Pure and Binary Adsorption of Methane and Nitrogen by Silicalite

Methane is the most important non-CO2 greenhouse gas (GHG) responsible for global warming with more than 10% of total GHG emissions. The greenhouse warming potential (GWP) of this gas is much higher than carbon dioxide. Therefore, any reduction in methane emissions is really important in atmosphere reconstruction. Nitrogen is needed to be removed from landfill gas to obtain low grade natural gas as a renewable source of energy from garbage, but the separation is really difficult. Adsorption was considered as a possibility for this separation, and silicalite was studied as the adsorbent. The adsorption behavior of methane and nitrogen with this adsorbent was studied by concentration pulse chromatography and constant volume techniques. Ideal separation factors were obtained from the experimental pure adsorption isotherms by using the temperature independent Toth isotherm model. Mixture adsorption isotherms for the binary system of methane and nitrogen at (40, 70, and 100)degrees C at 1 bar total pressure were determined experimentally. Corresponding x-y diagrams and separation factors were obtained from these data. The thermodynamic consistency tests between pure and binary gas adsorption systems were also carried out. The separation factors obtained with silicalite for the separation applications of methane and nitrogen gases in this work are much better than those obtained for other systems in the literature.