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Polymer/ionic liquid pilot scale membrane prototype for the recovery of difluoromethane (R-32) from refrigerant mixtures

Abstract: Difluoromethane (R-32) is a hydrofluorocarbon (HFC) that has been massively used over the last 30 years in refrigeration and air conditioning as a primary component of azeotropic or close boiling refrigerant mixtures. Despite environmental directives commanded to drastically reduce the use of HFCs, R-32 has excellent thermodynamic properties and moderate GWP, thus its recovery from depleted mixtures collected from end-of-life equipment is sought to synthesize alternative low-GWP refrigerant blends. Membrane separation using composite polymer/ionic liquid membranes based on poly-ether-block-amide have shown potential to separate R-32 from other fluorinated hydrocarbons, yet the development of this type of composite membranes still remains at laboratory scale. In this work, a spray coating technique was successfully applied to create defect-free thin selective layers of neat Pebax®1657, Pebax®1657/40 wt% [C2C1im][BF4] and Pebax®1657/40 wt% [C2C1im][SCN] coated on porous PVDF substrates. This methodology was transferred from the lab-scale tests (12.6 cm2) to a custom pilot set-up (300 cm2). The pilot results confirmed the superior performance and stability of [C2C1im][SCN]-based membranes, which allowed the recovery of up to 64.3% and 67.1% R-32 from the refrigerant mixtures R-410A (69.8 mol % R-32 and 30.2 mol % R-125) and R-454B (82.1 mol % R-32 and 17.9 mol % R-1234yf) at 6 bar, increasing the R-32 permeate concentration up to 89.6 and 95.9 mol %, respectively. These results highlight the need to expand the knowledge of this type of gas separation membranes towards thinner and defect-free selective dense layers with the purpose of approaching their real applications.

 Authorship: Pardo F., Gutiérrez-Hernández S.V., Rodríguez-San Miguel P., Zarca G., Urtiaga A.,

 Fuente: Separation and Purification Technology, 2023, 320, 124115

 Publisher: Elsevier

 Publication date: 01/09/2023

 No. of pages: 11

 Publication type: Article

 DOI: 10.1016/j.seppur.2023.124115

 ISSN: 1383-5866,1873-3794

 Spanish project: PID2019-105827RB-I00

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