Optimal wetting of active carbons for methane hydrate formation

In a recent paper (Perrin A, Celzard A, Marêché JF, Furdin G. Methane storage within dry and wet active carbons: a comparative study. Energy and Fuels 2003;17(5):1283–1291), methane storage by formation of methane hydrates within wet commercial active carbons (wetting ratio R=mass ratio water/carbon≈1) was investigated at 2 °C and up to 8 MPa. It was suspected from this study that more methane hydrate could be formed if more water was added. The present article is the continuation of this former work, and the pore volumes of the same materials were now saturated by water and investigated in the same T–P conditions. It is shown that, doing this, hydrate formation occurs at the lowest possible pressures (i.e. corresponding to those observed in bulk water) but poor results in terms of stored amounts are obtained. An optimal wetting ratio leading to the highest stored amounts was evidenced and found to be close to 1 whatever the pore texture of the carbon materials. Additionally, saturating the pore space with water further slows down the formation kinetics, which were already very long at R≈1. Finally, the role of an additive like sodium dodecyl sulphate (SDS) was investigated in one carbon; it is found that hydrates are formed at a rather low methane pressure, but the final amount stored is not higher than that previously obtained without adding SDS.