| Acetonitrile is a widely used organic solvent, and the separation of acetonitrile-water azeotropes is very important. The effects of ionic liquids on azeotropic system of acetonitrile-water were investigated, and the extractive distillation process with ionic liquid as solvent was also studied.The vapor-liquid equilibria of acetonitrile-water-ionic liquids were predicted using the COSMO-SAC Model. The vapor-liquid equilibria were measured in an modified Othmer equilibrium still.The vapor-liquid equilibrium experimental results show that: if the mole fraction of ionic liquid in the acetonitrile-water-ionic liquid mixture is 0.2, the ionic liquid 1-ethyl-3-methyl imidazolium nitrate([Emim][NO3]) and 1-ethyl-3-methyl imidazo- lium dicyanamide ([Emim][N(CN)2]) can eliminate the azeotropic point of the acetonitrile-water mixture, however the 1-ethyl-3-methyl imidazolium tetrafloro- borate([Emim][BF4]), 1-butyl-3-methyl imidazolium tetrafloroborate([Bmim][BF4]) and 1-ethyl-3-methyl imidazolium trifluoromethanesulphonate([Emim][CF3SO3]或[Emim][OTf]) can only increase the acetonitrile's mole fraction at the azeotropic point but can not remove the azeotropic point completely. The vapor-liquid equilibria of acetonitrile-water-[Emim][BF4], acetonitrile-water-[Bmim][BF4] and acetonitrile- water-[Emim][N(CN)2] were measured when the mole fraction of ionic liquid in the mixture is 0.4. The relative volatility of acetonitrile to water reduced at low acetonitrile concentration, and increased at its high concentration as the mole fraction of [Emim][BF4], [Bmim][BF4] and [Emim][N(CN)2] increased. The NRTL parameters were fitted through the vapor-liquid equilibria.The extractive distillation process of acetonitrile-water with ionic liquid as solvent was simulated by the software ChemCAD. The effects of feed location, the solvent charge location, the solvent temperature, reflux ratio and solvent ratio to the extractive distillation process were investigated by the simulation results.
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