(324g) A DFT Study of the Mechanism of Zeolite-Catalyzed Carbonylation of Dimethoxymethane – a Critical Step along the Path From Synthesis Gas to Mono-Ethylene Glycol

Recent experimental studies have shown that zeolites will catalyze the carbonylation of dimethoxymethane (DMM) carbonylation to produce methyl methoxyacetate (MMAc), a product that can readily be converted to monoethylene glycol (MEG), thus opening up a pathway to the MEG from synthesis gas. We have conducted a quantum-chemical study of DMM carbonylation to form MMAc catalyzed by the zeolites MFI and FAU. We report elementary steps and activation their energies. The reaction occurs in three steps: initiation, carbonylation of methoxymethoxy species adsorbed on the zeolite active site, and methoxylation of the carbonylated intermediate by DMM. We discovered that: (a) CO does not adsorb on the zeolite prior to the reaction; (b) the transition state of each step is carbocationic in nature, and (c) the relative rates of the three steps are different for different zeolites. We performed energy decomposition analysis and compared the effects of the MFI and FAU structure on the different contributions to the energy of the intermediates and of the transition states. The results of this work help to explain the relative activities of FAU and MFI based upon the structure of the zeolite framework.