间歇萃取精馏分离乙腈-水体系

Separation of Acetonitrile-Water Mixture by Batch Extractive Distillation

选择乙二醇为分离乙腈-水体系的萃取剂,在压力0.101 MPa条件下,测定了乙腈-乙二醇物系的汽液平衡数据。采用Wilson模型对试验数据进行关联,得到Wilson模型参数,α1,3=5 683.6,α3,1=576.4（下标1代表乙腈,3代表乙二醇）,关联的计算结果和试验结果的最大偏差为0.015 7。测定了乙二醇存在下乙腈-水物系的汽液平衡数据,试验结果表明乙二醇做萃取剂能够消除乙腈-水物系的共沸点。进行了乙腈-水物系的间歇萃取精馏试验,回流比为2.0,萃取剂流量与回流量之比（溶剂比）为4.1,塔顶产品中乙腈的摩尔分数x达到0.988,乙腈的回收率为75%。应用Chemcad软件考察溶剂比和回流比对产品纯度及塔顶产品量的影响,确定适宜溶剂比为3.0,其回流比值在0.5-2.0之间。

Ethylene glycol was selected as solvent for separating mixture of acetonitrile-water. Vapor-liquid equilibrium of acetonitrile-ethylene glycol binary system was measured under 0. 101 MPa. Experimental data were correlated by Wilson equation, and obtained the parameters for Wilson model, α1,3 = 1 359.7, α3,1 = 137.9, maximum deviation of correlation result to experimental data is 0.015 7. Vapor-liquid equilibrium of acetonitrile-water with ethylene glycol was measured. The results show that the azeotropic point of acetonitrile- water can be eliminated by ethylene glycol. Separation of acetonitrile-water mixture was carried out by batch extractive distillation, under conditions of reflux ratio 2 ： 1, solvent ratio 4.1 ： 1, mole fraction of aeetonitrile in overhead can reach 0. 998 and the recovery of acetonitrile is 75 %. The effects of reflux ratio and solvent ratio on the purity of product and the amount of product in overhead were also investigated for batch extractive distillation by Chemead and obtained that suitable solvent ratio was 3 ： 1, reflux ratio ranged from 0.5--2.0.