Additive promoted supported mixed amines on mesoporous silica for cyclic capture of carbon dioxide

Abstract

Blending two amines has recently been developed as an efficient strategy to improve the post-combustion CO₂ capture performance of amine-functionalized mesoporous materials. The mixed two amine species of polyethyleneimine (PEI) and diethanolamine (DEA) can help to overcome the problems of intrinsic large viscosity, easy aggregation and low amine efficiency of the polyamine. In this study, a novel additive promoted supported mixed amines on mesoporous silica were successfully synthesized via a facile and efficient wet impregnation route. The adsorption performance of PEI and DEA individually loaded onto Al-MCM-41 was tested at 75 °C in a flow of 60 vol% CO₂/40 vol% N₂, leading to the identification of an optimal mixed amine loading of 50 %. The supported mixed amines system was further evaluated based on amine efficiency, adsorption capacity, kinetics and stability. The optimal adsorbent loaded with 30 wt% PEI and 20 wt% DEA exhibits a maximum CO₂ uptake of 3.53 mmol/g at 75 °C and stable cyclic stability with an average 1.93 % decay per cycle, due to the synergistic effect of both amines. The DEA with hydroxyl groups was introduced into PEI and co-impregnated within mesoporous silica can overcome the poor mass transfer of PEI, the limited stability of DEA and low adsorption capacity of Al-MCM-41. The synergistic combination of PEI and DEA is able to provide abundant CO₂ affinity sites and create extra CO₂ transfer pathways for effectively reducing the internal CO₂ diffusion resistance, by which the diffusion limitation of CO₂ in the deeper PEI films can be alleviated due to the interactions between PEI and DEA. As a result, the final mixed amine-functionalized adsorbents have excellent cyclic CO₂ uptake capacity, rapid kinetics and stability. This approach holds significant promise for environmentally friendly, cost-efficient, and large-scale applications in CO₂ capture and separation.