Effect of the Sulfate Sulfur Content and the Preparation Procedure on the Catalytic Properties of Sulfated Zirconium Oxide

The effects of the composition and the procedure of preparing sulfated zirconium oxides on their catalytic properties in the reactions of 1-butene isomerization to 2-butenes and isobutanol dehydration were studied. The activity was found to depend on the nature of parent zirconium oxide, the sulfate sulfur content, and the temperature of calcination. Catalysts prepared from a crystalline oxide exhibited the highest activity. Their activity depends on the sulfate sulfur content. The calcination of catalysts at temperatures higher than 400°C resulted in a detectable loss of sulfate. The activity of sulfated oxides prepared from an amorphous oxide was noticeably lower; it depended only slightly on the temperature of calcination and sulfate sulfur content. The catalytic behavior of the sulfated oxide in both of the reactions is indicative of the absence of superstrong proton sites. Based on the results, assumptions on the nature of formed surface compounds were made.     

固体超强酸研究的最新进展

简要介绍了近年来固体超强酸的发展。目前研究较多的固体超强酸有负载硫酸超强酸、Ｃｓ２．５盐、ＡｌＣｌ３／ＰＳ－ＤＶＢ磺酸树脂体系和全氟磺酸树脂（Ｎａｆｉｏｎ－Ｈ－Ｈ ＰＥＩＥＰ）四种。文章主要阐述了这几种固体超强酸的制备方法及它们的性质比较。     

SO(2-)4/Ti-Al-O固体超强酸的酸强度及催化性能

ＳＯ４＾２＾－／Ｔｉ－Ａｌ－Ｏ型固体超强度酸可用于邻苯二甲酸二辛酯（ＤＯＰ）的合成，当Ｔｉ／Ａｌ原子比为２时，催化性能优于ＳＯ４＾２＾－／ＴｉＯ２，且催化剂的制备条件对其酸强度，表面积和催化活性有较大的影响。使用ＴＰＤ技术对催化剂的酸强度分布进行了表征，发现在ＳＯ４＾２＾－／Ｔｉ－Ａｌ－Ｏ型固体超强度酸中，存在着三种酸中心（弱酸，中等强度酸和超强酸），中等强度的酸中心浓度与ＤＯＰ合成的催化活性有有     

WO3/ZrO2 Strong Acid as a Catalyst for the Decomposition of Chlorofluorocarbon (CFC-12)

IntroductionChlorofluorocarbons(CFCs) diffusing to the stratosphere isa major reason forozone de-pletion[1 ] .Also CFCshasbeen claimed to be notoriousforitsgreenhouseeffect[2 ] .So,recent-ly it has become very important to eliminate CFCs as far as protecting the ozone layer sur-rounding the earth is concerned.Among various kinds of approaches to do destruction toCFCs,the catalytic decomposition seems to be the most practical and energetically favorableone,especially for treating small amo…     

SO4^2—／MXOY型固体超强酸及其催化酯化

ＳＯ４＾２－／ＭＸＯＹ型固体超强酸用作酯化反应的催化剂，具有催化活性高、选择性好、易与产品分离、无污染、可重复利用等优点。本文综述了ＳＯ４＾２／ＭＸＯＹ型固体超强酸的研究进展及其在酯化反应中的催化作用。探讨了这类固体超强酸的制备条件、表面结构及其用作酯化催化剂的性能和寿命等问题。     

Acidity and Catalytic Activity of Sulfate Modified Mixed Oxides of Tin and Praseodymium

A comparitive study of the acid-base properties and physico-chemical characteristics of pure SnO₂, sulfated SnO₂ and sulfated binary oxides of Sn and Pr was done. The data were correlated with the catalytic activity of the oxides towards benzoylation of toluene.     

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.     

S~2O~8^2^-处理的ZrO~2固体超强酸上的正丁烷异构化反应

首次报道了由浸渍过硫酸根的方式制备固体超强酸。讨论了焙烧温度、浸渍浓度以及ZrO~2前驱体沉淀条件对样品性质的影响,并研究了它们对正丁烷异构化反应性能。实验结果表明,600-650℃焙烧、0.25-0.50mol/LS~2O~8^2^-浸渍反加沉淀的ZrO~2具有最高超强酸性。与相同条件下制备的SO~4^2^-/ZrO~2相比,S~2O~8^2^-/ZrO~2上正丁烷250℃异构化活性是SO~4^2^-/ZrO~2的2倍,可能是由于它具有较多的中强酸位并具有与SO~4^2^-/ZrO~2不同的活性位结构。     

Adsorption and desorption of small molecules for the characterization of solid acids

The relative acid strength and acid amount of solid acids has been determined from the adsorption and desorption of small molecules, such as argon. The order of activation energy for desorption of Ar from a solid acid, determined using temperature-programmed desorption (TPD), is sulfated zirconia > Cs_2.5H_0.5PW₁₂O₄₀ > proton-type zeolites > silica–alumina. The adsorption isotherms were analyzed using Langmuir and Henry equations. The Henry-type adsorption isotherms were also analyzed using the theory of Cremer and Flügge. The heat of Ar adsorption was 22 kJ mol⁻¹ for sulfated zirconia and ca. 17 kJ mol⁻¹ for mordenite, ZSM-5, and beta-zeolite. Molybdenum oxides reduced at 623 and 773 K exhibited a large heat of adsorption (19.3 and 19.7 kJ mol⁻¹, respectively), and these materials are classified as superacids. W-Nb mixed-oxides and tungstated tin oxide (calcined at 1373 K), which are newly developed solid acids, had a heat of adsorption of 18.1 and 16.9 kJ mol⁻¹, respectively. The type of acid site could be distinguished by comparing the heat of adsorption of Ar and N₂. Our data indicate that Ar is useful for the characterization of solid acids.     

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.     

水热合成超细晶粒A-/MxOy固体超强酸

 A-/MxOy是一种新的固体超强酸催化材料,由单价酸根负载于金属氧化物上组成,它不同于传统的固体超强酸SO2-4/ZrO2. 在水热合成的条件下金属盐和碱沉淀剂发生均匀的水解沉淀反应,生成A-/MxOy固体超强酸,这种合成方法被称作“均匀沉淀法”. 采用“均匀沉淀法”可以一步直接合成具有小于10 nm超细晶粒的A-/MxOy固体超强酸催化材料. 对“均匀沉淀法”合成A-/MxOy固体超强酸的影响因素和规律性进行了详细的考察.     

铜钴尖晶石复合氧化物催化剂的组成对二甲苯完全氧化反应催化性能的影响

具有特定结构的复合氧化物,如ABO3,A2BO4及AB2O4等对某些反应比单一氧化物具有更好的催化性能[1,2]. 然而,有关尖晶石型复合氧化物AB2O4对有机物燃烧反应催化性能的研究相对较少,且常用的模型反应大都是一氧化碳或甲烷的催化氧化反应[3]. 超微粒子由于具有大的比表面积和高的表面能等特性,在催化领域已日益引起人们的重视[4]. 低温固相合成是近十几年发展起来的一种新的超细粒子制备方法[5]; 它具有不使用溶剂,无废液排放,工艺过程简单,能耗低等优点,属于对环境友好的“绿色化学”. 目前,此法在合成多组分复合氧化物及催化化学中的应用仍不多见. 本文以含有结晶水的醋酸铜和醋酸钴为原料,采用低温固相合成法制备了单组分氧化铜和氧化钴,以及三种不同铜钴比的铜钴尖晶石型复合氧化物,并以二甲苯氧化为模型反应,采用XRD,BET及程序升温还原(TPR)等手段进行了研究.     

Defect magnesium oxides containing acetate and nitrate ion fragments incorporated in the oxide structure

The results of studies on the synthesis of defect magnesium oxides by MgO hydration in salt solutions are summarized. The incorporation of oxygen-containing salt anions into the anionic hydroxide/oxide framework is described. In this case, the anion residue whose oxygen atoms belong to the oxygen framework of the oxide is incorporated in the octahedral oxygen cell of the oxide to occupy the place of a virtual magnesium cation. A portion of cationic vacancies remains free, whereas a portion is occupied by the transformed anion residue with a positive charge other than 2+. As a result, defect magnesium oxides are formed as substitutional solid solutions. The structure and charge heterogeneity of defect oxides is responsible for their high catalytic activity.     

Sulfated and phosphated mesoporous Nb oxide in the benzylation of anisole and toluene by benzyl alcohol

Materials possessing the high acidities of sulfated zirconia and the diffusion properties of mesoporous oxides are predicted to have numerous applications in the petrochemical industry. Because of surface deactivation and loss of structure under highly acidic conditions, there are few examples of materials which meet these specifications. In this work, mesoporous Nb oxide was treated with 1 M sulfuric acid or phosphoric acid and evaluated for their catalytic activities in the benzylation of toluene or anisole with benzyl alcohol. Characterization by XRD, nitrogen adsorption/desorption, and TEM demonstrated that the mesostructure was surprisingly stable to acid treatment. Pyridine adsorption and infrared spectroscopy (IR) showed a mixture of Lewis and Bronsted sites before and after acid treatment. Titration with a series of indicators demonstrated that sulfated mesoporous Nb oxide possesses a pKa of -8.2 and 31.784 mmol/g acid sites, roughly 100 times stronger than either bulk phosphated or sulfated niobia, which both possess pKa values in the range of -3.0. The best catalytic results in this study were achieved when using mesoporous Nb oxide treated with sulfuric acid; the conversion of benzyl alcohol with anisole to the benzylation product was 100% in 30 min, which is 200 times faster than the bulk catalyst. The extremely high activity was rationalized by the high number of strong Br?nsted sites on the surface coupled with the superior diffusion properties of the mesoporous system.     

有氧气氛中碱金属改性CuAl复合氧化物催化分解N2O的活性

合成了Cu/Al原子比分别为2.0、3.1、4.1的CuAl类水滑石样品,焙烧得到CuAl复合氧化物。在Cu/Al原子比为3.1的CuAl氧化物表面浸渍碱金属盐溶液,制备改性CuAl复合氧化物,用AES、XRD、FT-IR、BET、H₂-TPR、XPS等技术对催化剂进行了结构表征,考察了CuAl复合氧化物组成、碱金属助剂类型和K的前驱物对改性催化剂在有氧气氛中催化分解N₂O活性的影响。结果表明,Na、K、Cs改性CuAl复合氧化物均提高了催化剂活性,但K助剂的增强效应最显著;钾的不同前驱物改性CuAl复合氧化物的催化活性有显著差异,加入碳酸钾、草酸钾提高了催化剂的活性,而加入醋酸钾、硝酸钾反而降低了催化剂活性。优化出的K改性CuAl复合氧化物催化剂在含氧含水气氛的N₂O分解反应中表现出了较高的活性。     

Hydrogen transfer reaction of cyclohexanone with 2-propanol catalysed by CeO2-ZnO materials: Promoting effect of ceria

Ce-Zn-O mixed oxides were prepared by amorphous citrate process and decomposition of the corresponding acetate precursors. The resulting materials were characterised by TGA, XRD, UV-Vis-DRS, EPR, SEM and surface area measurements. XRD and DRS results indicated fine dispersion of the ceria component in the ZnO matrix. EPR results clearly indicate the presence of oxygen vacancy and defect centres in the composite oxide. Addition of CeO₂ to ZnO produced mixed oxides of high surface area compared to the pure ZnO. Hydrogen transfer reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity of ZnO. Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction. The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity. Dedicated to Professor C N R Rao on his 70th birthday     

Promotion of Catalytic Properties of Sulfated Zirconium and Aluminum Oxides with Carbon Tetrachloride

The promoting effect of minor amounts of carbon tetrachloride on the catalytic activity and working life of sulfated zirconium and aluminum oxides is considered for the example of isobutane alkylation with butenes.     

铜锆复合氧化物的结构对其催化选 择还原－氧化氮性 能的影响

用浸渍法和共沉淀法分别制得CuO---ZrO~2复合氧化具物有不同的选择还原NO~x的催化性能,采用XRD,BET,EXAFS和H~2---TPR等手段对样品进行了表征,发现浸渍法制备的样品具有的比表面较大,氧化锆被稳定在四方相。EXAFS实验表明,浸渍法制得样品的铜离子填入氧化锆表面空穴中,并以Cu^2+形式存在;500℃焙条件下用共沉淀法引入的铜离子可部分取代锆离子,在氧化锆体相高度分散形成均匀的无定形固溶体,铜离子在氧化锆体相的高度分散是形成表面弧立铜物种的关键。溶入氧化锆体相的铜离子在取代部位由于局部负电荷而使氧化性降低,是共沉淀法制备样品具有较高催化活性的主要原因。     

Calorimetric and FTIR study of the acid properties of sulfated titanias

Titanium oxides of different surface areas were sulfated then calcined to convert the solid to a strong acid. The amount of sulfur retained by the solid and the thermal stability of the resulting sulfate are controlled by the dispersion of the initial oxide. The acid properties were determined by gravimetry at 383 K, calorimetry using ammonia adsorption at 353 K, and by quantitative analysis of the infrared spectra of pyridine retained after evacuation at 423 K. A good agreement was observed between the different determinations. At low coverage of ammonia, sulfated titanias show a much lower heat of adsorption, and the IR study of NH3 adsorption shows that the first doses of NH3 dissociate at the surface with the formation of OH species. The lower heat of adsorption is then attributed to the contribution of NH3 dissociation to the differential heat of adsorption. IR spectroscopy indicates that NH3 reacts with sulfates and may lead to the transformation of disulfate species into monosulfate species on sulfated titania dioxide. A band at ca. 3574 cm-1 has been assigned to nu(OH) of monosulfate species. This particular behavior makes it difficult to appreciate the initial acidity of these sulfated oxides.     

Preparation of Mixed Co and Cu Oxides via Thermal Decomposition of Their Oxalates,and Study of Their Catalytic Properties

Mixed oxides were prepared by the thermal decomposition of the oxalates of cobalt(II) and copper(II) coprecipitated from aqueous solution or made by mechanical mixing. The compositions and structures of the oxides were confirmed by means of TG and X-ray powder diffraction spectroscopy. The catalytic behaviour of the oxides obtained was studied by using the decomposition of H₂O₂ as a model reaction. The results were compared with those on the oxides produced from the thermal decomposition of mechanically mixed oxalates. The catalytic activities of the mixed oxides were found to be lower than that of pure cobalt oxide, but higher than that of copper oxide. This result was interpreted in terms of the relative standard reduction potential of the catalyst as compared with that of H₂O₂. The catalytic activity of the mixed oxides obtained from the coprecipitate was found to be lower than that of the oxides obtained from the mechanical mixture at the same temperature. As the temperature of preparation was increased, the catalytic activities of the oxides obtained decreased. This was attributed to the solid-solid interactions, which gave a new phase with lower catalytic activity than those of the interacting phases. This revised version was published online in July 2006 with corrections to the Cover Date.