Current legislation calling for the phase out of hydrofluorocarbon (HFC) refrigerants is driving a global market shift that has prompted industry and research institutions to investigate new refrigerant mixtures and sustainable separation techniques for recycling refrigerants. The recent American Innovation and Manufacturing (AIM) Act of 2020 requires an 85% phase down of HFC production over the next 15 years. To achieve this goal, azeotropic refrigerant mixtures, such as R-410A composed of 50 wt % HFC-32 (difluoromethane, CH 2 F 2 ) and 50 wt % HFC-125 (pentafluoroethane, CHF 2 CF 3 ), will have to be separated to recycle the lower global warming HFC-32 component. The present work investigates the solubility of HFC-32 and HFC-125 in six ionic liquids (ILs) with halogen anions for the purpose of developing the thermophysical property data required for designing extractive distillation recycling processes and understanding the choice of cation and anion type. A gravimetric microbalance was used to collect isothermal vapor liquid equilibrium data for each of the ILs at 298.15 K and pressures from 0.05 to 1.0 MPa. The Peng−Robinson equation of state was used to model the solubility of the HFCs in the ILs. The solubility of HFC-32 in the ILs showed small differences, while the solubility of HFC-125 had significant variations with respect to the anion type and the cation alkyl chain length. Fick's law was applied to calculate diffusion coefficients for each HFC/IL system. HFC-32 has a greater diffusivity than HFC-125 based on smaller molecular size. The 1-n-hexyl-3-methylimidazolium chloride and the trihexyl(tetradecyl)phosphonium chloride ILs have the highest HFC-125/HFC-32 selectivity at 298.15 K. Based on both the mass uptake and selectivity ratio, these two ILs are potential entrainers for the separation of R-410A using extractive distillation.
Directional solvent extraction (DSE) is an emerging membrane-free liquid-liquid extraction process to desalinate water using low-grade heat. Several unique features make DSE a potentially disruptive desalination technology: 1) it is thermally driven and utilizes low-grade heat; 2) it does not require the use of membranes; 3) there are opportunities to intensify, modularize and customize
Separating azeotropic mixtures of hydrofluorocarbons
(HFCs) for
reuse and recycle is environmentally and economically imperative.
While ionic liquid (IL)-enabled HFC separations show promise, Edisonian
trial-and-error screening for the optimal IL entrainer is intractable
and expensive. Here, we propose an open-source, equation-oriented
modeling framework to rapidly translate HFC/IL solubility data into
regressed thermodynamic models which can be used for process design
under uncertainty and rapid IL screening. Moreover, we use data science
and process systems engineering tools to contemplate which data are
the most valuable for IL screening. We find that binary solubility
data collected at multiple temperatures is adequate for separation
process design, and newly available ternary solubility measurements
should be reserved for validation. Additionally, we use uncertainty
quantification analyses to show up to 10% experimental error is acceptable
for IL screening decisions. Informed by these results, we recommend
a multistep workflow for IL screening.
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