Computer-aided design of ionic liquids for hybrid process schemes

Abstract Hybrid process schemes that combine two (or more) units operating at their highest process efficiencies to perform one (or more) process tasks are considered as potentially innovative and sustainable processing options. Additionally, Ionic liquids (ILs), as well as certain organic chemicals, are good candidates for use as solvents in hybrid schemes that can replace energy-intensive processing steps. As successful design of solvent-based hybrid schemes depends on the specific properties of the solvent used, a computer-aided ionic liquid design (CAILD) toolbox was added to an existing tool for computer-aided molecular design for solvent selection-design. Promising IL solvent candidates were first identified through the formulation and solution of mixed-integer nonlinear programming (MINLP) problems for CAILD and were then further evaluated in the process simulation design stage, where the process variables were optimized by means of trade-off and sensitivity analysis. In order to understand and develop model-based hybrid reaction systems, a dynamic model that describes the behavior of the reaction system has been developed. Based on a wide range of collected experimental data, parameters of sub-models, used to calculate the temperature-dependent properties of ILs, are regressed for the purpose of process simulation. Consequently, a hybrid process design method combining CAILD and process design-simulation to identify the optimal IL and its corresponding hybrid process specifications has been proposed. The application of this design method has been illustrated through case studies including the separation of aqueous solutions using an IL-based hybrid distillation scheme and the bio-oxidation of alcohols using a hybrid reaction-separation scheme with continuous product removal.