Synthesis of dimethyl carbonate and glycols from carbon dioxide, epoxides,and methanol using heterogeneous basic metal oxide catalysts with high activity and selectivity

This paper gives a comprehensive report on a two-step synthesis of dimethyl carbonate (DMC) from epoxides, carbon dioxide and methanol using various b asic metal oxide catalysts. The first step is the reaction of ethylene oxid e or propylene oxide with CO2 to form the corresponding cyclic carbonates, and the second step is the transesterification reaction of the cyclic carbo nates with methanol to DMC and glycols. Among the catalysts examined, MgO i s the most active and selective for both these reactions. Other alcohols ca n be used for the second step, but the activity decreases as the carbon num ber of the alcohol increases. Although a one-pot synthesis of DMC, i.e. the sequential reaction of the epoxide, CO2 and methanol, is also possible wit h MgO, the selectivity is low because of the alcoholysis of the epoxide. In contrast with the reactions of ethylene oxide and propylene oxide, when st yrene oxide is used for the first reaction and for the one-pot synthesis, m andelic acid is produced. Basic properties of the metal oxide catalysts wer e measured by temperature programmed desorption of CO2. The relationship be tween the catalytic performance and the basic property is discussed. (C) 20 01 Elsevier Science B.V. All rights reserved.