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

Abstract

We present the results of a combined experimental−molecular simulations approach concerning the capacity for CO 2 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 CO 2 adsorption capacity of these materials was evaluated by recording CO 2 adsorption isotherms up to 100 kPa. Molecular simulations of the CO 2 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 CO 2 chemisorption, providing some insight into key parameters for designing adsorbent materials for CO 2 capture and separation. The relationship between the adsorption results with N 2 and CO 2 allow us to compare the potential applications of the materials in CO 2 adsorption and separation processes. A correlation of the N 2 adsorption at a given pressure with the CO 2 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 CO 2 adsorption capacity and selectivity.

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“…advantages such as (i) high CO 2 capture capacity, (ii) low energy requirement of adsorbent regeneration, (iii) adsorbent stability, (iv) fast kinetics, (v) easy handling, and (vi) efficiency under flue gas moisture [10,11]. On the atomic scale, polarizability or the quadrupole moment of the adsorbent functional site plays a significant role in the selective capture of CO 2 during physisorption [12,13]. However, for chemisorptive adsorption, selectivity is obtained based on chemical interactions between individual components of the gas mixture and surface functionalities of the adsorbent [14].…”

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