Ionic Liquid Design and Process Simulation for Decarbonization of Shale Gas

TLDR

Ionic liquids are increasingly considered for decarbonizing methane, but the vast number of possible ILs makes selecting the optimal CO2‑removal solvent challenging. The study proposes a screening method for ILs using COSMO‑RS, an absorption mechanism, and experimental data. The method incorporates COSMO‑RS predictions, Henry’s constants, viscosity, toxicity, a rigorous thermodynamic model, and process simulations of single‑stage and multistage flash options to evaluate IL‑based decarbonization. The screening identified [bmim][NTf2] as the most promising IL, and simulations—validated against experiments—show that single‑stage and multistage flash processes cut energy consumption by 42.8 % and 66.04 % compared to MDEA.

Abstract

Ionic liquids (Ms) have been receiving increasing attention as a potential decarbonization solvent. However, the enormous number of potential ILs that can be synthesized makes it a challenging task to search for the best IL for CO2 removal from methane. In this work, a method was proposed to screen suitable ILs based on the COSMO-RS (conductor-like screening model for real solvents) model, an absorption mechanism, and experimental data. Besides the Henry's constant, the viscosity and toxicity of ILs should also be taken into consideration for an industrial decarbonization process. Furthermore, process simulation was performed to evaluate the new IL-based decarbonization technology. Considering CO2 solubility, CO2/CH4 selectivity and toxicity and viscosity of ILs, [bmim][NTf2] has been screened to be the potential solvent among 90 classes of ILs. Based on reliable experimental data, a rigorous thermodynamic model was established. The simulation results have been found to agree well with the available experimental results. Two process flow sheet options, use of two single-stage flash operations or a multistage flash operation following the absorber, have been simulated and assessed. Compared with the well-known MDEA (methyldiethanolamine) process for CO2 capture, the single-stage and multistage process alternatives would reduce the total energy consumption by 42.8% and 66.04%, respectively.