Visualization study of the effects of polycarboxylates on CO₂ hydrate generation and interfacial property

Marine carbon sequestration, with its high potential and low risk of leakage, is an attractive technology for effectively addressing global climate change and reducing greenhouse gas emissions. A current concern about marine sequestration lies in the potential negative effects of the carbon sequestration process on the marine environment. CO₂ hydrate sequestration is considered to be one of the most stable method of sequestration, and researchers are actively searching for promoters that facilitate hydrate sequestration and are friendly to the marine environment. Therefore, the development and utilization of environment-friendly promoters are of great significance for marine carbon sequestration by the hydrate method. In this study, two novel kinetic promoters, polycarboxylates (SP-409 and SPC-100), were applied. The changes in kinetic properties of CO₂ hydrate generation and gas-liquid interfacial properties were investigated under different promoter types and concentrations, temperatures, and pressures. Visual observation reveals that the formation of hydrate first occurs at the gas-liquid interface and on the reactor wall, then gradually starts to diffuse into the interior of the solution, forming a white cylindrical solid with a hollow interior. After a comprehensive comparison of temperatures, pressures, and concentrations, the SP-409 solution promoted hydrate generation better than the SPC-100 solution, and the optimal promotion concentration was 1000 ppm. In addition, there is an exponential relationship between the rate of hydrate formation and interfacial tension (IFT), which means that the rate of hydrate generation can be quickly estimated from the interfacial tension data at a certain temperature and pressure.