NSF/EPA: Hydrogen Formation and Transfer in Alkane Reactions Catalyzed by Cation-Modified Zeolites

点击翻译按钮获取中文摘要

Abstract - Enrique Iglesia CTS-9613632 Environmental impact during processing of fuels and their precursors can be reduced via efficient utilization of hydrogen. This critical component of many petroleum processing operations is used nonselectively in reactions such as isomerization (those that involve hydrogen-transfer steps), dehydrocyclization, desulfurization and hydrotreatment in general. A limit to the selectivity of current catalysts used for those reactions is the insufficient knowledge about catalytic sites requirements. This proposal formulates a study of cationic sites exchanged into pentasil zeolites, in terms of structure, spectroscopy, and catalytic reactions, as means of characterization. The author has produced related work in recent projects, and successfully demonstrated the use of the techniques to be exploited in this project. The structure of exchanged cations will be determined by X ray absorption spectroscopy. The H-transfer and disposal by those sites will be examined using kinetic and H-D exchange reactions and in-situ infrared spectroscopy. Coupled dehydrogenation-hydrogenation reactions will be enhanced by addition of hydrogen scavengers such as O2, CO2, CnHx, etc., and the role that such coupling has on alkane dehydrogenation selectivity will be determined. Sulfur-containing compounds will be explored as hydrogen acceptors for activation of alkanes, and the hypothesis will be tested that more efficient hydrodesulfurization of such compounds is possible by means of coupled hydrogen transfer. Infrared spectroscopy of adsorbed thiophenic compounds on Lewis acid sites in ZSM5 in the presence of light alkanes or H2, isotopic exchange and chemical test reactions with sulfur-containing molecules will also be part of this study.