Establishment Of Structure-property Models For Relative Volatility And It’s Validation In Extractive Distillation

In this paper,the study of extractive distillation was carried out from four aspects,including thermodynamics analysis,solvent selection,optimization and improvement of steady state and dynamic control.Quantitative structure-property relationship（QSPR）was proposed to study the relationship between relative volatility and molecular structure of solvent in separating binary azeotropic mixture.The aim of the study was to investigate the nature effect on relative volatility in extractive distillation.The molecular structure of solvent for isopropanol-water and t-butanol-water systems was established with Discovery Studio and Material Studio software and the structure was optimized in the force field based on the minimal molecular energy.617 descriptors of one-dimensional,two-dimensional,and three-dimensional were calculated.The relative volatility QSPR model was set up for two systems by genetic algorithm and GFA modeling.The two models were validated with inter and outer verification.The verification parameters R²for isopropanol-water was 0.8,R²_CV was0857,R²_adj was 0.7,the model was stable after the model verification.The verification parameters R²for isopropanol-water was 0.983,R²_CV was 0.976,R²_adjdj was 0.937.The calculated parameter values are within the standard range and the model was stable.The QSPR model for THF–ACT system was set up based on the structure-activity theory.The new solvent n-octane was selected out based on the model and relative volatility for n-octane and old solvent butyl ether.The ternary residue curve map for n-octane/THF/ACT was set up using Aspen Plus and the feasibility of extractive distillation was analyzed.The two separation flowsheets for different solvents were built and were optimized with optimization tool of Visual Basic based on sequential iterative method taking the minimal total annual cost as objective function.Based on the optimal steady-state process design,the optimal control strategy of extractive distillation dynamics was studied.The control strategy was evaluated by ISE.By comparing the relative volatility,steady-state economy,and temperature controllability,the stability and predictability of the QSPR model can be verified by industrial separation.