Structure of active sites in Pd-exchanged mordenite: A density functional investigation
- Author(s)
- Robert Grybos, Juergen Hafner, Lubomir Benco, Hervé Toulhoat
- Abstract
Pd-exchanged mordenite (Pd-MOR) is considered as a promising catalyst for the selective catalytic reduction of nitrogen oxides (NOx) by hydrocarbons. However, it is well known that the chemical reactivity of the Pd2+ cations depends strongly on their location in the zeolite framework and on the coordination of the cation by the charge-compensating Al ions replacing Si framework atoms. In the present paper, we present a comprehensive investigation of the structure of the active sites in Pd-MOR based on periodic density functional calculations. For the possible configurations of Al in mordenite at a Si/Al ratio of 11, we find a rather narrow distribution of energies spreading over an interval of only 0.6 eV per primitive unit cell. This suggests that aluminum will be distributed more or less randomly over the framework. The stability of Pd2+ cations depends on the number of bonds between palladium and oxygen atoms directly connected to Al substitution sites. The energy difference between the most stable Pd locations in the main channel and the side pocket is found to be small (ca. 0.5 eV per primitive unit cell). However, the energy of a Pd cation in the side pocket is very sensitive to the local arrangement of Al sites, while Pd in the main channel remains quite stable for a number of different Al distributions.
- Organisation(s)
- Computational Materials Physics
- External organisation(s)
- Institut Francais du Petrole (IFP)
- Journal
- The Journal of Physical Chemistry Part C (Nanomaterials and Interfaces)
- Volume
- 111
- Pages
- 6454-6464
- No. of pages
- 11
- ISSN
- 1932-7447
- DOI
- https://doi.org/10.1021/jp0662606
- Publication date
- 2007
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1030 Physics, Astronomy
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/structure-of-active-sites-in-pdexchanged-mordenite-a-density-functional-investigation(9f24352f-a5ff-4a3e-a65e-b79ffc764802).html