Catalytic Capture of CO₂with Template-Containing Zn/MCM-41 and Its Transformation to Solid Carbonate

Abstract

Mesoporous MCM-41 materials modified by zinc have been prepared by non hydrothermal procedure. Zinc has been introduced by the direct synthesis (DS), template ion-exchange (TIE) and wet impregnation (WI) methods. The catalysts were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy-scanning electron microscopy (EDX-SEM), thermogravimetric and differential thermal analyses (TGA-DTA), Fourier transform infrared spectroscopy (FTIR) and N 2 adsorption/desorption measurements. The obtained catalysts were investigated for hydration of CO 2 and its precipitation as CaCO 3 at room temperature. We investigated the effect of synthesis method and cationic template on catalytic activity of Zn/MCM-41 catalysts. The results showed that template containing Zn/MCM-41 prepared by template ion exchange technique has high CO 2 hydration activity. This high activity is due to the presence of strong basic sites. It was also found that this catalyst can be easily recovered from the reaction mixture and reused without activation.Keywords: Zn/MCM-41, template, CO 2 capture, CaCO 3 IntroductionHuman and industrial development over the past hundred years has led to a huge increase in fossil fuel consumption and CO 2 emissions, causing a dramatic increase in atmospheric CO 2 concentration. This increased CO 2 is believed to be responsible for a significant rise in global temperature over the past several decades. In an attempt to solve these problems, researchers have proposed the large-scale sequestration of CO 2 from our atmosphere. Mineral carbonation aims to create stable carbonate minerals such as magnesite (MgCO 3 ) and calcite (CaCO 3 ) by reacting CO 2 with silicate minerals containing magnesium and calcium.1 Such minerals are stable over geologic timescales, so sequestration by this method would minimize risk of leaking back into the atmosphere in the future. Furthermore, the resulting material could be used as a building material, as an additive to concrete or paper, or as a soil amendment to improve texture, pH and fertility of low-productivity soils.The zinc-containing enzyme carbonic anhydrase catalyzes the reversible hydration of CO 2 to bicarbonate. 2 Actually, after CO 2 binding, the zinc-bound hydroxide (ZnOH) nucleophilically attacks the CO 2 to form bicarbonate. Then, a molecule of water coordinates directly to the zinc ion, which promotes diffusion of the bicarbonate out of the active site. Finally, the active site is regenerated by the removal of H + from the active site to a proton-transfer group, then to buffer, and finally to solvent (proton wire). This reaction is made possible by the amphiphilic active site of this enzyme. That is, on one side is a hydrophobic patch which is responsible for the binding of carbon dioxide. On the other side is a patch of hydrophilic residues that act to orient the CO 2 and also form the aforementioned proton wire. and metal organic frameworks 6 are good candidates for capturing CO 2 through physical adsorption. The physical adsorption process that requi...

The remarkable activity of template‐containing Mg/MCM‐41 and Ni/MCM‐41 in CO2 sequestration

“…Seawater pH is also limited to the range 7.5 and 8.4. Thus, we performed the CO 2 hydration reaction at pH = 8, like our previous work . The blank test (reaction without catalyst) was performed and resulted in an extremely low yield (5–10 mg CaCO 3 ).…”

“…Thus, we performed the CO 2 hydration reaction at pH = 8, like our previous work. 15 The blank test (reaction without catalyst) was performed and resulted in an extremely low yield (5-10 mg CaCO 3 ). Template-containing Mg/MCM-41 and Ni/MCM-41 showed higher catalytic activity in hydration of CO 2 relative to calcined and wet impregnated MCM-41 (e.g.…”

“…Despite the importance of these metals in CO 2 capture, there are a few solid sorbents containing zinc, nickel, and magnesium metals. [8][9][10][11][12][13][14] In continuation of our study on CO 2 sequestration, 15 we have synthesized Mg/MCM-41 and Ni/MCM-41 nano catalysts by two different metal-loading methods. Based on our experience, template-containing MCM-41 molecular sieve possesses highly basic sites so in some preparations the ionic template was preserved.…”

A study on zeolite-based adsorbents for $$\hbox {CO}_{2}$$ capture

“…Solid adsorbents can provide an alternative to the traditionally used aqueous absorbents for CO 2 capture due to relatively lower energy consumption, negligible corrosion problem and easy regeneration of adsorbents. CO 2 capture using solid adsorbents such as zeolites, AC, mesoporous silica, Al 2 O 3 and metal-organic frameworks are still under research [3][4][5][6][7][8]. The suitability of zeolite materials for the capture of CO 2 has been reported by many research groups.…”