APCATA 250-2003-75

IR study of acid sites on WO3-ZrO2

The mechanism of the generation of protonic acid sites from molecular hydrogen on WO3-ZrO2 was studied by IR
spectroscopy. The spectral changes in the W=O stretching and the OH stretching regions were observed in response to the
exposure to hydrogen and the removal of hydrogen. By heating in the presence of hydrogen, the W=O stretching bands at
1021 and 1014 cm−1 eroded and a broad band around 980 cm−1 was developed. The peaks at 1021, 1014 and 980 cm−1
restored to their original intensities on heating in a vacuum. A broad OH stretching band around 3600 cm−1 was intensified
by heating in the presence of hydrogen and restored to its original intensity by removal of the hydrogen from a gas phase.
Pyridine adsorption caused essentially the same changes in the W=O stretching region as hydrogen adsorption. Based on the
spectral changes, the changes in the structure of acid sites caused by hydrogen adsorption are proposed.
© 2003 Elsevier Science B.V. All rights reserved.