Nanostructured silica as a support for regenerable high-capacity organoamine-based CO2 sorbents

Nanostructured precipitated and fumed silica (nanosilica) were found to be superior supports for the immobilization of various organoamines. The easily prepared solids were found to be regenerable and effective CO2 absorbents at moderate temperatures from room temperature up to 100 degrees C. Supported polyethylenimines (PEIs), especially branched low-molecular-weight (LMW, M-w ca. 800) and high-molecular-weight (HMW, Mw ca. 25 000) PEIs were particularly suitable as CO2 absorbents. Amines with lower molecular weights and lower boiling points such as pentaethylenehexamine (PEH), tetraethylenepentamine (TEP), monoethanolamine (MEA) and diethanolamine (DEA) showed sorbent leaching from the solid absorbents. The addition of poly(ethylene glycol) was found to significantly enhance the subsequently needed desorption of CO2 from PEI-based solid absorbents. In the preparation of CO2 absorbents, the particle size of the nanosilica was found to be of advantage compared to other solid supports having similar or higher surface area but larger particle size.