Influence of the preparation conditions on the physico-chemical and catalytic properties of a vanadium-aluminum oxynitride propane ammoxidation catalyst

Abstract

The influence of the precipitation pH and of the vanadium concentration in solution on the physico-chemical properties and catalytic activity of the V-Al oxynitride catalyst system was investigated. The V-Al precursor oxide samples were submitted to a nitridation treatment to form the V-Al oxynitride (VAlON), which is the active and stable phase during the catalytic reaction. The VAlON catalyst was subsequently tested in the propane ammoxidation reaction and characterized by BET-surface area, X-ray diffraction, temperature programmed reduction (TPR), nitrogen and metal content analyses. Optimal acrylonitrile (ACN) selectivity was observed for the sample prepared at pH=5.5 and vanadium concentration in solution=30.10(-3) M. This catalyst also showed the highest specific surface area, reduction temperature and nitrogen content. The existence of an optimum balance between the basic properties provided by surface and bulk nitrogen species (N-3 and NH(x)rectangle) and the redox capacity of the vanadium ions (Vrectangle+) would explain the catalytic behavior of the VAlON system in propane ammoxidation reaction