Rutile-type metal (Cr, V) niobates as catalysts for propane ammoxidation to nitriles: In situ characterization and operando reactivity

Rutile-type Cr/Nb and V/Nb mixed oxides were prepared by co-precipitation from ethanolic solutions, and calcination at 700 8C. The development of the rutile structure during the thermal treatment of the precursor was investigated by in situ TP‐Raman spectroscopy. It was found that graphite-like carbon deposits build-up during calcinations in inert. Their decomposition providesthe reducing agent that leads to the formation of rutile VNbO4 at relatively mild conditions. Rutile Cr and V niobates were tested as catalysts for the ammoxidation of propane, under both hydrocarbon-rich and hydrocarbon-lean conditions. Catalysts were active but non-selective to acrylonitrile. The catalyst modifications occurring during reaction were followed by operando Raman‐GC methodology. VNbO4 transforms into a catalyst active and selective for acetonitrile under leaner hydrocarbon feed. # 2005 Elsevier B.V. All rights reserved.