4.27 Acid Property and Metathesis Activity of WO3-ZrO2 Catalysts

Abstract

Acidity and acid strength of ZrO2 were enhanced by addition of WO3. Surface OH group as Brønsted acid was divided into two groups by WO3 content. One of them is a group of acid sites which are able to convert to metathesis active sites while the other is not. The metathesis activity was produced by evacuation at over 300°C. It is assumed that the low valent tungsten ions are generated by dehydration of surface tungsten hydroxide as precursors of metathesis active sites. The spectra shapes of O2− formed on the catalysts were different from low content catalysts (W/Zr≤0.1) and high content catalysts (W/Zr≥0.2). There appeared to be two kinds of O2− on the high content catalysts. The metathesis active sites, which act as formation sites of O2−, were only produced on high content catalysts.