Inhibition Effect of Surfactants on CO2 Enclathration with Cyclopentane in an Unstirred Batch Reactor

Abstract

The effect of sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and fatty alcohol EO/PO derivative (LS54) on unsteady-state CO2 absorption in the metastable region Of CO2 hydrates and CO2 enclathration with cyclopentane (CP) was investigated in an unstirred batch reactor. These surfactants have no measurable effect on the mass transfer of CO2 across the gas-liquid interface into water. However, they retard CO2 enclathration, and this inhibition effect becomes significant at 200 ppm of SDS and 100 ppm of LS54 or CTAB. A layer of clathrate hydrates is visually observed if charging CO2 and CP sequentially. Even though this layer cannot be macroscopically detected when swapping the order of CO2 and CP charge, the existence of this layer can be inferred from the unchanged pressure profile. This layer prevents CO2 from contacting with water and thus delays CO2 enclathration. The habit of clathrate hydrates growing along the reactor wall without agitation is discussed based on the magnitude of temperature spikes at the initial stage of the enclathration.