Mitsubishi Rayon Company, Limited

Masanori Nitta

Toru Kuroda

Seiichi Kawato

Masahide Kondo

Hiroyuki Naitou

Hideyasu Takezawa

Toshihiro Satou

Mieji Sugiyama

Tomomasa Tatsumi

The present invention provides a (meth)acrylic acid-producing method capable of suppressing formation of carbides so that the production yield of (meth)acrylic acid is enhanced. In such a method, (meth)acrylic acid is produced through gas-phase catalytic oxidation reactions of (meth)acrolein by using molecular oxygen in a fixed-bed reactor configured to have a packed layer containing a packing material and a catalyst layer formed with a catalyst containing at least molybdenum and vanadium. The packed layer contains a packing material that has been used at least once for above gas-phase catalytic oxidation reactions, and the catalyst is present in the packed layer at 0.001&#x2dc;0.15 mass % of the total amount of the packing material.

Method for producing (meth)acrylic acid

Disclosed is a method for producing a catalyst, in which physical properties of a dried material or a calcined material in a production process of the catalyst are stable and a change in at least one of a catalyst activity and a selectivity to a target product is small and hence reproducibility of the catalyst is excellent. The present invention is a method for producing a catalyst containing molybdenum, bismuth, and iron, which contains the steps of washing a surface of at least one device equipped in an apparatus for the production of catalyst, to which a solid matter adheres, with a basic solution, and producing the catalyst with the apparatus for the production of catalyst thus washed.

Method for producing catalyst

Process for producing catalyst

In producing a catalyst used for synthesis of an unsaturated aldehyde and an unsaturated carboxylic acid by a gas-phase catalytic oxidation, there is used a step of packing an additive-containing catalyst precursor of the catalyst into a tubular reactor, passing a gas through the tubular reactor, and elevating, in this state, the temperature of the additive-containing catalyst precursor so that a temperature of the gas at an outlet of the catalyst precursor layer becomes higher than a temperature of the gas at an inlet of the catalyst precursor layer. The step makes possible easy and highly reproducible production of a high-performance catalyst which is small in the reduction in catalytic performance caused by, for example, the thermal decomposition of the additive contained in the catalyst precursor.

Reaction tube, process for producing catalyst and process for producing unsaturated aldehyde and unsaturated carboxylic acid

A molybdenum-based precipitate is prepared according to a process including the first step of forming a crude precipitate by pH adjustment to 6.5 or less in the presence of an alkali metal compound, and the second step of dissolving the crude precipitate in aqueous ammonia and forming a precipitate by pH adjustment to 6.5 or less. Then, the resulting molybdenum-based precipitate is washed with an acid aqueous solution having a pH of 6.5 or less and containing not less than 0.01 mole/L of ammonium root. Thus, a change in average particle diameter can be suppressed and good workability can be achieved, so that a molybdenum-based precipitate having a high purity and a desired average particle diameter can be obtained.

Method for producing precipitate and catalyst

The present invention relates to the effective utilization of a used catalyst containing at least molybdenum, an A element (at least one element selected from the group consisting of phosphorus and arsenic) and an X element (at least one element selected from the group consisting of potassium, rubidium and cesium), and provides a process for producing a catalyst, which comprises dispersing said used catalyst in water, adding thereto an alkali metal compound and/or ammonia solution, adjusting the resulting mixture to pH 6.5 or less to generate a precipitate containing at least molybdenum and the A element, and using the precipitate as a material for catalyst-constituting elements.

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Hiroshima, Japan

Masanori Nitta