PROPANE AMMOXIDATION TO ACRYLONITRILE OVER A TIN-BASED MIXED-OXIDE CATALYST

The catalytic properties of a Sn/V/Sb mixed oxide for propane ammoxida tion to acrylonitrile are studied in this paper. First, preparing the sample with a coprecipitation method from an ethanolic phase, the amou nts of antimony and vanadium were changed in order to optimize the rel ative atomic ratio of the ternary catalyst. The results obtained indic ate that vanadium is responsible for the paraffin activation and antim ony for the insertion of nitrogen in the molecule tit can be considere d as an acrylonitrile selectivity modulator). Other samples, with the optimized atomic ratio, were also prepared using a similar coprecipita tion technique (but by dissolving the starting materials with iso-buta nol or water instead of ethanol), or by solid state reaction between o xide and tin hydroxide, The sample prepared using ethanol shows the be st catalytic performance. This solvent makes the partial alkoxides qui te stable in solution and brings about better coprecipitation with a m ore intimate mixture of tin, antimony and vanadium. Finally, the therm al transformation of the precursor of this sample was followed during calcination, both in air and in nitrogen with several characterization techniques. The thermal treatment in air at 700 degrees C leads to th e best catalytic performance, i.e., goad activity and high selectivity . (C) 1998 Elsevier Science B.V. All rights reserved.