2010 Volume 51 Issue 4 Pages 727-734
As an active surface can be a nucleation site for some reactions, the possibility of iron and carbon acting as a catalyst for methane hydrate formation has been examined in the previous study. If iron oxide and carbon can be used as a catalyst, they would have a low environmental influence and a relatively low cost. It has previously been shown that carbon and iron oxide can be used as a catalyst under weak stirring conditions. In the present study, experiments involving intense stirring were conducted for the establishment of the basis for a high production system.
The proposed reaction model consisted of the mass transfers of CH4 in the liquid films both at the gas-liquid and the liquid-solid interfaces and the diffusion in liquid water, and a chemical reaction at the liquid-solid interface. The kinetic analysis was performed using the model and the following results were obtained.
The reaction was a mixed control between the mass transfer and the chemical reaction at 277 K, which was closed to the maximum temperature of methane hydrate formation thermodynamically. While in the lower temperature region lower than 275 K, the mass transfer including the diffusion of CH4 and the apparent mass transfers in the liquid films, ks′ was dominant.
The addition of catalysts (hematite, graphite and its mixture) had acceleration effects on hydrate formation, but to varying degrees. The catalyst “Mix” (mixture of hematite and graphite) had the largest effect on hydrate formation over the whole stirring range. From the results of kinetic analysis, the existence of catalyst had a relatively large influence on the chemical reaction of the formation of methane hydrate.