Coupling Amino Acid with THF for the Synergistic Promotion of CO2 Hydrate Micro Kinetics: Implication for Hydrate-Based CO2 Sequestration

CO2 capture and sequestration are broadly recognized as the most effective technology for reducing CO2 emissions and mitigating global climate change. In this regard, hydrate-based CO2 sequestration (HBCS) has been proposed as an effective method for long-term safe and stable CO2 sequestration. It is a promising technology for reducing the concentration of CO2 in the atmosphere and achieving carbon neutrality. However, one major challenge related to HBCS technology is the lack of understanding of how to improve the formation kinetics of CO2 hydrate effectively. Herein, in this study, we identified the synergistic promotion effect on CO2 hydrate formation when a low-dose thermodynamic promoter (tetrahydrofuran, THF) is coupled with an environment-friendly kinetic promoter (l-methionine, l-Met). Based on the kinetic experiments and the morphological observation, 0.6 mol % THF coupled with 0.1 wt %l-Met yields the optimal CO2 gas uptake. In situ Raman spectra reveal the mechanism of the observed two-step growth behavior at the molecular level, where low-dose THF promotes the initial CO2-THF sII hydrate nucleation and growth in the solution and l-Met promotes the subsequent CO2 sI hydrate growth along the surface of the reactor. Our study unveils the underlying synergistic mechanism when thermodynamic and kinetic promoters are coupled for CO2 hydrate formation. The results provide guidance for the identification and use of novel bio-friendly thermodynamic and kinetic promoters and are beneficial to a series of sustainable hydrate-based technologies when fast CO2 formation is required.