Selective oxidation and ammoxidation of propane on a Mo-V-Te-Nb-O mixed metal oxide catalyst: a comparative study

A comparative study on the selective oxidation and the ammoxidation of propane on a Mo-V-Te-Nb-O mixed oxide catalyst is presented. The catalyst has been prepared hydrothermally at 175 degreesC and heat-treated in N-2 at 600 degreesC for 2 h. Catalyst characterization results suggest the presence mainly of the orthorhombic Te2M20O57 (M= Mo, V and Nb) bronze in samples before and after use in oxidation and ammoxidation, although some little modifications have been observed after its use in ammoxidation reaction. Propane has been selectively oxidized to acrylic acid (AA) in the 340-380 degreesC temperature range while the ammoxidation of propane to acrylonitrile (ACN) has been carried out in the 360420 C temperature interval. The steam/propane and the ammonia/propane molar ratios have an important influence on the activity and the selectivity to acrylic acid and acrylonitrile, respectively. The reaction network in both oxidation and ammoxidation reactions as well as the nature of active and selective sites is also discussed. The catalytic results presented here show that the formation of both ACN and AA goes through the intermediate formation of propene. (C) 2004 Elsevier B.V. All rights reserved.