JP2592325B2 - Method for producing unsaturated carboxylic acid - Google Patents

Description

The present invention relates to a process for producing unsaturated carboxylic acids by using a specific catalyst in the gas phase catalytic oxidation of unsaturated aldehydes.

[Conventional technology]

Hitherto, many proposals have been made regarding a method and a catalyst for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas phase catalytic oxidation. In particular, since the discovery of heteropolyacid catalysts as methacrolein oxidation catalysts, a number of patents have been submitted for their improvement.
No. 74142, JP-A-60-239439, Japanese Patent Application No. 63-172369, etc., but the reaction results are not sufficient, the catalyst activity is significantly reduced with time, and the nitrogen-containing heterocyclic compound or Since various other compounds are used, they have drawbacks such as complicated post-treatment, and at present, further improvement is desired when used as an industrial catalyst.

[Object of the invention]

An object of the present invention is to provide a method for advantageously producing an unsaturated carboxylic acid from an unsaturated aldehyde.

[Means for solving the problem]

The present invention relates to a method for producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen to produce an unsaturated carboxylic acid, wherein P _a Mo _b V _c Ce _d La _e X _f Y _g Z _h O _i (wherein P , Mo, V, Ce, La and O are respectively phosphorus, molybdenum, vanadium, cerium, lanthanum and oxygen, X
Is at least one element selected from the group consisting of copper, zinc, bismuth, chromium, magnesium, silver, tantalum, nickel, manganese, barium and calcium, Y is arsenic, antimony, zirconium, boron, germanium, tellurium and gallium Z is at least one element selected from the group consisting of potassium, rubidium, cesium and thallium; a, b, c, d, e, f, g, h And i indicate the atomic ratio of each element, and when b = 12, a = 0.5-3 and c = 0.0
1-3, d = 0.01-2, e = 0.01-2, f = 0.01-3,
g = 0.01-3, h = 0.01-2, and i is the number of oxygen atoms necessary to satisfy the valency of each component described above.) This is a method for producing an acid.

The present invention is characterized in that cerium and lanthanum are used in combination in a catalyst containing phosphorus, molybdenum, vanadium and other specific elements. Since the catalyst used in the present invention has a high activity, a sufficient unsaturated carboxylic acid yield can be achieved even at a lower reaction temperature, and as a result, a high catalyst activity is maintained over a long period of time. The value is extremely high. The effect of the combined use of cerium and lanthanum on the catalyst is not strictly clear, but is presumed to have provided an ideal oxidation-reduction balance.

The unsaturated aldehyde used as a raw material for the reaction of the present invention is acrolein, methacrolein and the like, and the unsaturated carboxylic acid obtained is acrylic acid, methacrylic acid and the like.

The method for producing the catalyst used in the present invention does not need to be limited to a special method. Unless accompanied by significant uneven distribution of components, conventionally well-known evaporation-drying method, precipitation method, oxide mixing method. And various other methods can be used.

As a raw material for preparing the catalyst, nitrates, carbonates, ammonium salts, halides and the like of each element can be used in combination. For example, as a molybdenum raw material, ammonium paramolybdate, molybdenum trioxide, molybdenum chloride and the like can be used, and as a vanadium raw material, ammonium metavanadate, vanadium pentoxide, vanadium chloride and the like can be used.

The catalyst used in the method of the present invention may be free of a carrier, may be supported on an inert carrier such as silica, alumina, silica / alumina, silicon carbide, or may be diluted with the carrier before use.

In carrying out the present invention, the concentration of the unsaturated aldehyde in the raw material gas can be changed in a wide range,
20% is appropriate, and particularly preferably 3 to 10%. The starting unsaturated aldehyde may contain a small amount of impurities such as water and lower saturated aldehyde, and these impurities do not substantially affect the reaction.

Although it is economical to use air as the oxygen source, air enriched with pure oxygen can be used if necessary. The oxygen concentration in the source gas is defined by the molar ratio to the unsaturated aldehyde, and this value is preferably from 0.3 to 4, particularly preferably from 0.4 to 2.5. The source gas may be diluted by adding an inert gas such as nitrogen, steam, or carbon dioxide.

The reaction pressure is preferably from normal pressure to several atmospheres. Reaction temperature is 23
Can be selected in the range of 0 ~ 450 ℃, especially 250 ~ 400 ℃
Is preferred. The reaction can be carried out in a fixed bed or a fluidized bed.

〔Example〕

Hereinafter, a method for preparing a catalyst according to the present invention and a reaction example using the same will be specifically described.

In Examples and Comparative Examples, the conversion of unsaturated aldehyde and the selectivity of unsaturated carboxylic acid to be formed are defined as follows.

The parts in the following examples are parts by weight, and the analysis was performed by gas chromatography.

Example 1 100 parts of ammonium paramolybdate, 2.76 parts of ammonium metavanadate and 4.77 parts of potassium nitrate were added to 30 parts of pure water.
Dissolved in 0 parts. A solution prepared by dissolving 8.16 parts of 85% phosphoric acid in 10 parts of pure water was added thereto, and 4.13 parts of antimony trioxide was further added. The mixture was heated to 95 ° C. while stirring. Then copper nitrate 1.14
, Cerium oxide (1.62 parts) and lanthanum oxide (1.54 parts) to which pure water (30 parts) was added, and the mixture was evaporated to dryness while heating and stirring. The obtained solid was dried at 130 ° C. for 16 hours, molded under pressure, and heat-treated at 380 ° C. for 5 hours in an air stream, and used as a catalyst.

The composition of the elements other than oxygen in the obtained catalyst (the same _applies hereinafter) was P _1.5 Mo ₁₂ V _0.5 Ce _0.2 La _0.2 Cu _0.1 Sb _0.6 K ₁ .

This catalyst is filled in a reaction tube, and methacrolein 5%, oxygen
A mixed gas of 10%, water vapor 30%, nitrogen 55%, (volume%) was passed at a reaction temperature of 270 ° C and a contact time of 3.6 seconds. The product was collected and analyzed by gas chromatography. As a result, the methacrolein conversion was 89.6% and the methacrylic acid selectivity was 87.8%.

Examples 2 to 12 Each of the catalysts shown in the following table was prepared according to Example 1, and
The reaction was carried out under the same conditions as described above. The results are shown in the table.

Comparative Example 1 Comparative catalyst P _1.5 Mo ₁₂ V _0.5 Cu _0.1 Sb _0.6 K according to Example 1
₁ was prepared and reacted under the same reaction conditions as in Example 1 using this catalyst. The reaction rate of methacrolein was 80.5%,
The methacrylic acid selectivity was 80.1%.

Comparative Example 2 Comparative catalyst P _1.5 Mo ₁₂ V _0.5 Ce _0.2 Cu _0.1 S according to Example 1
b _0.6 K ₁ was prepared and reacted under the same reaction conditions as in Example 1 using this catalyst.
% And methacrylic acid selectivity of 88.0%.

Example 13 Using the catalyst prepared in Example 1, acrolein 5%,
When a mixed gas of 10% oxygen, 30% steam and 55% nitrogen (volume%) was introduced into the catalyst at a reaction temperature of 270 ° C and a contact time of 3.6 seconds, the reaction rate of acrolein was 92.5% and the selectivity of acrylic acid was 94.6%.
%.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-239439 (JP, A) JP-A-5-122934 (JP, A) JP-A-61-5043 (JP, A) JP-A-62 161739 (JP, A) JP-A-61-7233 (JP, A) JP-A-58-65240 (JP, A) JP-A-53-51194 (JP, A) JP-A-51-115416 (JP, A)

Claims (1)

(57) [Claims] (1) In producing an unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas-phase catalytic oxidation with molecular oxygen to produce an unsaturated carboxylic acid, a general formula P _a Mo _b V _c Ce _d La _e X _f Y _g Z _h O _i (wherein P, Mo, V, Ce, La and O are respectively phosphorus, molybdenum, vanadium, cerium, lanthanum and oxygen, X
Is at least one element selected from the group consisting of copper, zinc, bismuth, chromium, magnesium, silver, tantalum, nickel, manganese, barium and calcium, Y is arsenic, antimony, zirconium, boron, germanium, tellurium and gallium Z is at least one element selected from the group consisting of potassium, rubidium, cesium and thallium; a, b, c, d, e, f, g, h And i indicate the atomic ratio of each element, and when b = 12, a = 0.5-3 and c = 0.0
1-3, d = 0.01-2, e = 0.01-2, f = 0.01-3,
g = 0.01-3, h = 0.01-2, and i is the number of oxygen atoms necessary to satisfy the valence of each component described above.) Method for producing carboxylic acid.