Surfactant effects on SF6 hydrate formation

Sulfur hexafluoride (SF6) has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate or collect it from waste gas streams. One separation method is through hydrate crystal formation. In this study, SF6 hydrate was formed in aqueous surfactant solutions of 0.00, 0.01, 0.05, 0.15 and 0.20 wt% to investigate the effects of surfactants on the hydrate formation rates. Three surfactants, Tween 20 (Tween), sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS), were tested in a semi-batch stirred vessel at the constant temperature and pressures of 276.2 K and 0.78 MPa, respectively. All surfactants showed kinetic promoter behavior for SF6 hydrate formation. It was also found that SF6 hydrate formation proceeded in two stages with the second stage being the most rapid. In situ Raman spectroscopy analysis revealed that the increased gas consumption rate with the addition of surfactant was possibly due to the increased gas filling rate in the hydrate cavity.

The SF same vibration mode before and after the inflection point indicted that the significantly increased gas consumption rate in the 2nd stage was not due to the structural change. Figure: Raman spectra of symmetric SF stretching vibration mode of SF6 hydrate with 0.1 wt% SDS.Figure optionsDownload as PowerPoint slide