Amine functionalized hierarchical bimodal mesoporous silicas as a promising nanocomposite for highly efficient CO2 capture

Abstract

Amine loaded solid adsorbents are promising for the post-combustion CO2 capture. A current challenge is how to synthesize support with excellent pore structure by cost-effective methods as supports for amine loading. Herein, hierarchical bimodal mesoporous silica (HMS) was synthesized by using P123 as template through the partitioned cooperative self-assembly process. The prepared HMS is found to have large pore volumes and hierarchical pore networks. Subsequently, a series of tetraethylenepent amine (TEPA) functionalized adsorbents is prepared and CO2 capture measurements were implemented in a fixed-bed reactor to investigate the effects of TEPA loading and mesoporous structure. And the influence of CO2 concentration on capture performance was also studied in both In-situ DRIFTS and adsorption kinetic ways. The results show that the CO2 capture amount of HMS is up to 5.82 mmol/g at 70 wt.% TEPA loading and 75 ℃ with 15 vol% CO2. The large pore volumes significantly increase the amine loading and the interconnected hierarchical mesopores networks facilitated the dispersion of amine. The higher CO2 concentrations is conducive to the formation of carbamic acid and the decrease of CO2 adsorption activation energy, thereby facilitating the CO2 adsorption. In addition, poly (propylene glycol) bis (2-aminopropyl ether) (PEA) was also introduced in the adsorbent to further improve the adsorption performance. The results show that the introduction of PEA can offer increased CO2 capture amount, improved thermal stability and regenerability due to the participation of the ether group in the reaction of CO2 with the amine group and improved the thermal stability of the TEPA and PEA co- functionalized adsorbent.