LAUSR

Abstract Vanadium-chromium oxides (VCrO) were usually prepared by high-temperature solid-state reactions; however, mixed phases were frequently produced and the morphology of the products was not well controlled. In this work, we prepared amorphous VCrO precursors by using V2O5 and CrO3 and alcohols or mixtures of alcohol and water via solvothermal reaction at 180 °C. The precursors were then calcined under nitrogen at various temperatures. The products were characterized by powder X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was revealed that pure-phase nanocrystalline orthorhombic CrVO4 was obtained when methanol or methanol/water was used as the solvothermal medium and the precursor was calcined at 700 °C. The size of the CrVO4 crystals was around 500 nm when methanol was used, whereas it reduced significantly to less than 50 nm when a mixture of methanol and water was used. The sizes could be effectively tuned from 10 to 50 nm by varying the methanol/water volume ratio. To the best of our knowledge, this is the first report on the synthesis of pure-phase CrVO4 nanocrystals. The nano-CrVO4 showed almost the highest catalytic activity for the ammoxidation of 2,6-dichlorotoluene to 2,6-dichlorobenzonitrile among the reported bi-component composite oxides, owing to its smaller particle size, larger specific surface area, and more exposed active centers.