Mechanism of the dissolution of methane in the complex micellar system of NaOA/cyclohexane

The surfactant sodium oleate (NaOA) has important applications in dissolving methane, but there is insufficient research regarding the dissolution mechanism of methane in compound solutions of NaOA. Cyclohexane can also be used as a reagent to dissolve methane because of the similar phase dissolution principles. Thus, surfactant NaOA and the compounding reagent cyclohexane are selected as the experimental subjects of this study. In this study, the optimum ratio of NaOA to cyclohexane and the dissolution mechanism of methane in the mixed solution are microscopically determined by measuring the amount of methane dissolution, critical micelle concentration, particle size, and micelle morphology in the mixed solutions. Compared with the single NaOA solution, the mixed solutions of NaOA and cyclohexane have lower critical concentrations of micelles, more concentrated micelle particle size distributions, and more extended and aggregated micelle morphologies, all of which lead to higher methane solubilities in the mixed solutions. The optimum NaOA to cyclohexane ratio for dissolving methane is 1:3. The NaOA to cyclohexane concentration ratio of 1:3 demonstrates the lowest critical micelle concentration, which is most likely to generate micelles with a hydrophobic environment favorable for the dissolution of methane. The mixed solution at this ratio also demonstrates the most suitable particle size distribution and micelle morphology for the retention of methane in the core of the micelle.