JP2778055B2 - Method for producing vanadium-phosphorus crystalline oxide or catalyst containing same - Google Patents

Description

The present invention relates to a method for producing a vanadium-phosphorus crystalline oxide or a catalyst containing the same. More specifically, the present invention relates to a vanadium-phosphorus crystalline oxide which is useful as an active substance exhibiting a catalytic action and a specific solid acidity on a maleic anhydride production reaction by gas-phase oxidation of a hydrocarbon having 4 or more carbon atoms and a precursor thereof. And a method for producing a catalyst containing each of these crystalline oxides.

[Conventional technology]

In recent years, research on vanadium-phosphorus composite oxides has progressed,
It is known that there are a very wide variety of crystalline compounds, including differences in the valences of the vanadium and phosphorus atoms. In particular, as an active component of a catalyst for producing maleic anhydride by vapor-phase oxidation of a paraffinic or olefinic hydrocarbon having 4 carbon atoms such as butane and butene, or a catalyst having a specific solid acidity, the following Table B A vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown below (hereinafter, referred to as a fired body oxide) is known.

The structure of the calcined oxide is (VO) ₂ P ₂ O by X-ray structure analysis
₇ , that is, divanadyl pyrophosphate (E. Bordes and P. Coutine, J. Catal., 57 , 236-252 (1.
979)).

Although various methods for producing a fired body oxide are known, the following Table A
Is advantageous in that a vanadium-phosphorus crystalline oxide (hereinafter, referred to as a precursor oxide) having a main X-ray diffraction peak shown in (1) is calcined and produced.

When the precursor oxide is calcined, it releases and transfers water of crystallization at a temperature of 500 ° C. or less and is converted into divanadyl pyrophosphate, ie, a calcined oxide (E. Bordes et al, Mater. Sc)
i.Monograph, 28B , 887-892 (1985)). [This is the reason why the former is called a precursor oxide and the latter is called a fired oxide. ] And X-ray structural analysis is made also precursor _{oxide, (VO) HPO 4 · 1} / 2H 2 O (JWJohnson et al, J.Am.Che
m. Soc., 106 , 8123-8128 (1984)), or (VO) ₂ H ₄ P ₂
O ₉ (CCTORardi et al, Inorg.Chem., 23 , 1308-1310 (1
984)).

In the case where the calcined oxide is produced using the precursor oxide as a starting material, the structure of the precursor oxide, and thus the conditions for producing the precursor oxide, greatly affect the physical properties and activity of the calcined oxide.

Conventionally, various methods for producing a precursor oxide have been proposed, and these are roughly classified into an organic medium method in which a crystal formation reaction is performed in an organic medium having a low moisture concentration, and an aqueous medium. This is considered to be an aqueous medium method for performing a crystal formation reaction. Specifically, the following method has been proposed.

First, as an organic medium method, a method in which vanadium pentoxide is added to a non-corrosive organic liquid such as isobutanol, reduced by heating under reflux, phosphoric acid is added, the generated solid is separated, and dried by heating (US Patent No. 4,132,670).

A method of producing vanadyl phosphate using a pentavalent vanadium compound and orthophosphoric acid as starting materials and phosphorous acid and an alcohol as a vanadium reducing agent (JP-A-56-141840).

A method of boiling a pentavalent vanadium compound in an organic medium such as alcohol, reducing, adding phosphoric anhydride, and azeotropically dehydrating with benzene (US Pat. No. 4,283,288).

And the like.

Further, as an aqueous medium method, a pentavalent vanadium compound is dissolved in a non-oxidizing acidic solution, reacted with phosphoric acid, and then a salt of the generated soluble vanadium-phosphorus complex is precipitated by adding water, Drying method (JP-A-51-95990).

A vanadium compound is reacted with phosphoric acid to form a vanadium-phosphorus complex, which is contacted with an acid stronger than phosphoric acid to recover only an effective precursor, and furthermore, soluble phase E is dissolved in water or another solvent. A method in which the purity is improved by extracting and removing the components (JP-A-53-146992).

A method of contacting a pentavalent vanadium compound with a trivalent phosphorus compound to form a phosphorus-vanadium-based precursor containing at least 50 atomic% of vanadium in a tetravalent state (JP-B-53-2631).

Forming an aqueous oxide slurry of a pentavalent vanadium compound and a mineral acid-free inorganic reducing agent, mixing the pentavalent phosphorus compound with the chiller to prevent substantial evaporation of water in the chiller; A method of heating at a temperature of at least 120 ° C. under a self-generated pressure, followed by removing water and drying
3).

A method of reacting a pentavalent vanadium compound with phosphoric acid in an aqueous medium in the presence of hydrazine or hydroxylamine hydrochloride (JP-A-56-45815).

After dissolving vanadium pentoxide in an aqueous medium in the presence of an inorganic reducing agent such as phosphoric acid, hydrazine and hydroxylamine to form a homogeneous solution containing tetravalent vanadium ions, a temperature of 110 to 250 ° C. Hydrothermal treatment within the range (JP-A-58-151313).

And the like.

When industrially producing a precursor oxide, it is preferable that a non-corrosive atmosphere can be used and that problems such as combustible material treatment and waste treatment can be avoided. From this viewpoint, the aqueous medium method, particularly the above-mentioned method, is considered to be an industrially advantageous method.

[Problems to be solved by the invention]

As described above, the aqueous medium method is generally considered to be superior from the viewpoint of industrial implementation, but not necessarily from the viewpoint of the physical properties of the obtained crystalline oxide. That is, according to the findings of the present inventors, the precursor oxide obtained by the aqueous medium method or the calcined oxide obtained by calcining the precursor oxide,
Compared with the precursor oxide obtained by the organic medium method or the calcined oxide obtained by calcining the precursor oxide, generally, the specific surface area is small, and undesired phenomena such as excessive growth of the primary particle diameter are likely to occur. Having.

The present inventors have studied in detail the crystallinity of the crystalline oxide produced by various methods, and in the case of any of the crystals generated in the aqueous medium, a highly developed plate-like,
Some of these are agglomerated particles, but the crystals formed in an organic medium such as isobutanol are fine flake crystallites, especially when the water concentration in the organic medium is maintained at a low level. It turned out to be an aggregate. According to the findings of the present inventors, the specific surface area, which is considered to have a close relationship with the catalytic activity, particularly in terms of physical properties, is always recognized to be larger in the organic medium method than in the aqueous medium method, and the catalytic activity tends to be larger. There is.

However, on the other hand, the organic medium method involves consuming a large amount of industrially expensive organic solvents, handling of combustibles, by-products of highly corrosive reduction products, and further reducing the crystal purity. There are many problems.

[Means for solving the problem]

In view of the problems of the conventional method described above, the present inventors have conducted intensive studies on a method for improving the disadvantages of the synthesis method while maintaining the advantages of the synthesis method in an aqueous medium. The inventors have found that it is effective to make a specific seed crystal exist in a medium, and have reached the inventions of the present application.

That is, the gist of the first invention of the present application is that vanadium-phosphorus having a main X-ray diffraction peak shown in the above-mentioned Table A, which is synthesized by a reaction in an aqueous medium and obtained by pulverization treatment as a seed crystal. In the presence of fine crystals of a systemic crystalline oxide (that is, a precursor oxide) having an average particle size of 3 μm or less, a tetravalent vanadium compound and a pentavalent phosphorus compound are mixed in an aqueous medium. Reacting under heating to form a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in Table A (i.e., a precursor oxide); Manufacturing method.

The gist of the second invention of the present application is a method for producing a vanadium-phosphorus-based crystalline oxide-containing catalyst, which comprises molding the precursor oxide obtained according to the first invention into a catalyst shape, Exists.

Further, the gist of the third invention of the present application is that a precursor oxide obtained by the above first invention is calcined and a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in Table B ( That is, a method for producing a vanadium-phosphorus crystalline oxide characterized by producing a calcined oxide).

Further, the gist of the fourth invention of the present application is a method for producing a vanadium-phosphorus-based crystalline oxide-containing catalyst, wherein the calcined oxide obtained by the third invention is shaped into a catalyst, Exists.

 Hereinafter, each invention of the present application will be described in detail.

The formation of the precursor oxide in the method of the present invention, that is, the vanadium-phosphorus crystalline oxide having the main X-ray diffraction peaks shown in Table A above, was carried out in an aqueous medium by using a tetravalent vanadium compound and a pentavalent phosphorus. The reaction is carried out by an aqueous medium method in which the compound is reacted under heating.

As a vanadium raw material, in addition to tetravalent compounds, pentavalent,
Various compounds such as trivalent can be used. Specifically, oxides such as vanadium dioxide, vanadium pentoxide, and vanadium trioxide; acids of vanadium such as vanadic acid and metavanadic acid and salts or esters thereof; vanadium phosphates such as vanadyl phosphate; Organic salts or mineral salts containing vanadyl ions such as vanadyl acid and vanadyl chloride; vanadium halides such as vanadium chloride; Practically, a pentavalent vanadium compound such as vanadium pentoxide is preferably used. In this case, a tetravalent vanadium compound is generated in situ from the pentavalent vanadium compound by using a reducing agent in combination. Examples of the reducing agent include a low-valent vanadium compound such as vanadium trioxide; a low-valent raw material compound itself such as a low-valent phosphorus compound such as phosphorous acid, metaphosphorous acid, and phosphorus trioxide; And hydrazine, hydroxylamine, and metal powder; and organic reducing agents such as oxalic acid, lactic acid, ascorbic acid, and hydroquinone. Of these, non-halogen inorganic reducing agents such as hydrazine and hydroxylamine are preferred.

As the phosphorus material, phosphorus acids such as phosphoric acid, pyrophosphoric acid, tripolyphosphoric acid and metaphosphoric acid, or esters thereof, or pentavalent phosphorus compounds such as phosphorus pentoxide are usually used. Also, various phosphonium compounds can be used in combination. When a pentavalent vanadium compound is used as a raw material, 3
The oxidation-reduction reaction may be performed using a valent phosphorus compound, for example, phosphorous acid, phosphorus trioxide, or the like, and as a result, the state may be converted to a state in which tetravalent vanadium and pentavalent phosphorus coexist.

Water is generally used as the aqueous medium. If desired, a hydrophilic organic solvent such as alcohol, carboxylic acid, ether, and ketone can be used in combination.However, the combined use of a large amount of the organic solvent also impairs the industrial advantage of the aqueous medium method described above, When a pentavalent vanadium compound such as vanadium pentoxide is reacted with a reducing agent to generate a tetravalent vanadium compound in situ, the reduction rate of vanadium is reduced. It should be less than 50% by weight, preferably less than 10% by weight.

The above-described vanadium raw material, phosphorus raw material, and, if necessary, a reducing agent are mixed in an aqueous medium, and reacted under heating to generate a precursor oxide. The type of reaction is not particularly limited, but a hydrothermal treatment method in which heating is performed in a closed vessel is preferable.

Now, in the method of the present invention, the precursor oxide is synthesized as a seed crystal in the aqueous medium during the production of the precursor oxide by the above-described aqueous medium method by a reaction in the aqueous medium, and pulverized to an average particle diameter of 3 μm or less. The crystal formation process of the precursor oxide is controlled by the presence of the thus obtained fine crystals of the precursor oxide. As a result, it is possible to produce a precursor oxide of a fine crystal close to a fine flake, which has been conventionally obtained only in an organic medium as described above.

In the aqueous medium method, it is known to add a seed crystal pulverized during the hydrothermal treatment in the above method, but little is known about a suitable form of the seed crystal and an effect of adding the seed crystal.

The mechanism of action of the specific seed crystal during the crystal formation process is not fully understood. Conventionally, in the process of crystallization accompanying the change in solubility among the processes involving crystal precipitation, a method is generally used in which a seed crystal having the same crystal structure as the target crystal is present and a crystal having the same structure is grown around the crystal. Has been adopted. However, the production process of the vanadium-phosphorus crystalline oxide targeted by the present invention is a system in which a complicated chemical reaction accompanied by dehydration condensation proceeds, and is different from a mere crystallization process. By presenting a specific seed crystal according to the present invention, a specific crystal in a group of vanadium-phosphorus crystalline oxides that is originally extremely complex is generated to improve the chemical purity, and the particle size of the obtained crystal is improved. Is kept very small, the shape of the crystalline oxide finally obtained,
Unexpected effects such as improvement in physical properties and catalytic activity are exhibited.

In the method of the present invention, the fine crystals of the precursor oxide to be present in the aqueous medium at the time of generation of the precursor oxide are produced by finely pulverizing the precursor oxide synthesized by the aqueous medium method. As the aqueous medium method, various methods as described above can be adopted, and among them, the above method is preferable. The method of finely pulverizing the synthesized precursor oxide is not particularly limited, either a dry method or a wet method can be adopted, but a wet method is preferably used. As the pulverizing device, for example, a suitable mechanical pulverizing device such as a hammer mill, a jet mill, a colloid mill, and a sand grinder can be used.

The pulverization treatment is performed so that the average particle diameter of the seed crystal is 3 μm or less, preferably 2 μm, in order to ensure the same physical properties of the crystalline oxide produced by the conventionally known organic medium method.
μm or less, more preferably 1 μm or less, particularly preferably
It is performed so as to be 0.5 μm or less. When a crystal formation reaction is performed using this, a crystalline oxide having extremely excellent catalytic activity can be generated.

The method for producing the precursor oxide fine crystals in an aqueous medium solution containing a tetravalent vanadium compound and a pentavalent phosphorus compound for producing a precursor oxide is not particularly limited, and aqueous The precursor oxide synthesized by the medium method may be preliminarily pulverized as described above to form fine crystals, and may be added to the aqueous medium solution, for example, in the form of an aqueous slurry, or may be added to the aqueous medium method. The aqueous slurry obtained by adding the precursor oxide having a relatively large particle diameter synthesized in the above aqueous medium solution is pulverized as described above to form fine crystals of the precursor oxide in situ. It may be generated.

The amount of the fine crystals of the precursor oxide used as the seed crystal is usually about 1 to 25 wt%, preferably about 3 to 20 wt%, more preferably about 5 to 20 wt%, based on the theoretical amount of the precursor oxide to be formed. It is about 10 wt%. The theoretical amount of the precursor oxide to be generated is calculated from the amount of the charged vanadium raw material and assuming a 100% yield.

As described above, the formation of the precursor oxide according to the method of the present invention is preferably performed by a hydrothermal treatment method. The four cases will be described more specifically as follows. That is, raw material compounds such as a vanadium raw material, a phosphorus raw material, and a reducing agent are mixed and reacted in an aqueous medium to produce an aqueous medium solution containing a tetravalent vanadium compound and a pentavalent phosphorus compound. The P / V atomic ratio in this aqueous medium solution is usually 0.90-1.2
It is adjusted to be about 5 and preferably in the range of 1.00 to 1.20. In this aqueous medium solution, an appropriate amount of seed crystals is made to exist by an appropriate method as described above to form an aqueous slurry, which is heated and subjected to hydrothermal treatment. The hydrothermal treatment is preferably carried out by heating in a closed vessel at a temperature of usually 110 to 250 ° C, preferably 140 to 200 ° C, usually for 0.2 to 12 hours, preferably for 1 to 8 hours.

When a tetravalent vanadium compound and a pentavalent phosphorus compound are reacted under heating in an aqueous medium as described above, an aqueous slurry containing the target precursor oxide containing grayish blue crystals is obtained. The precursor oxide can be obtained as a solid by evaporating the aqueous slurry to dryness, drop drying or spray drying on a heated surface, or excessively or centrifuging the aqueous slurry.

The precursor oxide obtained by the method of the present invention may be a hydrocarbon having 4 or more carbon atoms such as butane, butene, 1,3-butadiene or the like as a catalyst itself, or as an active component of the catalyst, or as a precursor thereof. It is suitably used for the production of maleic anhydride by gas phase oxidation of.

For example, the precursor oxide itself can be used as a fixed-bed catalyst by shaping the precursor oxide itself into pellets or other catalysts, optionally using a shaping aid. In addition, the precursor oxide as an active component can be used as a fixed bed catalyst by molding into a pellet or other catalyst shape using a carrier and other auxiliary components, if necessary, together with a molding aid, if necessary. When catalyzed in the form of the precursor oxide in this way, the obtained catalyst is usually 400 to 600 ° C. in a kiln type, a muffle furnace type, or other calciner or reactor.
Calcined at about the temperature, and activated by being converted to a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in Table B, that is, a calcined oxide,
Used for reaction. As the firing atmosphere, an inert gas such as nitrogen or argon; air; air diluted with an inert gas; air containing butane, butene, or the like is preferably used. The activation by baking can be performed outside the reactor by using a suitable baking furnace.

When the precursor oxide is fired, a fired oxide is obtained as described above. The firing temperature is usually from 350 to 800 ° C, preferably from 400 to 600 ° C. The firing atmosphere is the same as described above for the firing of the precursor oxide-containing catalyst.

The resulting calcined oxide itself is used as a catalyst or as an active component of the catalyst, butane, butene, production of maleic anhydride by gas phase oxidation of hydrocarbons having 4 or more carbon atoms such as 1,3-butadiene, Or olefin isomerization reaction,
It is suitably used for reactions utilizing solid acidity such as olefin hydration reaction, alcohol dehydration reaction, ether synthesis reaction, cracking reaction, paraffin skeletal isomerization reaction, and Prince reaction.

For example, the calcined oxide itself can be used as a fixed-bed catalyst by shaping it into pellets or other catalysts, optionally using a forming aid in combination. Further, the calcined oxide can be used as a fixed bed catalyst by molding into a pellet or other catalyst shape by using the calcined oxide as an active component, together with a carrier or other auxiliary components, if necessary, together with a molding aid, if necessary. In the case of the catalyst containing the calcined oxide as described above, activation may be performed by the same calcination as in the case of the precursor oxide-containing catalyst.

Maleic anhydride can be produced by subjecting a hydrocarbon to gas phase oxidation using the catalyst obtained by the method of the present invention. The raw material is a hydrocarbon having 4 or more carbon atoms, preferably a linear aliphatic hydrocarbon having 4 carbon atoms. Specifically, for example, n-butane, 1-butene, 2-butene, 1,
Examples include 3-butadiene or mixtures thereof. Branched aliphatic hydrocarbons having 4 carbon atoms, such as isobutane and isobutylene, produce maleic anhydride at lower yields. The most economically advantageous raw materials are n- butane and butenes, typically as a C ₄ fraction obtained by separation or naphtha cracking or FCC reaction from natural gas, also extracted therefrom butadiene and isobutylene if desired Used as the remaining mixture. In these cases, hydrocarbons having 3 or 5 carbon atoms are usually mixed as impurities, but there is no particular problem. These starting hydrocarbons are catalytically oxidized in the gas phase in the presence of the above-mentioned catalyst to obtain anhydrous anhydride. Produces maleic acid. As the oxidizing agent, a molecular oxygen-containing gas, usually air, is used. The raw material hydrocarbon is usually 0.1 to 8% (vol) as the concentration in the air, more preferably
The catalyst layer is oxidized by being introduced into the catalyst layer together with or separately from air at a ratio of about 1.0 to 4.5%. The reaction temperature is usually in the range of 300 to 550 ° C, more preferably 350 to 500 ° C, and the reaction pressure is usually higher than normal pressure, more preferably 0.1 to 1
The range is 0 kg / cm ² G.

〔Example〕

Next, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Example-1 (1) Synthesis of precursor oxide for seed crystal 100 ml of water was placed in a beaker having a volume of 500 ml, and 85% of the water was placed therein.
24.22 g of H ₃ PO ₄ and 2.58 g of 98% hydrazine hydrate were added and heated to 60-80 ° C. with stirring. 18.20 g of 99% V ₂ O _{5 was} added into the above solution little by little while paying attention to foaming, and the entire amount was completely dissolved. The solution was concentrated to a total amount of 98 g, transferred to a fluororesin beaker, and heated in a sealed pressure vessel at 150 ° C. for 8 hours to produce a precursor oxide slurry. After cooling, the slurry was dropped on a hot plate heated to about 150 ° C. and dried to obtain a dry powder of a precursor oxide.

The resulting precursor oxide had the main X-ray diffraction peaks shown in Table A above, and the particle size was about 3 μm.

(2) Production of precursor oxide in the presence of seed crystal 100 ml of water was placed in a beaker having a volume of 500 ml, and 85%
24.22 g of H ₃ PO ₄ and 2.58 g of 98% hydrazine hydrate were added and heated to 60-80 ° C. with stirring. 18.20 g of 99% V ₂ O _{5 was} added into the above solution little by little while paying attention to foaming, and the entire amount was completely dissolved. This solution was concentrated to a total volume of 98 g.

As a seed crystal, 3.4 g of the precursor oxide synthesized in the above (1) (10% of the theoretical amount of the precursor oxide to be formed) was added.
%) And mixed to form an aqueous slurry. This slurry was charged into a wet pulverizer and pulverized at room temperature for 3 hours. When the particle size of the seed crystal in the slurry was measured after the pulverization, the average particle size was about 0.2 μm.

The slurry after the fine pulverization treatment was transferred to a beaker made of fluororesin having a capacity of 100 ml, and this container was put in a stainless steel pressurized container, sealed, heated to 150 ° C. and held for 8 hours to produce a precursor oxide. . After cooling, remove the slurry and remove
It was dropped on a hot plate heated to 0 ° C. and dried to obtain a precursor oxide powder. The obtained precursor oxide had the main X-ray diffraction peaks shown in Table A above, and was in the form of fine flaky crystals having an average particle diameter of 1 μm or less.

(3) Production of calcined oxide The precursor oxide obtained in the above (2) is placed in a calcined tube made of quartz and mixed at 480 ° C. in a mixed gas of 8% O ₂ /92% N _{2 at} 6 ° C.
It was baked for minutes and converted to a baked oxide. The obtained fired body oxide had a main X-ray diffraction peak shown in Table B above, and had a specific surface area of 16.1 m ² / g.

(4) Production of catalyst The fired oxide obtained in the above (3) was tableted (7 mm
φ × 2 mm), and then crushed to take out a powder having a particle size of 14 to 24 mesh to obtain a catalyst (catalyst-1).

Comparative Example-1 A precursor oxide and a fired body oxide were obtained in the same manner as in Example 1, except that no seed crystal was used. The particle size of the precursor oxide was 2-3 μm, and the specific surface area of the calcined oxide was 5.3 m ² / g. Example from fired oxide-
In the same manner as in Example 1, a catalyst (Comparative Catalyst-1) was produced.

Comparative Example 2 A precursor oxide and a fired body oxide were obtained in the same manner as in Example 1, except that the slurry after the addition of the seed crystal was not subjected to the fine pulverization treatment by a wet pulverizer. Was.
The particle size of the precursor oxide was about 3 μm, and the particle size of the calcined oxide was about the same. Specific surface area of calcined oxide is 5.6m
² / g. A catalyst (comparative catalyst-2) was produced from the calcined oxide in the same manner as in Example-1.

Reaction Example-1 A fixed-bed reactor made of a glass tube having an outer diameter of 6 mmφ was charged with 1 ml of the catalyst. The reaction tube was maintained at a reaction temperature, and a reaction gas was supplied thereto to carry out a reaction. The product was absorbed in water, the amount of maleic acid as the product was quantified by absorbance, and the waste gas was analyzed by gas chromatography. As a reaction gas, a 4% butane / air mixed gas was used, and the reaction was performed at GHSV = 1,000 hr ^-1 . The results of the reaction using catalyst-1 and comparative catalysts-1 and 2 are shown in the following table. The optimum reaction temperature is a reaction temperature at which the yield of maleic anhydride is maximized.

[Effects of the Invention] The vanadium-phosphorus crystalline oxide produced by the method of the present invention or a catalyst containing the same can be used as a catalyst precursor or an active component, or as a catalyst, in the form of a hydrocarbon having 4 or more carbon atoms. It can be used for the production of maleic anhydride by phase oxidation and has excellent activity and selectivity.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Motoyuki Miyasaka 3-10, Utsudori, Kurashiki-shi, Okayama Prefecture Mizushima Plant, Mitsubishi Chemical Corporation (56) References JP-A-58-194726 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) C01B 25/37

Claims (5)

(57) [Claims] 1. The following Table A, prepared by reaction in an aqueous medium as seed crystals and obtained by milling: Are fine crystals of a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in FIG.
A tetravalent vanadium compound and a pentavalent phosphorus compound are reacted under heating in an aqueous medium in the presence of: a vanadium-phosphorus crystal having a main X-ray diffraction peak shown in Table A above. A method for producing a vanadium-phosphorus crystalline oxide, which comprises producing an oxide. 2. The method for producing a vanadium-phosphorus crystalline oxide according to claim 1, wherein said tetravalent vanadium compound is formed in situ by reacting a pentavalent vanadium compound with a reducing agent. A method characterized by having been performed. 3. The following Table A, prepared by reaction in an aqueous medium as seed crystals and obtained by milling: Are fine crystals of a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in FIG.
A tetravalent vanadium compound and a pentavalent phosphorus compound are reacted under heating in an aqueous medium in the presence of: a vanadium-phosphorus crystal having a main X-ray diffraction peak shown in Table A above. A method for producing a catalyst containing a vanadium-phosphorus crystalline oxide, which comprises producing an oxide and shaping the crystalline oxide into a catalyst shape. 4. The following Table A, prepared by reaction in an aqueous medium as seed crystals and obtained by milling: Are fine crystals of a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in FIG.
A tetravalent vanadium compound and a pentavalent phosphorus compound are reacted under heating in an aqueous medium in the presence of: a vanadium-phosphorus crystal having a main X-ray diffraction peak shown in Table A above. Producing an oxide, and calcining the crystalline oxide, Table B below: A method for producing a vanadium-phosphorus crystalline oxide, comprising producing a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in (1). 5. The following Table A, prepared by reaction in an aqueous medium as seed crystals and obtained by milling: Are fine crystals of a vanadium-phosphorus crystalline oxide having a main X-ray diffraction peak shown in FIG.
A tetravalent vanadium compound and a pentavalent phosphorus compound are reacted under heating in an aqueous medium in the presence of: a vanadium-phosphorus crystal having a main X-ray diffraction peak shown in Table A above. Producing the oxide, calcining the crystalline oxide and Table B below: Producing a vanadium-phosphorus-based crystalline oxide having a main X-ray diffraction peak shown in the following, and forming the crystalline oxide into a catalyst shape.
A method for producing a phosphorus-based crystalline oxide-containing catalyst.