The interaction of nitric oxide with copper ZSM5 zeolites at room temperature has been studied by EPR and FT-IR spectroscopy in the aim of investigating the surface intermediates involved in the decomposition of NO to N2 and O2. Particular care has been devoted to obtaining a catalyst in a well-defined oxidation state, i.e., with one of the two ionic forms of copper (Cu2+ or Cu+) clearly prevailing on the other. The interaction of NO with Cu2+/ZSM5 yields a reversibly adsorbed nitrosylic adduct easily desorbed upon pumping at 333 K. The species is diamagnetic and bears a partial positive charge. Cu+ is unstable under NO pressure and undergoes oxidation at room temperature. In the early stages of the interaction a paramagnetic nitrosyl of Cu+ is formed having a partial negative charge on NO. This species evolves with time (or NO pressure) towards a diamagnetic dinitrosyl capable of eliminating N2 with simultaneous oxidation of the site to Cu2+.

The interaction of NO with copper ions in ZSM5: and EPR and IR investigation

GIAMELLO, Elio;MAGNACCA, Giuliana;MORTERRA, Claudio;
1992-01-01

Abstract

The interaction of nitric oxide with copper ZSM5 zeolites at room temperature has been studied by EPR and FT-IR spectroscopy in the aim of investigating the surface intermediates involved in the decomposition of NO to N2 and O2. Particular care has been devoted to obtaining a catalyst in a well-defined oxidation state, i.e., with one of the two ionic forms of copper (Cu2+ or Cu+) clearly prevailing on the other. The interaction of NO with Cu2+/ZSM5 yields a reversibly adsorbed nitrosylic adduct easily desorbed upon pumping at 333 K. The species is diamagnetic and bears a partial positive charge. Cu+ is unstable under NO pressure and undergoes oxidation at room temperature. In the early stages of the interaction a paramagnetic nitrosyl of Cu+ is formed having a partial negative charge on NO. This species evolves with time (or NO pressure) towards a diamagnetic dinitrosyl capable of eliminating N2 with simultaneous oxidation of the site to Cu2+.
1992
136
510
520
EPR and IR measurements; Cu-ZSM5; NO adsorption
GIAMELLO E; MURPHY D; G. MAGNACCA; MORTERRA C; SHIOYA Y; NOMURA T; ANPO M
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/26783
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