High Efficiency and Rapid Natural Gas Storage through Forming Hydrate in Water/Diesel Emulsions with the Promotion of Cyclopentylamine and Cyclopentanone

Water/diesel-cyclopentylamine and water/diesel-cyclopentanone emulsions were used to store natural gas during hydrate formation. First, cyclopentylamine (-amine) and cyclopentanone (-anone) were tested as thermodynamic promoters for CH4 hydrate formation in water/diesel (w/o) emulsions. The kinetics of CH4 hydrate formation in the w/o-amine and w/o-anone emulsions were then investigated. It was found that the promotional effect of both cyclopentylamine and cyclopentanone on CH4 storage in the hydrate phase was much better than that of cyclopentane, with the highest gas storage amount reaching 201.7 m3/m3, which is close to the ideal value (220 m3/m3), and the water-to-hydrate conversion ratio was higher than 90%. The main hydration reaction process was completed in 50 min, with the reaction rate reaching 2.3 mmol/min, which is higher than that reported for aqueous solutions. It should be noted that this was the first time that cyclopentylamine was tested and it showed good thermodynamic and kinetic stimulation effects on gas hydrate formation. The suitable CH4 hydrate formation conditions including the additional amount of promoters, temperature, pressure, and water cut range were determined to be approximately 20 wt %, 274.15–278.15 K, 5.0–6.0 MPa, and 20 wt %, respectively. The storage and transport pressure for the formed hydrate products could be decreased to less than 1 MPa. The significant gas storage amount was further supported by laser Raman analysis, which confirmed that the CH4 molecules were trapped in the small and large cages of the formed SII hydrate. Meanwhile, the formed hydrate/diesel slurries exhibited good dispersion features.