The possibility of storing large amounts of natural gas within wet active carbons is examined.The sorption isotherms of methane at 2 deg C and up to 8 MPa are built for four carbonaceous materials.Three of them originate from the same precursor(coconut shell),are physically activated at various burn-offs and are mainly microporous.The fourth material is a highly mesoporous chemically activated pinewood carbon.These adsorbents are wetted with a constant weight ratio water/carbon close to 1.The resulting isotherms all exhibit a marked step occurring near the expected formation pressure of methane hydrates,thus supporting their occurrence within the porous materials.The amount of gas stored at the highest pressures investigated then ranges from 6 to 17 mol/ kg of wet adsorbent(i.e.,corresponding to 10-36 mol/kg of dry carbon),depending on the material.The results are discussed on the basis of the known pore texture of each adsorbent,and stoichiometries of the formed hydrates are calculated.Considerations about adsorption/desorption kinetics and metastability are also developed.
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