Molecular Design Of Solvents For Extractive Distillation

A computer-aided molecular design (CAMD) approach of solvents for extractive distillation is established for the systems of close boiling compounds or azeotropes. Aromatic groups which have a harmful effect on environment are got rid of from Mod.UNIFAC groups. On the basis of group contribution method, chain hydrocarbons and ring compounds are designed with adaptive multiple objectives genetic algorithm (GA). Firstly according the requirements of the special problem, the lasted Mod.UNIFAC groups are preselected. And then resolve the problem how to combine the groups into the molecules with adaptive multiple objectives genetic algorithm. The method overcomes the combinatorial explosion in molecular design.The molecular design program based on adaptive multiple objectives GA is written with Matlab using its strong numerical calculation function. The multiple screening indexes of solvents for extractive distillation include relative volatility, molecular weight, freezing point, boiling point and solvent power. Slovents of extractive distillation for Methanol- acetone (distillate acetone), methanol-methyl acetate (distillate methyl acetate) and benzene-cyclohexane (distillate cyclohexane) systems are designed applying this method.A apparatus for vapor-liquid equilibrium is set up with the gas chromatography to study of solvents for extractive distillation. The vapor-liquid equilibrium of acetone-methanol and methanol-methyl acetate systems are measured with the solvents of 1,4-butanediol, DMFO and glycol, DMFO by the device respectively. The results indicate that the molecular design method is reasonable and the program is reliable and practical.