(262a) Effect Of Sds On Methane Hydrate Nucleation

Gas hydrates are crystalline compounds in which small molecules such as methane stabilizes the cavities formed by hydrogen-bonded water molecules. One volume of methane hydrates stores about 170 volumes (STP) of methane, which corresponds to about 25 % of the volumetric capacity of liquefied methane. The largest challenges in the practical application of hydrate storage are long induction time, slow growth rate, and entrapped water. Sodium dodecyl sulfate (SDS) was found to be the most effective additive for shortening induction time and accelerating growth rate. This paper investigates the role of SDS in hydrate nucleation under static conditions. The induction time of methane + propane hydrate nucleation at temperatures above the Krafft point was determined at various SDS concentrations. The induction time decreases as SDS concentrations increases and then levels off at 100 ppm at 285 K. The hydrate nucleation rate depends on SDS monomer concentration, and it less dependent on SDS micelle concentrations. The high nucleation rate in the presence of SDS is due to the hydrate-solution interfacial tension decreases after SDS adsorbs on the hydrate nuclei, reducing the energy barrier of hydrate nucleation.