Active sites of WO3ZrO2 for metathesis and isomerization of 1-butene characterized by ESR

The surface of WO3ZrO2 prepared by a co-precipitation has been characterized by ESR. Three kinds of O2− radicals having different g1 values (SI: g = 2.028, SII: g = 2.026, and SIII: g = 2.015) were formed on the surface of WO3ZrO2 by introduction of O2 at room temperature. The ESR signals were divided into two groups from the changes of their intensities by the View the MathML source ratio; SI and the other two (SII and SIII). It was found that the View the MathML source ratio dependence of catalytic activity for metathesis of 1-butene was very close to those of the intensities of SII and SIII. This indicates that the active sites for metathesis concern with those giving SII and SIII, where SII and SIII are presumed to be W4+ and W5+ to form O2−W5+ and O2−W6+, respectively.