Application of transition path sampling methods in catalysis: A new mechanism for C C bond formation in the methanol coupling reaction in chabazite

P R O We describe the application of transition path sampling methods to the methanol coupling reaction in the zeolite chabazite; these methods have only been recently applied to complex chemical systems. Using these methods, we have found a new mechanism for the formation of the first C C bond. In our mechanism, the reaction, at 400 C, proceeds via a two-step process: (1) the breaking of the C O bond of the chemisorbed methoxonium cation, followed by the transfer of a hydride ion from the remaining methanol molecule to the methyl cation, resulting in the formation of H 2O, CH 4, and CH 2OH þ and (2) a simultaneous proton transfer from methane to water, and direct C C bond formation between the methyl anion and CH 2OH þ, resulting in the formation of ethanol. The C C bond forming process has the higher barrier, with an activation energy of about 100.49 kJ/mol. # 2005 Published by Elsevier B.V.