JPS60209258A - Oxidation catalyst and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a heteropoly-acid comp. catalyst which is excellent in selectivity, yield, activity and catalytic strength for methacrylic acid by adding potassium or the like and copper, etc. to isolated molybdovanadophosphoric acid having rhombic system catalyst structure. CONSTITUTION:In an oxidation catalyst shown by the formula PaMobVcXdYe Of, molybdovanadophosphoric acid having rhombic system crystal structure which is manufactured under the existence of quinolines and/or quinoline derivatives is contained. (X is at least one or more kinds of elements selected among K, Rb, Cs, Ca, Sr and Ba, Y is at least one or more kinds of elements selected among Cu, Ag, As, Sb, Te, Co and Bi, (a)-(f) shown atomic ratio of each element respectively and when (b) is 12, a=0.1-3.0, c=0.1-6.0, d=0.05-6, e= 0.01-5.0 and (f) is value decided by the valence of each element and the atomic ratio.) The catalyst is excellent in selectivity, yield, activity and catalytic strength for methacrylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxidation catalyst and a method for its preparation. Specifically, the present invention relates to a heteropolyacid compound catalyst for producing methacrylic acid by catalytic gas phase oxidation of C4 aliphatic aldehydes or fatty acids such as methacrolein, isobutyraldehyde and isobutyric acid, respectively, and a method for preparing the same. .

Heteropolyacids exhibit strong acidity and act as oxidizing agents that easily oxidize other substances and are themselves reduced, but are easily reoxidized in the presence of an appropriate oxygen source, making them useful as catalysts for gas phase oxidation. has been highly evaluated, and research and development has been particularly active in recent years on molypdovanadric acid among heteropolyacid compounds.

Specifically, molypdovanadoline, a type of heteropolyacid compound, is used as a catalyst in the general process of producing methacrylic acid by gas-phase oxidation using either methacrolein, isobutyraldehyde, or isobutyric acid as a raw material. Many uses of acids have been proposed. Molypdovanadophosphoric acid is characterized by having strong oxidizing activity in gas phase oxidation, but on the other hand, because of its strong oxidizing power, sequential reactions in which the target product is further oxidized tend to occur and the target product is easily formed. It has the disadvantage that it is difficult to obtain products with good selectivity and high yield. Furthermore, from the point of view of producing practical catalysts, molypdovanadophosphoric acid has very poor catalyst formability and mechanical strength, and when various production methods to increase strength are used, the yield is reduced due to changes in the physical properties of the catalyst. It has been difficult to obtain a catalyst that is strong enough to withstand commercial use and has a sufficiently satisfactory yield.

A composition containing molypdovanadophosphoric acid or phosphorus-molybdenum as the main component and other elements added thereto is used as a catalyst, and a type selected from methacrolein, isobutyl-aldehyde, and isobutyric acid is used as a raw material. As an example of producing methacrylic acid through phase oxidation, there is
-15817, JP-A No. 49-95921, JP-A No. 4
9-126616, JP 50-82013, JP 52-62220, JP 52-122317,
JP-A-52-105113, JP-A-53-31615
No., JP-A-53-82715, JP-A-55-1003
No. 24, JP-A-56-15238, JP-A-50-23
No. 013, Special Publication No. 52-31327, Special Publication No. 53-1
It is reported in various publications such as No. 4052. However, the yield of methacrylic acid, which is the desired product, is low and is not satisfactory for industrial use.

Also, JP-A-57-12830, JP-A-57-177
No. 347-177348, JP-A-57-177343-
No. 177344 and other publications contain molypdovanadric acid.
Although a method for preparing a catalyst composition in the presence of a nitrogen-containing heterocyclic compound having a membered ring and/or a six-membered ring is disclosed,
When catalysts made by these methods are used, the yield of methacrylic acid is very high, but the space velocity of the raw material gas during the reaction is low, so the space-time yield of methacrylic acid is low. By the way.

The present inventors have conducted intensive research on the structure of molypdovanadophosphoric acid, its activity for producing methacrylic acid, its selectivity and catalytic strength, and the improvement in productivity required for industrial catalyst performance. As a result, potassium, rubidium, cesium, calcium, One or more elements selected from strontium and barium, as well as copper, silver, arsenic,
For example, when catalytic gas phase oxidation of methacrolein was carried out using a catalyst containing one or more elements selected from antimony, tellurium, cobalt, and bismuth, the selectivity, yield, and activity to methacrylic acid were significantly improved. It was discovered that the catalyst strength was greatly improved and productivity was improved, and a catalyst advantageous for gas phase oxidation and a method for preparing the same were completed.

That is, the present invention is specified as follows.

(1) An oxidation catalyst represented by the following general formula, which is characterized by containing free molybdovanadophosphoric acid having a cubic crystal structure.

PaMo, vcX, YeOf (where X is at least one element selected from potassium, rubidium, cesium, calcium, strontium, and barium, Y is copper, silver, arsenic, antimony, tellurium, cobalt, and bismuth) Indicates at least one element selected from
, c, d, e, f represent the atomic ratio of each element, and when b=12, a=0.1~3.0, 'c
= 0.1-6.0, d=0.05-6, preferably 0
．． 05-40, more preferably 0.1-3. O,e
= 0.01 to 5.0, f takes a value determined by the valence and atomic ratio of each element. ) (2) The method for preparing the catalyst according to (1) above, which is prepared in the presence of quinolines and/or quinolines derivatives.

The present invention will be explained in more detail below. The quinolines and their derivatives used in the present invention are compounds that form water-insoluble salts with molybdovanadratic acid and can be easily eliminated, such as sb, especially derivatives of these compounds. It is preferable to use the compound as a water-soluble inorganic salt such as a nitrate, sulfate, or hydrochloride.

Due to the decomposition reaction caused by the heteropolyacid during catalyst preparation, the desired salt cannot be obtained, and when nitrogen-containing heterocyclic compounds such as pyridine, piperazine, and pyrroline are used, similar insoluble Molybd/<natrate is formed, but the pore volume and specific surface area of the catalyst are insufficient, making it difficult to obtain sufficient activity to satisfy industrial performance at high space velocities. It has its drawbacks.

In preparing the catalyst of the present invention, various raw materials can be used.

Examples of molybdenum compounds include molybdenum trioxide, molybdic acid, sodium molybdate, ammonium paramolybdate, and molybdophosphoric acid.

Examples of vanadium compounds include vanadium pentoxide, ammonium metavanadate, sodium metavanadate, vanadyl oxalate, vanadyl sulfate, and the like.

Examples of the phosphorus compound include orthophosphoric acid, sodium hydrogen phosphate, ammonium phosphate, and ammonium heptaphosphate. Further, as the compounds of the X and Y components, hydroxides, oxides, nitrates, sulfates, carbonates, halides, oxyacids, etc. of the respective elements are used. Furthermore, metals can also be used as the Y component.

The effects of quinoline compounds in the preparation of molybdovanadratic acid in the present invention, for example, when quinoline is used, are as follows. The atomic ratio of P:M was prepared by a known method.

:V=1:11:1 Molybdovaranadophosphoric acid is an extremely water-soluble compound, and its crystal structure changes greatly depending on the crystal water it contains. That is, high water content (29 to 1 molecule of water per molecule of molybdovanadophosphate
30 molecules), a diamond-shaped structure with a lattice constant of 2 g and 5 It has a crystalline structure, and when measured by X-ray diffraction (α to the anticathode Cu-), the diffraction lines have 2θ of 7.9°, 8.9°, 9.
It is known that many angles are observed at angles such as 2", 26.8" and 27.1°.

When molypdovanadric acid is dissolved in water, it becomes a reddish-brown solution, but when an aqueous solution of quinoline nitrate is added to this, an orange-yellow precipitate is formed, and the supernatant becomes colorless and transparent. The presence of quinolinium ions was confirmed from the infrared absorption spectrum of this precipitate, and since there was no absorption attributed to quinoline, the reaction to produce quinolinium salt of molypdovanadophosphate was negative, and the reaction was due to the adsorption of excess quinoline. It is thought that there is no such thing. Although this precipitate is a salt with a monovalent base, X-ray diffraction measurements show that the structure at this stage does not have a cubic structure like alkali metal salts, ammonium salts, or pyridinium salts, and is extremely amorphous. It is believed that this difference in crystalline state contributes to the high activity of the obtained catalyst.

This observed precipitate was further heated at 300 to 600°C in a nitrogen stream.
When treated at a high temperature, the color changes to a dark blue reduced color, and when this is treated again in the air at a temperature in the range of 200 to 400°C, it changes to a yellow-green substance. In the measurement results of the infrared absorption spectrum of the substance, there was no absorption attributed to quinoline or quinolinium ions, and only the characteristic absorption of molybdo and vanadric acid was observed.

As a result of X-ray diffraction measurements, it was confirmed that the company had a cubic crystal structure with a lattice constant of 11.85. Unlike the crystal structure of quinolinium salt of pudopanadophosphate, it had a crystal structure similar to that of an alkali metal salt of molybdovanadophosphate.

The line width of the 7'c X-ray diffraction diagram was large, and it was confirmed that the substance consisted of extremely fine crystals.

Furthermore, the obtained substance is water-soluble, and after dissolving it in water, the aqueous solution was evaporated and dried, and X-ray diffraction was measured. Diffraction lines appeared and the crystal structure was close to the triclinic structure of free molypdovanadophosphate. From this, it was found that quinoline has the effect of changing the crystal structure of molypdovanadric acid to the cubic structure seen in its alkali metal salts and making the crystals finer. Similar effects were also observed when quinoline compounds other than quinoline and their rust conductors were used.

Next, the catalyst preparation method according to the present invention will be described by taking as an example the case where the catalyst is prepared using quinoline.Molypdovanadric acid found in a known method is dissolved in water, and an inorganic salt of quinoline (for example, nitric acid) is dissolved in water. quinoline, etc.) and add an aqueous solution,
Forms a precipitate that is insoluble in water. Alternatively, water-soluble compounds of molybdenum, sodium, and phosphorus are dissolved in water, an aqueous solution of an inorganic salt of quinoline is added, and the solution is made acidic to obtain a water-insoluble precipitate. From the absorption spectrum measurement results, it was recognized as a quinolinium salt of molybdovanadophosphoric acid, and this precipitate was found to be difficult to filter due to the aluminum and potassium gold-stripe salts and ammonium salts of molybdovanadophosphate found in known methods. Since the particles are larger than those of the conventional method, it can be easily passed through the filtration process, which is extremely advantageous in terms of catalyst preparation.

Using the thus found insoluble substance as a starting material, further
A compound of at least one element is added to each of the components and X component and molded to obtain a catalyst precursor.

Next, it is dried at a high temperature to remove volatile components contained in the hydrogen precursor. The temperature varies depending on the type and physical properties of volatile components, but is in the range of 100 to 300°C.

Further, during drying, it is preferable that the oxygen concentration in the atmosphere be 5 liters (volume concentration) or less in order to suppress the decomposition of volatile components.

This dried product is then further treated with an inert gas (e.g. nitrogen,
Quinoline is completely desorbed by heating in the range of 300 to 600°C under normal pressure or reduced pressure in an atmosphere of reducing gas (such as helium, argon, carbon dioxide gas, etc.) or reducing gas (e.g. carbon oxide, methane, ethane, propannatate). The catalyst is then activated in an air stream at a temperature of 200 to 400°C.

Alternatively, the above dried product is heated to a temperature in the range of 350 to 400°C from room temperature in an atmosphere in which air is diluted with an inert gas and the oxygen concentration is 5% (volume concentration) or less, and quinoline is desorbed and activated. may be used as a catalyst by simultaneously carrying out the reaction.

The crystal structure of the catalyst observed mainly consists of a coexistence of free molybdovanadophosphoric acid with a cubic structure and molybdovanadophosphate as the added component It is believed that molybdovanadophosphate or an oxide of the X component element is present.

This can be inferred from the following. In other words, when the added element is only the X component, when the X component is an alkaline earth metal, the X-ray diffraction measurement results indicate that it is free molypdovanadophosphoric acid with a cubic structure. , it has been revealed that it is a coexistence product with the molypdovanadophosphate of the added metal element, and when the X component is an alkali metal element, the molypdovanadophosphate has a cubic structure. Therefore, clear identification is difficult, but there is almost no X-ray diffraction pattern of free molybdovaranadophosphoric acid in the normal triclinic system. f of alkali metal salts of molypdovanadric acid separated by r
When the liquid was evaporated to dryness, a solid substance was obtained which was close to the amount calculated assuming that the soluble component was free molybdovanadophosphoric acid, and when X-ray diffraction measurements of this substance were performed, it was found that the free triclinic crystal structure was 20 specific to moripdopanadric acid is 8.9”, 9.2
Diffraction lines such as ＠, 26.8” were observed, and free molypdovanadophosphoric acid should exist based on the atomic composition. It is considered to be a coexistence of a salt of doric acid and the X component element.

In addition, when the added element is only the Y component, the X-ray diffraction measurement results indicate that molypdovanadophosphoric acid has a cubic structure, and that oxides of the added X component are also observed. This is known, and the above is the basis for the above speculation.

When these catalysts of the present invention are used in the production of methacrylic acid by gas phase oxidation, their selectivity and catalytic activity are extremely superior compared to catalysts that do not undergo #1 quinoline treatment. Not only is the specific surface area and pore volume large by using quinolines and their derivatives, but as a result, the resulting catalyst becomes more porous, has a smaller bulk specific gravity, and also has improved formability and mechanical properties. It was confirmed that the optical strength as well as the reproducibility during preparation were significantly improved.

If quinolines or their derivatives are used extensively during the preparation of the catalyst targeted by the present invention, it may be difficult to carry out settling and molding during the preparation.For example, even if a molding aid is added and molded, the catalyst strength Although the degree of pulverization is improved somewhat, on the other hand, the performance deteriorates so much that it cannot be used as a practical catalyst. Furthermore, when pyridine χ is used instead of quinolines or their derivatives, the catalyst performance and strength are improved, but the productivity required for industrial use is
In other words, the space-time yield is not satisfactorily high and is unsatisfactory from an economic point of view.

This fact shows how effective the use of quinolines and their derivatives are in the present invention.

These effects of the present invention are due to the interaction between the changes in the crystal structure of molypdovanadophosphoric acid as well as the surface and pore structure of the catalyst caused by quinolines and their derivatives, and the introduction of the X component and the X component element. This is considered to be a negative effect. As a result, the activity was increased, leading to the advantage that the yield upon release was dramatically increased.

These catalysts do not only have good performance, but also have good moldability and strong mechanical strength, so they can be used without a carrier, but when used in oxidation reactions, the heat removal effect in the catalyst layer is If considered, it is also possible to use a carrier. The carrier is generally an inert carrier such as silica, alumina,
Celite, silicon carbide, etc. are preferred, but are not limited to these.

In the preparation of the present invention, the quinolines and their derivatives may be added at the time mentioned above, or after adding the compound of each element ' of the X component and Y component to molybdovanadophosphoric acid, or It may be any stage in which all raw materials are mixed in an aqueous solution. The amount of quinolines and their derivatives used can be up to 10 times the mole of molypdovanadric acid, but is preferably in the range of 0.5 to 6 times the mole.

It is also possible to use quinolines and their derivatives in combination with other nitrogen-containing heterocyclic compounds such as pyridine.

The catalyst of the present invention is used in a gas phase oxidation reaction of a reaction gas containing methacrolein and/or inbutyraldehyde and/or inbutyric acid. Air is industrially advantageous as an oxygen source. As the diluent, for example, nitrogen, carbon dioxide, helium, an inert gas such as argon, -carbon oxide, water vapor, etc. can be used, but the use of water vapor is preferable in order to improve the yield.

The raw material concentration targeted in the oxidation reaction is 0.5 to 10
A range of capacitance is preferred. Further, the volume ratio of oxygen to the raw material is in the range of 0.5 to 1o, preferably in the range of 1 to 5. Space velocity of raw material gas is 500 to 10,000 hr
', preferably 1,000 to 5,000 h
A range of r- is appropriate.

In addition, the reaction temperature depends on the type of raw materials used, but it is 220~
The temperature range is 350°C.

When using the catalyst according to the present invention, a fixed bed type reactor is generally used, but either a fluidized bed type or a moving bed type can be used.

The preparation method of the catalyst according to the present invention and reaction examples using the same will be specifically explained below, and the conversion rate, selectivity, and single flow yield in Examples and Comparative Examples shall comply with the following definitions.

Example 1 Molybdenum trioxide 144. Of, vanadium pentoxide8.
27 t and phosphoric acid (85% by weight) to 1 t of water
1 and heated under reflux for 5 hours. The resulting dark red solution was filtered to remove a trace amount of insoluble solids, and then concentrated to dryness to give reddish brown crystals. According to the results of X-ray diffraction, fluorescent X-ray analysis, and infrared absorption spectroscopy, this crystal has an atomic ratio of P:Mo:V=1.09:1 excluding oxygen.
It was confirmed that this was molybdovanadophosphoric acid having a triclinic structure with a composition of 2:1.09. The observed crystals were dried, 81.7 F of them were dissolved in 100 ml of hot water, and a solution of 21.5 t of quinoline dissolved in 83.3 ml of an aqueous nitric acid solution with a concentration of 2N was added. A precipitate formed. This precipitate was filtered, washed with water, and then added with 4.0% cesium nitrate. Of and nitrate steel1. Add Of and mix well, mold into a cylinder with a diameter of 5111E% and a height of 5n, dry at 150'C, bake at 430℃ in a nitrogen stream for 4 hours, and then bake at 350℃ in an air stream for 3 hours. By this, the atomic ratio excluding oxygen is P:Mo:V
: Cs : Cu =1.09 : 12 : 1.
A catalyst oxide having a composition of 09:0.5:0.1 was obtained. This catalyst has good moldability and has a compressive fracture strength of 3
．． If it is more than 0 kg/pellet, the sufficient degree is 10.8 tr? /t, 0.35 ml/f and 0.81 f/cd. In the infrared absorption spectrum of this catalyst, no characteristic absorption of quinoline or quinolinium ions was observed, and only absorption characteristic of molypdovanadophosphoric acid was observed.

In addition, the measurement results by X-ray diffraction (Anticathode Cu-II, α) show that the amount of cesium is as low as 0.5 in terms of atomic ratio, and the atomic ratio composition indicates that more than 80% of free molypdovanadric acid exists. However, no diffraction lines characteristic of molybdovanadophosphoric acid with a triclinic structure with a 2θ of less than 10° were observed;
Only the diffraction lines attributed to the cubic system with θ of 10.5°, 18.3@, 260@, 30.2", etc., appear, and thus the free molybdovanadophosphoric acid in this catalyst is It is assumed that it has a cubic crystal structure.

Further, the resulting catalyst 10f was dispersed in water, and the P solution from which the insoluble cesium molypdovanadophosphate was removed was evaporated to dryness to obtain 8.5 tons of solid matter. When this substance was measured by X-ray diffraction, 20, which is characteristic of triclinic free molypdovanadric acid, was 8.9°, 9.2°, and 26.8°.
Diffraction lines such as @ were observed, and it was revealed that free molybdovanadophosphoric acid existed in the catalyst in an amount close to that estimated from the atomic composition.

This touch K 5 G ml is made of stainless steel with an inner diameter of 25 mm.
Filled into a tube and immersed in a molten salt bath at 280°C, methacrolein: oxygen: nitrogen: water vapor = 1: by volume was added into the tube.
3:36:10 raw material mixed gas space velocity 2000hr
” and obtained the results shown in Table 1.

Comparative Example 1 A catalyst was obtained in the same manner as in Example 1 except that copper nitrate was used. Using this catalyst, Example 1
The reaction was carried out under the same conditions as in Example 1, and the results are shown in Table 2.90 Comparative Example 2 A catalyst was obtained in the same manner as in Example 1, except that cesium nitrate was not used.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1, and the results shown in Table 2 were obtained.

Comparative Example 3 81.7 f of dried molypdovanadophosphoric acid obtained before adding quinoline in Example 1 was dissolved in 1 ood of warm water, and 4.0 f of cesium nitrate, 1.7 f of copper nitrate were added thereto. Of
A solution dissolved in 20ml of warm water was added, and the powder was further concentrated to dryness and ground, and the resulting powder was formed into a cylinder with a diameter of 5 wings and a height of 5 wings, and heated at 350°C in an air stream. The catalyst was calcined for 3 hours to obtain a catalyst.This catalyst was hygroscopic, had poor moldability, and had a poor compressive fracture strength of less than 1.oJ/pellet.

The specific surface area of this catalyst is 1.9 i/t s, the pore volume is 0.11 min, and the packing density is 1.5 f/IR1.
Compared to the catalyst found in Example 1, both the specific surface area and pore volume were extremely small, and the packing density was also significantly large.

Also, from X-ray diffraction, 20 is 7.9°, 8.9°, 9.2"
Diffraction lines due to free molybdopanadoric acid with a triclinic structure of 10° or less, and diffraction lines due to molybdovanadophosphate cesium salt with 2θ of 10.6 @ and 26.1° are observed, Thus, it was found that free molypdovanadric acid does not have a cubic structure when quinoline treatment is not performed.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1, and the results shown in Table 2 were obtained.

Comparative Example 4 A catalyst was obtained in the same manner as in Example 1 except that pyridine 13.6f was used instead of quinoline. The free molypdovanadophosphoric acid present in this catalyst was estimated to have a cubic crystal structure by X-ray diffraction analysis, with a specific surface area of 4.1 yj/fs and a pore volume of 0. 21m1/t1 packing density is x, xt
Compared to the catalysts of /door j and Example 1, both the specific surface area and pore volume were smaller, and the packing density was also larger.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1, and the results shown in Table 2 were obtained.

Example 2 The catalyst was prepared in the same manner as in Example 1, except that quinoline was replaced with isoquinoline, and the results shown in Table 1 were obtained.

Example 3 A catalyst was obtained in the same manner as in Example 1, except that methylquinoline was used instead of quinoline and the amount used was 23.9 f. Using this catalyst, the reaction temperature was set to 27
The reaction was carried out under the same conditions as in Example 1 except that the temperature was 0°C, and the results shown in Table 1 were obtained.

Example 4 88.3 t of ammonium paramolybdate and 5.3 t of ammonium metavanadate in 2001 Rg of heated water
was dissolved and stirred. Add phosphoric acid (85% by weight) to this solution.
Add 5.24 f, followed by 21.5 t of quinoline
When a solution prepared by dissolving this in 90 ml of a 10N aqueous nitric acid solution was added, an orange-yellow precipitate was formed. This was separated by f, and the resulting clay-like substance contained 4.22% of potassium nitrate and 1.4% of silver nitrate.
After adding 2 tons and mixing well, the diameter is 5 mm and the height is 51 RN.
It was molded into a cylindrical shape, dried at 200°C for 15 hours, baked at 430°C in a nitrogen stream for 4 hours, and then heated in an air stream for 350°C.
℃ for 3 hours, the atomic ratio excluding oxygen is P:Mo
: V : K : Person g = 1.09: 12:1.
A catalyst having a composition of 09:1:0.2 was obtained.

According to X-ray diffraction, this catalyst did not show any diffraction lines attributed to the triclinic system of free molybdovaranadophosphoric acid in which 20 is 101 or less. Vanadric acid is presumed to have a cubic crystal structure.

Except for using this catalyst and changing the reaction temperature to 290°C,
The reaction was carried out under the same conditions as in Example 1, and the results shown in Table 1 were obtained.

Comparative Example 5 A catalyst was prepared in the same manner as in Example 4, except that pyridine 13.61F was used instead of quinoline. The reaction was carried out under the same conditions as in Example 1 except that this catalyst was used and the reaction temperature was changed to 290°C, and the results shown in Table 2 were obtained.

Example 5 Molybdenum dioxide 72f1 Vanadium pentoxide 5,68
f and phosphoric acid (85% by weight) 5.76 t to water 50
0i/ and heated under reflux for 5 hours to dissolve.

To this solution was added a solution of 21.5 f of quinoline dissolved in 83.3 ttrl of an aqueous solution of nitric acid with a concentration of 2N, and then an aqueous solution of 5.12 f of rubidium hydroxide and 0.88 t of strontium nitrate dissolved in warm water from SOMZ and tellurium. 4.78 f of acid was added, and the mixture was heated and concentrated while stirring. The resulting clay-like substance was molded into a cylindrical shape with a diameter of 5nφ and a height of 5ill, dried at 200°C, and then heated in a nitrogen stream for 430°C.
℃ for 4 hours, followed by 3 hours of calcination at 400℃ in a stream of air, resulting in an atomic ratio of P:Mo:V excluding oxygen.
: Rb : 8r : Te= 1.2 : 12
A catalyst with a composition of : 1.5 : 1.2 : 0.1 : 0.5 was obtained.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was 280°C, and the results shown in Table 1 were obtained.

Examples 6 to 9 According to the preparation method of Example 5, quinoline or inquinoline was used, the amounts of vanadium pentoxide and phosphoric acid used were varied, and the compounds of component X were potassium, rubidium, cesium, and calcium. By using nitrates of , strontium, and barium, and nitrates of copper, silver, cobalt, and bismuth, orthoarsenic acid, antimony trioxide, and telluric acid as the X component, the composition shown in Table 3 was obtained. A catalyst was prepared. Using these catalysts, the reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was changed, and the results shown in Table 3 were obtained.

Examples 10 to 13 According to the preparation method of Example 4, quinoline or isoquinoline was used, the amounts of ammonium metavanadate and phosphoric acid used were varied, and as the compound of X component, potassium, rubidium, calcium, strontium, Catalysts with the compositions shown in Table 3 were prepared by using each nitrate of barium, and each nitrate of copper, silver, cobalt, and bismuth, orthoarsenic acid, antimony trioxide, and telluric acid as the compound of X component. . Using these catalysts, the reaction was carried out under the same conditions as in Example 1, except that the reaction temperature was changed, and the results shown in Table 3 were obtained.

Example 14 Using the same catalyst as in Example 1, the reaction was carried out under the same conditions except that the raw material methacrolein was replaced with isobutyraldehyde. The conversion of isobutyraldehyde was 100% and the single flow yield of methacrylic acid was 69.5%. A single flow yield of methacrolein of 10.5% was obtained. (
Table 4) Comparative Example 6 Using the catalyst of Comparative Example 3, a reaction was carried out under the same reaction conditions as in Example 14, and the conversion rate of isobutyraldehyde was 93.1%, the yield of methacrylic acid was 40.2%, and the yield of methacrolein was 40.2%. A yield of 21.5% was obtained. (Table 4) Example 15 50ml of the catalyst of Example 1 was placed in a stainless steel tube with an inner diameter of 25 mm.
It was filled into a tube and immersed in a 280°C molten salt bath, and the volume ratio of imbutyric acid:oxygen:nitrogen:steam=1:1:2 was added to the tube.
2:1 raw material gas is passed at a space velocity of 3000 hr',
Isobutyric acid conversion rate 100%, methacrylic acid selectivity 82.3
A single flow yield of methacrylic acid of 82.3% was obtained.

(Table 4) Comparative example 7

Claims (2)

[Claims] (1) An oxidation catalyst represented by the following general formula, which is characterized by containing free molybdovanadophosphoric acid having a cubic crystal structure. P aMo B VCX, I Y, O ((where X is at least one selected from potassium, rubidium, cesium, calcium, strontium,
Y represents at least one element selected from copper, silver, arsenic, antimony, tellurium, cobalt and bismuth, and the subscripts a, b, c, d
, e and f each represent the atomic ratio of each element, and b = 1
2, a=0.1~3.01c=0.1~6.
0, d=0.05-6, e=0.01-5.0, and f takes a value determined by the valence and atomic ratio of each element. ) (2) A method for preparing a catalyst according to claim (1), which is prepared in the presence of quinolines and/or quinolines derivatives.