Enhanced growth of methane–propane clathrate hydrate crystals with sodium dodecyl sulfate, sodium tetradecyl sulfate, and sodium hexadecyl sulfate surfactants

Abstract

In the present study the effect of three commercially available anionic surfactants on the hydrate growth from a gas mixture of 90.5 mol% methane/9.5 mol% propane mixture was investigated. The surfactants used were sodium dodecyl sulfate (SDS), sodium tetradecyl sulfate (STS), and sodium hexadecyl sulfate (SHS). The morphology of the growing crystals and the gas consumption were observed during the experiments. The results showed that in the presence of surfactants, branches of porous fibre-like crystals were formed instead of dendritic crystals formed in the absence of any additive. In addition, extensive hydrate crystal growth on the crystallizer walls and a “mushy” hydrate layer instead of a thin crystal film appeared at the gas/water interface. Finally, the addition of SDS with concentration range between 242 and 2200 ppm (Δ T=13.1 K) was found to increase the mole consumption for hydrate formation by approximately 14 times compared to pure water. This increase is related to the change in hydrate morphology, whereby a more porous hydrate forms with enhanced water/gas contacts.