Isothermal versus Non-isothermal Adsorption−Desorption Cycling of Triamine-Grafted Pore-Expanded MCM-41 Mesoporous Silica for CO₂ Capture from Flue Gas

CO2 adsorption−desorption isotherms for triamine-grafted pore-expanded mesoporous silica (TRI-PE-MCM-41) were measured up to 25 bar using the same adsorption and pretreatment temperatures at 298, 323, and 343 K and compared to CO2 adsorption data for 13X zeolite, aminated metal organic framework (Zn-Atz MOF), and Darco activated carbon (Darco-AC). Cyclic isothermal adsorption−desorption measurements of pure CO2 and a 10:90 CO2/N2 mixture were carried out using vacuum swing (VS) and concentration swing (CS) regeneration modes at 298 and 343 K, in dry and humid conditions, and compared to cyclic non-isothermal desorption measurements, i.e., temperature swing (TS) and temperature-vacuum swing (TVS) regeneration operations. In addition to high CO2 selectivity, it was found that, in comparison to the three other adsorbents, TRI-PE-MCM-41 exhibited higher CO2 uptake in the presence of a 10:90 CO2/N2 mixture in both dry and humid conditions. Cyclic experiments using VS regeneration mode at 343 K gave a similar CO2 uptake as the TS regeneration mode. Similar to liquid-phase CO2 absorption, SO2 had a deleterious effect on CO2 adsorption.