CO2 capture using triamine- grafted SBA-15: The impact of the support pore structure

The impact of the support pore structure on the CO2 adsorption performance of triamine-tethered SBA-15 silica was studied. Six SBA-15 silica supports with different pore sizes and intrawall pore volumes were synthesized, followed by triamine functionalization through dry and wet grafting (i.e., with and without added water). CO2 adsorption measurements showed the positive impact of support large pore size and high intrawall pore volume on adsorptive properties, with the former being dominant. Large-pore supports exhibited the highest surface density of amine groups (up to 35 mu mol/m(2)), highest CO2 uptakes (up to 1.88 mmol CO2/g) and CO2/N ratios (up to 0.33 mol CO2/mol N), and fastest adsorption kinetics. When the intrawall pore volume decreased by 53% for samples with identical pore sizes, lower CO2 uptakes (up to 63%) and CO2/N ratios (up to 62%), and slower adsorption kinetics were observed, particularly for the lowest adsorption temperature (i.e., 25 degrees C). It was inferred that large pore size and/or high intrawall pore volume of the support improve the adsorptive properties via enhanced amine accessibility. Large-pore supports also allowed higher surface amine density to be achieved because of reduced steric hindrance between grafted triamine species.