Time on stream behaviour in the (amm)oxidation of propene/propane over iron antimony oxide: cyclic operation

The time on stream behaviour of the selective (amm)oxidation of propene and propane over an active iron antimony oxide catalyst showed that the activi ty and selectivity of these catalysts decreased significantly with time on stream. Also gamma-Bi2MoO6 shows a strong time on stream behaviour. It is s hown that the selectivity for acrolein increases strongly with time on stre am for the bismuth molybdate catalyst. The activity, however, decreases str ongly. The catalytic performance of iron antimony oxide catalyst can be imp roved by operating the partial oxidation/ammoxidation in a cyclic mode, i.e . alternating the feed from reducing (hydrocarbon/air(/ammonia)) to oxidisi ng (air) atmospheres. It is shown that the re-oxidation of the catalyst can be performed at the same temperature as the reaction temperature. The orig inal oxidation state is, however, not fully regained. Elevated temperatures or prolonged oxidation times are required to regain the original oxidation state of the catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.