Abstract
The CO2 adsorption capacity of different functionalized mesoporous silicas of the SBA-15 type was investigated and the influence of textural properties and the effect of the silicon source on the CO2 uptake studied. Several adsorbents based on SBA-15 were synthesized using sodium silicate as silicon source, replacing the commonly used tetraethyl orthosilicate (TEOS). Thus, we synthesized three couples of supports, two at room temperature (RT, RT-F), two hydrothermal (HT, HT-F) and two hydrothermal with addition of swelling agent (1,3,5-triisopropylbenzene) (TiPB, TiPB-F). Within each couple, one of the materials was synthesized with ammonium fluoride (NH4F). The supports were functionalized via grafting 3-aminopropyltriethoxysilane (APTES) and via impregnation with polyethylenimine ethylenediamine branched (PEI). The adsorption behavior of the pure materials was described well by the Langmuir model, whereas for the amine-silicas, a Dualsite Langmuir model was applied, which allowed us to qualify and quantify two different adsorption sites. Among the materials synthesized, only the SBA-15 synthesized at room temperatures (RT) improved its properties as an adsorbent with the addition of fluoride when the silicas were functionalized with APTES. The most promising result was the TiPB-F/50PEI silica which at 75 °C and 1 bar CO2 captured 2.21 mmol/g.
Highlights
Since the beginning of the industrialization era, the emissions of greenhouse gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFC), and sulfur hexafluoride (SF6) have been continuously increasing
room temperatures (RT), RT-F, HT and HT-F clearly show the (100)
Reflection to lower angles, which has been attributed to the incorporation of swelling agents such as alkanes or derived benzene compounds that penetrate into the hydrophobic core of the surfactant micelle of P-123, disrupting the honeycomb packing typical of the hydrothermal SBA-15, leading to node separation into spherical micelles [39,40]
Summary
Since the beginning of the industrialization era, the emissions of greenhouse gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbons (CFC), and sulfur hexafluoride (SF6) have been continuously increasing. The emissions of greenhouse gases cause the global warming, which is directly related with droughts, floods, heat waves, and destruction of ecosystems [2]. This fact has led to more restrictive environmental requirements by governments to reduce CO2 emissions to the atmosphere. Among the currently available technologies, post-combustion capture, a technology for capturing. Post-combustion capture uses wet/dry adsorbents, which are used for gas separation, and separates and collects CO2 by adsorption/desorption. Post-combustion capture technologies include wet absorption, dry adsorption, membrane-based technologies, and cryogenics [3,4]
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