The catalytic performance of 14-membered ring zeolites

We have synthesized and carried out extensive characterization (IR, MAS NMR , TPD, Ar and N-2 adsorption, and scanning electron microscopy) of two unid irectional 14-membered ring zeolites (CIT-5 and UTD-1) and one unidirection al 12-membered ring zeolite (SSZ-24). All three samples have comparable aci dic properties and are of comparable crystal size. The performance of these three zeolite samples in the catalytic cracking of n-decane, triisopropylb enzene, and a complex industrial feed (vacuum gas oil) have been evaluated. The performance of CIT-5, a 14-membered ring zeolite, is indistinguishable from that of SSZ-24, a 12-membered ring zeolite. A large, flat molecule-su ch as triisopropylbenzene-can be converted inside the 14-membered ring chan nels of a UTD-1 zeolite, but not inside the pores of CIT-5 or SSZ-24. In th e catalytic cracking of complex feedstock, all three of the unidirectional zeolites are inferior in performance to the conventional tridirectional zeo lites, such as USY or Beta zeolites. (C) 1999 Academic Press.