Structural and kinetic studies in propene oxidation over Sb oxide dispersed on TiO2

Abstract

Antimony oxide dispersed on TiO2 was characterized using FTIR, Raman, and Auger spectroscopies as well as XRD. They indicate that the electronic environment about Sb is perturbed at low concentration suggesting that the structure of Sb oxide on TiO2 is somewhat distorted as compared to Sb6O13. The oxidation of labeled propene such as CH2=CH---CD3, 13CH2=CH---CH3, and cis-CHD=CD---CH3 was examined on Sb6O13 and Sb---Ti oxide catalysts. The results indicate that the first hydrogen abstraction is rate determining and that there is little or no isotope effect in the second hydrogen abstraction over Sb and Sb---Ti oxide catalysts. The oxidation kinetics was discussed on the basis of a modified redox mechanism. The reduction step was promoted by a factor of ca. 50 over Sb oxide dispersed on TiO2 as compared to that on unsupported Sb6O13. Rate promotion was mainly attributed to the increase in the amount of active sites for the reduction step.