Ionic Liquids Can Enable the Recycling of Fluorinated Greenhouse Gases

LF Lepre and D Andre and S Denis-Quanquin and A Gautier and AAH Padua and MC Gomes, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 7, 16900-16906 (2019).

DOI: 10.1021/acssuschemeng.9b04214

Recycling fluorinated gases that have high global warming potential is crucial for a sustainable and responsible use of mobile air conditioners. In this context, five ionic liquids with different hydrogenated or fluorinated alkyl chains in the ions were designed to improve the absorption of the refrigerant 1,1,1,2-tetrafluoroethane, commonly known as R134a. R134a is one of the most used refrigerant gases, and its global warming potential is several orders of magnitude higher than that of carbon dioxide. Gas solubility was measured between 303 and 343 K up to 3.5 bar and follows the order C(2)C(1)ImNTf2 < C(8)C(1)ImNTf2 < C(8)C(1)ImBETI < C(8)H(4)F(13)C(1)ImNTf2 < C(8)H(4)F(13)C(1)Im BETI. The R134a solubility increases in ionic liquids having fluorinated moieties in the ions, a behavior that could be linked to a more favorable entropy of solvation. R134a absorption is always selective toward atmospheric gases like nitrogen, ionic liquids with fluorinated moieties being more selective to separate R134a from ethane (C2H6) while their hydrogenated counterparts are more suited to separate R134a from perfluoroethane (C2F6). Overall, this study provides a comprehensive perspective on how the fluorination of ionic liquids can be explored to selectively recycle fluorinated greenhouse gases.

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