Optical spectra of Co-zeolites

Abstract

The coordination changes of Co^II in A, X, Y zeolites, dried at high temperature, have been investigated by diffuse reflectance spectroscopy. Fully hydrated zeolites show an octahedral coordination of Co^II. During dehydration at high temperature, Co^II in X and Y zeolite changes its coordination, first from symmetric to a distorted tetrahedral and, successively, to an octahedral coordination.

Co^II in A zeolite, changes its coordination from slightly distorted tetrahedral to threefold.

The formation of Co oxide species has been observed during calcination at high temperature of CoX and CoY.

The rate sequence of re-hydration of species dehydrated at high temperature, is CoA CoY > CoX.