The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO2 for the production of biodiesel

The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO2 for the production of biodiesel | 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 Article The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO 2 for the production of biodiesel SANDRO DOS SANTOS, Moises Pedro, David Nelson, Lucas Paconio, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7421017/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 A catalyst (SiO 2 -RMS) composed of basic silica gel (SiO 2 ) with red mud solution (RMS), which is a waste alkaline solution, was prepared. The SiO 2 -RMS was characterized by FT-IR, SEM, XRD, XRF, BET and TG/DTA analysis. Basicity was determined using the Hammett titration. The SiO 2 -RMS catalyst was employed for the synthesis of biodiesel (FAME - fatty acid methyl esters). Triglycerides from waste cooking oil (WCO) were treated with MeOH, 1:18 molar ratio of WCO/MeOH, at 60 o C during 90 min in the presence of 10.0% (w/w) SiO 2 -RMS:WCO to yield mixtures of FAMEs. The use of SiO 2 -RMS catalyst resulted in a 100% conversion of WCO to FAME. The catalyst was reused in four more transesterification reactions with excellent yields. The reaction times after the first reaction cycle were longer: second cycle 2:30 h, third cycle 4:30 h and fourth cycle 8:30 h. The catalyst is obtained from inexpensive, easily prepared, recyclable and environmentally friendly waste material (waste management). The protocol is highly significant from green and sustainable chemistry perspectives because the reaction involves a renewable catalyst and solvent-free reaction conditions. Physical sciences/Chemistry/Chemical synthesis/Catalyst synthesis Physical sciences/Energy science and technology/Renewable energy/Bioenergy : modification of silica alkaline catalyst reusable catalyst environmentally friendly process red mud fatty acid methyl esters Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Heterogeneous catalysts exist in a phase different from that of the reactants in a reaction process. The catalyst employed in this study is environmentally friendly, non-corrosive, nontoxic, and easy to separate from the reaction mixture. The cost of purification is low, and the catalyst is normally reusable. The active center of a heterogeneous catalyst contains Lewis acid and Brønsted base sites that can furnish electrons or act as proton acceptors to furnish high yields of biodiesel products [ 1 , 2 ]. Heterogeneous catalysts are classified as acid, such as sulfonated silica (SiO 2 -SO 3 H) [ 3 ], or base, such as alkaline earth metal oxides, including calcium oxide or calcium methoxide [ 4 ]. Silica is a crystalline material that has good adsorption properties, high mechanical strength, and high thermal stability [ 5 – 9 ]. Natural sources of silica include rice husk ash [ 10 ] and natural sand [ 3 , 11 ]. The synthetic silica is obtained from the precursors of tetraethyl orthosilicate (TEOS) [ 12 ], tetramethyl orthosilicate (TMOS), and sodium silicate (Na 2 SiO 3 ) [ 13 ]. Si-Han Wu, Chung-Yuan Mou and Hong-Ping Lin described different methods of synthesis for the preparation of well-dispersed mesoporous silica nanoparticles (MSNs) and hollow silica nanoparticles (HSNs) with mesostructures that possess tuneable dimensions ranging from a few to hundreds of nanometers. The methods include fast self-assembly, soft and hard templating, a modified Stőber method, dissolving reconstruction and modified aerogel approaches [ 14 ]. Silica is a material that can be used as a heterogeneous acidic or basic catalyst, making it suitable for biodiesel production. Its acidity can be employed to reduce free fatty acid (FFA) contents in oil via an esterification reaction, whereas its basic character is needed to convert the triglycerides to biodiesel [ 15 ]. Modification of silica can increase its catalytic activity [ 16 ]. Nanosilica-based catalysts have been utilized in FAME production. Like all silica-based catalysts, the nanosilica-based catalyst possesses a high degree of thermal stability, in addition to a large surface area and high degree of porosity. In many studies, nanosilica acts as a support material that improves the properties of the catalyst [ 17 ]. Narayanan and Pandey [ 18 ] prepared nanosilica as a support for lipase. Their study was mathematically simulated using a multiparameter software package, and the results were subsequently confirmed through pilot plant experiments. The effectiveness factor for the use of nanoparticles is close to unity, and the global rate of transesterification is approximately equal to the intrinsic rate. The performance efficiency of the bioreactor increased. Rafee et al. [ 19 ] prepared nanosilica from rice husk. The material is highly pure, amorphous silica having a large surface area, high activity and high degree of reusability. It has been used as a support for 12-tungstophosphoric acid (H 3 PW 12 O 40 ). Nanoscale silica has been shown to possess valuable properties for use in various organic chemical reactions. Saxena et al. [ 20 ] synthesized nanosilica via an inductively coupled plasma (ICP) method. The nanosilica was employed as the medium for the growth of two benthic marine diatoms: Chaetoceros sp . and Thalassiosira sp . These species of algae served as feedstock for the preparation of biodiesel. The study compared normal silica with ICP nanosilica. The production of biodiesel was greater when ICP nanosilica was used. The performance of silica as a catalyst can be improved through the addition of a base to increase its basic properties [21. Some types of highly basic heterogeneous catalysts, such as CaO, possess greater activity and selectivity in transesterification reactions [ 22 , 23 ]. Moradi et al. [ 24 ] employed the sol-gel method for the preparation of a CaO/SiO 2 catalyst for the transesterification of corn oil triglycerides. The optimum composition of CaO/SiO 2 catalyst, which resulted in an 85% yield of biodiesel, contained 70% CaO on SiO 2 at a calcination temperature of 650°C. Another transesterification reaction that employed CaO/Silica catalyst for the conversion of WCO into biodiesel was reported by Lani et al. [ 21 ]. A 90% yield of biodiesel was obtained using a 3% catalyst load, a WCO:MeOH ratio of 1:15, and a 90 min reaction time at a temperature of 60°C. The advantages of the use of silica-based catalysts in FAME production include the fact that it is environmentally friendly, offers easy separation and recovery, has an improved reusability and a lower level of waste generation. Silica-based materials are an important class of catalysts for the production of biodiesel. Ongoing research is focused on the optimization of their properties to improve their efficiency, selectivity, and sustainability in the production of biodiesel [ 3 , 25 ]. In our previously published work, waste alkaline solution from red mud was employed as a homogeneous catalyst for the synthesis of FAME via a transesterification reaction involving WCO and MeOH in aqueous medium [ 26 ]. There is still room for exploration of catalysts with desirable properties. In a recent work, we used SiO 2 -SO 3 H (silicasulfonic acid) as the solid catalyst in the synthesis of FAME [ 3 ]. In the present work, we discussed the use of silica produced from the reaction of construction sand and sodium carbonate [ 7 ] and its modifications with RMS (residue from the industrial production of alumina) to increase the alkaline properties. RMS contains high concentrations of soluble hematite, goethite, gibbsite, boehmite, anatase, rutile, hydrogarnets, and perovskite [ 26 ]. This mixture produced a new solid, basic catalyst, SiO 2 -RMS, which was reusable. It was applied in the production of biodiesel by transesterification. 2. Experimental 2.1. Raw materials and chemicals RM containing RMS was collected from ALCOA (Juruti, PA, Brazil). Silica gel (SiO 2 ) was previously prepared from sand intended for construction [ 7 ]. WCO (soybean) was obtained commercially, and it was purified by filtering through SiO 2 gel. MeOH (analytical grade) was supplied by VETEC, São Paulo, Brazil. 2.2. Typical procedures 2.2.1. Preparation of SiO 2 -RMS catalyst. A 10.000 g portion of SiO 2 was mixed with 35.0 mL RMS, stirred at room temperature for 1 h, dried at 120°C for 24 h, cooled and stored in a desiccator. 2.2.2. Base strength and basicity measurement of SiO 2 -RMS catalyst The base strength of SiO 2 -RMS catalyst was investigated by the Hammett method [ 27 ] employing bromothymol blue (H = 7.2), and phenolphthalein (H = 9.8) as the indicators. Approximately 1.0 mmol of indicator dissolved in 2 mL of benzene was added to 200 mg of SiO 2 -RMS with stirring. The basicity of the SiO 2 -RMS was determined by titrating with 0.1 N benzoic acid dissolved in benzene using the indicator. The endpoint was indicated by the loss of the green color of bromothymol blue. 2.2.3. Reaction of the TGs from WCO and MeOH using SiO 2 -RMS as catalyst. The procedure utilized for the transesterification reaction was based on various trials to determine the optimum conditions for this reaction. A 150-mL round bottom flask containing SiO 2 -RMS (10.00% w/w of WCO) with MeOH (3.75 mL, 0.0928 mol; or 1:18 molar ratio of WCO/MeOH) and WCO (4.417 g; 5.0510 − 3 mol) and equipped with a reflux condenser was heated for 90 min at 60 o C. The beginning of reflux was recorded as time zero. The reaction mixture was cooled, filtered to separate the catalyst (SiO 2 -RMS) and transferred to a separatory funnel, where the upper phase containing the FAME was separated from the lower phase containing glycerol. The MeOH was removed on a rotary evaporator, purified by distillation and used in new reaction processes within this study. The glycerol by-product was filtered through silica gel and stored. The FAME phase was dissolved in hexane (20 mL), washed with 20 mL of a saturated solution of NaCl, dried over MgSO 4 and the solvent was removed on a rotary evaporator. The catalyst was dried at 120 o C and reused three times for the catalysis of transesterification reactions. 2.3. Analysis of WCO and FAME. The official methods proposed by Internal standard ISO 12966 were used to determine the compositional profile by gas chromatography using a flame ionization detector (GC-FID). The EN 14103 European standard and the Brazilian Technical Standards Association (ABNT NBR 15908) methods were used to quantify FAMEs and the remaining mono-, di- and triglycerides (MG, DG, TG) in the FAME. The quantification of the FAME was performed as previously described [ 26 ]. 2.3.1. Thermogravimetry analysis. The thermal behavior of FAME was evaluated by thermogravimetry (TG), and the data were treated in the first derivative to confirm thermal phenomena, thermogravimetry derivative (DTG) and differential thermal analysis (DTA). Simultaneous. TG/DTA curves were obtained on a DTG60H Shimadzu thermobalance; the heating rate was 10 ºC.min − 1 , and the temperature range was 25–350 ºC under a controlled nitrogen atmosphere and under oxidizing conditions (synthetic air), both conditions at 50 mL.min − 1 for comparison purposes. An open alumina crucible with sample mass accurately weighed to about 20 mg was used. The derivative curve was obtained with T.A. data software. 3. Results and Discussion In the present work, FAME could be produced in 100% yield using the SiO 2 -RMS catalytic mixture, and the catalyst could be reused in up to four consecutive processes to produce glycerol with 100% purity after simple filtering through silica gel. In the present work, we sought to obtain a catalytic mixture that was efficient and that could be easily reused, as well as producing glycerol in excellent yield and purity. The procedure used in the first cycle of the production of FAME was the following: SiO 2 -RMS (10.00% w/w of WCO) with MeOH (3.75 mL, 0.0928 mol; or 1:18 molar ratio of WCO/MeOH) and WCO (4.417 g, 5.0510 − 3 mol). The mixture was heated under reflux at 60 o C for 90 min, resulting in a 100% yield of biodiesel. The beginning of reflux was recorded as time zero. The FAME was obtained within 2.5 h in the second cycle, within 4.5 h in the third cycle, within 8.5 h in the fourth cycle and within 20 h in a fifth cycle. All of the processes resulted in total conversion of triglycerides to biodiesel or 100% yields. 3.1. Measurement of the basicity of the SiO 2 -RMS catalyst. The basic strength on the surface of SiO 2 -RMS was determined by the Hammett method using bromothymol blue and phenolphthalein as indicators. When mixed with the catalyst, the color of the two indicators changed, which revealed that the basic strength of SiO 2 -RMS probably lay in the range of 7.2 ≤ H_ ≤ 9.8. 3.2. Thermal gravimetric (TG) analysis of SiO 2 -RMS. The TG curve of WCO (Fig. 1 , left, thick solid line) indicated that the ignition of the oil began at 197 ºC, confirmed by DTG (Fig. 1 , left, thin solid line), with a total loss of mass and release of 4.8 KJ/g in the combustion process. This release can be observed in the large exothermic event in the DTA curve (shaded region, Fig. 1 , left, short dotted line). The heat involved was calculated by integrating the phenomenon with TAdata software. The TG curve of SiO 2 -RMS (Fig. 1 , right, thick solid line) indicated that the sample has a high thermal stability because there was a mass loss of only 11.3% (Δm, shaded region of Fig. 1 , right) up to 800 o C, referring to the waste RMS. The absence of temperature fluctuation in the sample, as observed by the DTA curve (Fig. 1 , right, short, dotted line), indicated that the catalyst is thermally inert or has a low heat capacity, which is a desirable behavior in catalyst materials [ 28 ]. 3.3. Characterization of the SiO 2 -RMS catalyst. 3.3.1. Characterization of the material by powder XRD. The x-ray diffraction (XRD) patterns of the SiO 2 and SiO 2 -RMS materials confirmed that the adsorptions produced a thin layer as a result of the change in the maximum 2 theta position after adsorption and the fact that no significant diffraction peak appeared that was related to RM, as indicated in a previous work [ 26 ]. Another observation is related to the reuse of catalyst that attested to no change in the diffraction patterns, which indicates that there was an effective relationship in the adsorption and mechanical stability of the prepared material. 3.3.2. Nitrogen adsorption/desorption isotherms for SiO 2 and SiO 2 -RMS catalyst. BJH pore size distributions. The BET, Brunauer-Emmett-Teller, method is primarily used to determine the specific surface area of a solid material. The BJH, Barrett-Joyner-Halenda, method is then used to analyze the pore size distribution and pore volume of the solid material. While the BJH method doesn't directly calculate surface area in the same way as BET, it does provide information regarding the surface area within the pores. Textural parameters of SiO 2 gel and SiO 2 -RMS catalyst were determined by N 2 adsorption/desorption isotherms (Fig. 3 ). A type IV behavior with H1 hysteresis, referring to mesoporous materials, was observed for the isotherm. A 49% lower surface area and 37% lower pore volume was observed for the SiO 2 -RMS catalyst (Table 1 ), which confirmed the incorporation of inorganic material from RMS into the silica pores, can clearly be seen in the N 2 adsorption/desorption isotherms. The lower C-BET constant means that the surface of SiO 2 -RMS became less polar, which compromised part of the silanol groups for the adsorption of the catalyst. The pore size distributions of the catalyst determined by BJH (Fig. 3 , inset) are broad (~ 2–20 nm), which is consistent with the amorphous pore structure (XRD). After modification of the pure SiO 2 , the smaller pores were mostly filled; thus, the average pore size in the distribution of SiO 2 -RMS increased. Table 1 Textural parameters obtained from N 2 adsorption/desorption isotherms for pure silica (SiO 2 ) and SiO 2 -RMS catalyst. Sample BET Surface Area (m 2 g − 1 ) Pore volume (cm 3 g − 1 ) Pore size (nm) C-BET SiO 2 43.8 0.246 19.6 105 SiO 2 -RMS 22.5 0.155 24.6 42 3.3.3. FE-SEM of the SiO 2 and SiO 2 -RMS catalyst. The differences between the SiO 2 gel and the SiO 2 -RMS catalyst are also evident in the FE-SEM images shown in Figs. 4 A and B. Even distributions of the silica particles, responsible for its large surface area, form aggregates upon adsorption of the waste alkaline solution onto SiO 2 . The aggregates were separated by macropores several nanometers in diameter. Elemental analysis by Energy Dispersive X-ray Fluorescence (EDXRF), Table 2 , indicates that the elements that were incorporated into SiO 2 -RMS catalyst were clearly Al, K and V, which are the elements with the highest concentration found in the RMS after drying (previous study) [ 26 ]. The concentrations of the remaining elements were practically unchanged. Table 2 Elemental analysis of Energy Dispersive X-ray Fluorescence (EDXRF). Element / Material SiO 2 SiO 2 -RMS SiO 2 99.72 98.51 Al - 0.99 P 0.110 0.120 Cl 0.066 0.160 Ca 0.047 0.048 Ti 0.015 0.008 Cr 0.003 0.003 Fe 0.024 0.019 Ni 0.001 0.002 Cu 0.005 0.002 Zn 0.008 0.005 Pb 0.001 0.002 K - 0.043 V - 0.046 3.4. WCO composition The profile of the compositional analysis of the WCO used in this work is described in a previous paper [ 26 ]. The composition of the WCO was very similar to that of soybean oil (SO) reported in the literature [ 28 , 29 ]. This profile was considered for calculating the molar ratio of WCO:MeOH for the transesterification reaction. 3.5. The 1 H NMR spectrum of WCO. The 1 H NMR spectrum for WCO is presented in Fig. 5. The peaks characteristic of the triglyceride chains in WCO are in complete agreement with those of the literature [ 30 – 32 ]. 3.6. Transesterification of TGs from WCO with MeOH using SiO 2 -RMS as catalyst. In this study, an excess of MeOH was mixed with SiO 2 -RMS and WCO and heated at 60 o C while the progress of the reaction was monitored by thin layer chromatography (TLC). The total consumption of TGs occurred within 90 min. The FAMEs and glycerides (MG, DG, and TG) contained in the FAME phase were confirmed by GC-FID using the methods defined in EN 14103 and ASTM D6584. A 99.73% yield of FAME was obtained in the first cycle. The SiO 2 -RMS was recovered and reused four times. A 98.79% yield was obtained in the second reaction over a 2.5 h period, the third reaction lasted 4.5 h (98.56%), the fourth reaction required 8.5 h (98.29%), and 20 h was necessary in the fifth reaction (98.19%). An 80.17% yield was obtained in a sixth reaction that lasted 30 h. 3.7. 1 H NMR analysis of FAME. The formation of FAME could be observed when the spectrum depicted in Fig. 6 was compared with that of Fig. 6 . A summary of assignments of the peaks of the 1 H NMR spectrum of FAME and that of WCO is presented in Table 3 . The -CH 2 protons related to the glycerides of WCO, which appeared in the range of δ 4.12–4.31 ppm in Fig. 5, completely disappeared. This disappearance was accompanied by the appearance of a strong peak at δ = 3.66 ppm representing the -OCH 3 of FAME [ 32 ]. Table 3 1 H NMR peaks characteristic of FAME and the corresponding WCO. Chemical shift, δ (ppm) Proton (s) Functional group WCO FAME CH 3 -C Terminal methyl group 0.80–1.01 0.82–1.02 -(CH 2 ) n - Backbone CH 2 1.20–1.41 1.22–1.42 -C H 2 CH 2 -COOH β-methylene proton 1.53–1.70 1.54–1.70 =CH-C H 2 - methylene group alpha to a double bond 1.94–2.11 1.95–2.11 CH 2 COOR ester α-methylene group 2.31 2.30 =CH-C H 2 -CH= methylene group alpha to two double bonds 2.76 2.77 -COOCH 3 Ester methyl group absent 3.66 -CH 2 OCOR Methylene group (C 1 and C 3 ) of glyceride 4.09–4.34 absent -CHOCOR Methinyl proton at C 2 of glyceride 5.25 absent -CH = CH- Vinyl protons 5.28–5.43 5.26–5.45 3.8. Thermogravimetry analysis of FAME. The thermogravimetric analysis of FAME (Fig. 7 ) has been previously reported [ 26 ]. The results were in accord with that reported in the literature [ 26 ]. 3.9. Infrared analysis of FAME. The infrared spectra of FAME (from WCO) shown in Fig. 8 demonstrated the transformation of WCO into FAME. The strong ester peaks can be seen at 1744 (the C = O vibration) and around 1170–1197 cm − 1 for O-CH 3 stretching vibrations. IR bands in the region 1436–1464 cm − 1 for CH 3 asymmetric bending. The peaks characteristic of the FAME are in complete agreement with those of the literature [ 33 ]. 4. Conclusions The SiO 2 -RMS catalyst was prepared and used for the catalysis of the transesterification of triglycerides in heterogeneous medium. It has the advantage of being formed from waste material industrial; it is cheap, easily prepared, and environmentally friendly. It has basic properties, a 22.5 m 2 .g − 1 surface area, good chemical stability, and has been shown to be an excellent catalyst. The addition of RMS for the transesterification of WCO produced up to 100% FAME. The SiO 2 -RMS catalyst was reused with excellent yields in four additional transesterifications of triglycerides without loss of effectiveness or the formation of by-products, such as soap. This result is different from that obtained with the basic catalysts used in FAME production. A high degree of effectiveness in all the repetitions was observed, which increases the viability of its implementation. The accumulation of industrial waste can be a reason for great concern for the environment if not properly managed. In this work, we demonstrated that waste such as RM can be of great importance in the production of new catalysts for classical reactions such as transesterification. In 2025, global red mud production from refining of alumina is projected to reach around 150 million tons. This waste byproduct of aluminum production is primarily stored in containment ponds or dams, and billions of tons are accumulated globally. This work contributes to the growing interest in valorizing RM for the recovery of resources. Only 2–3% is currently effectively utilized. Declarations 5. Acknowledgements The authors acknowledge the support by the SENAI CIMATEC, PRPPG/UFVJM in response to Resolução 15/2019, LMMA sponsored by FAPEMIG APQ-03088-2 and the Fundação de Apoio à Pesquisa do Estado de Minas Gerais - FAPEMIG (Chamada Universal), 0004022 code. Data availability The paper entitled ‘‘The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO 2 for the production of biodiesel” is submitted for your kind considerations. The research data policy and data availability are not shared with anyone before publication. References Wijaya K, Nadia A, Dinana A, Pratiwi AF, Tikoalu AD (2021a) Wibowo AC (2021) Catalytic hydrocracking of fresh and waste frying oil over Ni- and Mo-Based catalysts supported on sulfated silica for biogasoline production. 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Biomass Bioenergy 63: 22–32. https://doi.org/10.1016/j.biombioe.2014.01.034 Chiplunkar PP, Pratap AP (2016) Utilization of Sunflower Acid Oil for Synthesis of Alkyd Resin. Progressing Organic Coatings 93: 61–67. https://doi.org/10.1016/j.porgcoat.2016.01.002 Shimamoto GG, Favaro MMA, Tubino M (2015) Simple Methods via Mid-IR or 1 H NMR Spectroscopy for the Determination of the Iodine Value of Vegetable Oils. Journal Brazilian Chemical Society 26: 1431–1437. https://doi.org/10.5935/0103-5053.20150111 Vlahov G (1999) Application of NMR to the Study of Olive Oils. Progress in Nuclear Magnetic Resonance Spectroscopy 35: 341–357. https://doi.org/10.1016/S0079-6565(99)00015-1 Chakraborty R, Bepari S, Banerjee A (2010)Transesterification of soybean oil catalyzed by fly ash and egg shell derived solid catalysts. Chemical Engineering Journal 165(3): 798–805. https://doi.org/10.1016/j.cej.2010.10.019 Additional Declarations There is NO Competing Interest. Supplementary Files SupplementarymaterialbiodieselSiO2RMS.docx The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO2 for the production of biodiesel 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-7421017","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":503535087,"identity":"659e1657-b6e0-4a28-90ab-5da3f5975a1d","order_by":0,"name":"SANDRO DOS SANTOS","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABE0lEQVRIiWNgGAWjYJACCSBOYGDgAbFtGNgbQBwGZog4EVrSGHgOkKjlMEgLA14t8u1nD96uqGDI45999uDDHzXnE3skEp5uYKiwTmyQ7n2ATYvBmbxkyzNnGIolzuUlG/Mcuw3SknaD4Ux6YoPMcQOsWhhyzCQb2xgSG87wmEkzsN1O3M9zIO0GY9vhxAaJNOwO638D0TIfqEXyx79ziT1gLf9wa2G4AbVlA1CLBG/bgcQe9gaglgbcWgxuvDG2bDgjUWx4hi/ZmLcv2RisJeFYunGbzDEcDssxvNlQYZMnd4YXGGLf7GR7mHnSbnyosZbtl27D7jAIQIkCngRwZLLh04AG2A+QoHgUjIJRMApGAAAAcrtjNyKup5wAAAAASUVORK5CYII=","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":true,"prefix":"","firstName":"SANDRO","middleName":"DOS","lastName":"SANTOS","suffix":""},{"id":503535088,"identity":"d66bc794-4c2e-4826-8d0a-0f097a50e49e","order_by":1,"name":"Moises Pedro","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"Moises","middleName":"","lastName":"Pedro","suffix":""},{"id":503535089,"identity":"c28e89ba-62cb-4581-9996-9bfec9f06ed6","order_by":2,"name":"David Nelson","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"David","middleName":"","lastName":"Nelson","suffix":""},{"id":503535090,"identity":"d9b068ca-cc26-4dbd-b80c-e3fc30281328","order_by":3,"name":"Lucas Paconio","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"Lucas","middleName":"","lastName":"Paconio","suffix":""},{"id":503535091,"identity":"6e4dd9ec-06f6-4cf1-a281-0e89ebab6912","order_by":4,"name":"Milton Freitas","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"Milton","middleName":"","lastName":"Freitas","suffix":""},{"id":503535092,"identity":"f3d7a248-929a-4709-a99c-c3d885162bc3","order_by":5,"name":"Alexandre Wentz","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"Alexandre","middleName":"","lastName":"Wentz","suffix":""},{"id":503535093,"identity":"a791f6b1-73f1-42fc-a01a-3b669fa2b5dd","order_by":6,"name":"Daniel Bortoleto","email":"","orcid":"","institution":"Federal University of Jequitinhonha and Mucuri Valleys","correspondingAuthor":false,"prefix":"","firstName":"Daniel","middleName":"","lastName":"Bortoleto","suffix":""},{"id":503535094,"identity":"b074c65f-eb90-4528-b0c5-8f2e0a667afa","order_by":7,"name":"Fernando Pessoa","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Fernando","middleName":"","lastName":"Pessoa","suffix":""},{"id":503535095,"identity":"6d79eb66-0263-4efb-8f7c-6be418fa6468","order_by":8,"name":"Foster Agblevor","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Foster","middleName":"","lastName":"Agblevor","suffix":""},{"id":503535096,"identity":"d442367f-75fd-4d28-9dbf-8349f8649e38","order_by":9,"name":"Maria Marques","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"","lastName":"Marques","suffix":""},{"id":503535097,"identity":"557d6250-ad1c-4d1c-8d23-81c0141b7fdd","order_by":10,"name":"Lucas Zanatta","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Lucas","middleName":"","lastName":"Zanatta","suffix":""}],"badges":[],"createdAt":"2025-08-21 00:20:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7421017/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7421017/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89943165,"identity":"b790a532-14f2-46e1-91fe-dff775e40da4","added_by":"auto","created_at":"2025-08-26 16:31:17","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":149193,"visible":true,"origin":"","legend":"\u003cp\u003eThermal behavior of WCO (left) and SiO\u003csub\u003e2\u003c/sub\u003e-RMS (right) determined by thermogravimetry (TG – thick solid line), thermogravimetry derivative (DTG – thin solid line) and differential thermal analysis (DTA – short, dotted line).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/1cb4b8581b673afb6ac622ea.png"},{"id":89943868,"identity":"3bfdf1e4-f5d7-49da-950d-e7ea3add4b68","added_by":"auto","created_at":"2025-08-26 16:39:17","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":152887,"visible":true,"origin":"","legend":"\u003cp\u003eThe XRD patterns of pure SiO\u003csub\u003e2\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e-RMS materials before and after catalyzed reactions.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/d495d6b83260588f0526ebb6.png"},{"id":89943163,"identity":"229b417f-b7f9-48d5-832f-1e695f1a7d2b","added_by":"auto","created_at":"2025-08-26 16:31:17","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":128877,"visible":true,"origin":"","legend":"\u003cp\u003eN\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms for pure silica (SiO\u003csub\u003e2\u003c/sub\u003e) and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst (black squares) and BJH pore size distributions (red line graphs inserted).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/25382b70e4322715c75005a0.png"},{"id":89943169,"identity":"4c5eaf04-a4af-47a9-8d9d-d4fc8b7df33a","added_by":"auto","created_at":"2025-08-26 16:31:17","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":286758,"visible":true,"origin":"","legend":"\u003cp\u003eFE-SEM images of the amorphous silica gel (A) and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst (B).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/9cc1a98e405a84a6fc1b56ee.png"},{"id":89943872,"identity":"11683d8c-3154-41d0-8268-d12b2d084b23","added_by":"auto","created_at":"2025-08-26 16:39:17","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":148162,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eH NMR spectra were recorded on Bruker \u003cem\u003eAvance\u003c/em\u003e 400 spectrometers. (400 MHz, CDCl\u003csub\u003e3\u003c/sub\u003e) spectrum of WCO.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/60d10f442d3579f5852f5599.png"},{"id":89943167,"identity":"79407986-f1cb-4a15-8646-ef279a31ddd7","added_by":"auto","created_at":"2025-08-26 16:31:17","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":84972,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, CDCl\u003csub\u003e3\u003c/sub\u003e) spectrum of FAME. \u003csup\u003e1\u003c/sup\u003eH NMR (400 MHz, CDCl\u003csub\u003e3\u003c/sub\u003e) δ 5.45-5.26 (m, 5H), 3.66 (s, 6H), 2.77 (dd, J = 13.7, 6.9 Hz, 2H), 2.30 (t, J = 7.6 Hz, 4H), 2.11-1.95 (m, 6H), 1.70-1.54 (m, 5H), 1.27 (dd, J = 13.3, 6.2 Hz, 36H), 1.02-0.82 (m, 6H).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/63da47ea82d3dfceeb74119b.png"},{"id":89943873,"identity":"33de91f7-0b7a-4129-9c5a-0bc38c28a24a","added_by":"auto","created_at":"2025-08-26 16:39:17","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":124882,"visible":true,"origin":"","legend":"\u003cp\u003eThermal behavior of FAME under inert (N\u003csub\u003e2\u003c/sub\u003e) conditions (left) and oxidizing (air) conditions (right).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/3a4ff4e9925686d5339fe6e1.png"},{"id":89944048,"identity":"1e5316f0-1954-407c-b455-8b83c4e6aa6b","added_by":"auto","created_at":"2025-08-26 16:47:17","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":38889,"visible":true,"origin":"","legend":"\u003cp\u003eA typical FTIR Spectrum of FAME.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/d922fd8a6815cee07a20ec89.png"},{"id":90336294,"identity":"19dd1197-e579-45c8-b57a-fc4f3c97b73a","added_by":"auto","created_at":"2025-09-01 14:14:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2032308,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/8951e16f-18c1-44b6-914b-abb442ed6b8d.pdf"},{"id":89943181,"identity":"5ebb3de1-b68b-4c59-bea0-14ff483c57da","added_by":"auto","created_at":"2025-08-26 16:31:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":5738413,"visible":true,"origin":"","legend":"The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO2 for the production of biodiesel","description":"","filename":"SupplementarymaterialbiodieselSiO2RMS.docx","url":"https://assets-eu.researchsquare.com/files/rs-7421017/v1/53cc930678cd970f20fe0d29.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eThe application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e for the production of biodiesel\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHeterogeneous catalysts exist in a phase different from that of the reactants in a reaction process. The catalyst employed in this study is environmentally friendly, non-corrosive, nontoxic, and easy to separate from the reaction mixture. The cost of purification is low, and the catalyst is normally reusable. The active center of a heterogeneous catalyst contains Lewis acid and Br\u0026oslash;nsted base sites that can furnish electrons or act as proton acceptors to furnish high yields of biodiesel products [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Heterogeneous catalysts are classified as acid, such as sulfonated silica (SiO\u003csub\u003e2\u003c/sub\u003e-SO\u003csub\u003e3\u003c/sub\u003eH) [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], or base, such as alkaline earth metal oxides, including calcium oxide or calcium methoxide [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSilica is a crystalline material that has good adsorption properties, high mechanical strength, and high thermal stability [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Natural sources of silica include rice husk ash [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and natural sand [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The synthetic silica is obtained from the precursors of tetraethyl orthosilicate (TEOS) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], tetramethyl orthosilicate (TMOS), and sodium silicate (Na\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e3\u003c/sub\u003e) [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Si-Han Wu, Chung-Yuan Mou and Hong-Ping Lin described different methods of synthesis for the preparation of well-dispersed mesoporous silica nanoparticles (MSNs) and hollow silica nanoparticles (HSNs) with mesostructures that possess tuneable dimensions ranging from a few to hundreds of nanometers. The methods include fast self-assembly, soft and hard templating, a modified Stőber method, dissolving reconstruction and modified aerogel approaches [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSilica is a material that can be used as a heterogeneous acidic or basic catalyst, making it suitable for biodiesel production. Its acidity can be employed to reduce free fatty acid (FFA) contents in oil via an esterification reaction, whereas its basic character is needed to convert the triglycerides to biodiesel [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Modification of silica can increase its catalytic activity [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Nanosilica-based catalysts have been utilized in FAME production. Like all silica-based catalysts, the nanosilica-based catalyst possesses a high degree of thermal stability, in addition to a large surface area and high degree of porosity.\u003c/p\u003e\u003cp\u003eIn many studies, nanosilica acts as a support material that improves the properties of the catalyst [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Narayanan and Pandey [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] prepared nanosilica as a support for lipase. Their study was mathematically simulated using a multiparameter software package, and the results were subsequently confirmed through pilot plant experiments. The effectiveness factor for the use of nanoparticles is close to unity, and the global rate of transesterification is approximately equal to the intrinsic rate. The performance efficiency of the bioreactor increased.\u003c/p\u003e\u003cp\u003eRafee et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] prepared nanosilica from rice husk. The material is highly pure, amorphous silica having a large surface area, high activity and high degree of reusability. It has been used as a support for 12-tungstophosphoric acid (H\u003csub\u003e3\u003c/sub\u003ePW\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e40\u003c/sub\u003e). Nanoscale silica has been shown to possess valuable properties for use in various organic chemical reactions.\u003c/p\u003e\u003cp\u003eSaxena et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] synthesized nanosilica via an inductively coupled plasma (ICP) method. The nanosilica was employed as the medium for the growth of two benthic marine diatoms: \u003cem\u003eChaetoceros sp\u003c/em\u003e. and \u003cem\u003eThalassiosira sp\u003c/em\u003e. These species of algae served as feedstock for the preparation of biodiesel. The study compared normal silica with ICP nanosilica. The production of biodiesel was greater when ICP nanosilica was used.\u003c/p\u003e\u003cp\u003eThe performance of silica as a catalyst can be improved through the addition of a base to increase its basic properties [21. Some types of highly basic heterogeneous catalysts, such as CaO, possess greater activity and selectivity in transesterification reactions [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Moradi et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] employed the sol-gel method for the preparation of a CaO/SiO\u003csub\u003e2\u003c/sub\u003e catalyst for the transesterification of corn oil triglycerides. The optimum composition of CaO/SiO\u003csub\u003e2\u003c/sub\u003e catalyst, which resulted in an 85% yield of biodiesel, contained 70% CaO on SiO\u003csub\u003e2\u003c/sub\u003e at a calcination temperature of 650\u0026deg;C. Another transesterification reaction that employed CaO/Silica catalyst for the conversion of WCO into biodiesel was reported by Lani et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. A 90% yield of biodiesel was obtained using a 3% catalyst load, a WCO:MeOH ratio of 1:15, and a 90 min reaction time at a temperature of 60\u0026deg;C.\u003c/p\u003e\u003cp\u003eThe advantages of the use of silica-based catalysts in FAME production include the fact that it is environmentally friendly, offers easy separation and recovery, has an improved reusability and a lower level of waste generation. Silica-based materials are an important class of catalysts for the production of biodiesel. Ongoing research is focused on the optimization of their properties to improve their efficiency, selectivity, and sustainability in the production of biodiesel [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. In our previously published work, waste alkaline solution from red mud was employed as a homogeneous catalyst for the synthesis of FAME via a transesterification reaction involving WCO and MeOH in aqueous medium [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. There is still room for exploration of catalysts with desirable properties.\u003c/p\u003e\u003cp\u003eIn a recent work, we used SiO\u003csub\u003e2\u003c/sub\u003e-SO\u003csub\u003e3\u003c/sub\u003eH (silicasulfonic acid) as the solid catalyst in the synthesis of FAME [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In the present work, we discussed the use of silica produced from the reaction of construction sand and sodium carbonate [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and its modifications with RMS (residue from the industrial production of alumina) to increase the alkaline properties. RMS contains high concentrations of soluble hematite, goethite, gibbsite, boehmite, anatase, rutile, hydrogarnets, and perovskite [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This mixture produced a new solid, basic catalyst, SiO\u003csub\u003e2\u003c/sub\u003e-RMS, which was reusable. It was applied in the production of biodiesel by transesterification.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Raw materials and chemicals\u003c/h2\u003e\u003cp\u003eRM containing RMS was collected from ALCOA (Juruti, PA, Brazil). Silica gel (SiO\u003csub\u003e2\u003c/sub\u003e) was previously prepared from sand intended for construction [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. WCO (soybean) was obtained commercially, and it was purified by filtering through SiO\u003csub\u003e2\u003c/sub\u003e gel. MeOH (analytical grade) was supplied by VETEC, S\u0026atilde;o Paulo, Brazil.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Typical procedures\u003c/h2\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.2.1. Preparation of SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst.\u003c/h2\u003e\u003cp\u003eA 10.000 g portion of SiO\u003csub\u003e2\u003c/sub\u003e was mixed with 35.0 mL RMS, stirred at room temperature for 1 h, dried at 120\u0026deg;C for 24 h, cooled and stored in a desiccator.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.2.2. Base strength and basicity measurement of SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst\u003c/h2\u003e\u003cp\u003eThe base strength of SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst was investigated by the Hammett method [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] employing bromothymol blue (H\u0026thinsp;=\u0026thinsp;7.2), and phenolphthalein (H\u0026thinsp;=\u0026thinsp;9.8) as the indicators. Approximately 1.0 mmol of indicator dissolved in 2 mL of benzene was added to 200 mg of SiO\u003csub\u003e2\u003c/sub\u003e-RMS with stirring. The basicity of the SiO\u003csub\u003e2\u003c/sub\u003e-RMS was determined by titrating with 0.1 N benzoic acid dissolved in benzene using the indicator. The endpoint was indicated by the loss of the green color of bromothymol blue.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.2.3. Reaction of the TGs from WCO and MeOH using SiO\u003csub\u003e2\u003c/sub\u003e-RMS as catalyst.\u003c/h2\u003e\u003cp\u003eThe procedure utilized for the transesterification reaction was based on various trials to determine the optimum conditions for this reaction. A 150-mL round bottom flask containing SiO\u003csub\u003e2\u003c/sub\u003e-RMS (10.00% w/w of WCO) with MeOH (3.75 mL, 0.0928 mol; or 1:18 molar ratio of WCO/MeOH) and WCO (4.417 g; 5.0510\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e mol) and equipped with a reflux condenser was heated for 90 min at 60 \u003csup\u003eo\u003c/sup\u003eC. The beginning of reflux was recorded as time zero. The reaction mixture was cooled, filtered to separate the catalyst (SiO\u003csub\u003e2\u003c/sub\u003e-RMS) and transferred to a separatory funnel, where the upper phase containing the FAME was separated from the lower phase containing glycerol. The MeOH was removed on a rotary evaporator, purified by distillation and used in new reaction processes within this study. The glycerol by-product was filtered through silica gel and stored. The FAME phase was dissolved in hexane (20 mL), washed with 20 mL of a saturated solution of NaCl, dried over MgSO\u003csub\u003e4\u003c/sub\u003e and the solvent was removed on a rotary evaporator. The catalyst was dried at 120 \u003csup\u003eo\u003c/sup\u003eC and reused three times for the catalysis of transesterification reactions.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Analysis of WCO and FAME.\u003c/h2\u003e\u003cp\u003eThe official methods proposed by Internal standard ISO 12966 were used to determine the compositional profile by gas chromatography using a flame ionization detector (GC-FID). The EN 14103 European standard and the Brazilian Technical Standards Association (ABNT NBR 15908) methods were used to quantify FAMEs and the remaining mono-, di- and triglycerides (MG, DG, TG) in the FAME. The quantification of the FAME was performed as previously described [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e2.3.1. Thermogravimetry analysis.\u003c/h2\u003e\u003cp\u003eThe thermal behavior of FAME was evaluated by thermogravimetry (TG), and the data were treated in the first derivative to confirm thermal phenomena, thermogravimetry derivative (DTG) and differential thermal analysis (DTA). Simultaneous. TG/DTA curves were obtained on a DTG60H Shimadzu thermobalance; the heating rate was 10 \u0026ordm;C.min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the temperature range was 25\u0026ndash;350 \u0026ordm;C under a controlled nitrogen atmosphere and under oxidizing conditions (synthetic air), both conditions at 50 mL.min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for comparison purposes. An open alumina crucible with sample mass accurately weighed to about 20 mg was used. The derivative curve was obtained with T.A. data software.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eIn the present work, FAME could be produced in 100% yield using the SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalytic mixture, and the catalyst could be reused in up to four consecutive processes to produce glycerol with 100% purity after simple filtering through silica gel.\u003c/p\u003e\u003cp\u003eIn the present work, we sought to obtain a catalytic mixture that was efficient and that could be easily reused, as well as producing glycerol in excellent yield and purity. The procedure used in the first cycle of the production of FAME was the following: SiO\u003csub\u003e2\u003c/sub\u003e-RMS (10.00% w/w of WCO) with MeOH (3.75 mL, 0.0928 mol; or 1:18 molar ratio of WCO/MeOH) and WCO (4.417 g, 5.0510\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e mol). The mixture was heated under reflux at 60 \u003csup\u003eo\u003c/sup\u003eC for 90 min, resulting in a 100% yield of biodiesel. The beginning of reflux was recorded as time zero.\u003c/p\u003e\u003cp\u003eThe FAME was obtained within 2.5 h in the second cycle, within 4.5 h in the third cycle, within 8.5 h in the fourth cycle and within 20 h in a fifth cycle. All of the processes resulted in total conversion of triglycerides to biodiesel or 100% yields.\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Measurement of the basicity of the SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst.\u003c/h2\u003e\u003cp\u003eThe basic strength on the surface of SiO\u003csub\u003e2\u003c/sub\u003e-RMS was determined by the Hammett method using bromothymol blue and phenolphthalein as indicators. When mixed with the catalyst, the color of the two indicators changed, which revealed that the basic strength of SiO\u003csub\u003e2\u003c/sub\u003e-RMS probably lay in the range of 7.2\u0026thinsp;\u0026le;\u0026thinsp;H_ \u0026le; 9.8.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Thermal gravimetric (TG) analysis of SiO\u003csub\u003e2\u003c/sub\u003e-RMS.\u003c/h2\u003e\u003cp\u003eThe TG curve of WCO (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, left, thick solid line) indicated that the ignition of the oil began at 197 \u0026ordm;C, confirmed by DTG (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, left, thin solid line), with a total loss of mass and release of 4.8 KJ/g in the combustion process. This release can be observed in the large exothermic event in the DTA curve (shaded region, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, left, short dotted line). The heat involved was calculated by integrating the phenomenon with TAdata software. The TG curve of SiO\u003csub\u003e2\u003c/sub\u003e-RMS (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, right, thick solid line) indicated that the sample has a high thermal stability because there was a mass loss of only 11.3% (Δm, shaded region of Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, right) up to 800 \u003csup\u003eo\u003c/sup\u003eC, referring to the waste RMS. The absence of temperature fluctuation in the sample, as observed by the DTA curve (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, right, short, dotted line), indicated that the catalyst is thermally inert or has a low heat capacity, which is a desirable behavior in catalyst materials [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Characterization of the SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst.\u003c/h2\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.3.1. Characterization of the material by powder XRD.\u003c/h2\u003e\u003cp\u003eThe x-ray diffraction (XRD) patterns of the SiO\u003csub\u003e2\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e-RMS materials confirmed that the adsorptions produced a thin layer as a result of the change in the maximum 2 theta position after adsorption and the fact that no significant diffraction peak appeared that was related to RM, as indicated in a previous work [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Another observation is related to the reuse of catalyst that attested to no change in the diffraction patterns, which indicates that there was an effective relationship in the adsorption and mechanical stability of the prepared material.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.3.2. Nitrogen adsorption/desorption isotherms for SiO\u003csub\u003e2\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst. BJH pore size distributions.\u003c/h2\u003e\u003cp\u003eThe BET, Brunauer-Emmett-Teller, method is primarily used to determine the specific surface area of a solid material. The BJH, Barrett-Joyner-Halenda, method is then used to analyze the pore size distribution and pore volume of the solid material. While the BJH method doesn't directly calculate surface area in the same way as BET, it does provide information regarding the surface area within the pores.\u003c/p\u003e\u003cp\u003eTextural parameters of SiO\u003csub\u003e2\u003c/sub\u003e gel and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst were determined by N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). A type IV behavior with H1 hysteresis, referring to mesoporous materials, was observed for the isotherm.\u003c/p\u003e\u003cp\u003eA 49% lower surface area and 37% lower pore volume was observed for the SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), which confirmed the incorporation of inorganic material from RMS into the silica pores, can clearly be seen in the N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms. The lower C-BET constant means that the surface of SiO\u003csub\u003e2\u003c/sub\u003e-RMS became less polar, which compromised part of the silanol groups for the adsorption of the catalyst. The pore size distributions of the catalyst determined by BJH (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, inset) are broad (~\u0026thinsp;2\u0026ndash;20 nm), which is consistent with the amorphous pore structure (XRD). After modification of the pure SiO\u003csub\u003e2\u003c/sub\u003e, the smaller pores were mostly filled; thus, the average pore size in the distribution of SiO\u003csub\u003e2\u003c/sub\u003e-RMS increased.\u003c/p\u003e\u003cp\u003e\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\u003eTextural parameters obtained from N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms for pure silica (SiO\u003csub\u003e2\u003c/sub\u003e) and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst.\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\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBET Surface Area (m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePore volume (cm\u003csup\u003e3\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePore size (nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eC-BET\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e43.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.246\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e19.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e105\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e-RMS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e22.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.155\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e24.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e42\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=\"Sec16\" class=\"Section3\"\u003e\u003ch2\u003e3.3.3. FE-SEM of the SiO\u003csub\u003e2\u003c/sub\u003e and SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst.\u003c/h2\u003e\u003cp\u003eThe differences between the SiO\u003csub\u003e2\u003c/sub\u003e gel and the SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst are also evident in the FE-SEM images shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA and B. Even distributions of the silica particles, responsible for its large surface area, form aggregates upon adsorption of the waste alkaline solution onto SiO\u003csub\u003e2\u003c/sub\u003e. The aggregates were separated by macropores several nanometers in diameter.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eElemental analysis by Energy Dispersive X-ray Fluorescence (EDXRF), Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, indicates that the elements that were incorporated into SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst were clearly Al, K and V, which are the elements with the highest concentration found in the RMS after drying (previous study) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The concentrations of the remaining elements were practically unchanged.\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\u003eElemental analysis of Energy Dispersive X-ray Fluorescence (EDXRF).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eElement\u003csub\u003e/\u003c/sub\u003e Material\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e-RMS\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e99.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e98.51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.110\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.120\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.066\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.160\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCa\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.047\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.048\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTi\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.015\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.008\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCr\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.003\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.003\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.024\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.019\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNi\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCu\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.005\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eZn\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.008\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.005\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePb\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eK\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.043\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eV\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.046\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\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.4. WCO composition\u003c/h2\u003e\u003cp\u003eThe profile of the compositional analysis of the WCO used in this work is described in a previous paper [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The composition of the WCO was very similar to that of soybean oil (SO) reported in the literature [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. This profile was considered for calculating the molar ratio of WCO:MeOH for the transesterification reaction.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e3.5. The \u003csup\u003e1\u003c/sup\u003eH NMR spectrum of WCO.\u003c/h2\u003e\u003cp\u003eThe \u003csup\u003e1\u003c/sup\u003eH NMR spectrum for WCO is presented in Fig.\u0026nbsp;5. The peaks characteristic of the triglyceride chains in WCO are in complete agreement with those of the literature [\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003e3.6. Transesterification of TGs from WCO with MeOH using SiO\u003csub\u003e2\u003c/sub\u003e-RMS as catalyst.\u003c/h2\u003e\u003cp\u003eIn this study, an excess of MeOH was mixed with SiO\u003csub\u003e2\u003c/sub\u003e-RMS and WCO and heated at 60 \u003csup\u003eo\u003c/sup\u003eC while the progress of the reaction was monitored by thin layer chromatography (TLC). The total consumption of TGs occurred within 90 min. The FAMEs and glycerides (MG, DG, and TG) contained in the FAME phase were confirmed by GC-FID using the methods defined in EN 14103 and ASTM D6584. A 99.73% yield of FAME was obtained in the first cycle. The SiO\u003csub\u003e2\u003c/sub\u003e-RMS was recovered and reused four times. A 98.79% yield was obtained in the second reaction over a 2.5 h period, the third reaction lasted 4.5 h (98.56%), the fourth reaction required 8.5 h (98.29%), and 20 h was necessary in the fifth reaction (98.19%). An 80.17% yield was obtained in a sixth reaction that lasted 30 h.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003e3.7. \u003csup\u003e1\u003c/sup\u003eH NMR analysis of FAME.\u003c/h2\u003e\u003cp\u003eThe formation of FAME could be observed when the spectrum depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e was compared with that of Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eA summary of assignments of the peaks of the \u003csup\u003e1\u003c/sup\u003eH NMR spectrum of FAME and that of WCO is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The -CH\u003csub\u003e2\u003c/sub\u003e protons related to the glycerides of WCO, which appeared in the range of δ 4.12\u0026ndash;4.31 ppm in Fig.\u0026nbsp;5, completely disappeared. This disappearance was accompanied by the appearance of a strong peak at δ\u0026thinsp;=\u0026thinsp;3.66 ppm representing the -OCH\u003csub\u003e3\u003c/sub\u003e of FAME [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\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\u003e\u003csup\u003e1\u003c/sup\u003eH NMR peaks characteristic of FAME and the corresponding WCO.\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=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eChemical shift, δ (ppm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProton (s)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFunctional group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWCO\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eFAME\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCH\u003csub\u003e3\u003c/sub\u003e-C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTerminal methyl group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.80\u0026ndash;1.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.82\u0026ndash;1.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003en\u003c/sub\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBackbone CH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.20\u0026ndash;1.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.22\u0026ndash;1.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-C\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eH\u003c/span\u003e\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003e-COOH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eβ-methylene proton\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.53\u0026ndash;1.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.54\u0026ndash;1.70\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e=CH-C\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eH\u003c/span\u003e\u003csub\u003e2\u003c/sub\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emethylene group alpha to a double bond\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.94\u0026ndash;2.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.95\u0026ndash;2.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCH\u003csub\u003e2\u003c/sub\u003eCOOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eester α-methylene group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e=CH-C\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eH\u003c/span\u003e\u003csub\u003e2\u003c/sub\u003e-CH=\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003emethylene group alpha to two double bonds\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-COOCH\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEster methyl group\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eabsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.66\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-CH\u003csub\u003e2\u003c/sub\u003eOCOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMethylene group (C\u003csub\u003e1\u003c/sub\u003e and C\u003csub\u003e3\u003c/sub\u003e) of glyceride\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.09\u0026ndash;4.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eabsent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-CHOCOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMethinyl proton at C\u003csub\u003e2\u003c/sub\u003e of glyceride\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eabsent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e-CH\u0026thinsp;=\u0026thinsp;CH-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVinyl protons\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.28\u0026ndash;5.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.26\u0026ndash;5.45\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=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003e3.8. Thermogravimetry analysis of FAME.\u003c/h2\u003e\u003cp\u003eThe thermogravimetric analysis of FAME (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e) has been previously reported [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The results were in accord with that reported in the literature [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\u003ch2\u003e3.9. Infrared analysis of FAME.\u003c/h2\u003e\u003cp\u003eThe infrared spectra of FAME (from WCO) shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e demonstrated the transformation of WCO into FAME.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe strong ester peaks can be seen at 1744 (the C\u0026thinsp;=\u0026thinsp;O vibration) and around 1170\u0026ndash;1197 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for O-CH\u003csub\u003e3\u003c/sub\u003e stretching vibrations. IR bands in the region 1436\u0026ndash;1464 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for CH\u003csub\u003e3\u003c/sub\u003e asymmetric bending. The peaks characteristic of the FAME are in complete agreement with those of the literature [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst was prepared and used for the catalysis of the transesterification of triglycerides in heterogeneous medium. It has the advantage of being formed from waste material industrial; it is cheap, easily prepared, and environmentally friendly. It has basic properties, a 22.5 m\u003csup\u003e2\u003c/sup\u003e.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e surface area, good chemical stability, and has been shown to be an excellent catalyst. The addition of RMS for the transesterification of WCO produced up to 100% FAME. The SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst was reused with excellent yields in four additional transesterifications of triglycerides without loss of effectiveness or the formation of by-products, such as soap. This result is different from that obtained with the basic catalysts used in FAME production. A high degree of effectiveness in all the repetitions was observed, which increases the viability of its implementation. The accumulation of industrial waste can be a reason for great concern for the environment if not properly managed. In this work, we demonstrated that waste such as RM can be of great importance in the production of new catalysts for classical reactions such as transesterification. In 2025, global red mud production from refining of alumina is projected to reach around 150\u0026nbsp;million tons. This waste byproduct of aluminum production is primarily stored in containment ponds or dams, and billions of tons are accumulated globally. This work contributes to the growing interest in valorizing RM for the recovery of resources. Only 2\u0026ndash;3% is currently effectively utilized.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003e5. Acknowledgements\u003c/h2\u003e\u003cp\u003eThe authors acknowledge the support by the SENAI CIMATEC, PRPPG/UFVJM in response to Resolu\u0026ccedil;\u0026atilde;o 15/2019, LMMA sponsored by FAPEMIG APQ-03088-2 and the Funda\u0026ccedil;\u0026atilde;o de Apoio \u0026agrave; Pesquisa do Estado de Minas Gerais - FAPEMIG (Chamada Universal), 0004022 code.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e\u003cp\u003eThe paper entitled \u0026lsquo;\u0026lsquo;The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO\u003csub\u003e2\u003c/sub\u003e for the production of biodiesel\u0026rdquo; is submitted for your kind considerations. 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Chemical Engineering Journal 165(3): 798\u0026ndash;805. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cej.2010.10.019\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2010.10.019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":": modification of silica, alkaline catalyst, reusable catalyst, environmentally friendly process, red mud, fatty acid methyl esters","lastPublishedDoi":"10.21203/rs.3.rs-7421017/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7421017/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA catalyst (SiO\u003csub\u003e2\u003c/sub\u003e-RMS) composed of basic silica gel (SiO\u003csub\u003e2\u003c/sub\u003e) with red mud solution (RMS), which is a waste alkaline solution, was prepared. The SiO\u003csub\u003e2\u003c/sub\u003e-RMS was characterized by FT-IR, SEM, XRD, XRF, BET and TG/DTA analysis. Basicity was determined using the Hammett titration. The SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst was employed for the synthesis of biodiesel (FAME - fatty acid methyl esters). Triglycerides from waste cooking oil (WCO) were treated with MeOH, 1:18 molar ratio of WCO/MeOH, at 60 \u003csup\u003eo\u003c/sup\u003eC during 90 min in the presence of 10.0% (w/w) SiO\u003csub\u003e2\u003c/sub\u003e-RMS:WCO to yield mixtures of FAMEs. The use of SiO\u003csub\u003e2\u003c/sub\u003e-RMS catalyst resulted in a 100% conversion of WCO to FAME. The catalyst was reused in four more transesterification reactions with excellent yields. The reaction times after the first reaction cycle were longer: second cycle 2:30 h, third cycle 4:30 h and fourth cycle 8:30 h. The catalyst is obtained from inexpensive, easily prepared, recyclable and environmentally friendly waste material (waste management). The protocol is highly significant from green and sustainable chemistry perspectives because the reaction involves a renewable catalyst and solvent-free reaction conditions.\u003c/p\u003e","manuscriptTitle":"The application of a solid basic catalyst produced through the adsorption of red mud solution onto SiO2 for the production of biodiesel","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-26 16:31:12","doi":"10.21203/rs.3.rs-7421017/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":"a998e1a8-c9e4-4f10-aa99-0d5c87c4bb77","owner":[],"postedDate":"August 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":53743643,"name":"Physical sciences/Chemistry/Chemical synthesis/Catalyst synthesis"},{"id":53743644,"name":"Physical sciences/Energy science and technology/Renewable energy/Bioenergy"}],"tags":[],"updatedAt":"2025-09-11T17:53:25+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-26 16:31:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7421017","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7421017","identity":"rs-7421017","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}