| Summary: | The process of reduction (by hydrogen and ethanol) and oxidation (by oxygen and NO) of Cu sites in dealuminated faujasite-type zeolites (of Si/Al = 31) was studied by infrared (IR) spectroscopy with CO (for Cu<sup>+</sup>) and NO (for Cu<sup>2+</sup>) as probe molecules. Two zeolites were studied: one of them contained mostly Cu<sup>+</sup><sub>exch.</sub>, whereas another one contained mostly Cu<sup>2+</sup> and Cu<sup>+</sup><sub>ox.</sub> The susceptibility of various forms of Cu for reduction were investigated. IR experiments of CO sorption evidenced that Cu<sup>+</sup><sub>ox.</sub> was more prone for the reduction than Cu<sup>+</sup><sub>exch.</sub> According to NO sorption studies, Cu<sup>2+</sup><sub>exch.</sub> was reduced in the first order before Cu<sup>2+</sup><sub>ox.</sub> Ethanol reduced mostly Cu<sup>2+</sup> and, also, some amounts of Cu<sup>+</sup>. The treatment with oxygen caused the oxidation of Cu<sup>+</sup> (both Cu<sup>+</sup><sub>exch.</sub> and Cu<sup>+</sup><sub>ox.</sub>) to Cu<sup>2+</sup>. The adsorption of NO at 190K produced Cu<sup>+</sup>(NO)<sub>2</sub> dinitrosyls, but heating to room temperature transformed dinitrosyls to mononitrosyls and increased the Cu<sup>2+</sup> content.
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