The effect of sodium dodecyl sulfate and dodecyltrimethylammonium chloride on the kinetics of CO2 hydrate formation in the presence of tetra-n-butyl ammonium bromide for carbon capture applications

Tetra-n-butyl ammonium bromide (TBAB) is a commonly used promoter to moderate CO2 hydrate phase equilibrium. However, it decreases CO2 gas uptake. In this work, the effects of anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant dodecyltrimethylammonium chloride (DTAC) on the kinetics of CO2–TBAB hydrate formation are investigated. Experiments in a batch reactor at the same initial pressure of CO2/N2 gas mixtures are conducted in systems of 10-wt% TBAB and varied SDS concentrations of 0–1500 ppm and DTAC concentrations of 0–0.6 wt%. Induction time, normalized gas uptake, split fraction and separation factor are the metrics to study in this paper. The results show that the hydrate formation is most accelerated with the addition of SDS, and the best CO2 separation performance is achieved in the presence of DTAC. 10-wt%TBAB with 0.1-wt% DTAC is found to be the optimum recipe, and it leads to the same amount of CO2 uptake at 283.15 K as that in a pure water system at 276.45 K under the same initial pressure. CO2 uptake is also found to increase with a higher subcooling. Furthermore, the intensive uptake period of different systems is determined for practical applications of hydrate-based carbon capture.