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.