Density Functional Theory Study on the Adsorption of H2S and Other Claus Process Tail Gas Components on Copper- and Silver-Exchanged Y Zeolites

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• 作者：Chun-Yi Sung ; Saleh Al Hashimi ; Alon McCormick ; Michael Tsapatsis ; Matteo Cococcioni
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：February 9, 2012
• 年：2012
• 卷：116
• 期：5
• 页码：3561-3575
• 全文大小：1449K
• 年卷期：v.116,no.5(February 9, 2012)
• ISSN：1932-7455

文摘

The potential use of Cu- and Ag-exchanged Y zeolites as selective adsorbents for hydrogen sulfide (H<sub>2sub>S) from Claus process tail gas was investigated with density functional theory (DFT). The adsorption energies of H<sub>2sub>S and other Claus tail gas components (CO, H<sub>2sub>O, N<sub>2sub>, and CO<sub>2sub>) were computed for these zeolites as well as for Li鈥揧, Na鈥揧, and K鈥揧 on a cluster model. Comparison of adsorption energies for H<sub>2sub>S versus the other components indicated that Ag鈥揧 has potential for selective adsorption of H<sub>2sub>S, whereas Cu鈥揧 is subject to strong adsorption of CO, and alkali metal-exchanged Y zeolites are subject to H<sub>2sub>O adsorption. Comparison with alkali metal-exchanged Y zeolites was performed to clarify the role of d electrons, while the influence of the zeolite framework was assessed by comparing adsorption energies on the cluster model with those on bare cations. Absolutely localized molecular orbital energy decomposition analysis (ALMO EDA) revealed that for Cu- and Ag-containing systems, transfer of electrons between the cation and the adsorbate, i.e., the donation of d electrons and the acceptance of electrons in the unoccupied orbitals of the cation, plays an important role in determining the adsorption energy. On the other hand, for alkali metals-containing systems, charge transfer is negligible and adsorption energies are dominated by interactions due to electrostatics, polarization, and structural distortions.