Synergistic Promotion of CO₂ Hydrate Formation by 1,3-Dioxolane and Sodium Lignosulfonate: A Study of Kinetic Characteristics

Capture and storage of CO2 (CCS) is recognized as an important, urgent, and necessary option to reduce CO2 emissions from the coal and oil and gas industries and to mitigate the severe impact of CO2 on the atmosphere and the environment. Hydrate-based approach is a new way to solve this challenge, but the challenge is how to synthesize hydrates rapidly and increase their growth rate and storage capacity. In this paper, two additives, 1,3-dioxopentacycline (1,3-DIOX) and sodium lignosulfonate (SL-Na), were selected for experimental studies of CO2 hydrate trapping at different concentration ratios, and the results showed that the two synergistically enhanced the kinetic process of the hydrates under a certain concentration of the compound system. Molecular dynamics simulations showed that the potential energy of the 1,3-DIOX + SL-Na + CO2 + H2O compound system was lower than that of the other systems, suggesting that a more stable CO2 hydrate would be generated within this compound system. The radial distribution function shows that 1,3-DIOX changes the structure of the hydrate, SL-Na enhances the solubilization of CO2 molecules, and the copresence of the two reduces the agglomeration force between CO2 molecules, which facilitates the diffusion of CO2 in the aqueous solution and the confinement of CO2 in the crystalline cages, and thus promotes the growth of the hydrate.