Direct Observation of Acetyl Group Formation from the Reaction of CO with Methylated H-MOR by in Situ Diffuse Reflectance Infrared Spectroscopy

Methanol to olefins (MTO) is an important and economical process for methanol to olefins conversion, which can potentially lower the dependence of petrochemicals on the expensive liquid hydrocarbon feeds. The mechanism of the first C-C bond formation in MTO reaction is poorly understood despite numerous previous studies. The direct observation of acetyl group formation by the reaction between intrazeolitic Brønsted methyl groups and CO by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is reported. It was found that only under high CO pressure could the acetyl group accumulate to substantial amount for spectroscopic observation; at low CO pressure, other competing reactions would either consume the active Brønsted methyl groups or react with the acetyl groups. Such direct observation further confirms the recent theoretical simulation results. We also postulate that this reaction may be one of the possible pathways for the formation of the first carbon-carbon species in the methanol to olefins process. © 2010 American Chemical Society.