Separation of refrigerant gas mixtures containing R32, R134a and R1234yf through poly(ether-block-amide) membranes

Hydrofluorocarbons (HFCs) are powerful greenhouse gases whose production and consumption must be phased down in order to reach the reduction goals established by the Kigali Amendment to the Montreal Protocol. However, the share of recycled refrigerant gases remains very low owing to the extremely inefficient separation of refrigerant mixtures by cryogenic distillation. In this sense, the HFCs, difluoromethane (R32, GWP = 675) and 1,1,1,2-tetrafluoroethane (R134a, GWP = 1430), together with the hydrofluoroolefin (HFO) 2,3,3,3-tetrafluoropropene (R1234yf, GWP = 4), are among the most common constituents of HFC/HFO refrigerant mixtures currently employed in the refrigeration and air-conditioning sector. Therefore, the feasibility of using membrane technology for the selective separation of these compounds is assessed in this work for the first time. A comprehensive study of their gas permeation through several poly(ether-block-amide) (PEBA) membranes that differ on the content and type of backbone segments is performed. Results show that PEBA membranes exhibit superior permeability of R32 (up to 305 barrer) and R134a (up to 230 barrer) coupled with reasonably high selectivity for the gas pairs R32/R1234yf (up to 10) and R134a/R1234yf (up to 8). Moreover, for the blends R32/R1234yf and R32/R134a, the membrane separation performance is not significantly affected under the mixed gas conditions tested. Thus, results evidence that consideration should be given to membrane technology for the cost-efficient separation of HFC/HFO mixtures in order to boost the recycling of these compounds.

This research is supported by Project KET4F-Gas-SOE2/ P1/P0823, which is co-inanced by the European Regional Development Fund within the framework of Interreg Sudoe Programme. The authors acknowledge the collaboration of Dr. Mar Lopez-Gonza ́ lez and Dr. Rosario Benavente (Institute of Polymer Science and Technology-CSIC) to perform the sorption and DSC experiments. F.P. acknowledges the postdoctoral fellowship (FJCI-2017-32884, ‘Juan de la Cierva Formacioń ’) from the Spanish Ministry of Science, Innovation and Universities)