Adsorption of CO2-Containing Gas Mixtures Over Amine-Bearing Pore-Expanded MCM-41 Silica: Application to CO2 Separation and Purification
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Adsorption technology such as pressure swing or temperature swing adsorption is widely used for purification and separation of gases (Ruthven et al., 1994). Adsorption is considered to be a competitive method for CO2 removal in comparison to other technologies, provided that highly selective adsorbents with high CO2 capacity are available. A large variety of CO2 solid sorbents have been reported in the literature including oxides (Lee et al., 2008), zeolites (Cavenati et al. 2004), activated carbons (Himeno et al., 2005), metal-organic frameworks (MOFs) (Millward and Yaghi 2005), organo-silicas and surface-modified silicas (Hicks et al., 2008, Yue et al., 2008).
In this work, adsorption of CO2 on triamine-grafted pore-expanded mesoporous MCM-41 silica TRI-PE-MCM-41 was investigated from very low pressure to 25 bar at four temperatures (298, 308, 318, 328 K) using gravimetric measurements. The adsorption isotherms, at very low partial pressure of CO2, showed one of the highest equilibrium capacities compared to other typical CO2 adsorbents such as zeolites, activated carbon and MOFs. In contrast, under the same pressure and temperature conditions TRI-PE-MCM-41 exhibited very small uptakes of N2, CH4, H2 and O2. Breakthrough dynamic measurements of CO2 in mixtures with other species showed exceedingly high selectivity of CO2 over N2, CH4, H2 and O2 in a wide range of CO2 concentration, indicating that TRI-PE-MCM-41 is suitable for gas separation and purification. In addition, TRI-PE-MCM-41 was found to be moisture-tolerant and highly stable over hundreds of adsorption-desorption cycles using temperature swing (TS) or temperature-pressure swing (TPS) as regeneration modes.
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