Epoxide functionalization of a pentaethylenehexamine adsorbent supported on macroporous silica for post-combustion CO₂ capture

N-functionalized solid adsorbents have been studied for post-combustion CO₂ capture. Most studies have focused only on the adsorption condition of the adsorbents. Few studies have focused on the regeneration condition of adsorbents. Regeneration is required under the condition of 100 % CO₂ for high-purity CO₂ separation. Regeneration under inert conditions such as N₂ or He, not under the condition of 100 % CO₂ regeneration are required additional cost for high-purity CO₂ separation. In this study, a macroporous silica (MPS) support, which combined a high surface area, large porosity and large pore volume, was selected as the support to achieve high CO₂ capture performance. Pentaethylenehexamine (PEHA) was selected because of its high amine content, high adsorption capacity, high thermal stability, and low cost. The epoxide functionalization of PEHA was used to suppress the urea formation under regeneration conditions. The working capacity and cyclic stability of epoxide functionalization of MPS-based PEHA adsorbents were investigated. A working capacity of 1.8 mmol g⁻¹ was maintained by repeating adsorption and desorption experiments 20 times under an adsorption condition of 15 % CO₂ and a desorption condition of 100 % CO₂. Additionally, the stability of the adsorbent under a 100 % CO₂ regeneration condition was confirmed by maintaining the working capacity constant during 20 repeated adsorption and desorption cycle experiments. When the adsorption time was reduced to minimize H₂O adsorption, the regeneration heat of the adsorbent was 2.86 GJ tCO₂^-1. These results demonstrated that the regeneration ability was excellent under the condition of 100 % CO₂, which is the actual process application condition. This approach is promising for industrial applications of CO₂ capture technology.