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. ***
