Investigation of the Influence Mechanism of CO2 Hydrate Formation in Seawater Systems in the Presence of Solid Promoters by Combining In Situ Raman Analysis with Macroscopic Experiments

Hydrate-based carbon dioxide (CO2) sequestration in the deep sea or marine strata is an important process in achieving carbon emission reduction. However, the micro mechanism of gas hydrate formation in a seawater system has not yet reached consensus, which restricts the development of the hydrate-based CO2 sequestration. The basic process of water conversion into hydrates is the transformation from disordered water molecules to a structurally ordered state under specific conditions. The influence mechanism of CO2 hydrate formation in seawater in the presence of solid promoters with or without chemical functional group modification was systematically investigated by combining in situ Raman analysis with macroscopic experiments. The results indicate that the hydrate formation is determined by the transformation from weak hydrogen bonds to strong hydrogen bonds; hydroxyl groups help improve the promoting effect, and the acidity of the solution increases due to the retention of CO2 in the solution, which inhibits the secondary formation of CO2 hydrates.