A NEW TERNARY MIXED-OXIDE CATALYST FOR AMMOXIDATION OF PROPANE - SN V/SB/

The catalytic properties of a Sn/V/Sb mixed oxide for propane ammoxida tion to acrylonitrile are studied in this paper. In particular the ant imony and vanadium amounts were changed in order to optimize the relat ive atomic ratio. The ternary sample with the best catalytic performan ce was compared with the analogous binary samples (Sn/Sb and Sb/V). Th e results obtained indicate that vanadium is responsible for the paraf fin activation, nevertheless much vanadium produces a lot of carbon ox ides. Antimony is responsible for the insertion of nitrogen in the mol ecule (it can be considered as an acrylonitrile selectivity modulator) ; nevertheless, too much antimony deactivates the catalyst. Tin does n ot act only as a dispersive matrix for the active sites, but leads to the formation of a polyfunctional catalyst, increasing the rate of acr ylonitrile formation from the intermediate propene. From a structural point of view, this catalytic system can be described as a homogeneous system, containing microfields of rutile type oxide (SnO2), promoted with antimony and vanadium in substitutional solid solution, dispersed in an excess of amorphous antimony oxide.