IN-SITU STUDY OF REACTIVE INTERMEDIATES OF METHANOL IN ZEOLITES FROM FIRST PRINCIPLES CALCULATIONS

Nonlocal periodic density functional calculations have been used to ex amine the stability of various possible reactive intermediates resulti ng from the initial adsorption of methanol in the zeolite chabazite. T he formation of dimethyl ether has been examined both for pathways via framework coordinated methyl groups and by direct condensation with t he framework acting as a solvent. Both are found to offer a reasonable energetic route to dimethyl ether, which is only hydrogen bonded in i ts bound state, proton transfer being disfavored. No evidence is found for the existence of carbenes or ylide species as local minima within the microporous environment, though trimethyl oxonium is stable with respect to dimethyl ether and a framework methoxy group.