Sequential strategy of experimental design I: Optimization of extractive distillation process of ethanol–water using [bmim][N(CN)2] as entrainer

Abstract

Nowadays, one of the methods available to obtain the anhydrous ethanol is the extractive distillation process, which presents great potential depending on the solvent used. It is imperative that the solvent promotes dehydration, but low cost, the low energy consumption, and low waste generation and emissions must be taken into account. Within this context, there is high demand for new efficient solvents for extractive distillation of ethanol-water mixture, so, the ionic liquids (ILs) have some interesting properties for such applications. This work was performed in order to optimize the process using of the Plackett-Burman experimental design and the response surface methodology applied to the process of extractive distillation of azeotropic ethanol-water mixture, using the IL 1-butyl-3-methylimidazolium dicyanamide ([bmim] [N(CN)2]) as solvent. The choice of this IL as solvent was based on the data presented in the open literature.Plackett–Burman experimental design was used to evaluate the process variables. Then, these variables, called independent variables (Invar), were used in a central composite rotatable design for generating models to predict some parameters, such as the energy consumption, amount of IL used, purity and recovery of the ethanol obtained. This model was applied to an optimization algorithm, being possible to recover 99.39% of ethanol which enters the extractive distillation process with a purity of 99.76%mol, using a ratio of 0.074mol IL/mol ethanol at feed stream and consuming 3071.3kJ per kg anhydrous ethanol produced.