The interaction of methyl acetate with HZSM-5.

The methanol-to-hydrocarbons (MTH) reaction is an industrial process that converts a cheap feedstock (methanol) into more valuable alkenes and gasoline using a HZSM-5 catalyst. The mechanism has been extensively studied, but the formation of the first C-C bond is still controversial. A recent suggestion was that methyl acetate was a key intermediate in the early stages of the reaction. We wish to investigate the interaction of methyl acetate with the zeolite, in particular the methyl torsion is very sensitive to the local environment. Neutrons are essential, as only with INS is it possible to observe the region below ~1500 cm-1, as the lattice modes result in spectral opacity for infrared spectroscopy. It is in this region, where most of the intramolecular modes occur and, crucially, so do the intermolecular zeolite-methyl acetate modes. TOSCA is the instrument of choice as it provides the best resolution in this region and offers very high signal-to-noise ratio in the region below 300 cm-1 where the methyl torsions occur.