Co2 Adsorption Capacity Is Defined As A Measure Of An Adsorbent

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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…show more content…
Amine efficiency provides a measure of the fraction of amine groups present in an adsorbent that actively participate in adsorbing CO2 by chemisorption. It is reported that the theoretical maximum value for amine efficiency that an ideal adsorbent should exhibit under dry CO2 adsorption conditions is 0.5 (for PCO2 = 0.1-0.2) i.e., in the absence of significant physisorption at non-functionalized sites. The amine efficiency values for MCM-41-30-AP-9 series and MCM-41-30-TP-9 series are presented in Table 2, from which the variation in amine efficiency with respect to amine loading can be noticed. From Table 2, it is evident that, as amine loading increases, at first amine efficiency increases, then reaches a maximum at a critical value of amount of water added in the reaction mixture and then finally drops off at water levels higher than the critical value for both mono and tri aminosilane addition. The similar trend in amine efficiency is observed with respect to increase in grafting temperature for constant amount of water, in case of both mono and tri amino silane compounds. MCM-41-30-AP-9-85-0.5 sample exhibited the maximum amine efficiency of ~0.5, which is close to theoretical maximum value. This proves that MCM-41-30 serves as an ideal support for amine tethering process, where the CO2 adsorption process is not hindered due to transport/diffusion
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