Extractive Distillation Of Acetic Acid-N,N-dimethylacetamide With Ionic Liquid As Entrainer

N,N-dimethylacetamide is widely used as solvent in chemical industry,but it can form maximum boiling point azeotrope with acetic acid,so the azeotropic mixture cannot be separated by regular distillation.The extractive distillation process for the separation of acetic acid – N,N-dimethylacetamide azeotrope using ionic liquid as entrainer was studied in this paper.The COSMO-SAC model was utilized to screen the effective ionic liquid entrainer for the extractive distillation process.The ionic liquid 1-butyl-3-methylimidazolium bis[?trifluoromethyl?sulfonyl]imide?[BMIM][Tf₂N]?was selected as entrainer to separate the azeotrope of acetic acid and N,N-dimethylacetamide.The vapor-liquid equilibrium data of the ternary system of acetic acid + N,N-dimethylacetamide + [BMIM][Tf₂N] were measured at 7.0 kPa and 12.0 kPa and the results show that the azeotrope of acetic acid + N,N-dimethylacetamide can be broken by [BMIM][Tf₂N].The equilibrium data were correlated with NRTL-HOC model and the binary interaction parameters of acetic acid-[BMIM][Tf₂N],N,N-dimethylacetamide-[BMIM][Tf₂N] were obtained,the correction results agree well with the experimental results.The extractive distillation with [BMIM][Tf₂N] as entrainer to separate acetic acid and N,N-dimethylacetamide was simulated by Aspen Plus.The effects of feed stage,solvent feed stage,solvent temperature,reflux ratio,solvent ratio on the concentration of acetic acid in the distillate and heat reboiler of the extractive distillation column have been investigated by the sensitivity analysis.The feed location and reflux ratio on the purity of N,N-dimethylacetamide and heat duty of the solvent recovery column were also investigated.The suitable operational and structural parameters for the extractive distillation column and solvent recovery column were obtained.