Electron spin resonance of copper-exchanged Y zeolites. Part 1.—Behaviour of the cation during dehydration

Abstract

Copper Y zeolites were dehydrated under vacuum and their e.s.r. spectra recorded at different intermediate stages of the dehydration. The results show a complex evolution of spectra, with the occurrence of several symmetric and asymmetric bands, some of which have been overlooked in the previous literature. Use is made of band broadening by oxygen and of numeric subtraction of the spectra, in order to isolate these bands and to determine their shapes. In this way, two symmetric peaks and five asymmetric bands are characterized; apart from these, there are Cu^II ions which do not appear in the spectrum. Discussion of these results leads to the proposal of a detailed dehydration scheme, in which all the detected bands are tentatively assigned to differently coordinated copper species in several lattice sites.