Separation of HFC-32 and HFC-125 Using Imidazolium Based Ionic Liquid + Polyvinyl Acetate Ionic Liquid Polymer Membranes

Hydrofluorocarbons (HFCs) are greenhouse gases commonly used in refrigeration systems. Current legislation has called for the phase-out and regulation of HFCs due to many of them having high global warming potentials. Since many refrigerants are azeotropic HFC mixtures, innovative and effective methods for separating these compounds are crucial. In the past, ionic liquids and polymers have been used separately for this application. The incorporation of ionic liquid into polymer membranes creates a great possibility for more efficient separations due to both entities having separation potential. Pure polymer membranes are able to separate gas mixtures by differences in the solubility and diffusivity of the gases. In this work, the permeability, selectivity, and solubility of difluoromethane (HFC-32) and pentafluoroethane (HFC-125) are investigated in ionic liquid polymer membranes of polyvinyl acetate (PVAc) with three ionic liquids: 1-hexyl-3-methylimidazolium ([C₆C₁im][Cl]), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₆C₁im][Tf₂N]), and 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate ([C₆C₁im][FAP]). The composite membranes were created with 0, 1, 5, 10, and 20 wt% ionic liquid. The membranes were evaluated for their glass transition temperature, density, molecular composition, and mechanical stability to investigate the effect of increasing ionic liquid concentration. Results of this study indicate that incorporating ionic liquids into polymer membranes can create solubility tunability for the separation of hydrofluorocarbons.