Study On The Separation Of Acetonitrile And N-propanol Azetropic Mixture With Quaternary Ammonium Ionic Liquid As Entrainers

Both acetonitrile and n-propanol are extremely important organic chemical raw materials,which are widely used in industrial production.The azeotrope formed by acetonitrile and n-propanol is a typical binary azeotrope system,and ordinary methods cannot separate the azeotrope of acetonitrile and n-propanol.Recently,as a class of green solvents,ionic liquids have special properties such as negligible saturated vapor pressure,recyclability,and strong designability.They are expected to replace traditional organic solvents as new extractants used in extractive distillation processes.Therefore,this paper chooses ionic liquid as the extractant for separating acetonitrile n-propanol azeotrope system to study the effect of ionic liquid on the phase equilibrium of acetonitrile-n-propanol system.In this paper,the COSMO-thermX computer software is first used to explore the effect of different ionic liquids on the separation of azeotrope acetonitrile-n-propanol.Select 528kinds of ionic liquids composed of 24 kinds of anions and 24 kinds of cations,calculate the selectivity of different ionic liquids,select ionic liquids with higher selectivity through selective analysis,and integrate factors such as economic cost and property comparison of synthetic methods,Screened out methyl trioctyl ammonium acetate([N_8,8,8,1][Ac]),methyl trioctyl ammonium chloride([N_8,8,8,1][Cl])and methyl Trioctylammonium bromide([N_8,8,8,1][Br])is used as an extracting agent for the separation of the acetonitrile-n-propanol azeotrope system.At 101.3k Pa,measure the binary system of acetonitrile+n-propanol and the ternary system containing ionic liquid(acetonitrile+n-propanol+[N_8,8,8,1][Ac]/[N_8,8,8,1][Cl]/[N_8,8,8,1][Br])vapor-liquid equilibrium data.The results show that the addition of the three ionic liquids can increase the relative volatility of acetonitrile relative to n-propanol,and play a role in breaking the azeotropy of the system,and the greater the concentration of the ionic liquid,the better the destruction effect on the azeotrope;The NRTL activity coefficient model performs regression fitting on the experimental data,and the deviation between the fitted value and the experimental value is close to 1%,indicating that the NRTL model is suitable for the acetonitrile-n-propanol ternary system containing ionic liquid;the NRTL model is used to predict three ionic liquids[N_8,8,8,1][Ac],[N_8,8,8,1][Cl]and[N_8,8,8,1][Br]the minimum mole fractions required to break the azeotropic system are respectively 0.015,0.024,0.025,therefore,[N8,8,8,1][Ac]is a better extractant for separating acetonitrile-n-propanol azeotrope.UsingBased on Aspen Plus process simulation software,the acetonitrile-n-propanol-[N_8,8,8,1][Ac]system was used to simulate the two-column continuous extractive distillation process,and the sensitivity analysis tool was used to show that the product fraction was higher than99.9%.Under the premise,the effect of changes in process parameters such as the amount of extractant,the number of theoretical plates of the distillation column,the reflux ratio and the feed position of the raw materials on the separation effect of the acetonitrile-n-propanol system and the energy consumption of the equipment are studied.The optimization results show that when the process conditions are as follows:the solvent ratio is 0.2,the total number of theoretical plates is 25,the reflux ratio is 1.1,and the ionic liquid and raw material feed positions are the second and eighth plates respectively,the top product The mass fraction of acetonitrile can reach 99.9%,which meets the separation requirements.It shows that the separation of acetonitrile-n-propanol azeotrope system with[N_8,8,8,1][Ac]as the solvent is industrially feasible.