Patent ID: 8178720

Claim:
A method for producing an unsaturated aldehyde and an unsaturated carboxylic acid through gas-phase catalytic oxidation of propylene, isobutylene or tertiary butanol, which is a raw material, with molecular oxygen in the presence of a catalyst comprising a complex oxide including molybdenum, bismuth and iron as essential components, the method comprising: controlling reaction pressure in such a way that a rate of reaction of the raw material is kept constant in the temperature range of from (TA−15)° C. to TA° C., where TA° C. is the boundary temperature of the activation energy of the catalyst, and controlling reaction pressure such that the reaction pressure rises with the progress of the reaction of the raw material, wherein the reaction pressure at the start of the reaction is 90 to 110 kPa and is 105 to 125 kPa at the end of the reaction, where reaction pressure is an average of inlet pressure and outlet pressure and is expressed in gauge pressure.