JPS6345658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing acrylic acid or methacrylic acid by catalytically oxidizing a mixed gas containing acrolene or methachlorolene and molecular oxygen with a catalyst at high temperature in the vapor phase.

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
23013, 50-23014, etc., proposed catalysts containing phosphorus, molybdenum, and oxygen.

According to research conducted by the present inventors, a catalyst containing phosphorus, molybdenum, and oxygen, especially when calcined under air circulation, exhibits significantly higher activity than a catalyst calcined without air circulation. However, when calcination is carried out on an industrial scale, a difference in activity occurs between the catalyst at the inlet of the flowing gas and the catalyst at the outlet when calcination is carried out under air circulation. That is, if the inlet part has high activity, the outlet part will have low activity, and if the outlet part is set to have an appropriate activity, the catalyst in the inlet part will be over-calcined and deactivated.
In any case, it has been found that a catalyst having such non-uniform activity cannot be used on an industrial scale. This is because water vapor, ammonia nitrogen oxides, and other gases or gaseous substances are generated from the catalyst during calcination during catalyst preparation, so the catalyst composition during calcination is uniform from the inlet to the outlet of the gas flow. This is because they are exposed to an atmosphere that is not

When catalysts with different activities are used on a large scale industrially, a method is generally adopted in which the catalyst particles are mixed so that the aggregate of the catalyst particles appears uniform. The operation of mixing catalysts by such a method is very complicated, and in the case of a catalyst containing weak phosphorus and molybdenum, it is practically impossible to employ this method.

As a result of research into a method for industrially usable catalysts containing phosphorus, molybdenum, and oxygen, the present inventors found that the catalyst was packed into a reaction tube, and air or air containing ammonia and/or water vapor was introduced from one end. After firing at a temperature of 300 to 500°C while supplying , a reaction method is adopted in which a raw material gas containing acrolein or methacrolein (hereinafter referred to as unsaturated aldehyde) and molecular oxygen is supplied from the other end of the reaction tube. acrylic acid or methacrylic acid (hereinafter referred to as unsaturated acid) on an industrial scale.
The present inventors have discovered that the present invention can be produced with high yield and can be used for a long period of time, and have completed the present invention.

In the method of the present invention, after filling the reaction tube with the catalyst,
Since the firing is performed while supplying air, the catalytic activity after firing is large at the inlet and gradually decreases toward the exit. Since the raw material gas containing unsaturated aldehyde and molecular oxygen is in the opposite direction to the air during calcination, the raw material gas with a high concentration of unsaturated aldehyde is catalytically oxidized at a relatively low active part, and the concentration of unsaturated aldehyde is reduced. As it becomes smaller, it is catalytically oxidized with the catalyst in the highly active part, and the reaction amount is averaged. Therefore, unlike when catalyst particles with different activities are mixed and homogenized, highly active catalyst particles are not subjected to particularly severe conditions, and the reaction occurs on average over the entire catalyst layer, resulting in a higher yield. It brings good results for improvement of performance or long-term use.

The second feature of the present invention is that it is fired in a reactor. The fact that calcination can be performed in a reactor is very effective because in a catalyst system whose strength decreases with calcination, it can be filled before calcination, which increases the strength, thereby preventing the catalyst from becoming powder.

In the method of the present invention, it is possible to use an unfired shaped catalyst containing components attributable to raw materials that are dispersed by evaporation or decomposition. In order to reduce the diffusion resistance within the calcined catalyst particles, substances that can be removed by evaporation, decomposition, or combustion are added, the particles are molded, and the particles are filled into a reactor and heated or calcined, which can be applied to an industrial scale. It is also possible to reduce the decrease in yield of the desired product when expanding.

Catalysts that can be used in the present invention are catalysts for producing unsaturated acids by oxidizing unsaturated aldehydes containing phosphorus, molybdenum, and oxygen, including sodium,
Alkali metals such as potassium, cesium, and lithium, Group metals of the periodic table such as magnesium, calcium, strontium, barium, zinc, and cadmium, aluminum, thallium, indium, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, and nickel. , germanium, arsenic, selenium, zirconium, niobium, rhodium,
It also applies to materials containing one or more elements selected from palladium, tin, antimony, tellurium, tantalum, tungsten, copper, silver, lead, etc.

The raw material may be a hydroxide, oxide, salt, chloride, or free acid. 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. Add phosphoric acid aqueous solution to ammonium paramolybdate aqueous solution, and if necessary, add other elemental compounds such as arsenic acid, copper nitrate, ammonium metavanadate, germanium oxide, colloidal silica, etc., and then evaporate while heating and stirring. Dry until dry. Shape the cake after crushing it. If desired, a carrier may be added to the dry powder or to the slurry prior to dry powder. Furthermore, it is also possible to add substances that can be removed during the firing process, such as stearic acid.

After the catalyst thus obtained is filled into a reactor, it is fired while supplying air from one end.

The air used in the present invention may be dry air. However, the packing length of the catalyst packed in the reactor is large,
If the difference between the activity of the catalyst on the outlet side of the firing gas and the activity on the inlet side is too large, the effects of the present invention may not be fully exhibited. Favorable results are obtained using air containing .

The amount of air can be varied within a wide range, but an air velocity of 100 to 10,000 1/Hr is appropriate. The firing temperature varies slightly depending on the catalyst composition, but is 300 to 500℃.
Preferably it is 350-420°C. The time required for firing is preferably 1 to 50 hours, particularly 1 to 30 hours.

In producing an unsaturated acid by the method of the present invention, a raw material gas containing a corresponding unsaturated aldehyde is supplied from the other end of the reaction tube in a direction opposite to the direction of the air passed for calcination. As the raw material gas, a mixed gas of acrolene or methachlorolene and molecular oxygen, such as air, is used. Steam, carbon dioxide gas, etc. may be introduced as a diluent. In particular, the presence of water vapor has a favorable effect on improving the unsaturated aldehyde conversion rate and the unsaturated acid selectivity.

The unsaturated aldehyde concentration in the raw material gas is 1~
20vol% is appropriate, particularly preferably 3~
It is 15vol%. The oxygen concentration is preferably 0.3 to 4, particularly 0.4 to 3.2 in molar ratio to the unsaturated aldehyde. The reaction pressure can be varied from normal pressure to several atmospheres. The reaction temperature is suitably 240-390°C, particularly 250-350°C. The gas hourly space velocity varies depending on the reaction pressure and reaction temperature, but is suitably between 300 and 10,000 1/Hr.

The method of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. The conversion rate and selectivity are as follows.

Conversion rate (%) = Number of moles of unsaturated aldehyde reacted / Number of moles of unsaturated aldehyde supplied × 100 Selectivity (%) = Number of moles of unsaturated acid produced / Number of moles of unsaturated aldehyde reacted × 100 The parts are Parts by weight are shown.

Example 1 3000 parts of ammonium paramolybdate was dissolved in 10000 parts of pure water at 70°C. After adding and dissolving 82.7 parts of ammonium metavanadate, 85%
196 parts of phosphoric acid was added followed by 73.6 parts of germanium dioxide. Furthermore, 143 parts of potassium nitrate and 1700 parts of pure water
After dissolving 114 parts of ferric nitrate in 1000 parts of pure water, they were added in order, and the mixture was evaporated to solidify while stirring. It was dried at 130°C for 16 hours and then ground.
This powder was mixed with a lubricant and then pressure-molded.

After filling a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m, the temperature was raised to 380° C. at a rate of 40° C./H while supplying dry air at a space velocity of 10,001/H, and maintained at that temperature for 8 hours.

After completion of calcination, the temperature of the reactor was lowered to 270°C.
3.5% methachlorene, 47.8% air, water vapor by volume
The space velocity of the raw material gas with a composition of 20% and 28.7% nitrogen
After supplying air at 800 1/Hr in the opposite direction to that during firing, the temperature was gradually raised to 290°C. Methachlorolene conversion rate 85.1%, methacrylic acid selectivity 76.4%,
A single flow yield of methacrylic acid of 65.0% was obtained.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the raw material gas was supplied in the same direction as the dry air supply during firing in Example 1. As a result, the temperature of the catalyst layer near the raw material gas inlet became abnormally high, and there was a risk of deterioration of the catalyst and damage to the reactor, so the reaction was immediately stopped.

Comparative Example 2 The unfired catalyst obtained in Example 1 was heated in a firing furnace at a rate of 40°C/H while supplying dry air at a space velocity of 1000 1/H, and then fired at 380°C for 8 hours. After completion of calcination, it was taken out and filled into a reactor. The same raw material gas as in Example 1 was supplied at a reaction temperature of 290°C. However, even if the pressure was increased, the conversion rate did not increase, making it impossible to achieve the same reaction conditions as in Example 1. When the catalyst was taken out from the reactor, there were many pieces of catalyst that were broken into small pieces.

Example 2 3000 parts of ammonium paramolybdate was dissolved in 12000 parts of pure water at 60°C, and 196 parts of 85% phosphoric acid was added to this.
160 parts of a 50% arsenic acid aqueous solution was added, followed by 82.7 parts of ammonium metavanadate. Further, an aqueous solution in which 85.5 parts of copper nitrate and 276 parts of cesium nitrate were dissolved was added and held at 60°C for 2 hours with stirring, then 107 parts of tin oxide was added, and the resulting slurry was evaporated to dryness. After drying at 130°C for 16 hours, it was crushed and pressure molded.

The obtained molded product was packed into a reaction tube with an inner diameter of 27.5 m/m and a length of 6 m, and the temperature was raised at a rate of 30°C/H while supplying air containing 1.5% water vapor at a space velocity of 1500 1/H. It was baked at ℃ for 10 hours. After firing, the temperature is lowered and the volume is 3.5% methachlorene, 47.8% air,
When a raw material gas containing 48.7% water vapor was supplied at a space velocity of 800 1/H in the opposite direction to the air supplied during calcination, the conversion rate of methachlorolene was 87.8% at a reaction temperature of 300°C.
Methacrylic acid selectivity 85.0%, methacrylic acid yield
A result of 74.6% was obtained.

Comparative Example 3 The same procedure as in Example 2 was carried out except that the raw material gas was supplied in the same direction as the gas supplied during firing in Example 2. As a result, methachlorene conversion rate was 85.0%, methacrylic acid selectivity was 67.7%, and methacrylic acid single flow yield was
A score of 57.5% was obtained. The temperature of the catalyst layer at this time was measured and the results are shown in FIG. The vertical axis in FIG. 1 indicates temperature, and the direction of the arrow indicates the high temperature side. The horizontal axis represents the length direction of the catalyst layer filled in the reaction tube.
Part A represents one end of the catalyst filling part, and part B represents the other end. The firing gas was supplied in the direction of A→B, and the raw material gas was also supplied in the same direction of A→B. The solid line a shows the temperature of the catalyst layer, and the solid line b shows the reactor bath temperature at that time. As described above, it can be seen that in the reaction method of Comparative Example 3, the reaction mainly occurred in the catalyst section filled at the inlet of the raw material gas, and the entire catalyst was not utilized equally.

Example 3 After 3000 parts of ammonium paramolybdate was dissolved in 8000 parts of pure water heated to 70°C, 133 parts of ammonium metavanadate was added and dissolved. Then mix 163 parts of 85% phosphoric acid, then 101 parts of 60% arsenic acid, 171 parts of copper nitrate
143 parts of potassium nitrate, and 56.6 parts of titanium dioxide are mixed in this order. The mixture was maintained at a temperature of 70° C. for 3 hours with stirring and then evaporated to dryness. The resulting cake was dried at 130°C for 16 hours, then ground and pressure molded.

The obtained molded product was filled into a reaction tube with an inner diameter of 27.5 m/m and a length of 6 m, and dry air was blown at a space velocity of 3000 1/Hr.
The temperature was raised to 250° C. at a rate of 15° C./H while supplying water at a temperature of 15° C. and then held for 2 hours. Next, air containing 0.9% water vapor and 0.06% ammonia was heated at a space velocity of 1000.
Raise the temperature at a rate of 35℃/Hr while supplying at a rate of 1/Hr.
It was baked at 380°C for 12 hours.

The temperature was lowered to 270℃, and the raw material gas with a composition of 3.5% by volume, 47.8% air, and 48.7% water vapor was pumped at a space velocity of 800 1/
The temperature was gradually increased while supplying air in the opposite direction to the air supplied during calcination using Hr, and at a temperature of 295°C, values of 86.7% methachlorolene conversion, 82.8% methacrylic acid selectivity, and 71.8% methacrylic acid yield were obtained. . Continuing the reaction, after 720 hours, the methachlorene conversion rate
85.2%, methacrylic acid selectivity 84.1%, yield 71.6
%was gotten.

Example 4 3000 parts of ammonium paramolybdate was dissolved in 8000 parts of pure water heated to 70°C. then 85% phosphoric acid
After mixing 163 parts, 167 parts of a 60% arsenic acid aqueous solution was added. Additionally, 68.4 parts of copper nitrate, 113 parts of thallium nitrate,
After adding a mixed aqueous solution of 71.6 parts of potassium nitrate and 82.8 parts of cesium nitrate, 33.1 parts of ammonium metavanadate and then 41.3 parts of antimony trioxide were added and evaporated to dryness with stirring.

The resulting cake was crushed and supported on a silica-alumina carrier. After filling a reaction tube with a length of 3 m with the obtained catalyst, the temperature was raised at 25°C/Hr while supplying air containing 0.5% water vapor at a space velocity of 900 1/Hr.
It was baked at 380°C for 10 hours. The reaction was carried out in the same manner as in Example 3 except that the reaction temperature was 320°C, and the methachlorene conversion rate was 92.0% and the methacrylic acid selectivity was 86.0.
%, and a methacrylic acid yield of 79.1% was obtained.

Example 5 After dissolving 3000 parts of ammonium paramolybdate in 8000 parts of pure water heated to 70°C, 163 parts of 85% phosphoric acid,
201 parts of 60% arsenic acid was added. After stirring thoroughly,
Furthermore, an aqueous solution of 85.5 parts of copper nitrate and 71.6 parts of potassium nitrate was added and evaporated to dryness with stirring. The obtained cake was pulverized, a lubricant was added and mixed, and then pressure molded. The obtained molded product has an inner diameter of 27.5 m/m and a length of 3
Fill a reaction tube with dry air at a space velocity of 3000 m.
At a heating rate of 10℃/Hr while supplying at a rate of 1/Hr.
The temperature was raised to 270°C and held for 4 hours. Next, the supply of dry air was reduced to a space velocity of 1500 1/Hr, and the temperature was raised to 380°C at a heating rate of 25°C/H, followed by firing at the same temperature for 8 hours. When the reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 280°C, the methachlorene conversion rate was
85.8%, methacrylic acid selectivity 85.1%, yield 73.0
%was gotten.

Example 6 After 500 parts of ammonium paramolybdate was dissolved in 1000 parts of pure water, 66.2 parts of ammonium metavanadate was added and dissolved. Furthermore, an aqueous solution of 95.4 parts of ferric nitrate was added, followed by 33.6 parts of water glass. The mixture was rapidly evaporated to dryness while stirring, and then dried at 340°C for 2 hours. Thoroughly crush the obtained cake and add silica.
It was supported on an alumina carrier.

After filling a reaction tube with an inner diameter of 27.5 m/m and a length of 3 m, the obtained catalyst was heated to 360°C at a heating rate of 60°C/H while passing air containing 0.08% water vapor at a space velocity of 200 1/H. The temperature was raised and maintained for 2 hours.

Thereafter, the reaction was carried out in the same manner as in Example 5. However, using acrolene instead of methachlorolene,
The reaction temperature was 265°C and the space velocity was 500 1/H.
As a result, an acrolene conversion rate of 93.9%, an acrylic acid selectivity of 86.0%, and an acrylic acid yield of 80.8% were obtained.

[Brief explanation of the drawing]

The drawing shows the temperature distribution of the catalyst layer in the reaction of Comparative Example 3, where the vertical axis represents the temperature and the horizontal axis represents the length of the catalyst layer. a indicates the temperature of the catalyst layer, and b indicates the reactor bath temperature.

Claims (1)

[Claims] 1. When producing the corresponding acrylic acid or methacrylic acid by vapor phase catalytic oxidation of acrolein or methacrolein, a reaction tube is filled with a catalyst containing phosphorus, molybdenum and oxygen, and air is introduced from one end. A method for producing acrylic acid or methacrylic acid, which comprises firing at 300 to 500°C while supplying acrylic acid or methacrylic acid, and then supplying a raw material gas containing acrolein or methacrolein and molecular oxygen from the other end of the reaction tube. 2. The manufacturing method according to claim 1, wherein the air supplied during firing contains ammonia and/or water vapor. 3 Catalysts include phosphorus, molybdenum, oxygen and alkali metals, group metals of the periodic table, aluminum, thallium, indium, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, germanium, arsenic, selenium, zirconium, niobium , rhodium, palladium, tin, antimony, tellurium, tantalum, tungsten, copper,
3. The production method according to claim 1 or 2, wherein the catalyst comprises at least one selected from silver and lead.