Exploring C3F8 as a gaseous structure H hydrate former: Implications for hydrate-based greenhouse gas separation and recovery

Abstract

Octafluoropropane (C3F8) is a fluorinated gas (F-gas) known for its high global warming potential. In this study, the role of C3F8 as a novel gaseous structure H (sH) hydrate former was investigated. By employing a comprehensive methodology involving thermodynamic, crystallographic, and spectroscopic analyses, the successful encapsulation of C3F8 into the large cages of sH hydrates was unveiled for the first time. The incorporation of C3F8 into sH hydrates was inferred from a shift in the thermodynamic hydrate phase equilibria, and unequivocal evidence of successful C3F8 encapsulation was obtained using powder X-ray diffraction, 13C nuclear magnetic resonance, and Raman spectroscopy. The findings showed that C3F8 overcame the conventional limitations associated with sH hydrate formers, which are predominantly liquid and solid substances, thereby significantly expanding the scope of potential gaseous sH hydrate formers. This advancement not only enhances the fundamental understanding of gas hydrate formers but also opens up new avenues for hydrate-based technologies, particularly in the separation and recovery of large-size F-gases, which have substantial environmental implications.