Synthesis of Dimethyl Carbonate from Methyl Alcohol and Supercritical Carbon Dioxide in the Presence of Ionic Liquids

摘要

Dimethyl carbonate (DMC) that is a raw material for polycarbonate and an intermediate compound for various organic products was synthesized from methanol at 343.15～423.15 K and 5～35 MPa in the presence of ionic liquid and supercritical carbon dioxide. This new process can make us avoid the current toxic and dangerous DMC synthesis process. Methanol or Compound A and carbon dioxide were used as reactants. Potassium carbonate was used as the catalyst and two ionic liquids were tested in the reaction: 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF{sub}6]) and 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF{sub}4]). The yield of DMC was very low (less than 3 mol%) when methanol was used. As either the amount of ionic liquid or pressure was increased, the yield of DMC increased. The yield of DMC has been increased slowly at low catalyst concentrations but rapidly above 0.6 mmol (0.3 mol% CO{sub}2). Methyl iodide promoted the reaction. When compound A was used, however, the yield of DMC increased up to 5 times as high as in the methanol route.