Regenerating catalyst containing phosphorus and molybdenum-containing heteropoly acid compound, useful for producing methacrylic acid, comprises e.g. drying aqueous slurry, containing used catalyst, ammonium ion, nitrate ion and water

摘要

Regenerating a catalyst containing a phosphorus and molybdenum-containing heteropoly acid compound, comprises (a) drying an aqueous slurry containing a used catalyst, which is used for producing methacrylic acid, an ammonium ion, a nitrate ion and water to obtain a catalyst precursor, (b) carrying out a first calcining of the catalyst precursor in an atmosphere of an oxidizing gas, which contains moisture of 0.1-2.0 vol.%, at 360-410[deg] C, to obtain a product, and (c) carrying out a second calcining of the product in an atmosphere of non-oxidizing gas at 420-500[deg] C. An independent claim is also included for producing methacrylic acid comprising carrying out the above method, and subjecting the compound to a catalytic gas-phase oxidation reaction in the presence of the regenerated catalyst, where the compound contains methacrolein, isobutylaldehyde, isobutane and isobutyric acid.