CHARACTERIZATION OF ZEOLITE-CRACKING CATALYSTS

The revolutionary zeolite cracking catalyst (synthetic Linde X and Y) was introduced commercially over 28 years ago, but considerable effort is still being expended on the improvement of its stability and catalytic properties. Decreasing the aluminum content of the zeolite framework and the replacing the rare-earth with the hydrogen form have greatly increased activity at the expense of stability. The thermal stability of the faujasites is fairly well understood, while the reasons for the increased catalytic activitity are still not fully known. The use of traditional and new techniques to elucidate the structure of synthetic faujasites with different silica alumina ratios, dealuminated by steaming and chemical treatment, and with and without faulting will be described. The migration and fixation of cations and the role of aluminum in the dealumination of the zeolite will be discussed. Very clean and highly dealuminated samples have been prepared that have removed some of the variables in determining the state of the framework and extra-framework aluminum.