JPH0215255B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to phosphorus, which is used when producing a corresponding unsaturated acid by vapor phase catalytic oxidation of an unsaturated aldehyde,
This invention relates to a method for calcination of a catalyst containing molybdenum and oxygen. More specifically, the present invention relates to a method for firing a catalyst containing phosphorus, molybdenum, and oxygen used when producing acrylic acid or methacrylic acid by vapor phase catalytic oxidation of acrolene or methachlorolene. Conventionally, various catalysts have been proposed for gas phase catalytic oxidation of acrolene or methachlorolene, but catalysts containing phosphorus, molybdenum, and oxygen have shown relatively excellent performance. Some of the inventors also published phosphorus in Japanese Patent Publications No. 50-23013 and No. 50-23014.
A catalyst containing molybdenum and oxygen was proposed. When the above catalysts are prepared under specific conditions, the activity and selectivity of the desired product are significantly improved. However, the reproducibility of performance is insufficient, and as the scale of production increases, the variation in performance increases.
This was not always sufficient from the point of view of industrial implementation. The present inventors conducted intensive research on a method for producing the above-mentioned catalyst with high performance and high homogeneity, especially when producing it on an industrial scale, and as a result, a catalyst composition obtained by a known method was obtained. When activating ammonia and/or water vapor at a temperature of 300 to 500°C for 1 to several tens of hours under a gas flow containing ammonia and/or water vapor at a strictly controlled concentration, if necessary, the ammonia or water-containing gas The present inventors have discovered that a high-performance and highly homogeneous catalyst can be obtained by reversing the flow direction of the catalyst and completing the present invention. Accordingly, the present invention provides a method for calcination of a catalyst containing phosphorus, molybdenum, and oxygen used in producing acrylic acid or methacrylic acid by gas-phase catalytic oxidation of acrolene or methachlorolene. The present invention will be explained in detail below. Catalysts containing phosphorus and molybdenum are active in a variety of preparations, as shown in the references cited above. In particular, catalysts calcined under air circulation often exhibit significantly higher activity than catalysts calcined without air circulation. However, in this calcination, as the amount of catalyst increases, the difference in activity between the catalysts occurs, resulting in a catalyst with non-uniform performance, poor reproducibility, and difficulty in calcination on an industrial scale. can be,
Improvements were awaited. Therefore, the present inventors conducted various studies in order to elucidate the mechanism of activity expression and the cause of the non-uniformity of activity in the calcination of a catalyst containing phosphorus, molybdenum and oxygen. As a result, non-uniformity in catalytic activity is caused by the generation of water vapor, ammonia, nitrogen oxides, and other gases or gaseous substances from the catalyst due to decomposition of raw material salts when the catalyst is fired through gas such as air. It has been found that this is because the catalyst composition therein is exposed to a non-uniform atmosphere from the inlet to the outlet of the gas flow. Based on these facts, the present inventors researched methods for uniformly firing catalysts on an industrial scale from various angles. They have discovered that a catalyst with high performance and highly uniform performance can be obtained by treating the catalyst under gas flow that is regulated to contain a total amount of 0.05 to 3%. Catalyst systems that can be subjected to calcination in the present invention are compositions containing phosphorus and molybdenum, and systems in which ammonia or ammonium groups are involved in the preparation process. For example, when preparing a catalyst from a raw material compound of a catalyst by evaporation to dryness method, coprecipitation method, or oxide mixing method, if ammonia or ammonium group does not exist in the raw material, ammonia or ammonium group may be added. It is a composition obtained by preparing the slurry in the presence of a base and drying the obtained slurry. The catalyst calcination method of the present invention can be applied to catalysts containing various elements in addition to phosphorus, molybdenum, and oxygen. Examples of elements that can be contained include alkaline earth metals, arsenic, antimony, bismuth, copper, vanadium, tungsten, iron, manganese, tin, zirconium, cobalt, nickel, zinc, selenium, cadmium, niobium, tantalum, and silicon. , aluminum, titanium, rhodium, cerium, germanium, lead, chromium,
Examples include thallium, indium, palladium, silver, and tellurium. The raw materials used to prepare the catalyst include hydroxides, oxides, salts, chlorides,
Any free acid may be used. Examples of these include phosphoric acid, molybdic acid, phosphomolybdic acid, ammonium molybdate, ammonium phosphomolybdate, molybdenum trioxide, and the like. An example of the preparation method is as follows. A phosphoric acid aqueous solution is added to an ammonium molybdate aqueous solution, and if necessary, other elemental compounds such as arsenic acid, copper nitrate, ammonium metavalidate, etc. are added, and then evaporated to dryness with stirring to dry.
The cake may be crushed and then molded into tablets, or it may be diluted with a diluent and molded. Alternatively, it may be supported on a suitable carrier. The obtained catalyst may be calcined as it is, or it may be calcined after being heat treated at a temperature of 340° C. or less. In the method of the present invention, in the case of ammonia-containing gas, the ammonia concentration is 0.05 to 3%, particularly 0.05 to 1.5%.
is preferred. In the case of water vapor-containing gases or ammonia and water vapor-containing gases, a range of 0.05 to 3% is preferred. In any case, if it is smaller than the above lower limit, the effect will be small and the catalyst will have non-uniform activity. In addition, even if it is larger than the above-mentioned upper limit, the activity of the catalyst obtained after heat treatment will be non-uniform, and the activity will be insufficiently expressed as a whole. The firing temperature is 300~500℃, especially 300~
420°C is preferred. The time required for firing depends on the firing temperature,
Although it varies depending on the atmosphere or its concentration, it is preferably 1 to several tens of hours, particularly 1 to 30 hours. For firing according to the present invention, commonly used equipment and furnaces are sufficient. Furthermore, according to the method of the present invention, a highly homogeneous catalyst can be obtained, so that the size of the catalyst layer during firing can be increased. For example, total length 5~
It can also be carried out by filling a 6 m reactor or the like. In this case, the direction of the gas may be reversed if necessary to improve uniformity. When producing acrylic acid or methacrylic acid by oxidizing acrolene or methacrolene using the highly activated catalyst according to the present invention, a mixed gas of acrolene or methachlorolene and molecular oxygen, such as air, is used as a raw material gas. is used. Steam, nitrogen, carbon dioxide gas, etc. may be introduced as a diluent. In particular, the presence of water vapor has a favorable effect on improving the acrolene or methacrolene conversion rate and the selectivity of acrylic acid or methacrylic acid. The acrolene or methachlorolene concentration in the raw material gas can be varied within a wide range, but is 1 to 20 vol.
% is suitable, particularly preferably 3 to 15 vol%
It is. Oxygen concentration is the molar ratio to acrolene
0.3-4, particularly 0.4-3.2 is preferred. The reaction pressure is preferably from normal pressure to several atmospheres. Reaction temperature is 240-390℃,
A temperature of 270 to 340°C is particularly suitable. The gas space velocity varies depending on the reaction pressure and reaction temperature, but is 300 to 10,000/
H is appropriate. The method of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. In the following, parts represent parts by weight, and conversion rates and selectivities are as follows. Conversion rate (%) = Number of moles of acrolene or methacrolene reacted / Number of moles of acrolene or methacrolene supplied × 100 Selectivity (%) = Number of moles of acrylic acid or methacrylic acid produced / Number of moles of acrolene or methacrolene reacted × 100 Example 1 3000 parts of ammonium paramolybdate was dissolved in 8000 parts of pure water at 70°C, and an aqueous solution of 163 parts of 85% phosphoric acid and 147 parts of a 60% arsenic acid aqueous solution was added thereto. The mixture was heated with stirring to evaporate to dryness, and was further dried by keeping it at 130° for about 16 hours. The resulting cake was crushed and molded. 0.06vol% after filling 660 parts of the obtained molded product into a stainless steel pipe with an inner diameter of 27.5m/m and a length of 1m.
While passing through 1000/h of air containing ammonia
After raising the temperature to 380°C at a rate of 80°C/hour and holding it for 2 hours, the flow direction was reversed and heat treatment was performed for an additional 4 hours.
After cooling, it was divided into 5 approximately equal parts and taken out, starting from the inlet side of the first gas flow. Each of these catalysts was packed into a reaction tube with an inner diameter of 16 m/m, the furnace temperature was kept at 280°C, and the raw material gas with a volume composition of 5% methachlorolene, 47.8% air, 20% water vapor, and 27.2% nitrogen was heated at a space velocity of 1000/m. The reactants were reacted by feeding them with H. The results are shown below.

[Table] Comparative example 1 In Example 1, the gas used for heat treatment was 0.01
The same procedure as in Example 1 was carried out except that the air containing % of ammonia was used.

[Table] As a result, it can be seen that large variations in activity and selectivity occur in the calcination of a large amount of catalyst. Comparative example 2 5% of the gas used for heat treatment in Example 1
Example 1 except that the air containing ammonia was changed to
I did the same thing.

[Table] Example 2 3000 parts of ammonium paramolybdate was dissolved in 14000 parts of pure water at about 60°C. After 41.3 parts of ammonium metavanadate was added and dissolved, 163 parts of 85% phosphoric acid and then 73.6 parts of germanium dioxide were added. Furthermore, add 143 parts of potassium nitrate to 1,700 parts of pure water.
57.2 parts of ferric nitrate was dissolved in 600 parts of pure water and added, and the mixture was evaporated to dryness with heating and stirring.
After drying at 130°C for 16 hours, it was crushed, mixed with a lubricant, and molded. After filling this into a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m, 1000/H of air containing 0.5% water vapor was added.
from 100°C to 385°C at a heating rate of 25°C/H.
After the temperature was raised, the temperature was maintained for 4 hours, and then the direction of the gas was reversed and the treatment was continued for 4 hours. After cooling, the catalyst was divided into five approximately equal parts and taken out from the inlet side of the first gas flow. Each of these catalysts was packed into a reaction tube with an inner diameter of 22 m/m. Thereafter, the reaction was carried out under the same reaction conditions as in Example 1.
However, the reaction temperature was 300℃, 4% methachlorolene,
60% air and 36% water vapor.

[Table] Comparative Example 3 The gas used for heat treatment in Example 2 was 0.01
The same procedure as in Example 2 was carried out except that the air containing % of water vapor was used.

[Table] Comparative Example 4 In Example 2, the gas used for heat treatment was 5.0
The same procedure as in Example 2 was carried out except that the air containing % of water vapor was used.

[Table] Example 3 500 parts of molybdenum trioxide, 63.3 parts of antimony trioxide, and 17.4 parts of chromium trioxide were added to 200 parts of pure water. After adding a mixed aqueous solution of 17.5 parts of copper nitrate and 29.3 parts of potassium nitrate, the mixture was stirred. Mix 66.7 parts of 85% phosphoric acid. After maintaining the temperature at 50°C for 3 hours with sufficient stirring, 80 parts of 28% aqueous ammonia was gradually added.
After keeping for another 2 hours, it is evaporated to dryness. The resulting cake was dried at 150°C for 16 hours, then ground and molded. This was filled into a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m, and the temperature was raised to 390°C at a rate of 65°C/H while passing air containing 0.05% ammonia and 0.85% water vapor at a rate of 1500°C/H. After holding for 1 hour, the direction of the gas was reversed and the heat treatment was further carried out for 3 hours. Thereafter, the same extraction as in Example 2 was carried out and a reaction was carried out. However, the reaction temperature is 310℃ and the space velocity is 700/H.
And so.

[Table] Example 4 3000 parts of ammonium paramolybdate was dissolved in 14000 parts of pure water at about 70°C. 163 parts of 85% phosphoric acid was added to this and stirred. Further, 147 parts of a 60% arsenic acid aqueous solution was added with stirring. An aqueous solution of 34.1 parts of copper nitrate, a mixed aqueous solution of 43.0 parts of potassium nitrate, and 193 parts of cesium nitrate were added. While stirring the above liquid, 49.6 parts of ammonium metavanadate was added, and finally 41.3 parts of antimony trioxide was added. It was evaporated to dryness while stirring. The resulting cake was dried at 130° C. for 16 hours and then ground. Approximately 30% of this powder was supported on a silica-alumina spherical carrier. The obtained catalyst was packed into a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m. Air 1000 containing 0.8% water vapor
/H is supplied while increasing the temperature at a temperature increase rate of 25℃/H.
It was baked at 380°C for 8 hours. After the temperature had cooled, it was divided into five parts and taken out from the air supply side. After each of the obtained catalysts was filled into a reaction tube with an inner diameter of 16 m/m, 4.0% methachlorolene, 47.8% air, 15% water vapor, and 33.2% nitrogen were added while keeping the bath temperature at 295°C.
Space velocity of feed gas with composition (percent by volume)
When it was supplied at a rate of 600/H, the following results were obtained.

[Table] Comparative Example 5 Example 4 was carried out in the same manner as in Example 4, except that the gas supplied during firing was changed to air containing 1% ammonia and 4% water vapor. As a result, the following values were obtained.

[Table] Example 5 After dissolving 500 parts of ammonium paramolybdate in 1000 parts of pure water, 82.8 parts of ammonium metavanadate was added and dissolved. Furthermore, an aqueous solution of 47.7 parts of ferric nitrate was added, followed by an aqueous solution of 21.0 parts of water glass, and the mixture was quickly evaporated to dryness. the resulting cake
It was dried at 340°C for 2 hours and then ground. Then, about 30% was supported on a silica-alumina carrier. The obtained catalyst was packed into a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m, and then heated to 370°C at a rate of 70°C/H while passing air containing 0.5% water vapor at a space velocity of 300/H. Heat treatment was performed for a certain period of time. Thereafter, the samples were taken out and reacted in the same manner as in Example 1. However, acrolene was used instead of methachlorolene, and the reaction temperature was 270°C.

【table】

Claims (1)

[Claims] 1. A catalyst containing phosphorus, molybdenum and oxygen, which is used in the gas phase catalytic oxidation of unsaturated aldehydes to produce the corresponding unsaturated acids, and in which ammonia or ammonium groups are involved in the preparation process. ~500℃
A method for calcination of a catalyst, which is characterized in that, when calcination is carried out at a temperature of . 2. The catalyst firing method according to claim 1, wherein the gas is air. 3. The catalyst calcination method according to claim 1 or 2, characterized in that the calcination is carried out in a reaction tube for gas phase catalytic oxidation of unsaturated aldehydes. 4. The catalyst firing method according to claim 1, 2, or 3, characterized in that the direction of gas flow is reversed during firing.