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

被引:10
|
作者
Sierraalta, Anibal [1 ]
Alejos, Paola [1 ]
Ehrmann, Elena [2 ]
Rodriguez, Leonardo J. [3 ]
Ferrer, Yetziree [3 ]
机构
[1] Inst Venezolano Invest Cient, Ctr Quim, Lab Quim Computac, Caracas 1020A, Venezuela
[2] Univ Simon Bolivar, Dept Proc & Sistemas, Buruta Edo Miranda, Venezuela
[3] Fac Ciencias Expt, Dept Quim, Lab Quim Teor & Computac, Marocaibo, Venezuela
关键词
ONIOM; ZSM-5; CO; NO; Gold; Au; Zeolite; DFT; FTIR; NO REDUCTION; ZEOLITE CATALYSTS; GOLD; AG; PROPANE; SO2; CO; OXIDATION; SUPPORT; SCR;
D O I
10.1016/j.molcata.2008.11.008
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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 Delta G 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 Clue to the hydrogen bond formation between the NH3 hydrogen atoms and the oxygen atoms of the zeolitic framework. (C) 2008 Elsevier B.V. All rights reserved.
引用
收藏
页码:61 / 66
页数:6
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