CO₂ adsorption performance of amino-functionalized SBA-15 under post-combustion conditions

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 PEI-impregnated solids and moderately decreases for TEPA-impregnated adsorbent. CO2 adsorption capacity decreased significantly with the presence of 1000 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 degrees C and 1 bar. (C) 2013 Published by Elsevier B.V.