Measurement And Process Simulation Of Acetonitrile-Methanol Azeotrope Separation With Ionic Liquid As Extractant

Acetonitrile and methanol mixture will be produced in some chemical production processes,such as acetonitrile and methanol as raw materials for the synthesis of acetamidine hydrochloride.Methanol and acetonitrile form azeotropy at normal pressure.The study of extractive distillation separation technology using green solvent ionic liquid as a separating agent has important economic value for strengthening separation azeotrope.In this paper,four ionic liquids,1-butyl-3-methylimidazolium chloride [BMIM][Cl],1-butyl-3-methylimidazolium bromide [BMIM][Br],1-butyl-3-methylimidazolium diethylphosphate [BMIM][DEP],1-butyl-3-methylimidazolium acetate [BMIM][OAc],were firstly screened as extractants to separate the acetonitrile-methanol system,and three kinds of ionic liquids were prepared.The analytical methods of nuclear magnetic resonance spectroscopy,ion chromatography and water content ensure that the synthesized ionic liquid meets the requirements of the later phase equilibrium experiment.Secondly,under normal pressure,the equal pressure vapor-liquid equilibrium data of the binary system and the ternary system containing ionic liquid were determined by the modified Othmer still method,and the experimental data were fitted using the NRTL thermodynamic model,and the relevant parameters of the model were obtained by regression.The effects of different ionic liquids on the phase equilibrium behavior of the system were compared and analyzed.Finally,the Aspen Plus software was used to simulate and optimize the extractive distillation process of ionic liquid separation acetonitrile-methanol azeotrope system,in order to support the theory in practical industrial applications.Experimental conclusions: The four ionic liquids can significantly improve the relative volatility of acetonitrile to methanol,and can effectively break the azeotrope system;The separation ability of four ionic liquids is: [BMIM][OAc] > [BMIM][DEP] >[BMIM][Cl]> [BMIM][Br].The minimum mole fractions for breaking the azeotropy are 0.183,0.138,0.122,0.116,respectively.The data measured by the NRTL model equation correlation experiment,the fitted value and the experimental value are in good agreement,indicating that the NRTL model is suitable for the data association of the system.Using Aspen plus software to simulate the process flow,the optimal operating parameters are: theoretical plate number 20,raw material feeding position 8,reflux ratio 1.1,top column recovery amount 45kmol/h,extractant feed amount 45 kmol /h(solvent ratio 2.47).Comparing with organic solvent,sulfolane,the results show that ionic liquids are superior to organic solvents in terms of energy consumption and energy consumption.