Amine-impregnated as-synthesized silicas for CO2 capture: Experimental study and mechanism analysis

Abstract

Porous silicas have been extensively investigated as amine carriers for the production of CO2 adsorbents, while few studies demonstrated that as-synthesized silicas (without template removal) can also serve as good amine carriers for efficient CO2 capture. This raises a fundamental question of whether the time-consuming and energy-intensive process of removing the template from as-synthesized silicas is still necessary. More importantly, a reasonable mechanism is quite needed to explain the as-synthesized silicas as effective amine carriers. To this end, in this study, four types of as-synthesized silicas were compared together with their corresponding porous silicas as amine carriers for CO2 capture. Experimental results show that as-synthesized silicas exhibit comparable or even better performance at medium amine loadings (50 ∼ 60 wt%), including larger CO2 adsorption capacities and better cyclic stability, while porous silicas predominate at high amine loadings (70 wt%). Molecular simulation results indicate that the amine species are located in the interparticle cavities in the silicas rather than in the structural pores. This work provides important guidance for the future design of practical solid-amine CO2 adsorbents.