Investigation of the oxidative carbonylation of methanol to dimethyl carbonate over copper zeolite catalysts

The development of a micro-kinetic model for the oxidative carbonylation of methanol to DMC over copper zeolite catalysts was done to gain understanding and insight on the interaction of the catalyst with the species that form DMC. The kinetic data and IR spectroscopy agree well with a reaction mechanism that posits slow insertion of carbon monoxide into the surface methoxide species. The fitted values of the model parameters indicate that the most abundant surface species on the catalyst is methoxide at low water pressures.; The adsorption of CO on the catalyst is an important consideration. Cu +X is a better catalyst than Cu+ZSM-5 for DMC production. The weaker adsorption of CO onto Cu+X compared to Cu +ZSM-5 is advantageous for DMC production because adsorbed CO blocks sites for methoxide formation but does not participate in DMC formation.; Decomposition of DMC over Cu+Y limits the operating temperature and yield of the methanol carbonylation reaction. The active sites for DMC decomposition are the residual Bronsted sites present due to incomplete exchange. Exchanging the residual acid sites of a Cu+Y catalyst with Li+ ions lowers the residual acidity of the catalyst, decreasing the rate of decomposition. The lower rate of decomposition resulted in a higher observed activity of DMC production over Cu+Li +Y compared to Cu+Y at higher temperatures.; Adding the WGS catalyst to the reactor with Cu+Y catalyst increased the rate of DMC production over the Cu+Y catalyst. The amount of water in the reactor effluent was less when the WGS catalyst was used, due to the WGS catalyst removing water faster than it was produced by the oxidative carbonylation reaction.; The activity of the copper zeolite catalyst decreases for a period of around 15 days, after which the activity remains relatively constant. During deactivation, there is a migration of copper away from the catalyst surface and some of the cuprous ions are oxidized to cupric ions. No bulk formation of copper metal or copper oxide was detected.