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

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 CC bond. In our mechanism, the reaction, at 400 °C, proceeds via a two-step process: (1) the breaking of the CO 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 H2O, CH4, and CH2OH+ and (2) a simultaneous proton transfer from methane to water, and direct CC bond formation between the methyl anion and CH2OH+, resulting in the formation of ethanol. The CC bond forming process has the higher barrier, with an activation energy of about 100.49 kJ/mol.