Abstract
Abstract A quantitative ESR study of copper-deficient CuH-ZSM-5 demonstrates that the valence state of copper in this system is determined by the techniques of sample preparation and pretreatment. Oxidative calcination of the system at 500–550°C results, however, in a stabilization of the majority of copper by the H-ZSM-5 matrix in the form of isolated Cu 2+ cations, irrespective of the method of copper introduction. No measurable auto-reduction of Cu 2+ occurs upon calcination of the samples which are free of organic impurities. Peculiarities in the change of the ESR signal intensity upon water adsorption–desorption are related to the change in the coordination of Cu 2+ and the spin–lattice interaction between Cu 2+ ions and the zeolitic framework.
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