Phosphotungstic acid promoted zirconia–alumina mixed oxides: A stable and reusable catalysts for epoxidation of trans-stilbene

Zirconia–alumina mixed oxide supported phosphotungstic acid catalysts were synthesized and characterized by various techniques. The surface and bulk properties of the catalysts were examined by X-ray diffraction, BET surface area, ammonia-TPD, TPR, 31P MAS NMR and FTIR techniques. The prepared catalysts were evaluated for liquid phase epoxidation of trans-stilbene using tert-butylhydroperoxide as an oxidant. Among all the promoted catalyst, 25 wt.% phosphotungstic acid impregnated zirconia–alumina mixed oxide showed 46% conversion and 89% of selectivity towards trans-stilbene oxide formation.