The role of sodium dodecyl sulfate (SDS) in methane hydrate formation is investigated in a nonstirred batch reactor. Addition of SDS reduces the induction time, but no systematic trend is observed between induction times and SDS concentrations. The hydrate growth is analyzed by using a diffusion-reaction kinetics model with an assumption that crystallization occurs only in the liquid film at the gas-liquid interface. At the start of hydrate growth, the apparent rate constant increases linearly with increasing aqueous SDS concentrations. The apparent rate constant during hydrate growth increases as more available gas-liquid interface is generated. SDS not only increases hydrate nucleation rate by reducing the interfacial tension between hydrate and liquid but also accelerates hydrate growth rate by increasing the total surface area of hydrate particles and the gas-liquid interfacial area.

Cyclopentane (CP) forms sII hydrates, in which CP only occupies the large cavities. Small gas molecules such as hydrogen and carbon dioxide can be encaged in the small cavities. However, there are no reported data on the equilibrium conditions of CP + H 2 and CP + CO 2 binary hydrates, which are essential to developing CO 2 capturing or H 2 enriching processes. In this study, the dissociation temperature of CP + H 2 hydrate pressures ranging from (2.7 to 11.1) MPa and CP + CO 2 hydrates at pressures of (0.89 to 3.51) MPa was measured by using a high-pressure MicroDSC.

Understanding the interaction between sodium dodecyl sulfate (SDS) and gas hydrates provides insight into the role of SDS in promoting gas hydrate formation. The aim of this study was to investigate the relationship between tetrahydrofuran (THF) hydrate induction and SDS adsorption at the hydrate/liquid interface. The adsorption behavior was studied by ζ-potential and pyrene fluorescence measurements. The negative charge of the hydrate particles remains constant at SDS concentrations of 0 to 0.17 mM. The ζ-potential becomes more negative as the SDS concentration increases from 0.17 to 3.4 mM. The micropolarity of the THF hydrate/ liquid interface decreases with increasing SDS concentrations, and then it remains almost unchanged at SDS concentrations above 0.17 mM. A monolayer of DSis completed at a SDS concentration of 0.17 mM. The reduction of induction time in the presence of SDS levels off at a SDS concentration of 0.17 mM. This provides strong evidence that the short induction is due to the adsorption of DSat the hydrate/liquid interface. The adsorption study of SDS on THF hydrates can be extended to other systems and we may screen suitable surfactants for accelerating or retarding gas hydrate formation.