GOALI: Characterization of Active Sites in Zeolites for Hydrocarbon Cracking Reaction

摘要：本文研究了用于烃类裂解的沸石催化剂的活性位点。蒸HY沸石中的强Bronsted位点是通过用胺（如吡啶）中毒，然后通过硅基化阻断未中毒（较弱）的羟基位点来分离的。然后对强位点进行仔细的再生，使它们与弱位点分开进行研究。这是通过核磁共振、红外光谱和吸附碱性探针分子的微量热法来完成的。另一组实验旨在探索框架外阳离子对催化活性和羟基性质的影响。通过将沸石羟基与引入气相的金属的氯或烷基反应，将框架外的铝、镓或镧离子引入HZSM-5中。随后的水解产生了分散的框架外物质，可以表征其结构、阳离子位置和催化活性。烃类裂解是原油制汽油的关键步骤。虽然HY沸石蒸煮的结果是一个非常活跃的裂化催化剂，但造成这一现象的因素仍然是一个谜。本研究试图识别和分离那些负责催化活性的位点，并研究它们与沸石基质中框架外物质的相互作用。这是西北大学和阿莫科石油公司的合作研究成果。＊＊＊

ABSTRACT Harold Kung This is an investigation of the active sites in zeolite catalysts used for cracking of hydrocarbons. Strong Bronsted sites in steamed HY zeolites are isolated by poisoning with an amine such as pyridine and then blocking the unpoisoned (weaker) hydroxyl sites by silylation. Careful regeneration of the strong sites then allows them to be studied separately from the weaker sites. This is done using nuclear magnetic resonance, infrared spectroscopy, and microcalorimetry of adsorption of basic probe molecules. A separate set of experiments is designed to explore the effects of extraframework cations on catalytic activity and hydroxyl-group properties. Extraframework aluminum, gallium, or lanthanum ions are introduced into HZSM-5 by reacting the zeolite hydroxyl groups with the chloride or alkyl of the metal introduced in the gas phase. Subsequent hydrolysis gives dispersed extraframework species that can be characterized for structure, cation location, and catalytic activity. Hydrocarbon cracking is a crucial step in the production of gasoline from crude oil. Although it is well established that steaming of HY zeolite results in a very active cracking catalyst, the factors responsible for this remain mysterious. This study is an attempt to identify and to isolate those sites that are responsible for the catalytic activity and to study their interactions with extraframework matter in the zeolite matrix. This is a collaborative research effort between Northwestern University and Amoco Oil Company. ***