The structure of zirconium oxide in silica matrix and its epoxidation activity

Zirconia-silica composite oxides were prepared by a sol-gel method, and the state of Zr in the silica matrix was analyzed in relation to its activity in the epoxidation of oct-l-ene with t-butyl hydroperoxide. XAFS analysis s uggested that Zr in the composite oxides with low Zr content was in the coo rdinatively less saturated state compared with those in the oxides with hig her Zr contents. Epoxidation of oct-1-ene proceeded effectively on the oxid es with low Zr contents. The first step of the epoxidation was assumed to b e the interaction of t-butyl hydroperoxide with the coordinatively unsatura ted site of Zr.