Role of the Zeolitic Environment in Catalytic Activation of Methanol

We present an extensive study of the initial stages of the methanol to gasoline conversion in the framework of the ab initio molecular dynamics approach. We investigate the effect of different zeolite environments, methanol loading, and temperature and show that, for understanding the initial adsorption and activation of the adsorbed species, all three factors need to be considered simultaneously. The results allow us to develop a simple model for the activation of the methanol molecule, which elucidates the role of both the zeolite framework and the methanol solvent. The zeolite framework plays an active role in methanol protonation. The solvent significantly softens the C−O bond of the methoxonium, rendering it very anharmonic. High mobility of the methoxonium cation, promoted by some zeolite frameworks, prevents it from forming hydrogen bonds with the active sites and the solvent leading to the activation of the methoxonium species. This picture is shown to be consistent with the experimental infrared spectra.