Separation Of Sec-Butyl Acetate-Sec-Butyl Alcohol Azeotrope By Extractive Distillation With Mixed Solvents

In the production of sec-butyl alcohol(SBA)by trans-esterification of secbutyl acetate(SBAC)and alcohols,SBAC and SBA form an azeotrope,which is difficult to be separated by conventional distillation.Extractive distillation is an effective process for separating the azeotrope.In the continuous extractive distillation process,the charge of raw materials and extractive solvents and the draw of products are carried out continuously.And the product quality is more stable.Thus,it is suitable for large-scale production.In this work,four solvents: Acetamide,N,N-dimethyl acetamide(DMAC)-dimethyl sulfoxide(DMSO),N,N-dimethyl formamide(DMF)-Acetamide and DMAC-Acetamide were chosen as the extractive solvents for separating the azeotrope of SBAC-SBA by extractive distillation.Isobaric vapor-liquid equilibrium(VLE)data for the systems of SBAC-SBA-solvents were measured at 101.3 k Pa.And the experimental VLE data of the binary systems were correlated with Wilson,NRTL and UNIQUAC models.The ternary and quaternary VLE data predicted by the binary interaction parameters agreed well with the experimental data.And the NRTL model performed better than Wilson and UNIQUAC models.The four solvents were compared at the same mass ratio using the NRTL model.The mixed solvents DMAC-acetamide were selected as an appropriate extractive solvent by taking melt point,bubble point and solubility into account.The conventional continuous extractive distillation with DMAC-Acetamide as solvents to separate the SBAC-SBA azeotrope was simulated by Aspen Plus 8.4software.The effects of the structural and operating parameters of the extractive distillation column and solvent recovery column on the purity of products and the heat duty of the reboilers were investigated.Under the optimal operating conditions,the mass fractions of SBAC and SBA were 0.995 and 0.999,respectively.Based on the investigation of the process of conventional continuous extractive distillation,the simulation of separation of the SBAC-SBA azeotrope in a dividing wall extractive distillation column was carried out.Compared with the conventional extractive distillation process,the extractive distillation process in a dividing wall column saves 10% of the heat duty and reduces the use of a reboiler.