DFT-ONIOM study of Au/ZSM-5 catalyst: Active sites, thermodynamic and vibrational frequencies

详细信息    查看全文

• 作者：Anibal Sierraalta ; Paola Alejos ; Elena Ehrmann ; Leonardo J. Rodriguez ; Yetziree Ferrer
• 关键词：ONIOM ; ZSM-5 ; CO ; NO ; Gold ; Au ; Zeolite ; DFT ; FTIR
• 刊名：Journal of Molecular Catalysis A: Chemical
• 出版年：2009
• 出版时间：18 March 2009
• 年：2009
• 卷：301
• 期：1-2
• 页码：61-66
• 全文大小：753 K

文摘

Density functional and ONIOM calculations were carried out to investigate the possible active sites of Au(I) ion-exchanged ZSM-5 catalysts. Adsorption energies and vibrational frequencies of CO, NO, NO₂, SO₂, H₂O, NH₃, CH₃NH₂ and CH₃SH molecules were analyzed. For first time the existence of two active sites in Au/ZSM-5 is shown; one of them is responsible for the high and the other for the low CO and NO adsorption frequencies. The analysis of adsorption ΔG shows that Au(I) behaves like a soft acid; therefore, there will be a preferential adsorption of soft bases over hard bases. The interaction with NH₃ is thermodynamically very favored, mainly due to the hydrogen bond formation between the NH₃ hydrogen atoms and the oxygen atoms of the zeolitic framework.