Evaluation of the thermal regeneration of an amine-grafted mesoporous silica used for CO 2 /N 2 separation

In view of the promising applicability of adsorption to the capture of CO 2 from post-combustion gases, the use of mesoporous silica functionalized with 3-aminopropyltriethoxysilane (APTES) was studied as adsorbent in a fixed bed for CO 2 –N 2 separation under thermal swings. Characterization of the adsorbent performed before and after functionalization indicated that amine grafting was successful. Additionally, CO 2 adsorption on a magnetic suspension balance showed a significant increase in uptake of the APTES-functionalized sample over the support, mainly at low relative pressures. Relatively high values of adsorption enthalpy suggest the occurrence of chemical adsorption attributed to CO 2 bonding with the amines. Breakthrough curves were measured for pure CO 2 , N 2 and the CO 2 /N 2 (15/75% v/v) mixture, which showed good agreement with respect to the uptake of the individual gases, as determined from gravimetric tests. Full CO 2 desorption from the bed required a temperature rise, which suggests that these materials may be suitable for TSA cyclic processes. A temperature of 90 °C was enough for a complete regeneration of the adsorbent during the desorption phase under dynamic conditions. The material showed very stable behavior after 20 successive cycles.