Mesoporous Ce–Zr mixed oxides for selective oxidation of styrene in liquid phase

Abstract

This work reports the synthesis of mesoporous Ce_1-x-Zr_xO_2-δ (x?=?0.5 and 0.8) mixed oxides with distinct Ce/Zr mole ratio by inverse micelle template method and their catalytic exploration for epoxidation of styrene in isopropanol solvent using TBHP as the oxidant. Among various catalysts investigated, the Ce_0.8Zr_0.2O₂ combination catalyst exhibited best catalytic activity with?~?98% conversion and?~?90% selectivity to styrene epoxide. The synthesized Ce–Zr mixed oxide catalysts were characterized by various state-of-the-art techniques. Characterization studies revealed that Ce/Zr mole ratio has an imperative influence on the physicochemical properties such as surface area, oxygen vacancy concentration, and redox nature. Interestingly, catalytic efficiency was significantly improved with the increase of Ce and decrease of Zr content in the Ce–Zr mixed oxides. Catalytic efficiency and distribution of the products for styrene oxidation under various conditions such as reaction time, solvent, temperature, and styrene to TBHP mole ratio were also evaluated. Reusability of the highly active Ce_0.8Zr_0.2O₂ mixed oxide catalyst was also demonstrated.