Ammonia-Containing Species Formed in Cu-Chabazite As Per In Situ EPR, Solid-State NMR, and DFT Calculations.
Nowadays, the most attractive technology for the elimination of nitric oxides from the exhaust gas of diesel vehicles is the selective catalytic reduction with ammonia (NH3-SCR-NOx) using Cu zeolite with the chabazite structure as the catalyst. Isolated copper species are the active sites, but the reaction intermediates and the overall reaction mechanism are still under debate. Here, we study the interaction of ammonia with zeolite Cu-SSZ-13 (CHA topology) with a uniform distribution of Cu(2+) sites prepared in one pot and a conventional Cu-ZSM-5 (MFI topology) for comparison. In situ EPR and solid-state NMR spectroscopies combined with DFT calculations have allowed the identification of NH4(+), [Cu(NH3)5](2+), [Cu(Of)2(NH3)2](2+), [Cu(Of)3NH3](2+), [Cu(NH3)2](+), and [CuOf(NH3)](+) (Of being framework oxygen) under different conditions. The results demonstrate that ammonia is able to reduce Cu(2+) to Cu(+) and provide new information on the species formed in Cu-SSZ-13, which have important implications for the elucidation of the SCR reaction mechanism.
Instituto de Tecnologı́a Quı́mica (UPV-CSIC), Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Cientı́ficas, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Marta
M
Moreno-González
Instituto de Tecnologı́a Quı́mica (UPV-CSIC), Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Cientı́ficas, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Beatriz
B
Hueso
Instituto de Tecnologı́a Quı́mica (UPV-CSIC), Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Cientı́ficas, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Mercedes
M
Boronat
Instituto de Tecnologı́a Quı́mica (UPV-CSIC), Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Cientı́ficas, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Teresa
T
Blasco
Instituto de Tecnologı́a Quı́mica (UPV-CSIC), Universidad Politécnica de Valencia - Consejo Superior de Investigaciones Cientı́ficas, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Avelino
A
Corma
D000393:Air Pollutants / Q000737:chemistry; D000641:Ammonia / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D001335:Vehicle Emissions / Q000032:analysis; D017641:Zeolites / Q000737:chemistry*
D000393:Air Pollutants; D001335:Vehicle Emissions; C554923:chabazite; D017641:Zeolites; D000641:Ammonia; D003300:Copper; D010100:Oxygen
DFT; EPR; NMR; SCR; ZSM-5; chabazite; nitric oxides