Separation Of Methyl Acetate And Methanol By Using Ionic Liquids

As a representative azeotropic system involved in the manufacturing process of poly(vinyl alcohol), methyl acetate and methanol is difficult to be separated by using traditional distillation methods. In the industry, the most commonly used method to separate the azeotropic system is extractive distillation and the key is the selection of entertainer. Organic solvents are volatile and have some other disadvantages, so it is urgent to find a new entertainer and then those disadvantages can be avoided. Ionic liquids (ILs) as green solvents came into being because of the outstanding characteristics such as salting-out or salting-in for component, can being easily separated and recycled, etc.Three ILs are synthesized, [AMIM][DAP], namely, 1-alkyl-3-methylimidazolium dialkylphosphate, and the A is CH3, C2H5 and C4H9, respectively. ILs as extracting agent are applied to separation of methyl acetate and methanol. The vapor liquid equilibrium (VLE) data of both binary and ternary system are measured under constant pressure. And the separation effect of three ILs is investigated.The isobaric VLE data of binary system including methyl acetate-methanol, methyl acetate-IL and methanol-IL is measured. It can be inferred that the activity coefficient of methyl acetate is gradually increased by increasing the mole concentration of IL in the binary system, the relationship between the increasing amplitude and three ILs is:[MMIM][DMP]> [EMIM][DEP]> [BMIM][DBP]; but the activity coefficient of methanol is declined, the relationship between the declining amplitude and the three ILs is: [BMIM][DBP]> [EMIM][DEP]> [MMIM][DMP]0The isobaric VLE data of ternary system with adding ILs is measured. It can be inferred that when the mole concentration of ILs in the system is 0.05, the azeotropic point of methyl acetate and methanol has completely disappeared. At this point, in the whole range of the concentration the relative volatility of methyl acetate is greater than 1.The ability of three ILs to separate methyl acetate and methanol azeotropic system is followed:[MMIM][DMP]> [EMIM][DEP]> [BMIM][DBP]。We use e-NRTL thermodynamic model to correlate the VLE data of the binary and ternary systems in this experiment. And the maximum relative deviation of correlation is also worked out, which is 4.483% and 4.801% for the binary and ternary systems, respectively. It indicated that e-NRTL thermodynamic model can be used well in the correlation of the measured data of binary and ternary system.From the experimental results we can come to conclusion that three ILs can be used as extraction agent and applied to the extractive distillation separation of methyl acetate and methanol.