Ionic liquid effects on mass transfer efficiency in extractive distillation of water¿ethanol mixtures

Abstract

tThe relatively high viscosities of ionic liquids could reduce the mass transfer efficiency of the extractivedistillation process. The rate-based model was adopted to analyze this phenomenon since it predicted theperformance of an extractive distillation pilot plant using ionic liquids as solvent. For the water¿ethanolseparation, three ionic liquids: 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazoliumacetate and 1-ethyl-3-methylimidazolium dicyanamide and the organic solvent ethylene glycol wereused for the analysis. Simulations were conducted for sieve trays and Mellapak®250Y. The results indi-cate that relatively high viscosities affect the mass transfer efficiency. However, the improvements inrelative volatilities obtained from the ionic liquids help to overcome this effect. However, with high sol-vent viscosities (>65 mPa s at T = 353.15 K) it was not possible to overcome the reductions. Additionally, athigher distillate rates high relative volatilities yielded negative effects on mass transfer efficiency becauseof a decrease in vapor velocity.