Computer-aided Design And Process Evaluation Of Ionic Liquids For Alkanes-cycloalkanes Extractive Distillation

There are few kinds of special environmental protection solvent oil in our country,extraction distillation is often used in preparation of solvent oil.The conventional entrainers have the problems of low selectivity,large consumption and easy volatilization.Ionic liquids(ILs)are highly attractive entrainers for separating close-boiling or azeotropic mixtures in extractive distillation processes.However,it is impossible to screen a suitable IL from a large number ILs for a specific mixture by experiments,so it is particularly important to develop a computer-aided design method based on theoretical prediction.In this work,the representive alkanes-cycloalkanes mixtures of solvent oil(i.e.n-hexane-methylcyclopentane and n-heptane-methylcyclohexane)were studied,a computer-aided molecular design method(CAMD)combined with Aspen Plus process simulation software were used to determine the optimal separation performance of IL entrainers.First,a lot of experimental data of methylcyclopentane and methylcyclohexane in different ILs of infinite dilution activity coefficient,as well as the ternary vapor-liquid equilibria experimental data of relevant systems were collected from literature to validate the reliability of the employed UNIFAC-IL model.Then,combining the UNIFAC-IL model and two group contribution models of IL physical properties,taking N-methyl pyrrolidone as the benchmark,the activity coefficient,distribution coefficient and selectivity in infinite dilution were used as thermodynamic indicators to form ILs design problems.The top IL candidates pre-identified for the two systems were further introduced into Aspen Plus for process simulation and evaluation.By comparing their process performances with the benchmark solvent N-methyl pyrrolidone,1-nonyl-imidazolium thiocyanate([C9Im][SCN])was consequently identified as the optimal entrainer for the two systems.Finally,through the economic analysis,the feasibility and advantages of the IL process were proved,the similarities and differences of the two systems were illustrated.