Laboratory-scale studies on the effect of promoters on CO2 capture and sequestration via hydrate method: A comprehensive review

CO2 capture and sequestration via the hydrate method has attracted much attention because of its high sequestration density and energy density. However, the influencing mechanism of the promoters on the formation of CO2 hydrate was not yet clarified. Also, there was no comprehensive review of the effect of promoters on CO2 hydrate formation from laboratory-scale studies. Therefore, this paper reviewed the effect of promoters on CO2 capture and sequestration via the hydrate method from the laboratory research scale. Typical CO2 hydrate formation processes were summarized in detail. And the characteristic parameters of CO2 hydrate were analyzed. Then, the different types of promoters were carefully overviewed. In particular, the influencing mechanisms of promoters on CO2 hydrates were highlighted and compared. Thermodynamic promoters mainly affected the conditions of hydrate formation, while kinetic promoters mainly acted at the gas-liquid contact interface. However, the promotional mechanism of CO2 hydrate promoters was controversial and the solution formulation units were not consistent. In addition, the effects of different promoters on CO2 capture, separation, and sequestration were also summarized. The existing studies ignored the CO2 hydrate formation experiments under in-situ conditions in the presence of promoters. The influence of different promoters on the sequestration effect was critically evaluated through parameters such as phase equilibrium curves, induction time, gas consumption, and sequestration density. A uniform evaluation standard for CO2 hydrate promoters was lacking. Finally, future development recommendations should focus on large-scale, low-energy, commercial, in-situ, environmentally friendly, and intelligent research directions. The review may provide some theoretical guidance for the commercial application of CO2 hydrate.