Suppression of radical-cationic benzene oligomerization on sulfated zirconia

The effect of catalyst activation conditions on transformations of benzene cation radicals on sulfated zirconia has been studied by in situ ESR spectroscopy. After the catalyst activation at 300°C there was no oligomerization of the cation radicals to biphenyl and heavier products, which is observed after catalyst calcination at 500°C. It has been suggested that the oligomerization is suppressed by the presence of strong Br?nsted sites on the surface.     

纯四方相硫化氧化锆催化剂的制备及其生物柴油合成应用研究

将过硫酸铵浸渍于直接合成的纳米氧化锆晶体表面,经300-500℃高温焙烧处理获得硫化氧化锆催化剂。采用X射线衍射（XRD）、氮气吸附-脱附、氨气程序升温脱附（NH₃-TPD）、傅里叶红外光谱（FT-IR）、扫描电镜（SEM）和能谱仪（EDS）等分析手段对催化剂的结构性能进行了表征。结果表明,所有的催化剂均展现出纯四方相结构和高的结晶度。其中,经500℃热处理获得的催化剂拥有最高的硫含量和酸性位,将其应用于大豆油与甲醇酯交换反应合成生物柴油,获得了脂肪酸甲酯收率高达84.6%的催化效果,进一步表明该催化剂表面存在优越的超强酸位。     

Formation of supported size-controlled nanoparticles of sulfated zirconia

Methods of the preparation of catalysts for alkane skeletal isomerization based on uniform nanoparticles of sulfated zirconia anchored to different supports were investigated. These catalysts were characterized by using the ICP, HRTEM and BET techniques. The activities of the catalysts in the reaction of n-butane isomerization were measured and compared with those of bulk catalysts.     

Comparison of the promoting effects of gallium and aluminium on the n-butane isomerization actvity of sulfated zirconia

Sulfated zirconia catalysts promoted by gallium or aluminium were prepared and tested for n-butane isomerization. Both elements increase and stabilize the isomerization rate. Characterization results showed that the promoting mechanism of gallium was different from that of aluminium. This revised version was published online in June 2006 with corrections to the Cover Date.     

Benefits of mesopores in sulfated zirconia catalyst

Activities of two catalysts obtained from hydroxide and alkoxide precursors were correlated to their different structural and textural properties. Activity is mainly determined by the presence of active tetragonal phase, which is more stable at high temperatures in the catalyst of alkoxide origin than in one from hydroxide. An appropriate structure must be accompanied with beneficial pore structure, as is the case of mesopores of the catalyst from alkoxide. In the case of very small pores of the catalyst from hydroxide precursor, activity is negligible due to pores plugged by coke.     

Enhancement of catalytic activity of titanosilicalite-1 - sulfated zirconia combination towards epoxidation of 1-octene with aqueous hydrogen peroxide

Summary Titanosilicalite-1 (TS-1) in combination with sulfated zirconia efficiently catalyzes the epoxidation of 1-octene with aqueous hydrogen peroxide. The presence of both octahedral zirconium and sulfate species in the catalysts enhances the epoxidation rates.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

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.     

Oxidative dehydrogenation of ethane with carbon dioxide over sulfated zirconia supported metal oxides catalysts

Several metal oxides supported on sulfated zirconia catalysts were tested for the oxidative dehydrogenation of ethane into ethylene by carbon dioxide. It is found that the catalytic behavior of supported oxide catalysts differ depending on the nature of metal oxides. Chromium oxide-sulfated zirconia exhibits the highest ethane conversion and medium level of ethylene selectivity, producing 38% ethylene yield at 50% ethane conversion at 650°C.     

Effect of metals on the catalytic activity of sulfated zirconia for light naphtha isomerization

We studied on the function of the metal in the sulfated zirconia(SO₄^2–/ZrO₂) catalyst for the isomerization reaction of light paraffins. The addition of Pt to the SO₄^2–/ZrO₂ carrier could keep the high catalytic activity. The improvement in this isomerization activity is because Pt promotes removal of the coke precursor deposited on the catalyst surface. Though this catalytic function was observed in other transition metals, such as Pd, Ru, Ni, Rh and W, Pt exhibited the highest effect among them. It was further found that the Pd/SO₄^2–/ZrO₂–Al₂O₃ catalyst possessed a catalytic function for desulfurization of sulfur-containing light naphtha in addition to the skeletal isomerization. The sulfur tolerance of catalyst depended on the method of adding Pd, and the catalyst prepared by impregnation of the SO₄^2–/ZrO₂–Al₂O₃ with an aqueous solution of Pd exhibited the highest sulfur tolerance.Further, we investigated the improvement in sulfur tolerance of the Pt/SO₄^2–/ZrO₂–Al₂O₃ catalyst by impregnation of Pd. The results of EPMA analysis indicated that this catalyst was a hybrid-type one (Pt/SO₄^2–/ZrO₂–Pd/Al₂O₃) in which Pt/SO₄^2–/ZrO₂ particles and Pd/Al₂O₃ particles adjoined closely. This hybrid catalyst possessed a very high sulfur tolerance to the raw light naphtha that was obtained from the atmospheric distillation apparatus, although this light naphtha contained much sulfur. We assume that such a high sulfur tolerance in the hybrid catalyst is brought about by the isomerization function of Pt/SO₄^2–/ZrO₂ particles and the hydrodesulfurization function of Pd/Al₂O₃ particles. Besides, since the hybrid catalyst also provides high catalytic activity in the isomerization of HDS light naphtha, we suggest that the Pd/Al₂O₃ particles supply atomic hydrogen to the Pt/SO₄^2–/ZrO₂ particles by homolytic dissociation of gaseous hydrogen and also enhance the sulfur tolerance of Pt/SO₄^2–/ZrO₂ particles. Finally, we also propose the most suitable location of Pd and Pt in the metal-supported SO₄^2–/ZrO₂–Al₂O₃ catalyst.     

Thermal behavior of n-alcohols, benzene, and toluene in water urea and water ethyleneglycol systems

Relations are suggested for calculating the heat characteristics of alcohols, benzene, and toluene in aqueous solutions of urea and ethylene glycol. The solution heat of an alcohol shows greater dependence on the glycol concentration, while the heat capacity of solution, on the urea concentration. For n-butanol in aqueous glycol, the characteristic temperature at which the solution heat of the alcohol is zero decreases as the glycol concentration increases. The dependence of the characteristic temperature of 1-butanol on the urea concentration has a maximum.     

An efficient synthesis of 1,5-benzodiazepine derivatives catalyzed by a solid superacid sulfated zirconia

2,3-Dihydro-1H-1,5-benzodiazepines are synthesized by the condensation of o-phenylendiamine and various ketones in the presence of a versatile solid superacid catalyst ‘sulfated zirconia’ under solvent free conditions.     

采用二维气相色谱及毛细管色谱柱分析汽油中苯和甲苯的含量

采用微板流路控制技术(Deans Switch)和常见的商品毛细管柱HP-5 (30 m×0.32 mm×0.25 μm)和Rtx-TCEP (30 m×0.25 mm×0.4 μm),建立了一种全新的分析车用汽油中苯和甲苯含量的二维气相色谱方法。用该方法分析汽油中0～5%的苯和0～20%的甲苯,两者校正曲线的线性关系良好,相关系数分别为0.9994和0.9999;标准样品5次重复测定的相对标准偏差均小于1.5%;车用汽油实际样品中苯和甲苯的加标回收率在96.8%～103.8%之间。车用汽油实际样品测定结果和SH/T 0713-2002标准方法测定结果一致。该方法是车用汽油中苯和甲苯含量测定的一种简便快捷、准确可靠的分析方法。     

Density functional theory study of the reactivity and electronic structure of the transesterification of triacetin in biodiesel production via a sulfated zirconia heterogeneous catalysis

This DFT study examined the interaction of a sulfated zirconia (SZ) slab model system (heterogeneous catalyst) and triacetin (a precursor in biodiesel production) using explicit methanol solvent molecules. Full geometry optimizations of the systems were performed at the B3LYP level of theory. Gibbs free energies provide insight into the spontaneity of the reactions along a three‐step reaction mechanism for the transesterification of triacetin. Charge decomposition analysis revealed electronic charge transfer between the metallic oxide and the organic moieties involved in the reaction mechanism. Fukui indices indicate the likely locations on the SZ surface where catalysis may occur. The quadratic synchronous transit scheme was used to locate transition structures for each step of the transesterification process. The results are in agreement with the strongly acidic catalytic character of zirconium observed experimentally in the production of biodiesel. © 2016 Wiley Periodicals, Inc.     

Reversible formation of F+-centers over platinum promoted sulfated zirconia upon hydrogen treatment

Reversible formation of F⁺-centers was observed over platinum promoted sulfated zirconia in the presence and absence of hydrogen. The intensity of ESR signal of F⁺-centers was increased by treatment in He stream and it was decreased rapidly by supply of hydrogen in gas phase. This behavior seems to be related to proton spillover.     

Equilibrium and kinetic studies for the adsorption of benzene and toluene by graphene nanosheets: a comparison with carbon nanotubes

In this study, graphene nanosheets (GNSs) were adopted as an adsorbent to investigate their characterizations and performance for adsorbing benzene and toluene in aqueous solutions. In order to determine the best fit model for each considered system, nonlinear regressions were used. Experimental data of adsorption were corroborated by the combined Langmuir–Freundlich (Sips) models for the isotherms and pseudo‐first‐order model for the kinetics. As a result, GNSs displayed high affinity to the aromatic hydrocarbons such as benzene and toluene. The high affinity was dominated by π–π interactions to the flat surface and the sieving effect of the powerful groove regions formed by wrinkles on GNS's surfaces. Hydrophobic properties and molecular sizes of benzene and toluene affected the adsorption of GNS. In addition, the favorable adsorption of toluene possibly was due to the increase in the molecular weight, decrease in the solubility, and the increase in the boiling point. A comparative study on the benzene and toluene adsorption revealed that favorable adsorption of GNSs compared with that of carbon nanotubes was consistent with the order of physical properties such as specific surface area and pore's volume. Copyright © 2016 John Wiley & Sons, Ltd.     

Solubilities of benzene, toluene and diphenyl in the t-butyl alcohol+water mixtures and hydrophobic interaction

The solubilitices of benzene, toluene and diphenyl in mixed solvents of t-butyl alcohol (TBA) and water at 283.15, 288.15, 293.15 and 298.15 K have been determined by spectrophotometry. The mole fraction of TBA [x (TBA)] in the mixed solvent are 0.000, 0.010, 0.020, 0.030, 0.040, 0.045, 0.050, 0.060, 0.080 and 0.100, respectively. The standard Gibbs energies of solution of benzene, toluene and diphenyl in the mixed solvent have also been calculated based on the solubility data. The hydrophobic interactions (HI) for the pairs of benzene-benzene, methane-benzene and methane-methane in the mixed solvent were calculated and discussed.     

Acid-base, electron donating and catalytic properties of sulfated zirconia

The electron donating properties of sulfated zirconia were studied from the adsorption of electron acceptors of various electron affinity. The surface acidity and basicity of the oxides have also been determined by titration method using a set of Hammett indicators. The data have been correlated with the catalytic activity of the oxide towards esterification of acetic acid usingn-butanol, reduction of cyclohexanol in 2-propanol and oxidation of cyclohexanol with benzophenone.     

Isomerization of light alkanes: preparation and characterization of platinum promoted sulfated zirconia catalysts

Summary Platinum-promoted sulfated zirconia catalysts active in n-hexane isomerization were prepared in a one-step synthesis and characterized. The crystallinity and sulfur contents depend mainly on the calcination temperature. The stability of the sulphate in the presence of hydrogen is reduced by the presence of Pt.     

The effects of ammonium sulfate and sulfamic acid on the surface acidity of sulfated zirconia

In this work, sulfated zirconia (SZ) was prepared by a solvent-free method, ammonium sulfate ((NH₄)₂SO₄) and sulfamic acid (NH₂SO₃H) were as sulfur sources, respectively. The resulting catalysts were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), N₂ adsorption–desorption isotherms, inductively coupled plasma (ICP) and pyridine-FTIR. The characterization of the catalysts revealed that SZ prepared with (NH₄)₂SO₄ 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 (NH₄)₂SO₄ as sulfur source had a better catalytic performance for removing trace olefins from aromatics.     

The miracle role of lattice imperfections in benzene alkylation with methanol over mordenite

Mordenite (MOR) has demonstrated potential as a catalyst for alkylation due to high variability, intrinsic porosity, and outstanding stability. However, the contact probability of benzene and methanol has been limited by typical layered structures of MOR and there is no connection between layers. Here, we report the preparedness of H-MOR via a sequential post-treatment method based on a commercial MOR. H-MOR sample had appeared lattice imperfections inferred from characterization means. The samples were tested with benezene methylation reaction. Results show that the high conversion of benzene and the high selectivity of toluene were obtained from the miracle role of lattice imperfections in the H-MOR sample. Sequentially, based on the study of all catalyst structure and physical properties, a plausible reaction mechanism for the selectivity of the desired toluene was proposed.