Experimental Study on the Mechanism of Enhanced CO2 Hydrate Generation by Thermodynamic Promoters

CO2 capture by hydrates is attracting worldwide research interest. In particular, the mechanisms of various additives are being actively studied. In this study, static hydrate formation experiments were performed at pressures of 2.5 and 3.5 MPa and at 0.5 °C using three thermodynamic promoters. The results revealed that 39 wt % TBAB and the CP system could enhance hydrate formation and CO2 capture at the two experimental pressures. The same effect was observed for the THF system at 3.5 MPa, and all systems except the CP system at 3.5 MPa accelerated the hydrate formation. By building a Raman observation system and the use of differential scanning calorimetry, we found that the hydrate formation process in the thermodynamic promoter system can be divided into three stages: promoter hydrate formation, crystal size adjustment, and induction of CO2 hydrate formation. It was observed that the formation and crystal stability of the thermodynamic promoter hydrate were key to the acceleration of CO2 hydrate formation. This finding indicated that the promoter of the CO2 hydrate has an “optimal induction size.” This study provides a theoretical foundation for the further development of CO2 capture and storage technology involving the use of the hydrate method.