Separation Of Isobutyl Alcohol–isobutyl Acetate Azeotrope By Extractive Distillation

Isobutyl acetate is an important industrial raw material,which is mainly used as a solvent for nitrocellulose and paint,as well as chemical reagents and modulation spices.Isobutyl acetate is produced by esterification of acetic acid with isobutyl alcohol catalyzed by acidic catalyst.However,isobutyl alcohol and isobutyl acetate can form a minimum boiling point azeotrope(isobutyl alcohol 0.875,mole fraction)at 101.3 kPa,which causes difficulty for the subsequent purification of isobutyl acetate with conventional distillation.In this paper,DMSO was selected as entrainer to separate isobutyl alcohol + isobutyl acetate azeotrope.A study on the separation of isobutyl acetate + isobutyl acetate by continuous extractive distillation was carried out.In this paper,the isobaric VLE data for isobutyl alcohol + DMSO,isobutyl acetate + DMSO and isobutyl alcohol + isobutyl acetate + DMSO were measured at 101.3kPa.The relative volatility of isobutyl acetate to isobutyl alcohol can be greatly increased by DMSO and the azeotropic point of isobutyl acetate and isobutyl alcohol will disappear if enough DMSO was added.All VLE data passed the thermodynamic consistency tests.The VLE data of binary systems were correlated with NRTL,UNIQUAC and Wilson models.The binary and ternary VLE were predicted with the corresponding correlated binary interaction parameters,and the predicted results agreed well with the experimental data.The extractive distillation with DMSO as entrainer to separate isobutyl alcohol and isobutyl acetate was simulated by Aspen Plus with the analysis of residual curve.The effects of solvent feed location,solvent ratio,solvent temperature,reflux ratio,feed location,number of stage on the concentration of isobutyl acetate in the distillate and heat duty of reboiler of the extractive distillation column have been investigated by the sensitivity analysis.The effects of reflux ratio,feed location,feed temperature and number of stage on the purity of isobutyl alcohol in distillation and heat duty of reboiler of the solvent recovery column were also investigated.The suitable structural and operational parameters for the extractive distillation column and solvent recovery column were obtained.TAC is utilized as an objective function to optimize the extractive distillation process.The fixed reflux ratio and fixed R/F ratio structure were put forward for the optimal extractive distillation process and assessed by feed composition and feed flow rate disturbances.The results indicate that the fixed R/F ratio structure could effectively handle the disturbances.The control effect of fixed R/F ratio structure is better than that of the fixed reflux ratio.