Enhancing R410A blend separation by using ionic liquids: From UNIFAC model extension, solvent design to molecular dynamics simulation

Abstract

The selective separation of refrigerants could facilitate their reclamation and reduce emissions of hydrofluorocarbons (HFC) with high global warming potential. R410A, a near azeotropic mixture comprising equimass difluoromethane (R-32) and pentafluoroethane (R-125), is required to be phased out and shortly replaced by more efficient and sustainable refrigerants. Under this background, the recovery of R-32 and R-125 by using ionic liquids (ILs) as the solvent is considered as a promising approach. In this work, the rational selection of ILs for enhancing the R410A separation is presented. To this end, 873 refrigerant-in-IL solubility data (573 for R-32, 300 for R-125) are firstly adopted for the extension of the UNIFAC-IL model to cover the R410A system. With the obtained UNIFAC-IL model, a computer-aided IL design (CAILD) task is cast as a mixed-integer nonlinear programming (MINLP) problem, which is solved to identify three top-ranked ILs. Following that, molecular dynamics (MD) simulations of the selected IL-refrigerant systems are conducted, which well elucidate the reliability of the CAILD results.