Zeolite Effects on the Cracking of Long Chain Alkyl Aromatics

Long chain alkyl aromatic compounds crack by a number of competing reaction pathways including dealkylation, side chain cracking, and self-alkylation. Cracking studies of 1-phenylheptane over zeolites Y, beta, mordenite, and ZSM-S, as well as silica-alumina, show that the catalyst can significantly alter the relative importance of these pathways. For example, large pore zeolites give significant amounts of bicyclic reaction products, whereas the medium pore sieve ZSM-S gives almost no bicyclic products. Other catalyst properties such as Si/Al ratio, adsorption characteristics, and geometrical factors also affect cracking catalyst performance.