(653c) The Effect of Alkyl Chain Length on Imidazolium-Based Ionic Liquids and Choice of Halide Anions (Cl, Br, I) on Phase Equilibria for HFC-32, HFC-125, and Binary Mixtures (R-410A)

The current generation of refrigerants, hydrofluorocarbons (HFCs), are being phased out due to their high global warming potential (GWP) while the next generation of more environmentally friendly refrigerants, hydrofluoroolefins (HFOs), are developed and commercialized. Consequently, millions of tons of HFC mixtures will need to be recycled. Project EARTH (Environmentally Applied Research Toward Hydrofluorocarbons) is focused on developing efficient and selective separation processes for HFC mixtures. One promising approach is to use ionic liquids (ILs) as an entrainer to selectively separate azeotropic HFC mixtures like R-410A, which is composed of 50 wt.% HFC-125 (CHF₂CF₃) and 50 wt.% HFC-32 (CH₂F₂). The HFC-32 can be blended with HFOs to produce new products such as R-454B (68.9 wt.% HFC-32 and 31.1 wt.% HFO-1234yf (CH₂=CFCF₃)) and HFC-125 can be repurposed as a high-value fluorinated feedstock for production of new materials with a low-GWP.

This presentation will compare the effects of alkyl chain length on imidazolium-based ILs and anion substitution (Cl, Br, I) on the phase equilibria data for HFC-32 and HFC-125 and mixtures (e.g., R-410A). This presentation will also discuss ILs that are both solid and liquid at 25 °C. Phase equilibria data for HFC-32 and HFC-125 were measured using a Hiden Isochema IGA gravimetric balance and mixtures of HFC-32 and HFC-125 were measured using the first Hiden Isochema XEMIS Integral Mass Balance (IMB) method. The impact of alkyl chain length and anion on diffusion and selectivity will also be discussed for both pure HFC+IL and binary HFC+IL mixture measurements.