RU2793851C1 - Oxide catalyst and method for producing unsaturated nitriles - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: inventions relate to catalysts and their use for the production of unsaturated nitrile. Described is an oxide catalyst for use in a gas-phase catalytic propane or isobutane ammoxidation reaction, wherein the oxide catalyst contains a complex oxide, in which the complex oxide contains catalytically active particles that are isolated from the complex oxide using a hydrogen peroxide solution, and these catalytically active particles have an average composition, defined by STEM-EDX measurements, represented by the following formula: Mo₁V_aSb_bNb_cW_dO_n, where a, b, c and d satisfy the relations represented by the formulas 0.050≤a≤0.200, 0.050≤b≤0.200, 0.100≤c≤0.300, 0≤d≤0.100, and a≤c; and n is a number determined by the valences of other elements. Described is a process for producing unsaturated nitrile by the reaction of gas-phase catalytic ammoxidation of propane or isobutane in the presence of the oxide catalyst described above.

EFFECT: obtaining unsaturated nitrile.

7 cl, 1 tbl, 12 ex

Description

Technical field

[0001]

The present invention relates to an oxide catalyst and a process for producing an unsaturated nitrile.

State of the art

[0002]

In the past, as a catalyst used to produce an unsaturated carboxylic acid or an unsaturated nitrile by a gas-phase catalytic oxidation reaction or a gas-phase catalytic ammoxidation reaction of propylene or isobutylene, a complex oxide containing a plurality of metals such as molybdenum and vanadium has been used. A complex oxide containing many metals such as molybdenum and vanadium has also been used in the production of the corresponding unsaturated nitrile using propane or isobutane instead of olefin as the starting compound.

[0003]

Non-Patent Document 1 describes an oxide catalyst containing molybdenum (Mo), vanadium (V), antimony (Sb), and niobium (Nb). Non-Patent Document 1 explains the redox action mechanism of an oxide catalyst, and specifically describes a Mo/V/Sb/Nb=1/0.33/0.15/0.11 catalyst as an oxide catalyst.

[0004]

Patent Document 1 describes a catalyst composition for carrying out propane ammoxidation in a gas phase, wherein the catalyst composition contains one or more crystalline phases, wherein at least one of the crystalline phases is a first phase containing an M1 crystal structure and containing a mixed metal oxide containing molybdenum (Mo), vanadium (V), antimony (Sb) and niobium (Nb); and the first phase has a unit lattice volume in the range of 2250 A ³ to 2350 A ³ , a first crystal size, and a second size that intersects the first crystal size, provided that the ratio of the first size to the second size is in the range of 2.5 to 0 .7. The catalyst composition is described to exhibit properties that make ammoxidation of a saturated hydrocarbon to the corresponding unsaturated nitrile easy in high yield.

List of cited literature

Patent Documents

[0005]

[Patent Document 1]: Japanese Patent No. 5547057

Non-Patent Documents

[0006]

[Non-Patent Document 1]: Safonova, O., et. al., J. Phys. Chem. B 2006, 110, 23962 to 23967

[Non-Patent Document 2]: Millet, J.M., et. al., Appl. Catal., A 2002, 232, 77

[Non-Patent Document 3]: Millet, J.M., et. al., Appl. Catal., A 2003, 244, 359

[Non-Patent Document 4]: Baca, M., et. al., Top. catal. 2003, 23, 39

[Non-Patent Document 5]: Shannon et al., Acta A 32 (1976) 751

The essence of the present invention

Technical problem

[0007]

In the gas phase catalytic ammoxidation of propane or isobutane, improving product yield and increasing productivity are challenges. Non-Patent Document 1 only describes, as mentioned above, the redox action mechanism of an oxide catalyst containing molybdenum (Mo), vanadium (V), antimony (Sb) and niobium (Nb) and having a rhombic crystal structure, but studies on improving the yield of unsaturated nitrile was not carried out.

[0008]

Patent Document 1 describes that the yield of unsaturated nitrile can be increased by controlling the aspect ratio of a given oxide catalyst, but studies on controlling the ratio of elements that form the crystal structure of an oxide catalyst have not been conducted.

[0009]

The present invention has been made in view of these problems, and an object of the present invention is to provide an oxide catalyst capable of increasing the yield of unsaturated nitrile which is a gas phase catalytic ammoxidation reaction product of propane or isobutane, and a process for producing unsaturated nitrile using this oxide catalyst.

Solution

[0010]

The present inventors have made careful studies to solve the problems, and have found that an oxide catalyst containing a composite oxide having a predetermined element ratio, in particular a composite oxide in which the proportion of Nb content is increased and the proportion of V content is relatively reduced, can improve the yield of unsaturated nitrile, whereby the present invention was completed.

[0011]

That is, the present invention includes the following aspects.

[1]

An oxide catalyst for use in a gas phase catalytic propane or isobutane ammoxidation reaction, wherein the oxide catalyst comprises a complex oxide in which

the complex oxide contains catalytically active particles that are separated from the complex oxide using a hydrogen peroxide solution, and

these catalytically active particles have an average composition determined by measurements using STEM-EDX, represented by the following formula (1):

Mo ₁ V _a Sb _b Nb _c W _d X _e O _n (1)

where X is at least one element selected from the group consisting of Te, Ce, Ti and Ta; a, b, c, and d satisfy the ratios represented by the formulas 0.050≤a≤0.200, 0.050≤b≤0.200, 0.100≤c≤0.300, 0≤d≤0.100, 0≤e≤0.100, and a≤c; and n is a number determined by the valences of the other elements.

[2]

The oxide catalyst according to [1], where the formula (1) satisfies the relationship represented by the formula 1.1×a ≤ c.

[3]

The oxide catalyst according to [1], where the formula (1) satisfies the relationship represented by the formula 1.3×a ≤ c.

[4]

The oxide catalyst according to any one of [1] to [3], wherein formula (1) satisfies the relationship represented by the formula 8.00 ≤ 100×b/(1+a) ≤ 10.00.

[5]

The oxide catalyst according to any one of [1]-[4], where

the oxide catalyst contains silica as a support supported by a composite oxide, and

the mass fraction of silicon dioxide is from 30 to 70% by weight in terms of SiO ₂ relative to the total amount of the oxide catalyst.

[6]

An oxide catalyst for use in a gas phase catalytic propane or isobutane ammoxidation reaction, wherein the oxide catalyst comprises a complex oxide in which

the complex oxide contains catalytically active particles containing molybdenum, vanadium, antimony and niobium, and

the mass fraction of catalytically active particles is 45% by mass or more of the total amount of complex oxide.

[7]

A method for producing an unsaturated nitrile, the method comprising producing an unsaturated nitrile by means of a gas-phase catalytic ammoxidation reaction of propane or isobutane in the presence of an oxide catalyst according to any one of [1]-[6].

Advantageous Effects of the Present Invention

[0012]

According to the present invention, there is provided an oxide catalyst capable of increasing the yield of unsaturated nitrile which is a gas-phase catalytic reaction product of propane or isobutane ammoxidation, and a process for producing unsaturated nitrile using this oxide catalyst.

Description of Embodiments

[0013]

Next, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. It should be noted that the present invention is not limited to the following present embodiment, and can be implemented by modifying the present embodiment in various ways within the scope of the present invention. In the case where numerical values or physical property values are expressed before and after "-" such that "-" is inserted between them in the present specification, the values apply provided that the values before and after "-" are included. For example, the designation of the range of numerical values from "1 to 100" includes both the upper limit value "100" and the lower limit value "1". The same applies to the designations of other ranges of numerical values.

[0014]

[Oxide Catalyst]

The oxide catalyst of the present embodiment is used for the gas-phase catalytic ammoxidation reaction of propane and isobutane, and is an oxide catalyst containing a composite oxide. Further, the reaction for producing an unsaturated nitrile from propane or isobutane, an oxygen source such as oxygen, and a nitrogen source such as ammonia is simply referred to as "gas-phase catalytic ammoxidation reaction".

[0015]

The oxide catalyst of the present embodiment contains a predetermined composite oxide and, if necessary, may contain a carrier on which the composite oxide is supported. Next, each component will be described in detail.

[0016]

(Complex oxide)

The composite oxide contains catalytically active particles, which are separated from the complex oxide by using a hydrogen peroxide solution, and the catalytically active particles have an average composition determined by STEM-EDX measurements represented by the following formula (1).

Formula:

Mo ₁ V _a Sb _b Nb _c W _d X _e O _n (1)

where X is at least one selected from the group consisting of Te, Ce, Ti and Ta; a, b, c, and d satisfy the ratios represented by the formulas 0.050≤a≤0.200, 0.050≤b≤0.200, 0.100≤c≤0.300, 0≤d≤0.100, 0≤e≤0.100, and a≤c; and n is a number determined by the valences of the other elements.

[0017]

Catalytically active particles in the present embodiment can be separated from an oxide catalyst, more specifically from a complex oxide, using a hydrogen peroxide solution, and thus the separated substances are called catalytically active particles. In this case, in the case where the oxide catalyst contains a carrier, the catalyst particles can be separated in a state in which the carrier is mixed, but each of the carrier and the catalyst particles are different components. The average composition of the selected catalytically active particles is measured using STEM-EDX. STEM-EDX in the present invention is a scanning transmission electron microscope equipped with an X-ray spectrometer with energy dispersive characteristics.

[0018]

The catalytically active particles in the present invention are a crystalline phase containing at least molybdenum (Mo), vanadium (V), antimony (Sb) and niobium (Nb), and a complex metal oxide having catalytic activity for propane ammoxidation and/ or isobutane. It should be noted that, if necessary, at least one additional metal (X) selected from the group consisting of tungsten (W), tellurium (Te), cerium (Ce), titanium (Ti) and tantalum (Ta) can additionally contained in catalytically active particles.

[0019]

The previously mentioned catalytically active particles are described, for example, as the first phase having an M1 crystal structure in Patent Literature 1 (Japanese Patent No. 5547057), and a similar explanation is given in Non-Patent Literature 1 (Safonova, O., et. al., J Phys. Chem. B 2006, 110, 23962 to 23967), non-patent literature 2 (Millet, J.M., et. al., Appl. Catal., A 2002, 232, 77), non-patent literature 3 (Millet, J.M., et al., Appl. Catal., A 2003, 244, 359), non-patent literature 4 (Baca, M., et. al., Top. Catal. 2003, 23, 39) and the like.

[0020]

As a result of careful studies carried out by the present inventors, it has become clear that by using an oxide catalyst in which the relative content of Nb in the catalytically active particles is increased and the relative content of V is relatively reduced, an increase in the yield of unsaturated nitrile in the gas-phase catalytic ammoxidation reaction is achieved. That is, when the formula (1) of the catalytically active particles has the above-described average composition, thereby increasing the yield of unsaturated nitrile produced by the gas-phase catalytic ammoxidation reaction.

[0021]

As will be mentioned below in the oxide catalyst production method, it has been found that by using a specific Nb-containing liquid as a raw material and/or further performing a specific catalyst production step, the relative Nb content of the catalytically active particles can be increased and the relative amount of V can be relatively reduced. According to non-patent literature 5 (Shannon et al., Acta A 32 (1976) 751), the ionic radii of Nb and V (in the case of five valences and six-coordination in the oxide) are 0.64 and 0.54 Å, respectively, and there are a large difference up to 18.5%, and so it is generally considered that a substitutional solid solution is unlikely to form by the Hume-Rothery rules. The Hume-Rothery rules given in the present invention are rules showing that in substitutional solid solutions, a solid solution is formed in almost the entire ratio of components if the difference in the ionic radius of the respective components is up to about 10%, but, on the other hand, in the case when the ionic radii differ by 15% or more, hardly any solid solution is formed.

It is assumed that specific substitution phenomena, such as those in which the site occupied by Mo having an ionic radius of 0.59 Å, the ionic radius being such that the difference in ionic radius is relatively small for both Nb and V (Nb: 8.5 %) is replaced by Nb, and that the destabilized adjacent site that V occupies is replaced by Mo, are the result of the fact that the present catalytically active particles have an extremely complex crystal structure, although the detailed structure of the substitution is not well understood.

[0022]

The factor that can improve the yield of unsaturated nitrile by increasing the relative content of Nb in the catalytic active particles and the relative decrease in the relative content of V is considered as follows. First of all, Nb has a high melting point, and when the proportion of Nb having a high melting point is increased, the stability of the catalytically active particles in the reaction atmosphere is increased. It is believed that the yield of unsaturated nitrile can be improved in this way.

[0023]

In the present embodiment, it is preferable to relatively increase the relative content of Sb relative to the relative content of Mo-O-V in the catalytically active particles compared to conventional catalysts. Through this, the relative content of Mo-O-V, which is considered to cause non-selective decomposition activity, although Mo-OV is the active site of the propane or isobutane dehydrogenation reaction, can be relatively reduced, and the relative content of Sb, which is the active site of the gas-phase catalytic ammoxidation reaction , can be relatively enlarged. It is believed that therefore it is possible to increase the yield of unsaturated nitrile.

[0024]

Unsaturated nitrile means acrylonitrile as a preferred aspect of the present embodiment.

[0025]

The composite oxide in the present embodiment is a metal oxide that constitutes the oxide catalyst of the present embodiment, at least molybdenum (Mo), vanadium (V), antimony (Sb), and niobium (Nb) are included as metal oxide metals, and optionally, additional metal may be included.

[0026]

Catalytically active particles in the present embodiment means metal components which are obtained by treatment with hydrogen peroxide as shown in the above-described method, in particular, in the measurement method (physical property 1) to be mentioned below. Typically, a complex oxide contains two crystalline phases and an amorphous component in many cases. These two crystalline phases are composed of a phase having a high oxidation resistance and a phase having a weak oxidation resistance, and it is known that in the present catalyst system, the phase having a high oxidation resistance corresponds to catalytically active particles as described in non-patent literature 1 When pretreatment is carried out using a hydrogen peroxide complex oxide solution, the phase having poor oxidation resistance is dissolved, but the catalytically active species, which is the phase having high oxidation resistance, is not dissolved, so that the state before oxidation can be maintained. oxidation treatments. Therefore, by carrying out the oxidation treatment, the phase having poor oxidation resistance is dissolved, so that the catalytically active particles can be separated from the composite oxide, and the composition of the catalytically active particles can be measured with high accuracy.

[0027]

As shown in the measurement method (Physical property 4) to be mentioned below, the mass fraction of the catalytically active particles (G1), assuming that the mass of the complex oxide is 100%, can be calculated using the following equation, from the mass fraction of the carrier, which has almost there is no increase or decrease in weight before and after treatment. The mass fraction of the catalytically active particles is preferably 43% by mass or more, more preferably 45% by mass or more, and even more preferably 48% by mass or more by mass fraction.

I ₁ : mass fraction of support in the oxide catalyst

I ₂ : mass fraction of support in the oxide catalyst residue obtained by oxidative treatment with hydrogen peroxide solution

[0028]

The catalytically active particles may additionally or optionally contain an additional metallic element (X). Examples of the additional metal element (X) include, but are not specifically limited to, Te, Ce, Ti, and Ta. In the case where the catalytically active particles contain an additional metal element (X), the additional metal element (X) may be a single metal element or may be a plurality of metal elements. It should be noted that in the case where the catalytically active particles do not contain an additional metal element (X), the formula (1) is represented by the following formula (1a).

Mo ₁ V _a Sb _b Nb _c W _d O _n (1a)

where a, b, c, d, and n have the same meanings as the variables in formula (1).

[0029]

With regard to the measurement of the average composition of the catalytically active particles, the catalytic active particles are separated from the oxide catalyst using a hydrogen peroxide solution, and the average composition of the separated catalytically active particles can be measured by STEM-EDX as mentioned above, and in particular, the measurement of the average composition of the catalytic particles can be performed in the manner (physical property 1) described in the examples.

[0030]

In the formula (1), a satisfies 0.050≤a≤0.200, preferably satisfies 0.050≤a≤0.150, more preferably satisfies 0.080≤a≤0.150, even more preferably satisfies 0.100≤a≤0.150, and even more preferably satisfies 0.100≤a≤ 0.130.

[0031]

In the formula (1), b satisfies 0.050≤b≤0.200, preferably satisfies 0.050≤b≤0.150, more preferably satisfies 0.070≤b≤0.150, and even more preferably satisfies 0.080≤b≤0.150.

[0032]

In formula (1), c satisfies 0.100≤c≤0.300, preferably satisfies 0.100≤c≤0.250, more preferably satisfies 0.130≤c≤0.250, and even more preferably satisfies 0.140≤c≤0.200.

[0033]

In the formula (1), d satisfies 0≤d≤0.100, preferably satisfies 0<d≤0.100, more preferably satisfies 0.010≤d≤0.100, and even more preferably satisfies 0.020≤d≤0.100.

[0034]

In formula (1), e satisfies 0≤e≤0.100, preferably satisfies 0≤e≤0.050, more preferably satisfies 0≤e≤0.010, and even more preferably satisfies e=0. It should be noted that e is the ratio of at least one X metal selected from the group consisting of Te, Ce, Ti, and Ta per molybdenum atom, and in the case where two or more X metals are contained, e is the total relative content of metals X.

[0035]

There is a tendency that when each of a, b, c, d, and e satisfies the above-described range, the yield of unsaturated nitrile is thereby improved. The average composition of the catalytically active particles can be controlled by adjusting the amount of raw materials. The ratio represented by the formula a≤c can be controlled in particular by using a specific Nb-containing liquid as a raw material.

[0036]

Formula (1) preferably satisfies 0.050≤a≤0.150 and 0.100≤c≤0.250, and more preferably satisfies 0.050≤a≤0.150, 0.080≤b≤0.150, 0.100≤c≤0.250, and 0≤d≤0.100. In addition, the formula (1) preferably satisfies 0.050≤a≤0.150, 0.100≤c≤0.250, and e=0, and more preferably satisfies 0.050≤a≤0.150, 0.08≤b≤0.150, 0.100≤c≤0.250, 0≤d≤0.100 and e=0. There is a tendency that when the formula (1) satisfies the composition described above, the yield of the unsaturated nitrile is thus improved.

[0037]

Formula (1) satisfies the relationship represented by the formula a≤c, and from the viewpoint of further improving the yield of unsaturated nitrile, preferably satisfies the relationship represented by the formula 1.1×a≤c, more preferably satisfies the relationship represented by the formula 1.3×a≤ c, and even more preferably satisfies the ratio represented by the formula 1.5×a≤c. In addition, the formula (1) preferably satisfies the relationship represented by the formula c≤a×3.0, more preferably satisfies the relationship represented by the formula c≤a×2.5, and even more preferably satisfies the relationship represented by the formula c≤a×2 ,0.

[0038]

The Sb contained in the catalytically active particles is considered to be the active part of the gas-phase catalytic ammoxidation reaction as above, and therefore it is preferably contained in a certain amount. Specifically, the formula (1) preferably satisfies the ratio represented by the formula 0.100≤b/(a+b+c)≤0.400, more preferably satisfies the ratio represented by the formula 0.150≤b/(a+b+c)≤0.300, and even more preferably satisfies the ratio represented by the formula 0.200≤b/(a+b+c)≤0.300. There is a tendency that when the formula (1) satisfies the relationship described above, the yield of the unsaturated nitrile is thus improved.

[0039]

The catalytically active particles preferably contain a certain amount of Sb, the formula (1) preferably satisfies the ratio represented by the formula 7.00≤100×b/(1+a)≤11.00, more preferably satisfies the ratio represented by the formula 8.00≤100× b/(1+a)≤10.00, and even more preferably satisfies the ratio represented by the formula 8.50≤100×b/(1+a)≤10.00. The yield of unsaturated nitrile tends to increase more when the formula (1) satisfies the relationship described above.

[0040]

(Carrier)

The oxide catalyst of the present embodiment may contain a carrier in addition to the composite oxide. That is, the oxide catalyst of the present embodiment may be shaped such that the oxide catalyst is carried by a carrier. As the support, an oxide such as silica, alumina, titanium dioxide or zirconia is used, but silica is suitable from the point of view that the decrease in object selectivity is small, and the wear resistance and strength of the formed catalyst particles become satisfactory.

[0041]

The amount of silica carrier is usually 20% by mass to 80% by mass, preferably 30% by mass to 70% by mass, and more preferably 40% by mass to 60% by mass, based on the total mass of the carrier. based on silicon dioxide and complex oxide, namely the total amount of oxide catalyst.

[0042]

One of the preferred aspects of the oxide catalyst of the present embodiment is an oxide catalyst containing silica as a composite oxide support, and the mass fraction of silica is from 30% by mass to 70% by mass, based on SiO ₂ , based on the total amount of oxide catalyst.

[0043]

Examples of a starting material for a silica-based carrier include, but are not specifically limited to, silica sol (also referred to as colloidal silica) and powdered silica. As a starting material for a silica-based support, a silica sol is preferable from the point of view of ease of handling. The average particle diameter of the primary silica particles contained in the silica sol is not specifically limited. As a silica-based carrier for use, various types of silica sol can be added, each having a different primary particle diameter.

[0044]

The shape and particle size of the oxide catalyst of the present embodiment are not particularly limited, but in the case where the oxide catalyst of the present embodiment is used as a fluidized bed catalyst, the oxide catalyst is preferably spherical and preferably has a particle diameter of 10-150 µm in terms of fluidity.

[0045]

[Method for producing oxide catalyst]

The oxide catalyst of the present embodiment can be produced by a production method comprising: a step of mixing raw materials for appropriate mixing of raw materials, thereby obtaining a precursor slurry; a step of drying the precursor slurry to obtain a dried particle; and a calcination step in which the dried particle is calcined to obtain an oxide catalyst. If necessary, the method for producing an oxide catalyst according to the present embodiment may include the step of removing protrusions of the obtained oxide catalyst.

[0046]

It should be noted that hereinafter, the aqueous mixed liquid A corresponds to the mixed liquid (B) not containing niobium in general applications (Japanese Patent Application No. 2019-106015 and Japanese Patent Application No. 2019-106018). The niobium raw material liquid B corresponds to the composition for producing a catalyst containing niobium, the composition (A) for producing a catalyst or a mixed liquid in general applications (Japanese Patent Application No. 2019-106015 and Japanese Patent Application No. 2019-106018). Precursor slurry C corresponds to the original slurry or liquid with a mixture of raw materials in general applications (Japanese Patent Application No. 2019-106015 and Japanese Patent Application No. 2019-106018).

[0047]

(Stage of mixing of initial substances)

The step of mixing the raw materials is not particularly limited, and for example, includes: a step of obtaining A of mixing a molybdenum raw material, a vanadium raw material, an antimony containing raw material, and water, thereby obtaining an aqueous mixed liquid A; a production step B of mixing the niobium raw material and the organic acid, thereby obtaining a liquid B of the niobium raw material; and a step of mixing C of the aqueous mixed liquid A and liquid B with the niobium raw material, thereby obtaining a precursor slurry C.

[0048]

The oxide catalyst of the present embodiment can be produced by adjusting the preferred production conditions to be mentioned below in the production step B, or by adjusting the preferred mixing conditions to be mentioned below in the mixing step C.

[0049]

Then, the niobium raw material liquid B containing the organic acid and the niobium raw material, and the aqueous mixed liquid A which was obtained in the preparation step B in advance, are mixed so as to match the intended composition, thereby obtaining the raw material mixture liquid as a suspension precursors (mixing step C). For example, in the case where the catalyst contains W or Ce, the raw material mixture liquid is obtained by appropriately mixing the W-containing compound. starting material and aqueous mixed liquid A.

[0050]

In the case where the oxide catalyst contains a silica-based support, namely, in the case where the oxide catalyst is carried on a silica-based support, the raw material mixture liquid can be obtained in such a way that it contains a silica sol, and in this case, the sol silicon dioxide can be added in a suitable manner.

[0051]

(Acquisition Stage A)

The production step A is a step of mixing a molybdenum raw material, a vanadium raw material, an antimony-containing raw material, and water, thereby obtaining an aqueous mixed liquid A. More specifically, a molybdenum raw material, a vanadium raw material, and an antimony-containing raw material are added to water and heated at a predetermined temperature or higher with stirring, and thereby an aqueous mixed liquid A can be obtained. In this case, when the catalyst contains W or Ce, a tungsten raw material or a cerium raw material can be further added.

[0052]

The raw material components to be used for the aqueous mixed liquid A are not particularly limited, and for example, the following components can be used.

[0053]

Examples of the molybdenum starting material include, but are not specifically limited to, molybdenum oxide, ammonium dimolybdate, ammonium heptamolybdate, phosphomolybdic acid, and silicomolybdic acid, and ammonium heptamolybdate, among others, can be conveniently used.

[0054]

Examples of the vanadium starting material include, but are not specifically limited to, vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate, and ammonium metavanadate can be conveniently used, among others.

[0055]

As the starting material containing antimony, antimony oxide can be conveniently used. The tungsten raw material is not particularly limited, and for example, ammonium metatungstate is conveniently used. The cerium starting material is not particularly limited, and for example, cerium nitrate hexahydrate can be conveniently used.

[0056]

The lower temperature limit during stirring is usually 80°C or higher, and preferably 90°C or higher. There is a tendency that when the stirring temperature is set to 80° C. or higher, the oxidation/reduction reaction between antimony oxide, which is generally poorly soluble in water, and another precursor oxide (eg, vanadium precursor) proceeds more easily. On the other hand, it is preferable that the upper limit of the stirring temperature is generally 100° C. or lower to avoid bubbling.

[0057]

(Acquisition stage B)

The production step B is a step of mixing a niobium raw material and an organic acid, thereby obtaining liquid B with a niobium raw material. At the stage of obtaining B, you can additionally add water. The niobium starting material is, in general, poorly soluble in water and, therefore, dissolves in water due to the presence of an organic acid. In this case, it is preferable that the content of Nb in the niobium raw material liquid B is high and the dispersibility of Nb is satisfactory when producing the oxide catalyst of the present embodiment.

[0058]

From this point of view, it is preferable to mix the niobium starting material and the organic acid with stirring and heating in the production step B, adjusting the molar ratio of the organic acid to Nb and the turbidity. More specifically, by setting the molar ratio of organic acid to Nb (organic acid/Nb) to 2.40 or less, the concentration of Nb can be sufficiently increased, and the amount of organic acid used as a reducing agent can be sufficiently reduced. In addition, by setting the turbidity of the niobium raw material liquid B to 500 NMU or less, the fineness of Nb can be kept at a satisfactory level even if there is a sufficiently high concentration of Nb. Due to the niobium raw material B liquid which is obtained by this method, the ratio of Nb in the complex oxide in the oxide catalyst of the present embodiment is increased, and the ratio of V, which is considered to cause alkane decomposition, is relatively reduced, and thus can be increased. yield of unsaturated nitrile.

[0059]

The niobium raw material is not particularly limited as long as it is an Nb-containing compound, but any of these compounds is sparingly soluble and therefore dissolves in the presence of an organic acid. Specific examples of the niobium starting material include, but are not limited to, niobium hydrooxalate, niobium ammonium oxalate, NbCl ₃ , NbCl ₅ , Nb ₂ (C ₂ O ₄ ) ₅ , Nb ₂ O ₅ , niobic acid, Nb(OC ₂ H ₅ ) ₅ , niobium halide, niobium halogenated ammonium salt, and combinations thereof. Among them, in the case where an additional metal is added to the niobium raw material liquid B, niobic acid and niobium hydroxalate are preferable from the viewpoint of reducing the effect on the additional metal. It should be noted that niobic acid contains niobium hydroxide and niobium oxide. The niobium raw material changes its quality in some cases due to long-term storage or dehydration process, and therefore, it is preferable to use the niobium raw material immediately after production to obtain liquid B with the niobium raw material, but it is possible to use a compound that has suffered to some extent quality change.

[0060]

The niobium starting material may be solid or in suspension when making Liquid B with the niobium starting material. In the case of using niobic acid, the particle diameter is preferably small in terms of ease of dissolution. The niobic acid can be washed with ammonia water and/or water before use.

[0061]

Examples of organic acids include, but are not specifically limited to, dicarboxylic acids. Specific examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid and glutaric acid, and from the viewpoint of suppressing excessive metal oxide reduction in the calcination step during catalyst preparation, oxalic acid is preferred, more specifically, oxalic anhydride and oxalic acid dihydrate are preferred. Only one dicarboxylic acid may be added, or several dicarboxylic acids may be added.

[0062]

As stated above, the molar ratio of organic acid to Nb (organic acid/Nb) is preferably low. When the molar ratio (organic acid/Nb) is large, the Nb concentration is low, and there is a tendency that the fineness and stability of Nb in liquid B with the niobium raw material is satisfactory, but when the molar ratio (organic acid/Nb) is excessively large, there is a risk that the resulting catalyst is over-reduced by the organic acid, which functions as a reducing agent. In addition, the amount of Nb is insufficient, whereby the catalytically active particles are not sufficiently formed, and the decomposition suppressing effect of the product is not sufficiently obtained. On the other hand, when the molar ratio (organic acid/Nb) is small, the concentration of Nb is high, a niobium raw material liquid B is obtained containing sufficient Nb, but the dispersion of Nb in the niobium raw material liquid B is reduced, and as a result , it becomes difficult to obtain a uniform introduction of Nb into the catalytically active particles. From this point of view, the molar ratio (organic acid/Nb) is set to 2.40 or less. That is, by setting the molar ratio to 2.40 or less, a sufficient amount of Nb can be introduced without making the input amount of the organic acid that functions as a reducing agent excessive, and hence the catalytic active particles are sufficiently formed and the suppression effect decomposition of the product can be achieved sufficiently, and as a result, the characteristics of the obtained catalyst become satisfactory. From a point of view similar to that described above, the molar ratio (organic acid/Nb) is preferably 2.20 or less, more preferably 1.90 or more and 2.18 or less, and even more preferably 1.95 or more and 2.15 or less.

[0063]

As previously stated, if the dispersion of Nb in the niobium raw material liquid B is not satisfactory, Nb precipitation is observed, and there is a tendency that the change in Nb concentration over time is noticeable. Therefore, the molar ratio in the present embodiment is increased based on the concentration after the niobium raw material liquid B is left standing at normal temperature for one day immediately after production. It should be noted that "normal temperature" in the present invention means a temperature in the region of 15-25°C. Specifically, the molar ratio can be measured by the method described in the examples below. The molar ratio (organic acid/Nb) can be controlled within the range described above by the ratio of the starting materials to be used.

[0064]

As for the turbidity of the niobium raw material liquid B, a larger value suggests that the fineness of Nb is poor, and a smaller value suggests that the fineness of Nb is more satisfactory. From this point of view, the turbidity of liquid B with niobium raw material is 500 NU or less. In the present embodiment, the turbidity is sufficiently low even if the molar ratio (organic acid/Nb) is reduced to a minimum of 2.40 or less as above, and hence catalytically active particles which are active sites are formed in sufficiently, and the effect of suppressing the decomposition of the product can be sufficiently obtained. In addition to this, uniform introduction of Nb into the catalytically active particles becomes possible due to the satisfactory dispersion of Nb, and as a result, the performance of the obtained oxide catalyst becomes particularly satisfactory. From a point of view similar to that described above, the turbidity is preferably 0.5 NMU or more and 400 NMU or less, and more preferably 1.0 NMU or more and 200 NMU or less.

[0065]

As previously stated, if the dispersion of Nb in liquid B with niobium raw material is not satisfactory, Nb precipitation is observed, and there is a tendency that a change in the amount of haze becomes noticeable with time. Therefore, the turbidity in the present embodiment is also increased based on the turbidity after the niobium raw material liquid B is left standing at normal temperature for one day immediately before production. Specifically, haze can be measured by the method described in the examples to be given below. The turbidity can be controlled within the range described above by adapting the preferred method of preparation, which will be given below.

[0066]

The mixing temperature in the production step B is preferably greater than 60°C and less than 80°C, more preferably 63°C or higher and 78°C or lower, and even more preferably 65°C or higher and 75°C or lower. By setting the mixing temperature in such a way that it is more than 60° C., there is a tendency that sufficient suspension of Nb is facilitated. By setting the mixing temperature such that it is below 80°C, the complex of organic acid and Nb that is formed in liquid B with the niobium raw material is stabilized, so that there is a tendency that sufficient dispersibility is provided even at a high concentration of Nb. In addition, stirring is preferably carried out simultaneously with heating in the production step B. Through this, the molar ratio (organic acid/Nb) is controlled in the above-described range, and the turbidity can be kept at a low level.

[0067]

With regard to the mixing time in the production step B, it is desirable to provide a sufficiently long reaction time in terms of allowing the reaction between the organic acid and the niobium starting material to proceed sufficiently, but if the reaction time is too long, there is concern that the stability of the organic acid complex and Nb decreases because the mixed liquid is in a heated state for an excessively long time. From the viewpoint of ensuring sufficient dispersion, even though the Nb concentration is large, the dissolution step is preferably carried out for 1 hour or longer and 8 hours or less, preferably 3 hours or longer and 7 hours or less, and even more preferably 4 hours or longer and 6 hours or less.

[0068]

In the case where the organic acid and the niobium raw material are heated with stirring, the temperature of the mixture of the organic acid and the niobium raw material is lowered to 5°C or lower, and then the solid residue is filtered and separated by suction filtration to obtain liquid B with the niobium raw material.

[0069]

From the above, it is preferable to set the molar ratio of organic acid to Nb to 2.40 or less as organic acid/Nb, and mix the organic acid and the niobium raw material at 80° C. or lower with stirring, from the viewpoint of more efficient production of the oxide catalyst of the present embodiment. The condition that satisfies them is called the condition for obtaining b.

[0070]

(Mixing step C)

Mixing step C is a step of mixing aqueous mixed liquid A and liquid B with a niobium raw material, thereby obtaining a suspension of precursors C. In mixing step C, if necessary, hydrogen peroxide, a basic aqueous solution, an additional metal raw material such as a tungsten precursor or a cerium precursor, and/or a carrier precursor. The precursor slurry C, which is obtained by this process, is a uniformly mixed liquid in some cases, but is usually a slurry.

[0071]

The mixing condition in the mixing step C is not particularly limited, but, for example, the mixing temperature is preferably 50°C or higher and 80°C or lower, and more preferably 60°C or higher and 80°C or lower. The mixing time is preferably 1 hour or more and 5 hours or less.

[0072]

Examples of the method for adding hydrogen peroxide in the mixing step C include: a method in which an aqueous mixed liquid A and hydrogen peroxide are mixed, and then liquid B with a niobium raw material is further added; a method in which the niobium raw material liquid B and hydrogen peroxide are mixed, and then the aqueous mixed liquid A is further added; a method in which the aqueous mixed liquid A, the niobium raw material liquid B, and hydrogen peroxide are mixed at the same time; and a method in which an aqueous mixed liquid A and liquid B with a niobium raw material are mixed, and then hydrogen peroxide is further added. Among them, a method in which an aqueous mixed liquid A and hydrogen peroxide are mixed, and then a niobium raw material B is further added is preferable.

[0073]

In the case where hydrogen peroxide is added in the mixing step C, the molar ratio of hydrogen peroxide to antimony (Sb) (H ₂ O ₂ /Sb) in the aqueous mixed liquid A is preferably 0.01 or more and 5.0 or less, more preferably 2.0 or more and 4.0 or less, and even more preferably 2.5 or more and 3.5 or less. In the case where the aqueous mixed liquid A and hydrogen peroxide are mixed, it is preferable to add hydrogen peroxide while stirring the aqueous mixed liquid A under heating conditions. In this case, the temperature is usually 30°C-70°C, preferably 60°C or higher. The mixing time is preferably 30 minutes to 2 hours.

[0074]

Examples of the method for adding the basic aqueous solution in the mixing step C include: a method in which the aqueous mixed liquid A and the basic aqueous solution are mixed, and then the niobium raw material liquid B is further added; a method in which the niobium raw material liquid B and the basic aqueous solution are mixed, and then the aqueous mixed liquid A is further added; a method in which the aqueous mixed liquid A, the niobium raw material liquid B, and the basic aqueous solution are mixed at the same time; and a method in which the aqueous mixed liquid A and liquid B are mixed with the niobium raw material, and then the basic aqueous solution is further added. Among them, a method in which an aqueous mixed liquid A and a niobium raw material liquid B are mixed and then a basic aqueous solution is further added is preferable.

[0075]

Examples of the basic aqueous solution to be added in the mixing step C include, but are not specifically limited to, ammonia water, amine, and alkaline aqueous solution. Among them, the basic aqueous solution is preferably ammonia water because ammonia water mostly evaporates in the drying step and does not affect the steps after the drying step.

[0076]

In the case where the basic aqueous solution is added in the mixing step C, the molar ratio of NH ₃ to niobium (Nb) in liquid B with niobium raw material (NH ₃ /Nb) is preferably 0.01 or more and 5 or less, more preferably 2 0 or more and 4 or less, and even more preferably 2.5 or more and 3.5 or less.

[0077]

Among the above, it is preferable to mix hydrogen peroxide in such a manner that the molar ratio of hydrogen peroxide to antimony (Sb) (H ₂ O ₂ /Sb) is 2.5 or more, and to add ammonia in such a manner that the molar ratio of ammonia to niobium (Nb) (NH ₃ /Nb) was 2.0 or more in the mixing step C, from the point of view of more efficient production of the oxide catalyst of the present embodiment. In addition, it is preferable to set the pH in the mixing step C to be 5 or more, and obtain a suspension of precursors by carrying out mixing under heating conditions of 60°C or higher. Conditions that satisfy this are called mixing conditions c. It should be noted that the pH can be adjusted using the above basic aqueous solution.

[0078]

Examples of the method for adding an additional metal raw material such as a tungsten raw material or a cerium raw material in the mixing step C include: a method in which an aqueous mixed liquid A and an additional metal raw material are mixed, and then liquid B with a niobium raw material is further added; a method in which the niobium raw material liquid B and the additional metal raw material are mixed, and then the aqueous mixed liquid A is further added; a method in which the aqueous mixed liquid A, the niobium raw material liquid B, and the additional metal raw material are mixed at the same time; and a method in which an aqueous mixed liquid A and liquid B with a niobium raw material are mixed, and then additional metal raw material is further added.

[0079]

Examples of the method for adding the carrier raw material in the mixing step C include: a method in which the aqueous mixed liquid A and the carrier raw material are mixed, and then the niobium raw material liquid B is further added; a method in which the niobium precursor liquid B and the carrier precursor are mixed, and then the aqueous mixed liquid A is further added; a method in which an aqueous mixed liquid A, a liquid B with a niobium raw material, and a carrier raw material are mixed at the same time; and a method in which an aqueous mixed liquid A and liquid B with a niobium raw material are mixed, and then a carrier raw material is further added.

[0080]

In the case where an oxide catalyst is prepared, since the complex oxide is on a silica support, a silica sol can be used as the carrier starting material.

[0081]

(Other conditions)

By adjusting both of the above production conditions b and mixing conditions c, an oxide catalyst is obtained that satisfies the above ratios represented by the formulas. In particular, adjusting both of the above-described production conditions b and the mixing conditions is preferable because an oxide catalyst satisfying the ratio represented by the formula 1.1×a≤c or 1.5×a≤c or the ratio represented by formula 8 can be obtained, 00≤100×b/(1+a)≤10.00.

[0082]

It is preferable that the amount of the vanadium precursor contained in the aqueous mixed liquid A is relatively low based on the amount of the niobium precursor contained in the liquid B with the niobium precursor, in addition to adjusting the production conditions b or mixing conditions c described above. Specifically, the V/Nb atomic ratio of the vanadium atom contained in the vanadium raw material to the niobium atom contained in the niobium raw material is preferably 2.7 or less, more preferably 2.0 or less, and even more preferably 1.7 or less. The atomic ratio V/Nb can be adjusted for each concentration of the vanadium precursor in the aqueous mixed liquid A and the niobium precursor in the niobium precursor liquid B, or the weight ratio of the aqueous mixed liquid A to the niobium precursor liquid B.

[0083]

(drying stage)

The drying step is a step of drying the precursor slurry C obtained in the above step, thereby obtaining a dried powder. Drying can be carried out in a known manner, and can be carried out, for example, by spray drying or evaporation to dryness. Among them, fine spherical dried particles are preferably obtained by spray drying. Spraying in the spray-drying process can be carried out by a centrifugal system, an air-spray system, or a high-pressure spray system. As the heat source for drying, steam or air heated by an electric heater or the like can be used. The inlet temperature of the dryer in the spray dryer is preferably 150 to 300°C, and the outlet temperature of the dryer is preferably 100 to 160°C.

[0084]

(Ignition step)

The calcination step is a step of calcining the dried powder obtained in the drying step, thereby obtaining an oxide catalyst. As a calcining device, a rotary kiln can be used. The shape of the calciner is not particularly limited, but it is preferably tubular so that continuous calcination can be performed. The shape of the calcination pipe is not particularly limited, but is preferably cylindrical. As the heating system, an external heating type is preferable, and it is advisable to use an electric furnace.

[0085]

Appropriate size, material and the like of the calcination tube can be selected depending on the calcination conditions or volume to be obtained, but the inner diameter of the calcination tube is preferably 70 to 2000 mm, moreover 100 to 1200 mm, and the length of the calcination tube is preferably 200 to 10000 mm, and more preferably 800 to 8000 mm. In the case where the calciner is subjected to impact loading, the thickness of the calciner is preferably 2 mm or more, and more preferably 4 mm or more from the point of view of having a thickness sufficient for the calciner not to be broken when impacted, and is preferably 100 mm or less. , and more preferably 50 mm or less from the point of view of a sufficient degree of transmission of the shock load to the inside of the calciner. The material of the calciner is not particularly limited, except that the material has such heat resistance and strength that the material does not collapse under impact, and SUS can be conveniently applied.

[0086]

The calcination tube can be divided into two or more zones by inserting into the calcination tube a chopping grate vertically to the powder flow, a chopping grate containing an opening for passing the powder into the central part. The installation of a chop grate makes it easy to control the retention time in the calcination tube. The number of chops gratings can be one or more. The material of the chop grate is preferably metal, and the same metal as for the igniter tube can conveniently be used. The height of the chopping grate can be adjusted depending on the duration of the hold that needs to be provided. For example, in the case where the powder is fed at 250 g/h into a rotary kiln containing a SUS calcination tube with an inner diameter of 150 mm and a length of 1150 mm, the chopping grate preferably has a height of 5-50 mm, more preferably 10-40 mm, and even more preferably 13-35 mm. The thickness of the chop grate is not particularly limited, and is preferably set depending on the size of the calcination tube. For example, in the case of a rotary kiln containing a SUS calcination tube with an inner diameter of 150 mm and a length of 1150 mm, the thickness of the calcination tube is preferably 0.3 mm or more and 30 mm or less, and more preferably 0.5 mm or more, and 15 mm or less.

[0087]

The calcination tube is preferably rotated in order to prevent cracking, cracking and the like on the dried powder and to ensure uniform calcination. The rotation speed of the calcination tube is preferably 0.1-30 rpm, more preferably 0.5-20 rpm, and even more preferably 1-10 rpm.

[0088]

When the dried powder is calcined, it is preferable that the temperature rise to heat the dried powder is started from a temperature lower than 400°C, and the temperature is raised continuously or intermittently up to a temperature within the range of 550-800°C.

[0089]

The calcination atmosphere may be in an atmosphere of air or under a stream of air, but preferably carries out at least part of the calcination by allowing an inert gas, such as nitrogen, which is substantially free of oxygen, to flow. The amount of inert gas supplied is 50 N liters or more, preferably 50-5000 N liters, and even more preferably 50-3000 N liters per kg of dried powder (N liters means liters measured under standard temperature/pressure conditions, namely liters measured at 0°C and 1 atm). In this case, there is no problem when the inert gas and the dried powder are brought into contact in parallel flow or countercurrent, but countercurrent contact is preferable in view of the gas components generated from the dried powder and the air which is mixed in a small amount together with the dried powder.

[0090]

The calcination step can be carried out in one step, but it is preferred that the calcination includes a pre-calcination and a final calcination, wherein the pre-calcination is carried out in a temperature range of 250-400°C and the final calcination is carried out in a temperature range of 550-800°C. The pre-calcination and the final calcination may be carried out continuously, or after the completion of the pre-calcination, the final calcination may be carried out again. In addition, each of the pre-calcination and the final calcination can be divided into several steps.

[0091]

Precalcination is carried out at a heating temperature in the range of 250°C-400°C, and preferably 300°C-400°C, preferably in an inert gas flow. The temperature is preferably maintained at a constant temperature in the temperature range of 250°C-400°C, but it does not matter whether the temperature changes, or smoothly rises or falls in the range from 250°C to 400°C. The heating temperature holding time is preferably 30 minutes or longer, and more preferably 3-12 hours.

[0092]

With respect to the temperature raising scheme until the time when the temperature reaches the pre-calcination temperature, the temperature may be raised linearly, or the temperature may be raised in such a manner as to draw a convex upward or downward arc.

[0093]

The average temperature rise rate when the temperature is raised until the temperature reaches the pre-calcination temperature is not particularly limited, but is usually about 0.1-15°C/min, preferably 0.5-5°C/min, and more preferably 1- 2°C/min.

[0094]

The final calcination is carried out at 550-800°C, preferably 580-750°C, more preferably 600-720°C and even more preferably 620-700°C, preferably under an inert gas atmosphere. The temperature is preferably maintained at a constant temperature in the temperature range of 620-700°C, but it does not matter whether the temperature changes or gradually rises or falls in the range of 620-700°C. The final calcination time is 0.5-20 hours and preferably 1-15 hours.

[0095]

In the case where the calcination tube is separated by a chop grid or trays, the dried powder and/or composite oxide catalyst passes successively through at least two, preferably 2-20, and more preferably 4-15 zones. The temperature control can be performed using one or more controls, but the temperature is preferably controlled by setting a heater and a control for each zone separated by the chopping grids in order to obtain the desired calcination pattern. For example, in the case where seven chopping bars are set in such a manner as to evenly divide the length of the part that enters the heating furnace, the calcination pipes into eight, and the calcination pipe divided into eight zones is used, the set temperatures of the eight zones are preferably controlled by the heater and control device set for the respective zones so that the temperature of the dried powder and/or complex oxide catalyst shows the desired calcination pattern. It should be noted that it does not matter whether an oxidizing component (eg oxygen) or a reducing component (eg ammonia) is added, if necessary, to the calcination atmosphere in the inert gas stream.

[0096]

As for the temperature raising scheme until the time when the temperature reaches the final calcination temperature, the temperature may be raised linearly, or the temperature may be raised in such a manner as to draw a convex arc up or down.

[0097]

The average rate of temperature rise in the temperature rise process before the temperature reaches the final calcination temperature is not particularly limited, but is usually 0.1-15°C/min, preferably 0.5-10°C/min, and more preferably 1- 8°C/min.

[0098]

The average rate of temperature decrease after completion of the final calcination is preferably 0.05-100°C/min, and more preferably 0.1-50°C/min. Temporarily maintaining the temperature at a temperature less than the final calcination temperature is also preferred. The holding temperature is a temperature lower than the final calcination temperature by 10°C, preferably by 50°C, and more preferably by 100°C. The holding time is 0.5 hour or more, preferably 1 hour or more, more preferably 3 hours or more, and even more preferably 10 hours or more.

[0099]

In the case where the final calcination is performed again after completion of the precalcination, the low temperature treatment is preferably carried out at the final calcination.

[0100]

The time required for low temperature treatment, i.e. the time required to raise the temperature of the dried powder and/or complex oxide catalyst to the calcination temperature after lowering the temperature, can be appropriately adjusted by the size, thickness and material of the calciner, the amount of catalyst obtained, a number of continuous calcination periods dried powder and/or complex oxide catalyst, fixing speed/degree of fixing and the like. For example, in the case where a SUS calcination pipe with an inner diameter of 500 mm, a length of 4500 mm and a thickness of 20 mm is used, the time required for the low temperature treatment is preferably within 30 days, more preferably within 15 days, even more preferably within within 3 days, and particularly preferably within 2 days during a series of periods of continuous calcination of the catalyst.

[0101]

For example, in the case where the dried powder is supplied at a speed of 35 kg/h, the dried powder is rotated at 6 rpm in a rotary kiln containing a SUS calcination tube with an inner diameter of 500 mm, a length of 4500 mm and a thickness of 20 mm, and the final calcination temperature is set to 645°C, the step of lowering the temperature to 400°C, and then raising the temperature to 645°C can be carried out in about one day. In the case where the calcination is carried out for one year continuously, carrying out this low temperature treatment once a month, the calcination can be carried out while the temperature of the oxide layer is kept stable.

[0102]

[Method for producing unsaturated nitrile]

The process for producing an unsaturated nitrile of the present embodiment produces an unsaturated nitrile by carrying out a gas-phase catalytic ammoxidation reaction on propane or isobutane in the presence of the oxide catalyst of the present embodiment.

[0103]

(original substance)

Propane or isobutane and ammonia as raw materials need not be of high purity, and industrial grade gases such as propane containing 3 vol% or less impurities such as ethane, ethylene, n-butane, ammonia can be used containing 3 vol.% or less impurities such as water. The oxygen-containing gas is not particularly limited, for example, air, oxygen-enriched air, pure oxygen, a gas obtained by diluting any of them with an inert gas such as helium, argon, carbon dioxide or nitrogen, or steam can also be provided for the reaction. Among them, in the case where the oxygen-containing gas is used commercially, air is preferably used from the viewpoint of simplicity.

[0104]

(reaction conditions)

The gas-phase catalytic ammoxidation reaction of propane or isobutane can be carried out, for example, but they are not specifically limited, under the following conditions. The molar ratio of oxygen to be fed to the reaction to propane or isobutane is preferably 0.1-6, and more preferably 0.5-4. The molar ratio of ammonium to be fed to the reaction to propane or isobutane is preferably 0.3-1.5, and more preferably 0.7-1.2.

[0105]

The reaction temperature is preferably 350-500°C, and more preferably 380-470°C. The reaction pressure is preferably 5×10 ⁴ -5×10 ⁵ Pa, and more preferably 1×10 ⁵ -3×10 ⁵ Pa. The contact time is preferably 0.1-10 sec.g/cm ³ , and more preferably 0.5-5 sec.g/cm ³ . By setting the conditions for the gas-phase catalytic ammoxidation reaction in the above-described ranges, there is a tendency that the production of by-products is suppressed, and the yield of unsaturated nitrile can be further increased.

[0106]

In the present embodiment, the contact duration is determined by the following equation.

Contact duration (sec g/cm ³ ) = (W/F) × 273/(273+T)

where W, F, and T are defined as follows.

W=amount (g) filled catalyst

F=flow rate (N cm ³ /sec) of the mixed gas of the original substance in the standard state (0°C, 1.013 × 10 ⁵ Pa)

T=reaction temperature (°C)

[0107]

As the reaction system in the gas-phase catalytic ammoxidation reaction, a standard system such as a fixed bed, a fluidized bed, and a moving bed can be adopted. Among them, a fluidized bed reactor is preferable, with which heat of reaction is easily removed. The gas phase catalytic ammoxidation reaction can be single stream or recirculating.

Examples

[0108]

Hereinafter, the present embodiment will be described in more detail with specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples at all to the extent not going beyond the gist of the present embodiment. The respective physical properties and evaluations made in the examples and comparative examples to be mentioned below were measured by the following methods.

[0109]

[Example 1]

<Acquisition stage A; obtaining an aqueous mixed liquid (A ₁ )>

To 2572 g of water was added 436.4 g of ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ ∙4H ₂ O] and 54.6 g of ammonium metavanadate [NH ₄ VO ₃ ], 91.4 g of distimine trioxide [Sb ₂ O ₃ ] and 5.4 g of cerium nitrate [Ce(NO ₃ ) ₃ .6H ₂ O], and the resulting mixture was heated at 98°C for 2 hours with stirring to obtain an aqueous mixed liquid (A ₁ ).

[0110]

<Acquisition stage B; obtaining liquid niobium starting material (B ₁ )>

The niobium starting material liquid was obtained by the following method. 57.9 kg of water was added to the mixer, and then the water was heated to 45°C. Then, 72.2 kg of oxalic acid dihydrate [H ₂ C ₂ O ₄ .2H ₂ O] was charged with stirring, and then 19.9 kg of niobic acid containing 76.0% by mass of Nb ₂ O ₅ was charged to mix both in water. This liquid was stirred while heating at 70° C. for 8 hours, and thereby an aqueous mixed liquid was obtained. This aqueous mixed liquid was left to stand and cooled on ice, and then the solid residue was filtered and separated by suction filtration to obtain a homogeneous liquid of the niobium starting material (B ₁ ). By the analysis described below, it was determined that the molar ratio of oxalic acid/niobium in this liquid of the niobium starting material was 2.11. The resulting niobium precursor liquid was used as the niobium precursor liquid (B ₁ ) in the preparation of the oxide catalysts of Examples 2 to 5 described below.

[0111]

The molar ratio of oxalic acid/niobium in the liquid of the niobium starting material (B ₁ ) was calculated as described below. After heat treatment such that the liquid of the niobium raw material (B ₁ ) was stirred at 40°C for 20 minutes after one day after the production was carried out, and the liquid of the niobium substance (B1) was left to stand at 20°C for 7 days after the heat processing, measured the molar ratio of oxalic acid/niobium and turbidity.

[0112]

The concentration of Nb in the aqueous mixed liquid was calculated from the weight of the solid Nb ₂ O ₅ obtained in such a way that 10 g of the liquid of the niobium starting material (B ₁ ) was accurately weighed in a crucible dried at 120°C for 2 hours, and then subjected to heat treatment at 600°C for 2 hours, determining that the Nb concentration is 1.072 mol/kg.

[0113]

In a 300 ml beaker, 3 g of liquid niobium starting material (B ₁ ) was precisely weighed, 20 ml of hot water at approximately 80° C. was added, and then 10 ml of 1:1 sulfuric acid was added. The mixed liquid thus obtained was titrated with stirring using 1/4N KMnO ₄ while the temperature of the liquid was maintained at 70° C. in a water bath. The point at which a faint pale pink color due to KMnO4 persisted for about 30 seconds or more was defined as the end point. The concentration of oxalic acid was calculated from the titrated amount according to the following formula, finding that the concentration of oxalic acid was 2.26 mol/kg.

2KMnO ₄ +3H ₂ SO ₄ +5H ₂ C ₂ O ₄ → K ₂ SO ₄ +2MnSO ₄ +10CO ₂ +8H ₂ O

[0114]

Haze was measured using a 2100AN turbidimeter manufactured by HACH after the liquid of the niobium starting material (B ₁ ) was allowed to stand for another day after preparation. 30 ml of a measurement solution based on US EPA method 180.1 was placed in the measuring cell, finding that the turbidity of the liquid of the niobium starting material (B ₁ ) was 69 NMU.

[0115]

<Mixing stage; obtaining a suspension of precursors (C ₁ )>

After cooling the resulting aqueous mixed liquid (A ₁ ) to 70°C, 593.8 g of a silica sol containing 34.1% by mass of SiO ₂ was added to the aqueous mixed liquid (A ₁ ), and then at the time when the temperature of the liquid became 55° C., 181 g of a hydrogen peroxide solution containing 30% by mass of H ₂ O ₂ was added to obtain an aqueous mixed liquid (A ₁ '). Immediately thereafter, 309.1 g of the liquid of the niobium starting material (B ₁ ), 34.2 g (50% purity) of an aqueous solution of ammonium metatungstate, and a dispersion liquid obtained by dispersing 247.5 g of powdered silica in 2228 g of water were added successively to the aqueous mixed liquid (A ₁ ), then added 51.7 g of 25% ammonia water, and the resulting mixture was subjected to keeping under stirring at 65°C for 2.5 hours, obtaining a suspension of precursors (C ₁ ).

[0116]

<Drying stage; getting dried powder (E ₁ )>

The resulting suspension of precursors (C1) was fed into a centrifugal spray dryer and dried to obtain a microspheric dried powder (D1). Air was used as a heat source for drying. It should be noted that the same heat source for drying was used in the centrifugal spray dryer in the following examples and comparative examples. The dryer inlet temperature was 210°C and the outlet temperature was 120°C. The resulting dried powder (D1) was sorted using a 32 µm sieve to obtain a dried powder (E1) which is a graded product.

[0117]

<Ignition step; production of an oxide catalyst (F ₁ )>

In PYREX, a calcination tube (PYREX is a registered trademark) having a diameter of 3 inches was filled with 100 g of the resulting dried powder (E ₁ ) and calcined at 685° C. for 2 hours under a nitrogen flow of 5.0 Nl/min by rotating the pipe, and thereby an oxide catalyst (F ₁ ) was obtained.

[0118]

<deletion stage>

A vertical tube (inner diameter 41.6 mm, length 70 cm) equipped with a disk with three 1/64 inch diameter holes at the bottom and a paper filter installed at the top was loaded with 50 g of oxide catalyst (F1). The air was then allowed to flow from the bottom up the vertical tube through the appropriate holes at room temperature to facilitate contact between the calcined particles. The length of the air flow in this case in the direction in which it passed was 56 mm, and the average linear speed of the air flow was 332 m/s. After 24 hours, there were no protrusions in the obtained oxide catalyst (F1).

[0119]

<Physical property 1; analysis of the composition of catalytically active particles (G ₁ ) STEM-EDX

In a 500 ml assay beaker, 200 g of a hydrogen peroxide solution containing 10% by mass H ₂ O ₂ was placed, and the water temperature was set to 27°C. To this hydrogen peroxide solution, 15 g of an oxide catalyst (F ₁ ) was added after the projections were removed, and stirred using a magnetic stirrer at 500 rpm for 5 hours, and then an insoluble component was obtained by suction filtration. The obtained insoluble component was dried at 50°C for 12 hours, collecting the residue (H1). The collected residue (H1) was such that other crystals other than the catalytically active species (G1) and carrier (eg silica) were removed by oxidative treatment with hydrogen peroxide solution, and it contains the catalytically active species (G1) and carrier.

[0120]

The resulting residue (H1) was ground in a mortar for 30 seconds to obtain a powder sample. In a vessel with an internal volume of 10 ml, 0.1 g of the resulting powder sample and 6 ml of ethanol were placed. The vessel was placed in a tabletop ultrasonic washing machine (YAMATO BRANSON, manufactured by Yamato Scientific Co., Ltd.) and subjected to ultrasonic vibration for 60 seconds while dispersing a sample of residue powder (H1) in ethanol.

[0121]

Thereafter, this ethanol liquid dispersion of the powder sample was dropped onto a Cu mesh with a carbon support membrane (elastic carbon support membrane; mesh pitch 100 μm; manufactured by Okenshoji Co., Ltd.), and then the liquid drop was held for about one minute and then removed with filter paper and the like. Thus, a sample was obtained such that the catalyst particle in the liquid dispersion was placed on the Cu mesh carbon support membrane. The thus prepared sample was observed using STEM-EDX.

[0122]

A scanning transmission electron microscope equipped with an energy dispersive X-ray spectrometer (STEM-EDX) was used to quantify the catalytically active species (G1) in the powder sample. An HD2300A (manufactured by Hitachi Hi-Tech Corporation) was used as a scanning transmission electron microscope (STEM), and an Apollo XLT2 SUTW (manufactured by AMETEK, Inc) was used as an energy dispersive X-ray spectrometer (EDX). Genesis (Ver 6.53, manufactured by AMETEK, Inc.) was used as the EDX measurement and analysis software.

[0123]

The energy calibration method for EDX was as follows. A sample was used in which Al and Cu were present, and the sample was irradiated with an electron beam accelerated to 200 kV to detect characteristic X-rays. In the characteristic X-ray spectrum detected in this case, a measurement site was chosen where the peak intensity of the Al-Kα radiation was approximately the same or somewhat greater than the peak intensity of the Cu-Kα radiation, and the number of pulses (CPS) became equal to 1000-5000 pulses ./With. Energy values were calibrated by applying the calibration function in the software, setting the number of measurements to 5, setting peak 1 to the energy value of the Al-Kα beam ((1486 eV) and setting peak 2 to the energy value of the Cu-Kα beam (8.04 eV) .

[0124]

The conditions for measuring the characteristic X-ray radiation were as follows. The accelerating voltage was 200 kV, operating mode; normal, the objective aperture was No. 2 (hole diameter 60 µmɸ, irradiation angle about 15 mrad), the spectrometer tilt angle was 26°, the EDX aperture was inserted to measure the spectrum by area analysis in such a way as to include the periphery of the central part of the catalyst particle. The measurement was carried out under EDX detection conditions: time constant 7.68 µs and integration time from 70 to 80 s.

[0125]

A thin film correction method (Thin Apex) for STEM was used as a quantitation method. Quantification was carried out using L-beams for Nb, Mo, Sb and W, and K-beams for V. As K-factors for use in quantification, the values recorded in the software were used, Nb-L: 3.52, MoL; 3.62, Sb-L; 5.59, V-K; 1.34 and WL; 7.68 (K-factors, which are recommended values by the device manufacturer; AMETEK EDAX). The density of the quantification sample was set to 7.8 g/cm ³ (average density of Nb, Mo, Sb and V), and the film thickness was set to 50 nm. Quantification was carried out by setting the background elimination to the automatic setting.

[0126]

The measurement was carried out at 15 points, and the composition of the catalytically active particles (G ₁ ) was calculated by taking the average of them. In the case where the carrier (for example, silica) was calculated as a composition, silica was excluded from the measurement results. The particle present as a crystal in the sample was only the catalytically active species (G ₁ ) due to the above oxidative treatment with the hydrogen peroxide solution. Accordingly, by observing a particle in which transverse bands are observed among the observed particles, reflecting the periodicity of crystals, catalytically active particles (G1) can be effectively detected in the field of view. The composition of catalytically active particles (G1) is presented in table 1.

[0127]

<Physical property 2; evaluation of reactivity in propane ammoxidation reaction>

Propane was fed into the gas-phase catalytic ammoxidation reaction in the following manner using the oxide catalyst (F ₁ ) obtained above. In a VYCOR glass fluidized bed reaction tube with an inner diameter of 25 mm, 40 g of an oxide catalyst was filled, and a mixed gas having a molar ratio of propane:ammonia:oxygen:helium=1:1.1:2.9:11.6 was supplied, at contact time 3.0 (sec∙g/cm3) at a reaction temperature of 445°C and a reaction pressure of 40 kPa.

[0128]

The acrylonitrile yield was determined as follows. After obtaining a calibration curve in advance by analyzing the gas of acrylonitrile at a known concentration by gas chromatography (GC: product name "GC 2014" manufactured by SHIMADZU CORPORATION), the gas obtained by the ammoxidation reaction was quantitatively injected into the GC, and the number of moles of acrylonitrile was measured. The yield of acrylonitrile was determined by the number of moles of acrylonitrile measured according to the following equation.

Yield of acrylonitrile (%)=(moles of acrylonitrile produced)/(moles of propane supplied)×100

The reaction was continuously carried out with this catalyst (F1), and the yield of acrylonitrile (AN) measured 10 days after the start of the reaction is shown in Table 1.

[0129]

<Physical Property 3; measuring the amount of catalyst>

The amount of catalyst was determined as the amount (% by mass) of the SiO ₂ support based on the total amount (100% by mass) of the oxide catalyst (F ₁ ), and the resulting oxide catalyst (F ₁ ) was crushed/mixed for two hours using an automatic agate mortar of a single axis type (manufactured by NITTO KAGAKU CO., LTD.) and pressed into a vinyl chloride ring (manufactured by Rigaku Corporation) with a single axis press. The measurement by semi-quantitative analysis was carried out on the obtained precipitate by the fundamental parameter (FP) method, in which the relative content is determined from the sensitivity library registered in the software in advance, using wavelength dispersive X-ray fluorescence analysis (trade name "RIX 1000", manufactured Rigaku Corporation, chromium tube, tube voltage 50 kV, tube current 50 mA). The mass fraction (I1) (%) of the carrier (for example, silicon dioxide) determined by this measurement is shown in Table 1.

[0130]

<Physical property 4; measurement of the composition and amount of catalytically active particles by X-ray fluorescence analysis>

Composition analysis by X-ray fluorescence was carried out on a pellet obtained by grinding/mortar-mixing the residue (H1) obtained from the measurement of physical property 1 to perform molding in the same manner as for physical property 3. Mass fraction (J ₁ ) (% ) catalytically active particles (G1), assuming that the mass of the complex oxide was 100%, can be calculated from the determined mass fraction (I ₂ ) (%) of the carrier and the mass fraction (I ₁ ) (%) of the carrier in the oxide catalyst (F1), measured for physical property 3 using the following equation. The resulting mass fraction (J ₁ ) (%) of catalytically active particles is presented in table 1.

[0131]

[Example 2]

An oxide catalyst was prepared in the same manner as in Example 1, except that the added amount of water was changed to 2564 g, the added amount of ammonium heptamolybdate was changed to 440.9 g, the added amount of ammonium metavanadate was changed to 52.2 g, the added amount of trioxide diantimony was replaced by 90.5 g, the added amount of cerium nitrate was replaced by 5.49 g, the niobium starting material liquid (B ₁ ) that was added was replaced by 300.7 g in obtaining an aqueous mixed liquid (A ₁ ), and the added amount hydrogen peroxide solution was changed to 179.2 g, the added amount of silica sol was changed to 593.8 g, the added amount of ammonium metatungstate aqueous solution was changed to 34.6 g, the added amount of silica powder was changed to 247.5 g, and the added amount water was replaced by 2228 g in the mixing step for the precursor slurry (C ₁ ), and the evaluation of physical properties 1-3 was carried out in the same way as in example 1.

[0132]

[Example 3]

An oxide catalyst was prepared in the same manner as in Example 1, except that the added amount of water was changed to 2732 g, the added amount of ammonium heptamolybdate was changed to 421.1 g, the added amount of ammonium metavanadate was changed to 63.8 g, the added amount of trioxide diantimony was replaced by 76.1 g, the added amount of cerium nitrate was replaced by 5.25 g, the niobium starting material liquid (B ₁ ) that was added was replaced by 176.8 g to obtain an aqueous mixed liquid (A ₁ ), and the added amount hydrogen peroxide solution was changed to 192.3 g, the added amount of silica sol was changed to 862.2 g, the added amount of ammonium metatungstate aqueous solution was changed to 33.0 g, the added amount of silica powder was changed to 196.0 g, and the added amount water was replaced by 1764 g in the mixing step for the precursor slurry (C ₁ ), and the evaluation of physical properties 1-3 was carried out in the same way as in example 1.

[0133]

[Example 4]

An oxide catalyst was prepared in the same manner as in Example 1, except that the added amount of water was changed to 2909 g, the added amount of ammonium heptamolybdate was changed to 448.3 g, the added amount of ammonium metavanadate was changed to 67.9 g, the added amount of trioxide diantimony was replaced by 84.7 g, the added amount of cerium nitrate was replaced by 5.6 g, the niobium starting material liquid (B ₁ ) that was added was replaced by 211.7 g to obtain an aqueous mixed liquid (A ₁ ), and the added amount hydrogen peroxide solution was changed to 166.7 g, the added amount of silica sol was changed to 791.8 g, the added amount of ammonium metatungstate aqueous solution was changed to 35.2 g, the added amount of silica powder was changed to 180.0 g, and the added amount water was replaced by 1620 g in the mixing step for the precursor slurry (C ₁ ), and the evaluation of physical properties 1-3 was carried out in the same way as in example 1.

[0134]

[Example 5]

An oxide catalyst was prepared in the same manner as in Example 1, except that an aqueous solution of ammonium metatungstate was not added in the mixing step for the precursor slurry (C ₁ ), and evaluation of physical properties 1-3 was carried out in the same manner as in Example 1 .

[0135]

[Example 6]

An aqueous mixed liquid (A ₁ ) was obtained in the same manner as in Example 1, except that water was replaced by 25 kg, ammonium heptamolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ ∙4H ₂ O] was replaced by 4.088 kg, ammonium metavanadate [NH ₄ VO ₃ ] was replaced by 0.646 kg, disantimony trioxide [Sb ₂ O ₃ ] was replaced by 0.907 kg, and cerium nitrate was replaced by 0.051 kg, and the resulting mixture was heated at 95°C for 1 hour with stirring upon receipt of an aqueous mixed liquid (A ₁ ).

[0136]

The liquid of the niobium starting material (B ₁ ) was obtained in the same manner as in Example 1, except that the aqueous mixed liquid obtained by replacing water with 77.3 kg of oxalic acid dihydrate [H ₂ C ₂ O ₄ ∙2H ₂ O ] by 57.0 kg, and niobic acid by 15.7 kg, and stirring the resulting mixture while heating at 73°C for 6 hours, cooled to 40°C by natural cooling with stirring to obtain a liquid niobium raw material (B ₁ ).

[0137]

The oxalic acid/niobium molar ratio and the liquid turbidity of the niobium starting material (B ₂ ) were measured in the same manner as in Example 1. As a result, the Nb concentration was found to be 0.756 mol/kg, the oxalic acid concentration was 1.74 mol/kg. kg, and the turbidity was 32 NM.

[0138]

After cooling the obtained aqueous mixed liquid (A ₁ ) to 70° C., 7.038 kg of a silica sol containing 34.0% by mass of SiO ₂ , 1.06 kg of a solution of hydrogen peroxide containing 30% by mass of H ₂ O ₂ were added, was further added to the aqueous mixed liquid (A ₁ ), and stirring was continued at 55° C. for 30 minutes. After additional sequential addition of a dispersion liquid obtained by dispersing 3.850 kg of a liquid of a niobium raw material (B ₁ ) and 2.4 kg of silica powder (trade name "AEROSIL 200", manufactured by NIPPON AEROSIL Co., Ltd.) in 197.6 kg of water , and 0.319 kg of an ammonium metatungstate liquid containing 50.2% by weight of tungsten oxide to the liquid, the resulting mixture was stirred at 50° C. for 2.5 hours to obtain a suspension of precursors (C ₁ ).

[0139]

An oxide catalyst was prepared in the same manner as in Example 1 except as described above, and physical property evaluation 1-3 was carried out in the same manner as in Example 1.

[0140]

[Example 7]

An oxide catalyst was prepared in the same manner as in Example 6, except that water was replaced by 83.2 kg, oxalic acid dihydrate [H ₂ C ₂ O ₄ .2H ₂ O] was replaced by 52.3 kg, and niobic acid was replaced by 14.5 kg, and the resulting mixture was stirred with heating at 78° C. for 5 hours to obtain a niobium starting material (B ₁ ) liquid, and evaluation of physical properties 1-3 was carried out in the same manner as in Example 1 .

[0141]

The molar ratio of oxalic acid/niobium and the turbidity of the resulting liquid of the niobium starting material (B ₁ ) were measured in the same manner as in Example 1. As a result, the concentration of niobium was found to be 0.753 mol/kg, the concentration of oxalic acid was 1.77 mol /kg, and the turbidity was 41 NM.

[0142]

[Comparative Example 1]

88.7 kg of water was added to the mixer, and then the water was heated to 50°C. Then, 48.1 kg of oxalic acid dihydrate [H ₂ C ₂ O ₄ ∙2H ₂ O] was charged with stirring, and then 13.2 kg of niobic acid containing 76.3% by mass of Nb ₂ O ₅ was charged, mixing both in water. The aqueous mixed liquid obtained by stirring this liquid while heating at 95°C for 3 hours was cooled to 40°C by natural cooling while stirring. Then, the aqueous mixed liquid was cooled to 2°C at -10°C/h and left to stand for 1 hour. Then, the mixture of the precipitated solid and the mixed liquid was poured onto the filter, and the mixed liquid was obtained by filtering the precipitated solid.

[0143]

An oxide catalyst was obtained in the same manner as in Example 1, except that the resulting mixed liquid was used as the liquid of the niobium starting material (B ₁ ), and the evaluation of physical properties 1-3 was carried out in the same manner as in Example 1 Analysis of the resulting liquid of niobium precursor (B ₁ ) was carried out in the same manner as in Example 1, finding that the Nb concentration of this liquid of niobium precursor (B ₁ ) was 0.578 mol/kg, the molar ratio of oxalic acid/niobium was 2, 77 and the turbidity is 201 NMU.

[0144]

[Comparative Example 2]

An oxide catalyst was obtained in the same manner as in Example 3, except that the preparation was carried out using a liquid of a niobium starting material (B ₁ ) obtained in the same manner as in Comparative Example 1, and evaluation of physical properties 1-3 was carried out by in the same way as in example 1.

[0145]

[Comparative Example 3]

An oxide catalyst was obtained in the same manner as in Example 5, except that the preparation was carried out using a liquid of a niobium starting material (B ₁ ) obtained in the same manner as in Comparative Example 1, and evaluation of physical properties 1-3 was carried out by in the same way as in example 1.

[0146]

[Example 8]

An oxide catalyst was obtained in the same manner as in Example 1, except that the amount of water charged was replaced by 67.5 kg, oxalic acid dihydrate [H ₂ C ₂ O ₄ ∙2H ₂ O] was replaced by 64.6 kg, niobium the acid was replaced by 17.9 kg, and the resulting mixture was stirred with heating at 95° C. for 4 hours to obtain a niobium starting material (B ₁ ) liquid, and evaluation of physical properties 1-3 was carried out in the same manner as in Example 1.

[0147]

[Comparative Example 4]

An oxide catalyst was prepared in the same manner as in Example 6, except that the preparation of the liquid of the niobium starting material (B ₁ ) was carried out in the same manner as in Example 8, and the evaluation of physical properties 1-3 was carried out in the same manner as in example 1.

[0148]

[Table 1]

Composition of active particles (G1) Amount of carrier based on silicon dioxide I1 (%) Number of catalytically active particles J ₁ (%) Acrylonitrile Yield (%) Example 1 Mo ₁ V _0.125 Sb _0.112 Nb _0.200 W _0.054 48.5 48.7 56.8 Example 2 Mo ₁ V _0.095 Sb _0.098 Nb _0.185 W _0.052 48.6 52.5 57.0 Example 3 Mo ₁ V _0.140 Sb _0.076 Nb _0.175 W _0.051 52.1 43.4 56.0 Example 4 Mo ₁ V _0.120 Sb _0.103 Nb _0.196 W _0.053 48.3 43.1 56.2 Example 5 Mo ₁ V _0.123 Sb _0.110 Nb _0.198 W _0.000 48.4 48.5 56.7 Example 6 Mo ₁ V _0.121 Sb _0.108 Nb _0.151 W _0.048 48.2 44.5 56.2 Example 7 Mo ₁ V _0.128 Sb _0.089 Nb _0.162 W _0.051 48.2 44.3 56.2 Example 8 Mo ₁ V _0.124 Sb _0.098 Nb _0.160 W _0.049 48.3 44.2 56.3 Comparative Example 1 Mo ₁ V _0.143 Sb _0.020 Nb _0.212 W _0.051 48.6 15.8 35.0 Comparative Example 2 Mo ₁ V _0.153 Sb _0.056 Nb _0.106 W _0.051 51.9 30.6 53.0 Comparative Example 3 Mo ₁ V _0.199 Sb _0.082 Nb _0.097 W _0.000 48.2 25.8 52.0 Comparative Example 4 Mo ₁ V _0.154 Sb _0.075 Nb _0.144 W _0.047 48.2 40.5 55.0

Claims (11)

1. An oxide catalyst for use in a gas phase catalytic propane or isobutane ammoxidation reaction, wherein the oxide catalyst contains a complex oxide in which the complex oxide contains catalytically active particles that are separated from the complex oxide using a hydrogen peroxide solution, and these catalytically active particles have an average composition determined by measurements using STEM-EDX, represented by the following formula (1): Mo ₁ V _a Sb _b Nb _c W _d O _n (1), where a, b, c and d satisfy the ratios represented by the formulas 0.050≤a≤0.200, 0.050≤b≤0.200, 0.100≤c≤0.300, 0≤d≤0.100, and a≤c; and n is a number determined by the valences of the other elements. 2. The oxide catalyst according to claim. 1, where the formula (1) satisfies the relationship represented by the formula 1.1×a≤c. 3. The oxide catalyst according to claim. 1, where the formula (1) satisfies the relationship represented by the formula 1.3×a≤c. 4. Oxide catalyst according to any one of paragraphs. 1-3, where the formula (1) satisfies the relationship represented by the formula 8.00≤100×b/(1+a)≤10.00. 5. Oxide catalyst according to any one of paragraphs. 1-4, where the oxide catalyst contains silicon dioxide as a support supported by a complex oxide, and the mass fraction of silicon dioxide is from 30 to 70% by weight in terms of SiO ₂ relative to the total amount of oxide catalyst. 6. Oxide catalyst according to any one of paragraphs. 1-5, in which the complex oxide contains catalytically active particles containing molybdenum, vanadium, antimony and niobium, and the mass fraction of catalytically active particles is 45% by mass or more of the total amount of the complex oxide. 7. The method of obtaining unsaturated nitrile, and the method includes obtaining unsaturated nitrile by the reaction of gas-phase catalytic ammoxidation of propane or isobutane in the presence of an oxide catalyst according to any one of paragraphs. 1-6.