CRACKING ACTIVITY OF SOME SYNTHETIC ZEOLITES AND NATURE OF ACTIVE SITES

The activities of synthetic Y faujasites, mordenites, and L zeolite for cracking n-hexane n-heptane, and ethylbenzene were determined using a pulse microreactor. Activities of ammonium-exchanged forms after various activation procedures indicated that strong Brönsted sites were required for cracking of alkanes, but that some weaker sites may have been active for ethylbenzene cracking. Brönsted sites were also responsible for the activity of lanthanum and calcium-exchanged Y. Partial dehydroxylation increased the activity of NH4Y for n-hexane cracking, but it was not possible to determine whether Lewis sites were necessary for cracking activity on any of the zeolites tested. Optimum activation temperatures for cracking of hexane by LaY and NH4Y were similar to those found previously for benzene alkylation, suggesting common active sites for the two reactions. © 1969.