Improved methane storage capacity of methane hydrate promoted by vesicles from carboxylate surfactants and quaternary ammonium

The maximum methane storage capacity (MSC) is of critical importance of methane hydrate to store methane. This paper reports the effects of vesicle solutions, formed through combination of carboxylate surfactants with cationic quaternary ammonium salt including hydroxypropyl trimethyl ammonium chloride chitosan (HACC) or dodecyl trimethyl ammonium chloride (DTAC), on the formation of methane hydrate. It was found that vesicles could raise the maximum MSC of hydrate by about 10 (V/V, the volume of methane stored by one volume of hydrate) at appropriate anion and cation concentrations. For example, at 800 ppm (parts per million) of sodium laurate (SL) and 600 ppm of HACC concentrations, the formed vesicles could elevate the maximum capacity to 151 V/V, 5.3% higher than that of sodium laurate alone. The vesicles formed could increase the maximum MSC, from 136 V/V to 147 V/V by sodium oleate (SO) and HACC, 145 V/V to 153 V/V by sodium decanoate (SD) and HACC and 137 V/V to 149 V/V by SO and DTAC. The reason for the enhancement is that the large hydrophobic space of the vesicles could solubilize methane molecules and facilitate them to contact with water molecules.