Effect of Immobilized Amines on the Sorption Properties of Solid Materials: Impregnation versus Grafting

Abstract

The underlying mechanism of the adsorption process in functionalized materials is not yet fully understood. This incomplete understanding limits the possibility of designing optimal adsorbent materials for different applications. Hence, the availability of complementary methods to advance this field is of great interest. We present here results concerning the adsorption of CO(2) in amine-functionalized silica materials by Monte Carlo simulations, providing new insights into the capture process. Two different mechanisms of functionalization are compared: impregnation (a physical mixture of the amine and the support) and grafting (a chemical bond is formed between the amine and the support). We evaluate in this work a model of MCM-41 for N(2) and CO(2) adsorption with varying degrees of density of the functionalized chains. The results indicate that the mobility of the impregnated chains allows the creation of a network of microcavities, which enhance the low-pressure adsorption capabilities of these materials. Molecular simulations allow us to study in detail the conformational changes in the functionalized chains during the adsorption process. Materials functionalized densely by grafting undergo a change in the preferential orientation of the chains, which allows the adsorption of additional molecules close to the surface of the support. The adsorption of gas molecules close to the pore surface is usually the most energetically favorable configuration; however, for densely grafted materials the adsorption close to the surface occurs only at pressures large enough to provide energy to displace the functionalized chains.

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

“…Previous works have shown that depending on the hybrid adsorbent synthesis route and on the porous support employed for functionalization, different effects on the CO 2 capture capabilities of the synthesized products can be attained. 5,24,30 Jones and co-workers 24 studied the isosteric heats of adsorption of silica-supported amine materials with varying amine densities. They showed that a large increase in the heat of adsorption occurs once the average spacing between the grafted ends of the functionalized chains reaches a value below 1.2 nm.…”

Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning

“…Nitrogen content was great for the adsorbents prepared from MF resin . And the presence of amino groups in the adsorbent was interesting for separation purposes because of the possibility of creating responsive charged surfaces with selective CO 2 binding properties . The amount of nitrogen content was an important index of measuring the potential adsorption performance of the material .…”