Adsorption of CO2, CH4, and N2 on Gas Diameter Grade Ion-Exchange Small Pore Zeolites

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• 作者：Jiangfeng Yang ; Qiang Zhao ; Hong Xu ; Libo Li ; Jinxiang Dong ; Jinping Li
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2012
• 出版时间：December 13, 2012
• 年：2012
• 卷：57
• 期：12
• 页码：3701-3709
• 全文大小：548K
• 年卷期：v.57,no.12(December 13, 2012)
• ISSN：1520-5134

文摘

We prepared several different surfaces and pore volumes on small pore zeolites by hydrothermal synthesis and ion exchange (Li⁺, Na⁺, and Ca²⁺) based on three basic gas diameter grade structures of zeolites: KFI (0.39 脳 0.39 nm), CHA (0.38 脳 0.38 nm), and LEV (0.36 脳 0.48 nm), which were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and elemental analysis. The surface area and microporous volumes were calculated using the Dubinin鈥揜adushkevitch (D-R) equation based on CO₂ adsorption at 273 K. The CHA was synthesized with a lower Si/Al ratio, and the surfaces and microporous volumes were changed greatly by ion exchange. KFI had a higher Si/Al ratio, and the scope of the surface could be kept smaller. Focusing on the CO₂, CH₄, and N₂ adsorption isotherms at high pressure (1 MPa), we found that the samples were exchanged by Li⁺ and Na⁺ with bigger surfaces and greater adsorption volumes. The orifice diameter was very important in the sieving of CO₂ and N₂ or CO₂ and CH₄, while Na-LEV had an excellent sieving effect because N₂ and CH₄ could not diffuse into its structure like CO₂. From the viewpoint of the separate adsorption equilibria: Na-zeolites had the highest data adsorption equilibrium selectivity for CO₂ and N₂ or CO₂ and CH₄, followed by Li-zeolites, which only had a strong adsorption potential of CO₂; K-zeolites with high S_CO2/N2 and S_CH4/N2, based on the strong adsorption of CO₂ and CH₄. We conclude that the adsorption potential order was K-zeolites > Na-zeolites > Li-zeolites, so the bigger ions had a stronger affinity.