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This work highlights a scale-up study for microwave-assisted synthesis of solketal using ultrasonic velocity to monitor the progress of the reaction in combination with other analytical methods like GC–MS. The work aims to quantify the acetalization of glycerol to solketal using modified sulfated zirconia (Zr-S-400, Zr600-S-600, Zr600-S-400) as a catalyst. Stirring speed, catalyst dosing, and reactant ratio were optimized using response surface methodology to achieve maximum conversion. The catalyst (Zr-S-400) was doped with a 0.5 M solution of manganese acetate and nickel sulfate by the wet impregnation method, and catalytic activity was compared with the un-doped Zr-S-400. A maximum conversion of 89% was observed with an undoped Zr-S-400 catalyst. After metal doping, acidity as well as surface area decrease due to the aggregation of metals on the catalyst surface and also inside the pores of the catalyst. The conversion was further improved to 93% by increasing the acidity of the catalyst. A CSTR reactor model has been developed using the kinetic data to scale up the reaction. [ABSTRACT FROM AUTHOR]

Isosorbide, a bicyclic C6 diol, has considerable value as a precursor for the production of bio-derived polymers. Current production of isosorbide from sorbitol utilizes homogeneous acid, commonly H2SO4, creating harmful waste and complicating separation. Thus, a heterogeneous acid catalyst capable of producing isosorbide from sorbitol in high yield under mild conditions would be desirable. Reported here is a quantitative investigation of the liquid-phase dehydration of neat sorbitol over sulfated zirconia (SZ) solid acid catalysts produced via sol-gel synthesis. The catalyst preparation allows for precise surface area control (morphology) and tunable catalytic activity. The S/Zr ratio (0.1-2.0) and calcination temperature (425-625 °C) were varied to evaluate their effects on morphology, acidity, and reaction kinetics and, as a result, to optimize the catalytic system for this transformation. With the optimal SZ catalyst, complete conversion of sorbitol occurred in

Highlights: In this work, graphene nanoplates (GNPs) with a supreme medium were obtained. Pt particles (4.50 nm) were uniformly dispersed on the surface of S-ZrO2-GNP support. The Pt-Pd/S-ZrO2-GNPs exhibited higher ECSA than Pt-Pd/ZrO2-GNPs and Pt/C. Pt-Pd/S-ZrO2-GNPs exhibited higher ORR mass activity than other studied electrodes. Pt-Pd/S-ZrO2-GNPs exhibited low charge transfer resistance in EIS measurements. Developing highly active and durable Pt-based electrocatalysts is crucial for polymer electrolyte membrane fuel cells. This study focuses on the performance of oxygen reduction reaction (ORR) electrocatalysts composed of Pt-Pd alloy nanoparticles on graphene nanoplates (GNPs) anchored with sulfated zirconia nanoparticles. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Pt-Pd and S-ZrO2 are well dispersed on the surface of the GNPs. X-ray diffraction revealed that the S-ZrO2 and Pt-Pd alloy coexist in the Pt-Pd/S-ZrO2-GNP nanocomposites without affecting the crystalline lattice of Pt and the graphitic structure of the GNPs. To evaluate the electrochemical activity and reaction kinetics for ORR, we performed cyclic voltammetry, rotating disc electrode, and EIS experiments in acidic solutions at room temperature. The findings showed that Pt-Pd/S-ZrO2-GNPs exhibited a better ORR performance than the Pt-Pd catalyst on the unsulfated ZrO2-GNP support and with Pt on S-ZrO2-GNPs and commercial Pt/C. [ABSTRACT FROM AUTHOR]

This work is dedicated to the study of the effect of the synthesis conditions (drying and calcination) of sulfated zirconia on the final catalytic behavior of bifunctional composite catalysts prepared by the physical mixing of the sulfated zirconia (methanol dehydration catalyst) with Cu/ZnO/Al2O3 (CZA; methanol synthesis catalyst). The main objective was to optimize the CZA-ZrO2/SO42− composite catalyst for its use in the direct production of dimethyl ether (DME) from syngas. Sulfated zirconia aerogel (AZS) and xerogel (XZS) were prepared using the sol–gel method using different solvent evacuation conditions and calcination temperatures, while the Cu-ZnO(Al) catalyst was synthesized using the coprecipitation procedure. The effectivity of CZA-ZrO2/SO42− composite catalysts for the direct production of dimethyl ether (DME) from syngas was evaluated in a flow reactor at 250 °C and 30 bar total pressure. The characterization of the sulfated zirconia aerogels and xerogels using different techniques showed that the mesoporous aerogel (AZS0.5300) exhibited the best textural and acidic properties due to the gel drying under supercritical conditions and calcination at 300 °C. As a result, the composite catalyst CZA-AZS0.5300 exhibited seven times higher DME production than its xerogel-containing counterpart (364 vs. 52 μmolDME·min−1·gcat−1). This was attributed to its well-matched metal surface, mesoporous structure, optimal crystallite size and, most importantly, its higher acidity. [ABSTRACT FROM AUTHOR]

The effect of the support nature on the hexane isomerization reaction parameters for SiO2- and Al2O3-supported sulfated zirconia catalysts with different textural characteristics has been studied. It has been shown that a higher hexane conversion is achieved in the presence of sulfated zirconia catalysts supported on aluminas. Using IR spectroscopy of adsorbed CO, it has been found that, in the Al2O3-supported catalysts, the concentration of Brønsted acid sites (BAS) characterized by adsorbed CO with an absorption band at 2170 cm–1 and strong Lewis acid sites (LAS) characterized by adsorbed CO with absorption bands at 2210 and 2224 cm–1 is higher than that in the SiO2-supported catalysts. In the Al2O3-supported catalysts with different textural characteristics, an increase in the contribution of LAS to the total acidity leads to a significant increase in the high-octane 2,2-dimethylbutane yield and the hexane isomerization depth. [ABSTRACT FROM AUTHOR]

In the past decade, rising demand for air travel has resulted in increased carbon emissions, stimulating research into bio-jet fuel as an eco-friendly aviation alternative. This study examines the synthesis and application of cobalt-dispersed sulfated zirconia nanocatalysts for the hydroconversion of used palm cooking oil into bio-jet fuel under atmospheric conditions. The catalysts were synthesized using the wet impregnation method with varying cobalt loadings (1 %, 3 %, and 5 %) and characterized by FTIR, XRD, NH3-TPD, SAA, XRF, SEM-EDX Mapping, TEM-SAED, and XPS analyses. Hydroconversion with the Co-3/SZ catalyst yielded a 63.03 wt% liquid product, with 92.28 % bio-jet fuel selectivity and a yield of 58.17 wt%. Reusability tests for six consecutive runs further indicated that this catalyst maintained a bio-jet fuel selectivity of 56.94 % and a yield of 28.43 %, underscoring its potential as a promising candidate for bio-jet fuel production.

The catalytic efficiency of palladium supported sulfated zirconia catalysts in the isomerization of n-butane to isobutane has been studied in relation to the effects of the active site features (redox and acidic). By using the XRD, UV-DRS, and N2 adsorption methods, the structural and textural changes in the synthesized catalyst were investigated. H2-TPR was used to assess the sulfate species' type and distribution on the surface of the catalysts as well as their redox behavior. The n-butylamine titration method, NH3-TPD, and Py-FT-IR spectroscopy were used to characterize the nature/strength and kinds of acid sites. The CO-TPD was used to determine the kind of active sites. The outcomes showed that the Fe promoter in a sulfated catalyst has a major impact on the activity of n-butane isomerization. Comparing Fe–Mn and Fe alone promoted catalysts to a combination of Fe–Cr and Fe–V promoters, the activity was further increased. The findings of the characterization showed that the nature of the metal dopants influences the surface characteristics of the catalysts (their redox nature and the strength of their surface adsorption), which may be related to their ionic charge or electron density. The metal–metal synergy between the metal dopant and the zirconia matrix, which helped to improve the catalysts performance for n-butane isomerization, is primarily responsible for the active sites' adsorption capacity and reducibility. The findings of the characterization showed that the nature of metal dopants governs the surface properties of the catalysts (redox nature and surface adsorption strength), which could be related to the electron density or ionic charge. The metal–metal synergy between the metal dopant and the zirconia matrix is primarily responsible for the active sites' adsorption capacity and reducibility, which contributed to improve the catalysts' performance for n-butane isomerization. In addition, for the purpose of optimizing the Fe–V promoted sulfated zirconia catalyst, catalyst characteristics (acidity) can be adjusted by the catalyst synthesis conditions. [ABSTRACT FROM AUTHOR]

γ‐Valerolactone (GVL) is a renewable and versatile platform chemical derived from sustainable carbon feedstocks. The cascade conversion of levulinic acid into GVL requires Brønsted and Lewis acid catalysed reactions. Here, a dual‐catalyst bed configuration is demonstrated that promotes synergy between Brønsted acid sites in sulfated zirconia (SZ) and Lewis acid sites in ZrO2/SBA‐15 for the liquid phase, continuous flow esterification and subsequent catalytic transfer hydrogenation (CTH) of levulinic acid to GVL. A saturated surface sulfate monolayer, possessing a high density of strong Brønsted acid sites, was optimal for levulinic acid esterification to isopropyl levulinate over SZ (>80 % conversion). A conformal ZrO2 bilayer, deposited over a SBA‐15 mesoporous silica and possessing mixed Brønsted:Lewis acidity, catalysed CTH of the levulinate ester and subsequent dealcoholisation/cyclisation to GVL (>60 % selectivity). Maximum stable productivity for the dual‐bed was 2.2 mmolGVL.gcat.h−1 at 150 °C, significantly outperforming either catalyst alone or a physical mixture of both. Flow chemistry is a versatile approach to achieve spatial control over cascade transformations involving distinct catalytically active sites. [ABSTRACT FROM AUTHOR]

In this study, the kinetics of the esterification of acetic acid and n-propanol catalyzed by sulfated zirconia was investigated for the first time. The effect of different temperatures (60–80 °C), n-propanol to acetic acid molar ratios (1:1–3:1), catalyst loadings (5–10 wt%), and external and internal mass transfers on the acetic acid conversions was evaluated in a batch reactor. The pseudo-homogeneous, Langmuir–Hinshelwood, and Eley–Rideal models were adjusted to the experimental data to determine the reaction mechanism. The reusability and performance of the catalyst were also reported. The results demonstrated that increasing temperature, reactants molar ratio, and catalyst loadings positively affected the formation of propyl acetate. The Eley–Rideal with acetic acid adsorbed model presented the most suitable fit, suggesting that the surface reaction at the catalyst acid sites was the limiting step in the reaction mechanism. The estimated enthalpy of the reaction indicated a slightly endothermic process. The reusability of the catalyst showed a loss of activity after successive reaction cycles. The sulfated zirconia catalyst was effective for the studied esterification reaction. [ABSTRACT FROM AUTHOR]

Sulfated monoclinic zirconia (M-SZ) with high thermal stability and high catalytic performance on butane isomerization were obtained by hydrothermal method followed with sulfation treatment. The acidity of M-SZ was studied by 31P MAS NMR, with trimethylphosphine (TMP) as the probe molecule, and the catalytic performance of 1-13C-n-butane over M-SZ was monitored by 13C MAS NMR spectroscopy. Both Brønsted and Lewis acids were observed on M-SZ. Only Brønsted acid strength shows close relation to the activation energy of butane isomerization, and the M-SZ catalyst with the strongest Brønsted acid strength shows the lowest activation energy of 46.4 kJ·mol−1. The catalytic stability tests were evaluated at 673 K for 240 h, which shows that sulfated monoclinic zirconia has higher thermal stability than sulfated tetragonal zirconia. [ABSTRACT FROM AUTHOR]

The formic acid (CH2O2) decomposition over sulfated zirconia (SZ) catalysts prepared under different synthesis conditions, such as calcination temperature (500–650 °C) and sulfate loading (0–20 wt.%), was investigated. Three sulfate species (tridentate, bridging bidentate, and pyrosulfate) on the SZ catalysts were characterized by using temperature-programmed decomposition (TPDE), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The acidic properties of the SZ catalysts were investigated by the temperature-programmed desorption of iso-propanol (IPA-TPD) and pyridine-adsorbed infrared (Py-IR) spectroscopy and correlated with their catalytic properties in formic acid decomposition. The relative contributions of Brønsted and Lewis acid sites to the formic acid dehydration were compared, and optimal synthetic conditions, such as calcination temperature and sulfate loading, were proposed. [ABSTRACT FROM AUTHOR]

In the present study, highly acidic sulfated zirconia catalysts were prepared using a facile sol–gel method. A superior catalytic activity of sulfated zirconia nanomaterial for isomerization of n-hexane was observed when loaded with tungstophosphoric acid (WPA). The catalysts were fully characterized using SEM, powder XRD (PXRD), FTIR, and NH3-TPD techniques. The surface characteristics of materials were analysed using N2-adsorption isotherm (at − 196 °C). The results indicate that surface area and pore volume of zirconia were in the ranges of 93–150 m2/g and 0.08–0.31 cm3/g. Impregnation of WPA (loading of 10 to 60 wt%) on to the sulfated zirconia were conducted using the wet incipient method. The acidity of zirconia improved in the range of 0.12–0.69 mmol/g after its modification using sulfuric acid and WPA. The PXRD results revealed a monoclinic phase for the synthesized material. A fixed bed micro reactor was utilized to study the catalytic activity of the material towards isomerization of n-hexane in the temperature range of 150–250 °C, and the maximum conversion was obtained at 225 °C. [ABSTRACT FROM AUTHOR]

As a green and efficient antioxidant, nonylated diphenylamine (NDPA) is of great significance to fields such as lubricants, synthetic rubber, and plastic. However, traditional catalysts for synthesizing NDPA still exhibit drawbacks of low efficiency, equipment corrosion, non-renewability, and environmental pollution. To overcome these challenges, a series of Fe-promoted SO 4 2-/ZrO 2 catalysts were successfully developed and employed for the first time in the alkylation of DPA and NON to synthesize NDPA in our present work. Both synthesis variables of catalysts and reaction conditions were well optimized. The as-synthesized NFe 2.50 S 1.0 Z catalyst possessed excellent catalytic performance with a high yield of mono- and di-nonyl-diphenylamine, as well as better reusability and stability than activated clay. After 5 reaction cycles, over 90 % of the catalytic activity could be recovered by the thermal treatment. These observations make the Fe-promoted SO 4 2-/ZrO 2 catalyst a promising candidate for industrials. Additionally, to systematically investigate and elucidate the promoting effects of Fe on sulfated zirconia catalysts, a thorough characterization of the physicochemical properties of these catalysts was conducted through various techniques, including XRD, SEM, TEM equipped with EDX, N 2 adsorption-desorption isotherms, EA, ICP-OES, FT-IR, XPS, and NH 3 -TPD. The results indicated that the introduction of a small amount of Fe into the catalyst promoted the stabilization of T-ZrO 2 , smaller grain sizes, increased specific surface area, and strong acidity, which in turn positively affected the catalytic performance. In addition, a possible reaction mechanism of Fe-promoted SO 4 2-/ZrO 2 catalyst for catalyzing the alkylation of DPA with NON was proposed. [Display omitted] • Fe-promoted SO 4 2-/ZrO 2 was developed and applied firstly to synthesize nonylated diphenylamine by alkylation of DPA and NON. • The NFe 2.50 S 1.0 Z performed excellent reactivity and regenerability with high yields of mono- and di-nonyl-diphenylamine. • Fe promoting effects on structural and acid sites of the catalyst were thoroughly elucidated. • The mechanistic reaction pathway was proposed for the alkylation of DPA with NON over Fe-promoted SO 4 2-/ZrO 2 catalyst. [ABSTRACT FROM AUTHOR]

In the present study, perlite was thermally activated and then modified desirably to generate super acidity by loading different weight percentages of sulfated zirconia (SZ) via the two-step sol-gel method. As-prepared sulfated zirconia perlite (SZP) catalysts showed suitable catalytic potential in the vapor phase alkylation of o, m, and p-cresols with tert-butyl alcohol. The presence of crystalline phases in SZP catalysts was confirmed by XRD and FT-IR studies. TEM images revealed the nano size of the catalysts in the range of 9–25 nm. The presence of SZ on the surface of perlite was further confirmed by N2 adsorption–desorption, SEM, SEM-EDX, TGA, and UV-Vis DRS techniques. The pyridine FT-IR results confirmed the existence of Brønsted, Lewis acidic sites and their combination as super acidic catalytic active centers on the surface of catalyst utilized in the vapor phase alkylation of o, m, and p-cresols with tert-butyl alcohol. The regeneration and reusability of the preferred catalyst until the 5th reaction cycle without any considerable loss in catalytic activity demonstrated the stability of the catalyst. Comparative studies show that SZP can be regenerated and is superior compared to other catalysts previously used for other alkylation reactions with the potential for use on a large scale. [ABSTRACT FROM AUTHOR]

The platinum-loaded zirconium oxide (Pt/SO4 -2 /ZrO2) catalyst was developed for the light naphtha atoms over the reaction temperature range of 160 to 220 °C, 1 and 3 h-1 LSHV and 10 bar. Platinum improved the stability of the catalyst by preventing the formation of a coke precursor at the strong acid site of sulfur zirconium. The acidity of the catalyst was characterized by of NH3-TPD and the effect of sulfur and calcination temperature on the surface area of the final prepared zirconia was studied. The prepared catalyst shows high structural similar activity at temperature between 200 and 210°C for two types of light naphtha feed. [ABSTRACT FROM AUTHOR]

The preparation, characterization, and catalytic activity test of sulfated zirconia (SZ) modified with chromium for the hydrocracking of LDPE-based plastic waste have been investigated. SZ was prepared by wet impregnation method using zirconia nanopowder (ZrO2) and H2SO4 solution. SZ was further modified with chromium (0.5, 1.0, and 1.5% wt.%) by refluxing in aqueous solution of Cr(NO3)3·9H2O, followed by calcination and reduction processes. The prepared catalysts were characterized by SEM-Mapping and TEM. Hydrocracking of LDPE-based plastic waste was conducted at various temperatures and various catalysts. In addition, the optimum catalyst was repeatedly used for the reaction to demonstrate the stability of the catalyst. Liquid products obtained by hydrocracking were characterized by GCMS. The results showed that the morphology of the prepared catalysts had different sizes and disordered shapes after the addition of sulfate and Cr. The effective temperature for hydrocracking was 250 °C. The highest selectivity to liquid product and gasoline fraction were 40.99 and 93.42 wt.%, respectively, and were obtained over Cr/SZ with 1.0 wt.% Cr. Hydrocracking of plastic waste over the used Cr/SZ catalyst with 1.0 wt.% Cr showed that the Cr/SZ catalyst was stable and reusable up to three repetitions.

The synthesis of the nickel-loaded sulfated zirconia catalyst (Ni-SZ) and its application for the hydrocracking process have been carried out. This work has been conducted to determine the activity and selectivity from various Ni concentrations loaded on sulfated zirconia (SZ) in the hydrocracking of used palm cooking oil. The synthesis technique was preceded by sulfation of ZrO2 through incipient wetness impregnation method using H2SO4 solution and then continued with the impregnation of Ni via hydrothermal method employing NiSO4 · 6H2O precursor salt. The hydrocracking process was performed in a fix-bed microreactor at the optimum temperature (350 °C). The SZ loaded with 3 wt% of Ni (Ni-SZ 3) successfully produced the highest liquid product (44.25 wt%) and selectivity on gasoline (100 %). Besides, the gasoline fraction in the liquid product was dominated by unwanted aromatics compounds. The excellent performance of Ni-SZ 3 due to it has high acidity value, specific surface area, and Ni content. [ABSTRACT FROM AUTHOR]

Optimization studies for the esterification and transesterification of oil extracted from Croton gratissimus grains were carried out using the response surface methodology (RMS) that utilizes the central composite design (CCD) and the analysis of variance (ANOVA). A 23 full-factorial rotatable CCD for three independent variables at five levels was developed in each case, giving a total of 20 experiments needed per study. The three design factors chosen for study were the catalyst concentration, methanol-to-oil ratio, and the reaction temperature. The values of the acid value of oil (in esterification) and the percentage FAME yield and FAME purity (in transesterification) were taken as the responses of the designed experiments. In the optimization of the esterification and transesterification processes, the ANOVA showed that both quadratic regression models developed were significant. The optimum operating conditions for the esterification process that could give an optimum acid value of 2.693 mg KOH/g of oil were found to be 10.96 mass% SO42–/ZrO2 catalyst concentration, 27.60 methanol-to-oil ratio, and 64°C reaction temperature. In the optimization of the transesterification process, the model revealed that the catalyst concentration and the methanol-to-oil ratio were the terms that had the most influence on the % FAME yield and the % FAME purity of the final biodiesel product. From the combined regression model, it was established that optimum responses of the 84.51% FAME yield and 90.66% FAME purity could be achieved when operating the transesterification process at 1.439 mass% KOH catalyst concentration, 7.472 methanol-to-oil ratio, and at a temperature of 63.50°C. Furthermore, in the two-step biodiesel synthesis, a predominantly monoclinic-phased sulfated zirconia (SO42–/ZrO2) catalyst exhibited high activity in the esterification of high free fatty acid oil extracted from Croton gratissimus grains. A 91% reduction in the acid value of the Croton gratissimus oil from 21.46 mg KOH/g of oil to 2.006 mg KOH/g of oil, well below the 4 mg KOH/g of oil maximum limit, was achieved. This resulted in the high FAME yield and purity of the biodiesel produced in the subsequent catalytic transesterification of oil using KOH.

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The effect of fluorine addition to the alumina matrix used for the preparation of supported sulfated zirconia catalysts has been studied. The fluorinating agent was hydrofluoric acid. Fluorine additions affect the textural characteristics of the Al2O3 matrix and, as a consequence, the surface area of sulfated zirconia catalysts based on modified systems. The introduction of fluorine in the catalyst composition to an increase in the activity (conversion of hexane) and yield of the high-octane isomer 2,2-dimethylbutane. [ABSTRACT FROM AUTHOR]

The effect of iron and manganese additives on the textural characteristics and phase composition of the alumina matrix support was studied for sulfated zirconia catalysts of hexane isomerization. The additives introduced at the stage of plastification of aluminum hydroxide significantly improved the catalyst activity (hexane conversion and selectivity of isomerization to hexane isomers). A distinction of the modified catalysts is the formation of acid sites in a ratio of LAS : BAS ≥ 2, which increase the yield of isomers and especially of high-octane 2,2-dimethylbutane. [ABSTRACT FROM AUTHOR]

[Display omitted] • SO 4 /ZrO 2 were prepared by a simple wet impregnation technique. • A simple pseudo-homogeneous kinetic expression was developed and validated. • The activation energy of the reaction was estimated as 88.1 ± 8.9 kJ/mol. • Water largely affects the reaction rate and the conversion at equilibrium state. In this work, a series of acid catalysts were synthetized from a commercial zirconium oxide sulfated with a 0.5 M H 2 SO 4 solution by wet impregnation. The characterization results show a correlation between the calcination temperature and the acid sites generated on the materials. Among the catalysts prepared, the sulfated zirconia calcined in air at 400 °C (Zr-S-400), with a molar ratio S/Zr = 0.23 was the most active one due to its larger acid density and greater acid strength caused by the generation of new Brönsted sites. The Zr-S-400 catalyst exhibited an initial reaction rate of 0.0497 mol.min−1. g−1, and achieved a glycerol conversion of 80 % in 1 h of reaction at 40 °C (glycerol:acetone molar ratio = 1:6). The Zr-S-400 material remained stable after four catalytic cycles, demonstrating the stability of the superficial sulfate species (S/Zr ∼ 0.2). In addition, the thermodynamics and kinetics of the reaction were evaluated, as well as the influence of some operating conditions such as the molar ratio of reactants and the water content in the reaction mixture. The following standard molar reaction properties were obtained: ΔHº = -11.6 ± 1.1 kJ.mol−1 and ΔGº = 4.0 ± 0.1 kJ.mol−1. Taking into account that the adsorption of water on this catalyst did not affect the number of acid sites available, a simple pseudo-homogeneous kinetic expression was developed and successfully adjusted to the experimental data in the range under study. Based on this model, the estimated activation energy of the reaction was 88.1 ± 8.9 kJ.mol−1. [ABSTRACT FROM AUTHOR]

The proton exchange membrane is the main component of direct methanol fuel cells (DMFCs). It has binary function of separating oxidant and fuels, besides transporting protons. In this study, a binary polymer blend is formulated from inexpensive and ecofriendly polymers, such as iota carrageenan (IC) and poly vinyl alcohol (PVA). Super acidic sulfated zirconia (SO4ZrO2) was synthesized from an one pot, solvent free and simple calcination method and later embedded as a doping agent into the polymeric matrix with a percentage of 1–7.5 wt. %. The membranes formed were characterized by FTIR, TGA, DSC and XRD. The results revealed that, the oxidative stability and mechanical properties were enhanced with increasing doping addition due to an increase in numbers of hydrogen bonds formed between the polymers functional groups and oxygen functional groups of SO4 ZrO2. In addition to, the membrane with doping ratio of 7.5 wt. % of SO4 ZrO2 achieved methanol permeability of 1.95 × 10–7 cm2 s−1 which much less than Nafion 117 (14.1 × 10–7 cm2 s−1) and ionic conductivity of 22.3 mS cm−1 which is close to Nafion 117 (34 mS cm−1). [ABSTRACT FROM AUTHOR]

Inorganic-organic composites based on the foil and standard RALEX® cation-exchange heterogeneous membranes (Mega a.s., Czech Republic) were prepared by in situ modification with sulfated zirconia (S-ZrO2). The composite membranes were characterized by SEM, TGA, X-ray diffraction, and FTIR spectroscopy. The effect of S-ZrO2 doping on membrane transport properties was studied using measurements of water uptake, ion-exchange capacity, conductivity, cation diffusion, hydrogen permeability, current-voltage characteristics, and membrane specific permselectivity (Ca2+/Na+). The S-ZrO2 incorporation leads to an increase in conductivity and permselectivity of the composite membranes. The proton conductivity of the S-ZrO2-doped foil membrane (0.0316 S/cm at 30°С) is 4 times higher than that of the pristine membrane. The Ca2+/Na+ permselectivity of the standard RALEX® CM membrane doped by S-ZrO2 reaches 3.8 at low current densities. Moreover, the composite membranes retain their selectivity during the long-term tests (> 50 h continuous electrodialysis). The sulfated zirconia doping of heterogeneous membranes demonstrated an excellent separation efficiency that can be used in wastewater treatment, desalination, and related electromembrane separation processes as well as to reduce scaling of electrodialysis modules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Methane can be dehydroaromatized using Mo supported on sulfated zirconia (SZ) catalyst. • Acidity and coke resistivity of sulfated zirconia can be further enhanced by the addition of promoters like Pt, Pd, Cr. • An increase in target product yield is observed for MDHA with the addition of promoters to Mo/SZ. • Deactivation due to carbon deposition is eminent but is further reduced with the presence of Pt, Pd, Cr promoters. Methane dehydroaromatization (MDHA) is a direct approach of converting methane to aromatics and H 2. Mo doped HZSM-5/HMCM-22 are considered as the most active and stable catalysts for MDHA. It is generally thought to involve a process in which Mo oxides convert to MoC y /MoO x C y active species that activate CH 4 to C 2 H y dimers. In a final step, C 2 H y dimers undergo oligomerization on zeolite Brønsted acid sites. An alternative solid acid support is sulfated zirconia (SZ), which is known to contain strong Brønsted acidity. Carbon deposition is significant. Here, MDHA is compared to Pt, Pd, Cr, W promoters for Mo/SZ catalyst to decrease carbon deposition and increase aromatics selectivity. The catalysts are characterized using BET, SEM-EDS, DRIFTS, Raman Spectroscopy, XRD, XANES and TPO. Activity varied with different promoters. Less carbon deposition and slower deactivation were observed for Pd, Pt and Cr promoted catalysts, while W promotion resulted in more carbon deposition and rapid deactivation Compared to Pd and W promotion, Pt and Cr increased higher aromatics selectivity for Mo/SZ. [ABSTRACT FROM AUTHOR]

Corncob is an abundant agricultural residue containing high content of hemicellulose. In this paper, the hemicellulosic hydrolysate was prepared from the hydrolysis of corncob using the solid acid sulfated zirconia as a catalyst. According to response surface analysis experiments, the optimum conditions for preparing hemicellulosic hydrolysate catalyzed by sulfated zirconia were determined as follows: solid (sulfated zirconia)–solid (corncob) ratio was 0.33, solid (corncob)–liquid (water) ratio was 0.09, temperature was 153 °C, and time was 5.3 h. Under the optimized conditions, the soluble sugar concentration was 30.12 g/L with a yield of 033 g/g corncob. Subsequently, xylitol production from the resulting hemicellulosic hydrolysate was demonstrated by Candida tropicalis, and results showed that the yield of xylitol from the hemicellulosic hydrolysate could be significantly improved on a basis of decolorization and detoxification before fermentation. The maximum yield of xylitol from the hemicellulosic hydrolysate fermented by C. tropicalis was 0.76 g/g. This study provides a new attempt for xylitol production from the hemicellulosic hydrolysate. [ABSTRACT FROM AUTHOR]

Metal‐reinforced sulfonic‐acid‐modified zirconia catalysts were successfully prepared and used to remove trace olefins from aromatics in a fixed‐bed reactor. Catalysts were characterized by ICP‐OES, N2 adsorption–desorption, X‐ray diffraction, thermogravimetric analysis (TGA), and pyridine‐FTIR spectroscopy. Different metals and calcination temperatures had great influence on the catalytic activity. Alumina‐reinforced sulfated zirconia exhibited outstanding catalytic performance, stable regeneration activity, and giant surface area, and are promising in industrial catalysis. TGA showed that the decomposition of methyl could be attributed to Brønsted acid sites, and pyridine‐FTIR spectroscopy proved the weak Brønsted sites on these synthesized metal‐reinforced sulfated zirconia. Also, a relation between the reaction rate and weak Brønsted acid density is proposed. [ABSTRACT FROM AUTHOR]

This study reports experimental data and kinetic modeling of acetic acid esterification with n‐pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well‐mixed batch reactor at different temperatures (50‐80°C), n‐pentanol to acid molar ratios (1:1‐3:1), and catalyst loadings (5‐10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo‐homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n‐pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol−1, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism. [ABSTRACT FROM AUTHOR]

The need for valuable hydrocarbons is now at its peak. Methane is an abundant source of natural gas, and is well‐studied as a feedstock for producing heavier hydrocarbons of higher value. A number of processes are well‐studied, including methane dehydroaromatization (MDHA). This is a direct methane conversion process, eliminating the need for a syngas step while producing both benzene and hydrogen. [ABSTRACT FROM AUTHOR]

Distinct crystal phases of an oxide affect the configuration of surface atoms, which might further affect coordination with sulfate during sulfonation for the preparation of SO42−/MxOy type of acid catalyst. Herein, such an effect is investigated with zirconia of the tetragonal or monoclinic phase as the model catalysts. The results show that sulfonation inhibits the transformation of zirconia from the tetragonal phase to the monoclinic phase, whereas the varied phase of zirconia also affects the bonding patterns of sulfate species with zirconia in sulfonation. The sulfated zirconia of monoclinic phase contains more abundant acidic sites and more Brønsted acid sites than that of sulfated zirconia of tetragonal phase. Consequently, the sulfated zirconia of monoclinic phase is more active than the sulfated zirconia of tetragonal phase for the conversion of furfuryl alcohol in ethanol and conversion of fructose in dimethyl sulfoxide, achieving the yield of ethyl levulinate of 96.4% and a high yield of 5‐hydroxymethylfurfural. The sulfated zirconia is not stable in protic solvent due to the leaching of sulfur species and the change in configurations of the sulfate species and the zirconium species, but in the aprotic solvent, they show good stability and recyclability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The sulfated zirconia with Cu modification (CSZ) were synthesized by one-step method. • CSZ show superior performance to commercial Pt catalysts for i-butane normalization. • Cu content of CSZ show volcano-type relationship with n-butane yield. • Lewis active sites density is regarded as descriptor to corelate n-butane yield. Sulfated zirconia (SO 4 2-/ZrO 2) has been reported as an efficient and stable solid superacid catalyst for normalizing i-butane to n-butane, and may potentially substitute Pt-based catalysts. In this work, sulfated zirconia with Cu addition (Cu-SO 4 2-/ZrO 2) is prepared through a one-step method and exhibits comparable performance to commercial Pt-Cl/Al 2 O 3 , with an i-butane average conversion of 43.8% and n-butane average selectivity as high as 86.1%, while maintaining a stable n-butane yield for up to 120 hours. The relationship between Cu-promoter-induced physicochemical properties and catalytic performance for sulfated zirconia catalysts is investigated in detail, with the help of XPS, NH 3 -TPD, pyridine-IR, and density functional theory calculation. A volcano-type relationship is found between Cu content and n-butane yield, where n-butane yield first increases from 32.23% to 37.71%, and then decreases to 29.56%, with the gradual increase of Cu content. The moderate Cu species additive is beneficial to release Zr Lewis acid site from sulfate and increase its Lewis acid density, which accounts for its excellent catalytic selectivity for i-butane normalization. The excess Cu promoter covers the exposed Zr Lewis active sites, leading to the decayed i-butane conversion. Therefore, Lewis active sites density is regarded as descriptor to corelate n-butane yield, accounting for the volcano relationship between Cu content and n-butane yield for Cu-SO 4 2-/ZrO 2. This work demonstrates the feasibility of Cu modification and provides insight into the promotion mechanism, which may be extended to other solid superacid catalysts beyond sulfated zirconia. [ABSTRACT FROM AUTHOR]

A deep eutectic solvent (DES) was used to synthesize a sulfated zirconia catalyst, which stands out for its large specific surface area and high density of strong acidic sites. The unique hydrogen bonding and coordination capabilities of the DES were crucial in forming this catalyst. This DES-based catalyst shows significantly improved efficiency in producing alkyl glucosides from glucose and alkyl alcohols compared to those SZ made via traditional aqueous precipitation methods. The DES is believed to stabilize defect sites on the zirconia precursor during catalyst formation. Additionally, some DES residue remaining after acidification contributes to creating microporosity. This results in a marked increase in both the catalyst's specific surface area and the number of strong acidic sites, enhancing its overall catalytic performance. [Display omitted] In this study, a deep eutectic solvent (DES) system, comprising choline chloride and urea, was employed to synthesize sulfated zirconia (SZ) solid acid catalysts. The characteristics and efficacy of the SZ catalysts synthesized using this DES system were meticulously evaluated using a suite of analytical techniques, including nitrogen sorption, X-ray diffraction (XRD), pyridine adsorption infrared spectroscopy (Py-IR), X-ray photoelectron spectroscopy (XPS), and ammonia temperature-programmed desorption (NH 3 -TPD). The research also focused on analyzing the distinctive role and characteristics of the DES in the preparation of SZ. When compared with conventional aqueous phase precipitation methods, the SZ catalysts synthesized in the DES environment exhibited enhanced properties, such as an increased specific surface area, a higher density of acidic sites, and a larger proportion of potent acid centers. These improvements led to augmented catalytic activity in the reaction between alkyl alcohols and glucose. Moreover, the SZ catalysts prepared with DES demonstrated superior reaction stability and reusability, which can be attributed to the well-dispersed strong acid centers. The study uncovered that the components of the DES significantly contribute as microporous templating agents during the formation of SZ, assisting in the stabilization of the defect sites in the zirconia precursor. These components eventually evolved into prominently exposed surface strong acid centers during the stages of acidification and calcination, enhancing mass transfer efficiency and the acidic catalytic properties of the catalysts. [ABSTRACT FROM AUTHOR]

Palladium-containing catalyst based on binder-free granular sulfated zirconium oxide for n-butane isomerization has been investigated. It has been found that Pd content of 0.2–1.0 wt % slightly influences textural characteristics and other physicochemical properties of bifunctional catalysts; however, it determines their activity and selectivity in the reaction studied, with the optimal palladium content being 0.5 wt %. Parameters of the isomerization process have been studied depending on the composition of industrial n-butane fractions. It has been shown that impurities of isobutane, propane, neopentane, isopentane and pentane in an amount of no more than 2% do not exert a effect on isobutane production; nonetheless, the conversion of n-butane and selectivity for isobutane both increase when more pure n-butane fractions are used. It has been found that the process for isobutane production by isomerization of the n-butane fraction under the optimal conditions at H2 /n-C4 = 0.1 and 140–150°C makes it possible to obtain a high isobutane yield (up to 52 wt %) and avoid the undue formation of С1–С3 alkanes. [ABSTRACT FROM AUTHOR]

The complete oxidation of ethane in the presence of catalysts containing 1, 3, and 5 wt % CuO deposited on four supports (zirconia, sulfated zirconia, tungstated zirconia, and La2O3-stabilized zirconia) is studied. The supports and the catalysts are characterized via BET, XRD, and thermal analysis. It is shown that 100% conversion of ethane is achieved even at a temperature of 300°C. It is found that the temperature of 100% conversion falls upon an increase in the copper content; the lowest temperature is obtained for catalysts based on unmodified zirconia. With respect to catalytic activity, the samples with the highest copper content are in the order 5%Cu/ZrO2 > 5%Cu/5%La2O3/ZrO2 > 5%Cu/15%WO3/ZrO2 > 5%Cu/5%SO4/ZrO2. The temperatures of 100% ethane conversion for these catalysts are 305, 385, 410, and 419°C, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A stable mesoporous super-acid catalyst is prepared by using double-chain quaternary ammonium. • 3-Fold ionic sulfates absorbed on the surface promote the stability of active sites. • Brönsted acid sites in the catalyst are active phases. • The position of H+ lies on the configuration of sulfate species. • Oil conversion is still 86.5% after five (trans)esterification runs at 140 °C. Abstract Sulfated zirconia is used as solid acid catalyst in simultaneous (trans)esterification of low quality feedstock with free fatty acids for biodiesel production. However, its widespread application in catalytic reaction is limited by its framework and catalytic instability. Therefore, we prepared a stable sulfated zirconia catalyst with mesoporous structure and tetragonal phase nanocrystalline by using dioctyl dimethyl ammonium chloride as a template. The mesoporous sulfated zirconia shows more than 85% conversion of soybean oil after five recycle runs at 140 °C in both the transesterification and the simultaneous (trans)esterification. A comparison of physicochemical properties of the fresh and the reused catalysts shows that covalent sulfates combined with the sufficient of surface defective sites are the basis of the structural stability. With higher sulfate concentration, the ionic sulfate species absorbed on the low-index plane induce the production of abundant Brönsted acid sites, which are responsible for the activity in the transesterification or esterification, while the loss of these active sulfate species during the reaction is the intrinsic reason for the catalyst deactivation. Furthermore, simulation calculations confirm that position of two H+ affects the configurations of SO 4 2− and the most stable 3-fold coordinated configuration sulfates play a dominant role in the formation of stronger Brönsted acid sites. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sulfated Zirconia (SZ) is used as an acid support in CH 4 dehydroaromatization as compared to conventional H-ZSM-5. • Mo/SZ is characterized using XPS, XANES, and HRTEM. • Pyridine DRIFTS and NH 3 -TPD confirms the presence and the nature of acid sites. • Mo/SZ catalyst is more selective to heavier aromatics such as naphthalene as compared to Mo/H-ZSM-5. • Mo/SZ can be used in dehydrogenation, hydroconversion, or other light alkane aromatization reactions. Abstract The shale gas revolution has strongly impacted the world by providing a significant incentive for research in natural gas conversion. Natural gas is becoming an important feedstock for the production of valuable chemicals. Dehydroaromatization (DHA) is an important non-oxidative conversion route for methane conversion, and Mo doped on the H-ZSM-5 or H-MCM-22 have been well-studied for this reaction. In these catalysts, Mo sites activate CH 4 to form dimeric species that are subsequently oligomerized on the strong Brønsted acid sites. In the present study, Mo is doped on solid sulfated zirconia (SZ) to create a catalyst similar to Mo/H-ZSM-5, but with a different solid acid. Despite the logic of using SZ as the acid, we are aware of no systematic study of Mo/SZ catalysts for this reaction. These catalysts were characterized using Raman, XPS, DRIFTS, SEM-EDS, HRTEM, XRD, XANES and other temperature programmed techniques. Raman spectra confirmed the formation of Mo = O and O Mo O bonds on the surface of SZ support. DRIFTS confirmed that there was little difference in acid sites when Mo was doped on SZ, except at higher Mo loadings. XPS, XANES, and HRTEM analysis showed that MoO 3 is converted to MoO x C y and is further converted to Mo 2 C as the reaction progresses. Further, these catalysts were evaluated for methane DHA reaction. All of these catalysts showed methane conversions of 5–20 % at temperatures of 600–700 °C. In each case, the catalysts deactivated steadily, attributable to strong coking on the surface, as confirmed with TPO. A comparison with literature showed that Mo/SZ has comparable activity to Mo/H-ZSM-5 at around 650 °C–675 °C temperature range. Further, Mo/SZ was more selective towards heavier aromatics such as naphthalene and coke as compared to Mo/H-ZSM-5 at 700 °C, which is more selective towards benzene. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel sulfated zirconia (SZ) prepared by impregnation of high surface area ZrO 2 with H 2 SO 4. • CO 2 -to-DME over a hybrid catalyst containing CuO-ZnO-ZrO 2 and SZ. • Maximum DME yield was achieved at monolayer coverage of S. • Novel sulfated zirconia (SZ) was more active and stable than a conventional sulfated zirconia. • Increasing 2-fold coordinated sulfated ions caused a faster catalyst deactivation. Abstract A series of sulfated zirconia (SZ) catalysts were prepared by impregnation of high surface area mesoporous ZrO 2 with different H 2 SO 4 concentrations. The resulting SZ catalysts were admixed with a CuO-ZnO-ZrO 2 (CZZ) catalyst for direct CO 2 -to-dimethyl ether (DME) hydrogenation. A sulfated zirconia prepared via sulfation method (SZS), a commercial Zr(SO 4) 2 and HZSM-5 catalysts were employed for purpose of comparison. TGA analysis revealed that the interaction between sulfated ions and the ZrO 2 surface changed with S contents. At low S content, sulfate ions with tridentate coordination was mainly formed on the ZrO 2 surface. Increasing S contents led to an increase of 2-fold coordinated configuration of sulfate ions. The plot of S content against sulfuric concentration indicated that a saturated sulfate monolayer was obtained at 1 M H 2 SO 4 concentration. During the 48 h time-on-stream experiment, the CZZ-Zr(SO 4) 2 and CZZ-SZS showed a substantial decrease in DME yield ca. 24.24% and 28.54% compared to their initial activities, respectively, while the CZZ-1SZ catalyst exhibited not only higher activity but also much greater durability, experiencing only a 11.8% reduction under identical reaction conditions. The higher activity of CZZ-1SZ catalyst was attributed to a monolayer coverage of sulfate ions over the high surface area ZrO 2 , providing most of active sites to be accessible by methanol, while the strong interaction between sulfate ions bonded to the ZrO 2 surface could lead to the higher stability of the CZZ-1SZ catalyst. [ABSTRACT FROM AUTHOR]

A series of ordered mesoporous sulfated zirconia (OMSZ) with different calcination temperatures (400-650 °C) have been synthesized by a self-assembly method using zirconium n-propoxide as raw material, P123 (EO20PO70EO20) as structure-directing agent and ammonium sulfate as sulfonating agent. The transmission electron microscopy results indicated that the OMSZ had the ordered mesoporous structure and the X-ray diffraction analysis further revealed that the OMSZ had hexagonal ordering structure. The N2-BET results showed that the OMSZ were mesoporous materials and, when the calcination temperature was 500 °C, the BET surface area could reach 183 m2/g. Temperature-programed desorption of NH3 (NH3-TPD) analysis confirmed that the OMSZ possessed a superacid when the calcination temperature was higher than 450 °C. FTIR-pyridine adsorption results indicated that the OMSZ surfaces were mainly the Lewis acid sites. The catalytic activity of OMSZ was observed for transesterification of waste frying oil, and 92% of yield could be obtained after 6 h at 200 °C. [ABSTRACT FROM AUTHOR]

Highlights • The prepared 2-SZ-HM-550 shows higher activity than SZ and HZSM, achieving a HMF yield up to 61%. Abstract Production of 5-hydroxymethylfurfural (HMF) from glucose with high yield remains a big challenge. Thereinto, assembling catalysts with outstanding performance is the bottleneck at the current stage. In this study, effective catalysts were synthesized by loading SO 4 2−/ZrO 2 (SZ) on a series of H+ zeolites to investigate the catalytic dehydration of glucose into HMF. Among all the catalysts applied, 2-SZ-HM-550 (HZSM-5 with Si/Al molar ratios of 80∼150, calcined at 550 °C) gave the yields of HMF 41.32%, 61.14%, 54.67% and 40.71% in 4 applied reaction systems, respectively. Moreover, HMF with desirable yield was obtained while other carbohydrates were dehydrated catalyzed by 2-SZ-HM-550, such as fructose, sucrose, inulin and starch. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis method-resulting molecular structure stability/structure/reactivity relationships are discussed. • Diversity of sulfate zirconia preparation methods results in variety of the active site structures. • Hydrocarbon reaction mechanisms on sulfate zirconia mostly rely on homogeneous mechanisms. Abstract This article critically reviews the literature on sulfated zirconia catalysts for variety of important hydrocarbon and oxygenate reactions including ethylene dimerization, isomerization, alkylation and esterification. The catalyst synthesis method-resulting molecular structure relationships, stability and reactive transformations of the active site in response to gas phase environment, reaction mechanisms, reaction intermediates, the corresponding kinetics and effect of some popular promoters are covered. Key structural features of the active sites have been extensively investigated but the conclusive structure is yet to be determined due to the diversity of the preparation methods (nature and crystallinity of the support, sulfate deposition method, sulfate coverage) as well as the diversity of the experimental conditions used during the spectroscopic determination. Similarly, the effect of the promoters and the synergistic effects of the promoter/sulfate sites in the presence of hydrocarbons are not well-defined. Finally, multiple theories exist for the reactive mechanisms on sulfated zirconia but most rely on the homogeneous reaction mechanisms, such as those for ethylene dimerization and butane alkylation with butane. Collectively, these show the lack of a fundamental understanding and the need of modern catalysis studies of this important catalytic system. [ABSTRACT FROM AUTHOR]

Abstract In this work, sulfated zirconia (SZ) was prepared by a solvent-free method, ammonium sulfate ((NH 4) 2 SO 4) and sulfamic acid (NH 2 SO 3 H) were as sulfur sources, respectively. The resulting catalysts were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), N 2 adsorption–desorption isotherms, inductively coupled plasma (ICP) and pyridine-FTIR. The characterization of the catalysts revealed that SZ prepared with (NH 4) 2 SO 4 as sulfur source contained more Lewis acid sites and less Brønsted acid sites. The effects of sulfur sources on the catalytic activity of catalysts were studied. Catalytic testing showed that SZ prepared with (NH 4) 2 SO 4 as sulfur source had a better catalytic performance for removing trace olefins from aromatics. [ABSTRACT FROM AUTHOR]

Abstract: Sulfated zirconia catalysts were prepared using the sol-gel process. Hydrolysis water was produced in situ. The effects of the zirconium precursor on the physicochemical properties and the acidity of the solids have been investigated. The prepared catalysts were characterized by XRD, Raman spectroscopy, XPS, FTIR of adsorbed pyridine, physisorption of N2 at 77 K, and TPR-H2-MS. Pt-promoted catalysts were tested for n-hexane isomerization reaction and the influence of Pt amount on the stability was studied. Obtained solids exhibit low specific surface areas and narrow pore size distributions. In addition, the metastable tetragonal phase of ZrO2 was stabilized at a relatively high temperature. The acidity of catalysts prepared from different zirconium alkoxides and the magnitude of interaction between zirconia and sulfate species are compared and discussed.Sulfated zirconia catalysts were prepared using the sol-gel process. Hydrolysis water was produced in situ. The effects of the zirconium precursor have been investigated. The prepared catalysts were characterized by XRD, Raman spectroscopy, XPS, FTIR of adsorbed pyridine, physisorption of N2 at 77 K, and TPR-H2-MS. Pt-promoted catalysts were tested for n-hexane isomerization reaction. The metastable tetragonal phase of ZrO2 is stabilized at 833 K.The initial catalytic activity of sulfated zirconia is closely related to the density of Lewis acid sites.The use of zirconium propoxide leads to better retention of sulfate groups.The increase in the amount of Pt leads to a greater loss of sulfur. [ABSTRACT FROM AUTHOR]

Lignocellulose can help produce fuels in biorefineries through its fractionated components such as cellulose, hemicelluloses, and lignin. For instance, hemicellulose-derived xylose has been studied for obtaining petroleum-substituting fuels. Therefore, in this study, catalytic hydroalkylation/alkylation (HAA) of xylose-derived 2-methylfuran (2-MF) with butanal was targeted to selectively produce high-carbon-number diesel fuels. To that end, silica–alumina (SiAl) aerogels with different Si/Al ratios and a series of sulfated zirconia (SZ) compounds calcined at various temperatures were prepared as catalysts to overcome the limitations of conventional hazardous homogeneous acid catalysts. The activity of the SiAl catalysts in forming the desired HAA product, 5,5-bissylvylbutane (denoted as BB), was found to be directly related to the number of acid sites and acid density. Moreover, increasing the Si/Al molar ratio, which reduced the acid density and number of acid sites, led to lower 2-MF conversions and BB yields. The optimal 2-MF conversion and BB yield with the SiAl catalysts (67 % and 45 %, respectively) were achieved using a Si/Al ratio of 8:2 mol/mol. Furthermore, SZ calcined at 700 °C (denoted as SZ-700) exhibited the highest activity among the SZ catalysts (72 % 2-MF conversion, 63 % BB yield), despite having the fewest acid sites and lowest acid density. This was presumably because of the physical structure of SZ-700, which featured mixed monoclinic and tetragonal phases, many oxygen vacancies, and a large accessible external surface area, which facilitated the HAA reactions. Hydrogenation and hydrodeoxygenation (HDO) of BB were performed thereafter using Pd/C and Ru/SiO 2 –Al 2 O 3 catalysts, respectively. The resulting deoxygenated hydrocarbons comprised 15.1 % light hydrocarbons (C 4 –C 8) and 83.1 % heavier hydrocarbons (C 9 –C 20). Simulated distillation analysis of the post-HDO product distribution indicated that the liquid-phase product contained 70 % high-carbon-number bio-aviation fuels. [Display omitted] • Hydroalkylation/alkylation using silica-alumin aerogels and sulfated zirconia. • Increasing acidity improved the reaction on silica-alumina aerogels. • Crystal structures determined the activity of sulfated zirconia. • Hydrodeoxygenation of condensates produced gasoline- and diesel-like fuels. • Catalysts were degraded in the batch reaction. [ABSTRACT FROM AUTHOR]