| abstract |
A process for regenerating a catalyst consisting of a mixed oxide having molybdenum, bismuth and iron used for preparing an unsaturated aldehyde and/or an unsaturated carboxylic acid by catalytically oxidizing propylene, isobutylene and/or tert.-butanol with molecular oxygen in a gas phase, in which the catalyst is regenerated by thermally treating the deteriorated catalyst in an atmosphere of a gas containing molecular oxygen at a temperature of 200 to 500° C., and then thermally treating the catalyst in the presence of a reducing compound at a temperature of 200 to 500° C. |