Synthesis of dimethyl carbonate from methanol and supercritical carbon dioxide

The synthesis of dimethyl carbonate (DMC) from methanol and supercritical carbon dioxide over various base catalysts has been studied. Compounds of group-I elements (Li, Na and K) were used as base catalysts. The promoter and the dehydrating agent were also used to enhance the yield of DMC. The effects of the catalysts, promoter and dehydrating agent on the yield of DMC were investigated. By-products such as dimethyl ether (DME) and C-1-C-2 hydrocarbons were formed with the DMC as a main product. The yield of DMC with different alkali metal catalysts ranked in the following order: K > Na > Li. The catalysts of the metal-CO3 compounds were more effective than the metal-OH compounds in DMC synthesis. The maximum DMC yield reached up to about 12 mol% in the presence of K2CO3 (catalyst), CH3I (promoter) and 2,2-dimethoxypropane (dehydrating agent) at 130-140 degrees C and 200 bar. The reaction mechanism of DMC synthesis from methanol and supercritical carbon dioxide was proposed.