Enhanced Methane Delivery in MIL-101(Cr) by Means of Subambient Cooling

Adsorbed natural gas (ANG) technology is the use of highly porous materials to store natural gas at more reasonable pressures and temperatures compared with conventional liquefied or compressed natural gas storage. Many different porous materials have been considered for ANG; however, there is still lack of research on adsorption capabilities of these porous materials at subambient temperatures and their adsorption kinetics in order to explore alternative approaches to enhance methane delivery. Here, we present a study on the adsorption isotherms and kinetics of methane in MIL-101(Cr) over the temperature range from 263.15 to 453.15 K and the pressure range from 0.5 to 15.0 MPa. Based on the measured excess adsorption amount and the modified Sips model, the total adsorption amount and the corresponding isosteric heat of total adsorption were extracted. The study reveals that the delivery amount of methane charged at 263.15 K and discharged at 303.15 K can be enhanced by 38.3% as compared to that charged and discharged at the same temperature of 303.15 K. The rate of methane adsorption is found to be controlled by the diffusion process, and the methane diffusivity through MIL-101(Cr) is estimated by fitting the transient adsorption curves with the Crank model.