文摘
Cycloaddition of an oxirane group of 2-methyloxirane or 2,2-dimethyloxirane with carbon dioxidewas carried out in both supercritical homogeneous and vapor-liquid coexisting regions to producea cyclic carbonate compound of 4-methyl-1,3-dioxolan-2-one or 4,4-dimethyl-1,3-dioxolan-2-one.The yield of the cyclic carbonate exceeded 95%, when the reaction proceeded in the supercriticaluniform condition. On the other hand, the yield was less than 5%, when the reaction occurredin the two-phase region. While almost all kinds of alkali metal halides exhibited the high catalyticactivity in a polar liquid solvent, limited numbers of halides were found to have much activityin supercritical carbon dioxide. This might be due to differences in solvent properties such aspolarity and dissolving power between the supercritical and liquid solvents. The selectiveseparation of cyclic carbonate from the supercritical mixture of reactants and products wasinvestigated by manipulating the temperature and pressure. When decreasing the temperatureand pressure of the effluent from the reactor below the critical temperature and pressure ofcarbon dioxide, a condensate of cyclic carbonate with a purity of more than 99% was obtainedfrom the outlet stream.