Adsorption of CO2, CH4, and N2 on Ordered Mesoporous Carbon: Approach for Greenhouse Gases Capture and Biogas Upgrading

Separation of CO2 and N-2 from CH4 is significantly important in natural gas upgrading, and capture/removal of CO2, CH4 from air (N-2) is essential to greenhouse gas emission control. Adsorption equilibrium and kinetics of CO2, CH4, and N-2 on an ordered mesoporous carbon (OMC) sample were systematically investigated to evaluate its capability in the above two applications. The OMC was synthesized and characterized with TEM, TGA, small-angle XRD, and nitrogen adsorption/desorption measurements. Pure component adsorption isotherms of CO2, CH4, and N-2 were measured at 278, 298, and 318 K and pressures up to 100 kPa, and correlated with the Langmuir model. These data were used to estimate the separation selectivities for CO2/CH4, CH4/N-2, and CO2/N-2 binary mixtures at different compositions and pressures according to the ideal adsorbed solution theory (IAST) model. At 278 K and 100 kPa, the predicted selectivities for equimolar CO2/CH4, CH4/N-2, and CO2/N-2 are 3.4, 3.7, and 12.8, respectively; and the adsorption capacities for CH4 and CO2 are 1.3 and 3.0 mmol/g, respectively. This is the first report of a versatile mesoporous material that displays both high selectivities and large adsorption capacities for separating CO2/CH4, CH4/N-2, and CO2/N-2 mixtures.