Hydrate-based continuous hydrogen gas separation from mixing gas containing carbon dioxide with cyclopentanone

Abstract

Clathrate-hydrate-based H₂ separation is superior to conventional separation methods in terms of energy consumption, but the criteria for selecting promoters that facilitate stable hydrate formation and gas separation are unclear. We conducted continuous and batch separation experiments in a CO₂ + H₂ + cyclopentanone (CP-one) system and powder X-ray diffraction (PXRD) measurements of the hydrate formed in this system. While the mole fraction of H₂ in the gas phase increased from 0.60 to 0.90 in continuous separation, CO₂ in the hydrate phase remained at 0.90. PXRD measurements revealed that CO₂ + H₂ + cyclopentanone hydrate possesses the structure II hydrate, suggesting CO₂ and CP-one encapsulation in small and large cages of hydrate. Compared to previous studies using tetrahydropyran and cyclopentane as guest compounds, CP-one with high water solubility facilitated kinetics of the hydrate, encapsulation of CO₂ in the hydrate and more stable separation. This study would provide a comprehensive understanding of selecting guest compounds for hydrate-based separation.