INTERACTION OF THE NO-2 MIXTURE WITH CU(O)ZSM-5 ZEOLITE STUDIED BY ESR AND IR SPECTROSCOPY IN-SITU/

Isolated Cu2+ ions in the Cu/ZSM-5 catalyst are found to appear as a r esult of oxidation of Cu+ ions with NO2 molecules formed at temperatur es as low as 293 K. Cu2+ ions exist in the zeolite matrix in the squar e-planar or square-pyramidal coordination. Upon interaction with NO2 m olecules, a stable drop Cu2+-NO2 complex is formed, where Cu2+ is in t he square-planar coordination. Decomposition of the complex occurs at >620 K with the activation energy of 140 kJ/mol. The complex appears t o play a key role in NOx reduction with propane over copper-containing zeolites in the presence of an oxygen excess.