Experimental Investigation of CO2 Hydrate Formation in the Water Containing Graphite Nanoparticles and Tetra-n-butyl Ammonium Bromide

The effects of tetra-n-butyl ammonium bromide (TBAB) and graphite nanoparticles (GN) on phase equilibrium curves, gas consumption, induction time, and ratio of water to hydrate conversion were investigated in this work. Aqueous solutions of the mixture of TBAB and GN with three concentrations of 0.04%, 0.06%, 0.08%, and 0.1% were tested in a stirred reactor. The graphite nanoparticles with a concentration of 0.08% showed the highest hydrate formation rate, revealing that 0.08% is the optimal concentration for the hydrate formation in this, study. Comparing the induction time of the pure TBAB system with that of various concentrations of GN, a decrease by 16.6% of induction time at 0.08% GN concentration was observed, while the value decreased by 31.62% at a GN concentration of 0.1%. The final water to hydrate conversion reached the maximum value of 50.75% at a GN concentration of 0.08%. The concentration effect of graphite nanoparticles on the phase equilibrium curve in the presence of TBAB was also studied in this work. As reported, the concentration of graphite nanoparticles had little effect on the phase equilibrium of CO2 hydrate formation, while adding TBAB to nanofluids could greatly reduce the hydrate formation pressures.