Ionic liquid based absorption separation of fluorinated Refrigerants: UNIFAC model Extension, molecular Design, and mechanism analysis

The selective separation of fluorinated refrigerants (FR) is necessary to enable their reuse and thereby reduce emissions of hydrofluorocarbons (HFC), which are increasingly concerning due to their high global warming potential. To this end, a computer-aided ionic liquid design (CAILD) is conducted for commercially available HFC/HFC and HFC/hydrofluoroolefin (HFO) blend separations in the refrigerant industry. Experimental FR-in-IL solubility data are comprehensively collected and used for the task-specific extension of the UNIFAC-IL model to cover IL-FR systems. Using azeotropic R125/R143a and R134a/R1234ze(E) systems as representative case studies, a mixed-integer nonlinear programming (MINLP)-based CAILD problem is formulated and solved by integrating the extended UNIFAC-IL model with an IL physical property prediction model. The optimal ILs with the best separation performance, namely [dmpy][Ac] and [P₆₆₆₁₄][Ac], are identified for separating R125/R143a and R134a/R1234ze(E), respectively. The separation mechanisms are finally disclosed through molecular insights obtained by molecular dynamics simulations, σ-profile analysis, and quantum chemistry calculations, which jointly validate the reliability of the CAILD results.