Inhibition effect of surfactants on CO ₂ enclathration with cyclopentane in an unstirred batch reactor

The effect of sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and fatty alcohol EO/PO derivative (LS54) on unsteady-state CO ₂ absorption in the metastable region of CO ₂ ydrates and CO ₂ enclathration with cyclopentane (CP) was investigated in an unstirred batch reactor. These surfactants have no measurable effect on the mass transfer of CO ₂ across the gas-liquid interface into water. However, they retard CO ₂ 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 CO ₂ and CP sequentially. Even though this layer cannot be macroscopically detected when swapping the order of CO ₂ and CP charge, the existence of this layer can be inferred from the unchanged pressure profile. This layer prevents CO ₂ from contacting with water and thus delays CO ₂ 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.