CRACKING BEHAVIOR OF ZEOLITES WITH CONNECTED 12-MEMBER AND 10-MEMBER RING CHANNELS - THE INFLUENCE OF PORE STRUCTURE ON PRODUCT DISTRIBUTION

n-Heptane has been cracked on a CIT-1 zeolite which has connected 12- and 10-member ring (MR) channels, and its behavior was compared with t hat of MCM-22 with nonconnected 12- and 10-MW channels, and SSZ-24 and BETA with unidirectional and tridirectional 12-MR channels, respectiv ely. The kinetic rate constant is highest for CIT-1, and the decay con stant is lowest. From the selectivity point of view, its behavior can be better represented by a system with large cavities (the intersectio ns between the 12- and 10-MR) connected by windows. This gives a behav ior typical of that of large pore zeolites. CIT-1 produces a remarkabl y high selectivity to i-C-4, and specially to isobutane. This zeolite shows promise as an additive in FCC operations. (C) 1997 Academic Pres s.