CO2 adsorption performance of aminofunctionalized SBA-15 under post-combustion conditions

Abstract

Carbon dioxide adsorbents prepared from SBA-15 mesostructured silica functionalized with amino groups have been tested under a simulated gas mixture similar to that of a coal-fired thermal power plant. SBA-15 material was functionalized by grafting with aminopropyl-trimethoxysilane (AP (N)) and diethylene-triamine-trimethoxysilane (DT (NNN)), and by impregnation with polyethyleneimine (PEI) and tetraethylenepentamine (TEPA). CO2 adsorption performance was measured in both a thermobalance and in a fixed bed. A thorough study of the adsorption behaviour was carried out, including the influence of conditions found in real post-combustion operation processes, such as diluted CO2 concentration, presence of SO2 and moisture in the flue gas. The reutilization of the adsorbent by successive adsorption-desorption experiments has also been tested. Grafted materials and samples impregnated with around 50 % organic amount or higher, showed a small influence of the dilution of CO2 in the feed gas on their CO2 uptake. Adsorption capacity after 10 cycles remains almost unaltered for grafted and PEIimpregnated solids and moderately decreases for TEPA-impregnated adsorbent. CO2 adsorption capacity decreased significantly with the presence of 1,000 ppm SO2 for up to 5 cycles, finding a direct correlation with the nitrogen content of the sorbents. Humid conditions (5 % moisture) do not significantly affect adsorption capacity of grafted samples, but improve the CO2 uptake of impregnated adsorbents about 50-60 %, obtaining an adsorption capacity of 16.2 wt. % CO2 (3.7 mmol CO2/g) for sample SBA-TEPA (50) in a humid diluted CO2 stream (15 % CO2) at 45 ºC and 1 bar.