Patent ID: 7154009

Claim:
A process for the long-term operation of a heterogeneously catalyzed gas phase partial oxidation of propene to acrolein, by: conducting a starting reaction gas mixture which comprises propene, molecular oxygen and at least one inert diluent gas through a fixed catalyst bed at elevated temperature whose catalysts are such that their active composition is at least one multimetal oxide which contains the elements molybdenum and/or tungsten and also at least one of the elements bismuth, tellurium, antimony, tin and copper, and by, in order to counteract the deactivation of the fixed catalyst bed, and increasing the temperature of the fixed catalyst bed over the time, which comprises interrupting the gas phase partial oxidation at least once per calendar year and conducting a gas mixture G consisting of molecular oxygen, inert gas and optionally steam through the fixed catalyst bed at a temperature of the fixed catalyst bed of from 250 to 550° C.