Abstract: A process for cracking hydrocarbon feedstocks by contacting such stocks under cracking conditions with a composite catalyst comprising an improved hydrogen exchanged Y-type zeolite component and an amorphous inorganic matrix component. The use of this catalyst yields cracked naphthas of increased olefinic content for the production of lead-free high octane gasoline. Further improvement in the levels of C.sub.3 and C.sub.4 olefins can be realized by incorporating a portion of calcined rare earth exchanged Y-type zeolite into the composite catalyst.

Abstract: Uranium oxide or uranium and silver oxides in combination with hydrogen or rare earth oxides are exchanged into zeolites as components of zeolite cracking catalysts to increase the olefin content of the gasoline and, thus, enhance the yield of high octane components as well as reduce the coking tendency of the catalyst.

Abstract: An amorphous hydrocarbon cracking catalyst of high activity is prepared by mixing solutions of sodium silicate and sodium aluminate, allowing the gel and age, acidulating said gel to precipitate the excess aluminate and ion exchanging after drying to accomplish removal of the alkali metal.

Abstract: A stable rare earth exchanged zeolite having high catalytic activity and improved coke selectivity is prepared by a series of exchange steps whereby the rare earth is introduced into the zeolite in a multi-step e.g., two step manner. The method comprises exchanging a sodium zeolite to less than 4.0 weight percent Na.sub.2 O, exchanging with rare earth to give an initial rare earth oxide content of 0.3 to 5 weight percent, calcining, and further rare earth exchanging the zeolite to give a final rare earth content of 1.0 to 10 weight percent.