Influence of Memory Effect on the Growth Kinetics of Thermodynamically Promoted CO2 + H2 Hydrate for Rapid Hydrate-Based Gas Separation

Abstract

This study aimed to optimize the operating conditions and enhance the reaction rates of a hydrate-based gas separation process to facilitate environmentally friendly CO2 capture from fuel gas (CO2 + H-2) generated by natural gas reforming. Thermodynamic hydrate promoters, particularly tetrahydrofuran at 5.6 mol% and tetrabutylammonium bromide (TBAB) at 3.7 mol%, were used to alleviate strict equilibrium conditions and improve gas separation efficiency. To mitigate the effects of CO2 solubility, the gas-to-water ratio was maintained at 0.1. In addition, the influence of memory water on accelerating gas hydrate formation was explored by monitoring the hydrate formation behavior and changes in gas composition under isobaric condition based on the re-measured phase equilibrium data. The results showed that while the memory effect significantly reduced the induction time for hydrate formation, it did not influence the growth behavior or CO2 selectivity of the gas hydrates. Memory effect played a critical role in TBAB solution, particularly above the temperature required for pure clathrate formation. This study provides valuable insight into the roles of thermodynamic promoters and memory effects on the thermodynamic stability, induction time, and gas capture efficacy of gas hydrates, thereby contributing to the development of more efficient and environmentally sustainable gas separation technologies.