Porous properties of carbon gel microspheres as adsorbents for gas separation

Carbon gel microspheres were synthesized by the inverse emulsion polymerization of resorcinol with formaldehyde, followed by drying and pyrolysis in an inert atmosphere. By using freeze-drying and hot air drying for the preparation of the precursors, carbon cryogel microspheres (CCM) and carbon xerogel microspheres (CXM) were respectively synthesized to study the influence of the drying method on the porous properties of CCM and CXM. The mesoporosity of CCM was higher than that of CXM because freeze-drying was effective to prevent the shrinkage of mesopores in the precursors during drying. On the other hand, the microporosity of the carbon gel microspheres was hardly influenced by the drying method. It was revealed that the amount of nitrogen or oxygen adsorbed on CCM and CXM at 298 K was almost equivalent since they possess almost the same microporosity. Both CCM and CXM, which were found to have ultramicroporous surfaces, were confirmed to be applicable to adsorbents for separation of air by pressure swing adsorption (PSA), since the adsorption rate of nitrogen was much larger than that of oxygen. Furthermore, CCM and CXM were found to show similar adsorption characteristics as adsorbents for temperature swing adsorption (TSA).