Study On Effects Of Ionic Liquids On The Phase Equilibrium Behavior Of Ethyl Propionate-n-propanol And Separation Process Development

To address the azeotropic phenomenon of ethyl propionate and n-propanol,which is common in the production of alcoholic substances.In this study,two ionic liquids（ILs）[Emim][OAC]and[Mmim][DMP]were screened,and ethylene glycol（EG）was used as a comparison to investigate the effect of ILs as entrainer on the phase equilibrium behavior of this azeotrope through phase equilibrium experiments.Binary VLE data of the ethyl propionate-n-propanol mixture were measured,and these data passed the thermodynamic consistency test and were remarkably consistent with the published VLE data,demonstrating the precision of the experimental data and thus the reliability of the experimental apparatus.The ternary VLE data of ethyl propionate-n-propanol-[Emim][OAC],ethyl propionate-n-propanol-[Mmim][DMP]and ethyl propionate-n-propanol-EG were measured and fitted with the NRTL model to obtain the binary interaction parameters between the components.The experimental results indicated that all three entrainers shifted the azeotropic point toward the high concentration of ethyl propionate,which increased the relative volatility of ethyl propionate to n-propanol,but the effect of ILs is better than that of EG.Based on the VLE experiments,the pure component parameters of[Emim][OAC]and[Mmim][DMP]were defined into the Aspen Plus component module,and extractive distillation schemes with ILs as entrainers was developed,and the optimized process variables were gotten employing sequential iterative method.A comprehensive process evaluation system with economic,energy,environmental and efficiency indicators was established.The evaluation results for extractive distillation showed that compared with the[Emim][OAC]extractive distillation process,the[Mmim][DMP]extractive distillation process reduced TAC,TCC and TOC by 16.78%,27.91%and11.54%,respectively,at the same time,the energy consumption and total CO₂emissions are decreased by 12.10%and 12.37%,while thermodynamic efficiency improved by 12.45%.Using the phase diagram as a theoretical guide,the pressure swing distillation and azeotropic distillation schemes were developed,optimized using particle swarm optimization.HIPSD process and HIAD process were developed using heat integration technology such as feed preheating,tower-top steam reuse and heat pumps.The comprehensive evaluation showed that the HIPSD process was superior to the HIAD process in terms of economy,energy consumption,environment and efficiency.Further comparing the two ILs extractive distillation processes with the HIPSD process,it was found that the[Mmim][DMP]extractive distillation process was more advantageous.The[Mmim][DMP]extractive distillation process reduced TAC,TCC and TOC by54.58%,71.37%and 41.39%,respectively,at the same time,the energy consumption and total CO₂ emissions are decreased by 55.40%and 54.91%,while thermodynamic efficiency improved from 5.75%to 11.89%,comparing with HIPSD process.In conclusion,for the separation of ethyl propionate-n-propanol azeotropic system,the[Mmim][DMP]extractive distillation process has significant advantages.