Vapor - Liquid Equilibrium Of Dichloronitrobenzene Isomers And Its Distillation Separation Simulation

3,4-Dichloronitrobenzene(3,4-DCNB) and2,3-dichloronitrobenzene(2,3-DCNB) are both important intermediate which are widely used in the synthesis of pharmaceutical and pesticides. When producing3,4-DCNB by nitration of o-dichlorobenzene, the2,3-DCNB always exist in the products. In the process of purifying3,4-DCNB by melt crystallization, a large amount of eutectic form. The difference of boiling point between3,4-DCNB and2,3-DCNB is only2K. It is difficult to separate3,4-DCNB and2,3-DCNB by conventional distillation. In this work, the separation of3,4-DCNB and2,3-DCNB by extractive distillation had been studied.The vapor pressure of pure2,3-DCNB and3,4-DCNB from3.2tol01.32kPa were determined by means of an inclined ebulliometer. The relationship between saturated vapor pressure and boiling temperature is fitted by Antoine equation. The calculation results of the acquired Antoine equation coincide well with experimental data. The inclined ebulliometer was also used to determine the isobaric vapor-liquid equilibrium (VLE) data of the binary system3,4-DCNB(1)+2,3-DCNB(2) at101.3,60and20kPa. Herington method was used to check the thermodynamic consistency of the experimental data. All the data were confirmed to be thermodynamically consistent. The experimental data were correlated by Wilson, NRTL and UNIQUAC models. The prediction results of the three acquired models all coincide well with experimental VLE data.According to the principle of screening solvent for extractive distillation and results of VLE experiment, dibutyl phthalate(DBP) was selected as the solvent for extractive distillation in this work. The isobaric VLE data at10kPa of the ternary system3,4-DCNB(1)+2,3-DCNB(2)+DBP(3) which solvent mass ratio is3:1,2:1and1:1respectively were determined using the inclined ebulliometer. McDermott-Ellis method was used to test the thermodynamic consistency of the experimental VLE data for the ternary system. All experimental points pass the test. The VLE data of ternary system were correlated by the Wilson model. And the corresponding binary interaction parameters were obtained. The prediction results of obtained acquired model agree well with experimental VLE data. Process simulation software, ChemCAD, was used to simulate the extractive distillation process using DBP as solvent. The mole ratio of3,4-DCNB and2,3-DCNB in raw material was0.63:0.37.And temperature of raw material and solvent were both373.15K. The column top pressure was10kPa. Operation parameters such as solvent ratio, reflux ratio, number of stages, solvent feed stage and raw material feed stage were optimized by parameter sensitivity analysis. According to separation requirements, the suitable operation conditions of extractive distillation tower are as follows: solvent ratio is3, reflux ratio is5, number of stage is55, solvent feed location is the fourth stage and raw material location is the fourteenth stage. The corresponding suitable operation conditions of solvent recovery tower are as follows:number of stage is28, raw material feed location is the fifth stage, reflux ratio is7.