Influence Of Surface Wettability On Methane Hydrate Formation In Hydrophilic And Hydrophobic Mesoporous Silicas

The methane hydrate (MH) formation process in confinement was investigated using high-pressure methane sorption experiments on two wet materials with similar pore size distributions, B - PMO (hydrophobic) and MCM - 41 (hydrophilic). Their methane sorption isotherms possess two discrete methane gas consumption steps at similar to 10 bar and similar to 30 bar at 243 K. A systematic analysis reveals that external water and the so-called 'core water' inside the pore is rapidly consumed in the first step to form bulk-like hydrate, whereas adsorbed water is slowly consumed in the second step to form less stable confined hydrates at higher pressures. Synchrotron powder XRay results confirm methane hydrate structure I and reveal that bulk ice is swiftly and fully converted to hydrate in MCM - 41, whereas inactive bulk ice co-exists with MH in B - PMO at 6 MPa demonstrating the huge impact of the surface wettability on the water's behavior during MH formation.