Xenon Capture on Silver-Loaded Zeolites: Characterization of Very Strong Adsorption Sites

详细信息    查看全文

• 作者：C茅cile Daniel ; Adnane Elbaraoui ; Sonia Aguado ; Marie-Anne Springuel-Huet ; Andrei Nossov ; Jean-Pierre Fontaine ; Sylvain Topin ; Thomas Taffary ; Ludovic Deliere ; Yves Schuurman ; David Farrusseng
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：July 25, 2013
• 年：2013
• 卷：117
• 期：29
• 页码：15122-15129
• 全文大小：448K
• 年卷期：v.117,no.29(July 25, 2013)
• ISSN：1932-7455

文摘

The number and strength of adsorption sites for Xe in silver-modified zeolites are estimated from isotherm measurements at various temperatures over a broad range of pressure (from 1 ppm to atmospheric pressure). Fully and partially exchanged silver zeolites were synthesized starting from Na-ZSM-5(25), Na-ZSM-5(40), Na-Beta, NaX, and NaY. We have discovered that silver-modified zeolites may present one or two distinct adsorption sites depending on the nature of the material and silver loadings. The strongest adsorption sites are characterized by isosteric heat of adsorption in the order of 鈭?0 to 鈭?0 kJ路mol^鈥?. For Pentasil-type zeolites, we observe a linear 2:1 correlation between the total amount of silver and the number of strong sites. The highest concentration of strong sites is found for fully silver exchanged ZSM-5 (5.7 脳 10^鈥? mol/g), which presents the largest silver content for Pentasil-type zeolite. The equilibrium constant of Ag-ZSM-5 at low pressure is about 50 times larger than that of AgX. Qualitative correlations were established between Xe adsorption isotherms and Xe NMR signals. We show that Xe NMR could be used as a quantitative method for the characterization of the strength and of the number of strong Xe adsorption sites on silver-exchanged zeolites. The numbers of strong adsorption sites responsible for the Xe adsorption at 10鈥?000 ppm can be determined by the length of the plateau observed at low Xe uptake. In practice, our findings give guidelines for the discovery and optimization of silver-loaded zeolites for the capture of Xe at ppm levels. It appears that the amount of silver is a key parameter. Silver-modified ZSM-5 shows adsorption capacities 2鈥? orders of magnitude larger than currently applied adsorbents for atmospheric Xe capture.