Screening of ionic liquids for HCl absorption and their applicability via a multi‐scale approach

Abstract Efficient separation of hydrogen chloride (HCl) is vital for its resource utilization. Ionic liquids (ILs) are a potential absorbent, while their rational screening from countless species remains challenging. Here, a multi‐scale framework was established for the assessment of ILs based on quantum chemistry (QC) calculation, conductor like screening model for real solvents (COSMO‐RS) model, process simulation, and experimental verification. The solubility behavior of HCl in various ILs was studied, and the dissolution mechanism was revealed by Fourier transform infrared (FT‐IR), nuclear magnetic resonance (NMR) spectra and QC. The results show that the anion of the ILs played a leading role for the solubility of HCl, and their stability and solubility behavior can be regulated effectively by their H‐bonding capacity and alkalinity. The absorption/desorption performance of the ILs was evaluated through process simulation. Imidazolium chlorides are determined as a promising solvent for HCl absorption, and the multi‐scale framework is viable for the efficient screening of ILs and mechanism analysis for a gas absorption process.