(353a) Adsorption of Carbon Dioxide On Phase Change Material / Amino-Functionalized Mesoporous Silica Composite Adsorbent and Its Application to Carbon Dioxide Capture and Storage

Currently, remarkable attention has been paid to the capture and storage of carbon dioxide from flue gas to mitigate the greenhouse gas effect. The most major approach for carbon dioxide capture is the solvent absorption in which an aqueous solution of alkanoamine serving as an absorbent reacts chemically with mildly acidic carbon dioxide to form dissolved carbamates and bicarbonates. This process has been already in commercial use, however, it still has some drawbacks. Especially, it is a serious problem that the temperature swing required to regenerate the solvent leads to considerable energy consumption [1][2]. Hence, many studies have recently focused on the use of amino-functionalized mesoporous silicas as a solid adsorbent. These adsorbents possess the same chemical function at the surface of adsorbents as above-mentioned alkanoamine. That is, the anchored amine group on the mesoporous silicas forms a chemical bond with carbon dioxide, which plays an essential role for carbon dioxide capture. Nevertheless, its desorption is pressure dependent [1], meaning the pressure swing operation can also regenerate the used adsorbent [2]. This interesting nature provides a new possibility to overcome above-mentioned limitations of the solvent absorption using alkanoamine.

However, it should be also noted that the heat of adsorption onto amine-functionalized mesoporous silicas is considerably large [1]. Moreover, the adsorption of carbon dioxide onto amino-functionalized mesoporous silca is significantly affected by the temperauture [1]. Hence, adsorption of carbon dioxide causes a significant temperature increase in the adsorption column, resulting in the lowerness of adsorption performance. Aiming at the control of adsorption and desorption heats, this study deals with synthesis and application of phase change material (PCM)/amino-functionalized mesoporous silica composite adsorbent. PCM is a substance with a high melting and solidifying enthalpy, and thus, in the composite adsorbent, it works as a heat storage during the occurrence of adsorption or desorption heat to prevent the temperature changes in the adsorption column.

The synthesis strategy of the aforementioned composite adsorbent is based on the approach reported by Wesley et al.[3][4], which can easily synthesize the milimeter-to-centimeter sized spherical SBA-16 using nonionic surfactant (Pluronic F-127) and low concentiration of acid in the presence of butanol. By modifying the synthesis conditions, other types of mesoporous silica particles could be obtained. The mesoporous silica particles with uniformly dispersed PCM could be obtained by adding the microencapsulated PCM at the proper step of this synthesis. The amount of PCM contained in the adsrobent could be controlled easily by tuning PCM microcapsule addition. The experimental results on the carbon dioxide adsorption demonstrated that the composite adsorbent was very effective in controlling the temperature changes of the adsorbent due to the adsorption or desorption heat; quasi-isothermal adsorption and desorption was realized.

Reference

[1]Alan L. Chaffee, Gregory P. Knowles, Zhijian Liang, Jun Zhang, Penny Xiao, and Paul A. Webley, CO2 Capture by Adsorption: Materials and Process Development., International Journal of Greenhouse Gas Control 1(2007), 11-18

[2]V. Zelenak, D. Halamova, L. Gaberova, E. Bloch, and P. Llewellyn., Amine-modified SBA-12 Mesoporous Silica for Carbon Dioxide Capture: Effect of Amine Basicity on Sorption Peroperties., Mesoporous and Microporous Materials, 116(2008), 358-364

[3] Wesley J.J. Stevens, Myrjam Mertens, Steven Mullens, Ivo Thijs, Gustaaf Van Tendeloo, Pegie Cool and Etienne F. Vansant, Formation Mechanism of SBA-16 Spheres and Control of Their Dimensions., Microporous and Mesoporous Materials, 93 (2006), 119-124

[4] Wesley J. J. Stevens, Kurt Lebeau, Myrjam Mertens, Gustaaf Van Tendeloo, Pegie Cool, and Etienne F. Vansant, Investigation of the Morphology of the Mesoporous SBA-16 and SBA-15 Materials., J. Phys. Chem. B, 110 (2006), 9183?9187