Extractive Distillation Of Isobutyl Alcohol And Isobutyl Acetate Using N,N-dimethyl Acetamide As Solvent

Isobutyl acetate forms a minimum-boiling azeotrope with isobutyl alcohol(isobutyl alcohol 0.884,mole fraction)at 101.3 kPa,so it cannot be separated by conventional distillation.Extractive distillation is a good choice to separate the azeotrope.N,N-dimethyl formamide(DMF),1-hexanol,butyl propionate(BUP)and dimethyl sulfoxide(DMSO)have been chosen as the solvents to separate the azeotropic system in the open literatures,but the selectivity of the solvents was relatively low.N,N-dimethyl acetamide(DMAC)was chosen as a more effective solvent to separate isobutyl alcohol-isobutyl acetate azeotropic system.The isobaric Vapor-Liquid Equilibrium(VLE)data at 101.3 kPa were measured for the binary systems isobutyl alcohol + DMAC,isobutyl acetate + DMAC and the ternary system isobutyl alcohol + isobutyl acetate + DMAC.The NRTL,UNIQUAC and Wilson activity coefficient models were used to correlate the binary VLE data in order to obtain the binary interaction parameters which were used to predict ternary VLE data.The predicted results agreed well with the experimental data.The residual curve map of isobutyl alcohol-isobutyl acetate-DMAC system is plotted by Aspen Plus.A conventional extractive distillation process containing an extractive distillation column and a solvent recovery column was established.Based on the sensitivity analysis of the two columns,the optimal feed position,number of stage,and reflux ratio etc.were determined.Under optimal operating conditions,the molar purity of isobutyl alcohol and isobutyl acetate both reached 0.995.On the basis of conventional two-column extractive distillation,the simulation of extractive distillation in a dividing wall column was carried out.After the sensitivity analysis of the dividing wall column,the purity of isobutyl acetate and isobuty alcohol reached the same purity as the conventional extractive distillation—0.995(mole fraction).The heat duty of the dividing wall column was reduced by 17.18% comparing to the conventional extractive distillation column.