CO2/CH4, CH4/H2 and CO2/CH4/H2 separations at high pressures using Mg2(dobdc)

High-pressure separations of binary and ternary mixtures of CO2, CH4, and H-2 are relevant to carbon dioxide capture as well as hydrogen and natural gas purification. Metal-organic frameworks represent a class of porous materials that could be used to accomplish these separations, and Mg-2(dobdc) (dobdc(4-) = 1,4-dioxido-2,5-benzenedicarboxylate), also sometimes referred to as Mg-MOF-74 or CPO-27-Mg, is an especially lightweight metal-organic framework with a high concentration of coordinatively-unsaturated metal sites decorating its interior surfaces. High pressure CH4 adsorption isotherms presented here, together with CO2 and H-2 adsorption behavior, are analyzed using the Ideal Adsorbed Solution Theory to model CO2/CH4, CH4/H-2, and CO2/CH4/H-2 mixture separations using Mg-2(dobdc). The selectivities, working capacities and breakthrough performances for these three mixtures are reported, and Mg-2(dobdc) is shown to outperform zeolite 13X in each scenario. (c) 2011 Elsevier Inc. All rights reserved.