Patent ID: 7005542

Claim:
A process for preparing an unsaturated aldehyde and/or an unsaturated carboxylic acid, which comprises the step of carrying out catalytic gas phase oxidation, with a catalyst, of at least one compound selected from the group consisting of propylene, isobutylene, t-butyl alcohol, and methyl t-butyl ether as a raw material, with molecular oxygen or a molecular-oxygen-containing gas, thereby producing the unsaturated aldehyde and/or the unsaturated carboxylic acid which corresponds to the raw material; with said catalyst being produced by a preliminary production process which comprises the steps of: carrying out heat treatment of an aqueous solution or slurry of a starting material to thus prepare a catalyst precursor P 1 , wherein the starting material includes molybdenum, bismuth, and iron as essential components; thereafter adding and mixing a binder into the catalyst precursor P 1 to thus prepare a catalyst precursor P 2 ; and molding and then calcining the catalyst precursor P 2 , thereby producing the catalyst for synthesis of the unsaturated aldehyde and/or the unsaturated carboxylic acid; with the preliminary production process involving the step of controlling an ignition loss ratio of the catalyst precursor P 1 in the range of 10 to 40 mass % (excluding 40 mass %) by adjusting at least one of a temperature of a heated gas, a linear velocity of a heated gas, and a heat-treatment time in carrying out said heat treatment of an aqueous solution or slurry of a starting material, and, when the catalyst precursor P 1 is heated under air atmosphere at 300° C. for 1 hour, the ignition loss ratio of the catalyst precursor P 1 is calculated from the following equation: ignition loss ratio (mass %)=((mass of catalyst precursor P 1 which has been prepared by said step of carrying out heat treatment of said aqueous solution or slurry of said starting material)−(mass of catalyst precursor P 1 after catalyst precursor P 1 has been heated under air atmosphere at 300° C. for 1 hour))/(mass of catalyst precursor P 1 which has been prepared by said step of carrying out heat treatment of said aqueous solution or slurry of said starting material)×100.