The selective ammoxidation of propene was studied over SnO2-Sb2O4 and promoted (Bi2O3, Ga2O3, In2O3 and Tl2O3) tin-antimony mixed oxide catalysts. Over binary tin-antimony oxides, the main products of the allyl type oxidation are acrylonitrile and acrolein, but doping with oxide promoters was found to influence the selectivity towards formation of special products. Over catalysts promoted with In2O3, 1,5-hexadiene and benzene are produced from two propene molecules chemisorbed on the same In3+ center residing in the surface layer of the catalyst. The formation of 4-methylpent-2-enonitnle over catalysts doped with Bi2O3, Ga2O3 or Tl2O3 is explained by the ammoxidation of 4-methylpent-2-enyl carbenium ion produced by the interaction of a π-allyl intermediate and an isopropyl carbenium ion formed on surface Brönsted acidic centers.
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