A theoretical investigation of the methylation of alkenes with methanol over acidic zeolites

A quantum chemical investigation of the methylation of alkenes by methanol over acidic zeolite catalysts has been performed. A cluster model consisting of four tetrahedrally coordinated atoms (T-atoms) has been used to represent the zeolite. The activation barrier for methylation is dependent on the size and substitution pattern of the alkene reactant. The results can be rationalized by considering the relative energies of the carbocations that describe the reaction path. Implications for methanol-to-hydrocarbon chemistry are discussed. The effect of zeolite acidity on the activation barrier has also been probed. The barrier decreases when the catalyst acidity is increased.