Comparison of SDS and L-Methionine in promoting CO2 hydrate kinetics: Implication for hydrate-based CO2 storage

The continuously increasing CO2 emissions since industrialization has sparked widespread concerns on environmental and climate change issues. Carbon sequestration and storage technologies (e.g., hydrate-based CO2 sequestration) present promising potential for the disposing of excessive CO2 in geological media. High gas uptake capacity and rapid CO2 hydrate formation kinetics are required for the application of such a technology. In this study, we compared the kinetic promotion effects of sodium dodecyl sulfate (SDS) and L-methionine ((L)-Met) on CO2 hydrate with the objective of identification of an effective and eco-friendly CO2 hydrate kinetic promoter. The experimental results suggested that L-Met (0.1 wt%) promotes CO2 hydrates formation significantly with a gas uptake in CO2 hydrate five times more than SDS at the same concentration. The hydrate morphology observations indicated that the wall-climbing hydrates associated with the addition of (L)-Met induced by the capillary driving force offer a possible explanation for the difference in the observed kinetics. A novel calculation method was developed to quantify the partition of CO2 in gas, liquid and hydrate phases. Increasing the initial gas-liquid ratio promotes CO2 stored in the hydrate phase as solid rather than in the liquid phase as dissolution. We further demonstrated the reusability of (L)-Met in five consecutive cycles of CO2 hydrate formation and dissociation. It was assessed that (L)-Met as a CO2 hydrate kinetic promoter is superior to SDS and can be employed as an efficient, reliable and eco-friendly kinetic promoter for the hydrate-based CO2 sequestration technology.