One-pot synthesis of dimethyl carbonate and glycols from supercritical CO2, ethylene oxide or propylene oxide, and methanol

Direct syntheses of dimethyl carbonate (DMC) and glycols (GCs) front supercritical (SC) CO2, epoxides (propylene oxide or ethylene oxide), and methanol were carried out using different solid catalysts prepared in this work. The effects of various conditions, such as reaction temperature. pressure, reaction time, molar ratio of the reactants, and the properties of the supports of the catalysts, on the conversion and yields were investigated. KI supported on ZnO (KI/ZnO) and KI/ZnO with K2CO3 (K2CO3-KI/ZnO) were very active and selective for the reaction after calcinations. At 423 K, all epoxides were reacted in 4 h; the yields of DMC and GC exceeded 57% when ethylene oxide was used, and the amount of the by-products was very small (0.2%). The K2CO3-KI/ZnO could be reused four times, and the yield and selectivity remained unchanged. No leaching of the active catalyst components was detectable at the experimental conditions, probably because the reaction was conducted in homogenous supercritical conditions, where non-corrosive CO2 was the main component in the reaction mixture. A mechanism of the reaction was proposed on the basis of the experimental results. This route may be an effective way to produce DMC and glycols in large-scale because it is simple, the raw materials are cheap, and the amount of by-products is very small. (C) 2003 Elsevier B.V. All rights reserved.