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Highlights: [•] A series of sulfated Si-doped ZrO2 were synthesized and characterized in detail. [•] Ethyl levulinate was produced from levulinic acid and ethanol with high yields. [•] The catalytic activity far outperformed that of the conventional sulfated zirconia. [•] A distinct correlation was observed between the activity and textural properties. [•] The catalyst could afford levulinate ester directly from cellulosic sugars. [ABSTRACT FROM AUTHOR]

In this work, the performance of sulfated zirconia catalyst used in the synthesis of biodiesel by esterification of oleic acid was studied. For catalyst preparation the zirconium dioxide (ZrO⧠) by Aldrich was used as precursor. The sulfated zirconia obtained was calcined for 3 hours at different temperatures (200, 400, 600 and 700 °C) in an oxygen atmosphere. Each of the calcination conditions generated a sample of catalyst, which was used in the esterification reaction. The esterification reaction was carried out using reagents such as oleic acid and methanol at a molar ratio 1:20. The sulfated zirconia catalyst was used in the reaction in various proportions by weight relative to the weight of oleic acid (0.5, 1.0, 3.0 and 5%). The analysis of methyl ester conversion was performed by gas chromatography and mass spectrometry (CGMS) and the percentage area of the characteristic peaks as methyl oleate was quantified. A characterization of sulfated zirconia was also performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Finally, the catalyst performance was studied in the reduction of the acid index (AI) and the conversion of free fatty acids of oleic acid and compared to other commonly used catalyst for this purpose, which is concentrated sulfuric acid (H2SO4). [ABSTRACT FROM AUTHOR]

The condensation reaction of 2-aminobenzamide and aldehydes or ketones was investigated in the presence of nanocrystalline sulfated zirconia (SO/ZrO) as solid acid catalyst. SO/ZrO nanoparticles with different calcination temperatures were prepared and characterized by XRD, FT-IR and SEM techniques. The results confirm good stabilization of tetragonal phase of zirconia in the presence of sulfate. The reusability experiments show partial deactivation of the catalyst due to leaching of the sulfate and coke deposition on the catalyst. [ABSTRACT FROM AUTHOR]

X-ray absorption of inter-atom transitions (Zr L-, O K- and S K-edges) were used to probe the interaction of sulfate with nanoparticles of ZrO supported on multi-walled carbon nanotubes with the goal of describing the electronic interaction of formation of acid sites on sulfated zirconia. The changes in intensity at the Zr-O-S interface are first interpreted as charge transfer within various molecular orbitals using spectra of all three elements (Zr L-, O K- and S K-edges). An alternative interpretation of intensity, particularly for the sulfate precursor, is made in terms of charge distribution over molecular orbitals of different size and shape that result from the sulfate precursor decomposition and/or interaction with zirconia. Graphical Abstract: Zr L-edge XANES of S-ZrO/MWCNT annealed at different temperatures (250 °C ~ 550 °C), showing interaction between Zr and S.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Sulfated zirconia (S-ZrO) is a versatile solid acid catalyst that has wide application in hydrocarbon conversion reactions. In our previous work, we have developed well-dispersed ZrO nanoparticles supported on multi-walled carbon nanotubes (MWCNT) to form a ZrO/MWCNT composite, which, upon sulfation, becomes a S-ZrO/MWCNT solid acid catalyst. While X-ray absorption spectroscopy (XAS) of this composite at the C, O, Zr K-edges has been well studied in our previous reports, XAS at the S K-edge is complicated by the Zr L-edges that bracket the S K-edge. In this study, we have used conventional S XANES, together with first-derivative and third-derivative analysis, to probe the sulfur species formed during the catalyst preparation and their interaction with Zr. We have also designed combined Zr and S XANES, which spans 400 eV and covers all three Zr L-edges and the S K-edge, to study the Zr and S interaction. Such use of multiple-edge XANES to study the S-ZrO system at low X-ray energy (2,200-2,600 eV) was first reported in the previous publication of our research group, and in this paper we elaborate on the comprehensive study of our catalyst system using this method. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Highlights: [•] Chlorosulfonic acid modified zirconia was applied in biodiesel production. [•] FAME yield reached 100% consecutively for 5 cycles even under mild conditions. [•] Catalyst synthesis condition-activities relations were studied. [ABSTRACT FROM AUTHOR]

Abstract: A series of sulfated zirconia nanoparticles (abbreviated to SZNP) with high surface area and mesostructure have been synthesized by using sulfate-contained anion surfactants (SDS and SCS) both as a template and a sulfating agent via one-step liquid-crystal template (LCT) route. In light of N2 adsorption–desorption, XRD and FT-IR analyses, it can be concluded that SDS is in favor of the mesostructure formation as well as the inhibition of ZrO2 phase transformation from tetragonal to monoclinic with respect to SCS. The optimal molar ratio of Zr/S is 1:1, which lead to the largest BET surface area. It is well-demonstrated by FT-IR, NH3-TPD together with transesterification reaction that SO4 2− anion, originated from the hydrophilic moieties of templates, can be easily incorporated into ZrO2 to form SZNP with super acidity, and the formation mechanism is also illustrated. Catalytic data exhibiting the yield of fatty acid methyl ester (FAME) in transesterification of soybean oil with methanol is in the following order: SZNP12-(550)-1.0 >SZNP16-(550)-1.0 >TSZ(550). [Copyright &y& Elsevier]

This work studies the effect of the evacuation mode of the solvent to optimize the catalytic performances of sulfated zirconia doped with nickel prepared by the sol gel method in one step. Aerogel and xerogel catalysts exhibit different textural, structural and catalytic properties at various calcination temperatures. Aerogels, obtained by drying under supercritical conditions of solvent, exhibit a developed specific surface area and stabilize zirconia tetragonal phase before heating and even at high calcination temperature. However, xerogels obtained by ordinary drying in an oven are amorphous and has a low surface area and weak porosity. XPS spectroscopy shows that the nickel in aerogels is more reducible than those in xerogels. Aerogels exhibit higher activity than the xerogels, in the n-hexane isomerization reaction. [ABSTRACT FROM AUTHOR]

Abstract: Ceria catalysts supported on sulfated zirconia showed a remarkable resistance towards alkali metal poisoning in selective catalytic reduction of NO by NH3. TPD results revealed sulfation treatment of supports produced massive acid sites on the surface of catalysts. Adequate acidity was of importance for the enhanced resistance to alkali metal ions. The introduction of potassium did not affect the crystalline phases and morphology of catalysts, but it could lead to higher surface areas of samples. [Copyright &y& Elsevier]

Sulfated zirconia (SZ) nanoparticles (NPs) were successfully synthesized and deposited via chemical route called sol-gel technique. The structural, morphological, and optical properties the samples were investigated by X-ray diffraction (XRD), Energy Dispersive X-ray Spectrometry (EDX), canning Electron Microscopy (SEM) and UV-visible spectrophotometer. Results show that the transmittance of the samples increased from visible region (VIS) to infrared (UV) region. It also showed that the transmittance of the samples changed with the precursor's concentrations. Furthermore, the samples showed very low absorbance which decreased toward the infrared region. The nanoparticles have wide energy bandgap that varied from 3.80 to 4.00±0.05 eV and is therefore good candidate for solar cell and solar thermal applications. It also presents an attractive alternative material for biomedical implants due to its biocompatibility and mechanical strength. [ABSTRACT FROM AUTHOR]

Sulfated zirconia was promoted with alumina and yttria in order to improve catalyst isomerization behaviors. The n-hexane hydroisomerization reaction was carried out in a continuous flow fixed-bed reactor for 80 h on stream to evaluate catalyst reaction stability. The catalyst was characterized by XRD, TGA, H2-TPR, and NH3-TPD technologies in order to investigate the crystalline structure, sulfur content, reduction behavior, and acidity of the catalyst. It was proved that the addition of alumina and yttria obviously increased the sulfur content on the fresh catalyst and also markedly stabilized the sulfur species on the used catalysts. Thus, the modified catalyst possessed the better stable activity and selectivity although the addition of promoter could not enhance the isomerization activity. The crystalline structure of sulfated zirconia, acidity, and sulfur content only showed a limited influence on the isomerization activity of the catalyst. This work would have potential use to prepare an ideal catalyst for a commercial alkane hydroisomerization unit. [ABSTRACT FROM AUTHOR]

Highlights: [•] Crude rice bran oil with 40wt% FFA is converted to biodiesel via one-step reaction. [•] Chlorosulfonic acid modified zirconia catalyze the reaction at only 120°C. [•] The catalyst shows high FFA and water tolerance. [ABSTRACT FROM AUTHOR]

Mesoporous hollow colloidal particles with well-defined characteristics have potential use in many applications. In liquid-phase catalysis, in particular, they can provide a large active surface area, reduced diffusion resistance, improved accessibility to reactants, and excellent dispersity in reaction media. Herein, we report the tailored synthesis of sulfated ZrO2 hollow nanostructures and their catalytic applications in the dehydration of fructose. ZrO2 hollow nanoshells with controllable thickness were first synthesized through a robust sol-gel process. Acidic functional groups were further introduced to the surface of hollow ZrO2 shells by sulfuric acid treatment followed by calcination. The resulting sulfated ZrO2 hollow particles showed advantageous properties for liquid-phase catalysis, such as well-maintained structural integrity, good dispersity, favorable mesoporosity, and a strongly acidic surface. By controlling the synthesis and calcination conditions and optimizing the properties of sulfated ZrO2 hollow shells, we have been able to design superacid catalysts with superior performance in the dehydration of fructose to 5-hydroxymethyfurfural than the solid sulfated ZrO2 nanocatalyst. [ABSTRACT FROM AUTHOR]

Currently, the major concern in production of biodiesel fuel is to exploit new cata-lysts with the optimal conditions. In this study, the effect of calcination temperature on the synthesis of 20 mol % SrO/S-ZrO, was examined by solvent-free method. Moreover, the ability of the catalyst for esterification reaction of oleic acid with methanol was also assessed. To obtain this objective, X-ray diffraction and infra-red spectroscopy method was employed to characterize the structure of the catalysts. The results of this study re-veal that the calcined strontium oxide promoted sulfated zirconia at 500 °C has the high-est percentage of tetragonal phases of zirconia. It has also been demonstrated that owing to the high percentage of the tetragonal phases of zirconia and the acidity of the catalyst, conversion of oleic acid to fatty acids methyl esters (i.e., FAME) could be enhanced from 88.36 % to 91.13 %. Moreover, it has also been shown that 20 mol % SrO/S-ZrO2 exhib-its higher activity in comparison with S-ZrO2, at 500 °C in esterification reaction due to the presence more sulfate ions and higher activity of strontium ions. [ABSTRACT FROM AUTHOR]

The procedures leading to the preservation of catalytic performances of Au/ZrO2 samples have been investigated. The three potential causes of deactivation, namely the particle growth by sintering of gold nanoparticles, the metal leaching and the formation of un-reactive species which inhibit the reaction, have been evaluated. In particular, this paper deals with the stability of gold nanoparticles: (1) under storage conditions; (2) with time on stream for a gas phase reaction (LT-WGSR); (3) with time on stream for a liquid phase reaction (furfural oxidative esterification). [ABSTRACT FROM AUTHOR]

Synthesis of Pt-promoted sulfated zirconia catalyst Pt/SO4 2−/ZrO2 (designated as PSZ), Pt/SO4 2−/ZrO2-Al2O3 (designated as PSZA), and Pt/SO4 2−/ZrO2-Al2O3-Y2O3 (designated as PSZAY) was reported. These catalysts were characterized by N2 adsorption–desorption, thermal gravimetric (TG) analysis, NH3-temperature programmed desorption (NH3-TPD), and H2-temperature programmed reduction (H2-TPR) techniques. Effects of calcination temperature of the catalysts on the n-hexane hydroisomerization behavior were investigated in details. The experiment results revealed that the addition of Al and Y or Al promoter alone could improve the thermal stability of the catalysts. PSZA and PSZAY exhibited higher isomerization activity than unmodified PSZ as the calcination temperature of sulfated Zr(OH)4 was relatively high, for example, between 650°C and 750°C. For the first time, it was found that water-washing treatment of PSZA and PSZAY at different preparation stages had considerably different impacts on their catalytic activity. Water-washing after calcination of the sulfated Zr(OH)4, the catalytic activity of PSZA and PSZAY was high, as indicated by approximately 80% of n-hexane conversion. However, water-washing before calcination of sulfated Zr(OH)4 led to a significant decrease in the catalytic activity of PSZA and PSZAY, that is, the n-hexane conversion diminished to around 35%. It was proposed that the presence of excessive sulfur species over sample was favorable for keeping the active sulfur species in the catalyst surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of mesoporous nanocrystalline tetragonal zirconia. [•] Effect of digestion time, sulfonation on structural, textural and catalytic properties. [•] Strong influence of sulfonating agent and digestion time on number and type of acid sites. [•] Chlorosulfonic acid (CA) found to be better sulfonating agent than sulfuric acid. [•] CA prepared catalyst with 3h digestion time gave 85% conversion in 80min at 60°C. [ABSTRACT FROM AUTHOR]

The aldol condensation reaction over sulfated zirconia led to the production of diacetone alcohol, which was further dehydrated forming mesityl oxide. The sulfated zirconia was obtained from zirconium acetate ethane sulfonate as a single source precursor. Oxides were obtained by calcinations of the precursors at 550-650 °C, while the self-condensation reaction of acetone was carried out at 150 °C. The precursor and the produced oxides were characterized using various characterization techniques. The precursors were synthesized with different acetate to ethane sulfonate ratio, ranging from 1 to 3. The major products obtained from the condensation reaction over the resulted oxide were mesityl oxide, mesitylene isophorone, naphthalene, and pentamers. The selectivity of mesityl oxide was approximately 100 % at the initial time-on-stream. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The conversion of benzene-containing gasoline fractions on the bifunctional Pt/SO-ZrO-AlO catalytic system with different compositions of the support is studied. Using the results from hydroisomerization of a heptane-benzene model mixture, it is shown that a system with 67.8 wt % of aluminum oxide in its support has the best catalytic properties. For the IBP-85°C industrial benzene-containing fraction (23.7 wt % of benzene), it is established that the given catalyst ensures the complete removal of arenes from the benzene-containing fraction while raising its research octane number by 2.2-3.3 points and retaining a high yield of liquid products at levels of 98.7 wt % and higher. [ABSTRACT FROM AUTHOR]

Sulfated zirconia catalysts are proposed for the reversible hydrolysis of ethyl lactate instead of liquid acids. Sulfated zirconia catalysts were prepared by precipitation-impregnation method. The zirconium hydroxide was produced from zirconium oxychloride by adding aqueous ammonia and then impregnated in sulfuric acid. The solid samples were obtained by filtration and evaporation of the mixtures, respectively. After the samples were calcined, the sulfated zirconia catalysts were prepared. The results showed that the catalyst prepared by evaporation has higher catalytic activity. The physicochemical characteristics of the sulfated zirconia catalysts were studied by thermal analysis, X-ray powder diffraction (XRD), temperature programmed desorption of ammonia (NH-TPD) and N adsorption-desorption, respectively. By the precipitation-impregnation-evaporation method, the optimal sulfated zirconia catalyst of tetragonal phase was prepared under liquid-solid ratio of 5ml/g, 1 mol/L of HSO and calcination at 650 °C for 3 h. The conversion of the ethyl lactate was 87.8% in 3 h at 85 °C with the catalyst loading 2 wt% and initial molar ratio of water to ethyl lactate 20: 1. [ABSTRACT FROM AUTHOR]

Abstract: Combustion synthesis leads to very interesting characteristics to inorganic oxides which could be further modified to render them catalytic properties. Several new approaches were studied to make a novel superacidic sulfated zirconia called fuel lean sulfated zirconia (FLSZ), by combustion synthesis. FLSZ was fully characterized and used in a reaction of industrial relevance. The isomerization of styrene oxide to 2-phenyl acetaldehyde was studied by using several solid acid catalysts. 2-Phenyl acetaldehyde finds applications in the synthesis of fine chemicals, intermediates, speciality chemicals, flavors and fragrances. Among various catalysts studied FLSZ was found to give the best activity and selectivity to 2-phenyl acetaldehyde at 100°C using cyclohexane as a solvent. Process parameters were optimized by conducting a systematic investigation. The kinetics of the reaction was also studied. The catalyst is robust, recyclable and found to be highly active and selective. The overall process is 100% atom economical, green and clean. [Copyright &y& Elsevier]

The condensation reaction of o-phenylenediamine and arylaldehydes was investigated in the presence of nanosized sulfated zirconia (SO-ZrO) as the solid acid catalyst. Nanosized SO-ZrO was prepared and characterized by the XRD, FT-IR, and SEM techniques. The results confirm good stabilization of the tetragonal phase of zirconia in the presence of sulfate. Reusability experiments showed partial deactivation of the catalyst after each run; good reusability can be achieved after calcinations of the recovered catalyst before its reuse. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis of biomass-derived lubricants via esterification, transesterification, and simultaneous reactions of both was studied by using sulfated zirconia catalysts. Soybean oil or free fatty acids derived from soybean oil were used as a biomass-derived resource for the synthesis of biolubricants. Long chain alcohols (carbon number≥8) or neo-polyols (e.g., 2,2-diethyl-1,3-propanediol, trimethylol propane, pentaerythritol) were used as co-reactants. The structure of the alcohol significantly affected the conversion and yield for the esterification with oleic acid. The esters produced showed kinematic viscosity and viscosity index comparable to commercial lubricants. Various sulfated zirconia catalysts were prepared and were characterized by X-ray diffraction, NH3 temperature-programmed desorption, Brunauer–Emmett–Teller isotherm, and tested for esterification. The type of zirconium precursor demonstrated a significant effect on the physical property of the catalyst and its catalytic activity. Interestingly, esters with fully saturated hydrocarbon chains were synthesized from unsaturated free fatty acids regardless of the absence of hydrogen gas. The sulfated zirconia could be recycled for up to five repeated reactions without any degradation. The effects of reaction time and temperature were also investigated. [Copyright &y& Elsevier]

Abstract: In this paper, ceria supported on sulfated zirconia (CeSZ) as a superacid catalyst was synthesized and the resulted performances for selective catalytic reduction (SCR) of NO with NH3 were investigated. Experimental results revealed that the sulfation of zirconia supports could greatly improve the SCR activity of the catalysts. Among the tested samples, the CeSZ catalyst with Ce/Zr mole ratio at 0.095 possessed the highest NO conversion (i.e., 98.6% at ca. 420°C and 180,000h−1). The sulfation had led to a formation of pure tetragonal phase of ZrO2, a well dispersion of CeO2, abundant stable superacid sites, increasing surface area and enrichment of Ce3+ on the surface, all of which were responsible for its excellent performance in SCR of NO with NH3. [Copyright &y& Elsevier]

Abstract: Sulfated zirconia was synthesized and characterized by various physico-chemical techniques such as EDS, Thermal analysis (TGA & DTG), FT-IR, XRD, BET surface area measurement, SEM and n-butyl amine acidity determination. The use of synthesized catalyst was explored for biodiesel production by esterification of (free fatty acid) oleic acid with methanol. Influence of various reaction parameters (catalyst concentration, acid/alcohol molar ratio, catalyst amount, reaction temperature and reaction time) on catalytic performance was studied to optimize the conditions for maximum yield of methyl oleate. Also the catalyst was regenerated and reused. As an application, preliminary study was carried out for biodiesel production by transesterification of waste cooking oil and Jatropha oil, as feedstock without any pretreatment, with methanol. [Copyright &y& Elsevier]

Catalytic dehydration of 1-Butanol was used as a test reaction to determine the nature of acid sites on several samples: undoped and doped sulfated-zirconia (dopants: Ce, W, or Sb), ZSM-5, Al-MCM-41 and permutite (amorphous aluminosilicate). Acid strength for each sample was ranked according to its catalytic activity. Catalysts exhibiting similar activity can be compared by the isomer ratios: cis-butene/trans-butene (CB/TB), 1-butene/trans-butene (1B/TB), and isobutene/ trans-butene (IB/TB). It was found that the activity of the sulfated-zirconia was directly proportional to the sulfate content. Interestingly, Al-MCM-41 exhibits similar acidity to the best sulfated-zirconia sample.

Abstract: We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to ∼2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to ∼80m2/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions. [Copyright &y& Elsevier]

Pt/SO42−/ZrO2-Al2O3(PSZA) catalysts were prepared by extruding sulfated hydroxide zirconium with SB powder. The n-hexane hydroisomerization reaction was performed in a continuous flow fixed-bed reactor. Isomerization activities under varying pretreatment parameters (including catalyst storage time before use, activating temperature, and reduction temperature) and reaction conditions (including reaction temperature, space velocity, and the molar ratio of hydrogen to n-hexane) were investigated. The results indicated the optimum pretreatment conditions for the PSZA catalyst is as follows: five days of storage, 350°C of the activation temperature, and 250°C of the reduction temperature. In addition, the optimum reaction conditions contained the reaction temperature ranging from 200 to 210°C, space velocity of 1 hr−1, and hydrogen to hexane mole ratio of 5. [ABSTRACT FROM AUTHOR]

Abstract: Prins cyclization of styrene with paraformaldehyde was carried out over sulfated zirconia (SZ) catalyst in liquid phase. The SZ catalysts were synthesized by precipitation method with different sulfur impregnation and characterized by XRD, FT-IR, Nitrogen sorption, NH3-TPD. The SZ showed best performance among different types of acid catalysts. The acidity of SZ optimized by different concentrations of H2SO4 treatment influences the selectivity for dioxane. The sulfur loading, nature of solvent, temperature, catalyst amount, mole ratio and reusability of catalyst were investigated. The SZ catalyst synthesized by impregnating 2N sulfuric acid was found to be highly selective for the synthesis of 4-phenyl-1,3-dioxane (93%) with almost complete conversion of styrene (∼100%). The catalyst was recycled thrice with negligible decrease in the yield of 4-phenyl-1,3-dioxane. [Copyright &y& Elsevier]

The synthesis of a series of new azo dyes containing 4-sulfonyl azide benzenediazonium salt, salicylic acid, 2-hydroxy benzoic acid, and 2,4-dihydroxy benzoic acid derivatives over eco-friendly baker's yeast, modified montmorilonite K10, zeolites and sulphated zirconia are described. These inexpensive, noncorrosive and reusable catalysts were found to exhibit bifunctional catalytic properties for these reactions. No considerable decrease in the efficiency of the catalysts was observed after four cycles of operation. The new method totally avoids the use of acid, alkali or toxic solvents in diazotization and azocoupling reactions. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the process optimization and kinetic study for the heterogeneous transesterification of non-edible sea mango (Cerbera odollam) oil using response surface methodology central composite design (RSMCCD). The four transesterification process variables studied are; reaction temperature (333–453K), reaction time (1–5h), molar ratio of oil to methanol (1:6–1:14) and amount of sulfated zirconia catalyst (2–10g* g−1) (catalyst/oil). From this study, it was found that reaction temperature gave the most significant effect on the conversion of sea mango oil to fatty acid methyl esters (FAME), followed by reaction time. There were also significant interaction effects between reaction temperature and amount of catalyst, and between reaction time and amount of catalyst. Based on the optimized condition, highest conversion of 97.5% was predicted using the following variables; reaction temperature=423K, reaction time=3h, molar ratio of oil to methanol=1:12 and amount of catalyst=8g* g−1. Experimental verification on the predicted optimum condition gave an actual conversion of 94.1%. The small error between the predicted and actual optimum conversion (3.5%) indicated that the model was valid and accurate in representing the actual experimental values and also in predicting conversion at any condition within the range studied. The developed kinetics model suggested a 1.1th order reaction with activation energy of 36.03kJmol−1 and frequency factor of 5.56×102 min−1. [Copyright &y& Elsevier]

Abstract: A dual-catalyst bed composed of a reduction (Pd/SZ) and an oxidation (CoO x /CeO2) catalyst was investigated for selective catalytic reduction (SCR) of NO2 using hydrocarbons for lean-burn natural gas engines. The choice of a multifunctional oxidation catalyst was seen to play a crucial role to achieve the desirable NO2 reduction performance. A dual-catalyst bed optimization showed that different cobalt containing oxidation catalysts could be exploited to achieve desirable NO x and hydrocarbon conversions. Moreover, cyclic experiments in the presence of water vapor were conducted to understand its implications on dual catalyst bed performance. Finally, both kinetic and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies were undertaken to examine the behavior of the oxidation catalyst with respect to hydrocarbon oxidation which consequently affect the overall NO x reduction activity. [Copyright &y& Elsevier]

Abstract: Monometallic (Pt or Pd) and bimetallic (Pt–Pd) catalysts supported on zirconia promoted with sulfate (SZ) or tungsten oxide (WZ) were prepared and tested in the gas-phase hydrodechlorination of dichloromethane. The catalysts showed a high selectivity to non-chlorinated products (between 80% and 90% at 250°C) being methane the main reaction product. As a general trend, the WZ catalysts yielded significantly higher dichloromethane conversion than the SZ ones, yielding all the catalysts initial conversions higher than 80% at a reaction temperature of 250°C. However, the former showed a very poor stability regardless of the metallic active phase. On the other hand, the presence of palladium in the sulfated zirconia catalyst avoids deactivation as proved in long-term experiments (80-h time on stream). XPS and elemental analyses of the used catalysts suggest that adsorption of organochlorinated species is a cause of deactivation by blocking the active sites. In the monometallic SZ Pt catalyst, deactivation occurs also by poisoning of the Pt sites by the H2S resulting from sulfate reduction under the hydrogen-rich gas atmosphere. The metal particle size appears to be a critical point with regard to stability of the catalysts. The one with the highest dispersion showed the highest stability with no signs of deactivation after more than 80h on stream. [Copyright &y& Elsevier]

Mesoporous sulfated zirconia nanoparticles (MSZNP) with high surface area have been synthesized by using sodium dodecyl sulfate (CHOSONa, SDS), both as a template and a sulfating agent via one-step route. On the basis of FT-IR, EDS together with NH-TPD analyses, the SO anion, originated from the hydrophilic head of SDS, can be incorporated into ZrO to form MSZNP with super-acidity. The phase transition of ZrO from tetragonal to monoclinic phase was effectively inhibited by the presence of SO, and the formation mechanism was illustrated in detail. MSZNP achieved far higher activity than CSZ in transesterification of soybean oil with methanol due to the synergistic effect of strong acidity, high BET surface area and the formation of mesostructure. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous solid acid catalyst, sulfated zirconia loaded mesoporous silica, was reported here by a facile vapor–induced hydrolysis method. The zirconia precursor of Zr(SO4)2 was introduced into the mesopore of SBA-15 by impregnation, and then hydrolyzed under a NH3/H2O vapor ambience to form a thin zirconia layer coated on the pore surface of SBA-15, which was followed by the sulfation of SO4 2− ions with calcinations. The catalyst was characterized by powder X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy and infrared spectroscopy, and the results indicated that the catalyst retained the ordered mesoporous structure, high BET surface area, connected pore channel without pore blocking and a 0.7nm thin layer of sulfated zirconia coated on the pore surface. This super acid catalyst showed much higher activity compared with those of unloaded sulfated zirconia and sulfated zirconia loaded SBA-15 hydrolyzed by ammonia aqueous solution, for catalyzing the esterification reaction of oleic acid and methanol. The experimental parameters including the molar ratio of reactants and reaction time were optimized, and approximately 70% of acid sites were remained after three cycles. [Copyright &y& Elsevier]

Friedel-Crafts green alkylation of xylenes with tert-butanol was investigated in the presence of mesoporous superacidic catalysts named as UDCaT-4, UDCaT-5 and UDCaT-6. The catalysts are modified versions of zirconia showing high catalytic activity, stability and reusability. The catalytic activity is in the order: UDCaT-5 (most active) > UDCaT-6 > UDCaT-4 > sulfated zirconia (least active). Synergistic effect of very high sulfur content present (9% (w/w) S) and preservation of tetragonal phase in UDCaT-5, in comparison with sulfated zirconia (4% (w/w) S), were responsible for higher catalytic activity. The performance of UDCaT-5 in alkylation of xylenes was studied with tert-butanol with reference to selectivity and stability. Alkylation of m-xylene over UDCaT-5 gives 96% conversion of tert-butanol with 82% selectivity towards 5-tert-butyl-m-xylene (5-TBMX) under optimum reaction conditions. The formation of products is correlated with the acidity of the catalyst. The reactions were conducted in liquid phase at relatively low reaction temperatures (130-160 C). A systematic investigation of the effects of various operating parameters was done to describe the reaction pathway. The reaction was carried out without any solvent in order to make the process cleaner and greener. An overall second order kinetic equation was used to fit the experimental data, under the assumption that both xylene and tert-butanol are weakly adsorbed. An independent study of dehydration of tert-butanol (TBA) was also done. Alkylation of o-xylene and p-xylene with tert-butanol was also studied. The overall process is green and clean. [ABSTRACT FROM AUTHOR]

Abstract: We report the production of a biodiesel fuel by acid-catalyzed esterification of high free fatty acid (FFA) karanja oil (KO). Pretreated KO was converted to biodiesel by a process of alkaline catalyzed transesterification. Optimum acid-catalyzed esterification was achieved using 1% Sulfated Zirconia (SZ) as a solid acid catalyst with a methanol-to-oil ratio of 9:1, temperature at 60°C and reaction time of 2h. During this process, FFA were converted into fatty acid methyl esters. The acid value of karanja oil was reduced to 1.3mg KOH/g from 12.27mg KOH/g, which confirmed the conversion. Consequently, this pretreatment reduces the overall complexity of the process and reduces the cost of producing biodiesel fuel. [Copyright &y& Elsevier]

Abstract: A novel zirconia-based catalyst, with high sulfur content (15% w/w) and preservation of the tetragonal phase of zirconia, was synthesized for the first time via a solution combustion synthesis approach. Such high sulfur content with preservation of the tetragonal phase has not been reported so far. The catalyst synthesis parameters were optimized using a probe reaction of Friedel–Crafts alkylation. The optimized catalysts, fuel-lean sulfated zirconia (FLSZ) and fuel-rich sulfated zirconia (FRSZ), were characterized by XRD, FTIR, TPD, EDAX, SEM, and BET surface area and pore size analysis. Further, the activity and stability of FLSZ was tested using a Pechmann condensation reaction between resorcinol and ethyl acetoacetate to produce 7-hydroxy 4-methyl coumarin selectively. A complete theoretical and experimental analysis is presented, and a kinetic model is developed for this reaction. The model explains the experimental data well. The characterization and reaction studies show that combustion-synthesized sulfated zirconia exhibits higher superacidity than the conventional sulfated zirconia catalyst. [Copyright &y& Elsevier]

Catalytic properties of Sulfated Zirconia (SZ) and Niobium Oxide (NBO), in sucrose inversion reaction to obtain invert sugar were studied. The reaction was performed in two types of solvents: water or water:ethanol (50:50). Materials were analyzed by X-ray Diffraction (XRD), Nitrogen Physisorption, Temperature Programmed Desorption (TPD) and Infrared Spectroscopy (IR). The results showed an important influence of the solvent on the catalytic activity for both catalysts. It was found that SZ had a higher conversion (%) corresponding to 98% in water:ethanol opposite trend than NBO, which exhibited better catalytic activity in water solvent with a conversion (%) of 66%, such behavior can be assigned to the possible conservation of structural stability of each of the catalysts in the solvents used. It was also showed a higher selectivity at 100 % to the interest product when NBO was used, it is attributed to acid-tolerant properties in polar liquids, while SZ caused a consequent degradation of sucrose giving rise to the formation of secondary products of reaction and selectivity (%) around of 80%, due to the significant acidity as showed in the TPD results. [ABSTRACT FROM AUTHOR]

Solvent-free technique was employed in this work in order to assess the influence of the calcination temperature on the activity of Al-promoted sulfated zirconia. The cata-lyst was analyzed by XRD and IR-spectrum method, and catalytic activity was examined by esterification reaction of oleic acid. XRD analysis revealed that a decline in the per-centage of tetragonal phases of zirconia was observed by increasing the calcination tem-perature from 500 to 900 °C. In addition, a reduction of sulfate groups as SO42- on zirco-nia surface was observed. As a consequence, a decline in Bransted sites with calcination temperature enhancement also prevailed. Therefore, the size of Al-promoted sulfated zir-conia particles was increased accordingly. On the other hand, with the aluminum sulfate loading, the amount of sulfate ions on Al-promoted sulfated zirconia surface was en-hanced and a reduction in particle size of Al2O3/S-ZrO2 was also observed, as compared to non-promoted. The result of this study revealed that an increase of sulfate and alumina groups causes a raise in the acidity of catalyst. Furthermore, the calcined Al-promoted and non-promoted sulfated zirconia would convert 96.10 % and 89.36 % of oleic acid to biodiesel, respectively. Therefore, Al2O3/S-ZrO2 as a catalyst exhibits a higher activity than S-ZrO2. [ABSTRACT FROM AUTHOR]

Abstract: Stable sulfated zirconia can be prepared by impregnation with sulfuric acid of a zirconium doped mesoporous MCM-41 silica and ulterior calcination at 750°C. Two catalysts with nominal sulfur contents of 1.3 and 4wt.% were prepared. After the thermal activation at this temperature, some sulfate ions (sulfur content of 0.15 and 0.69wt.%) are strongly retained onto the superficial zirconia, thus generating acidic catalysts which are able to produce the esterification of oleic acid with methanol at 75°C in 5h. The experimental results reveal that the unique way to obtain stable catalysts without leaching of sulfate species to the liquid medium of reaction is by thermal treatment at high temperature as 750°C. Only with 1g of this stable catalyst a conversion close to 98% was attained. The conversion of this catalyst is well maintained in a high extend (76%) after three cycles of catalysis without any treatment and is stable in the presence of 5wt.% of water. [Copyright &y& Elsevier]

Abstract: This study was conducted to investigate the active role of sulfated zirconia catalyst in the transesterification of palm (Elaeis guineensis) and sea mango (Cerbera odollam) oils. Initially, the sulfated zirconia catalysts were prepared and optimized under various preparation conditions – calcination temperature, calcination period and ratio of Zr-species/support - and then characterized for its physical and chemical properties. The performance of the sulfated zirconia catalysts was tested in the transesterification of palm oil and sea mango oil. The optimized sulfated zirconia catalyst was also tested for its reusability and regenerability. From this study, it was found that the best (optimum) sulfated zirconia catalyst was prepared using calcination temperature of 400 °C, calcination period of 2.5 h and ratio of Zr-species/support of 2 g g−1. It was also found that the prepared sulfated zirconia catalyst contains acid sites which become the key factor in the transesterification process. The optimized sulfated zirconia catalyst was shown to be able to produce high yield of fatty acid methyl esters (>80%) even with oil that has high free fatty acids content i.e. sea mango oil. The reusability and regenerability study showed that the optimized sulfated zirconia can be regenerated and reused repeatedly with an average of 5% loss in activity after each run. [Copyright &y& Elsevier]

The catalytic activity of nano-crystalline sulfated zirconia catalyst, prepared by sol-gel method and characterized by various analytical tools, was evaluated for the esterification of caprylic acid with different short chain alcohols. The lower concentration of catalyst (0.5 wt%) exhibited 96-98% conversion of caprylic acid with methanol and 100% selectivity for methyl caprylate at 60 °C. The conversion was decreased with increasing carbon chain of alcohols namely with ethanol, n-propanol and n-butanol at 60 °C but increased significantly (91-98%) at higher reaction temperature. The selectivity for respective alkyl caprylate was observed to be 100% irrespective of the alcohol used. The activity of the catalyst was slightly decreased with successive five reaction cycles due to the water formed during the reaction. [ABSTRACT FROM AUTHOR]

Abstract: Sulfonic acid functionalised SBA-15 (SO3H-SBA-15), sulfated zirconia and beta, Y, ZSM-5 and mordenite zeolite catalysts have been applied for the dehydration of sugars to ethyl levulinate and ethyl-d-glucopyranoside (EDGP) using ethanol as solvent and reactant. The SO3H-SBA-15 catalyst showed a high catalytic activity for the selective conversion of fructose to ethyl levulinate (57%) and glucose to EDGP (80%) at 140°C, whereas the disaccharide sucrose yielded a significant amount of both products. The SO3H-SBA-15 catalysts were found to be highly active compared to the zeolites under identical reaction conditions. [Copyright &y& Elsevier]

Abstract: Nanocrystalline sulfated zirconia powder was prepared by a non-alkoxide sol–gel route using acidic condition (pH 1–2). The samples had superfine crystallites and pure tetragonal phase at 700°C. Zr(acac)4 was used as zirconium precursor due to a better retention of sulfate species and H2SO4 0.5M was used as sulfating agent. Fourier transform infrared (FT-IR) spectra have shown Zr–O–Zr and sulfate bonds. Crystal phase and crystallite size have been determined by X-ray Diffraction (XRD) analysis. Besides, the morphology of the samples has been investigated by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The optical properties of the samples have been analyzed using photoluminescence (PL) spectroscopy, too. All the analyses consistently have shown fairly uniform nanoparticles (calcined at 600 and 700°C) with very small size and pure tetragonal phase with crystallite size between 5 and 10nm. [Copyright &y& Elsevier]

Nano-crystalline sulfated zirconia catalyst, prepared by two-step sol-gel method, has been studied for the solvent free self condensation of acetophenone to dypnone. The influence of calcination temperature on the structural, textural and catalytic activity of sulfated zirconia has been analyzed. The surface acidity along with the structural and textural features of the catalyst influenced its activity. The conversion of acetophenone was found to be effected by the variation in the reaction and calcination temperature, however, the dypnone selectivity was not affected much. The catalyst calcined at 650 °C, showed maximum dypnone selectivity of 92% with 68.2% acetophenone conversion at 170 °C after 7 h. The catalyst was reused up to five cycles with marginal decrease in acetophenone conversion, however, without losing its selectivity for dypnone. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the work was the analysis of the phenomena occurring during glycerol dehydration in the presence of sulfated zirconia used as solid acid catalysts; the attention was focused on catalyst deactivation. A close correlation between the sulfate content and catalytic behavior was found. In addition to the accumulation of carbon residues on the catalyst surface, there were other phenomena contributing to catalyst deactivation: (i) the self-reduction of sulfuric into sulfurous groups – an event which occurred, however, only in samples with the higher S content under anaerobic conditions – and (ii) the leaching of S from catalysts, due to the hydrolysis of sulfate groups and the formation of volatile esters. These findings are of general interest in relation to both the transformation of glycerol into acrolein by means of gas-phase dehydration and the use of sulfated zirconia catalysts for high-temperature, acid-catalyzed reactions. [Copyright &y& Elsevier]

Abstract: A series of non-periodic mesoporous silicas impregnated with both framework and nanocrystalline sulfated zirconia was prepared by a sol–gel process using an ionic liquid as a template. The physico-chemical properties of the mesoporous sulfated zirconia materials are described. Analysis of the new silicas indicates isomorphous substitution of silicon with zirconium and reveals the presence of extremely small (<10nm) polydispersed zirconia nanoparticles in the materials with zirconium loadings of 28–41wt.%. The materials with higher zirconium loadings catalyse the Meerwin–Ponndorf–Verley reductions of aldehydes and ketones for substrates with hydrogen-bond basicities, pK HB >1.10. In order to explain the catalytic activity, analysis of the acid sites of the materials using pyridine as a probe molecule reveals that in all cases the majority are Bronsted acid sites, with only a small number of Lewis acid sites present in those materials with low zirconium loadings. [Copyright &y& Elsevier]

In-Fe loaded sulfated zirconia (SZ) was firstly studied for the selective catalytic reduction (SCR) of NO with methane and exhibited higher activity than In/SZ and Fe/SZ. The addition of iron to the In/SZ increases its surface area and strong acid sites, which can be helpful for the SCR of NO. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]