Toward the Recycling of Low-GWP Hydrofluorocarbon/Hydrofluoroolefin Refrigerant Mixtures Using Composite Ionic Liquid–Polymer Membranes

Fernando Pardo,Sergio V Gutiérrez-Hernández,Gabriel Zarca,Ane Urtiaga

doi:10.1021/acssuschemeng.1c00668

Fernando Pardo, Sergio V Gutiérrez-Hernández + Show 2 more

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https://doi.org/10.1021/acssuschemeng.1c00668

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Abstract

Authors fully acknowledge the financial support received from Project KET4F-Gas-SOE2/P1/P0823, which is cofinanced by the European Regional Development Fund within the framework of Interreg Sudoe Programme, and project PID2019-105827RB-I00—Agencia Estatal de Investigacion, Spain. F.P. acknowledges the postdoctoral fellowship (FJCI-2017-32884 Juan de la Cierva Formacion) awarded by the Spanish Ministry of Science, Innovation and Universities.

Highlights

Hydrofluorocarbons (HFCs), the 3rd generation of fluorinated gases (F-gases), are a family of synthetic compounds mainly used in the refrigeration and air conditioning (RAC) sector and as aerosols and foam blowing agents because of their weak impact on depleting the stratospheric ozone, good thermodynamic performance, and negligible toxicity.[1]
A well-reported trend is observed; the permeability of all studied gases through composite ionic liquid−polymer membranes (CILPMs) increases at higher ionic liquids (ILs) concentrations as a result of increased polymer chain mobility within the composite film.[39−41] It is verified that the order of gas permeability, that is, R32 > R134a > R1234yf, is consistent with the lower molecular size of R32 compared to that of R134a and R1234yf, as already stated in our previous work[26] regarding the permeation properties of these gases through polymer membranes prepared with different Pebax grades
In a similar way to R32/R1234yf separation, the largest anions with a significant degree of fluorination, such as OTf and Tf2N, exhibit lower separation capacity toward the R134a/R1234yf pair, which is consistent with the reported low solubility selectivity in ILs for this pair of gases.[11]. These results suggest that F-gas permeability through ILs is favored by strong enthalpic interactions (F-gases exhibit large electric dipole moments and H-bonding capability), the HFC/HFO separation selectivity may benefit from unfavorable entropic effects that hinder the solvation of large solutes in low-molar volume ILs, a fact that is in good agreement with available F-gas solubility studies in ILs.[11,16]

Summary

Introduction

Hydrofluorocarbons (HFCs), the 3rd generation of fluorinated gases (F-gases), are a family of synthetic compounds mainly used in the refrigeration and air conditioning (RAC) sector and as aerosols and foam blowing agents because of their weak impact on depleting the stratospheric ozone, good thermodynamic performance, and negligible toxicity.[1] because of their very high global warming potential (GWP) and the sustained increase in HFC emissions since 1990, a roadmap has been established to gradually eliminate their production and use through several international agreements and regulations such as the Kigali Amendment to the Montreal Protocol and the European Regulation on Fgases.[2−6] the current legislative and environmental framework demands the implementation of innovative technologies to improve the management of the end-of-life RAC equipment and promote the recovery, reuse, and recycling of refrigerants, with the aim of drastically reducing their emissions to the atmosphere In this context of transition to a low-carbon economy, some HFCs are being replaced by the 4th generation of F-gases, known as hydrofluoroolefins (HFOs), which present zero ozone depletion potential, negligible toxicity, reduced atmospheric lifetimes and GWPs that are several orders of magnitude below those of the most commonly used HFCs.[7] For instance, the HFO 2,3,3,3-tetrafluoropropene

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