Surfactant dry solution (DS) was prepared by mixing sodium dodecyl sulfate (SDS) solution, hydrophobic silica nanoparticles and air in a high speed blender. Flour-like SDS-DS combines the advantages of dispersed dry water and active SDS solution. Methane storage in clathrate hydrates using SDS-DS was investigated in a stainless steel vessel without stirring under the condition of 5.0 MPa and 273.2 K. The results demonstrated that highly dispersed SDS-DS could significantly enhance formation kinetics and storage capacity of methane hydrate. SDS-DS exhibited about the same methane storage capacity (172.96 m 3 •m-3) as dry water, but faster storage rates than dry water. Compared to SDS solution, SDS-DS had similar storage rates (7.44 m 3 •m-3 •min-1) and higher methane storage capacity under the relative low pressure. However, the aggregation of partial SDS-DS powders destroyed its original dispersive property after hydrate dissociation.

In this paper, hydrate phase equilibrium data for the CO2/CH4 + water system, CO2/CH4 + tetrabutylammonium bromide (TBAB) + water system, CO2/CH4 + tetrabutylammonium chloride (TBAC) + water system, and CO2/CH4 + tetrabutylammonium fluoride (TBAF) + water system were measured at temperatures from 280.2 K to 291.3 K and pressures from 0.61 MPa to 9.45 MPa with the 2.93·10–3 mole fraction of tetrabutylammonium halide. The equilibrium hydrate formation conditions were measured by an isochoric pressure-search method. The mole fractions of the mixture gas used in this work were 0.33 CO2 and 0.67 CH4. The experimental data for the CH4 + water system were contrasted with the published equilibrium data in the literature. Both have a good consistency, which demonstrates that the experimental method and the apparatus used in this paper are feasible and reliable. The experiment results show that the hydrate stable region was enlarged by adding TBAB, TBAC, or TBAF. Among the three additives, TBAF is the best and the enlarged extent order of three additives is TBAF > TBAC > TBAB. The three-phase equilibrium pressure of the CO2/CH4 + TBAF + water system is 0.61 MPa at 284.2 K.

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