Analysis of CO2 Adsorption in Amine-Functionalized Porous Silicas by Molecular Simulations

We present the results of a combined experimental-molecular simulations approach concerning the capacity for CO2 adsorption of aminosilica hybrid products synthesized using supercritical fluids. Two porous supports were examined for amine functionalization, an ordered mesoporous silica (MCM-41) and a disordered silica gel (SG40). The textural properties of the studied materials were analyzed by low-temperature N-2 adsorption-desorption isotherms and compared to those of molecular simulations using the grand canonical Monte Carlo simulation method. The CO2 adsorption capacity of these materials was evaluated by recording CO2 adsorption isotherms up to 100 kPa. Molecular simulations of the CO2 adsorption behavior of selected samples were performed to gain a fundamental understanding of the effect of functionalization. This study shows that in the functionalized materials, the distance between nitrogen atoms of the grafted amines is a critical factor for the occurrence of CO2 chemisorption, providing some insight into key parameters for designing adsorbent materials for CO2 capture and separation. The relationship between the adsorption results with N-2 and CO2 allow us to compare the potential applications of the materials in CO2 adsorption and separation processes. A correlation of the N-2 adsorption at a given pressure with the CO2 adsorption at a different pressure allowed the prediction of which materials will perform well for these processes. The hybrid products with high amine density have desirable features required for industrial sorbents, such as an enhanced CO2 adsorption capacity and selectivity.