Reduction and Oxidation of Cu Species in Cu-Faujasites Studied by IR Spectroscopy.

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) and NO (for Cu) as probe molecules. Two zeolites were studied: one of them contained mostly Cu, whereas another one contained mostly Cu and Cu The susceptibility of various forms of Cu for reduction were investigated. IR experiments of CO sorption evidenced that Cu was more prone for the reduction than Cu According to NO sorption studies, Cu was reduced in the first order before Cu Ethanol reduced mostly Cu and, also, some amounts of Cu. The treatment with oxygen caused the oxidation of Cu (both Cu and Cu) to Cu. The adsorption of NO at 190K produced Cu(NO) dinitrosyls, but heating to room temperature transformed dinitrosyls to mononitrosyls and increased the Cu content.