One-Step Process\nUsing CO₂ for the Preparation\nof Amino-Functionalized Mesoporous Silica for CO₂ Capture\nApplication

Abstract

In this study, a\nnovel and facile one-step method using CO₂ for the preparation\nof amino-functionalized mesoporous silica\nfor CO₂ capture application was introduced. 3-Aminopropyltriethoxysilane\n(APTES, 30 wt % in water) was first bubbled with CO₂ and\nthen mixed with sodium silicate to produce amino-functionalized mesoporous\nsilica. Three adsorbents, namely, precipitated silica adsorbent (PSA),\nsilicagel adsorbent (SGA), and condense silicagel adsorbent (C-SGA),\nwere synthesized by tuning CO₂ pressure when preparing\nCO₂ absorbed APTES solution and aging temperatures of obtained\nhydrogel, respectively. PSA has large primary particles (200–1000\nnm) with 73.4 m²/g in surface area and 0.1 cm³/g in pore volume. SGA has smaller silica primary particles (10–20\nnm) with higher surface area (205.9 m²/g) and higher pore\nvolume (0.70 cm³/g). When PSA and SGA hydrogels were aged\nat 110 °C, they transformed to a condensed silicagel adsorbent\n(C-SGA) with very low surface area (12.0 m²/g) and pore\nvolume (0.05 cm³/g). The existence of amino-functional\ngroups in the adsorbents was confirmed by Fourier transform infrared\nspectroscopy technique and energy dispersive spectroscopy coupled\nwith a scanning electron microscope. PSA had the highest CO₂ loading with 45.1 mg/g at the adsorption temperature of 50 °C,\nand CO₂ loading decreased with the increase in adsorption\ntemperature. This adsorbent has low CO₂ adsorption heat\n(66 kJ/mol) and heat capacity (1.25 kJ/kg °C) and is thermally\nstable, indicating that it could be suitable for CO₂ capture\napplication. The success of the proposed one-step process does not\nonly provide a facile method to synthesize solid adsorbent for CO₂ capture but also contributes an additional option to CO₂ utilization.