Adsorption and Separation of CO2/CH4 on Amorphous Silica Molecular Sieve

Adsorption and separation of CO2/CH4 were examined on two kinds of amorphous silica molecular sieves, ASMS-3A and ASMS-SA, that are composed of spherical cavities arranged in a face-centered-cubic array and connected through narrow necks of molecular dimensions. For ASMS-3A, the exclusion of CH4 molecules due to their dimensions into the narrow necks and preferential adsorption of CO2 with the smaller kinetic diameter is observed at 283 K. In addition, the amount of CO2 adsorbed at 283 K does not decrease at all with surface hydration. All these results suggest that ASMS-3A is a promising candidate for the separation and purification of CO2 from various CO2/CH4 mixtures such as natural gas and landfill gas by a PSA process.