COSMO-RS guided screening of ionic liquids for the separation of fluorinated greenhouse gases R-410A: Delving into anion, cation effects, and hydrogen bond dynamics

Gongran Ye; Xilei Wu; Neng Gao; Yingjie Xu; Zhikai Guo; Xiaohong Han

doi:10.1016/j.envres.2023.117386

COSMO-RS guided screening of ionic liquids for the separation of fluorinated greenhouse gases R-410A: Delving into anion, cation effects, and hydrogen bond dynamics

Environ Res. 2023 Dec 15;239(Pt 2):117386. doi: 10.1016/j.envres.2023.117386. Epub 2023 Oct 13.

Authors

Gongran Ye¹, Xilei Wu², Neng Gao³, Yingjie Xu⁴, Zhikai Guo⁵, Xiaohong Han⁶

Affiliations

¹ Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou, 310027, China. Electronic address: gongranye@zju.edu.cn.
² Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou, 310027, China. Electronic address: Lu_wxl@zju.edu.cn.
³ Ningbo Institute of Technology, Zhejiang University, Ningbo, 315100, China. Electronic address: gao@zju.edu.cn.
⁴ Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, 310014, China. Electronic address: xuyingjie@zjut.edu.cn.
⁵ State Key Lab for Fluorine Greenhouse Gases Replacement and Control Treatment, Zhejiang Research Institute of Chemical Industry, Hangzhou, 310023, China. Electronic address: guozhikai@sinochem.com.
⁶ Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou, 310027, China. Electronic address: hanxh66@zju.edu.cn.

PMID: 37839536
DOI: 10.1016/j.envres.2023.117386

Abstract

Reclamation of high-GWP near-azeotropic refrigerant R-410A (50 wt% R-32 (difluoromethane) + 50 wt% R-125 (pentafluoroethane)) can be an effective way to mitigate the greenhouse effect and achieve a circular economy. Efficient ionic liquids (ILs) as extractants needed to be found for the extractive distillation (ED) separation process of R-410A. Given the numerous combinations of cations and anions in ILs, the discovery of an efficient IL via experimental methods proves to be an exceedingly complex task. In this work, the solubilities of R-32, and R-125 in 840 conventional ILs (comprised of 20 cations and 42 anions) were analyzed based on infinite dilution activity coefficient. The absorption mechanisms of R-32 and R-125 in ILs were elucidated by analyzing excess enthalpy (H^E), excess Gibbs free energy (G^E)) and surface charge density distribution through COSMO-RS (Conductor-like Screening Model for Real Solvents). Results revealed that H^E and G^E of the mixture formed by R-125 and most ILs surpassed those of R-32, resulting in higher solubility of R-32 in most ILs compared to R-125. Structural changes of anions and cations had a greater effect on the solubility of R-125 in ILs. It is found for the first time that the existence of a strong hydrogen bond donor region in cations/anions generated intense repulsion with the hydrogen atom in R-125. Furthermore, a large area of weak polarity on the surface of cations/anions was difficult to form an effective charge shield with fluorine atoms in R-125, thus inhibiting the dissolution of R-125. Finally based on the identified interaction sites, combined with melting point and viscosity, some novel functional ILs with high selectivity for R-32 + R-125 were designed and determined for actual separation process. These findings significantly enrich the understanding of the solubility mechanism and provide theoretical guidance for designing new ILs for R-410A reclamation.

Keywords: COSMO-RS; Ionic liquids; R-410A; Refrigerant reclamation; Solubility.

MeSH terms

Anions / chemistry
Cations / chemistry
Greenhouse Gases*
Hydrogen Bonding
Ionic Liquids* / chemistry

Substances

Ionic Liquids
Greenhouse Gases
Anions
Cations