The Catalytic Performance of 14-Membered Ring Zeolites

We have synthesized and carried out extensive characterization (IR, MAS NMR, TPD, Ar and N2adsorption, and scanning electron microscopy) of two unidirectional 14-membered ring zeolites (CIT-5 and UTD-1) and one unidirectional 12-membered ring zeolite (SSZ-24). All three samples have comparable acidic properties and are of comparable crystal size. The performance of these three zeolite samples in the catalytic cracking ofn-decane, triisopropylbenzene, 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—such as triisopropylbenzene—can be converted inside the 14-membered ring channels of a UTD-1 zeolite, but not inside the pores of CIT-5 or SSZ-24. In the catalytic cracking of complex feedstock, all three of the unidirectional zeolites are inferior in performance to the conventional tridirectional zeolites, such as USY or Beta zeolites.