The Effect of Silica Gel Nanopores and Surfactants on Co2 Hydrate Formation Kinetics : An Experimental and Modeling Study Based on Shrinking Core Model

The carbon dioxide (CO2) hydrate formation kinetics with the addition of surfactants sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) are studied in silica gel (SG) particles, which can greatly enhance gas–water mass transfer. Experiments are implemented with varied SG pore sizes of 30, 50 and 100 nm. An advanced shrinking core model is established considering CO2 dissolved in the water and capillary effect in the hydrate shell to study CO2 hydrate formation kinetics in the presence of nanopores and surfactants. The experimental results show a remarkable increase in both gas uptake yield and gas uptake rate in larger pores SG, but an inhibition effect is found in 30-nm SGs with 500-ppm SDS. The simulation results reveal that surfactants can increase the reaction rate constant, saving up to 49.3% time to achieve the same amount of gas uptake in 100-nm SG with 500-ppm SDS. The water consumed by capillary effect is more dominant in smaller pores, and the proportion of water consumed by capillary effect to the total water consumption raised to up to 76% in the presence of surfactants, due to the more capillaries with larger radius formed in the hydrate initially with the help of surfactants