Surface tensions of aqueous solutions of lithium dodecyl sulfate, sodium oleate, and dodecylbenzene sulfonic acid in contact with methane under hydrate-forming conditions

This paper presents experimental surface tension data of separate aqueous solutions of lithium dodecyl sulfate, sodium oleate, and dodecylbenzene sulfonic acid, each in contact with methane at a pressure of 3.90 MPa or 4.00 MPa and a temperature of 275 K (i.e., a condition in which a clathrate hydrate of methane is thermodynamically stable). These data were obtained by use of the pendant drop method in the metastable absence of any hydrate in the experimental system (i.e., every measurement was accomplished during the induction time for the hydrate formation). The surfactant concentration ranged up to 5.0 g kg−1 for lithium dodecyl sulfate, 0.6 g kg−1 for sodium oleate, and 1.0 g kg−1 for dodecylbenzene sulfonic acid. Based on the obtained surface-tension versus surfactant-concentration data, we estimated the critical micelle concentrations for lithium dodecyl sulfate, sodium oleate and dodecylbenzene sulfonic acid to be about 3.2 g kg−1, 0.12 g kg−1 and 0.39 g kg−1, respectively.