Study on the effect of carbon nanotubes on the kinetics of CO2 hydrate formation under the synergistic effect of trace surfactants based on hydrophobic effect

Greenhouse gas emissions are a primary driver of global warming. Thus, effective utilization, capture, or conversion of CO₂ into clean energy is vital for global environment and industrial development. The formation of CO₂ hydrates, however, presents a promising approach to address these challenges. In this study, five different concentrations of pure multi-armed carbon nanotubes (MWCNTs) were tested in three different systems: a binary composite sodium dodecyl sulfate (SDS) system (MWCNTs + 300 ppm SDS), a binary composite dodecyl trimethyl ammonium chloride (DTAC) system (MWCNTs + 300 ppm DTAC), and a ternary composite system (MWCNTs + 300 ppm SDS + 300 ppm DTAC). The experiments investigated the kinetics of CO₂ hydrate formation. The results revealed that the gas consumption in all three systems peaked at a MWCNTs concentration of 0.03 mg/ml. At this concentration, the ternary composite system showed a 7.63 % (±1.26 %) higher gas consumption than the binary SDS system, and a 13.62 % (±0.19 %) higher consumption than the binary DTAC system. Induction time decreased progressively with increasing MWCNTs concentration, reaching its shortest value at 0.09 mg/ml. At this point, the ternary composite system exhibited a 43.75 % reduction in induction time compared to the binary SDS system, and a 68.75 % reduction compared to the binary DTAC system. Furthermore, a comparison between the ternary composite MWCNTs system and the ternary composite NH₂-MWCNTs system showed that the latter promoted hydrate formation slightly better, though the difference was not significant. This research will contribute to advancing the commercialization of CO₂ capture and storage technologies based on hydrate formation.