| Autor: |
Feng, Yingxin, Janssens, Ton V. W., Vennestrøm, Peter N. R., Jansson, Jonas, Skoglundh, Magnus, Grönbeck, Henrik |
| Zdroj: |
The Journal of Physical Chemistry - Part C; April 2024, Vol. 128 Issue: 16 p6689-6701, 13p |
| Abstrakt: |
Cu-exchanged chabazite (Cu-CHA) shows good performance for selective catalytic reduction of nitrogen oxides using NH3as a reducing agent (NH3-SCR). The temperature dependence of the activity has a characteristic nonmonotonic behavior with a minimum in the range 300–350 °C. The minimum signals that different reaction mechanisms or active sites dominate at low and high temperatures. The low-temperature mechanism is believed to occur over a pair of mobile [Cu(NH3)2]+complexes, whereas the high-temperature mechanism should proceed over framework-bound Cu ions. To explore the NH3-SCR reaction over framework-bound Cu ions, we use first-principles calculations combined with mean-field microkinetic simulations. We find that the reaction proceeds over a single framework-bound Cu ion and that the first step is NO and O2coadsorption. The coadsorption competes with NH3adsorption, and the NH3-SCR rate is largely determined by the adsorption energy of NH3. Combining the high-temperature kinetic model with our previous low-temperature model for NH3-SCR over pairs of mobile [Cu(NH3)2]+complexes makes it possible to describe the nonmonotonic behavior of the reaction rate. The work provides a detailed mechanistic understanding of the role and transformation of different forms of Cu ions during low- and high-temperature standard SCR in Cu-CHA. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
