Solid Superacid Catalysts Based on Tungsten Oxide

CTS-9510575这项由加州大学伯克利分校、埃克森公司和墨西哥伊兹塔帕拉帕的大都会自治大学共同开展的工作，涉及以孤立物种、团簇或薄膜的形式分散在氧化锆或二氧化钛表面的基于钨的固体超强酸的合成和表征。前人的研究表明，氧化钨对高碳烷烃的异构化反应具有催化活性，而不会引起其他超强酸的裂解。为了提高催化剂的催化活性，需要较高的比表面积。这项工作包括详细研究高比表面积的锆氧化物和钛氧化物的沉淀以及钨酸基在其表面的分散所涉及的固态过程。使用X射线衍射和吸收技术、电子显微镜、红外和拉曼光谱进行了结构研究；使用位置滴定和丙烯和二甲基环己烷的催化反应来探索酸位密度和化学。这些研究与使用原位红外光谱和同位素跳跃技术的机理研究相辅相成。支链烷烃在汽油、润滑油组分和化工原料中作为辛烷值增强剂具有很大的价值。传统上，它们是使用几种使用液态酸的工艺之一来制造的，但人们普遍认为，这些工艺很快就会被使用固体酸的新工艺所取代。这一举措寻求的优势包括更容易遏制、腐蚀性更低、对环境友好和提高选择性。这项工作得到了化学反应过程计划(CTS)、固态化学和聚合物计划(DMR)和美国人计划(INT)的联合支持。***

ABSTRACT CTS-9510575 This joint effort between the University of California at Berkeley, Exxon Corporation and the Metropolitan Autonomous University at Iztapalapa, Mexico, involves the synthesis and characterization of solid "superacids" based on tungsten oxide dispersed as isolated species, clusters, or films on the surface of zirconia or titania. Previous work has shown that tungsten oxide on zirconia has catalytic activity for isomerization of higher alkanes without the cracking caused by other "superacids". In order to improve the catalytic activity, higher surface areas are desirable. This work includes detailed study of the solid-state processes involved in the precipitation of high-surface-area zirconium and titanium oxides and in the dispersion of tungstate groups on their surfaces. Structural studies are performed using X-ray diffraction and absorption techniques, electron microscopy, and infrared and Raman spectroscopies; acid-site densities and chemistry are probed using site titrations and catalytic reactions of propylene and dimethylcyclohexane. These studies are complemented with mechanistic studies using in-situ infrared spectroscopy and isotope jump techniques. Branched alkanes have great value as octane enhancers in gasoline, lubricant components, and chemical feedstocks. Traditionally, these have been made using one of several processes employing liquid acids, but it is generally accepted that these processes will soon be replaced by new processes using solid acids. Among the advantages sought in this move are easier containment, less corrosiveness, environmental benignity, and improved selectivity. This effort is supported jointly by the Chemical Reaction Processes Program (CTS), the Solid State Chemistry and Polymers Program (DMR), and the Americans Program (INT). ***