Methane hydrate formation in the confined nanospace of activated carbons in seawater environment

Abstract

Methane hydrate formation studies in saline environment show that activated carbons are excellent host structures able to promote the water-to-hydrate conversion. Under confinement conditions, methane hydrate formation takes place at mild temperatures (−10 °C), low pressures (<6 MPa), with extremely fast kinetics (within minutes) and with a large adsorption capacity (up to 66 wt% CH4 for seawater, i.e. a 128% improvement compared to the dry carbon). Similar studies using ultrapure water give rise to a total methane adsorption capacity of 93 wt%, i.e. entropic effects exerted by salt play a crucial role in the methane hydrate nucleation and growth. Synthesized methane hydrates exhibit a sI crystal structure and a stoichiometry that mimics natural hydrates. These findings open the gate towards the application of activated carbons with a highly developed nanoporous network as host structure for offshore methane storage in marine reservoirs.