Optimizing Hydrate-Based CO2 Capture in Saline Environments Using Low-Dosage THF for Seawater Utilization

Abstract

This study investigated the influence of low-dosage thermodynamic promoters on gas hydrate-based CO2 capture from CO2 + N-2 mixtures in saline environments for offshore applications. Phase equilibria measured in the presence of 0.1 and 1.0 mol% tetrahydrofuran (THF) demonstrated that a small amount of THF mitigated the inhibition effect of NaCl. However, the promotion effect diminished with increasing pressure, possibly due to the transfer of a small fraction of THF molecules to the vapor phase at high pressure. Weight fractions calculated from Rietveld analysis revealed that low-dosage THF promoted sII hydrate formation, enhancing thermodynamic stability. Cage-dependent guest occupancy indicated that higher THF concentrations in solution decreased both CO2 selectivity and capacity, as N-2 was preferentially captured in the small cages of sII hydrates. These findings provide insights into optimizing hydrate-based CO2 capture in offshore environments by balancing thermodynamic stability enhancement with CO2 separation efficiency.