Redox behaviour of transition metal ions in zeolites. Part 3.—Auto-reduction of cupric ions in Y zeolites

Abstract
In CuY zeolites degassed at temperatures above 650 K cupric ions are reduced to some extent to cuprous ions. Evidence for this process of auto-reduction was taken from the decrease in weight of the sample, and the detection of a desorbing gas in a volumetric system. The latter was identified as oxygen. U.v. reflectance spectroscopy showed directly the decrease of the Cu2+ species upon outgassing and their increase after oxygen adsorption. Excitation spectra showed the presence of Cu+ ions after high temperature degassing. Infrared spectroscopic techniques showed that Lewis sites are also formed upon degassing. A mechanism is proposed that accounts for the observations.

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