Understanding CO₂ Capture in Amine-Functionalized MCM-41 by Molecular Simulation

Abstract

It has been demonstrated that merging the inherent sorptive behavior of amorphous silica with organic groups increases the adsorption capabilities of the solid silica. However, the underlying mechanism of the adsorption process in the functionalized materials is not fully understood, limiting the possibility of designing optimal adsorbent materials for different applications; hence, the availability of complementary methods to advance in this field is of great interest. Here we present results concerning the adsorption of CO2 in amine-functionalized silica materials, by Monte Carlo simulations, providing new insight into the capture mechanism. We propose a simulation methodology for the design of postsynthesis-functionalized silica materials in which realistic model adsorbents are generated using an energy bias selection scheme for the possible grafting sites. This methodology can be applied to different materials. In this work, we evaluate a model MCM-41 for CO2 adsorption using grand canonical Monte Carlo simulations, and compared the results with available experimental data. A new methodology is presented, which allows accounting for the chemisorbed CO2 on the adsorption isotherms. The results indicate that although chemisorption is an important part of this process at low pressures, physisorption also plays a significant role in the capture of CO2 in these materials. Functionalization increases the interactions of the CO2 molecules with the surface, whereas it decreases the available space for adsorption of CO2; the overall efficiency of the improved adsorption lies on the availability of adsorption space versus stronger interactions. In addition to the adsorption isotherms, we studied the configurations of the amine chains during the adsorption process for different degrees of functionalization as well as the effect of the concentration of grafted amines on the adsorption isotherm. The overall results show that molecular simulations serve as a guide to quantify the CO2 amount that can be easily sorbed for carbon capture applications, highlighting the importance of this approach.

A new sustainable route in supercritical CO2 to functionalize silica SBA-15 with 3-aminopropyltrimethoxysilane as material for carbon capture

“…The CO 2 adsorption in amine-functionalized silica materials has been studied by Monte Carlo simulations. These simulations indicate that CO 2 adsorption occurred on the surface at high pressure by displacing the functionalized chains [67,68].…”

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

“…The TraPPE potential 36 18 The parameters for the Lennard-Jones 12−6 and Coulumbic charges for the aminosilane chains were taken from our previous work, which described the methodology for the calculation of adsorption isotherms of aminofunctionalized silica materials. 32 The surface area, pore volume, and pore diameter were calculated by analyzing the N 2 isotherms for both the experimental and simulated materials for consistency and ease of comparison. Simulated CO 2 adsorption isotherms were generated considering chemisorption and physisorption at low CO 2 pressure and physisorption at all pressures.…”

Synthesis of Functionalized McM-41 Mesoporous Silica

“…These properties avail its extensive use in several areas of application (Taib et al, 2011). Studies on using mesoporous silica modified with amine groups as adsorbents in CO2 adsorption are quite extensive (Belmabkhout et al, 2010;Builes & Vega, 2012;Gholami et al, 2016;Klinthong et al, 2013;Liu et al, 2015;Wang et al, 2015). The various chemical ligands that are either organic or inorganic can be anchored on the surface of MCM-41.…”

“…There are studies that attract great interest regarding the application of the functionalized mesoporous materials by organic compounds. These include heavy metal removal from water, CO2 capturing, drug delivery system, and catalytic applications (Builes et al, 2012;Faghihian & Naghavi, 2014;Manzano et al, 2008;Rath et al, 2014;Wu et al, 2010). In the present study, the MCM-41 mesoporous silica was synthesized from sodium metasilicate pentahydrate, and then, modified using tri-methoxymethyl-silane (TMMS).…”