Separation Of Methyl Acetate-Methanol System By Extractive Distillation For Screening Ionic Liquids

With economic transformation and supply-side structural adjustment,environmental protection and ecology have become the mainstream of manufacturing.Methyl acetate and methanol are common chemical raw materials,usually in the form of azeotropes.Ionic liquids have received extensive attention as green solvents.The research of the use of ionic liquids instead of traditional organic solvents for extractive distillation of methyl acetate-methanol azeotropes is hot.An ionic liquid extractant for extractive distillation separation of methyl acetate-methanol azeotrope was selected from 676 ionic liquids composed of 26 anions and26 cations by COSMO-ThermalX software based on COSMO-RS theory.Selective results revealed that selective 1-benzyl-3-methylimidazoliumacetic acid（[BzMIM][Ac]）>1-octyl-3-methylimidazoliumacetic acid（[OMIM][Ac]）>chlorination1-octyltrimethylimidazole（[OMIM][Cl]）,while butyltrimethylacetate([N₄₁₁₁][Ac])has the highest selectivity.Considering the cost and systemicity of the whole system study,1-benzyl-3-methylimidazoliumacetic acid（[BzMIM][Ac]）,1-octyl-3-methylimidazoliumacetic acid（[OMIM][Ac]was chosen.）,1-octyltrimethylimidazolium chloride（[OMIM][Cl]）was subjected to phase equilibrium experiments,and phase equilibrium data were predicted for butyltrimethylacetate ammonia([N₄₁₁₁][Ac]).The experimentally determined three sets of ternary data were correlated with a set of ternary data predicted by the software using the NRTL model,and the obtained ternary data was fitted.[N₄₁₁₁][Ac]、[BzMIM][Ac]、[OMIM][Ac]、[OMIM][Cl]were estimated by a new fragment contribution-correspondence（FC-CS）method.The critical properties of the four ionic liquids of 1-octyltrimethylimidazole and the liquid vapor pressure of four ionic liquids such as butyltrimethylacetate were predicted using the Riedel equation in combination with the estimated critical properties.These parameters were substituted into the Aspen Plus software to simulate the extractive distillation process in which the methyl acetate-methanol system was separated by four ionic liquid extractants,and the best design parameters were verified based on the economic assessment of total annual cost（TAC）.The results show that[BzMIM][AC]is the most suitable extractant for the separation of methyl acetate and methanol azeotrope systems.