Seed-Assisted Hierarchical H-ZSM-5: Overcoming Diffusion Barriers for Efficient Recyclable Oleic Acid Isomerization to Commercial Isostearic Acid

Seed-Assisted Hierarchical H-ZSM-5: Overcoming Diffusion Barriers for Efficient Recyclable Oleic Acid Isomerization to Commercial Isostearic Acid | 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 Seed-Assisted Hierarchical H-ZSM-5: Overcoming Diffusion Barriers for Efficient Recyclable Oleic Acid Isomerization to Commercial Isostearic Acid Xincheng Li, Pengpeng Huang, Mingming Fan, Pingbo Zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8280043/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Isostearic acid, a bio-based and environmentally friendly chemical, has attracted considerable attention because of its high value as an oleic acid derivative. The synthesis of isostearic acid via oleic acid isomerization over commercial H-ZSM-5 zeolites is limited by low yield and acid value, mainly due to diffusion constraints. To address this issue, a hierarchical-pore H-ZSM-5 zeolite (Meso-5) was synthesized using Silicalite-1(S-1) as a seed crystal to enhance diffusion and catalytic performance. The catalyst was comprehensively characterized by XRD, SEM, BET, TGA, FT-IR, and Py-FTIR. Meso-5 efficiently catalyzed the isomerization of oleic acid, attributed to its abundant Brønsted and Lewis acid sites whose synergistic interaction significantly promoted the formation of branched-chain products. The catalyst delivered a selectivity of 87.3% with a 71.1% yield in the first run, and even after five reuse cycles it maintained 82.1% selectivity with a 55.6% yield. Evidently, the hierarchical pore structure of the catalyst significantly facilitated the diffusion of oleic acid molecules and their isomerized intermediates, thereby enhancing the overall catalytic activity. The resulting isostearic acid was purified via a simple recrystallization procedure to a purity of 83.4% and an acid value of 186.7 mg KOH/g, both meeting the standards of commercial isostearic acid. These findings provide a robust basis for further catalyst optimization and scale-up toward industrial isostearic acid production. Isostearic acid Oleic acid Isomerization Hierarchical H-ZSM-5 zeolite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1 Introduction Isostearic acid is a mixture of saturated fatty acid isomers of stearic acid featuring unique branched structures[ 1 ]. The presence of methyl or ethyl branches at various positions along the carbon chain endows isostearic acid with multiple distinctive properties[ 2 ]. It has a relatively low melting point and is usually liquid at room temperature, exhibiting excellent cold-flow performance[ 3 ]. Moreover, as a saturated fatty acid, isostearic acid possesses outstanding oxidative stability[ 4 ]. These characteristics make it widely applicable in biomedical applications, cosmetics, lubricants, metalworking fluids, and coatings[ 5 ]. The isomerization of oleic acid is typically catalyzed by Brønsted acids, making zeolites well-suited for this type of reaction[ 6 , 7 ]. H-ZSM-5 zeolite, a high-silica zeolite with a three-dimensional 10-membered ring channel structure, exhibits high hydrothermal stability and strong acidity, and has been widely applied in catalysis, including toluene disproportionation and xylene isomerization[ 8 , 9 ]. H-ZSM-5 is generally synthesized using quaternary ammonium salts as structure-directing agents (SDAs), such as tetrapropylammonium hydroxide (TPAOH) and tetraethylammonium hydroxide (TEAOH). When a single SDA is used, the resulting H-ZSM-5 crystals tend to be relatively large, ranging from several hundred nanometers to several hundred micrometers[ 10 – 12 ]. At relatively low temperatures and high pressures, ZSM-5 can catalyze the liquid-phase isomerization of xylene with remarkable selectivity, providing insights for oleic acid isomerization[ 13 – 15 ]. Due to its larger molecular size, oleic acid encounters steric limitations in the narrow H-ZSM-5 channels, which reduces the contact between the molecules and the active sites, lowers molecular diffusion rates, and ultimately limits the catalytic activity[ 16 , 17 ]. To overcome diffusion limitations in zeolite-catalyzed reactions, hierarchical porous zeolites have been increasingly employed in recent years[ 18 – 20 ]. There are two main strategies for preparing hierarchical zeolites. The first involves integrating micropores and mesopores, typically achieved by introducing mesopore-directing agents during synthesis or via post-synthetic treatments[ 21 , 22 ]. The second strategy is to synthesize small zeolite crystals, which tend to aggregate and generate abundant mesopores[ 23 , 24 ]. The seed-assisted synthesis method is an effective approach for producing such mesoporous H-ZSM-5, as it can accelerate crystallization and reduce the amount of template required[ 25 ]. Mesoporous H-ZSM-5 can also be synthesized without SDAs by adding seeds with an average particle size of approximately 70 nm[ 26 ]. Among the factors affecting zeolite synthesis, crystallization temperature and time have the most significant impact, followed by alkalinity and seed particle size[ 27 – 29 ]. Even without SDAs, precise control of these parameters allows the formation of uniform, small zeolite crystals[ 30 ]. Zhang et al. developed a salt-assisted seed-induced method to synthesize nanosized ZSM-5 using S-1 as seeds[ 31 ]. In SDA-assisted syntheses with tetrapropylammonium bromide (TPABr), the addition of potassium fluoride (KF) reduces crystallization time and SDA usage while broadening the Si/Al ratio range[ 32 ]. By controlling the amount of KF, the mesopore volume can be precisely tuned. Using S-1 as seeds, Chen et al. synthesized mesoporous ZSM-5 with cetyltrimethylammonium bromide (CTAB) and TPAOH as SDAs[ 33 ]. The addition of CTAB suppresses secondary crystal growth and promotes mesopore formation, and increasing the amount of S-1 seeds results in smaller primary crystals[ 34 – 36 ]. In this study, hierarchical H-ZSM-5 was synthesized using S-1 as seeds and TPAOH as SDA. The effect of different seed types on the morphology of the samples was investigated. The structure of the hierarchical H-ZSM-5 was characterized by XRD, SEM, nitrogen adsorption–desorption analysis, FT-IR, TGA, and Py-FTIR. Furthermore, the synthesized hierarchical H-ZSM-5 was employed for the isomerization of oleic acid to evaluate its catalytic performance. 2 Experimental Section 2.1 Materials Oleic acid (≥ 90%, Aladdin, acid value: 192.3 mg KOH/g ), fumed silica (SiO 2 , Sigma-Aldrich), TPAOH (25 wt.% in water), anhydrous ethanol (AR), tetraethyl orthosilicate (TEOS, AR), sodium aluminate (NaAlO 2 , AR), sodium hydroxide (NaOH, AR), ammonium chloride (NH 4 Cl, AR), and H-ZSM-5 zeolite (Macklin) were used as received. Deionized water was used throughout the experiments. All reagents were of analytical grade and employed without further purification. 2.2 Synthesis of the Zeolite In a typical synthesis, 32.51 g of TPAOH, 36.80 g of anhydrous ethanol, and 47.61 g of deionized water were added to a beaker and stirred for 30 min to obtain a homogeneous solution. Subsequently, 41.68 g of TEOS was slowly added dropwise into the solution under continuous stirring. The mixture was further stirred for 3 h to allow aging. The aged gel was then transferred into a Teflon-lined autoclave and crystallized hydrothermally at 140°C for 64 h. The resulting product was centrifuged, washed with deionized water, and dried. Finally, the dried solid was calcined at 550°C for 6 h in air to remove the organic SDA, yielding the S-1 seed crystals. In the synthesis of hierarchical H-ZSM-5 zeolite, S-1 was used as the seed, fumed silica as the silica source, and sodium aluminate (NaAlO 2 ) as the aluminum source. In a beaker, 58.70 g of deionized water was first added, followed by 1.64 g of NaAlO 2 , 0.48 g of NaOH, 8.13 g of TPAOH, and 2 g of S-1 seed under continuous stirring for 3 h to form mixture A. Then, 12 g of fumed silica was gradually added into mixture A under stirring, and the resulting suspension was aged for 4 h to obtain mixture B. Mixture B was transferred into a Teflon-lined autoclave and crystallized hydrothermally at 180°C for 48 h. The resulting material was collected by filtration, washed with deionized water until neutral, and dried overnight at 70°C. The dried sample was then calcined at 550°C for 4 h in air to remove the template. Ion exchange of the calcined sample with 1 M aqueous NH 4 Cl solution yielded NH 4 -ZSM-5, which was subsequently calcined at 400°C for 4 h in air with a heating rate of 3°C/min to obtain the hierarchical H-ZSM-5, denoted as Meso-5. For comparison, the commercially available H-ZSM-5 zeolite was denoted as H-5. The H-ZSM-5 zeolite synthesized using the commercial H-5 as the seed was denoted as SH-5, while the H-ZSM-5 zeolite synthesized without any seed was denoted as N-5. A schematic illustration of the synthesis process is shown in Fig. 1. 2.3 Experimental Methods and Data Evaluation The isomerization of oleic acid was carried out in a high-pressure stainless-steel autoclave. In a typical experiment, 60 g of oleic acid, 4.8 g of zeolite catalyst, and 2.4 g of deionized water were added to the reactor. The air inside the autoclave was purged with nitrogen five times, and the final nitrogen pressure was adjusted to 0.5 MPa. The mixture was stirred at 500 rpm and heated to 250 ~ 290°C, maintaining the reaction for 6 h. After completion, the reactor was cooled to room temperature, residual gases were vented, and the reaction mixture was filtered. The filtrate contained the isomers of oleic acid, while the solid residue consisted of the zeolite catalyst. The hydrogenation of the isomers of oleic acid was performed in a high-pressure stainless-steel autoclave. A certain amount of isomers of oleic acid and Ni-based hydrogenation catalyst (Ni/C) were added to the reactor. The air inside the autoclave was purged with nitrogen five times, followed by purging with hydrogen five times. Finally, the isomers of oleic acid were hydrogenated under specific conditions (Reaction condition: 40 g of the isomers of oleic acid, 0.4 g Ni/C, 220°C, 4 MPa H 2 , 4 h). After the reaction was completed, the autoclave was cooled to room temperature, and the residual gas was released. The reaction mixture was then filtered, and the filtrate was collected as the crude isostearic acid. The crude product was dissolved in an appropriate amount of n-hexane and subjected to low-temperature recrystallization. The filtrate was subsequently distilled under reduced pressure to remove the solvent, yielding the purified isostearic acid. Scheme 1 shows the reaction process for producing isostearic acid from oleic acid. Oleic acid is first isomerized over hierarchical H-ZSM-5 to form isomers of oleic acid, which is then hydrogenated at C = C to yield isostearic acid. The reaction products were first converted to their methyl esters, and the composition was quantified by gas chromatography (GC). The GC analysis was performed with an initial oven temperature of 150°C, ramped at 10°C·min -1 to 270°C, and held at 270°C for 7 min. The acid values of both the crude and purified isostearic acid products were determined using the ethanolic hot method. The conversion of key components and the selectivity of the target product were calculated according to the corresponding equations. The conversion of key component A, the selectivity of the target product, and the yield of the target product were calculated using the following equations: 2.4 Catalyst characterizations The X-ray diffraction (XRD) patterns of the samples were recorded on a Bruker D8 Advance diffractometer (Germany) at a scanning rate of 4 °/min over a 2θ range of 5°-50°. The relative crystallinity was calculated by integrating the peak area within the range of 22°~25°, using the sample with the largest peak area as the reference (defined as 100%). The relative crystallinity of other samples was obtained by comparing their peak areas with that of the reference. The textural properties and specific surface areas were measured using a Micromeritics ASAP 2460 automated surface area and porosity analyzer. Nitrogen adsorption-desorption was conducted at -196°C after degassing the samples at 350°C for 8 h. The total surface area was calculated using the Brunauer-Emmett-Teller (BET) method, while the total pore volume was determined at P/P 0 = 0.99. The micropore surface area and pore volume were obtained by the t-plot method. Scanning electron microscopy (SEM) images were obtained using a Hitachi S-4800 field-emission scanning electron microscope operated at an accelerating voltage of 2 kV. Fourier transform infrared (FT-IR) spectra were recorded on a Nicolet iS5 spectrometer (America) to evaluate the Brønsted acid strength of the catalysts. Each sample (1 mg) was thoroughly mixed with KBr (1000 mg), and the pellet was prepared under a pressure of 50 bar. The acidity of the catalysts was estimated based on the intensity of characteristic absorption bands. Thermal stability was examined using a Mettler TGA/100SF thermogravimetric analyzer. The TGA analysis was conducted in the temperature range of 50 ~ 750°C with a heating rate of 10°C/min. Pyridine-adsorbed infrared (Py-IR) spectroscopy was performed on a Tensor FT-IR spectrometer to analyze the acid amount and acid type of the hierarchical H-ZSM-5 zeolite. Before measurement, the in-situ cell was evacuated at 350°C for 2 h to remove adsorbed species. The background spectrum was recorded at room temperature, and Py-IR spectra were collected at 150, 250, and 350°C. 3 Results and Discussion 3.1 Characterization of the samples The XRD patterns of the catalyst samples are shown in Fig. 2 a. All zeolite catalysts exhibit the characteristic diffraction peaks of H-ZSM-5. The samples SH-5, H-5, and Meso-5 show relatively high crystallinity, while N-5 exhibits noticeably lower crystallinity, indicating that the addition of seed crystals promotes the crystallization of zeolites. Moreover, pronounced peak broadening is observed for Meso-5, indicating smaller crystallite sizes of the zeolite. The SEM images of the samples are shown in Fig. 2 c-f. It can be observed that the H-5 particles have an average size of about 1 µm and exhibit a typical cubic morphology. In contrast, Meso-5, SH-5, and N-5 display relatively regular spherical shapes. Compared with H-5, the particle size of Meso-5 is smaller (approximately 0.5 µm), which is consistent with the XRD results. Moreover, the Meso-5 particles are smaller and show a more uniform size distribution than those of H-5. The morphology of SH-5 is similar to that of Meso-5, but the particle size is slightly larger. These observations indicate that the use of different seeds can significantly affect the morphology of the resulting zeolites. Smaller catalyst particle sizes generally enhance catalytic activity by shortening the diffusion path length of reactant molecules, thereby reducing internal mass-transfer resistance. Improved accessibility of active sites promotes faster reaction kinetics and higher overall conversion. As shown in Fig. 2 b, the Py-IR spectrum of Meso-5 indicates that the concentrations of Brønsted acid sites, Lewis acid sites, and their synergistic combined acidity decrease with increasing temperature. Since the isomerization of oleic acid occurs in the temperature range of 260–290°C, the acidity data obtained at 250°C are considered the most relevant for evaluating catalytic performance. At this temperature, the Brønsted acid concentration of Meso-5 is 112.2 µmol/g, while the Lewis acid concentration is 37.1 µmol/g, giving a B/L ratio of 3.0. The isomerization of oleic acid proceeds via a carbocation rearrangement mechanism, in which Brønsted acid sites provide protons to generate carbocations. Simultaneously, Lewis acid sites act synergistically, facilitating the formation of carbocations and thereby enhancing the overall reaction rate. Figure 3 a and 3 b present the N 2 adsorption-desorption isotherms and pore size distribution curves of the H-5 and Meso-5 samples. The Meso-5 sample exhibits a typical type IV isotherm with a pronounced hysteresis loop, indicating the presence of mesopores. In contrast, the isotherm of H-5 corresponds to a type I profile without a hysteresis loop, characteristic of a microporous structure. The average pore diameter of H-5 is 2.9 nm, suggesting that it predominantly consists of micropores with only a minor fraction of mesopores, which explains its type I adsorption behavior. In comparison, the average pore diameter of Meso-5 reaches 5.7 nm, approximately twice that of H-5, confirming the successful introduction of mesoporosity and the formation of a hierarchical pore structure. Figure 3 (d) illustrates the textural properties of the Meso-5 and H-5 samples. Compared with H-5, the Meso-5 sample exhibits a markedly higher degree of mesoporosity. Although both samples possess comparable total surface areas, the mesoporous surface area of Meso-5 reaches 110.1 m 2 /g, substantially exceeding the 43.6 m 2 /g observed for H-5. A similar trend is observed in the pore volume data, where Meso-5 displays a considerably larger mesoporous pore volume than H-5. These results are consistent with the morphological features observed in the SEM images, confirming the enhanced textural development in Meso-5. Therefore, S-1 proves to be a more effective seed for the synthesis of hierarchical H-ZSM-5 zeolites. Mesopores enhance the diffusion of reactant molecules within the catalyst, thereby minimizing internal mass-transfer limitations, while micropores offer a high density of active sites, effectively promoting the isomerization reaction. To further examine the surface chemical characteristics of the zeolite catalysts, FT-IR spectra of all samples were recorded, as shown in Fig. 3 (c). All zeolites exhibited a dominant absorption band at 1086.7 cm − 1 , which corresponds to the asymmetric stretching vibration of Si-O-Si, a typical feature of silica-based frameworks. The band observed at 1226.3 cm − 1 is also associated with Si-O-Si stretching vibrations. The absorption band at 1632.2 cm − 1 is assigned to the deformation vibration of hydroxyl groups associated with surface water on the zeolite. The absorption peak at 3442.1 cm − 1 is attributed to Brønsted acidic hydroxyl groups, and its intensity can be used to estimate the relative strength of Brønsted acidity. It is noteworthy that the Meso-5 sample displays a stronger Brønsted acidity compared with the other zeolites, suggesting the presence of a higher concentration of protonic sites. In addition, a weak band at 801.8 cm − 1 arises from the symmetric stretching vibration of Si-O-Si, while the strong band observed at 584.6 cm − 1 is assigned to Si-O-Si bending vibrations. During the isomerization of oleic acid, Brønsted acids supply protons that facilitate the formation of carbocation intermediates, thereby governing the protonation and rearrangement steps, whereas Lewis acids enhance adsorption and activation, promoting the accessibility of reactant molecules to the reaction channels. The simultaneous presence of both acid types synergistically accelerates the isomerization rate and improves both selectivity and overall yield. Figure 3 (e) shows the thermogravimetric (TG) curves of all H-ZSM-5 zeolite catalysts, revealing a single-stage weight loss. The slight mass loss observed below 250°C corresponds to the removal of physically adsorbed water located on the external surface as well as within the micropores and mesopores of the zeolites. This behavior is typical of low-temperature dehydration processes. Upon further heating, no additional weight loss is observed, suggesting that the structure-directing agents were completely decomposed into CO 2 and NH 3 during the calcination step and that no framework aluminum leaching occurred. The minor mass variation is mainly associated with storage conditions and has a negligible influence on the zeolite framework or its active sites. The excellent thermal stability of the catalysts confirms the effectiveness of the calcination procedure and ensures that the zeolite structure remains intact under high-temperature conditions relevant to oleic acid isomerization. 3.2 Catalytic Activity To evaluate the catalytic activity of Meso-5 in oleic acid isomerization, key reaction parameters such as temperature, reaction time, catalyst dosage, and calcination temperature were systematically optimized. The effect of reaction temperature was assessed at a fixed reaction time of 6 h. As shown in Fig. 4 (a), increasing the temperature from 250 to 290°C enhanced oleic acid conversion from 63.9% to 93.3%. The selectivity toward isostearic acid reached a maximum of 87.9% at 260°C. Further temperature increase led to a marked decline in selectivity, primarily due to intensified decarboxylation. Correspondingly, Fig. 4 (b) shows that the acid value of the products decreased from 179.3 to 125.4 mg KOH/g as the temperature rose from 250 to 290°C, mirroring the trend in selectivity. The highest yield of isostearic acid (72.5%) was obtained at 260°C. The influence of reaction time on the isomerization of oleic acid over Meso-5 was investigated at 260°C. As shown in Fig. 4 (c) and (d), the conversion rapidly increased to 81.3% within the first 4 h and then stabilized at 82.1%. The selectivity toward isostearic acid remained nearly constant at approximately 86.2% throughout the reaction. Accordingly, the optimal reaction time was determined to be 4 h, yielding 71.1% isostearic acid with an acid value of 172.8 mg KOH/g. The effect of catalyst loading on the isomerization of oleic acid over Meso-5 was investigated at 260°C for 4 h. As shown in Fig. 4 (e) and (f), considering the oleic acid conversion, the selectivity toward isostearic acid, and the acid value of the products, the optimal catalyst loading was identified as 8 wt.%. Under these conditions, the yield of isostearic acid reached 71.1%, and the corresponding acid value was 173.8 mg KOH/g. Therefore, the optimal reaction parameters for the isomerization of oleic acid over Meso-5 were established as a temperature of 260°C, a reaction time of 4 h, and a catalyst loading of 8 wt.%. The calcination temperature of NH 4 -ZSM-5 exerts a significant influence on the catalytic performance. As illustrated in Fig. 5 (a) and (b), the Meso-5 catalyst maintained stable activity upon calcination above 400°C, yielding isostearic acid at approximately 74.5%, with the crude product exhibiting an acid value of 172.7 mg KOH/g. In contrast, when the calcination temperature is reduced to 350°C, the catalytic performance decreases markedly, and the yield drops to 63.6%. Figure 5 (c) and (d) show that Meso-5 exhibits the highest catalytic activity, achieving an isostearic acid yield of 73.6% with an acid value of 172.3 mg KOH/g. In contrast, H-5 displays a lower yield of 59.3% and an acid value of 157.6 mg KOH/g. The crude isostearic acid was subsequently purified by low-temperature recrystallization, affording a high-purity product with a purity of 83.4% and an acid value of 186.7 mg KOH/g, which meets commercial standards (Fig. 5 (e)). As illustrated in Fig. 5 (f), Meso-5 retains high performance over five consecutive cycles, maintaining a selectivity of 82.1% and a yield of 55.6%, only 3.7% lower than the initial yield of H-5. Synergistic interactions between Brønsted and Lewis acid sites create stable, high-activity centers that substantially facilitate the isomerization reaction. Meanwhile, the hierarchical pore structure facilitates the diffusion of oleic acid molecules and their isomerized intermediates, minimizes internal diffusion limitations, and improves accessibility to active sites, thereby accelerating the reaction and enhancing both selectivity and product yield. 4 Conclusions H-ZSM-5 zeolites synthesized with different seed types exhibited distinct pore structures. During the isomerization of oleic acid, the commercial H-ZSM-5 zeolite, with an average pore size of only 2.9 nm, hindered the diffusion of oleic acid molecules and therefore showed relatively low catalytic activity. In contrast, the H-ZSM-5 synthesized using Silicalite-1 as a seed exhibited a hierarchical pore structure with an average pore diameter of 5.7 nm, which significantly enhanced molecular diffusion and catalytic performance. The calcination temperature of NH 4 -ZSM-5 exhibited a pronounced influence on catalytic activity, with 400°C identified as the optimal temperature that balances catalytic performance and energy efficiency. Meso-5 efficiently catalyzed the isomerization of oleic acid due to the abundance of Brønsted and Lewis acid sites, whose synergistic interactions markedly promoted the formation of branched-chain products. Meso-5 showed excellent catalytic performance in the isomerization of oleic acid, affording 87.3% selectivity and a 71.1% yield in the initial run. Notably, the catalyst retained robust activity after five reuse cycles, maintaining 82.1% selectivity and a 55.6% yield. Evidently, the hierarchical pore structure greatly enhances the diffusion of oleic acid molecules and their isomerized intermediates, thereby reducing internal diffusion resistance and improving the overall catalytic performance. After low-temperature recrystallization of the crude product, high-purity isostearic acid was obtained with a purity of 83.4% and an acid value of 186.7 mg KOH/g. These results provide a solid foundation for further catalyst optimization and the scale-up of isostearic acid production toward industrial application. Abbreviations S-1: Silicalite-1 seed NH 4 -ZSM-5: ZSM-5 zeolite with ammonium ions as the balanced cation H-ZSM-5: ZSM-5 zeolite with hydrogen ions as the balanced cation Meso-5: hierarchical-pore H-ZSM-5 XRD: X-ray diffraction FT-IR: Fourier transform infrared spectra Py-FTIR: Pyridine adsorption infrared spectroscopy TGA: Thermogravimetric analysis BET: Brunauer–Emmett–Teller SEM: Scanning electron microscopy GC: Gas Chromatography SDA: structure-directing agent TEAOH: tetraethylammonium hydroxide TPAOH: tetrapropylammonium hydroxide TPABr: tetrapropylammonium bromide KF: potassium fluoride CTAB: cetyltrimethylammonium bromide TEOS : tetraethyl orthosilicate Ni/C: Ni-based hydrogenation catalyst Declarations Ethics and Consent to Participate Not applicable Consent for Publication All authors have read and agreed to the published version of the manuscript. Competing Interest The authors declare no competing interests. Author Contribution Xincheng Li: Writing – original draft, Investigation, Data curation, Formal analysis. Pengpeng Huang: Investigation. Mingming Fan: Writing – review & editing, Supervision, Resources, Project administration. Pingbo Zhang: Writing – review & editing, Resources, Project administration, Funding acquisition. Funding This work was supported by the National Natural Science Foundation of China (No. 21978112) and MOE & SAFEA for the 111 Project (B13025). Availability of data and materials The data and materials supporting the findings of this study are available from the corresponding authors upon reasonable request. Acknowledgments This research was financially supported by the National Natural Science Foundation of China (No. 21978112) and the 111 Project of MOE & SAFEA (B13025), for which the authors are sincerely grateful. References Kerstens D, Van Praet S, Verhoeven L, et al (2022) Branched Fatty Acids: The Potential of Zeolite Catalysis. 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RSC Adv 6:76642–76651. https://doi.org/10.1039/C6RA14753D Jiang Y, Wang Y, Zhao W, et al (2016) Effect of (Si+Al)/CTAB ratio on crystal size of mesoporous ZSM-5 structure over methanol-to-olefin reactions. Journal of the Taiwan Institute of Chemical Engineers 61:234–240. https://doi.org/10.1016/j.jtice.2015.12.017 Shao X, Zhang Y, Li J, et al (2021) Seed-sol-assisted construction of a coffin-shaped multilamellar ZSM-5 single crystal using CTAB. Chem Commun 57:10624–10627. https://doi.org/10.1039/D1CC04620A Scheme 1 Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files GraphicalAbstract.png Graphical Abstract A tandem catalytic route combining ZSM-5-driven isomerization with Ni/C-catalyzed hydrogenation enabled the efficient conversion of oleic acid to isostearic acid. The hierarchical H-ZSM-5 structure enhanced branched-chain formation, ensuring high selectivity and yield toward the desired product. Scheme1.png Scheme 1. Schematic illustration of oleic acid isomerization over hierarchical H-ZSM-5 and hydrogenation of the isomers. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 23 Dec, 2025 Reviews received at journal 17 Dec, 2025 Reviews received at journal 14 Dec, 2025 Reviewers agreed at journal 11 Dec, 2025 Reviewers agreed at journal 09 Dec, 2025 Reviewers invited by journal 09 Dec, 2025 Editor assigned by journal 04 Dec, 2025 Submission checks completed at journal 04 Dec, 2025 First submitted to journal 04 Dec, 2025 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. 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1","display":"","copyAsset":false,"role":"figure","size":251896,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the synthesis routes for different H-ZSM-5 zeolites (H-5, SH-5, N-5, and Meso-5).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/b4e94233a1835face99232ea.png"},{"id":98137578,"identity":"31d56d51-f298-4584-819e-079e1d1750bc","added_by":"auto","created_at":"2025-12-13 17:19:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":662098,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of prepared catalysts; (b) Py-FTIR spectra of Meso-5; SEM image of (c) H-5, (d) Meso-5, (e) SH-5, and (f) N-5.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/ba8b2e0507e37720a39f87ca.png"},{"id":98430628,"identity":"ace02883-6f9c-4b10-b40f-5bf0dbfc0fad","added_by":"auto","created_at":"2025-12-17 16:45:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":719665,"visible":true,"origin":"","legend":"\u003cp\u003e(a, b) N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms and pore size distribution curves of H-5 and Meso-5, respectively; (c) FT-IR spectra of the H-5, Meso-5, SH-5, and N-5 zeolite samples; (d) Comparison of micropore, mesopore, and total textural properties of H-5 and Meso-5 zeolites; (e) TG profiles of used zeolites.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/7d1b647728914895ae2a5e8a.png"},{"id":98137583,"identity":"20898e4a-5478-4022-895b-7bdec179b56c","added_by":"auto","created_at":"2025-12-13 17:19:16","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":198836,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of reaction parameters on oleic acid isomerization over H-ZSM-5 catalysts: (a, b) reaction temperature; (c, d) reaction time; (e, f) catalyst amount. Conversion, selectivity, yield, and acid value are shown.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/c3d1c20f67d12342ff619269.png"},{"id":98429835,"identity":"096eb2bf-8695-4d62-8d80-2b9917185bd4","added_by":"auto","created_at":"2025-12-17 16:44:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":205441,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Effect of calcination temperature of NH\u003csub\u003e4\u003c/sub\u003e-ZSM-5 on conversion and selectivity; (b) Effect of calcination temperature on yield and acid value; (c) The conversion and selectivity of the catalyst used; (d) The yield of the catalyst used and acid value of the product; (e) Purity and acid value of products after purification over different zeolite catalysts; (f) Conversion and selectivity of Meso–5 during recycling tests.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/aa5fc396400346b41fbc32b1.png"},{"id":98622998,"identity":"c3b29c93-6228-4f18-b952-35c17f99c90a","added_by":"auto","created_at":"2025-12-19 17:03:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2356420,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/5341902a-952a-442b-a189-cf6d1cc9db0f.pdf"},{"id":98137575,"identity":"b025860d-c4b7-44fb-bee2-878abeb00243","added_by":"auto","created_at":"2025-12-13 17:19:16","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":214744,"visible":true,"origin":"","legend":"\u003cp\u003eGraphical Abstract\u003c/p\u003e\n\u003cp\u003eA tandem catalytic route combining ZSM-5-driven isomerization with Ni/C-catalyzed hydrogenation enabled the efficient conversion of oleic acid to isostearic acid. The hierarchical H-ZSM-5 structure enhanced branched-chain formation, ensuring high selectivity and yield toward the desired product.\u003c/p\u003e","description":"","filename":"GraphicalAbstract.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/ba65e0b7411d9f767468be7e.png"},{"id":98430660,"identity":"27d68b19-1785-4d7d-9ff4-40b358fa9ffa","added_by":"auto","created_at":"2025-12-17 16:45:59","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":84546,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1.\u003c/strong\u003e Schematic illustration of oleic acid isomerization over hierarchical H-ZSM-5 and hydrogenation of the isomers.\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-8280043/v1/7532573f0912b6760b86a71a.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Seed-Assisted Hierarchical H-ZSM-5: Overcoming Diffusion Barriers for Efficient Recyclable Oleic Acid Isomerization to Commercial Isostearic Acid","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eIsostearic acid is a mixture of saturated fatty acid isomers of stearic acid featuring unique branched structures[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The presence of methyl or ethyl branches at various positions along the carbon chain endows isostearic acid with multiple distinctive properties[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. It has a relatively low melting point and is usually liquid at room temperature, exhibiting excellent cold-flow performance[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Moreover, as a saturated fatty acid, isostearic acid possesses outstanding oxidative stability[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These characteristics make it widely applicable in biomedical applications, cosmetics, lubricants, metalworking fluids, and coatings[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe isomerization of oleic acid is typically catalyzed by Br\u0026oslash;nsted acids, making zeolites well-suited for this type of reaction[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. H-ZSM-5 zeolite, a high-silica zeolite with a three-dimensional 10-membered ring channel structure, exhibits high hydrothermal stability and strong acidity, and has been widely applied in catalysis, including toluene disproportionation and xylene isomerization[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. H-ZSM-5 is generally synthesized using quaternary ammonium salts as structure-directing agents (SDAs), such as tetrapropylammonium hydroxide (TPAOH) and tetraethylammonium hydroxide (TEAOH). When a single SDA is used, the resulting H-ZSM-5 crystals tend to be relatively large, ranging from several hundred nanometers to several hundred micrometers[\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. At relatively low temperatures and high pressures, ZSM-5 can catalyze the liquid-phase isomerization of xylene with remarkable selectivity, providing insights for oleic acid isomerization[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Due to its larger molecular size, oleic acid encounters steric limitations in the narrow H-ZSM-5 channels, which reduces the contact between the molecules and the active sites, lowers molecular diffusion rates, and ultimately limits the catalytic activity[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTo overcome diffusion limitations in zeolite-catalyzed reactions, hierarchical porous zeolites have been increasingly employed in recent years[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. There are two main strategies for preparing hierarchical zeolites. The first involves integrating micropores and mesopores, typically achieved by introducing mesopore-directing agents during synthesis or via post-synthetic treatments[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The second strategy is to synthesize small zeolite crystals, which tend to aggregate and generate abundant mesopores[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The seed-assisted synthesis method is an effective approach for producing such mesoporous H-ZSM-5, as it can accelerate crystallization and reduce the amount of template required[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Mesoporous H-ZSM-5 can also be synthesized without SDAs by adding seeds with an average particle size of approximately 70 nm[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Among the factors affecting zeolite synthesis, crystallization temperature and time have the most significant impact, followed by alkalinity and seed particle size[\u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Even without SDAs, precise control of these parameters allows the formation of uniform, small zeolite crystals[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Zhang et al. developed a salt-assisted seed-induced method to synthesize nanosized ZSM-5 using S-1 as seeds[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. In SDA-assisted syntheses with tetrapropylammonium bromide (TPABr), the addition of potassium fluoride (KF) reduces crystallization time and SDA usage while broadening the Si/Al ratio range[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. By controlling the amount of KF, the mesopore volume can be precisely tuned. Using S-1 as seeds, Chen et al. synthesized mesoporous ZSM-5 with cetyltrimethylammonium bromide (CTAB) and TPAOH as SDAs[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The addition of CTAB suppresses secondary crystal growth and promotes mesopore formation, and increasing the amount of S-1 seeds results in smaller primary crystals[\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn this study, hierarchical H-ZSM-5 was synthesized using S-1 as seeds and TPAOH as SDA. The effect of different seed types on the morphology of the samples was investigated. The structure of the hierarchical H-ZSM-5 was characterized by XRD, SEM, nitrogen adsorption\u0026ndash;desorption analysis, FT-IR, TGA, and Py-FTIR. Furthermore, the synthesized hierarchical H-ZSM-5 was employed for the isomerization of oleic acid to evaluate its catalytic performance.\u003c/p\u003e"},{"header":"2 Experimental Section","content":"\u003cdiv id=\"Sec3\"\u003e\n \u003ch2\u003e2.1 Materials\u003c/h2\u003e\n \u003cp\u003eOleic acid (\u0026ge;\u0026thinsp;90%, Aladdin, acid value: 192.3 mg KOH/g ), fumed silica (SiO\u003csub\u003e2\u003c/sub\u003e, Sigma-Aldrich), TPAOH (25 wt.% in water), anhydrous ethanol (AR), tetraethyl orthosilicate (TEOS, AR), sodium aluminate (NaAlO\u003csub\u003e2\u003c/sub\u003e, AR), sodium hydroxide (NaOH, AR), ammonium chloride (NH\u003csub\u003e4\u003c/sub\u003eCl, AR), and H-ZSM-5 zeolite (Macklin) were used as received. Deionized water was used throughout the experiments. All reagents were of analytical grade and employed without further purification.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\"\u003e\n \u003ch2\u003e2.2 Synthesis of the Zeolite\u003c/h2\u003e\n \u003cp\u003eIn a typical synthesis, 32.51 g of TPAOH, 36.80 g of anhydrous ethanol, and 47.61 g of deionized water were added to a beaker and stirred for 30 min to obtain a homogeneous solution. Subsequently, 41.68 g of TEOS was slowly added dropwise into the solution under continuous stirring. The mixture was further stirred for 3 h to allow aging. The aged gel was then transferred into a Teflon-lined autoclave and crystallized hydrothermally at 140\u0026deg;C for 64 h. The resulting product was centrifuged, washed with deionized water, and dried. Finally, the dried solid was calcined at 550\u0026deg;C for 6 h in air to remove the organic SDA, yielding the S-1 seed crystals.\u003c/p\u003e\n \u003cp\u003eIn the synthesis of hierarchical H-ZSM-5 zeolite, S-1 was used as the seed, fumed silica as the silica source, and sodium aluminate (NaAlO\u003csub\u003e2\u003c/sub\u003e) as the aluminum source. In a beaker, 58.70 g of deionized water was first added, followed by 1.64 g of NaAlO\u003csub\u003e2\u003c/sub\u003e, 0.48 g of NaOH, 8.13 g of TPAOH, and 2 g of S-1 seed under continuous stirring for 3 h to form mixture A. Then, 12 g of fumed silica was gradually added into mixture A under stirring, and the resulting suspension was aged for 4 h to obtain mixture B. Mixture B was transferred into a Teflon-lined autoclave and crystallized hydrothermally at 180\u0026deg;C for 48 h. The resulting material was collected by filtration, washed with deionized water until neutral, and dried overnight at 70\u0026deg;C. The dried sample was then calcined at 550\u0026deg;C for 4 h in air to remove the template. Ion exchange of the calcined sample with 1 M aqueous NH\u003csub\u003e4\u003c/sub\u003eCl solution yielded NH\u003csub\u003e4\u003c/sub\u003e-ZSM-5, which was subsequently calcined at 400\u0026deg;C for 4 h in air with a heating rate of 3\u0026deg;C/min to obtain the hierarchical H-ZSM-5, denoted as Meso-5.\u003c/p\u003e\n \u003cp\u003eFor comparison, the commercially available H-ZSM-5 zeolite was denoted as H-5. The H-ZSM-5 zeolite synthesized using the commercial H-5 as the seed was denoted as SH-5, while the H-ZSM-5 zeolite synthesized without any seed was denoted as N-5. A schematic illustration of the synthesis process is shown in Fig.\u0026nbsp;1.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\"\u003e\n \u003ch2\u003e2.3 Experimental Methods and Data Evaluation\u003c/h2\u003e\n \u003cp\u003eThe isomerization of oleic acid was carried out in a high-pressure stainless-steel autoclave. In a typical experiment, 60 g of oleic acid, 4.8 g of zeolite catalyst, and 2.4 g of deionized water were added to the reactor. The air inside the autoclave was purged with nitrogen five times, and the final nitrogen pressure was adjusted to 0.5 MPa. The mixture was stirred at 500 rpm and heated to 250\u0026thinsp;~\u0026thinsp;290\u0026deg;C, maintaining the reaction for 6 h. After completion, the reactor was cooled to room temperature, residual gases were vented, and the reaction mixture was filtered. The filtrate contained the isomers of oleic acid, while the solid residue consisted of the zeolite catalyst.\u003c/p\u003e\n \u003cp\u003eThe hydrogenation of the isomers of oleic acid was performed in a high-pressure stainless-steel autoclave. A certain amount of isomers of oleic acid and Ni-based hydrogenation catalyst (Ni/C) were added to the reactor. The air inside the autoclave was purged with nitrogen five times, followed by purging with hydrogen five times. Finally, the isomers of oleic acid were hydrogenated under specific conditions (Reaction condition: 40 g of the isomers of oleic acid, 0.4 g Ni/C, 220\u0026deg;C, 4 MPa H\u003csub\u003e2\u003c/sub\u003e, 4 h). After the reaction was completed, the autoclave was cooled to room temperature, and the residual gas was released. The reaction mixture was then filtered, and the filtrate was collected as the crude isostearic acid. The crude product was dissolved in an appropriate amount of n-hexane and subjected to low-temperature recrystallization. The filtrate was subsequently distilled under reduced pressure to remove the solvent, yielding the purified isostearic acid. Scheme 1 shows the reaction process for producing isostearic acid from oleic acid. Oleic acid is first isomerized over hierarchical H-ZSM-5 to form isomers of oleic acid, which is then hydrogenated at C\u0026thinsp;=\u0026thinsp;C to yield isostearic acid.\u003c/p\u003e\n \u003cp\u003eThe reaction products were first converted to their methyl esters, and the composition was quantified by gas chromatography (GC). The GC analysis was performed with an initial oven temperature of 150\u0026deg;C, ramped at 10\u0026deg;C\u0026middot;min\u003csup\u003e-1\u003c/sup\u003e to 270\u0026deg;C, and held at 270\u0026deg;C for 7 min. The acid values of both the crude and purified isostearic acid products were determined using the ethanolic hot method. The conversion of key components and the selectivity of the target product were calculated according to the corresponding equations.\u003c/p\u003e\n \u003cp\u003eThe conversion of key component A, the selectivity of the target product, and the yield of the target product were calculated using the following equations:\u003c/p\u003e\n \u003cdiv id=\"Equc\"\u003e\u003cimg 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\" width=\"553\" height=\"160\"\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\"\u003e\n \u003ch2\u003e2.4 Catalyst characterizations\u003c/h2\u003e\n \u003cp\u003eThe X-ray diffraction (XRD) patterns of the samples were recorded on a Bruker D8 Advance diffractometer (Germany) at a scanning rate of 4 \u0026deg;/min over a 2\u0026theta; range of 5\u0026deg;-50\u0026deg;. The relative crystallinity was calculated by integrating the peak area within the range of 22\u0026deg;~25\u0026deg;, using the sample with the largest peak area as the reference (defined as 100%). The relative crystallinity of other samples was obtained by comparing their peak areas with that of the reference. The textural properties and specific surface areas were measured using a Micromeritics ASAP 2460 automated surface area and porosity analyzer. Nitrogen adsorption-desorption was conducted at -196\u0026deg;C after degassing the samples at 350\u0026deg;C for 8 h. The total surface area was calculated using the Brunauer-Emmett-Teller (BET) method, while the total pore volume was determined at P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.99. The micropore surface area and pore volume were obtained by the t-plot method. Scanning electron microscopy (SEM) images were obtained using a Hitachi S-4800 field-emission scanning electron microscope operated at an accelerating voltage of 2 kV. Fourier transform infrared (FT-IR) spectra were recorded on a Nicolet iS5 spectrometer (America) to evaluate the Br\u0026oslash;nsted acid strength of the catalysts. Each sample (1 mg) was thoroughly mixed with KBr (1000 mg), and the pellet was prepared under a pressure of 50 bar. The acidity of the catalysts was estimated based on the intensity of characteristic absorption bands. Thermal stability was examined using a Mettler TGA/100SF thermogravimetric analyzer. The TGA analysis was conducted in the temperature range of 50\u0026thinsp;~\u0026thinsp;750\u0026deg;C with a heating rate of 10\u0026deg;C/min. Pyridine-adsorbed infrared (Py-IR) spectroscopy was performed on a Tensor FT-IR spectrometer to analyze the acid amount and acid type of the hierarchical H-ZSM-5 zeolite. Before measurement, the in-situ cell was evacuated at 350\u0026deg;C for 2 h to remove adsorbed species. The background spectrum was recorded at room temperature, and Py-IR spectra were collected at 150, 250, and 350\u0026deg;C.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Characterization of the samples\u003c/h2\u003e\u003cp\u003eThe XRD patterns of the catalyst samples are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. All zeolite catalysts exhibit the characteristic diffraction peaks of H-ZSM-5. The samples SH-5, H-5, and Meso-5 show relatively high crystallinity, while N-5 exhibits noticeably lower crystallinity, indicating that the addition of seed crystals promotes the crystallization of zeolites. Moreover, pronounced peak broadening is observed for Meso-5, indicating smaller crystallite sizes of the zeolite.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe SEM images of the samples are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec-f. It can be observed that the H-5 particles have an average size of about 1 \u0026micro;m and exhibit a typical cubic morphology. In contrast, Meso-5, SH-5, and N-5 display relatively regular spherical shapes. Compared with H-5, the particle size of Meso-5 is smaller (approximately 0.5 \u0026micro;m), which is consistent with the XRD results. Moreover, the Meso-5 particles are smaller and show a more uniform size distribution than those of H-5. The morphology of SH-5 is similar to that of Meso-5, but the particle size is slightly larger. These observations indicate that the use of different seeds can significantly affect the morphology of the resulting zeolites. Smaller catalyst particle sizes generally enhance catalytic activity by shortening the diffusion path length of reactant molecules, thereby reducing internal mass-transfer resistance. Improved accessibility of active sites promotes faster reaction kinetics and higher overall conversion.\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb, the Py-IR spectrum of Meso-5 indicates that the concentrations of Br\u0026oslash;nsted acid sites, Lewis acid sites, and their synergistic combined acidity decrease with increasing temperature. Since the isomerization of oleic acid occurs in the temperature range of 260\u0026ndash;290\u0026deg;C, the acidity data obtained at 250\u0026deg;C are considered the most relevant for evaluating catalytic performance. At this temperature, the Br\u0026oslash;nsted acid concentration of Meso-5 is 112.2 \u0026micro;mol/g, while the Lewis acid concentration is 37.1 \u0026micro;mol/g, giving a B/L ratio of 3.0. The isomerization of oleic acid proceeds via a carbocation rearrangement mechanism, in which Br\u0026oslash;nsted acid sites provide protons to generate carbocations. Simultaneously, Lewis acid sites act synergistically, facilitating the formation of carbocations and thereby enhancing the overall reaction rate.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb present the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms and pore size distribution curves of the H-5 and Meso-5 samples. The Meso-5 sample exhibits a typical type IV isotherm with a pronounced hysteresis loop, indicating the presence of mesopores. In contrast, the isotherm of H-5 corresponds to a type I profile without a hysteresis loop, characteristic of a microporous structure. The average pore diameter of H-5 is 2.9 nm, suggesting that it predominantly consists of micropores with only a minor fraction of mesopores, which explains its type I adsorption behavior. In comparison, the average pore diameter of Meso-5 reaches 5.7 nm, approximately twice that of H-5, confirming the successful introduction of mesoporosity and the formation of a hierarchical pore structure.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d) illustrates the textural properties of the Meso-5 and H-5 samples. Compared with H-5, the Meso-5 sample exhibits a markedly higher degree of mesoporosity. Although both samples possess comparable total surface areas, the mesoporous surface area of Meso-5 reaches 110.1 m\u003csup\u003e2\u003c/sup\u003e/g, substantially exceeding the 43.6 m\u003csup\u003e2\u003c/sup\u003e/g observed for H-5. A similar trend is observed in the pore volume data, where Meso-5 displays a considerably larger mesoporous pore volume than H-5. These results are consistent with the morphological features observed in the SEM images, confirming the enhanced textural development in Meso-5. Therefore, S-1 proves to be a more effective seed for the synthesis of hierarchical H-ZSM-5 zeolites. Mesopores enhance the diffusion of reactant molecules within the catalyst, thereby minimizing internal mass-transfer limitations, while micropores offer a high density of active sites, effectively promoting the isomerization reaction.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo further examine the surface chemical characteristics of the zeolite catalysts, FT-IR spectra of all samples were recorded, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c). All zeolites exhibited a dominant absorption band at 1086.7 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which corresponds to the asymmetric stretching vibration of Si-O-Si, a typical feature of silica-based frameworks. The band observed at 1226.3 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is also associated with Si-O-Si stretching vibrations. The absorption band at 1632.2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to the deformation vibration of hydroxyl groups associated with surface water on the zeolite. The absorption peak at 3442.1 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to Br\u0026oslash;nsted acidic hydroxyl groups, and its intensity can be used to estimate the relative strength of Br\u0026oslash;nsted acidity. It is noteworthy that the Meso-5 sample displays a stronger Br\u0026oslash;nsted acidity compared with the other zeolites, suggesting the presence of a higher concentration of protonic sites. In addition, a weak band at 801.8 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e arises from the symmetric stretching vibration of Si-O-Si, while the strong band observed at 584.6 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to Si-O-Si bending vibrations. During the isomerization of oleic acid, Br\u0026oslash;nsted acids supply protons that facilitate the formation of carbocation intermediates, thereby governing the protonation and rearrangement steps, whereas Lewis acids enhance adsorption and activation, promoting the accessibility of reactant molecules to the reaction channels. The simultaneous presence of both acid types synergistically accelerates the isomerization rate and improves both selectivity and overall yield.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(e) shows the thermogravimetric (TG) curves of all H-ZSM-5 zeolite catalysts, revealing a single-stage weight loss. The slight mass loss observed below 250\u0026deg;C corresponds to the removal of physically adsorbed water located on the external surface as well as within the micropores and mesopores of the zeolites. This behavior is typical of low-temperature dehydration processes. Upon further heating, no additional weight loss is observed, suggesting that the structure-directing agents were completely decomposed into CO\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e3\u003c/sub\u003e during the calcination step and that no framework aluminum leaching occurred. The minor mass variation is mainly associated with storage conditions and has a negligible influence on the zeolite framework or its active sites. The excellent thermal stability of the catalysts confirms the effectiveness of the calcination procedure and ensures that the zeolite structure remains intact under high-temperature conditions relevant to oleic acid isomerization.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Catalytic Activity\u003c/h2\u003e\u003cp\u003eTo evaluate the catalytic activity of Meso-5 in oleic acid isomerization, key reaction parameters such as temperature, reaction time, catalyst dosage, and calcination temperature were systematically optimized. The effect of reaction temperature was assessed at a fixed reaction time of 6 h. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a), increasing the temperature from 250 to 290\u0026deg;C enhanced oleic acid conversion from 63.9% to 93.3%. The selectivity toward isostearic acid reached a maximum of 87.9% at 260\u0026deg;C. Further temperature increase led to a marked decline in selectivity, primarily due to intensified decarboxylation. Correspondingly, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b) shows that the acid value of the products decreased from 179.3 to 125.4 mg KOH/g as the temperature rose from 250 to 290\u0026deg;C, mirroring the trend in selectivity. The highest yield of isostearic acid (72.5%) was obtained at 260\u0026deg;C.\u003c/p\u003e\u003cp\u003eThe influence of reaction time on the isomerization of oleic acid over Meso-5 was investigated at 260\u0026deg;C. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(c) and (d), the conversion rapidly increased to 81.3% within the first 4 h and then stabilized at 82.1%. The selectivity toward isostearic acid remained nearly constant at approximately 86.2% throughout the reaction. Accordingly, the optimal reaction time was determined to be 4 h, yielding 71.1% isostearic acid with an acid value of 172.8 mg KOH/g.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe effect of catalyst loading on the isomerization of oleic acid over Meso-5 was investigated at 260\u0026deg;C for 4 h. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(e) and (f), considering the oleic acid conversion, the selectivity toward isostearic acid, and the acid value of the products, the optimal catalyst loading was identified as 8 wt.%. Under these conditions, the yield of isostearic acid reached 71.1%, and the corresponding acid value was 173.8 mg KOH/g. Therefore, the optimal reaction parameters for the isomerization of oleic acid over Meso-5 were established as a temperature of 260\u0026deg;C, a reaction time of 4 h, and a catalyst loading of 8 wt.%.\u003c/p\u003e\u003cp\u003eThe calcination temperature of NH\u003csub\u003e4\u003c/sub\u003e-ZSM-5 exerts a significant influence on the catalytic performance. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a) and (b), the Meso-5 catalyst maintained stable activity upon calcination above 400\u0026deg;C, yielding isostearic acid at approximately 74.5%, with the crude product exhibiting an acid value of 172.7 mg KOH/g. In contrast, when the calcination temperature is reduced to 350\u0026deg;C, the catalytic performance decreases markedly, and the yield drops to 63.6%.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c) and (d) show that Meso-5 exhibits the highest catalytic activity, achieving an isostearic acid yield of 73.6% with an acid value of 172.3 mg KOH/g. In contrast, H-5 displays a lower yield of 59.3% and an acid value of 157.6 mg KOH/g. The crude isostearic acid was subsequently purified by low-temperature recrystallization, affording a high-purity product with a purity of 83.4% and an acid value of 186.7 mg KOH/g, which meets commercial standards (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(e)). As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(f), Meso-5 retains high performance over five consecutive cycles, maintaining a selectivity of 82.1% and a yield of 55.6%, only 3.7% lower than the initial yield of H-5. Synergistic interactions between Br\u0026oslash;nsted and Lewis acid sites create stable, high-activity centers that substantially facilitate the isomerization reaction. Meanwhile, the hierarchical pore structure facilitates the diffusion of oleic acid molecules and their isomerized intermediates, minimizes internal diffusion limitations, and improves accessibility to active sites, thereby accelerating the reaction and enhancing both selectivity and product yield.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eH-ZSM-5 zeolites synthesized with different seed types exhibited distinct pore structures. During the isomerization of oleic acid, the commercial H-ZSM-5 zeolite, with an average pore size of only 2.9 nm, hindered the diffusion of oleic acid molecules and therefore showed relatively low catalytic activity. In contrast, the H-ZSM-5 synthesized using Silicalite-1 as a seed exhibited a hierarchical pore structure with an average pore diameter of 5.7 nm, which significantly enhanced molecular diffusion and catalytic performance. The calcination temperature of NH\u003csub\u003e4\u003c/sub\u003e-ZSM-5 exhibited a pronounced influence on catalytic activity, with 400\u0026deg;C identified as the optimal temperature that balances catalytic performance and energy efficiency. Meso-5 efficiently catalyzed the isomerization of oleic acid due to the abundance of Br\u0026oslash;nsted and Lewis acid sites, whose synergistic interactions markedly promoted the formation of branched-chain products. Meso-5 showed excellent catalytic performance in the isomerization of oleic acid, affording 87.3% selectivity and a 71.1% yield in the initial run. Notably, the catalyst retained robust activity after five reuse cycles, maintaining 82.1% selectivity and a 55.6% yield. Evidently, the hierarchical pore structure greatly enhances the diffusion of oleic acid molecules and their isomerized intermediates, thereby reducing internal diffusion resistance and improving the overall catalytic performance. After low-temperature recrystallization of the crude product, high-purity isostearic acid was obtained with a purity of 83.4% and an acid value of 186.7 mg KOH/g. These results provide a solid foundation for further catalyst optimization and the scale-up of isostearic acid production toward industrial application.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eS-1:\u003c/strong\u003e Silicalite-1 seed\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNH\u003csub\u003e4\u003c/sub\u003e-ZSM-5:\u003c/strong\u003e ZSM-5 zeolite with ammonium ions as the balanced cation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eH-ZSM-5:\u003c/strong\u003e ZSM-5 zeolite with hydrogen ions as the balanced cation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMeso-5:\u003c/strong\u003e hierarchical-pore H-ZSM-5\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eXRD:\u003c/strong\u003e X-ray diffraction\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFT-IR:\u003c/strong\u003e Fourier transform infrared spectra\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePy-FTIR:\u003c/strong\u003e Pyridine adsorption infrared spectroscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTGA:\u003c/strong\u003e Thermogravimetric analysis\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBET:\u003c/strong\u003e Brunauer\u0026ndash;Emmett\u0026ndash;Teller\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSEM:\u003c/strong\u003e Scanning electron microscopy\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGC:\u0026nbsp;\u003c/strong\u003eGas Chromatography\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSDA:\u003c/strong\u003e structure-directing agent\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTEAOH:\u003c/strong\u003e tetraethylammonium hydroxide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTPAOH:\u003c/strong\u003e tetrapropylammonium hydroxide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTPABr:\u003c/strong\u003e tetrapropylammonium bromide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eKF:\u0026nbsp;\u003c/strong\u003epotassium fluoride\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCTAB:\u003c/strong\u003e cetyltrimethylammonium bromide\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTEOS\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e tetraethyl orthosilicate\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNi/C:\u003c/strong\u003e Ni-based hydrogenation catalyst\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthics and Consent to Participate\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003ch2\u003eConsent for Publication\u003c/h2\u003e\n\u003cp\u003eAll authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003ch2\u003eCompeting Interest\u003c/h2\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eXincheng Li: Writing – original draft, Investigation, Data curation, Formal analysis. Pengpeng Huang: Investigation. Mingming Fan: Writing – review \u0026amp; editing, Supervision, Resources, Project administration. Pingbo Zhang: Writing – review \u0026amp; editing, Resources, Project administration, Funding acquisition.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (No. 21978112) and MOE \u0026amp; SAFEA for the 111 Project (B13025).\u003c/p\u003e\n\u003ch2\u003eAvailability of data and materials\u003c/h2\u003e\n\u003cp\u003eThe data and materials supporting the findings of this study are available from the corresponding authors upon reasonable request.\u003c/p\u003e\n\u003ch2\u003eAcknowledgments\u003c/h2\u003e\n\u003cp\u003eThis research was financially supported by the National Natural Science Foundation of China (No. 21978112) and the 111 Project of MOE \u0026amp; SAFEA (B13025), for which the authors are sincerely grateful.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKerstens D, Van Praet S, Verhoeven L, et al (2022) Branched Fatty Acids: The Potential of Zeolite Catalysis. 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Chem Commun 57:10624\u0026ndash;10627. https://doi.org/10.1039/D1CC04620A\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme 1","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Isostearic acid, Oleic acid, Isomerization, Hierarchical H-ZSM-5 zeolite","lastPublishedDoi":"10.21203/rs.3.rs-8280043/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8280043/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIsostearic acid, a bio-based and environmentally friendly chemical, has attracted considerable attention because of its high value as an oleic acid derivative. The synthesis of isostearic acid via oleic acid isomerization over commercial H-ZSM-5 zeolites is limited by low yield and acid value, mainly due to diffusion constraints. To address this issue, a hierarchical-pore H-ZSM-5 zeolite (Meso-5) was synthesized using Silicalite-1(S-1) as a seed crystal to enhance diffusion and catalytic performance. The catalyst was comprehensively characterized by XRD, SEM, BET, TGA, FT-IR, and Py-FTIR. Meso-5 efficiently catalyzed the isomerization of oleic acid, attributed to its abundant Br\u0026oslash;nsted and Lewis acid sites whose synergistic interaction significantly promoted the formation of branched-chain products. The catalyst delivered a selectivity of 87.3% with a 71.1% yield in the first run, and even after five reuse cycles it maintained 82.1% selectivity with a 55.6% yield. Evidently, the hierarchical pore structure of the catalyst significantly facilitated the diffusion of oleic acid molecules and their isomerized intermediates, thereby enhancing the overall catalytic activity. The resulting isostearic acid was purified via a simple recrystallization procedure to a purity of 83.4% and an acid value of 186.7 mg KOH/g, both meeting the standards of commercial isostearic acid. These findings provide a robust basis for further catalyst optimization and scale-up toward industrial isostearic acid production.\u003c/p\u003e","manuscriptTitle":"Seed-Assisted Hierarchical H-ZSM-5: Overcoming Diffusion Barriers for Efficient Recyclable Oleic Acid Isomerization to Commercial Isostearic Acid","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-13 17:19:11","doi":"10.21203/rs.3.rs-8280043/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-24T01:58:56+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-18T01:28:03+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-15T04:35:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"331523030577870408927857691264364028610","date":"2025-12-11T23:43:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"237063655797619958581625720675836326636","date":"2025-12-09T15:09:06+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-09T14:53:23+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-04T14:08:24+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-04T14:07:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Catalysis Letters","date":"2025-12-04T13:34:55+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d4b57663-3036-4ef5-bf93-6db5a7e251e8","owner":[],"postedDate":"December 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-26T15:11:02+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-13 17:19:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8280043","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8280043","identity":"rs-8280043","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}