Hybrid Composites for CO2 Adsorption

Novel hybrid CO2 adsorbents, in forms of monoliths as needed for application in real processes, have been prepared using a robust and facile multiphase reaction–crystallization hydrothermal process, tuned to favor geopolymerization and in situ NaX zeolite gel conversion of metakaolin. The combination of raw materials and thermal treatments has affected the textural properties of the adsorbents, mainly in terms of different contribution of ultramicroporosity (< 7 Å) and supermicroporosity (7–20 Å) and microporous specific surface areas, ranging between 693 and 735 m2 g−1. The only crystalline phases produced have been NaX zeolite. Several CO2 adsorption/desorption cycles at room temperature (298 K) up to 15 bar were carried out on all the prepared adsorbents. The adsorbents showed an excellent CO2 storage capacity, higher than 20 wt%, and reversibility. The cyclability of the foamed adsorbent resulted positively affected by the textural features of the samples. Notably, the supermicroporosity, mesoporosity and macroporosity obtained in the foamed adsorbent limited to only 1 wt% loss of its adsorption capacity after three cycles.