Separation Of Water-acetonitrile Binary Azeotrope By Extraction Distillation

Acetonitrile is a kind of important chemical raw materials,its dehydration plays a significant role in the chemical production.The study of the vapor-liquid equilibrium of water + acetonitrile has an important theoretical guidance for the design and development of separating water + acetonitrile.This paper,from the selection of excellent solvent as the starting point,carried out the research about using extraction distillation to separate water + acetonitrile.This paper presents vapor-liquid equilibrium(VLE)measurement for the ternary system of water(1)+ acetonitrile(2)+ ethylene glycol(3),the quaternary system of Water(1)+ acetonitrile(2)+ ethylene glycol(3)+ glycerol(4)and water(1)+ acetonitrile(2)+ ethylene glycol(3)+ choline chloride(4)at p = 101.3 kPa,from which the activity coefficient and relative volatility of the volatile components were obtained.The NRTL model was used to correlate the vapor-liquid equilibrium data of each system,which showed good agreement with experimental data.For water(1)+ acetonitrile(2)+ ethylene glycol(3)system,the average absolute deviation of equilibrium temperature and acetonitrile vapor-phase mole fraction are ?T = 0.15 K,?y = 0.0025,respectively;for water(1)+ acetonitrile(2)+ ethylene glycol(3)+ glycerol(4)system,?T = 0.25 K,?y = 0.0017,for water(1)+ acetonitrile(2)+ ethylene glycol(3)+ choline chloride(4)system,?T = 0.22 K,?y = 0.0014.The reliability of the NRTL model was further confirmed by comparing the experimental results of water(1)+ acetonitrile(2)+ ethylene glycol(3)ternary system with the literature value.Compared the effects of three types extraction agents,ethylene glycol,ethylene glycol + glycerol and ethylene glycol + choline chloride on the separation of water+acetonitrile azeotropic system,the result of research indicated that deep eutectic solvents,ethylene glycol + choline chloride,used in water acetonitrile extraction distillation has a prominent performance.With the addition of choline chloride into ethylene glycol,the separation of water+acetonitrile could be strengthen,which can also significantly improve the relative volatility of acetonitrile to water.The correlation showed that azeotrope of water + acetonitrile can be removed at a glycol mole fraction of 0.277,for Ethylene glycol + glycerol EG:G(1:6)= 0.185,EG:G(1:4)= 0.190,EG:G(1:2)= 0.201,EG:G(1:1)= 0.217;for ethylene glycol + choline chloride sys-tem EG:ChCl(4:3)= 0.091,EG:ChCl(2:1)= 0.120,EG:ChCl(4:1)= 0.176,EG: ChCl(8:1)= 0.220.Based on the NRTL activity coefficient model,using Aspen plus chemical simulation software,the extraction and distillation of water + acetonitrile were simulated by using ethylene glycol,ethylene glycol + glycerol(1: 2),ethylene glycol + choline chloride(2: 1)as extraction agent respectively.Optimized the theoretical plate number,reflux ratio,flow rate of extractant,solvent ratio S / F,extraction temperature of extractant respectively.The results showed that when the same separation effect was achieved,ethylene glycol + choline,whose purity is required lower than other extractants,at the same time,less dosage and less reflux ratio in the tower,which is a potentially efficient extractant for the dehydrate of acetonitrile.