Abstract: An object of the present invention is to provide a catalyst capable of improving the selectivity of unsaturated aldehydes and unsaturated carboxylic acids, and a catalyst containing molybdenum, antimony, bismuth, and iron, wherein an atom ratio of the antimony to the molybdenum on a surface of the catalyst is greater than an atom ratio of the antimony to the molybdenum in the entire catalyst is provided.

Abstract: An object of the present invention is to suppress performance deterioration of a molybdenum composite oxide-based catalyst at the time of performing gas-phase catalytic partial oxidation with molecular oxygen by using a tubular reactor. The present invention relates to a catalytic oxidation method using a tubular reactor in which a Mo compound layer containing a Mo compound and a composite oxide catalyst layer containing a Mo composite oxide catalyst are arranged in this order from a reaction raw material supply port side and under a flow of a mixed gas containing 75 vol % of air and 25 vol % of water vapor at 440° C., a Mo sublimation amount of the Mo compound is larger than a Mo sublimation amount of the Mo composite oxide catalyst under the same conditions.

Abstract: An object of the present invention is to suppress performance deterioration of a molybdenum composite oxide-based catalyst at the time of performing gas-phase catalytic partial oxidation with molecular oxygen by using a tubular reactor. The present invention relates to a catalytic oxidation method using a tubular reactor in which a Mo compound layer containing a Mo compound and a composite oxide catalyst layer containing a Mo composite oxide catalyst are arranged in this order from a reaction raw material supply port side and under a flow of a mixed gas containing 75 vol % of air and 25 vol % of water vapor at 440° C., a Mo sublimation amount of the Mo compound is larger than a Mo sublimation amount of the Mo composite oxide catalyst under the same conditions.

Abstract: Provided is a method for producing methacrolein and methacrylic acid which can improve yields of methacrolein and methacrylic acid. The method is to produce methacrolein and methacrylic acid through gas-phase contact oxidation of at least one raw material selected from the group consisting of isobutylene, TBA, and MTBE with molecular oxygen in the presence of a catalyst containing molybdenum, bismuth, and iron, using a fixed-bed reactor, in which, when a boundary temperature of activation energy of the oxidation reaction is denoted by TA (° C.), the reaction is started at a temperature lower than the reaction temperature TA (° C.), the reaction is controlled while increasing a reaction temperature such that a reaction rate of the raw material is kept constant, and the reaction is ended at a reaction temperature exceeding TA (° C.), and, when an average of rates of temperature increase until the reaction temperature reaches TA (° C.) is denoted by A (° C.