| abstract |
The present invention provides a method capable of producing methacrylic acid continuously over a long period of time by subjecting methacrolein to vapor phase catalytic oxidation under conditions in which a decrease in catalytic activity is suppressed. A gas phase catalytic oxidation reaction of methacrolein is performed by supplying a raw material gas containing methacrolein, molecular oxygen and water vapor to a fixed bed reactor filled with a heteropolyacid catalyst containing phosphorus, molybdenum and vanadium. When producing methacrylic acid, the initial operation is carried out at a reaction temperature of 290 ° C. to 310 ° C., and then the steady operation is carried out at a reaction temperature of 270 ° C. to less than 290 ° C. [Selection figure] None |