First principles calculation of the free energy barrier for the reaction of methanol in a zeolite catalyst

Abstract

First principles calculations have significantly advanced the understanding of the first stages of the methanol to gasoline conversion process in zeolite acid catalysts. The theoretical techniques used in first principles total energy pseudopotential calculations are described in this paper and the application of these calculations to investigate the first stages of the reaction of methanol in acid zeolites is described. First principles total energy pseudopotential calculations have shown that finite temperature effects are particularly important in this system. A fully ab initio calculation of the free energy barrier to the formation of dimethyl ether (DME) from methanol has been performed. It is found that the entropy of the system varies considerably along the reaction path and that the conversion of methanol to DME is entropically driven.