Co2 Adsorption Capacity Is Defined As A Measure Of An Adsorbent

3415 Words Jul 31st, 2014 14 Pages
CO2 adsorption capacity is defined as a measure of an adsorbent’s capability or potential to adsorb CO2. It is expressed in terms of number of moles of CO2 that a unit mass of an adsorbent adsorbs under equilibrium conditions. The CO2 adsorption isotherms for MCM-41-30, MCM-41-30-AP-9-85-0.5 and MCM-41-30-TP-9-75-0.3 at 30 °C are presented in Figure 6(a). The CO2 adsorption isotherms for amine tethered samples exhibit a steep nonlinear concave shape due to the strong interactions between carbon dioxide molecules and amine moieties. In contrast, MCM-41-30 exhibits a less steep isotherm indicating that pure silica interacts with CO2 only by physisorption and hence lacks sufficient strong affinity towards CO2. Therefore, it is clear that the adsorption of CO2 on pure MCM-41 approaching the maximum adsorption with subsequent increase in pressure is a mere consequence of the large surface area and pore volume of this support. The CO2 adsorption capacity of amine grafted samples dramatically depends on the amount of accessible amine ligands. MCM-41-30-AP-9-85-0.5 and MCM-41-30-TP-9-75-0.3 samples, that are characterized by the maximum surface density of mono and tri amine ligands shows the steepest CO2 isotherm and the highest CO2 adsorption capacity attaining 1.58 and 1.75 mmol/g respectively at 0.2 bar and 30 °C. This underlines the fact that CO2 adsorption capacity increases with increasing surface density of accessible amine moieties although the surface area (SBET) of amine…
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