Methylcyclopentane conversion catalysis by zeolite encaged palladium clusters and palladium-proton adducts

Abstract

The conversion of methylcyclopentane (MCP) has been studied over the prototype catalysts HY, Pd/HY, Pd/NaHY, and proton-free Pd/NaY. Ring opening (RO) of MCP to hexane isomers is catalyzed by Pd n clusters, but ring enlargement (RE) of MCP to cyclohexane and benzene requires metal sites and protons. It is found that catalysts containing Pd and protons, in the same zeolite cavity, are dramatically more active for RE than a physical mixture of HY and proton-free Pd/NaY. As other data indicate that protons and Pda clusters inside supercages of zeolite Y form “electrondeficient” [Pd n H] + adducts, it is proposed that these adducts expose active sites, where MCP is converted to benzene during one residence of the adsorbed molecule. This novel reaction path compares favorably with the classical “bifunctional” route which requires shuttling of reaction intermediates between metal and acid sites.