Molecular oxygen assisted oxidative dehydrogenation of ethyl benzene to styrene with nanocrystalline Ti_1-xV_xO₂

Abstract

Oxidative dehydrogenation of ethylbenzene to styrene has been studied with vanadium-incorporated mesoporous nanocrystalline titania (Ti_1-xV_xO₂) and molecular oxygen between 440 and 530 °C. Incorporation of V in TiO₂ lattice framework has been achieved by simple solution combustion method. Incorporation of V in TiO₂ lattice has been confirmed by X-ray diffraction, XPS and Raman spectra and other physicochemical analysis. High ethyl benzene conversion and stable styrene yield has been observed with 10% V-containing rutile phase titania at 500 °C. However, stable but relatively lower styrene yield has been observed with 2 and 5% V-containing catalysts between 440 and 500 °C. Highest selectivity is observed with lower vanadium content. Comparable activity has been observed under similar experimental conditions with four times higher air-flow than that of O₂. In order to understand the structure activity relationship, spent catalysts were analyzed by all physico-chemical methods. Although there is a phase change from anatase to rutile Ti_1-xV_xO₂ within 1 h of reaction, higher activity is primarily attributed to the ionic V⁵⁺ in Ti_1-xV_xO₂ lattice, which prevents agglomeration to V₂O₅. It is to be underscored the reactivity is retained at the cost of textural properties and phase change from anatase to rutile, which is essential for the reaction.