Simultaneous Optimal Design of an Extractive Column and Ionic Liquid for the Separation of Bioethanol–Water Mixtures

Abstract

Recently renewed interest in the optimal design of sustainable processing systems has emerged as consequence of pollution issues and global climate changes. The replacement of hazardous industrial solvents widely used for azeotropic separations is clearly a challenging research area for new products design. However, as important as product design is, the design of the optimal processing configuration where the azeotropic separation will take place is also a key issue. As a matter of fact, the strong interaction between product and process design indicates that better optimal processing conditions can be attained by solving both problems simultaneously rather than sequentially. In the present work, we take advantage of this natural interaction for the optimal simultaneous design of both ionic liquids and an extractive distillation column for the high purity separation of the ethanol/water azeotropic mixture for deploying ethanol as a biofuel. The problem is formulated as a steady-state disjunctive mixed-integer nonlinear programming (MINLP) problem. The results indicate that new green solvents constitute a good replacement for hazardous solvents. Because ionic liquids are expensive solvents, it is worth it to explore the deployment of advanced optimization tools for profit maximization of sustainable processing systems. Through the use of the proposed MINLP formulation, improved ethanol/water separation configurations deploying ionic liquids were attained. Because ethanol features high purity, it can be used for biofuel applications.

A systematic approach to design task-specific ionic liquids and their optimal operating conditions

“…(30) where g CH 3 is the number of CH 3 groups in the selected cation and is the number of CH 3 group in the individual cation structure. CH 3 groups present in the cation core should be quantified and added to the UNIFAC model calculation.…”

“…The process model constraints were modelled through eqn (37)- (48), based on eqn (10)- (25). The remaining equations are structural constraints formulated from eqn (26)- (30). To minimise pumping costs and to increase mass transfer rates, an IL with low viscosity is desired.…”

“…McLeese et al 28 applied the CAMD approach to design ILs to be used in conjunction with refrigerants, within an absorption refrigeration system. 30 Roughton et al 31 also proposed to design IL entrainers and azeotropic separation processes at once, using a newly developed solubility parameter model that is based on the GC method and the UNIFAC-IL model. However, the design of cation was not considered in this work, which reduces the complexity of the optimisation problem.…”

Computer‐aided design of ionic liquids as solvents for extractive desulfurization

“…However, in comparison to the large variety of IL types and the huge diversity of IL‐involved applications, the available groups in the current UNIFAC‐IL models cover only a small subset of the IL structural space. Due to this limitation, only very few studies on designing ILs for separation processes by the CAMD approach, that is, computer‐aided IL design (CAILD), have been published . These CAILD studies are mainly dealing with alcohol‐water separation via extractive distillation and with CO 2 capture processes whereby only a small number of possible IL groups have been taken into account.…”

CO2 capture by methanol, ionic liquid, and their binary mixtures: Experiments, modeling, and process simulation

“…A number of predictive thermodynamic models are available for modeling the solubility of CO 2 in ILs . Among others, the universal quasichemical (UNIQUAC) functional‐group activity coefficients (UNIFAC) model for ILs constantly developed by our group (UNIFAC‐Lei model) has attracted wide attention, and it produces solid outcomes in various‐specific applications due to the unique advantages: (1) it provides quantitative accurate predictions; (2) its formulation is simple, and thus the calculation speed is rapid; (3) its parameters can be readily utilized in the modern simulation packages (e.g., Aspen Plus, PROII, and ChemCAD) for simulation and optimization of the desired industrial processes; and (4) in terms of the UNIFAC‐Lei preferable decomposition approach, the introduced main groups and subgroups together with their derived parameters are appropriate for the ILs‐based designing methodologies for specific applications . Thus, the UNIFAC‐Lei model has been extended in this work to predict the solubility of CO 2 in the proposed solvents.…”