Combined effects of surface tension and thermal conductivity on the methane hydrate formation in the presence of both nanoparticles and surfactant

Abstract

Hydrate has been considered as a promising and cost-effective route for massive storage of natural gas. However, the main problem for this technique to be commercially available is its poor chemical kinetics. In the present study, aiming to reveal the underlying mechanism dominating the hydrate formation kinetics, we investigated combined effects of surface tension and thermal conductivity on the methane hydrate formation. The induction time, gas uptake, and storage capacity for hydrate formation was investigated in detail in the presence of TiO2 nanoparticles and SDS surfactant. The optimal condition for methane hydrate growth was found to be 500 ppm SDS in the presence of 1.0 wt% TiO2 nanoparticles. In this case, the induction time significantly reduced from 183 to 14 min compared to that in pure water. With the addition of SDS alone the surface tension decreased from 72.4 mN/m for pure water to 38.4 mN/m which further decreased to 33.8mN/m, when 1.0% TiO2 was added into the SDS solution. On the other hand, the thermal conductivity of solution showed a continuous increase with the increasing addition of TiO2 while there was an optimal thermal conductivity value for the hydrate growth. It turns out that the optimal addition of TiO2 in SDS solution can result in the lowest surface tension and suitable thermal conductivity, which, in turn, leads to the favorable environment for methane hydrate growth. Our results are supposed to be valuable for the precise control of methane hydrate growth kinetics.