The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation

The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation Hengfu Yang, Guoming Zhao, Xing Fan, Chunxiao Qiao, Bingfei Li, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8814026/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract ZrOCl 2 ·8H 2 O, (NH 4 ) 6 H 2 W 12 O 40 ·XH 2 O and aqueous ammonia were used as raw materials to prepare solid oxide supports with varying tungsten contents (ZrO 2 -WO 3 ) via the co-precipitation method. A series of solid acid catalysts were subsequently prepared by impregnating these supports with sulfuric acid solutions of different concentrations. The effects of crystal structure regulation on the acid properties of these catalysts on tunning the reaction performance of 2,6-di-tert-butyl-4-methylphenol (BHT) dealkylation to produce p -cresol were first investigated. The primary role of tungsten oxide may be to stabilize the monoclinic phase of ZrO 2 and to facilitate the formation of more and stronger Brønsted acid sites. The sample with a WO 3 mass fraction of 14% prepared using a 0.1 mol/L sulfuric acid solution (0.1-H 2 SO 4 /ZrO 2 -WO 3 -14) exhibits the highest specific surface area (57.27 m 2 ·g − 1 ), a suitable pore size structure (average pore size of 13.69 nm), the highest content of strong Brønsted acid. As a result, it achieves the highest conversion of BHT (greater than 99.9%) and selectivity for p -cresol (95.0%) under mild reaction condition at 180°C, significantly lower than the catalytic reaction temperatures of zeolites such as H-ZSM-5 (250–350°C). This is attributed to its stronger Brønsted acidity compared to H-ZSM-5, decreasing the energy barrier of dealkylation to enable high catalytic performance at lower temperature, which needs higher temperature on weaker acid, according to the Arrhenius equation ( \(\:\text{k}=\text{A}{e}^{\frac{{-E}_{a}}{RT}}\) ). Furthermore, after five cycles of reaction, the catalytic performance of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 decreased somewhat, but it was essentially restored after re-calcination. These studies will contribute to the understanding and guidance of the design of strong solid acid for low-temperature catalytic reactions and the further in-depth exploration of the laws of solid acid-catalyzed reactions under mild conditions. Strong solid acid H2SO4 Dealkylation Cresol WO3 ZrO2 Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Mixed cresols generally refer to the mixture of p -cresol, m -cresol, and o -cresol [ 1 ]. The three isomers have similar physical properties and appear as colorless, transparent liquids with a distinctive odor. They are prone to oxidation by dioxygen in the air, which can turn them into a pink liquid [ 2 ]. One of the primary sources of mixed cresols is the extraction from petroleum, oil shale, or coal tar [ 3 – 6 ]. The three cresol products obtained after the separation of mixed cresols are all important chemical intermediates and raw materials. For instance, p -cresol is a raw material for the production of plasticizers and phenolic resins. In the process of separating mixed cresols, ordinary distillation can be used to separate o -cresol from the mixture. However, due to the small difference in boiling points between p -cresol and m -cresol, which is only about 0.4 ºC, this boiling point difference is less than the separation capacity of conventional trays, and ordinary distillation operations are not sufficient for purification [ 4 ]. Currently, the methods for separating the mixture of m -cresol and p -cresol mainly include high-pressure crystallization [ 7 ], zeolite adsorption [ 8 ], crystallization [ 9 ], extraction [ 10 ], membrane separation [ 11 ] and alkylation method [ 12 ]. Among these, alkylation separation is the mainstream industrial technology for separating the mixed cresols of p -cresol and m -cresol. Scheme 1 illustrates the general steps of the alkylation separation method, which consists of two main reaction parts: the alkylation of mixed cresols and the dealkylation process. Under the action of an acid catalyst, the mixture of m -cresol and p -cresol undergoes the Friedel-Crafts reaction to form 2,6-di-tert-butyl-4-methylphenol (BHT) and 4,6-di-tert-butyl- m -cresol (DBMC). Since the boiling points of BHT and DBMC differ by 18.9 ºC, they can be separated by distillation. Subsequently, BHT and DBMC undergo catalytic dealkylations to obtain p -cresol and m -cresol products, respectively. Sulfuric acid has been proven to be the most widely used homogeneous acid in the alkylation separation process. However, the dealkylation of BHT requires a high temperature (> 180 ºC). When sulfuric acid is used for the dealkylation of BHT, the excessively high temperature can generate sulfuric acid vapor, which corrodes the reaction vessel. Moreover, the large amount of sulfuric acid waste liquid can also cause environmental damage. Under the current trend of increasing emphasis on environmental protection, the advantages of heterogeneous catalysts make them an ideal choice for achieving sustainable development in industrial production. There have been some reports on solid acid-catalyzed dealkylations. Verboekend et al. [ 13 ] prepared a hydrogen-form acidic catalyst by calcining NH 4 -ZSM-5 zeolite in static air and selected ethyl phenol, propyl phenol, or their mixtures with water as reactants, successfully generating phenol and olefins at 305°C and WHSV = 3.7 h -1 , with conversion as high as 80% and phenol selectivity exceeding 95%. H-ZSM-5 zeolite is an effective catalyst for dealkylation, but due to diffusion limitation, the products and large molecular by-products formed cannot be promptly diffused out of the pores, which intensify carbon deposition in the pores, leading to the decrease of acidic sites and consequently affecting catalytic activity and stability. Similar work has also been reported recently, such as the dealkylation of bio-based long-chain alkylphenol catalyzed by H-ZSM-5 [ 14 ], where the residence time within H-ZSM-5 was reduced under the condition of 250°C and the presence of water vapor to mitigate the poisoning of active sites [ 15 ]. Chen et al. [ 16 ] reduced the graphitization degree of coke deposition by introducing mesopores through H-ZSM-5 desilication, but the problem of coke deposition in micropores still exists. Li et al. [ 17 ] introduced mesopores by treating H-ZSM-5 with a weak base, which enhanced the catalytic stability. However, this also led to the increased complexity of catalytic products and the problem of coke deposition in micropores. Chen et al. [ 18 ] reduced the total amount of coke and mitigated catalyst deactivation by treating H-ZSM-5 with ammonium hexafluorosilicate to decrease internal silanol groups (silicon-related framework defects) and Lewis acid sites (aluminum-related framework defects). In summary, zeolite (such as H-ZSM-5) is the most extensively studied catalyst for alkylphenol dealkylation to date, primarily through the formation of mesopores and reduction of Lewis acid sites to delay catalyst deactivation, without fundamentally solving the problem of catalyst deactivation. Moreover, the reaction temperatures for zeolite-catalyzed processes are all too high (250–350°C), resulting in a greater number of by-products and higher energy consumption. In addition, the study of reaction mechanisms contributes to the design of acid catalysts for dealkylations. Firstly, the alkyl structure of alkylphenols can also affect catalytic performance. For the H-ZSM-5-catalyzed alkylphenol dealkylation to produce phenol and olefins, the study of a combination of static and dynamic density functional theory simulations shows that 4-isopropyphenol is first protonated by the Brønsted acid site of zeolite, forming a positively charged transition state[ 19 ]. Then the secondary nature of the central carbon atom of the isopropyl tail stabilizes the carbocation intermediates, resulting in its higher reactivity than that of 4- n -propylphenol. Secondly, the acid type of catalyst can also affect its performance. Wang et al. [ 19 ]employed solid catalysts of different acid types to convert DBMC to m -cresol and elucidated the dealkylation mechanism. For the γ-Al 2 O 3 catalyst mainly composed of Lewis acid, the reaction follows a single pathway of Lewis acid site adsorption, tert-butyl cation generation, and isobutene elimination. For active clay catalysts rich in both Lewis acid and Brønsted acid sites, the reaction may involve the synergistic catalysis of Lewis acid and Brønsted acid, allowing the removal of two tert-butyl groups to occur at different active sites. Thirdly, the water in the pores of zeolite shows a significant impact on the dealkylation. Through the research of the transition from zeolite Brønsted acid sites to hydronium ions in zeolites with different pore sizes by ab initio molecular dynamics combined with an enhanced sampling method based on Well-Tempered Metadynamics and a newly developed set of collective variables, it was found that the acidic protons tend to be shared between water and zeolites under low water loading conditions (1–2 water per Brønsted acid site), whereas higher water loadings (n > 2) lead to proton solvation within a localized water cluster adjacent to the Brønsted acid site [ 20 ]. The standard free energy of the formed complex is primarily determined by enthalpy and is related to the acid strength of Brønsted acid site and the surrounding space of this site at low water contents. However, the entropy increases linearly with the increase of water concentration in the pores, favors proton solvation and is independent of the pore shape/size. And enthalpy contributes only very little to the stabilization of the proton from water loadings higher than 3. Water is mainly located in the vicinity of the Brønsted acid site and does not diffuse in the pore of zeolite, which is a further indication that the confinement effects play a minor role in determining the acidity. The empty space between hydrated hydronium ions is easily occupied by molecules with higher dispersion stabilization than that of water molecules. In this environment, the adsorption of less polar molecules generates excessive chemical potential for these molecules, thereby destabilizing the adsorption and ultimately enhancing their reactivity compared to adsorption in the absence of such hydrated hydronium ions [ 21 ]. From the above analysis, it can be seen that different water contents around protons can lead to different proton transfer energy barriers (i.e. activation energies), which in turn correspond to different acid strengths of catalytic sites. Therefore, the acid strength of the catalyst can regulate the reaction rate by affecting the proton transfer energy barrier. On the other hand, according to the Arrhenius formula ( \(\:\text{k=A}{\text{e}}^{\frac{{\text{-}\text{E}}_{\text{a}}}{\text{RT}}}\) ), the reaction rate is influenced by three variables: the pre-exponential factor (A) determined by entropy, the activation energy (E a ), and the reaction temperature (T). When the pre-exponential factor of collision probability is assumed to remain constant, the lower the activation energy, the lower the required reaction temperature. For reactions catalyzed by both Lewis acid and Brønsted acid, among the three property parameters of acid type, number of acid sites, and acid strength, the acid strength should be the most reflective of the intrinsic catalytic performance of the active center. Therefore, we assume that the stronger the acid strength of the designed solid acid catalyst, the theoretically smaller the energy barrier of its activated reactants, and the lower the temperature required to achieve the same reaction rate. According to this qualitative theoretical hypothesis, is it possible to design stronger solid acids to achieve catalytic dealkylations at lower temperatures? SO 4 2- /M x O γ stands out among solid acids for their high acid strength and excellent stability, and have been widely employed in various catalytic reactions over the past two decades. Hara first reported the halogen-free SO 4 2- /M x O γ acid system, discovering that certain metal oxides impregnated with dilute sulfuric acid or sulfates and calcined at high temperatures could form solid acids with acid strength exceeding that of 100% H 2 SO 4 [ 22 ]. This finding attracted widespread attention. The temperature-programmed desorption results of cumene and benzene for the cumene dealkylation on WO 3 /ZrO 2 , H-ZSM-5, H-ZSM-11 zeolites, combined with the Hammett acidity data of SO 4 2- /ZrO 2 , WO 3 /ZrO 2 , H-ZSM-5, H-MCM-22, H-mordenite, H-ZSM-11, H-erionite zeolites, showed that within the Hammett acidity range of -5.6 < H 0 < -16.0, the temperature (T m ) corresponding to the maximum generation rate of dealkylation product benzene was linearly positively correlated with the Hammett acidity of the catalyst (H 0 = 32.50-18.37 \(\:\times\:\) 10 3 /T m ) [ 23 ]. The acid strength of the Brønsted acid sites in heterogeneous catalysts is also linearly positively correlated with the reaction rate constant of cumene dealkylation. According to the Arrhenius equation, the above relationship is that the acid strength of the Brønsted acid sites in heterogeneous catalysts is linearly negatively correlated with the activation energy of cumene dealkylation. However, the above study only used cumene as the model substrate and did not use phenols (cresol, tert-butyl cresol). There is also no involvement in the structure-activity relationship of tungsten trioxide modified sulfated zirconia sulfated zirconia and phenolic dealkylation. Subsequent research has shown that appropriate calcination temperature is the key factor to forming such solid acids [ 21 ]. SO 4 2- /ZrO 2 is a type of solid acid that possesses both Brønsted and Lewis acid sites and is the most extensively studied [ 24 ]. However, it has relatively low thermal stability, and the loss of SO 4 2- during the reaction can affect its catalytic stability. To address these issues of the SO 4 2- /ZrO 2 , the common solution is to modify it by introducing other metals, such as SO 4 2- /Al 2 O 3 -ZrO 2 , La/Ni-promoted SO 4 2− /ZrO 2 -Al 2 O 3 [ 25 ]. Sulfated zirconia (H 2 SO 4 /ZrO 2 ) and tungsten trioxide modified sulfated zirconia (H 2 SO 4 /ZrO 2 -WO 3 ), obtained by calcination at 700°C, both are highly active catalysts for the cracking and isomerization of hexane at 140°C [ 26 ]. Compared with H 2 SO 4 /ZrO 2 , H 2 SO 4 /ZrO 2 -WO 3 is more active. However, the conversion of hexane over HY, which does not possess stronger acid properties than H 2 SO 4 /ZrO 2 -WO 3 , only occurs above 400°C [ 27 ]. Research has shown that both WO 3 and SO₄²⁻ ions can prevent the agglomeration of ZrO 2 particles, thereby increasing the specific surface area of the catalyst. The optimal loading amount of WO 3 is equal to its dispersion threshold on ZrO 2 . The dispersed WO 3 also stabilizes the SO 4 2- ions that are coadsorbed on ZrO 2 [ 26 ]. In practical applications, they have demonstrated strong stability, non-corrosiveness to equipment, good recyclability, easy separation from products, and minimal environmental pollution, thus attracting significant attention [ 28 , 29 ]. However, reports on the application of H 2 SO 4 /ZrO 2 -WO 3 to alkylphenol dealkylation remain scarce. In this study, selected H 2 SO 4 /ZrO 2 -WO 3 solid acid as a catalyst for the dealkylation of BHT. H 2 SO 4 /ZrO 2 -WO 3 solid acid, with a higher proportion of strong Brønsted acid active sites, can catalyze the dealkylation of BHT under mild condition at 180°C, significantly lower than the catalytic reaction temperatures of zeolites such as H-ZSM-5 (250–350°C). The incorporation of an appropriate amount of WO 3 can prevent the reduction of the monoclinic phase of zirconia, which supports the alkylation active centers. The effects of reaction temperature, reaction time, and sulfuric acid impregnation solution concentration on conversion and selectivity were investigated, and the recyclability of H 2 SO 4 /ZrO 2 -WO 3 solid acid was also examined. In addition, the catalytic performance and property characterization of the above materials with different acid strengths indicate that according to the Arrhenius equation ( \(\:\text{k}=\text{A}{e}^{\frac{{-E}_{a}}{RT}}\) ), the stronger Brønsted acidity results in the lower energy barrier, which needs the lower temperature to achieve the same reaction rate as weaker acid at higher temperature. Finally, the catalytic mechanism for the dealkylation of BHT by strong solid acid were proposed. These findings contribute to the understanding and guidance of the design of strong solid acid catalysts for low-temperature reactions and the further in-depth study of the laws of solid acid-catalyzed reaction under mild condition. 2. Experiments 2.1 Materials BHT, DBMC, WO 3 , ZrOCl 2 ·8H 2 O, (NH 4 ) 6 H 2 W 12 O 40 ·XH 2 O, 2 - tert - butyl - 4 - methylphenol(2 - TBC), H - ZSM - 5, p - cresol was supplied by Shanghai McLean Biochemical Technology Co. Sulfuric acid, 6-tert-butyl- m -cresol (6-BMC), m - cresol, n - octane, cyclohexane, ethanol was purchased from Chengdu Cologne Chemical Co., Ltd. Ammonia was purchased from Shanghai Aladdin Biochemical Science and Technology Co., Ltd. Other reagents were analytically pure and did not require further purification. 2.2 Catalyst preparation 2.2.1 Preparation of x - H 2 SO 4 /ZrO 2 ZrOCl 2 ·8H 2 O was dissolved in deionized water. Under continuous magnetic stirring, aqueous ammonia (NH 3 ·H 2 O) was slowly added dropwise until the pH reached approximately 9, resulting in the formation of a white precipitate. After filtration, the filter cake was repeatedly washed with deionized water until the complete removal of Cl⁻ was achieved. The resulting precipitate was dried at 105°C for 12 hours and then ground to a 100 mesh size. The fine powder was impregnated with H 2 SO 4 solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120°C for 4 hours. These sample was designated as x-H 2 SO 4 /ZrO 2 -N, where x denotes the concentration of sulfuric acid used for impregnation of the support, with the unit of x mol/L. where N indicates that the sample was not calcined. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800°C for 4 hours. The corresponding solid acid was prepared and named x-H 2 SO 4 /ZrO 2 . 2.2.2 Preparation of x-H 2 SO 4 /WO 3 WO 3 was impregnated with H 2 SO 4 solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120°C for 4 hours. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800°C for 4 hours. The corresponding solid acid was prepared and named x-H 2 SO 4 /WO 3 (where x denotes the concentration of sulfuric acid used for impregnation of the support, x mol/L). 2.2.3 Preparation of x - H 2 SO 4 /ZrO 2 - WO 3 - ω The preparation steps of the x-H 2 SO 4 /ZrO 2 -WO 3 -ω catalyst is shown in Figure S1 . First, a certain amount of ZrOCl 2 ·8H 2 O and(NH 4 ) 6 H 2 W 7 O 40 ·XH 2 O was dissolved in deionized water. Under continuous stirring, ammonia solution was slowly added until the pH reached approximately 9, resulting in the formation of a white precipitate. The precipitate was washed to remove chloride ions. The resulting precipitate was dried at 105°C for 12 hours and then ground to a 100-mesh size. The fine powder was impregnated with H 2 SO 4 solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120°C for 4 hours. The sample was designated as x-H 2 SO 4 /ZrO 2 -WO 3 -N, where x denotes the concentration of sulfuric acid used for impregnation of the support, x mol/L, and N indicates that the samples were not calcined. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800°C for 4 hours. The corresponding solid acid was prepared and named x-H 2 SO 4 /ZrO 2 -WO 3 -ω, where ω represents the mass fraction of WO 3 . The values of ω were 12%, 14%, 16%, 18%, and 20%, respectively. The material obtained after re-calcination at 800°C for 4 hours following five cycles of catalytic reaction is denoted as 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-RC. 2.3 Catalyst characterization method The functional groups in the samples were tested using a Thermo Fisher Nicolet iS50 Fourier-transform infrared spectrometer (FT-IR). The phase of the prepared sample was analyzed using an X-ray diffractometer (Rigaku Ultima IV). The test samples were dried overnight in an oven at 100°C and then ground in an agate mortar. The ground samples were pressed into a glass sample holder for XRD analysis. Cu-Kα radiation (λ = 0.1542 nm) was used, with a current of 40 mA and a voltage of 40 kV. The scanning range was 5–90°, with a scanning speed of 8°/min and a step size of 0.02. The morphology and elemental distribution of the prepared samples were analyzed using a scanning electron microscope (FEI APREO). A small amount of test sample was attached to a conductive silicone. An accelerating voltage of 2 kV was used. The elemental distribution of the test material was qualitatively analyzed using the point and area scanning modes of an energy-dispersive X-ray spectrometer. The sample preparation method was the same as that for SEM, with an accelerating voltage of 10 kV. The thermal stability, thermal decomposition, and the correlation between products and mass loss of the samples were determined using a Mettler TGA 2 thermogravimetric analyzer under a nitrogen atmosphere with a heating rate of 10°C/min. The specific surface area and pore size distribution of the prepared samples were analyzed using a physical adsorption instrument (ASAP 2460, Micromeritics, USA). Approximately 0.2 g of the test sample was dried overnight in an oven at 100°C, then degassed under vacuum at 200°C for 12 h, and subsequently the N₂ adsorption-desorption isotherms of the sample was recorded at -196°C. The surface acidity of the sample was analyzed using a Fourier-transform infrared spectrometer (produced by Thermo Nicolet, USA) with pyridine adsorption infrared method. The samples were dried in an oven at 300°C for 3 h, adsorbed with pyridine under vacuum at room temperature, evacuated for 1 h, and maintained under vacuum for 20 h. After adsorption, the samples were dried in a vacuum oven at 150°C for 5 h to remove physically adsorbed pyridine. The samples were then placed in the infrared spectrometer, and diffuse reflectance infrared spectra were recorded in the range of 650–4000 cm -1 . The acid amount and acid strength of the samples were analyzed using a CHEMBET-3000 TPD/TPR analyzer (produced by Quantachrome, USA). The method involved heating the samples to 500°C under a helium atmosphere and holding for 30 min, cooling to 70°C, adsorbing ammonia for 30 min, purging with helium for 1 h, and then recording the NH 3 -TPD curve while ramping to the set temperature. The products of catalytic reaction were analyzed using a SP-6800A gas chromatograph. The specific instrument parameter settings and chromatographic column information are shown in Table S1 . 2.4 Catalytic reaction The catalytic activity for BHT dealkylation was evaluated in a three-necked flask equipped with a reflux condenser. Typically, before each catalytic reaction test, 0.2 g of catalyst was thoroughly mixed with 10 g of BHT, and the reaction was carried out at 150–200°C under a nitrogen atmosphere as a protective gas. The stirring rate was 10 r/s, and the nitrogen flow rate was 100 mL/min. After the reaction, the product composition was analyzed using a gas chromatograph with nitrogen as the carrier gas, and the composition of the reaction mixture was determined using the internal standard method. 2.5 Calculation of conversion, selectivity and yield The calculation of conversion, selectivity and yield is provided in the Supporting Information. 3. Results and discussion 3.1 Characterization Figure 1 presents the XRD patterns of the samples. Compared with the 0.1-H 2 SO 4 /ZrO 2 sample, the 0.1- H 2 SO 4 /ZrO 2 -WO 3 -14 sample, which contains added tungsten, shows not only the characteristic peaks of the tetragonal phase of zirconia (t-ZrO 2 ) at around 29.9°, 34.1°, 50.0°, and 60.1° but also significantly enhanced peaks of the monoclinic phase of zirconia (m-ZrO 2 ) at around 28.1°, 31.5°, and 35.3° [ 30 , 31 ]. Additionally, new peaks at around 23.1°, 23.6°, and 24.4°, which are characteristic of the WO 3 phase, are observed. This is consistent with the literature reports that the addition of WO 3 alters the proportion of the two zirconia phases, and different tungsten contents affect the proportion of the two zirconia phases [ 32 ]. Therefore, the effect of WO 3 content on the crystalline structure of 0.1-H 2 SO 4 /ZrO 2 -WO 3 was investigated (Fig. 1 b). As the WO 3 content increases from 12 wt.% to 20 wt.%, the peak height of the characteristic diffraction peak of WO 3 gradually increases. When the WO 3 mass content reaches 14%, the sample begins to show distinct diffraction peaks of monoclinic ZrO 2 . Then, with the further increase of WO 3 mass content to over 16%, the diffraction peaks of monoclinic ZrO 2 in the sample disappear. Therefore, 14 wt.% of WO 3 aids in the formation and stabilization of monoclinic ZrO 2 in 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14, preventing its transformation to tetragonal ZrO 2 and enhancing the acidity of the material [ 33 ]. The structure of each sample was also confirmed by infrared spectroscopy, as shown in Figure S2. The absorption peak at 499 cm -1 corresponds to the vibration of the zirconium-oxygen bond [ 34 , 35 ], the peak at 1630 cm -1 is characteristic of adsorbed water, and the peak at 3446 cm -1 is due to the stretching vibration of hydroxyl groups. Compared with the support that was not impregnated with sulfuric acid solution, the reason for the smaller particle size of the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample may be due to the corrosive nature of the impregnation solution used (Fig. 2 ). And the uncalcined 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-N sample has larger particles than the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample (Fig. 2 e), which may be attributed to the decomposition of zirconium hydroxide during the calcination process. As shown in Fig. 2 f, the particles of the catalyst become smaller after calcination following the five catalytic cycles, which is attributed to the continuous mechanical stirring during the reaction causing the catalyst particles to break. As can be seen from the energy-dispersive X-ray (EDX) spectrum of the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample (Fig. 2 g), the elements Zr, W, O, and S are uniformly distributed in the sample. Figure 3 presents the TG and DTG curves of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-N. The weight loss in the curve from 50°C to 200°C is mainly attributed to the volatilization of adsorbed water in the sample. The second stage, from 200°C to 650°C, shows that the TG curve continues to decline, albeit at a significantly reduced rate. The weight loss in this stage is primarily due to the volatilization of chemically bound water [ 36 ]. And the mass loss of 4.8% between 650 and 800°C is attributed to the decomposition of zirconium hydroxide in 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-N. As the pyrolysis temperature increases further, the DTG curve gradually levels off, indicating that the zirconium hydroxide in the sample is almost completely decomposed around 800°C. The specific surface area and pore size distribution of different solid acids have a significant impact on the dealkylation of BHT. Therefore, N 2 adsorption-desorption characterization was used to analyze the specific surface area and average pore size of samples with different sulfuric acid impregnation concentrations, as well as those after five catalytic cycles and re-calcination (Fig. 4 ). As shown in Fig. 4 a, the N 2 adsorption-desorption isotherms of all samples exhibit distinct type IV isotherm characteristics and H4 hysteresis loops [ 37 , 38 ]. The hysteresis loops in the high-pressure region indicate the presence of mesoporous structures in the samples. The pore size distribution diagrams obtained from the adsorption curves (Fig. 4 b) also confirm the existence of mesoporous structures. The N 2 adsorption-desorption isotherms of samples prepared with different tungsten contents and different sulfuric acid impregnation concentrations show significant differences. Compared with the 0.1-H 2 SO 4 /ZrO 2 sample, the addition of WO 3 in the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample significantly increases the pore size of the mesopores (Table 1 ). With the increase of sulfuric acid impregnation concentration, the specific surface area of the samples first increases and then decreases, with the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample having the largest specific surface area. The impregnation load with sulfuric acid did not significantly reduce the specific surface area and average pore size of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample, compared with the ZrO 2 -WO 3 -14 sample. In addition, the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-RC sample has a specific surface area, pore volume, and average pore size comparable to those of the freshly prepared sample. Table 1 Specific surface area, pore volume and average pore size of solid acid catalysts. Catalyst S BET a / m 2 ·g -1 V P b / cm 3 ·g -1 d P c / nm 0.1-H 2 SO 4 /ZrO 2 108.00 0.26 9.74 ZrO 2 -WO 3 -14 53.09 0.20 14.08 0.01-H 2 SO 4 /ZrO 2 -WO 3 -14 47.31 0.20 16.60 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 57.27 0.20 13.69 2-H 2 SO 4 /ZrO 2 -WO 3 -14 15.19 0.07 23.27 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14- RC 43.51 0.18 17.14 a: BET surface area; b: total pore volume; c: average pore diameter. The distribution of Brønsted (B) and Lewis (L) acid sites on the surfaces of 0.1- H 2 SO 4 /ZrO 2 , 0.1-H 2 SO 4 /WO 3 and 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 samples was determined using pyridine adsorption infrared spectroscopy (Fig. 5 ). Pyridine molecules adsorbed on B acid sites are protonated, resulting in a characteristic infrared peak at 1540 cm -1 . Pyridine molecules adsorbed on L acid sites form coordinate bonds with the L acid centers due to the donation of electron pairs from the nitrogen atoms, leading to a characteristic infrared peak at 1445 cm -1 . As shown in Fig. 5 , the addition of WO 3 significantly affects the distribution of B and L acid sites on the catalysts [ 39 ]. Taking the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 catalyst as a reference standard and setting its relative total acid amount to 100, the relative amounts of B acid, L acid and total acid, as well as the ratio of B acid to L acid for other catalysts, were calculated. The specific results are shown in Table 2 . The appropriate addition of WO 3 can effectively increase the total acid amount and B acid content on the surface of the solid acid, while reducing the L acid content on the catalyst surface. Table 2 The relative amount of different types of acid sites. Catalyst Relative acid amount Lewis acid amount Brønsted acid amount B/L a 0.1-H 2 SO 4 /ZrO 2 20.55 8.74 8.85 1.01 0.1-H 2 SO 4 /WO 3 26.48 12.64 1.25 0.10 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 100.00 27.42 39.48 1.44 a: The contents of Brønsted and Lewis acid sites were determined by Py-IR: the integrated area of the band at 1540 cm -1 was taken as the Brønsted acid amount, and that at 1450 cm -1 as the Lewis acid amount; the total acid amount of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 was set to 100, and the corresponding peak areas of the other samples were scaled proportionally to obtain the relative acid amounts. In SO 4 2- /M x O γ solid acids, the oxygen end of the SO 4 2- group exhibits significant electron-withdrawing properties, causing the electron cloud in the Zr-O-S bond to shift towards the S = O bond, thereby enhancing the L acidity of the catalyst. However, when tungsten, which has a higher electronegativity than zirconium, is added to SO 4 2- / ZrO 2 , W forms Zr-O-W bonds with Zr atoms, competing with S atoms for electrons, weakening the polarity of the Zr-O-S bond, and ultimately reducing the number and strength of L acid centers. Nevertheless, the addition of WO 3 can to some extent increase the B acid amount of the catalyst. On the one hand, the presence of a small amount of water molecules or hydroxyl groups can convert L acid sites to B acid sites. On the other hand, some reduced WO X species in the system can form B acid sites by stabilizing hydrogen protons, and Zr atoms encapsulated by WO X octahedra can combine with OH groups to generate B acid sites with higher strength [ 40 ]. However, as the content of WO 3 continues to increase, WO X octahedra gradually aggregate to form three-dimensional WO 3 crystalline particles, disrupting the B acid sites formed by WO X species, thereby reducing the overall acid strength and the number of acid centers. Figure 6 shows the NH 3 -TPD spectra of 0.1-H 2 SO 4 /ZrO 2 , 0.1-H 2 SO 4 /WO 3 and 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14. The prepared solid acid samples exhibit four distinct peaks, corresponding to weak acid sites ( 450°C) [ 30 ]. Compared with the 0.1-H 2 SO 4 /ZrO 2 and 0.1-H 2 SO 4 /ZrO 2 samples, 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 has a more pronounced strong acid peak, especially in the range of 550–700°C where the NH 3 desorption peak at 640°C corresponds to a more pronounced strong acid peak. However, H-ZSM-5 only exhibited a desorption peak of NH 3 with a peak tip at 510°C [ 41 ]. The above results indicate that 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 has stronger acid sites than H-ZSM-5. Taking 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 as the standard, with its relative total acid amount set at 100, the relative contents of weak acid, medium-strong acid, strong acid and total acid amount for 0.1-H 2 SO 4 /ZrO 2 , 0.1-H 2 SO 4 /WO 3 and 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 were calculated, as shown in Table 3 . The addition of an appropriate amount of WO 3 significantly increases the total acid amount, especially the content of strong acid sites, of the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample compared to solid acids prepared from single metal oxides. Table 3 The relative amount of acid sites of different intnesities. Catalysts Relative weak acid amount Relative medium acid amount Relative strong acid amount Relative total acid amount 0.1-H 2 SO 4 /WO 3 1.12 0.97 16.04 18.13 0.1-H 2 SO 4 /ZrO 2 12.69 24.27 25.52 62.48 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 17.71 26.50 55.79 100.00 3.2 Catalytic performance As can be seen from Fig. 7 , when the ZrO 2 -WO 3 -14 sample that was not impregnated with sulfuric acid solution was used to catalyze the dealkylation of BHT, the conversion is only 85.1%, and the selectivity of p -cresol is only 74.6%. When ZrO 2 -WO 3 -14 was impregnated with sulfuric acid solutions of different concentrations, the conversion of BHT remains above 99.9% with increasing impregnation solution concentration, while the selectivity of p -cresol first increases and then decreases. 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 shows the best catalytic performance. Similarly, Zhang et al. [ 42 ] modified ZrO 2 with sulfuric acid to catalyze the isomerization and arylation of oleic acid and found that the activity of the sulfuric acid-modified zirconia was three times that of the catalyst without sulfuric acid impregnation. Since the highest conversion of BHT dealkylation and selectivity of p -cresol is achieved when the concentration of the impregnation solution is 0.1 mol/L, a sulfuric acid concentration of 0.1 mol/L was used in subsequent experiments to explore the optimal reaction conditions. As shown in Table 4 , the catalytic activity and selectivity of the target product p -cresol of the 0.1-H 2 SO 4 /ZrO 2 -WO 3 catalyst system are higher than those of 0.1-H 2 SO 4 /WO 3 and 0.1-H 2 SO 4 /ZrO 2 . The sample with 14 wt.% WO 3 exhibits the best catalytic performance. In combination with the catalyst characterization results, it can be seen that 0.1-H 2 SO 4 /ZrO 2 has the largest specific surface area (108.00 m 2 ·g -1 , see Table 1 ) and a higher number of relative strong Brønsted acid sites (Table 2 , Table 3 ), 0.1-H 2 SO 4 /WO 3 has fewer acid centers, especially a lower proportion of Brønsted acid centers than 0.1-H 2 SO 4 /ZrO 2 . 0.1-H 2 SO 4 /ZrO 2 exhibits higher catalytic activity and p -cresol selectivity than 0.1-H 2 SO 4 /WO 3 . It can be inferred that acid centers, especially strong Brønsted acid centers, are the more active dealkylation active centers. Similarly, in contrast to 0.1-H 2 SO 4 /WO 3 and 0.1-H 2 SO 4 /ZrO 2 , although 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 has a smaller specific surface area (57.27 m 2 ·g -1 , Table 1 ) than 0.1-H 2 SO 4 /ZrO 2 , it has the highest acid density and strong acid Brønsted acid content, showing the highest dealkylation activity and p -cresol selectivity. Therefore, 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 exhibits higher catalytic activity and selectivity towards p -cresol at lower reaction temperatures (180°C) than H-ZSM-5 at higher reaction temperatures (250–350°C), attributed to the stronger Brønsted acid sites and larger pore size of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 compared to H-ZSM-5 (see Table 4 and S3 for details). In summary, we can infer that the stronger the acidity of the Brønsted acid center, the more easily it can donate a proton to activate the alkylphenol to form an active alkyl carbocation at lower temperature, thereby facilitating the dealkylation at lower temperature. This provides a new idea for the further in-depth design of acid catalysts for the dealkylation of alkylphenols under mild conditions in industry. Table 4 The dealkylation performance of BHT using different solid acids. Catalysts a Conv./% Sel 2-TBC /% Sel p -cresol /% Sel Other /% b H-ZSM-5 16.7 15.6 80.2 4.2 0.1-H 2 SO 4 / WO 3 87.5 16.5 81.1 2.4 0.1-H 2 SO 4 / ZrO 2 90.5 12.8 85.2 2.0 0.1-H 2 SO 4 /ZrO 2 -WO 3 -12 99.9 8.4 89.9 1.7 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 99.9 4.0 95.0 1.0 0.1-H 2 SO 4 /ZrO 2 -WO 3 -16 99.9 8.7 90.2 1.1 0.1-H 2 SO 4 /ZrO 2 -WO 3 -18 99.9 8.4 89.9 1.7 0.1-H 2 SO 4 /ZrO 2 -WO 3 -20 99.9 8.8 90.3 0.9 a: For the dealkylation catalyzed by the solid acid, 10 g of BHT was charged with 0.2 g of catalyst, and the mixture was reacted at 180°C for 6 h.;b: the other isomerization by-products and other impurities. The effects of reaction time and temperature on the dealkylation of BHT catalyzed by 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 are shown in Fig. 8 a and 9 b, respectively. Both the conversion of BHT and the selectivity of p -cresol increase with increasing reaction time. After 3 h, the conversion of BHT gradually increases to 99.9%. And after 6 h, the selectivity of p -cresol reaches 95.0%. Figure 8 b shows the effect of reaction temperature on the dealkylation of BHT catalyzed by 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14. When the reaction temperature increases from 140°C to 160°C, the conversion of BHT rapidly increases to 99.9%, and the selectivity of p -cresol also gradually increases with increasing reaction temperature. When the reaction temperature rises from 160°C to 190°C, the conversion of BHT remains at 99.9%, and the selectivity of p -cresol continues to increase with increasing reaction temperature. After a catalytic reaction, the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample was filtered and separated, washed repeatedly with anhydrous ethanol, and then dried in an oven at 60°C for 12 h. The recovered solid acid was used for the next catalytic reaction under the same condition as the first reaction cycle. As shown in Fig. 9 a, the recyclability of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 without calcination after catalytic reaction was poor, with the conversion of BHT and the selectivity of p -cresol gradually decreasing. After re-calcination following five cycles of catalytic reactions, the catalytic activity was comparable to that of the fresh sample in its first reaction cycle. XRD characterization results (Fig. 9 b) show that, compared with the fresh catalyst, the characteristic peaks of the monoclinic phase of zirconia, which supports the active centers in the 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14-RC sample after five cycles and re-calcination, did not change significantly at around 29.8°, 34.1°, 50.0°, and 60.1°.The disappearance and shift of the characteristic peaks of the WO 3 sample indicate that the crystal form of W element in the sample after five cycles and calcination has changed, resulting in a more uniform distribution in ZrO 2 . In addition, the catalytic performance of 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 in the dealkylation of DBMC shows that, despite the different substitution position of the same substituent in DBMC and BHT, the spatial steric and electronic effects on catalytic performance are minimal (Table S2). 3.3 Reaction mechanism It is generally believed that the dealkylation of alkylphenols follows the acid-catalyzed carbocation mechanism and is the reverse reaction of the Friedel-Crafts alkylation. And the Friedel-Crafts alkylation reaction of cresol with isobutylene is an electrophilic substitution reaction on the aromatic ring of cresol, which is divided into two steps. First, the p -cresol molecule is adsorbed on the acid site of the catalyst surface. The B acid on the catalyst releases H⁺, which reacts with isobutylene to form a carbocation. Second, the carbocation attacks a carbon atom on the aromatic ring to generate 2-tert-butyl- p -cresol. Similarly, 2-tert-butyl- p -cresol repeats the same steps and subsequent processes as p -cresol. Based on the above characterization of the H 2 SO 4 /ZrO 3 –WO 3 catalyst and the analysis of its catalytic performance for BHT, it can be inferred that the reaction mechanism for the dealkylation of alkylphenols catalyzed by strong solid acid is as follows (Fig. 10 ). First, the BHT molecule is adsorbed on the acidic sites of the catalyst surface. The B acid center near the adsorbed reactants releases a proton. The released proton attacks the carbon atom of the tert-butyl group in the electron-rich BHT in an electrophilic manner, forming a carbocation with a positively charged carbon on the aromatic ring. Then, the electron on the activated tert-butyl C α is transferred to the adjacent aromatic carbon, forming tert-butyl- p -cresol. The activated tert-butyl group is replaced by a proton to form of a tert-butyl carbocation. At the same time, one electron from the C-H bond on the C β of the tert-butyl carbocation is transferred to C α . After a hydrogen atom on C β is released as a proton and returns to the sulfonic acid group on the catalyst that is lacking a proton, isobutylene is formed and the catalyst is restored to its original state, completing a catalytic reaction cycle. Through the same catalytic reaction process, 2 - TBC releases isobutylene to form p -cresol. Therefore, designing and synthesizing catalysts with relatively stronger acid centers can effectively catalyze the dealkylation and decrease the reaction temperature to some extent, which is of great significance to industrial production. 4. Conclusions ZrOCl 2 ·8H 2 O, (NH 4 ) 6 H 2 W 12 O 40 ·XH 2 O, and ammonia water were used as raw materials to synthesize the ZrO 2 -WO 3 supports. By adjusting the amount of (NH 4 ) 6 H 2 W 12 O 40 ·XH 2 O added, different supports were prepared. These supports were then impregnated with sulfuric acid solutions of different concentrations to prepare a series of solid acid catalysts. The 0.1-H 2 SO 4 /ZrO 2 -WO 3 -14 sample with 14 wt.% WO 3 and impregnated with 0.1 mol/L sulfuric acid aqueous solution shows the best catalytic performance for the new application of BHT dealkylation. This catalyst has a relatively higher specific surface area, a suitable mesoporous pore size distribution, a higher ratio of Brønsted acid to Lewis acid sites, and a greater amount of strong Brønsted acid sites, thus exhibiting the best performance in the BHT dealkylation. After catalyzing the BHT dealkylation at the mild condition of 180 ºC for 6 hours, the conversion of BHT was greater than 99.9%, and the selectivity for p -cresol reached 95.0%. After five cycles of reaction, the catalyst was re-calcined and its catalytic activity was restored for further cycle. It is found that the primary role of tungsten oxide may be to stabilize the monoclinic phase of ZrO 2 and to facilitate the formation of more strong Brønsted acid sites. Furthermore, it is found that designing and synthesizing catalysts with relatively stronger acid centers can effectively catalyze the dealkylation and decrease the reaction temperature to some extent. These findings contribute to the understanding and guidance of the design of strong solid acid catalysts and further in-depth studies on the laws of solid acid-catalyzed reaction under mild condition. Abbreviations 2,6-di-tert-butyl-4-methylphenol: BHT 4,6-di-tert-butyl- m -cresol: DBMC 2 - tert - butyl - 4 - methylphenol: 2 - TBC 6-tert-butyl- m -cresol: 6-BMC Fourier Transform Infrared Spectroscopy: FT-IR Thermogravimetric analysis: TG Derivative Thermogravimetry: DTG X-ray diffraction: XRD Scanning Electron Microscope: SEM: Brunauer–Emmett–Teller: EDX Brunauer–Emmett–Teller: BET Ammonia Temperature-Programmed Desorption: NH 3 -TPD Monoclinic phase of zirconia: m-ZrO 2 Tetragonal phase of zirconia: t-ZrO 2 Declarations Ethics and Consent to Participate This study does not involve human participants, human data, or animal experiments. Therefore, no ethical approval or informed consent to participate is required. Consent for Publication All authors have read and approved the final manuscript, and consent to its publication in Catalysis Letters . All authors confirm that the manuscript has not been published previously, is not under consideration for publication elsewhere, and its publication is approved by all authors and, if applicable, by the authorities where the work was carried out. Competing Interests The authors have no competing interests to declare that are relevant to the content of this article. Author Contribution All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Hengfu Yang, Guoming Zhao, Xing Fan, Chunxiao Qiao, Bingfei Li, Xiang Bai and Xianyong Wei. The first draft of the manuscript was written by Hengfu Yang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding This work was supported by the Natural Science Foundation of Yili Normal University (Grant 22XKZY18), the Key Research and Technology Development Projects of Yili Prefecture (YZD2024A18), the Major Science and Technology Projects of Xinjiang Uygur Autonomous Region (2024A01006), and the National Natural Science Foundation of China (Grant 21676293). Availability of data and materials The data that support the findings of this study are available on request. Acknowledgments The authors would like to express their sincere gratitude to Guoming Zhao/Xing Fan for their valuable guidance and suggestions during the research process. References Pan C, Guo J, Liu Y et al (2024) Efficient separation of cresol isomers using azeotropic coupling pressure-swing distillation: From separation mechanism to process integration. 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Supplementary Files SupportingInformation.doc scheme1.png Scheme 1 The process of separating mixed cresols of m -cresol and p -cresol by alkylation method. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8814026","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":592014538,"identity":"7b0bf123-915e-494f-a124-a39663628a8e","order_by":0,"name":"Hengfu Yang","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Hengfu","middleName":"","lastName":"Yang","suffix":""},{"id":592014541,"identity":"7092d31d-e30e-492d-a28c-c4fc1712d1af","order_by":1,"name":"Guoming Zhao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYDACCQgpZ3+8+cCBDxXEa7EwZjhzLPHgjDPEa6lIbLiRY3yYt4UIHfKzmx8+/Jojkdg4I+fDAd4GBnl+sQP4tTDOOWZsLLtNwriZ5+2GA5I7GAxnzk7Ar4VZIsFMWnKbhGwbe+6GA4ZnGBIMbhPQwiaR/g2khbGHIefBgcQ2IrTwSOSYSX7cJqE4gyOH4cBBYrRISOQUGzMC/WLAc8zgYMMZCcJ+kZ+RvvHhz211cgbszY8//6mwkeeXJqAFBJh5kGwlrBwEGH8Qp24UjIJRMApGKgAAdqJIakmREUsAAAAASUVORK5CYII=","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Guoming","middleName":"","lastName":"Zhao","suffix":""},{"id":592014543,"identity":"66e871a6-c10c-4554-9bdb-c2bfce7ac3b6","order_by":2,"name":"Xing Fan","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Xing","middleName":"","lastName":"Fan","suffix":""},{"id":592014547,"identity":"cd6733b1-7961-42f1-ae4b-9b75bf81bfc1","order_by":3,"name":"Chunxiao Qiao","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Chunxiao","middleName":"","lastName":"Qiao","suffix":""},{"id":592014549,"identity":"1869929b-3e31-4a56-976c-d146e4c8963a","order_by":4,"name":"Bingfei Li","email":"","orcid":"","institution":"Shandong University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Bingfei","middleName":"","lastName":"Li","suffix":""},{"id":592014554,"identity":"261ab2a0-9392-4a8b-811b-e12a2992e7a5","order_by":5,"name":"Xiang Bai","email":"","orcid":"","institution":"Yili Normal University","correspondingAuthor":false,"prefix":"","firstName":"Xiang","middleName":"","lastName":"Bai","suffix":""},{"id":592014558,"identity":"7779e3f4-3d08-4d0d-a5ce-023ab085da04","order_by":6,"name":"Xianyong Wei","email":"","orcid":"","institution":"Yili Normal University","correspondingAuthor":false,"prefix":"","firstName":"Xianyong","middleName":"","lastName":"Wei","suffix":""}],"badges":[],"createdAt":"2026-02-07 09:10:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8814026/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8814026/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102911689,"identity":"9030e28a-cc6f-4ac5-8cd9-029068194b0d","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":140681,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of (a) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 and (b) XRD patterns of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-ω.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/807cee61a174a712710d9fe2.png"},{"id":102911692,"identity":"943d0c17-efa1-4189-9404-9e0fb383fb15","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1527909,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the (a) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, (b) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e, (c) ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14, (d) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14, (e) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-N, (f) 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-RC and (g) SEM images and EDX elemental maps of the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/cb1d2718cad05c90842a6ecf.png"},{"id":102911690,"identity":"0b06ba49-9070-40cc-8bcb-45a189cd59ed","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":76684,"visible":true,"origin":"","legend":"\u003cp\u003eTG and DTG curves of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-N.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/dfb8ad9a221717babf4d01a2.png"},{"id":102911697,"identity":"ffcb4bce-18c0-4f03-ac1d-617dee25f312","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":193828,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Nitrogen adsorption–desorption isotherms of the catalysts, (b) pore size distribution.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/8e8044c2b03866316b82a8c2.png"},{"id":102964607,"identity":"d5d63140-1800-4a43-bcc6-0c015572db14","added_by":"auto","created_at":"2026-02-19 04:22:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":56928,"visible":true,"origin":"","legend":"\u003cp\u003ePyridine adsorption infrared spectra of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 solid acid catalysts.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/b8b600eecf24a988a947359b.png"},{"id":102964414,"identity":"c54ed5ce-b5e6-4ab6-a585-eb9f96cb20c9","added_by":"auto","created_at":"2026-02-19 04:22:14","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":57300,"visible":true,"origin":"","legend":"\u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e-TPD spectra of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 solid acid catalysts.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/67c685e83e65e78f7917f4e7.png"},{"id":102911693,"identity":"c6884453-3e32-428b-a97f-951a5226afc0","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":78944,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of sulfuric acid concentration on the dealkylation performance of x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 in catalyzing BHT.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/3084344f2945d1e3ed2b7232.png"},{"id":102963749,"identity":"73dd1253-565d-4483-81c5-268339f51493","added_by":"auto","created_at":"2026-02-19 04:20:25","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":131544,"visible":true,"origin":"","legend":"\u003cp\u003eThe catalytic performance of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 with different reaction conditions: (a) time; (b) temperature.\u003c/p\u003e\n\u003cp\u003eOther reaction conditions: (a) reaction temperature 180 ºC; (b) reaction time 6 h.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/b462607757fcd8c6e0639d81.png"},{"id":102911701,"identity":"473f4496-1e63-462f-8061-546bc09571f6","added_by":"auto","created_at":"2026-02-18 10:13:33","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":86548,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Evaluation of the catalytic stability of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14, (b) XRD patterns of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-RC and fresh catalyst.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/c381532afe5558755a18fa93.png"},{"id":102963581,"identity":"6f28ded5-34bd-4a0a-8dd3-d39452d98bfb","added_by":"auto","created_at":"2026-02-19 04:19:07","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":121212,"visible":true,"origin":"","legend":"\u003cp\u003eDealkylation mechanism.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/8d009bdfbbf0d6822fdfdc59.png"},{"id":105033666,"identity":"bbecf030-8839-4103-b44d-f80e727a1999","added_by":"auto","created_at":"2026-03-20 07:21:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3611701,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/abeb92b5-8b9c-43b4-8c9e-eff819d229e2.pdf"},{"id":102911698,"identity":"5f39c4ee-b7d3-455e-8f6b-f84da300f8be","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"doc","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2369536,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.doc","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/ddce650f0ef5f0ac7953d595.doc"},{"id":102911699,"identity":"75b5209f-18d1-47b9-9e58-850ee2f99f29","added_by":"auto","created_at":"2026-02-18 10:13:32","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":135086,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1\u003c/strong\u003e The process of separating mixed cresols of \u003cem\u003em\u003c/em\u003e-cresol and \u003cem\u003ep\u003c/em\u003e-cresol by alkylation method.\u003c/p\u003e","description":"","filename":"scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-8814026/v1/40320c11dde93ea42065cbac.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMixed cresols generally refer to the mixture of \u003cem\u003ep\u003c/em\u003e-cresol, \u003cem\u003em\u003c/em\u003e-cresol, and \u003cem\u003eo\u003c/em\u003e-cresol [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The three isomers have similar physical properties and appear as colorless, transparent liquids with a distinctive odor. They are prone to oxidation by dioxygen in the air, which can turn them into a pink liquid [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. One of the primary sources of mixed cresols is the extraction from petroleum, oil shale, or coal tar [\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The three cresol products obtained after the separation of mixed cresols are all important chemical intermediates and raw materials. For instance, \u003cem\u003ep\u003c/em\u003e-cresol is a raw material for the production of plasticizers and phenolic resins. In the process of separating mixed cresols, ordinary distillation can be used to separate \u003cem\u003eo\u003c/em\u003e-cresol from the mixture. However, due to the small difference in boiling points between \u003cem\u003ep\u003c/em\u003e-cresol and \u003cem\u003em\u003c/em\u003e-cresol, which is only about 0.4 \u0026ordm;C, this boiling point difference is less than the separation capacity of conventional trays, and ordinary distillation operations are not sufficient for purification [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Currently, the methods for separating the mixture of \u003cem\u003em\u003c/em\u003e-cresol and \u003cem\u003ep\u003c/em\u003e-cresol mainly include high-pressure crystallization [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], zeolite adsorption [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], crystallization [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], extraction [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], membrane separation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] and alkylation method [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Among these, alkylation separation is the mainstream industrial technology for separating the mixed cresols of \u003cem\u003ep\u003c/em\u003e-cresol and \u003cem\u003em\u003c/em\u003e-cresol. Scheme \u003cspan refid=\"Sch2\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the general steps of the alkylation separation method, which consists of two main reaction parts: the alkylation of mixed cresols and the dealkylation process. Under the action of an acid catalyst, the mixture of \u003cem\u003em\u003c/em\u003e-cresol and \u003cem\u003ep\u003c/em\u003e-cresol undergoes the Friedel-Crafts reaction to form 2,6-di-tert-butyl-4-methylphenol (BHT) and 4,6-di-tert-butyl-\u003cem\u003em\u003c/em\u003e-cresol (DBMC). Since the boiling points of BHT and DBMC differ by 18.9 \u0026ordm;C, they can be separated by distillation. Subsequently, BHT and DBMC undergo catalytic dealkylations to obtain \u003cem\u003ep\u003c/em\u003e-cresol and \u003cem\u003em\u003c/em\u003e-cresol products, respectively. Sulfuric acid has been proven to be the most widely used homogeneous acid in the alkylation separation process. However, the dealkylation of BHT requires a high temperature (\u0026gt;\u0026thinsp;180 \u0026ordm;C). When sulfuric acid is used for the dealkylation of BHT, the excessively high temperature can generate sulfuric acid vapor, which corrodes the reaction vessel. Moreover, the large amount of sulfuric acid waste liquid can also cause environmental damage.\u003c/p\u003e \u003cp\u003eUnder the current trend of increasing emphasis on environmental protection, the advantages of heterogeneous catalysts make them an ideal choice for achieving sustainable development in industrial production. There have been some reports on solid acid-catalyzed dealkylations. Verboekend et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] prepared a hydrogen-form acidic catalyst by calcining NH\u003csub\u003e4\u003c/sub\u003e-ZSM-5 zeolite in static air and selected ethyl phenol, propyl phenol, or their mixtures with water as reactants, successfully generating phenol and olefins at 305\u0026deg;C and WHSV\u0026thinsp;=\u0026thinsp;3.7 h\u003csup\u003e-1\u003c/sup\u003e, with conversion as high as 80% and phenol selectivity exceeding 95%. H-ZSM-5 zeolite is an effective catalyst for dealkylation, but due to diffusion limitation, the products and large molecular by-products formed cannot be promptly diffused out of the pores, which intensify carbon deposition in the pores, leading to the decrease of acidic sites and consequently affecting catalytic activity and stability. Similar work has also been reported recently, such as the dealkylation of bio-based long-chain alkylphenol catalyzed by H-ZSM-5 [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], where the residence time within H-ZSM-5 was reduced under the condition of 250\u0026deg;C and the presence of water vapor to mitigate the poisoning of active sites [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Chen et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] reduced the graphitization degree of coke deposition by introducing mesopores through H-ZSM-5 desilication, but the problem of coke deposition in micropores still exists. Li et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] introduced mesopores by treating H-ZSM-5 with a weak base, which enhanced the catalytic stability. However, this also led to the increased complexity of catalytic products and the problem of coke deposition in micropores. Chen et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] reduced the total amount of coke and mitigated catalyst deactivation by treating H-ZSM-5 with ammonium hexafluorosilicate to decrease internal silanol groups (silicon-related framework defects) and Lewis acid sites (aluminum-related framework defects). In summary, zeolite (such as H-ZSM-5) is the most extensively studied catalyst for alkylphenol dealkylation to date, primarily through the formation of mesopores and reduction of Lewis acid sites to delay catalyst deactivation, without fundamentally solving the problem of catalyst deactivation. Moreover, the reaction temperatures for zeolite-catalyzed processes are all too high (250\u0026ndash;350\u0026deg;C), resulting in a greater number of by-products and higher energy consumption.\u003c/p\u003e \u003cp\u003eIn addition, the study of reaction mechanisms contributes to the design of acid catalysts for dealkylations. Firstly, the alkyl structure of alkylphenols can also affect catalytic performance. For the H-ZSM-5-catalyzed alkylphenol dealkylation to produce phenol and olefins, the study of a combination of static and dynamic density functional theory simulations shows that 4-isopropyphenol is first protonated by the Br\u0026oslash;nsted acid site of zeolite, forming a positively charged transition state[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Then the secondary nature of the central carbon atom of the isopropyl tail stabilizes the carbocation intermediates, resulting in its higher reactivity than that of 4-\u003cem\u003en\u003c/em\u003e-propylphenol. Secondly, the acid type of catalyst can also affect its performance. Wang et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]employed solid catalysts of different acid types to convert DBMC to \u003cem\u003em\u003c/em\u003e-cresol and elucidated the dealkylation mechanism. For the γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst mainly composed of Lewis acid, the reaction follows a single pathway of Lewis acid site adsorption, tert-butyl cation generation, and isobutene elimination. For active clay catalysts rich in both Lewis acid and Br\u0026oslash;nsted acid sites, the reaction may involve the synergistic catalysis of Lewis acid and Br\u0026oslash;nsted acid, allowing the removal of two tert-butyl groups to occur at different active sites. Thirdly, the water in the pores of zeolite shows a significant impact on the dealkylation. Through the research of the transition from zeolite Br\u0026oslash;nsted acid sites to hydronium ions in zeolites with different pore sizes by ab initio molecular dynamics combined with an enhanced sampling method based on Well-Tempered Metadynamics and a newly developed set of collective variables, it was found that the acidic protons tend to be shared between water and zeolites under low water loading conditions (1\u0026ndash;2 water per Br\u0026oslash;nsted acid site), whereas higher water loadings (n\u0026thinsp;\u0026gt;\u0026thinsp;2) lead to proton solvation within a localized water cluster adjacent to the Br\u0026oslash;nsted acid site [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The standard free energy of the formed complex is primarily determined by enthalpy and is related to the acid strength of Br\u0026oslash;nsted acid site and the surrounding space of this site at low water contents. However, the entropy increases linearly with the increase of water concentration in the pores, favors proton solvation and is independent of the pore shape/size. And enthalpy contributes only very little to the stabilization of the proton from water loadings higher than 3. Water is mainly located in the vicinity of the Br\u0026oslash;nsted acid site and does not diffuse in the pore of zeolite, which is a further indication that the confinement effects play a minor role in determining the acidity. The empty space between hydrated hydronium ions is easily occupied by molecules with higher dispersion stabilization than that of water molecules. In this environment, the adsorption of less polar molecules generates excessive chemical potential for these molecules, thereby destabilizing the adsorption and ultimately enhancing their reactivity compared to adsorption in the absence of such hydrated hydronium ions [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. From the above analysis, it can be seen that different water contents around protons can lead to different proton transfer energy barriers (i.e. activation energies), which in turn correspond to different acid strengths of catalytic sites. Therefore, the acid strength of the catalyst can regulate the reaction rate by affecting the proton transfer energy barrier. On the other hand, according to the Arrhenius formula (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{k=A}{\\text{e}}^{\\frac{{\\text{-}\\text{E}}_{\\text{a}}}{\\text{RT}}}\\)\u003c/span\u003e\u003c/span\u003e), the reaction rate is influenced by three variables: the pre-exponential factor (A) determined by entropy, the activation energy (E\u003csub\u003ea\u003c/sub\u003e), and the reaction temperature (T). When the pre-exponential factor of collision probability is assumed to remain constant, the lower the activation energy, the lower the required reaction temperature. For reactions catalyzed by both Lewis acid and Br\u0026oslash;nsted acid, among the three property parameters of acid type, number of acid sites, and acid strength, the acid strength should be the most reflective of the intrinsic catalytic performance of the active center. Therefore, we assume that the stronger the acid strength of the designed solid acid catalyst, the theoretically smaller the energy barrier of its activated reactants, and the lower the temperature required to achieve the same reaction rate. According to this qualitative theoretical hypothesis, is it possible to design stronger solid acids to achieve catalytic dealkylations at lower temperatures?\u003c/p\u003e \u003cp\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/M\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003eγ\u003c/sub\u003e stands out among solid acids for their high acid strength and excellent stability, and have been widely employed in various catalytic reactions over the past two decades. Hara first reported the halogen-free SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/M\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003eγ\u003c/sub\u003e acid system, discovering that certain metal oxides impregnated with dilute sulfuric acid or sulfates and calcined at high temperatures could form solid acids with acid strength exceeding that of 100% H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. This finding attracted widespread attention. The temperature-programmed desorption results of cumene and benzene for the cumene dealkylation on WO\u003csub\u003e3\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, H-ZSM-5, H-ZSM-11 zeolites, combined with the Hammett acidity data of SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, WO\u003csub\u003e3\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, H-ZSM-5, H-MCM-22, H-mordenite, H-ZSM-11, H-erionite zeolites, showed that within the Hammett acidity range of -5.6\u0026thinsp;\u0026lt;\u0026thinsp;H\u003csub\u003e0\u003c/sub\u003e \u0026lt; -16.0, the temperature (T\u003csub\u003em\u003c/sub\u003e) corresponding to the maximum generation rate of dealkylation product benzene was linearly positively correlated with the Hammett acidity of the catalyst (H\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;32.50-18.37\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\times\\:\\)\u003c/span\u003e\u003c/span\u003e10\u003csup\u003e3\u003c/sup\u003e/T\u003csub\u003em\u003c/sub\u003e) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The acid strength of the Br\u0026oslash;nsted acid sites in heterogeneous catalysts is also linearly positively correlated with the reaction rate constant of cumene dealkylation. According to the Arrhenius equation, the above relationship is that the acid strength of the Br\u0026oslash;nsted acid sites in heterogeneous catalysts is linearly negatively correlated with the activation energy of cumene dealkylation. However, the above study only used cumene as the model substrate and did not use phenols (cresol, tert-butyl cresol). There is also no involvement in the structure-activity relationship of tungsten trioxide modified sulfated zirconia sulfated zirconia and phenolic dealkylation. Subsequent research has shown that appropriate calcination temperature is the key factor to forming such solid acids [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e is a type of solid acid that possesses both Br\u0026oslash;nsted and Lewis acid sites and is the most extensively studied [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, it has relatively low thermal stability, and the loss of SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e during the reaction can affect its catalytic stability. To address these issues of the SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, the common solution is to modify it by introducing other metals, such as SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e-ZrO\u003csub\u003e2\u003c/sub\u003e, La/Ni-promoted SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Sulfated zirconia (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e) and tungsten trioxide modified sulfated zirconia (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e), obtained by calcination at 700\u0026deg;C, both are highly active catalysts for the cracking and isomerization of hexane at 140\u0026deg;C [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Compared with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e is more active. However, the conversion of hexane over HY, which does not possess stronger acid properties than H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e, only occurs above 400\u0026deg;C [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Research has shown that both WO\u003csub\u003e3\u003c/sub\u003e and SO₄\u0026sup2;⁻ ions can prevent the agglomeration of ZrO\u003csub\u003e2\u003c/sub\u003e particles, thereby increasing the specific surface area of the catalyst. The optimal loading amount of WO\u003csub\u003e3\u003c/sub\u003e is equal to its dispersion threshold on ZrO\u003csub\u003e2\u003c/sub\u003e. The dispersed WO\u003csub\u003e3\u003c/sub\u003e also stabilizes the SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e ions that are coadsorbed on ZrO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In practical applications, they have demonstrated strong stability, non-corrosiveness to equipment, good recyclability, easy separation from products, and minimal environmental pollution, thus attracting significant attention [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. However, reports on the application of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e to alkylphenol dealkylation remain scarce.\u003c/p\u003e \u003cp\u003eIn this study, selected H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e solid acid as a catalyst for the dealkylation of BHT. H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e solid acid, with a higher proportion of strong Br\u0026oslash;nsted acid active sites, can catalyze the dealkylation of BHT under mild condition at 180\u0026deg;C, significantly lower than the catalytic reaction temperatures of zeolites such as H-ZSM-5 (250\u0026ndash;350\u0026deg;C). The incorporation of an appropriate amount of WO\u003csub\u003e3\u003c/sub\u003e can prevent the reduction of the monoclinic phase of zirconia, which supports the alkylation active centers. The effects of reaction temperature, reaction time, and sulfuric acid impregnation solution concentration on conversion and selectivity were investigated, and the recyclability of H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e solid acid was also examined. In addition, the catalytic performance and property characterization of the above materials with different acid strengths indicate that according to the Arrhenius equation (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{k}=\\text{A}{e}^{\\frac{{-E}_{a}}{RT}}\\)\u003c/span\u003e\u003c/span\u003e), the stronger Br\u0026oslash;nsted acidity results in the lower energy barrier, which needs the lower temperature to achieve the same reaction rate as weaker acid at higher temperature. Finally, the catalytic mechanism for the dealkylation of BHT by strong solid acid were proposed. These findings contribute to the understanding and guidance of the design of strong solid acid catalysts for low-temperature reactions and the further in-depth study of the laws of solid acid-catalyzed reaction under mild condition.\u003c/p\u003e"},{"header":"2. Experiments","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eBHT, DBMC, WO\u003csub\u003e3\u003c/sub\u003e, ZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO, (NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eW\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e\u0026middot;XH\u003csub\u003e2\u003c/sub\u003eO, 2\u003cb\u003e-\u003c/b\u003etert\u003cb\u003e-\u003c/b\u003ebutyl\u003cb\u003e-\u003c/b\u003e4\u003cb\u003e-\u003c/b\u003emethylphenol(2\u003cb\u003e-\u003c/b\u003eTBC), H\u003cb\u003e-\u003c/b\u003eZSM\u003cb\u003e-\u003c/b\u003e5, \u003cem\u003ep\u003c/em\u003e\u003cb\u003e-\u003c/b\u003ecresol was supplied by Shanghai McLean Biochemical Technology Co. Sulfuric acid, 6-tert-butyl-\u003cem\u003em\u003c/em\u003e-cresol (6-BMC), \u003cem\u003em\u003c/em\u003e\u003cb\u003e-\u003c/b\u003ecresol, \u003cem\u003en\u003c/em\u003e\u003cb\u003e-\u003c/b\u003eoctane, cyclohexane, ethanol was purchased from Chengdu Cologne Chemical Co., Ltd. Ammonia was purchased from Shanghai Aladdin Biochemical Science and Technology Co., Ltd. Other reagents were analytically pure and did not require further purification.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Catalyst preparation\u003c/h2\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1 \u003cem\u003ePreparation of x\u003c/em\u003e\u003cb\u003e-\u003c/b\u003e\u003cem\u003eH\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eSO\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ZrO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO was dissolved in deionized water. Under continuous magnetic stirring, aqueous ammonia (NH\u003csub\u003e3\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO) was slowly added dropwise until the pH reached approximately 9, resulting in the formation of a white precipitate. After filtration, the filter cake was repeatedly washed with deionized water until the complete removal of Cl⁻ was achieved. The resulting precipitate was dried at 105\u0026deg;C for 12 hours and then ground to a 100 mesh size. The fine powder was impregnated with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120\u0026deg;C for 4 hours. These sample was designated as x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-N, where x denotes the concentration of sulfuric acid used for impregnation of the support, with the unit of x mol/L. where N indicates that the sample was not calcined. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800\u0026deg;C for 4 hours. The corresponding solid acid was prepared and named x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2 \u003cem\u003ePreparation of x-H\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eSO\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/WO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eWO\u003csub\u003e3\u003c/sub\u003e was impregnated with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120\u0026deg;C for 4 hours. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800\u0026deg;C for 4 hours. The corresponding solid acid was prepared and named x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e (where x denotes the concentration of sulfuric acid used for impregnation of the support, x mol/L).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.2.3 \u003cem\u003ePreparation of x\u003c/em\u003e\u003cb\u003e-\u003c/b\u003e\u003cem\u003eH\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eSO\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ZrO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cb\u003e-\u003c/b\u003e\u003cem\u003eWO\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cb\u003e-\u003c/b\u003e\u003cem\u003eω\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe preparation steps of the x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-ω catalyst is shown in Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. First, a certain amount of ZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO and(NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eW\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e\u0026middot;XH\u003csub\u003e2\u003c/sub\u003eO was dissolved in deionized water. Under continuous stirring, ammonia solution was slowly added until the pH reached approximately 9, resulting in the formation of a white precipitate. The precipitate was washed to remove chloride ions. The resulting precipitate was dried at 105\u0026deg;C for 12 hours and then ground to a 100-mesh size. The fine powder was impregnated with H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solutions of different concentrations at a ratio of 15 mL/g for 20 minutes with continuous stirring. The well-mixed samples were then placed in an oven and dried at 120\u0026deg;C for 4 hours. The sample was designated as x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-N, where x denotes the concentration of sulfuric acid used for impregnation of the support, x mol/L, and N indicates that the samples were not calcined. Subsequently, the samples were calcined in a tube furnace under a nitrogen atmosphere at 800\u0026deg;C for 4 hours. The corresponding solid acid was prepared and named x-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-ω, where ω represents the mass fraction of WO\u003csub\u003e3\u003c/sub\u003e. The values of ω were 12%, 14%, 16%, 18%, and 20%, respectively. The material obtained after re-calcination at 800\u0026deg;C for 4 hours following five cycles of catalytic reaction is denoted as 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-RC.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Catalyst characterization method\u003c/h2\u003e \u003cp\u003eThe functional groups in the samples were tested using a Thermo Fisher Nicolet iS50 Fourier-transform infrared spectrometer (FT-IR). The phase of the prepared sample was analyzed using an X-ray diffractometer (Rigaku Ultima IV). The test samples were dried overnight in an oven at 100\u0026deg;C and then ground in an agate mortar. The ground samples were pressed into a glass sample holder for XRD analysis. Cu-Kα radiation (λ\u0026thinsp;=\u0026thinsp;0.1542 nm) was used, with a current of 40 mA and a voltage of 40 kV. The scanning range was 5\u0026ndash;90\u0026deg;, with a scanning speed of 8\u0026deg;/min and a step size of 0.02. The morphology and elemental distribution of the prepared samples were analyzed using a scanning electron microscope (FEI APREO). A small amount of test sample was attached to a conductive silicone. An accelerating voltage of 2 kV was used. The elemental distribution of the test material was qualitatively analyzed using the point and area scanning modes of an energy-dispersive X-ray spectrometer. The sample preparation method was the same as that for SEM, with an accelerating voltage of 10 kV. The thermal stability, thermal decomposition, and the correlation between products and mass loss of the samples were determined using a Mettler TGA 2 thermogravimetric analyzer under a nitrogen atmosphere with a heating rate of 10\u0026deg;C/min. The specific surface area and pore size distribution of the prepared samples were analyzed using a physical adsorption instrument (ASAP 2460, Micromeritics, USA). Approximately 0.2 g of the test sample was dried overnight in an oven at 100\u0026deg;C, then degassed under vacuum at 200\u0026deg;C for 12 h, and subsequently the N₂ adsorption-desorption isotherms of the sample was recorded at -196\u0026deg;C. The surface acidity of the sample was analyzed using a Fourier-transform infrared spectrometer (produced by Thermo Nicolet, USA) with pyridine adsorption infrared method. The samples were dried in an oven at 300\u0026deg;C for 3 h, adsorbed with pyridine under vacuum at room temperature, evacuated for 1 h, and maintained under vacuum for 20 h. After adsorption, the samples were dried in a vacuum oven at 150\u0026deg;C for 5 h to remove physically adsorbed pyridine. The samples were then placed in the infrared spectrometer, and diffuse reflectance infrared spectra were recorded in the range of 650\u0026ndash;4000 cm\u003csup\u003e-1\u003c/sup\u003e. The acid amount and acid strength of the samples were analyzed using a CHEMBET-3000 TPD/TPR analyzer (produced by Quantachrome, USA). The method involved heating the samples to 500\u0026deg;C under a helium atmosphere and holding for 30 min, cooling to 70\u0026deg;C, adsorbing ammonia for 30 min, purging with helium for 1 h, and then recording the NH\u003csub\u003e3\u003c/sub\u003e-TPD curve while ramping to the set temperature. The products of catalytic reaction were analyzed using a SP-6800A gas chromatograph. The specific instrument parameter settings and chromatographic column information are shown in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Catalytic reaction\u003c/h2\u003e \u003cp\u003eThe catalytic activity for BHT dealkylation was evaluated in a three-necked flask equipped with a reflux condenser. Typically, before each catalytic reaction test, 0.2 g of catalyst was thoroughly mixed with 10 g of BHT, and the reaction was carried out at 150\u0026ndash;200\u0026deg;C under a nitrogen atmosphere as a protective gas. The stirring rate was 10 r/s, and the nitrogen flow rate was 100 mL/min. After the reaction, the product composition was analyzed using a gas chromatograph with nitrogen as the carrier gas, and the composition of the reaction mixture was determined using the internal standard method.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Calculation of conversion, selectivity and yield\u003c/h2\u003e \u003cp\u003eThe calculation of conversion, selectivity and yield is provided in the Supporting Information.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Characterization\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the XRD patterns of the samples. Compared with the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e sample, the 0.1- H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample, which contains added tungsten, shows not only the characteristic peaks of the tetragonal phase of zirconia (t-ZrO\u003csub\u003e2\u003c/sub\u003e) at around 29.9\u0026deg;, 34.1\u0026deg;, 50.0\u0026deg;, and 60.1\u0026deg; but also significantly enhanced peaks of the monoclinic phase of zirconia (m-ZrO\u003csub\u003e2\u003c/sub\u003e) at around 28.1\u0026deg;, 31.5\u0026deg;, and 35.3\u0026deg; [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Additionally, new peaks at around 23.1\u0026deg;, 23.6\u0026deg;, and 24.4\u0026deg;, which are characteristic of the WO\u003csub\u003e3\u003c/sub\u003e phase, are observed. This is consistent with the literature reports that the addition of WO\u003csub\u003e3\u003c/sub\u003e alters the proportion of the two zirconia phases, and different tungsten contents affect the proportion of the two zirconia phases [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Therefore, the effect of WO\u003csub\u003e3\u003c/sub\u003e content on the crystalline structure of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e was investigated (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). As the WO\u003csub\u003e3\u003c/sub\u003e content increases from 12 wt.% to 20 wt.%, the peak height of the characteristic diffraction peak of WO\u003csub\u003e3\u003c/sub\u003e gradually increases. When the WO\u003csub\u003e3\u003c/sub\u003e mass content reaches 14%, the sample begins to show distinct diffraction peaks of monoclinic ZrO\u003csub\u003e2\u003c/sub\u003e. Then, with the further increase of WO\u003csub\u003e3\u003c/sub\u003e mass content to over 16%, the diffraction peaks of monoclinic ZrO\u003csub\u003e2\u003c/sub\u003e in the sample disappear. Therefore, 14 wt.% of WO\u003csub\u003e3\u003c/sub\u003e aids in the formation and stabilization of monoclinic ZrO\u003csub\u003e2\u003c/sub\u003e in 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14, preventing its transformation to tetragonal ZrO\u003csub\u003e2\u003c/sub\u003e and enhancing the acidity of the material [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The structure of each sample was also confirmed by infrared spectroscopy, as shown in Figure S2. The absorption peak at 499 cm\u003csup\u003e-1\u003c/sup\u003e corresponds to the vibration of the zirconium-oxygen bond [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], the peak at 1630 cm\u003csup\u003e-1\u003c/sup\u003e is characteristic of adsorbed water, and the peak at 3446 cm\u003csup\u003e-1\u003c/sup\u003e is due to the stretching vibration of hydroxyl groups.\u003c/p\u003e \u003cp\u003eCompared with the support that was not impregnated with sulfuric acid solution, the reason for the smaller particle size of the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample may be due to the corrosive nature of the impregnation solution used (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e2\u003c/span\u003e). And the uncalcined 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-N sample has larger particles than the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e2\u003c/span\u003ee), which may be attributed to the decomposition of zirconium hydroxide during the calcination process. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e2\u003c/span\u003ef, the particles of the catalyst become smaller after calcination following the five catalytic cycles, which is attributed to the continuous mechanical stirring during the reaction causing the catalyst particles to break. As can be seen from the energy-dispersive X-ray (EDX) spectrum of the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e2\u003c/span\u003eg), the elements Zr, W, O, and S are uniformly distributed in the sample.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the TG and DTG curves of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-N. The weight loss in the curve from 50\u0026deg;C to 200\u0026deg;C is mainly attributed to the volatilization of adsorbed water in the sample. The second stage, from 200\u0026deg;C to 650\u0026deg;C, shows that the TG curve continues to decline, albeit at a significantly reduced rate. The weight loss in this stage is primarily due to the volatilization of chemically bound water [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. And the mass loss of 4.8% between 650 and 800\u0026deg;C is attributed to the decomposition of zirconium hydroxide in 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-N. As the pyrolysis temperature increases further, the DTG curve gradually levels off, indicating that the zirconium hydroxide in the sample is almost completely decomposed around 800\u0026deg;C.\u003c/p\u003e \u003cp\u003eThe specific surface area and pore size distribution of different solid acids have a significant impact on the dealkylation of BHT. Therefore, N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption characterization was used to analyze the specific surface area and average pore size of samples with different sulfuric acid impregnation concentrations, as well as those after five catalytic cycles and re-calcination (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e4\u003c/span\u003e). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms of all samples exhibit distinct type IV isotherm characteristics and H4 hysteresis loops [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. The hysteresis loops in the high-pressure region indicate the presence of mesoporous structures in the samples. The pore size distribution diagrams obtained from the adsorption curves (Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) also confirm the existence of mesoporous structures.\u003c/p\u003e \u003cp\u003eThe N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms of samples prepared with different tungsten contents and different sulfuric acid impregnation concentrations show significant differences. Compared with the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e sample, the addition of WO\u003csub\u003e3\u003c/sub\u003e in the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample significantly increases the pore size of the mesopores (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). With the increase of sulfuric acid impregnation concentration, the specific surface area of the samples first increases and then decreases, with the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample having the largest specific surface area. The impregnation load with sulfuric acid did not significantly reduce the specific surface area and average pore size of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample, compared with the ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample. In addition, the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-RC sample has a specific surface area, pore volume, and average pore size comparable to those of the freshly prepared sample.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSpecific surface area, pore volume and average pore size of solid acid catalysts.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalyst\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/ m\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eV\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003eb\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/ cm\u003csup\u003e3\u003c/sup\u003e\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ed\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e\u003csup\u003e\u003cem\u003ec\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e/ nm\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e108.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9.74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e53.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.01-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e47.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.69\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e23.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14- RC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e43.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003ea: BET surface area; b: total pore volume; c: average pore diameter.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe distribution of Br\u0026oslash;nsted (B) and Lewis (L) acid sites on the surfaces of 0.1- H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 samples was determined using pyridine adsorption infrared spectroscopy (Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Pyridine molecules adsorbed on B acid sites are protonated, resulting in a characteristic infrared peak at 1540 cm\u003csup\u003e-1\u003c/sup\u003e. Pyridine molecules adsorbed on L acid sites form coordinate bonds with the L acid centers due to the donation of electron pairs from the nitrogen atoms, leading to a characteristic infrared peak at 1445 cm\u003csup\u003e-1\u003c/sup\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the addition of WO\u003csub\u003e3\u003c/sub\u003e significantly affects the distribution of B and L acid sites on the catalysts [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTaking the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 catalyst as a reference standard and setting its relative total acid amount to 100, the relative amounts of B acid, L acid and total acid, as well as the ratio of B acid to L acid for other catalysts, were calculated. The specific results are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The appropriate addition of WO\u003csub\u003e3\u003c/sub\u003e can effectively increase the total acid amount and B acid content on the surface of the solid acid, while reducing the L acid content on the catalyst surface.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe relative amount of different types of acid sites.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalyst\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRelative acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLewis acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBr\u0026oslash;nsted acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eB/L \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e26.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e27.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e39.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003ea: The contents of Br\u0026oslash;nsted and Lewis acid sites were determined by Py-IR: the integrated area of the band at 1540 cm\u003csup\u003e-1\u003c/sup\u003e was taken as the Br\u0026oslash;nsted acid amount, and that at 1450 cm\u003csup\u003e-1\u003c/sup\u003e as the Lewis acid amount; the total acid amount of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 was set to 100, and the corresponding peak areas of the other samples were scaled proportionally to obtain the relative acid amounts.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/M\u003csub\u003ex\u003c/sub\u003eO\u003csub\u003eγ\u003c/sub\u003e solid acids, the oxygen end of the SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e group exhibits significant electron-withdrawing properties, causing the electron cloud in the Zr-O-S bond to shift towards the S\u0026thinsp;=\u0026thinsp;O bond, thereby enhancing the L acidity of the catalyst. However, when tungsten, which has a higher electronegativity than zirconium, is added to SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2-\u003c/sup\u003e/ ZrO\u003csub\u003e2\u003c/sub\u003e, W forms Zr-O-W bonds with Zr atoms, competing with S atoms for electrons, weakening the polarity of the Zr-O-S bond, and ultimately reducing the number and strength of L acid centers. Nevertheless, the addition of WO\u003csub\u003e3\u003c/sub\u003e can to some extent increase the B acid amount of the catalyst. On the one hand, the presence of a small amount of water molecules or hydroxyl groups can convert L acid sites to B acid sites. On the other hand, some reduced WO\u003csub\u003eX\u003c/sub\u003e species in the system can form B acid sites by stabilizing hydrogen protons, and Zr atoms encapsulated by WO\u003csub\u003eX\u003c/sub\u003e octahedra can combine with OH groups to generate B acid sites with higher strength [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. However, as the content of WO\u003csub\u003e3\u003c/sub\u003e continues to increase, WO\u003csub\u003eX\u003c/sub\u003e octahedra gradually aggregate to form three-dimensional WO\u003csub\u003e3\u003c/sub\u003e crystalline particles, disrupting the B acid sites formed by WO\u003csub\u003eX\u003c/sub\u003e species, thereby reducing the overall acid strength and the number of acid centers.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the NH\u003csub\u003e3\u003c/sub\u003e-TPD spectra of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14. The prepared solid acid samples exhibit four distinct peaks, corresponding to weak acid sites (\u0026lt;\u0026thinsp;250\u0026deg;C), medium-strong acid sites (250\u0026ndash;450\u0026deg;C), and strong acid sites (\u0026gt;\u0026thinsp;450\u0026deg;C) [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Compared with the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e samples, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 has a more pronounced strong acid peak, especially in the range of 550\u0026ndash;700\u0026deg;C where the NH\u003csub\u003e3\u003c/sub\u003e desorption peak at 640\u0026deg;C corresponds to a more pronounced strong acid peak. However, H-ZSM-5 only exhibited a desorption peak of NH\u003csub\u003e3\u003c/sub\u003e with a peak tip at 510\u0026deg;C [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The above results indicate that 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 has stronger acid sites than H-ZSM-5.\u003c/p\u003e \u003cp\u003eTaking 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 as the standard, with its relative total acid amount set at 100, the relative contents of weak acid, medium-strong acid, strong acid and total acid amount for 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 were calculated, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The addition of an appropriate amount of WO\u003csub\u003e3\u003c/sub\u003e significantly increases the total acid amount, especially the content of strong acid sites, of the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample compared to solid acids prepared from single metal oxides.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe relative amount of acid sites of different intnesities.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalysts\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRelative weak acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRelative medium acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRelative strong acid amount\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRelative total acid amount\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e62.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e55.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Catalytic performance\u003c/h2\u003e \u003cp\u003eAs can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e7\u003c/span\u003e, when the ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample that was not impregnated with sulfuric acid solution was used to catalyze the dealkylation of BHT, the conversion is only 85.1%, and the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol is only 74.6%. When ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 was impregnated with sulfuric acid solutions of different concentrations, the conversion of BHT remains above 99.9% with increasing impregnation solution concentration, while the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol first increases and then decreases. 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 shows the best catalytic performance. Similarly, Zhang et al. [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e] modified ZrO\u003csub\u003e2\u003c/sub\u003e with sulfuric acid to catalyze the isomerization and arylation of oleic acid and found that the activity of the sulfuric acid-modified zirconia was three times that of the catalyst without sulfuric acid impregnation. Since the highest conversion of BHT dealkylation and selectivity of \u003cem\u003ep\u003c/em\u003e-cresol is achieved when the concentration of the impregnation solution is 0.1 mol/L, a sulfuric acid concentration of 0.1 mol/L was used in subsequent experiments to explore the optimal reaction conditions.\u003c/p\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the catalytic activity and selectivity of the target product \u003cem\u003ep\u003c/em\u003e-cresol of the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e catalyst system are higher than those of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e. The sample with 14 wt.% WO\u003csub\u003e3\u003c/sub\u003e exhibits the best catalytic performance. In combination with the catalyst characterization results, it can be seen that 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e has the largest specific surface area (108.00 m\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e, see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and a higher number of relative strong Br\u0026oslash;nsted acid sites (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e has fewer acid centers, especially a lower proportion of Br\u0026oslash;nsted acid centers than 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e. 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e exhibits higher catalytic activity and \u003cem\u003ep\u003c/em\u003e-cresol selectivity than 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e. It can be inferred that acid centers, especially strong Br\u0026oslash;nsted acid centers, are the more active dealkylation active centers. Similarly, in contrast to 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/WO\u003csub\u003e3\u003c/sub\u003e and 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, although 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 has a smaller specific surface area (57.27 m\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e-1\u003c/sup\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) than 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e, it has the highest acid density and strong acid Br\u0026oslash;nsted acid content, showing the highest dealkylation activity and \u003cem\u003ep\u003c/em\u003e-cresol selectivity. Therefore, 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 exhibits higher catalytic activity and selectivity towards \u003cem\u003ep\u003c/em\u003e-cresol at lower reaction temperatures (180\u0026deg;C) than H-ZSM-5 at higher reaction temperatures (250\u0026ndash;350\u0026deg;C), attributed to the stronger Br\u0026oslash;nsted acid sites and larger pore size of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 compared to H-ZSM-5 (see Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and S3 for details). In summary, we can infer that the stronger the acidity of the Br\u0026oslash;nsted acid center, the more easily it can donate a proton to activate the alkylphenol to form an active alkyl carbocation at lower temperature, thereby facilitating the dealkylation at lower temperature. This provides a new idea for the further in-depth design of acid catalysts for the dealkylation of alkylphenols under mild conditions in industry.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe dealkylation performance of BHT using different solid acids.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalysts \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConv./%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSel \u003csub\u003e2-TBC\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSel \u003csub\u003e\u003cem\u003ep\u003c/em\u003e-cresol\u003c/sub\u003e/%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSel \u003csub\u003eOther\u003c/sub\u003e/% \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH-ZSM-5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e80.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ WO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e87.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e81.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e90.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e85.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e89.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e95.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e89.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003ea: For the dealkylation catalyzed by the solid acid, 10 g of BHT was charged with 0.2 g of catalyst, and the mixture was reacted at 180\u0026deg;C for 6 h.;b: the other isomerization by-products and other impurities.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe effects of reaction time and temperature on the dealkylation of BHT catalyzed by 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e8\u003c/span\u003ea and \u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, respectively. Both the conversion of BHT and the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol increase with increasing reaction time. After 3 h, the conversion of BHT gradually increases to 99.9%. And after 6 h, the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol reaches 95.0%. Figure\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e8\u003c/span\u003eb shows the effect of reaction temperature on the dealkylation of BHT catalyzed by 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14. When the reaction temperature increases from 140\u0026deg;C to 160\u0026deg;C, the conversion of BHT rapidly increases to 99.9%, and the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol also gradually increases with increasing reaction temperature. When the reaction temperature rises from 160\u0026deg;C to 190\u0026deg;C, the conversion of BHT remains at 99.9%, and the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol continues to increase with increasing reaction temperature.\u003c/p\u003e \u003cp\u003eAfter a catalytic reaction, the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample was filtered and separated, washed repeatedly with anhydrous ethanol, and then dried in an oven at 60\u0026deg;C for 12 h. The recovered solid acid was used for the next catalytic reaction under the same condition as the first reaction cycle. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, the recyclability of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 without calcination after catalytic reaction was poor, with the conversion of BHT and the selectivity of \u003cem\u003ep\u003c/em\u003e-cresol gradually decreasing. After re-calcination following five cycles of catalytic reactions, the catalytic activity was comparable to that of the fresh sample in its first reaction cycle. XRD characterization results (Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e9\u003c/span\u003eb) show that, compared with the fresh catalyst, the characteristic peaks of the monoclinic phase of zirconia, which supports the active centers in the 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14-RC sample after five cycles and re-calcination, did not change significantly at around 29.8\u0026deg;, 34.1\u0026deg;, 50.0\u0026deg;, and 60.1\u0026deg;.The disappearance and shift of the characteristic peaks of the WO\u003csub\u003e3\u003c/sub\u003e sample indicate that the crystal form of W element in the sample after five cycles and calcination has changed, resulting in a more uniform distribution in ZrO\u003csub\u003e2\u003c/sub\u003e. In addition, the catalytic performance of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 in the dealkylation of DBMC shows that, despite the different substitution position of the same substituent in DBMC and BHT, the spatial steric and electronic effects on catalytic performance are minimal (Table S2).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Reaction mechanism\u003c/h2\u003e \u003cp\u003eIt is generally believed that the dealkylation of alkylphenols follows the acid-catalyzed carbocation mechanism and is the reverse reaction of the Friedel-Crafts alkylation. And the Friedel-Crafts alkylation reaction of cresol with isobutylene is an electrophilic substitution reaction on the aromatic ring of cresol, which is divided into two steps. First, the \u003cem\u003ep\u003c/em\u003e-cresol molecule is adsorbed on the acid site of the catalyst surface. The B acid on the catalyst releases H⁺, which reacts with isobutylene to form a carbocation. Second, the carbocation attacks a carbon atom on the aromatic ring to generate 2-tert-butyl-\u003cem\u003ep\u003c/em\u003e-cresol. Similarly, 2-tert-butyl-\u003cem\u003ep\u003c/em\u003e-cresol repeats the same steps and subsequent processes as \u003cem\u003ep\u003c/em\u003e-cresol. Based on the above characterization of the H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e3\u003c/sub\u003e\u0026ndash;WO\u003csub\u003e3\u003c/sub\u003e catalyst and the analysis of its catalytic performance for BHT, it can be inferred that the reaction mechanism for the dealkylation of alkylphenols catalyzed by strong solid acid is as follows (Fig.\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e10\u003c/span\u003e). First, the BHT molecule is adsorbed on the acidic sites of the catalyst surface. The B acid center near the adsorbed reactants releases a proton. The released proton attacks the carbon atom of the tert-butyl group in the electron-rich BHT in an electrophilic manner, forming a carbocation with a positively charged carbon on the aromatic ring. Then, the electron on the activated tert-butyl C\u003csub\u003eα\u003c/sub\u003e is transferred to the adjacent aromatic carbon, forming tert-butyl-\u003cem\u003ep\u003c/em\u003e-cresol. The activated tert-butyl group is replaced by a proton to form of a tert-butyl carbocation. At the same time, one electron from the C-H bond on the C\u003csub\u003eβ\u003c/sub\u003e of the tert-butyl carbocation is transferred to C\u003csub\u003eα\u003c/sub\u003e. After a hydrogen atom on C\u003csub\u003eβ\u003c/sub\u003e is released as a proton and returns to the sulfonic acid group on the catalyst that is lacking a proton, isobutylene is formed and the catalyst is restored to its original state, completing a catalytic reaction cycle. Through the same catalytic reaction process, 2\u003cb\u003e-\u003c/b\u003eTBC releases isobutylene to form \u003cem\u003ep\u003c/em\u003e-cresol. Therefore, designing and synthesizing catalysts with relatively stronger acid centers can effectively catalyze the dealkylation and decrease the reaction temperature to some extent, which is of great significance to industrial production.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO, (NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eW\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e\u0026middot;XH\u003csub\u003e2\u003c/sub\u003eO, and ammonia water were used as raw materials to synthesize the ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e supports. By adjusting the amount of (NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eW\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e\u0026middot;XH\u003csub\u003e2\u003c/sub\u003eO added, different supports were prepared. These supports were then impregnated with sulfuric acid solutions of different concentrations to prepare a series of solid acid catalysts. The 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 sample with 14 wt.% WO\u003csub\u003e3\u003c/sub\u003e and impregnated with 0.1 mol/L sulfuric acid aqueous solution shows the best catalytic performance for the new application of BHT dealkylation. This catalyst has a relatively higher specific surface area, a suitable mesoporous pore size distribution, a higher ratio of Br\u0026oslash;nsted acid to Lewis acid sites, and a greater amount of strong Br\u0026oslash;nsted acid sites, thus exhibiting the best performance in the BHT dealkylation. After catalyzing the BHT dealkylation at the mild condition of 180 \u0026ordm;C for 6 hours, the conversion of BHT was greater than 99.9%, and the selectivity for \u003cem\u003ep\u003c/em\u003e-cresol reached 95.0%. After five cycles of reaction, the catalyst was re-calcined and its catalytic activity was restored for further cycle. It is found that the primary role of tungsten oxide may be to stabilize the monoclinic phase of ZrO\u003csub\u003e2\u003c/sub\u003e and to facilitate the formation of more strong Br\u0026oslash;nsted acid sites. Furthermore, it is found that designing and synthesizing catalysts with relatively stronger acid centers can effectively catalyze the dealkylation and decrease the reaction temperature to some extent. These findings contribute to the understanding and guidance of the design of strong solid acid catalysts and further in-depth studies on the laws of solid acid-catalyzed reaction under mild condition.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e2,6-di-tert-butyl-4-methylphenol: BHT\u003c/p\u003e\n\u003cp\u003e4,6-di-tert-butyl-\u003cem\u003em\u003c/em\u003e-cresol: DBMC\u003c/p\u003e\n\u003cp\u003e2\u003cstrong\u003e-\u003c/strong\u003etert\u003cstrong\u003e-\u003c/strong\u003ebutyl\u003cstrong\u003e-\u003c/strong\u003e4\u003cstrong\u003e-\u003c/strong\u003emethylphenol: 2\u003cstrong\u003e-\u003c/strong\u003eTBC\u003c/p\u003e\n\u003cp\u003e6-tert-butyl-\u003cem\u003em\u003c/em\u003e-cresol: 6-BMC\u003c/p\u003e\n\u003cp\u003eFourier Transform Infrared Spectroscopy: FT-IR\u003c/p\u003e\n\u003cp\u003eThermogravimetric analysis: TG\u003c/p\u003e\n\u003cp\u003eDerivative Thermogravimetry: DTG\u003c/p\u003e\n\u003cp\u003eX-ray diffraction: XRD\u003c/p\u003e\n\u003cp\u003eScanning Electron Microscope: SEM:\u003c/p\u003e\n\u003cp\u003eBrunauer\u0026ndash;Emmett\u0026ndash;Teller: EDX\u003c/p\u003e\n\u003cp\u003eBrunauer\u0026ndash;Emmett\u0026ndash;Teller: BET\u003c/p\u003e\n\u003cp\u003eAmmonia Temperature-Programmed Desorption:\u0026nbsp;NH\u003csub\u003e3\u003c/sub\u003e-TPD\u003c/p\u003e\n\u003cp\u003eMonoclinic phase of zirconia: m-ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003eTetragonal phase of zirconia: t-ZrO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics and Consent to Participate\u0026nbsp;\u003c/strong\u003eThis study does not involve human participants, human data, or animal experiments. Therefore, no ethical approval or informed consent to participate is required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u0026nbsp;\u003c/strong\u003eAll authors have read and approved the final manuscript, and consent to its publication in \u003cem\u003eCatalysis Letters\u003c/em\u003e. All authors confirm that the manuscript has not been published previously, is not under consideration for publication elsewhere, and its publication is approved by all authors and, if applicable, by the authorities where the work was carried out.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u0026nbsp;\u003c/strong\u003eThe authors have no competing interests to declare that are relevant to the content of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u0026nbsp;\u003c/strong\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Hengfu Yang, Guoming Zhao, Xing Fan, Chunxiao Qiao, Bingfei Li, Xiang Bai and Xianyong Wei. The first draft of the manuscript was written by Hengfu Yang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThis work was supported by the Natural Science Foundation of Yili Normal University (Grant 22XKZY18), the Key Research and Technology Development Projects of Yili Prefecture (YZD2024A18),\u0026nbsp;the Major Science and Technology Projects of Xinjiang Uygur Autonomous Region (2024A01006),\u0026nbsp;and the National Natural Science Foundation of China (Grant 21676293).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u0026nbsp;\u003c/strong\u003eThe data that support the findings of this study are available on request.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u0026nbsp;\u003c/strong\u003eThe authors would like to express their sincere gratitude to Guoming Zhao/Xing Fan for their valuable guidance and suggestions during the research process.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePan C, Guo J, Liu Y et al (2024) Efficient separation of cresol isomers using azeotropic coupling pressure-swing distillation: From separation mechanism to process integration. 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ACS Phys Chem Au 3:74\u0026ndash;83. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acsphyschemau.2c00040\u003c/span\u003e\u003cspan address=\"10.1021/acsphyschemau.2c00040\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang S, Zhou J, Zhang ZC (2008) Isomerization and arylation of oleic acid on anion modified zirconia catalysts. Catal Lett 127:33\u0026ndash;38. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10562-008-9743-7\u003c/span\u003e\u003cspan address=\"10.1007/s10562-008-9743-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Scheme 1","content":"\u003cp\u003eScheme 1 is not available with this version.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Strong solid acid, H2SO4, Dealkylation, Cresol, WO3, ZrO2","lastPublishedDoi":"10.21203/rs.3.rs-8814026/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8814026/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eZrOCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO, (NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eW\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e\u0026middot;XH\u003csub\u003e2\u003c/sub\u003eO and aqueous ammonia were used as raw materials to prepare solid oxide supports with varying tungsten contents (ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e) via the co-precipitation method. A series of solid acid catalysts were subsequently prepared by impregnating these supports with sulfuric acid solutions of different concentrations. The effects of crystal structure regulation on the acid properties of these catalysts on tunning the reaction performance of 2,6-di-tert-butyl-4-methylphenol (BHT) dealkylation to produce \u003cem\u003ep\u003c/em\u003e-cresol were first investigated. The primary role of tungsten oxide may be to stabilize the monoclinic phase of ZrO\u003csub\u003e2\u003c/sub\u003e and to facilitate the formation of more and stronger Br\u0026oslash;nsted acid sites. The sample with a WO\u003csub\u003e3\u003c/sub\u003e mass fraction of 14% prepared using a 0.1 mol/L sulfuric acid solution (0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14) exhibits the highest specific surface area (57.27 m\u003csup\u003e2\u003c/sup\u003e\u0026middot;g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), a suitable pore size structure (average pore size of 13.69 nm), the highest content of strong Br\u0026oslash;nsted acid. As a result, it achieves the highest conversion of BHT (greater than 99.9%) and selectivity for \u003cem\u003ep\u003c/em\u003e-cresol (95.0%) under mild reaction condition at 180\u0026deg;C, significantly lower than the catalytic reaction temperatures of zeolites such as H-ZSM-5 (250\u0026ndash;350\u0026deg;C). This is attributed to its stronger Br\u0026oslash;nsted acidity compared to H-ZSM-5, decreasing the energy barrier of dealkylation to enable high catalytic performance at lower temperature, which needs higher temperature on weaker acid, according to the Arrhenius equation (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{k}=\\text{A}{e}^{\\frac{{-E}_{a}}{RT}}\\)\u003c/span\u003e\u003c/span\u003e). Furthermore, after five cycles of reaction, the catalytic performance of 0.1-H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e/ZrO\u003csub\u003e2\u003c/sub\u003e-WO\u003csub\u003e3\u003c/sub\u003e-14 decreased somewhat, but it was essentially restored after re-calcination. These studies will contribute to the understanding and guidance of the design of strong solid acid for low-temperature catalytic reactions and the further in-depth exploration of the laws of solid acid-catalyzed reactions under mild conditions.\u003c/p\u003e","manuscriptTitle":"The qualitative correlation between activation energy and acid strength: the influence of crystal structure regulation on the acidity of H 2 SO 4 /ZrO 2 -WO 3 in low-temperature dealkylation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-18 10:13:25","doi":"10.21203/rs.3.rs-8814026/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f4525336-6b13-49d2-b522-7b8f23a8f84c","owner":[],"postedDate":"February 18th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-17T14:41:48+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-18 10:13:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8814026","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8814026","identity":"rs-8814026","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}