Adsorption of CO2-Containing Gas Mixtures Over Amine-Bearing Pore-Expanded MCM-41 Silica: Application to CO2 Separation and Purification

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.

References

Ruthven, D. M.; Farooq, S.; Knaebal, K. S. Pressure swing adsorption. VCH: New York, 1994.

Lee, K. B.; Beaver, M. G.; Caram, H. S.; Sircar, S. Reversible chemisorbents for carbon dioxide and their potential applications. Ind. Eng. Chem. Res. 2008, 47, 8048-8062.

Cavenati, S.; Grande, C. A.; Rodrigues, A. E. Adsorption equilibrium of methane, carbon dioxide, and nitrogen on zeolites 13X at high pressures. J. Chem. Eng. Data 2004, 49, 1095-1101.

Himeno, S.; Komatsu, T.; Fujita, S. High-pressure adsorption equilibria of methane and carbon dioxide on several activated carbons. J. Chem. Eng. Data 2005, 50, 369-376.

Millward, A. R.; Yaghi, O. M. Metal-organic frameworks with exceptionally high capacity for storage of carbon dioxide at room temperature. J. Am. Chem. Soc. 2005, 127, 17998-17999.

Hicks, J. C.; Drese, J. D.; Fauth, D. J.; Gray M, L.; Qi, G.; Jones, C. W. Designing adsorbents for CO2 capture from flue gas - hyperbranched aminosilicas capable of capturing CO2 reversibly. J. Am. Chem. Soc. 2008, 130, 2902-2903.

Yue, M. B.; Sun, L. B.; Cao, Y.; Wang, Y.; Wang, Z. J.; Zhu, J. H. Efficient CO2 capturer derived from as-synthesized MCM-41 modified with Amine. Chem. Eur. J. 2008, 14, 3442-3451.&'