C-C bond scission of carbocations in zeolite pore cavity showing enzyme-like recognition

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The conversions of C_2H_4 , pentenes, and hexenes were examined. The catalytic performance was compared, in order to investigate the role of the pore volume of zeolites with8-, 10-, and 12-membered rings in the selective production of C_3H_6 . The selectivity for C_3H_6 was crucially dependent upon the pore volume of the zeolite. Highly selective production of C_3H_6 from olefins (C_2H_4,pentenes, and hexenes) can be accomplished by employing a new concept: adjusting the pore volume of a zeolite to accommodate the volume of an olefin and/or its carbenium cations, as opposed to a conventional molecular sieve approach. For example, an unimolecular cracking of pentenes into C_3H_6 and C_2H_4 involving primary cations can be controlled by the pore volume of a zeolite.Furthermore, the reaction mechanism for the production of C_3H_6 from C_2H_4 was also investigated. C_3H_6 was produced by the β-scission of the same specific octyl carbocations in the conversions of both butene and C_2H_4.