Sílica mesoporosa funcionalizada com APTES para captura de CO2 em cenários de pós-combustão: um estudo em leito fixo

Abstract

In view of the promising applicability of adsorption to the capture of CO2 from post-combustion gases, the use of silica SBA-15 functionalized with 3-aminopropyltriethoxysilane (APTES) was studied as adsorbent in gas separation CO2-N2 (binary system most representative of the post-combustion gases) in a fixed bed. Characterization of the solid was performed before and after the functionalization was carried out, which confirmed the anchoring of the amine molecules in the porous matrix. Additionally, a comparative test of CO2 adsorption on a magnetic suspension balance showed a significant advantage of the APTES-functionalized sample over the support, mainly at low relative pressures. The high adsorption heats obtained in the calorimetric tests suggest the existence of a chemical adsorption phenomenon attributed to CO2 bonding with the amines, even though the gravimetric equilibrium tests showed that an increase in temperature leads to a decrease in the adsorption capacity, a typical behavior of purely physical adsorption. The fixed-bed dynamic tests allowed for a study of the material from the breakthrough curves. The gas concentration profile data obtained showed good agreement with the gravimetric tests. The full regeneration of the adsorbent could not be carried out only with inert gas flow, it required a temperature rise to reverse the interactions of the CO2 with the solid. Although it represents an additional energy expenditure in the regeneration stage, the material showed very stable behavior when submitted to successive cycles, maintaining its adsorption capacity and selectivity.