Effects of Composite Accelerators on the Formation of Carbon Dioxide Hydrates

To improve the rate of formation of carbon dioxide hydrates, tetra-n-butylammonium bromide (TBAB) was compounded with different concentrations of sodium dodecyl sulfate (SDS) and nanographite, and the effects of these mixtures on carbon dioxide hydrate formation were studied. The addition of TBAB alone, as well as mixtures of TBAB and SDS or nanographite, shortened the induced nucleation time, and the induction times of the TBAB-2.5 g/L nanographite and TBAB-0.24 g/L SDS systems were the shortest and longest, respectively. Further, on mixing TBAB and SDS, the induced nucleation time first increased and then decreased with the increase in the SDS concentration. When TBAB and nanographite were mixed together, the induced nucleation time first decreased, then increased, and again decreased with the increase in the nanographite concentration. In addition, the hydrate formation rate and conversion were highest for the TBAB-0.48 g/L SDS system and lowest for the TBAB-0.06 g/L SDS system; in the first 35 min, from the end of gas charging, the TBAB-10 g/L nanographite and TBAB-5 g/L nanographite systems yielded the highest and lowest hydrate formation rates and conversions, respectively. For the composite systems, obvious effects were observed in the initial stages of reaction, but the effects varied over the course of the reaction. Overall, the use of different accelerators resulted in little differences in the total production, conversion, and formation rate of carbon dioxide hydrates over the course of the reaction.