Method for producing unsaturated aldehyde and/or unsaturated carboxylic acid

A method for producing an unsaturated aldehyde and/or an unsaturated carboxylic acid, the method comprising subjecting an alkene to gas-phase catalytic partial oxidation with molecular oxygen by using a multitubular reactor having a complex metal oxide catalyst filled therein, thereby obtaining a corresponding unsaturated aldehyde and/or unsaturated carboxylic acid, wherein

• two or more catalyst layers each containing a complex metal oxide catalyst are stuck in an axial direction of the tube, thereby achieving multilayer filling;
• a formulation of the complex metal oxide catalyst contained in one catalyst layer is different from a formulation of the complex metal oxide catalyst contained in at least one of other catalyst layers;
• a ratio of a component amount of bismuth to a component amount of molybdenum of the catalyst layer on the most gas inlet side in the tube axis is larger than a ratio of a component amount of bismuth to a component amount of molybdenum of the catalyst layer on the most gas outlet side in the tube axis;
• in all of the two catalyst layers adjacent to each other, a ratio of a component amount of bismuth to a component amount of molybdenum of the catalyst layer on the gas inlet side in the tube axis is equal to or larger than a ratio of a component amount of bismuth to a component amount of molybdenum of the catalyst layer on the gas outlet side in the tube axis;
• and
• the catalyst layer on the most gas outlet side in the tube axis contains a catalyst containing a compound represented by the following formula (1):
• Mo12BiaFebCocNidXeYfZgOh (1)
• wherein
• X is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), manganese (Mn), copper (Cu), zinc (Zn), cerium (Ce) and samarium (Sm);
• Y is at least one element selected from the group consisting of boron (B), phosphorus (P), arsenic (As), antimony (Sb), tungsten (W), silicon (Si) and aluminum (Al);
• Z is at least one element selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs);
• a to h represent atomic ratios of the respective components;
• a=0.40 or more and less than 0.80;
• b=1.0 to 2.5;
• c=3.0 to 7.5;
• d=2.0 to 3.5;
• e=0 to 10;
• f=0 to 10;
• g=0.01 to 1.0;
• h is expressed by a numerical value satisfying oxidation states of other elements;
• d/a is more than 2.5 and 8.8 or less;
• d/g is 2.0 or more and 350 or less;
• and a/g is 0.4 or more and less than 80.