Patent ID: 8329942

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 the molar ratio of molecular oxygen to the raw material O/R such 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 O/R in the feed gas so as to rise with the progress of the reaction, wherein O/R in the feed gas at the start of the reaction is 1.8 to 2.2 and at the end of the reaction is 2.1 to 2.5.