Influence of the reaction time on the physical–chemical and catalytic properties of vanadium phosphate catalysts prepared by a eutectic mixture

Abstract

Vanadium phosphate (VPO) materials with high specific surface area prepared via a eutectic mixture as solvent and template with different lengths of time, i.e. 24, 72 and 144 h, were investigated in the oxidation of benzyl alcohol. The X-ray diffraction result indicated the initial VPO precursor was an amorphous phase due to the stronger incorporation of eutectic mixture. On subsequent reflux duration of 72 h, the precursor was composed of a crystallised VOHPO 4 ·H 2 O phase. On further reflux duration of 144 h, the incorporated eutectic mixture gradually was leached out and the precursor became more crystalline. Interestingly the N 2 adsorption–desorption measurements Brunauer–Emmett–Teller studies showed that the VPO precursor incorporated eutectic mixture was mesostructured and the specific surface area first increased then decreased with increasing the reflux duration time. The growth process of the VPO nanostructures formed in a eutectic mixture with different lengths of time was investigated by scanning electron microscopic analysis. The influence of calcination temperature and lengths of reflux duration on the activity and selectivity of the VPO catalyst was studied and discussed.