ABSTRACT
Skeletal isomerization of olefins, paraffins, and aromatics over alu-minophosphate-based zeolites was reported by Pellet et al. Detailed analyses of the composition of cracked products from the hydrocracking and hydroisomerization of n-paraffins over ZSM-5 suggest that reactions involving tertiary carbenium ion intermediates do not take place in medium pore zeolites. Compared to large pore zeolites, such as the Ultrastable Y, the channel structure of ZSM-5 was found to exert a pronounced effect on both the relative rate of cracking to isomerization and on the isomer distribution. Song and Moffatt recently studied the ring-shift isomerization of oc-tahydrophenanthrene to octahydroanthracene over larger pore zeolites, Y, and mordenite. Aromatic amines can also undergo isomerization reactions over the medium pore zeolites. The isomerization activity of medium pore zeolites has also been studied over a variety of nonhydrocarbon aromatics and heterocyclic compounds, including dichlorotoluenes, halogenated thio-phenes and halogenated phenols.
