Development of zeolite-containing reforming catalysts

Copper-bearing zeolite catalysts are studied to develop a catalyst free of noble metals for obtaining high-octane components of motor fuels. The activity of the catalysts prepared on the basis of ZHM, ZHS-III-895, ZHS-III-889, and ZSM-5 zeolites with the different contents of copper is tested in the conversion of a model hydrocarbon (n-hexane). It is found that the reactions of isomerization and aromatization of n-hexane can lead to the formation of high-octane hydrocarbons in nonstandard conditions of conversion of n-alkanes: without feeding a hydrogen-bearing gas into the reaction medium at atmospheric pressure on copper-bearing high-silica zeolites, while an industrial process involving platinum catalysts is carried out under increased hydrogen pressure. The use of the recommended conditions for the conversion of hydrocarbons should lead to a reduction in the cost of final products.     

Efficient catalysts for benzene alkylation with olefins

The experimental data of benzene alkylation with ethylene and propylene in the presence of methyl and ethylchlorosilanes are presented in this article. The catalytic activity series are determined for the methyl and ethylchlorosilanes. These compounds are found to demonstrate high catalytic activity and selectivity in the alkylation reactions and can be used in place of aluminum chloride. The computational study reveals the linear dependence between the charges, acceptor capacities and activities of the catalysts in the alkylation reactions.     

Electrochemical catalysts for hydrocarbon combustion

Two series of electrochemical catalysts were prepared from sputtered Pt thin films onto two kinds of electrolyte membranes, 8 mol% Y₂O₃-stabilized ZrO₂ (YSZ), an O²⁻ conducting oxide and Na₃Zr₂Si₂PO₁₂ (NASICON), a Na⁺ one; respectively. The thickness of the Pt films varied from 8 to 120 nm. Therefore, the Pt loading was extremely low. The catalytic activity of Pt/YSZ and Pt/NASICON systems has been investigated between 200 and 500 °C for propane and propene, respectively. In spite of the low Pt loading, the Pt/YSZ electrochemical catalysts exhibited high activity for propane combustion. Furthermore, the catalytic activity can be in-situ controlled by applying electrical polarisation with high Faradaic efficiency (10³). The catalytic rate of propene deep oxidation on Pt/NASICON electrochemical catalyst was found to be limited by the number of active sites, which is low on very thin Pt films. Moreover, initial anodic polarisation indicate that Na⁺ ions are already present on the top surface of Pt, probably proceeding from the preliminary stabilisation treatment of Pt in the reactive mixture. Nevertheless, polarisation allows the tuning of the catalytic activity of the electrochemical catalysts for propene oxidation. Finally, for both kinds of electrochemical catalysts, our results have evidenced that the measurement of the open-circuit voltage during catalytic process can be an indicator of the hydrocarbon conversion.     

多级孔沸石分子筛在芳烃烷基化反应中的研究进展

多级孔沸石分子筛不仅具有微孔沸石固有的高水热稳定性和强酸性,且兼具介孔以及大孔材料的传质优势,提高了表面活性位的有效利用率,在多相催化领域表现出良好的催化性能。本文详细阐述了近年来多级孔沸石在芳烃烷基化反应中的研究进展,讨论了多级孔沸石分子筛中介孔的存在对芳烃烷基化特别是其中包含有较大分子参与的烷基化催化反应的促进作用,从分子扩散和可接近性两方面解释了多级孔沸石对催化活性、选择性和稳定性的促进作用。同时指出制备具有高度有序结构的介孔沸石,并深入研究多级孔沸石的酸性,建立沸石酸性能、孔结构与催化性能之间的关联是未来多级孔沸石的研究方向。     

苯与合成气烷基化催化剂的研究进展

对二甲苯（PX）是制备聚酯材料的重要原料,随着我国经济快速发展,对二甲苯的需求日益增长。目前PX主要通过石化路线生产,由于我国石油资源短缺,迫切需要开发基于煤化工路线的PX生产技术。通过苯与合成气烷基化制备PX是一条新的煤化工路线,近年来受到关注。本文综述了苯与合成气烷基化的最新进展,讨论了贵金属（Pt）、铜基氧化物、锌基氧化物（ZnZr、ZnCr）与沸石的复合以及负载和机械混合两类复合方式对催化效果的影响,分析了甲醇合成与烷基化反应的耦合机制以及反应条件的匹配关系;并与其他三种煤制芳烃技术,即合成气制芳烃、甲醇制芳烃以及苯与甲醇烷基化制烷基苯做了对比分析,表明该技术路线具有成本较低和工艺路线短的优势。     

芳烃烷基化催化剂的研究进展

传统芳烃烷基化催化剂存在缺陷,目前对可用于催化芳烃烷基化反应的新型催化剂的研究主要有固体酸和离子液体两个方向,其中固体酸催化剂中,研究较多的有分子筛、杂多酸、金属氧化物固体超强酸等。用于芳烃烷基化反应的离子液体催化剂主要有卤代金属和叔胺盐类、咪唑类及吡啶类组成的离子液体等。新型芳烃烷基化催化剂相比传统催化剂具有环境友好、可再生以及易与原料分离等优点,但由于其制备成本较高、易失活、循环使用寿命较短等原因,工业应用仍面临着许多困难与挑战。     

固体酸催化剂烷基化脱噻吩硫的研究进展

综述了为提高催化剂的活性、稳定性和选择性,对固体酸催化剂以及脱硫工艺进行改进的最新研究进展,指出全优适宜的烷基化脱硫固体酸催化剂及新型脱硫工艺的开发,是今后的研究方向。     

芳烃烷基化催化剂的研究进展

传统芳烃烷基化催化剂存在缺陷,目前对可用于催化芳烃烷基化反应的新型催化剂的研究主要有固体酸和离子液体两个方向,其中固体酸催化剂中,研究较多的有分子筛、杂多酸、金属氧化物固体超强酸等。用于芳烃烷基化反应的离子液体催化剂主要有卤代金属和叔胺盐类、咪唑类及吡啶类组成的离子液体等。新型芳烃烷基化催化剂相比传统催化剂具有环境友好、可再生以及易与原料分离等优点,但由于其制备成本较高、易失活、循环使用寿命较短等原因,工业应用仍面临着许多困难与挑战。     

Selective heterogeneous hydrocarbon oxidation over oxide catalysts

The heterogeneously-catalysed oxidation of hydrocarbons over oxide catalysts is reviewed. The first section of the paper deals in a general way with the structural features of hydrocarbons and relates these to the selective oxidation products which may be obtained from them. The interaction of oxygen and hydrocarbons with oxides is also considered in a general context and the kinetics of heterogeneous oxidation of hydrocarbons are discussed. The second section of the paper deals in more detail with the selective oxidation of aromatic hydrocarbons with particular reference to vanadium oxide containing catalysts. Finally, an account is given of the selective oxidation of monoalkenes to 1,3 conjugated systems and ketones over mixed oxide catalysts. The information available is considered throughout with a view to revealing those features of such systems which give rise to the selectivity.     

对甲酚烷基化反应催化剂的研究进展

主要从酸性催化剂的发展历程全面综述了分子筛、固体超强酸、离子交换树脂、杂多酸、离子液体等多种酸性催化剂的优点和缺点,并总结出对甲酚在不同催化剂作用下反应产物区域选择性的结果。通过对多种催化剂的特性和反应结果对比着重介绍了离子液体催化剂,离子液体同时拥有液体酸高密度酸性和固体酸易分离不挥发的优点,在保持着浓硫酸酸性强度的同时,还具有低蒸气压、热稳定性高、对环境无污染、功能化设计的优良特性,这为今后对甲酚烷基化反应绿色催化剂的发展提供了重要的研究方向,避免了目前工业上常用液体酸催化剂存在的污染环境设备和安全隐患等重大问题。     

Solid base catalysts for side-chain alkylation of toluene with methanol

A wide variety of solid bases, including alkali-exchanged zeolites X, Y, L and β, and alkali-impregnated carbon and magnesia, were tested as catalysts for the side-chain alkylation of toluene with methanol to form styrene and ethylbenzene. In addition, the effects of adding Group IIIA elements (B, Al, Ga, In) to the catalysts were examined. At 680 K and atmospheric pressure, the major reaction products were styrene, ethylbenzene, and carbon monoxide. Cesium-exchanged zeolite X was the most effective alkali-containing catalyst for the alkylation reaction. Of the Group IIIA additives that were tested, only boron promoted the alkylation reaction. The primary effect of adding boron was to reduce the decomposition of methanol to carbon monoxide. Apparently, boron selectively modifies the sites associated with methanol decomposition without inhibiting the sites active for alkylation. A borated Cs—carbon sample also catalyzed the alkylation reaction, demonstrating that a zeolite framework is not necessary to form the active site. Microporosity seems to play an important role in these catalysts since both the alkali-modified carbons and the zeolites are microporous.     

Cerium-containing MCM-41 materials as selective acylation and alkylation catalysts

The synthesis of Ce–MCM-41, Al–MCM-41 and Ce–Al–MCM-41-type mesoporous materials was carried out hydrothermally by refluxing the gel with magnetic stirring under atmospheric pressure for 24–36 h. The samples were characterized thoroughly in order to obtain the structural and textural properties, which reveal the presence of well-ordered M41S-type materials. The Ce–MCM-41 samples were used for catalytic acylation of alcohols, thiols, phenols and amines show good activity and selectivity including high chemoselectivity towards selective monofunctional acylation of bifunctional compounds. Quite importantly the acylation of bulky molecules such as cholesterol, ergesterol and β-sitosterol could be achieved using Ce–MCM-41 as solid catalyst. The presence of Ce along with Al in Ce–Al–MCM-41 was found to have synergistic effect as Ce–Al–MCM-41samples were more active catalysts for alkylation of naphthalene compared to either Ce–MCM-41 or Al–MCM-41 with comparable Si/Al or Si/Ce molar ratio.     

Anodic behaviour of aluminium in halogenated media. Electrogenerated alkylation catalysts

The anodic dissolution of aluminium in electrolytes in which alkyl- mono- or polyhalides are present together with aromatic compounds, gives rise to the in situ formation of the well known Friedel-Crafts catalysts, promoting the chemical alkylation of the aromatic ring with the halide. A chemical reaction dissolving aluminium is activated by the electrochemical one, and , after the passage of a limited amount of charge, becomes predominant. At this stage the process becomes strongly exothermic, cannot be controlled by electrochemical means and proceeds until one of the reagents, aluminium or the halide, is almost completely consumed. The resulting “red oils” are good catalysts even for alkylations in which halides different from the starting one are employed.     

甲苯甲醇选择性烷基化催化剂研究进展

甲苯甲醇烷基化是生产对二甲苯的一条新工艺路线,其原料价格低廉、对二甲苯选择性高、产物分离简单,因此引起国内外学者的极大关注。活性和选择性高、稳定性好的催化剂是甲苯烷基化技术应用的关键。综述了国内外甲苯甲醇烷基化催化剂的研究进展,包括水热处理法、浸渍法、预积炭法等。指出水蒸气改性可以提高催化剂寿命,浸渍法的操作简单、重复性好,这两种方法是目前分子筛改性的常用方法。通过对分子筛改性来制备高选择性甲苯甲醇烷基化催化剂己经不再是难题,在维持较高活性和选择性的基础上,提高催化剂稳定性,使其具备工业应用价值,是未来甲苯甲醇烷基化技术研究的重点。     

甲苯侧链甲醇烷基化催化剂的研究进展

苯乙烯是十分重要的基础有机原料,工业化的主要工艺路线是苯和乙烯烷基化制得乙苯,然后乙苯催化脱氢制得苯乙烯。相比于传统生产工艺,甲苯侧链甲醇烷基化一步生产苯乙烯具有原料廉价、工艺路线短、原子利用率高等优势,具有重要的研究意义和应用前景。对近年来甲苯侧链甲醇烷基化制苯乙烯的催化剂体系、反应工艺和反应机理等方面的研究进展进行归纳、总结和评述,并对研究工作的发展趋势进行展望。     

Tailoring catalysts for hydrodechlorinating chlorinated hydrocarbon contaminants in groundwater

A palladium-on-zeolite catalyst has been optimized for treating groundwater contaminated with halogenated hydrocarbon compounds (HHCs) by hydrodechlorination with dissolved hydrogen. Aqueous sulfite was used as the model poison and the dechlorination of 1,2-dichlorobenzene (1,2-DCB) was used as the model reaction to study the relationship between zeolite hydrophobicity, pore size, and resistance against deactivation. The optimal Pd support is a hydrophobic zeolite Y with a pore size of 0.74 nm tailored to exclude reactive ions from internal sites, to minimize deactivation and inhibition, and to maximize the transformation rate of HHCs. Common halogenated contaminants including chlorinated ethylenes and aromatics are removed within minutes. Catalyst efficiency under groundwater treatment conditions was demonstrated in a bench-scale column experiment.     

Interparticulate coke formation during hydrocarbon cracking on zeolite catalysts

A thermogravimetric study of coking of various C₆–C₇ hydrocarbons on HY and REY zeolites was performed using a Cahn microbalance modified to allow in-situ measurements of catalyst weight changes during reaction under flow conditions. Mass transfer effects during the reaction were found to play an important role in the coking process of the static catalyst bed. The results indicate that catalytic coke can form in the void space between zeolite particles in such a way as to deter molecular diffusion through the catalyst bed.     

甲苯甲醇烷基化合成对二甲苯催化剂研究进展

甲苯甲醇烷基化是新型高选择性合成对二甲苯的方法,可以解决石化行业甲苯和甲醇过剩问题,具有较高的工业开发价值。在具有B酸中心及特殊孔结构的分子筛催化下,甲苯甲醇发生苯环上亲电取代反应得到对二甲苯。甲苯甲醇烷基化催化剂主要有Y沸石催化剂、SAPO及MCM-22和ZSM-5分子筛催化剂等,研究较多的是ZSM-5分子筛催化剂。通过对ZSM-5分子筛进行金属、非金属或复合改性后,可以显著提高烷基化反应转化率和选择性。未来研究的主要目标是获得选择性高且稳定性好的催化剂。