Does SDS micellize under methane hydrate-forming conditions below the normal Krafft point?

Sodium dodecyl sulfate (SDS) can accelerate nucleation and growth of gas hydrates in a quiescent system. The objective of this paper is to investigate whether or not SDS micelles form in the meta-stable region of methane hydrates by the direct measurement of aqueous SDS concentration. The SDS solubility in water with high-pressure methane is identical to that under atmospheric pressure at a temperature range of 270–282 K; thus, the Krafft point under these methane hydrate-forming conditions does not shift from the normal Krafft point (281–289 K) under atmospheric pressure. The mole fraction of methane in SDS solution is independent of aqueous SDS concentration at a hydrate-forming condition. These results suggest that at temperatures below the normal Krafft point, no SDS micelles are present in the aqueous phase even in a high-pressure methane environment.

Graphical abstractAqueous SDS concentrations at 275 K and under two methane pressures (left) and SDS solubility in liquid water near methane hydrate-forming conditions (the Pexp/PdissPexp/Pdiss ratio ranges from 1.0 to 1.7) and under atmospheric pressure (right).Figure optionsDownload full-size imageDownload as PowerPoint slide