Catalytic Partial Oxidation of Lower Alkanes

这是一项涉及甲烷和乙烷活化和部分氧化的催化现象的基础研究。目的包括研究负载型和非负载型钒和钼催化剂上负责烷烃活化和氧插入的活性位点的性质，碱金属、磷和卤化物等改性剂（促进剂和抑制剂）对这些位点选择性的控制，反应物和添加剂在反应方案中的作用，以及负责甲烷和乙烷部分氧化的反应网络。催化剂在反应前后均采用BET表面积测量、孔径分布、x射线衍射、x射线荧光、激光拉曼光谱、x射线光电子能谱、俄歇电子能谱、二次离子质谱和热分析技术进行表征。原位激光拉曼表征与同位素标记相结合，以确定氧插入点。稳态和瞬态动力学研究和同位素标记被用作机械探针来检查部分和完全氧化的催化途径。甲烷和乙烷是容易获得的廉价原料，将甲烷转化为甲醛或甲醇，将乙烷转化为乙烯或乙醛一直是催化技术的主要目标。这些转化很容易实现，但隔离这些产品所需的精细控制一直难以捉摸；大多数过程主要产生一氧化碳和二氧化碳，它们是由竞争性反应途径和独立产物的进一步氧化形成的。更好地了解操作机制将允许新的控制策略来解决这一经典问题。

ABSTRACT CTS-9412544 Umit Ozkan This is a fundamental study of the catalytic phenomena involved in the activation and partial oxidation of methane and ethane. The objectives include investigation of the natures of the active sites responsible for alkane activation and oxygen insertion on supported and unsupported vanadia and molybdena catalysts, control of selectivity on these sites by modifiers (both promoters and inhibitors) such as alkali metals, phosphorus, and halides, the roles of coreactants and additives on the reaction schemes, and the reaction networks responsible for partial oxidation of methane and ethane. Catalysts are characterized both before and after reaction using BET surface-area measurements, pore size distribution, X-ray diffraction, X-ray fluorescence, laser Raman spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, secondary-ion mass spectroscopy, and thermal analysis techniques. In - situ laser Raman characterization is combined with isotopic labelling to identify oxygen insertion sites. Steady- state and transient kinetic studies and isotopic labelling are used as mechanistic probes to examine the catalytic routes to partial and complete oxidation. Methane and ethane are readily available inexpensive feedstocks, and the conversion of methane to formaldehyde or methanol and ethane to ethylene or acetaldehyde has been a major objective of catalytic technology. These conversions are easy to achieve, but the fine control needed to isolate these products has been elusive; most processes produce mainly carbon monoxide and carbon dioxide which are formed both from competitive reaction pathways and from further oxidation of the indended products. Better understanding of the operative mechanisms will permit new control strategies to solve this classical problem.