Investigation of functionalized carbon nanotubes' performance on carbon dioxide hydrate formation

Abstract In this work, the impact of functional group on the thermodynamics and kinetics of CO 2 hydrates are investigated experimentally. The hydroxylated multi-wall carbon nanotubes (OH-MWCNT) and carboxylated carbon nanotubes (COOH-MWCNT) along with pristine carbon nanotubes (MWCNT) are selected for this study. The carbon nanotubes are suspended in a 0.03 wt% sodium dodecyl sulfate (SDS) aqueous solution and the results are compared with SDS aqueous solution at the same concentration of 0.03 wt% and deionized water. The CO 2 hydrate phase boundary and kinetic parameters of CO 2 hydrate formation including induction time, the initial rate and amount of gas consumed, gas uptake, storage capacity, and water to hydrates conversion are studied. The results show that the nanofluids studied do not affect the equilibrium conditions of CO 2 hydrates. In addition, 0.01 and 0.05 wt% of COOH-MWCNT mixed with 0.03 wt% SDS showed highest initial hydrate formation rate and gas uptake. Furthermore, a comparison between SDS and COOH-MWCNT (without stabilizer SDS) at 0.03 wt% revealed that addition of COOH-MWCNT to the water enhance the initial hydrates formation rate compared to SDS.