Resumen de Methane storage on metal-organic frameworks
High surface area and high porosity metal-organic frameworks (MOF) are an attractive option to store methane at ambient temperature and low pressure (50 bar). More than 40 MOFs have been investigated for their methane storage ability. Like the Chahine rule for cryogenic hydrogen adsorption, it was found that for every 1000 m2 of specific surface area, one can expect 0.06 g/g of maximum methane excess adsorption. With few exceptions, this is largely independent of surface chemistry and geometry. This rule can be broken by materials with optimal pore sizes (∼7 Å) and materials with open metal sites. The thermodynamics of adsorption, as it pertains to applications of methane storage, are discussed. Pelletization of the benchmark MOF, Cu3btc2, was found to have little effect on the storage capacity of the adsorbent. However, when pilot-scale amounts of material were tested, pelletization improved thermal management and increased the permeability. Both were attributed to the extra free space around the pellets. Additionally, on the pilot scale, all MOFs showed improved permeability compared to the benchmark activated carbon.
