The restrictions imposed to the production of highglobal warming potential refrigerant gases have boosted the search of novel separation processes for the selective recovery of hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFO) from exhausted refrigerant mixtures. Membrane materials functionalized with ionic liquids can offer an effective techno-economical response to the challenging separation of HFC/HFO blends. In this work, we provide for the first time a thorough characterization of the gas solubility and permeation properties of three of the most relevant compounds for the future of the refrigeration and air conditioning sector, that is, difluoromethane (HFC-R32), 1,1,1,2-tetrafluoroethane (HFC-R134a), and 2,3,3,3-tetrafluoropropene (HFO-R1234yf), through composite ionic liquid−polymer membranes (CILPMs) that were prepared combining the Pebax 1657 copolymer with several ILs, [C 2 mim][SCN], [C 2 mim][BF 4 ], [C 2 mim][OTf], and [C 2 mim][Tf 2 N], varying the IL content in the range of 20−60 wt %. The CILPMs with the best separation performance and mechanical stability against feed pressure were those with 40 wt % of [C 2 mim][BF 4 ] and [C 2 mim][SCN]. For the 40 wt % [C 2 mim][BF 4] CILPM, the addition of IL promoted the permeability of the smallest molecules R32 and R134a and reduced the permeability of the largest molecule R1234yf, which resulted in 120 and 75% selectivity enhancement relative to that of the pristine polymer for R32/R1234yf and R134a/R1234yf mixtures, respectively. Finally, this CILPM was stable in the separation of two commercial HFC/HFO refrigerant blends (R513A and R454B) over a wide pressure range (up to 12 bar). These results indicate that CILPMs can be used for separating azeotropic and nearazeotropic exhausted HFC/HFO mixtures, which could stimulate the recovery and reuse of their components and thus avoid their emissions and pull down the demand for virgin refrigerants.

Membrane technology can play a very influential role in the separation of the constituents of HFC refrigerant gas mixtures, which usually exhibit azeotropic or near-azeotropic behavior, with the goal of promoting the reuse of value-added compounds in the manufacture of new low-global warming potential (GWP) refrigerant mixtures that abide by the current F-gases regulations. In this context, the selective recovery of difluorometane (R32, GWP = 677) from the commercial blend R410A (GWP = 1924), an equimass mixture of R32 and pentafluoroethane (R125, GWP = 3170), is sought. To that end, this work explores for the first time the separation performance of novel mixed-matrix membranes (MMMs) functionalized with ioNanofluids (IoNFs) consisting in a stable suspension of exfoliated graphene nanoplatelets (xGnP) into a fluorinated ionic liquid (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate ([C2C1py][C4F9SO3]). The results show that the presence of IoNF in the MMMs significantly enhances gas permeation, yet at the expense of slightly decreasing the selectivity of the base polymer. The best results were obtained with the MMM containing 40 wt% IoNF, which led to an improved permeability of the gas of interest (PR32 = 496 barrer) with respect to that of the neat polymer (PR32= 279 barrer) with a mixed-gas separation factor of 3.0 at the highest feed R410A pressure tested. Overall, the newly fabricated IoNF-MMMs allowed the separation of the near-azeotropic R410A mixture to recover the low-GWP R32 gas, which is of great interest for the circular economy of the refrigeration sector.

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