Computer-aided ionic liquid design for separation processes based on group contribution method and COSMO-SAC model

•A computer-aided ionic liquid design methodology (CAILD) is developed.•Extended GC-COSMO is established to estimate σ-profile and cavity volume of an ionic liquid.•Contribution parameters of 61 cation groups are regressed and validated.•The CAILD methodology is tested by examples of extraction and absorption.

For design of ionic liquid (IL) solvents for a specific separation process, a computer-aided ionic liquid design (CAILD) method based on multi-scale simulations is presented. A new group contribution based approach GC-COSMO for ILs is established for estimating the σ-profiles and cavity volumes of cations, where ILs are structured by three parts, i.e., one anion, one cation skeleton, and substituents on cation skeleton. Prediction models, including the COSMO-SAC model for thermodynamic properties and semi-empirical models for physical properties, are integrated into a computational IL design framework. A mixed-integer nonlinear programming (MINLP) problem is then formulated to optimize the separation performance combing the constraints of structural feasibility and physical properties. The optimal IL solvents are identified using a deterministic optimization method with branch and bound algorithm. The CAILD method is successfully tested for two typical separation examples, i.e. extraction of benzene from cyclohexane and post-combustion CO2 capture.

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