甲醇-碳酸二甲酯-离子液体等压汽液平衡数据测定

Isobaric vapor-liquid equilibria for methanol-dimethyl carbonate-ionic liquids ternary systems

在101.32 kPa下,用改进的Othmer釜测定了含离子液体1-乙基-3-甲基咪唑四氟硼酸([EMIM]BF4)的甲醇-碳酸二甲酯的等压汽液平衡数据,和含离子液体1-辛基-3-甲基咪唑四氟硼酸盐([OMIM]BF4)的甲醇-碳酸二甲酯的等压汽液平衡数据。结果表明:加入[EMIM]BF4和[OMIM]BF4,汽液平衡线偏离甲醇-碳酸二甲酯物系的汽液平衡线;离子液体摩尔分数越大,偏离程度越大;[EMIM]BF4与[OMIM]BF4表现出明显盐效应,使甲醇对碳酸二甲酯的相对挥发度发生改变,均消除了甲醇-碳酸二甲酯物系的共沸点。离子液体对甲醇的盐析效应顺序为:[OMIM]BF4>[EMIM]BF4。因此,[EMIM]BF4和[OMIM]BF4可以作为甲醇-碳酸二甲酯物系萃取精馏的溶剂,汽液平衡数据的测定可为分离过程优化设计提供依据。

Isobaric vapor-liquid equilibrium（VLE） data for the methanol-dimethyl carbonate system containing ionic liquids（ILs） have been measured at 101.32 kPa using a modified Othmer still.The ionic liquids employed were 1-ethyl-3-methylimidazolium tetrafluoroborate（BF4） and 1-octyl-3-methylimidazolium tetrafluoroborate（BF4）.The vapor-liquid equilibrium curves of the ionic liquid-containing systems deviate from that of the IL-free system and the deviation increases with increasing amount of IL.The IL shows a salt effect,which gives rise to an increase in the volatility of methanol relative to dimethyl carbonate,and even leads to an elimination of the azeotropic point.The salt effect on methanol decreases in the order BF4 BF4.As a result,it is concluded that BF4 and BF4 can be used as entrainers for the separation of methanol and dimethyl carbonate,and the VLE data obtained here can be used to optimize the process.