JPS5879545A - Calcining method for phosphorus-molybdenum catalyst - Google Patents

Abstract

PURPOSE:To provide a catalyst having high performance and uniform activity by treating a catalytic compsn. contg. no ammonium groups under the flow of a gas which is so regulated as to contain ammonia and/or steam at specific contents. CONSTITUTION:A catalyst system to be calcined is a compsn. contg. phosphorus and molybdenum, and is a compsn. obtd. in the state wherein ammonium groups have no connection in the stage of preparation. Such compsn. is treated under heating for 1-30hr at 300-500 deg.C in a gaseous atmosphere of 0.05-3% concn. of ammonia and/or steam in any of the cases of an ammonia-contg. gas, a steam- contg. gas or a gas contg. ammonia and steam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for calcination of a catalyst containing phosphorus, molybdenum and oxygen used in the gas phase catalytic oxidation of unsaturated aldehydes to produce the corresponding unsaturated acids. 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 gas-phase catalytic oxidation of acrolene or methacrylic acid.

Various catalysts have been proposed for gas-phase catalytic oxidation of unsaturated aldehydes, but catalysts containing phosphorus, molybdenum, and oxygen have shown relatively excellent performance. Some of the inventors also
No. 5014 and others proposed catalysts containing phosphorus, molybdenum, and oxygen. 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, and this is not necessarily sufficient from the viewpoint of industrial implementation.

The present inventors have conducted extensive research on a method for advantageously producing a catalyst having the above-mentioned composition that has high performance and high homogeneity, especially on an industrial scale. When poisoning, 300 ml of gas containing ammonia and/or water vapor in strictly controlled concentrations is
A high performance and highly homogeneous catalyst can be obtained by heat treatment at a temperature of ~500°C for 1 to several tens of hours, reversing the flow direction of the gas containing ammonia and/or water vapor if necessary. They discovered this and completed the present invention.

Accordingly, the present invention provides a method for calcination of a catalyst containing phosphorus, molybdenum, and oxygen for use in the vapor phase catalytic oxidation of unsaturated aldehydes to produce the corresponding unsaturated acids.

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, differences in activity occur between the catalysts, resulting in a catalyst with non-uniform performance, poor reproducibility, and difficult to calcinate on an industrial scale. , 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, 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 was found that this is because the catalyst composition of 2000 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, and found that
High performance and uniformity can be obtained by treating the catalyst composition Yanagi, which does not contain ammonium groups, obtained by a conventional method, under gas flow regulated to contain ammonia and/or water vapor in a total amount of 105 to 5%. They discovered that it can be made into a catalyst with high performance.

The catalyst system that can be subjected to calcination in the present invention is a composition containing phosphorus and molybdenum, and is a composition obtained in a state in which ammonium groups are not involved in the preparation process. These compositions contain phosphorus, molybdenum and oxygen and are free of ammonium groups, but can contain various elements that have catalytic activity or act as promoters. Such elements include potassium, rubidium,
Alkali metals such as cesium, alkaline earth metals such as magnesium, calcium, strontium and barium, Group B metals such as zinc and cadmium, arsenic, antimony, bismuth, copper, vanadium, tungsten, iron, manganese, tin, zirconium, Raw materials used in the preparation of O catalysts may include cobalt, nickel, selenium, niobium, tantalum, silica, aluminum, titanium, rhodium, cerium, germanium, lead, chromium, thallium, indium, palladium, silver, tellurium, etc. Substances are hydroxides, oxides,
It may be a salt, chloride, or free acid.

Examples of these include phosphoric acid, molybdic acid, phosphomolybdic acid, molybdenum trioxide, and the like. An example of the preparation method is as follows.

Molybdenum trioxide is dispersed in pure water and phosphoric acid is added to it for aging. If necessary, compounds of other elements such as arsenic acid, steel nitrate, vanadium pentoxide, etc. are added and evaporated to dryness with stirring. The cake is crushed and then compressed into tablets, or diluted with a cane diluent and molded. Alternatively, it may be supported on a suitable carrier. The obtained catalyst may be calcined as it is, or it can be treated at a low temperature and then calcined.

In the method of the present invention, in the case of an ammonia-containing gas, the ammonia concentration is preferably 105 to 5 tsl, particularly α05 to tsl. In the case of water vapor-containing gases or ammonia and water vapor-containing gases, a range of 105 to 5176 is preferred. In any case, if it is smaller than the above lower limit, the effect will be small and the catalyst will be non-uniform. Moreover, 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. Firing temperature is 500-500℃
, particularly preferably 300 to 450°C. The time required for firing varies depending on the firing temperature and the concentration of atmosphere or ammonia and/or water vapor, but it is 1 to several tens of hours, particularly 1 to 3 hours.
0 hours is preferred. For firing according to the present invention, commonly used equipment and furnaces are sufficient. Furthermore, in the method of the present invention, since the uniformity of the fired catalyst is maintained, the catalyst layer during firing can be made larger. For example, it can be carried out by filling a reactor with a total length of 5 to 6 inches. In this case, the direction of the gas may be reversed if necessary to further improve uniformity.

Acrolene or methachlorolene and molecular oxygen are used as raw material gases for producing the corresponding unsaturated acid by oxidizing an unsaturated aldehyde using a highly activated catalyst according to the present invention. Steam, nitrogen, carbon dioxide, etc. may be introduced as a diluent. In particular, the presence of water vapor has a favorable effect on improving the conversion rate of unsaturated aldehydes and the selectivity of unsaturated acids. The concentration of unsaturated aldehyde in the raw material gas can be varied within a wide range, but is between 1 and 20 v.
ol % is appropriate, particularly preferably 6 to 15 v
ol%. The oxygen concentration is preferably α3 to 4, particularly 0.4 to 5.2 in molar ratio to the unsaturated aldehyde.

The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature is 240
~390°C is suitable. The gas hourly space velocity varies depending on the reaction pressure and reaction temperature, but is suitably 300 to 100,001/#.

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.

Example 1 864 parts of molybdenum trioxide was dispersed in aooo parts of pure water. Add 115 parts of 85-phosphoric acid to this while stirring,
Next, an aqueous solution of 614 parts of copper nitrate and an aqueous solution of 1α0 part of chromium trioxide were added in this order. After further adding 599 parts of titanium oxide, the mixture was maintained at 70° C. for 3 hours while stirring. Finally, an aqueous solution of 114 parts of antimony trichloride in hydrochloric acid was gradually added, and the mixture was maintained for 30 minutes with stirring, followed by rapid evaporation to dryness. After drying at 150°C for 16 hours, the mixture was pulverized, additives and lubricants were added, and pressure molded.

The obtained molded product has an inner diameter of 27.5 tyv'm and a length of 1
After filling a stainless steel pipe of No. 111, the mixture was heated to 350° C. at a rate of 25° C./hour while passing 2000 t/'H of air containing ammonia of α25°, and then heat-treated for 8 hours. Next, the temperature was raised to iqo°C at a rate of 80°C/hour while passing air containing α09% ammonia at a rate of 500 L/′H, and the temperature was then maintained for 1 hour. Then, the direction of the gas was reversed and the heat treatment was continued for an additional hour. After cooling, divide it into 5 equal parts and take it out from the inlet side of the first gas flow.
■■. These ■■■■■ catalysts have an inner diameter of 16 s/
Fill each reaction tube of Q and add 4 volumes of methacrocin.
, 0chi, air 47.8%, water vapor 55-1 nitrogen cable 15-2
When the raw material gas of H was passed at a space velocity of 8001/'H and reacted at a reaction temperature of 355°C, the following values were obtained.

Comparative Example 1 The gas used for heat treatment in Example 1 was Q, 01ts.
The procedure was the same as in Example 1 except that the air containing ammonia was used.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the gas used for the heat treatment in Example 1 was changed to air containing 5-ammonia.

It can be seen that a catalyst can be obtained.

Example 2 627 parts of phosphomolybdic acid is dissolved in 3000 parts of pure water. Add to this 2 & 8 parts of 85 typhosphoric acid, 17.5 parts of chromium trioxide.
15.9 parts of vanadium pentoxide, and 666 parts of thallium nitrate were sequentially added and held at 70° C. for 3 hours with stirring. Added 81 parts of rhodium nitrate? 16 at 70℃
After aging for an hour, the carrier is added and evaporated to dryness. The resulting cake is dried at 150° C. for 16 hours, then crushed and pressure molded.

The obtained molded product has an inner diameter of 2″Z 5 tyv’m and a length of 3
The temperature was raised at 60°C/H while passing air containing water vapor CLsh into a reaction tube at a space velocity of 1000171.
Heat treatment was performed at 420°C for 2 hours.

Thereafter, the same procedure as in Example 1 was carried out. However, the reaction temperature is 550
℃, and the raw material gases were 4% methachlorenochloride, 58% air, and 58% water vapor.

Comparative Example 3 The same procedure as in Example 2 was carried out except that the gas used for the heat treatment in Example 2 was changed to air containing water vapor of a, 01-.

Comparative Example 4 The same procedure as in Example 2 was carried out except that the gas used for heat treatment in Example 2 was changed to air containing water vapor.

Example 3 2160 parts of molybdenum trioxide are dispersed in 17000 parts of pure water. To this, 144 parts of 85% phosphoric acid, 148 parts of 60% thiarsenic acid aqueous solution, 4 parts of copper 6α, 11 vanadium pentoxide.
4 parts and 244 parts of cesium nitrate were added in this order. 57.7 parts of tin oxide was added to the top bale, and the mixture was aged at 70°C for 4 hours with stirring, and then quickly evaporated to dryness. 1 at 150℃
After drying for 6 hours, it was pulverized, and about 35% was supported on a silica-alumina spherical carrier.

The obtained molded product was packed into a reaction tube with an inner diameter of 27.5 Jtl and a length of 3 cm (125 cm of ammonia and α8-
The temperature was raised to 300°C at a rate of 20°C/■ while passing air containing water vapor at a space velocity of 50001/H. After holding at the same temperature for 6 hours, the direction of the gas was reversed and the treatment was continued for 6 hours. Subsequently, the space velocity of the gas was decreased to 10001/i (10,001/i) and the temperature was increased to 670° C., and the temperature was maintained at the same temperature for 2 hours, after which the gas was returned to the initial direction and the treatment was continued for another 2 hours.

Thereafter, the reaction was carried out in the same manner as in Example 1. However, the reaction temperature was 515°C. The results were as follows.

Example 4 627 parts of phosphomolybdic acid is dissolved in 3000 parts of pure water. To this are added 14.4 parts of 85% + triphosphoric acid, 91 parts of vanadium pentoxide, 13.1 parts of germanium oxide, 107 parts of cesium nitrate and 116 parts of tungsten trioxide. After aging at 70°C for 8 hours, it was immediately evaporated to dryness. After drying at 150° C. for 16 hours, the mixture was pulverized, a lubricant and additives were added, and pressure molded.

The obtained molded product was packed into a reaction tube with an inner diameter of 27.56 cm and a length of 3 cm, and air containing tsl of water vapor was heated at a space velocity of 20 cm.
The temperature was raised to 400°C at a rate of 20°C/hour while supplying 00 lA, and held for 2 hours, and then further heated to 450°C and held at the same temperature for 2 hours for heat treatment.

Thereafter, the catalyst was removed and a reaction was carried out in the same manner as in Example 1. However, the reaction temperature was 340°C. The results were as follows.

Example 5 The same procedure as Example 4 was carried out except that acrolene was used instead of methachlorolene.

Claims (8)

[Claims] (1) Gas-phase catalytic oxidation of unsaturated aldehydes [50% of the catalyst containing phosphorus, molybdenum, and oxygen and containing no ammonium group used in the production of the corresponding unsaturated acids]
A method for firing a catalyst, characterized in that the catalyst is treated at a temperature of 0 to 500°C while flowing a gas containing 0.05 to 30% of ammonia and/or steam. (2) The catalyst firing method according to claim 1, characterized in that 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. (5) Catalyst! The method for firing the catalyst according to item 1, item 2, item 3, or item 4, wherein the heating rate to the firing temperature is 10 to b when the catalyst is fired at a temperature of 100 to 500°C. (6) The catalyst is phosphorus, molybdenum, alkali metals, oxygen and arsenic, antimony, bismuth, copper, vanadium, tungsten, iron, manganese, tin, zirconium, cobalt, nickel, zinc, selenium, cadmium, niobium, tantalum, magnesium, silicon, aluminum, titanium,
A catalyst comprising at least one selected from rhodium, cerium, calcium, strontium, germanium, lead, chromium, thallium, indium, palladium, silver, and tellurium and containing no ammonium group. Catalyst calcination method according to scope 1, 2, 3, 4 or 5. (7) A patent characterized in that the catalyst is a catalyst made of phosphorus, molybdenum, an alkali metal, oxygen, and at least one selected from arsenic, vanadium, tungsten, copper, iron, and tin, and does not contain an ammonium group. A catalyst firing method according to claim 1. (8) The catalyst is phosphorus, molybdenum, thallium, oxygen and arsenic, antimony, bismis, copper, vanadium, tungsten, iron, manganese, tin, zirconium, cobalt, nickel, zinc, selenium, cadmium, niobium, tantalum, magnesium, silicon. , aluminum, titanium,
5-dium, cerium, calcium, strontium,
Claims 1 and 2, characterized in that the catalyst is composed of at least one selected from kermanium%-lead, chromium, indium, palladium, silver, and tellurium, and does not contain ammonium groups. Catalyst calcination method according to item 5, item 4 or item 5.