Method for producing gas-phase catalytic oxidation reaction catalyst, method for producing unsaturated nitrile, and method for producing alkene

Abstract

The objective of the present invention is to provide a method for producing a gas-phase catalytic oxidation reaction catalyst exhibiting excellent thermal stability and excellent catalytic activity compared with a conventional catalyst. This method for producing a gas-phase catalytic oxidation reaction catalyst comprises a step (X) for obtaining a gas-phase catalytic oxidation reaction catalyst by firing, in a reactor, a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or more and less than 450°C, under a gas atmosphere containing water vapor and at a temperature of 400°C or higher.

Description

Method for producing a catalyst for gas-phase catalytic oxidation reaction, method for producing unsaturated nitrile, and method for producing alkene

[0001] The present invention relates to a method for producing a catalyst for gas-phase catalytic oxidation reaction, and a method for producing an unsaturated nitrile and an alkene using the catalyst for gas-phase catalytic oxidation reaction.

[0002] The process of producing unsaturated nitriles by reacting olefins with molecular oxygen and ammonia is known as the "ammoxidation reaction," and this reaction is used worldwide as an industrial process for producing unsaturated nitriles. Meanwhile, in recent years, attention has been focused on a process for producing the corresponding unsaturated nitriles by performing a gas-phase catalytic ammoxidation reaction using alkanes such as propane or isobutane as raw materials instead of olefins, and a method for producing the catalyst has also been attracting attention.

[0003] Patent Document 1 proposes a method for producing a corresponding unsaturated nitrile by subjecting propane or isobutane to a gas-phase catalytic ammoxidation reaction with ammonia and molecular oxygen in the presence of an oxide catalyst containing molybdenum, vanadium, antimony, and niobium but not containing tellurium in the catalyst preparation stage, and for adding a tellurium compound, or a tellurium compound and a molybdenum compound, to the fluidized bed reactor during the production.

[0004] Patent Document 2 proposes a method for stabilizing an antimony ammoxidation catalyst in a gas-phase catalytic ammoxidation reaction process, in which acrylonitrile is produced by reacting propylene with ammonia and oxygen in the presence of an antimony ammoxidation catalyst in a fluidized bed reactor, by adding an effective amount of an antimony-containing compound having a melting point of less than 375°C to the antimony ammoxidation catalyst during the reaction, thereby maintaining the conversion and selectivity of the catalyst.

[0005] Patent No. 4484995 Patent No. 7278396

[0006] The catalysts for producing acrylonitrile described in Patent Documents 1 and 2 can improve the yield of unsaturated nitrile, but there is a recent trend toward even higher catalytic performance, and therefore there is room for further improvement.

[0007] According to Patent Document 1, an attempt has been made to carry out the reaction while supplying a molybdenum-containing material as a method for maintaining catalyst efficiency, and according to Patent Document 2, an attempt has been made to maintain catalyst conversion and selectivity by adding a low-melting-point antimony-containing compound to the antimony ammoxidation catalyst in the reactor.

[0008] However, supplying only a molybdenum-containing compound leaves much room for improvement in performance, and the addition of a low-melting-point antimony-containing compound places limitations on the antimony-containing compound and raises concerns about thermal stability.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing a gas-phase catalytic oxidation catalyst, which can produce a gas-phase catalytic oxidation catalyst having superior thermal stability and catalytic activity compared to conventional catalysts, as well as a method for producing an unsaturated nitrile using the catalyst, which can produce an unsaturated nitrile in high yield, and a method for producing an alkene using the catalyst, which can produce an alkene in high yield.

[0010] As a result of investigations aimed at solving the above-mentioned problems, the present inventors discovered that by subjecting a catalyst to a predetermined treatment, it is possible to design a catalyst in which the amount of antimony (Sb) oxide in the gas-phase catalytic oxidation reaction catalyst falls within a predetermined range, thereby solving the above-mentioned problems and completing the present invention.

[0011] That is, the present invention is as follows: [1] A method for producing a gas-phase catalytic oxidation catalyst, comprising a step (X) of calcining a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher but lower than 450°C in a reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor, to obtain a gas-phase catalytic oxidation catalyst. [2] A method for producing the gas-phase catalytic oxidation catalyst according to the above [1], wherein in the step (X), the composite oxide, the antimony-containing compound, and the molybdenum-containing compound are calcined in the reactor. [3] A method for producing the gas-phase catalytic oxidation catalyst according to the above item [1], comprising: a step (A1) of adding a composite oxide containing at least Mo, V, and Sb into a reactor, and maintaining the reactor in a temperature condition of 300°C or higher and a gas atmosphere containing water vapor; and a step (A2) of adding an antimony-containing compound having a melting point of 375°C or higher and lower than 450°C into the reactor, and firing the reactor in a gas atmosphere containing water vapor at a temperature of 400°C or higher, thereby obtaining a gas-phase catalytic oxidation catalyst; or a step (B1) of adding a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher and lower than 450°C into a reactor, and maintaining the reactor in a temperature condition of 300°C or higher and a gas atmosphere containing water vapor; and a step (B2) of firing the reactor in a gas atmosphere containing water vapor at a temperature of 400°C or higher, thereby obtaining a gas-phase catalytic oxidation catalyst. [4] The method for producing a gas-phase catalytic oxidation catalyst according to the above [3], wherein in the step (A2), the antimony-containing compound is added to the reactor at a temperature condition of not less than the melting point of the antimony-containing compound and in a gas atmosphere containing water vapor. [5] The method for producing a gas-phase catalytic oxidation catalyst according to the above [3], wherein in the steps (A2) and (B1), the antimony-containing compound is added to the reactor at a temperature condition of not less than the melting point of the antimony-containing compound, and in the steps (A2) and (B1) or (B2), the temperature inside the reactor is raised to not less than the melting point of the antimony-containing compound in a gas atmosphere containing water vapor.[6] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [3] to [5] above, wherein in steps (A2) and (B1), a molybdenum-containing compound is added to the reactor together with an antimony-containing compound. [7] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [3] to [6] above, wherein in steps (A1) and (B1), an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms is reacted with ammonia and molecular oxygen in a gas phase at 300°C or higher to generate water vapor in the reactor, and the reactor is then placed under a gas atmosphere containing water vapor. [8] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [3] to [7] above, wherein in steps (A2) and (B2), an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms is reacted with ammonia and molecular oxygen in the gas phase at 300°C or higher, while calcining the reaction mixture in the reactor under a gas atmosphere containing water vapor. [9] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [1] to [8] above, wherein the composite oxide comprises a composite oxide obtained by drying and calcining a raw material mixed liquid containing at least a molybdenum-containing compound, a vanadium-containing compound, and an antimony-containing compound.

[10] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [1] to [9] above, wherein the concentration of water vapor contained in the gas atmosphere is 5% by volume or more.

[11] A method for producing the gas-phase catalytic oxidation catalyst according to any one of [1] to

[10] above, wherein the average particle size of the gas-phase catalytic oxidation catalyst is 35 μm or more and 75 μm or less.

[12] The gas-phase catalytic oxidation catalyst comprises a metal oxide, and the metal oxide is represented by the following formula (1): Mo. １ V ａ Sb ｂ Nb ｃ T ｄ Z ｅ O ｎ... (1) (In formula (1), T represents at least one element selected from the group consisting of Ti, W, Mn and Bi, Z represents at least one element selected from the group consisting of La, Ce, Yb and Y, a, b, c, d and e represent atomic ratios of each element when Mo is taken as 1, and are in the ranges of 0.05≦a≦0.35, 0.05≦b≦0.35, 0≦c≦0.25, 0≦d≦0.20 and 0≦e≦0.10, respectively, and n is a value that satisfies the valence balance.) A method for producing the gas-phase catalytic oxidation catalyst according to any one of the above [1] to

[11] .

[13] A method for producing the gas-phase catalytic oxidation catalyst according to any one of the above [1] to

[12] , wherein the gas-phase catalytic oxidation catalyst comprises a support.

[14] A method for producing the gas-phase catalytic oxidation catalyst according to the above

[13] , wherein the support comprises a silica support.

[15] The method for producing the catalyst for gas-phase catalytic oxidation reaction according to any one of [1] to

[14] above, wherein the reactor is a fluidized bed reactor.

[16] The method for producing the catalyst for gas-phase catalytic oxidation reaction according to any one of [1] to

[15] above, wherein the amount of antimony on the surface of the catalyst for gas-phase catalytic oxidation reaction is 10 mass % or more and 50 mass % or less when the catalyst for gas-phase catalytic oxidation reaction is measured with a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX) (accelerating voltage 10 kV).

[17] A method for producing an unsaturated nitrile, comprising: a step (N) of reacting an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms with ammonia and molecular oxygen in the gas phase in the presence of the catalyst for gas-phase catalytic oxidation produced by the method according to any one of [1] to

[16] above, to obtain an unsaturated nitrile.

[18] A method for producing an alkene having 2 to 6 carbon atoms, comprising: a step (O) of reacting an alkane having 2 to 6 carbon atoms with molecular oxygen in the gas phase in the presence of the gas-phase catalytic oxidation catalyst produced by the production method according to any one of the above items [1] to

[16] , to obtain an alkene having 2 to 6 carbon atoms.

[0012] According to the catalyst production method of the present invention, a vapor-phase catalytic oxidation catalyst having superior thermal stability and catalytic activity compared to conventional catalysts can be produced, and therefore, the use of this catalyst enables the production of unsaturated nitriles and alkenes in high yields.

[0013] Below, we will explain a form for implementing the present invention (hereinafter simply referred to as the ``present embodiment''), but the present invention is not limited to the following embodiment, and various modifications are possible within the scope that does not deviate from the gist of the present invention.

[0014] <<Method for Producing a Gas-Phase Catalytic Oxidation Reaction Catalyst>> The method for producing a gas-phase catalytic oxidation reaction catalyst of this embodiment includes step (X) of calcining a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher but lower than 450°C in a reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor, thereby obtaining a gas-phase catalytic oxidation reaction catalyst. This catalyst production method makes it possible to produce a gas-phase catalytic oxidation reaction catalyst with excellent catalytic activity. Therefore, the catalyst can be used to produce, for example, unsaturated nitriles in high yield.

[0015] In general, solid-phase reactions are significantly affected by the gas-phase atmosphere under heating. In particular, calcination in the presence of water vapor promotes the formation, growth, and decomposition of specific compounds. While the mechanism of action remains largely unknown, it is presumed that the collision of water molecules with the solid surface promotes the scission and recombination of chemical bonds on the solid surface, and that this promotes the diffusion of substances such as ions due to the temporary generation of defects in the structure. Similarly, in the method for producing a gas-phase catalytic oxidation catalyst of this embodiment, the formation, growth, and decomposition of the complex oxide are promoted in a gas atmosphere containing water vapor, and the reaction with the antimony-containing compound proceeds efficiently, resulting in the production of a gas-phase catalytic oxidation catalyst with excellent catalytic activity.

[0016] In a first embodiment, the method for producing a gas-phase catalytic oxidation catalyst of this embodiment preferably includes a step (A1) of adding a composite oxide containing at least Mo, V, and Sb to a reactor and maintaining the reactor at a temperature of 300°C or higher and in a gas atmosphere containing water vapor, and a step (A2) of adding an antimony-containing compound having a melting point of 375°C or higher and lower than 450°C to the reactor and calcining the compound in the reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor, thereby obtaining a gas-phase catalytic oxidation catalyst.

[0017] In the first embodiment, in the step (A2), the antimony-containing compound may be added to the reactor under a temperature condition of not less than the melting point of the antimony-containing compound and in a gas atmosphere containing water vapor. Alternatively, in the step (A2), the antimony-containing compound may be added to the reactor under a temperature condition of not more than the melting point of the antimony-containing compound, and in the step (A2), the temperature inside the reactor may be raised to not less than the melting point of the antimony-containing compound in a gas atmosphere containing water vapor.

[0018] In the second embodiment, the method for producing the gas-phase catalytic oxidation catalyst of this embodiment preferably includes a step (B1) of adding a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher and lower than 450°C to a reactor, and maintaining the interior of the reactor at a temperature of 300°C or higher and in a gas atmosphere containing water vapor; and a step (B2) of calcining the catalyst in the reactor under a gas atmosphere containing water vapor and at a temperature of 400°C or higher, thereby obtaining a gas-phase catalytic oxidation catalyst.

[0019] In the second embodiment, in the step (B1), the antimony-containing compound may be added to the reactor under a temperature condition below the melting point of the antimony-containing compound, and in the step (B1) or (B2), the temperature inside the reactor may be raised to a temperature equal to or higher than the melting point of the antimony-containing compound in a gas atmosphere containing water vapor.

[0020] Steps (A1) and (B1) are steps carried out at 300° C. or higher in a gas atmosphere containing water vapor, preferably at 350° C. or higher, more preferably at 400° C. or higher, even more preferably at 400° C. or higher and 500° C. or lower, still more preferably at 420° C. or higher and 500° C. or lower, still more preferably at 430° C. or higher and 500° C. or lower, and particularly preferably at 440° C. or higher and 500° C. In one embodiment, steps (A1) and (B1) are preferably carried out at a temperature equal to or higher than the melting point of the antimony-containing compound and in a gas atmosphere containing water vapor.

[0021] The temperature conditions for calcining the composite oxide and the antimony-containing compound in steps (X), (A2), and (B2) are 400° C. or higher, preferably 400° C. or higher and 500° C. or lower, more preferably 420° C. or higher and 500° C. or lower, even more preferably 430° C. or higher and 500° C. or lower, and particularly preferably 440° C. or higher and 500° C. In one embodiment, the temperature conditions for calcining the composite oxide and the antimony-containing compound in steps (X), (A2), and (B2) are preferably temperature conditions that are equal to or higher than the melting point of the antimony-containing compound.

[0022] In steps (A2) and (B2), as long as the above-mentioned temperature range is satisfied, firing may be performed under the temperature conditions of step (A1) or (B1) without intentionally changing the temperature conditions by performing heat dissipation, cooling, or temperature increase operations from the temperature conditions of step (A1) or (B1). That is, the temperature conditions for firing in steps (A2) and (B2) may be the same as the temperature conditions under the water vapor-containing gas atmosphere in step (A1) or (B1). In this case, firing in step (A2) begins when the antimony-containing compound (and molybdenum-containing compound) are added. Furthermore, firing in step (B2) begins or progresses when the specified temperature conditions and water vapor-containing gas atmosphere are established in step (B1).

[0023] In steps (X), (A1), and (B1), in order to create a gas atmosphere containing water vapor inside the reactor, water vapor may be supplied to the reactor from the outside, or an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms may be reacted with ammonia and molecular oxygen in the gas phase inside the reactor, i.e., a gas-phase catalytic oxidation reaction (gas-phase catalytic ammoxidation reaction) may be carried out to generate water vapor and create a gas atmosphere containing water vapor. When a gas-phase catalytic oxidation reaction is carried out to create a gas atmosphere containing water vapor, it is not necessary to supply water vapor to the reactor from the outside.

[0024] In steps (X), (A2), and (B2), calcination may be carried out in a reactor under a gas atmosphere containing water vapor while reacting the C alkane or C alkene with ammonia and molecular oxygen in the gas phase, i.e., while carrying out a gas-phase catalytic oxidation reaction. When calcination is carried out while carrying out a gas-phase catalytic oxidation reaction, it is not necessary to supply water vapor from the outside.

[0025] The concentration of water vapor contained in the gas atmosphere in steps (X), (A1), (A2), (B1) and (B2) is preferably 0.1 vol% or more, more preferably 5 vol% or more, and even more preferably 10 vol% or more, relative to 100 vol% of the total volume of the gas. The upper limit of the water vapor concentration is preferably 90 vol% or less, more preferably 60 vol% or less, and even more preferably 50 vol% or less.

[0026] The gas-phase catalytic oxidation reaction can be carried out by placing the inside of a reactor in an atmosphere of a raw material mixed gas in which an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms, ammonia, and molecular oxygen (oxygen gas) coexist, and raising the temperature to the temperature conditions specified for each step.

[0027] Examples of alkanes having 1 to 6 carbon atoms include methane, ethane, propane, butane, isobutane, pentane, isopentane, hexane, isohexane, and neohexane, with propane or isobutane being preferred. Examples of alkenes having 2 to 6 carbon atoms include ethylene, propylene, 1-butylene, 2-butylene, and isobutylene, with propylene or isobutylene being preferred.

[0028] The raw material mixed gas may contain other gases in addition to the C alkane or C alkene, ammonia, and molecular oxygen. The other gases may be, for example, an inert gas such as helium. The content of other gases (excluding water vapor when water vapor is contained) in the raw material mixed gas is preferably 95% by volume or less, more preferably 90% by volume or less, and even more preferably 85% by volume or less, relative to 100% by volume of the total volume of the gas (excluding water vapor when water vapor is contained).

[0029] The molar ratio of the alkane having 1 to 6 carbon atoms or the alkene having 2 to 6 carbon atoms to molecular oxygen in the raw material mixed gas (alkane or alkene / molecular oxygen) is preferably 0.1 or more and 6.0 or less, more preferably 0.3 or more and 5.0 or less, and even more preferably 0.5 or more and 5.0 or less. The molar ratio of the alkane having 1 to 6 carbon atoms or the alkene having 2 to 6 carbon atoms to ammonia in the raw material mixed gas (alkane or alkene / ammonia) is preferably 0.3 or more and 1.5 or less, more preferably 0.5 or more and 1.4 or less.

[0030] The reaction pressure of the gas phase catalytic oxidation reaction is preferably 300 kPa or less, more preferably 20 to 150 kPa.

[0031] The contact time of the composite oxide with the raw material mixed gas in the gas phase catalytic oxidation reaction is preferably 1 to 6.5 sec g / cm ３ , more preferably 1.5 to 5.5 sec g / cm ３ The contact time is defined by the following formula: Contact time (sec g / cm ３ ) = (W / F) × 273 / (273 + T) [wherein W = mass (g) of the composite oxide in the reactor, F = standard condition (0°C, 1.013 × 10 ５ raw material mixed gas flow rate (Ncm ３ / sec), T = temperature in reactor (°C)]

[0032] The amount of the antimony-containing compound calcined with the composite oxide in step (X) and the amount of the antimony-containing compound added in steps (A2) and (B1) are preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.1% by mass or more and 5% by mass or less, relative to 100% by mass of the total amount of the composite oxide. The antimony-containing compound may be added all at once or in multiple portions. There is no limit to the number of times the antimony-containing compound is added. The above-mentioned amount added is the final amount of the antimony-containing compound added.

[0033] The type of antimony-containing compound to be calcined with the composite oxide in step (X) and the type of antimony-containing compound to be added in steps (A2) and (B1) are not particularly limited as long as they are antimony-containing compounds having a melting point of 375°C or higher but lower than 450°C. However, antimony oxides having a melting point of 375°C or higher but lower than 450°C are preferred, such as diantimony pentoxide (Sb ２ O ５ ) can be used.

[0034] In step (X), the composite oxide, the antimony-containing compound, and the molybdenum-containing compound are preferably calcined in a reactor. In steps (A2) and (B1), the molybdenum-containing compound is preferably added to the reactor together with the antimony-containing compound. The molybdenum-containing compound and the antimony-containing compound may be added simultaneously, or the antimony-containing compound may be added after the molybdenum-containing compound, or the antimony-containing compound may be added after the antimony-containing compound.

[0035] The amount of the molybdenum-containing compound calcined with the composite oxide in step (X) and the amount of the molybdenum-containing compound added in steps (A2) and (B1) are preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to 100% by mass of the total amount of the composite oxide. Even when the antimony-containing compound is added in one batch, the molybdenum-containing compound may be added in multiple batches or all at once. Even when the antimony-containing compound is added in multiple batches, the molybdenum-containing compound may be added in one batch or all at once. There is no limit to the number of times the molybdenum-containing compound can be added. The above-mentioned amounts are the final amounts of the molybdenum-containing compound.

[0036] The type of the molybdenum-containing compound to be calcined with the composite oxide in step (X) and the type of the molybdenum-containing compound to be added in steps (A2) and (B1) are not particularly limited, but for example, ammonium molybdate (AHM) can be used.

[0037] The reactor used in steps (X), (A1), (A2), (B1), and (B2) is not particularly limited. However, when calcination is performed in a gas atmosphere containing water vapor while a gas-phase catalytic oxidation reaction is being carried out in steps (X), (A2), and (B2), from the viewpoint of uniformly dispersing the antimony compound (and the molybdenum-containing compound) in the catalyst, a reactor capable of constantly mixing and stirring the inside of the reactor, such as a fluidized bed reactor or a moving bed reactor, is preferred, and a fluidized bed reactor is more preferred.

[0038] The composite oxide used in steps (X), (A1), and (B1) preferably includes a composite oxide obtained by drying and calcining a raw material mixture containing at least a molybdenum-containing compound, a vanadium-containing compound, and an antimony-containing compound. Therefore, the method for producing a gas-phase catalytic oxidation catalyst of this embodiment may include, prior to steps (X), (A1), and (B1), a step (P) of drying and calcining a raw material mixture containing at least a molybdenum-containing compound, a vanadium-containing compound, and an antimony-containing compound to obtain a composite oxide. The raw material mixture may contain a support. Examples of molybdenum-containing compounds that can be used in step (P) include ammonium molybdate, vanadium-containing compounds include ammonium metavanadate, and antimony-containing compounds include diantimony trioxide. The raw material mixture may also contain other raw material compounds.

[0039] The gas-phase catalytic oxidation catalyst produced by the production method of this embodiment preferably contains a metal oxide. The metal oxide in the gas-phase catalytic oxidation catalyst is preferably supported on a carrier described below. The metal oxide in the gas-phase catalytic oxidation catalyst contains molybdenum (Mo), vanadium (V), and antimony (Sb) as metals, and may contain metals other than Mo, V, and Sb as necessary. Examples of metals other than Mo, V, and Sb include niobium (Nb), titanium (Ti), tungsten (W), manganese (Mn), bismuth (Bi), lanthanum (La), cerium (Ce), ytterbium (Yb), and yttrium (Y). In this embodiment, from the viewpoint of catalytic performance, the metal oxide in the gas-phase catalytic oxidation catalyst preferably satisfies the following composition formula (1): Mo １ V ａ Sb ｂ Nb ｃ T ｄ Z ｅ O ｎ .... (1) (In formula (1), T represents at least one element selected from the group consisting of Ti, W, Mn, and Bi, Z represents at least one element selected from the group consisting of La, Ce, Yb, and Y, a, b, c, d, and e represent atomic ratios of each element when Mo is defined as 1, and are in the ranges of 0.05≦a≦0.35, 0.05≦b≦0.35, 0≦c≦0.25, 0≦d≦0.20, and 0≦e≦0.10, respectively, and n is a value that satisfies the valence balance.)

[0040] The gas-phase catalytic oxidation catalyst produced by the production method of this embodiment preferably contains catalyst particles having a spherical shape. The spherical shape of the catalyst particles can be confirmed, for example, by the circularity of any cross-section of the catalyst particles. Circularity means a circularity of 0.95 or more. In this embodiment, the median diameter (average particle diameter) of the catalyst particles of the gas-phase catalytic oxidation catalyst is not particularly limited, but from the viewpoint of catalytic performance, it is preferably 20 μm to 150 μm, more preferably 30 μm to 100 μm, even more preferably 35 μm to 75 μm, and particularly preferably 45 μm to 65 μm. Here, the median diameter (average particle diameter) refers to the median diameter based on a volume-based particle size distribution and means the particle diameter corresponding to a cumulative frequency of 50% in the particle size distribution. The median diameter (average particle diameter) can be measured, for example, by a laser diffraction / scattering method based on Mie scattering theory.

[0041] The gas-phase catalytic oxidation catalyst produced by the production method of this embodiment preferably includes a carrier. The carrier preferably supports a metal oxide. The carrier is preferably a silica carrier. The silica carrier is not particularly limited as long as it contains silica, and examples of raw materials thereof include silica sol (also called colloidal silica) and powdered silica (dry silica). In this embodiment, from the viewpoint of the wear resistance and strength of the catalyst particles, the mass ratio of the silica carrier to the total amount (100 mass %) of the gas-phase catalytic oxidation catalyst is 100 mass % or less. ２ ) is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 60% by mass or less.

[0042] The gas-phase catalytic oxidation catalyst produced by the production method of this embodiment contains an antimony-containing compound on and / or within the catalyst particles. In the catalyst of this embodiment, the composite oxide and the antimony-containing compound are preferably in a state in which they cannot be non-destructively separated. The state in which they cannot be non-destructively separated means a state in which they cannot be separated without destroying the catalyst. Examples of a state in which they cannot be non-destructively separated include a state in which the composite oxide and the antimony-containing compound are integrated, a state in which the composite oxide and the antimony-containing compound are bonded, a state in which the antimony-containing compound is supported on the composite oxide, and a state in which the antimony-containing compound is incorporated into the composite oxide (e.g., in the pores of the composite oxide).

[0043] A complex oxide and an antimony-containing compound that cannot be non-destructively separated are clearly different from a complex oxide and an antimony-containing compound that are simply mixed together. A complex oxide and an antimony-containing compound that are simply mixed can be non-destructively separated, for example, by classification. The classification method is not particularly limited, but examples include classification using a sieve, an air classifier, a filter, or a combination thereof. When a sieve is used, for example, a sieve with a mesh size of 32 μm is used to remove particles smaller than 32 μm, thereby separating the simply mixed antimony-containing compound. Whether or not the antimony-containing compound has been separated can be determined by the change in the content of the antimony-containing compound in the catalyst before and after classification. It is desirable that the proportion of antimony-containing compound particles smaller than 32 μm that are removed by classification, as represented by the following formula (I), is 50% or less. When this proportion is 50% or less, the complex oxide and the antimony-containing compound cannot be non-destructively separated, and such a catalyst has superior thermal stability and catalytic activity compared to conventional catalysts. The amount of antimony oxide (mass % relative to the total amount of catalyst) in the following formula (I) is the total amount of antimony in the composite oxide and the added antimony-containing compound, and can be determined by XRF or the like. Proportion of antimony-containing compounds removed by classification = {(amount of antimony oxide before classification) - (amount of antimony oxide after classification)} / (amount of added antimony-containing compound) x 100 (I)

[0044] Here, the antimony-containing compounds supported in the catalyst particles can be observed using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX) (SU-70, manufactured by Hitachi High-Technologies Corporation). The catalyst is applied to a carbon tape, and after osmium coating, SEM-EDX measurement is performed at an accelerating voltage of 10 kV to quantify the antimony-containing compounds. In this embodiment, from the viewpoint of catalytic performance, the amount of antimony on the surface of the gas-phase catalytic oxidation reaction catalyst when measured with SEM-EDX (accelerating voltage 10 kV) is preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, and even more preferably 30% by mass or more and 40% by mass or less.

[0045] <<Method for Producing Unsaturated Nitrile>> By using the vapor-phase catalytic oxidation catalyst produced by the production method of this embodiment, unsaturated nitrile can be produced in high yield. The method for producing unsaturated nitrile using the vapor-phase catalytic oxidation catalyst is not particularly limited, and includes, for example, a step (N) of reacting an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms with ammonia and molecular oxygen in the vapor phase (vapor-phase catalytic oxidation reaction) to obtain an unsaturated nitrile. The vapor-phase catalytic oxidation reaction in the method for producing unsaturated nitrile can be carried out in a raw material mixed gas in the presence of the vapor-phase catalytic oxidation catalyst, in which an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms coexists with ammonia and molecular oxygen.

[0046] The raw material mixed gas may be the same as the raw material mixed gas used when carrying out the gas phase catalytic oxidation reaction in the above-described method for producing a gas phase catalytic oxidation reaction catalyst.

[0047] As the reaction system for the gas-phase catalytic oxidation reaction, known systems such as a fixed bed, fluidized bed, or moving bed can be used, but from the viewpoint of more uniformly supporting the added antimony-containing compound, it is desirable to use a fluidized bed reactor.

[0048] The reaction pressure of the gas phase catalytic oxidation reaction may be the same as the reaction pressure when the gas phase catalytic oxidation reaction is carried out in the above-described method for producing a gas phase catalytic oxidation reaction catalyst.

[0049] In the method for producing an unsaturated nitrile, the contact time of the catalyst for gas-phase catalytic oxidation reaction with the raw material mixed gas is preferably 1 to 6.5 sec g / cm ３ , more preferably 1.5 to 5.5 sec g / cm ３ The contact time is defined by the following formula: Contact time (sec g / cm ３ ) = (W / F) × 273 / (273 + T) [wherein W = mass (g) of the catalyst for gas-phase catalytic oxidation reaction, F = standard condition (0°C, 1.013 × 10 ５ raw material mixed gas flow rate (Ncm ３ / sec), T = reaction temperature (°C)]

[0050] The reaction temperature of the gas-phase catalytic oxidation reaction in the method for producing an unsaturated nitrile is preferably 300°C or higher and 500°C or lower, more preferably 350°C or higher and 500°C or lower, even more preferably 400°C or higher and 500°C or lower, still more preferably 420°C or higher and 500°C or lower, still more preferably 430°C or higher and 500°C or lower, and particularly preferably 440°C or higher and 500°C or lower.

[0051] <<Method for Producing Alkenes Having 2 to 6 Carbon atoms>> Using the vapor-phase catalytic oxidation catalyst produced by the production method of this embodiment, alkenes having 2 to 6 carbon atoms can be produced in high yield. The method for producing alkenes having 2 to 6 carbon atoms using the vapor-phase catalytic oxidation catalyst is not particularly limited, but for example, includes a step (O) of reacting an alkane having 2 to 6 carbon atoms with molecular oxygen in the vapor phase (vapor-phase catalytic oxidation reaction) to obtain an alkene having 2 to 6 carbon atoms. The vapor-phase catalytic oxidation reaction in the method for producing alkenes having 2 to 6 carbon atoms can be carried out in a raw material mixed gas in which an alkane having 2 to 6 carbon atoms and molecular oxygen coexist, in the presence of the vapor-phase catalytic oxidation catalyst. The method for producing alkenes having 2 to 6 carbon atoms is not particularly limited, but it is preferable to produce ethylene from ethane.

[0052] The raw material mixed gas may be a mixed gas obtained by removing ammonia from the raw material mixed gas used when carrying out the gas phase catalytic oxidation reaction in the above-described method for producing a gas phase catalytic oxidation reaction catalyst.

[0053] As the reaction system for the gas-phase catalytic oxidation reaction, known systems such as a fixed bed, fluidized bed, or moving bed can be used, but from the viewpoint of more uniformly supporting the added antimony-containing compound, it is desirable to use a fluidized bed reactor.

[0054] The reaction pressure of the gas phase catalytic oxidation reaction may be the same as the reaction pressure when the gas phase catalytic oxidation reaction is carried out in the above-described method for producing a gas phase catalytic oxidation reaction catalyst.

[0055] In the method for producing alkenes having 2 to 6 carbon atoms, the contact time of the catalyst for gas-phase catalytic oxidation reaction with the raw material mixed gas is preferably 1 to 6.5 sec g / cm ３ , more preferably 1.5 to 5.5 sec g / cm３ The contact time is defined by the following formula: Contact time (sec g / cm ３ ) = (W / F) × 273 / (273 + T) [wherein W = mass (g) of the catalyst for gas-phase catalytic oxidation reaction, F = standard condition (0°C, 1.013 × 10 ５ raw material mixed gas flow rate (Ncm ３ / sec), T = reaction temperature (°C)]

[0056] The reaction temperature of the gas-phase catalytic oxidation reaction in the method for producing alkenes having 2 to 6 carbon atoms is preferably 300°C or higher and 500°C or lower, more preferably 350°C or higher and 500°C or lower, even more preferably 400°C or higher and 500°C or lower, still more preferably 420°C or higher and 500°C or lower, still more preferably 430°C or higher and 500°C or lower, and particularly preferably 440°C or higher and 500°C or lower.

[0057] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, the temperature conditions are room temperature (25°C), and unless otherwise specified, the pressure conditions are atmospheric pressure (1 atm).

[0058] Reference Example 1: Composite oxide (reference catalyst) (Step 1: Preparation of niobium raw material solution) A niobium raw material solution was prepared by the following method. 77.8 kg of water was added to a mixing vessel, and then the water was heated to 45°C. Next, oxalic acid dihydrate [H ２ C ２ O ４ ・2H ２ O] 72.2 kg, followed by niobium pentoxide [Nb ２ O ５20.0 kg of niobic acid containing 76.0 mass % of niobium as a raw material was added, and the two were mixed in water. This solution was heated and stirred at 70°C for 8 hours, and the resulting aqueous mixture was left to stand, ice-cooled, and the solid was filtered off by suction filtration to obtain a uniform niobium raw material solution. The molar ratio of oxalic acid / niobium in this niobium raw material solution was found to be 2.11 by the following analysis. The molar ratio of oxalic acid / niobium in the niobium raw material solution was calculated as follows. 10 g of the niobium raw material solution was precisely weighed into a crucible, dried at 120°C for 2 hours, and then heat-treated at 600°C for 2 hours to obtain a solid Nb ２ O ５ The Nb concentration of the niobium raw material solution was calculated from the weight of the solution, and was found to be 0.889 mol / kg. Furthermore, 3 g of the niobium raw material solution was precisely weighed into a 300 mL glass beaker, and 20 mL of hot water at about 80°C was added, followed by 10 mL of 1:1 sulfuric acid (concentrated sulfuric acid and water in a 1:1 ratio). The resulting mixture was stirred in a water bath at a temperature of 70°C, and then added with 1 / 4 N potassium permanganate [KMnO ４ ] was titrated with KMnO ４ The end point was the point at which a faint pink color due to 2KMnO persisted for about 30 seconds or more. The oxalic acid concentration was calculated from the titer using the following formula, and was found to be 1.88 mol / kg. ４ +3H ２ SO ４ +5H ２ C ２ O ４ →K ２ SO ４ + 2MnSO ４ +10CO ２ +8H ２ The turbidity was measured after leaving the solution to stand for one day after preparation using a 2100AN Turbidimeter manufactured by HACH Co. 30 mL of the niobium raw material solution was placed in a measurement cell and measured according to US EPA method 180.1. The turbidity was found to be 52 NTU.

[0059] (Step 2: Preparation of composite oxide (reference catalyst)) １ V ０．２３ Sb ０．２３ Nb ０．０８ W ０．０３ O ｎ / 49.0% by mass-SiO ２ A composite oxide (reference catalyst) (silica-supported catalyst) represented by the formula: was produced as follows.

[0060] 111 kg of water was added to ammonium molybdate [(NH ４ ) ６ Mo ７ O ２４ ・4H ２ 16.7 kg of ammonium metavanadate [NH ４ VO ３ ], 2.5 kg of diantimony trioxide [Sb ２ O ３ 3.2 kg of ] was added thereto, and the mixture was heated at 90°C for 2 hours and 30 minutes with stirring to obtain a mixed solution A.

[0061] 8.5 kg of the niobium raw material liquid obtained in step 1 was added to hydrogen peroxide [H ２ O ２ 1.7 kg of hydrogen peroxide solution containing 35.3 mass % of silicon dioxide [SiO ２ 34.5 kg of silica sol containing 34.1% by mass of HCl was added. ２ O ２ 4.6 kg of aqueous hydrogen peroxide containing 35.3% by mass of ammonium metatungstate was added, and stirring was continued for 1 hour at 50° C. Next, mixed solution B was added. Subsequently, 1.3 kg of an aqueous ammonium metatungstate solution (purity 49.9%) and a solution prepared by dispersing 7.8 kg of fumed silica in 78.4 kg of water were added, and a slurry-like aqueous mixed solution A was obtained.

[0062] The resulting slurry-like aqueous mixture A was supplied to a centrifugal spray dryer and dried to obtain microspherical dried particles. The inlet temperature of the dryer was 210° C., and the outlet temperature was 120° C. In order to continuously perform the firing step described below, the dry particle preparation step was repeated.

[0063] Calcination was carried out using a continuous SUS kiln with a diameter of 127 mm and a length of 1150 mm. The resulting dry powder was fed at 220 g / Hr and pre-calcined at 360°C for 2 hours under a countercurrent nitrogen flow of 3.6 NL / min to obtain a pre-calcined product. The pre-calcined product was then fed at 130 g / Hr and post-calcined at a TOP temperature of 660°C for 2 hours under a countercurrent nitrogen flow of 2.3 NL / min to obtain calcined particles as a composite oxide (reference catalyst). Projections consisting of protruding composite oxide crystals were present on the surface of these calcined particles.

[0064] While air was being passed through a vertical tube (inner diameter 41.6 mm, length 70 cm) equipped with a perforated disk with three 1 / 64 inch diameter holes at the bottom and a paper filter at the top, 50 g of the composite oxide (reference catalyst) was poured into the tube. The length of the airflow in the airflow direction was 52 mm, and the average linear velocity of the airflow was 310 m / s. When the composite oxide (reference catalyst) obtained after 24 hours was examined by SEM, no protrusions were found on the catalyst surface.

[0065] (Catalyst Performance Test 1: Propane Ammoxidation Reaction Test) A propane ammoxidation reaction test was carried out by filling a fixed-bed reactor (diameter 10 mm) with 2.0 g of a gas-phase catalytic oxidation reaction catalyst and introducing a mixed gas (propane 6.4 vol%, ammonia 7.7 vol%, oxygen 17.9 vol%, helium 68.0 vol%) at a predetermined temperature (445°C) and a predetermined pressure (0.06 kg / G) with a flow rate adjusted so that the propane conversion was 89 to 90%. The yield of acrylonitrile 2 hours after the start of the ammoxidation reaction test was determined as follows by analyzing the reaction product gas by gas chromatography. The number of moles of acrylonitrile produced was determined by analyzing acrylonitrile gas with a known concentration in advance using gas chromatography (Shimadzu Corporation "GC2014") to prepare a calibration curve, and then quantitatively injecting the gas produced by the gas-phase catalytic oxidation reaction into the GC and measuring it. The yield of acrylonitrile was calculated from the measured number of moles of acrylonitrile according to the following formula: Yield of acrylonitrile (AN yield) (%) = (number of moles of acrylonitrile produced) / (number of moles of propane supplied) × 100 The yield of acrylonitrile two hours after the start of the ammoxidation reaction test using the composite oxide of Reference Example 1 (reference catalyst) was 54.8%.

[0066] (Catalyst Performance Test 2: Ethane Oxidation Reaction Test) The ethane oxidation reaction test was carried out by filling a fixed-bed reactor (diameter 10 mm) with 2.0 g of a gas-phase catalytic oxidation reaction catalyst and introducing a mixed gas (ethane 20.0 vol %, oxygen 20.0 vol %, helium 60.0 vol %) at a predetermined temperature (445°C) and a predetermined pressure (0.06 kg / G) with a flow rate adjusted so that the ethane conversion was 85-86%. The ethylene yield 2 hours after the start of the ethane oxidation reaction test was determined by analyzing the reaction product gas by gas chromatography as follows. The number of moles of ethylene produced was determined by analyzing ethylene gas with a known concentration in advance using gas chromatography (Shimadzu Corporation's "GC2014") to prepare a calibration curve, and then quantitatively injecting the gas produced by the oxidation reaction into the GC and measuring it. The ethylene yield was calculated from the measured number of moles of ethylene according to the following formula: Ethylene yield (%)=(number of moles of ethylene produced) / (number of moles of ethane supplied)×100 Two hours after the start of the ethane oxidation reaction test using the composite oxide of Reference Example 1 (reference catalyst), the ethylene yield was 69.5%.

[0067] Comparative Example 1: Comparative Catalyst A A gas-phase catalytic oxidation reaction for producing acrylonitrile from propane was carried out in the presence of the composite oxide (reference catalyst) obtained in Reference Example 1. A Vycor glass fluidized-bed reactor tube having an inner diameter of 25 mm was packed with 40 g of the composite oxide (reference catalyst) obtained in Reference Example 1, and the catalyst was then passed through a Vycor glass fluidized-bed reactor tube having an inner diameter of 25 mm, at a reaction temperature of 445°C and a reaction pressure of 60 kPa, with a mixed gas having a molar ratio of propane:ammonia:oxygen:helium=1.0:1.1:2.9:11.6, in accordance with the following definitions, for a contact time of 3.0 (sec g / cm ３ ) was supplied. This reaction was continued for 180 days to obtain Comparative Catalyst A. The contact time is defined by the following formula: ３ ) = (W / F) × 273 / (273 + T) [wherein W = amount of catalyst loaded (g), F = standard condition (0°C, 1.013 × 10 ５ raw material mixed gas flow rate (Ncm ３ / sec), T = reaction temperature (°C)] Comparative catalyst A was subjected to catalytic performance test 1 similar to Reference Example 1, and the yield of acrylonitrile 2 hours after the start of the ammoxidation reaction test was determined to be 53.9%. Furthermore, the ammoxidation reaction test of catalytic performance test 1 was continued for 30 days, and the yield of acrylonitrile after 30 days was determined in the same manner as the yield of acrylonitrile 2 hours after the start of the ammoxidation reaction test. The yield of acrylonitrile 30 days after the start of the ammoxidation reaction test was 53.9%. Furthermore, the difference in the yield after 30 days from the start of the test to the yield after 2 hours was determined, and thermal stability was evaluated based on the "Evaluation Criteria for Thermal Stability" below. As a result, comparative catalyst A was evaluated as having "good thermal stability" under ammoxidation reaction. Comparative catalyst A was subjected to catalytic performance test 2 similar to Reference Example 1, and the yield of ethylene 2 hours after the start of the ethane oxidation reaction test was 68.0%. Furthermore, the ethane oxidation reaction test of Catalyst Performance Test 2 was continued for 30 days as is, and the ethylene yield after 30 days was determined in the same manner as the ethylene yield after 2 hours from the start of the ethane oxidation reaction test. The ethylene yield after 30 days from the start of the ethane oxidation reaction test was 68.0%. Furthermore, the difference in yield after 30 days from the start of the test relative to the yield after 2 hours from the start of the test was determined, and thermal stability was evaluated based on the "Evaluation Criteria for Thermal Stability" below. As a result, Comparative Catalyst A was evaluated as having "good thermal stability" under the ethane oxidation reaction. <Evaluation Criteria for Thermal Stability> Yield difference of -0.1% or more: "good thermal stability" Yield difference of -0.2% or less: "poor thermal stability"

[0068] (Measurement of average particle size) The average particle size was calculated as the median size based on the volume-based particle size distribution using an MT3000II (laser diffraction particle size distribution analyzer) manufactured by Microtrac Bell Co., Ltd. The average particle size of comparative catalyst A was 56 μm.

[0069] (SEM-EDX Measurement) The amount of antimony on the catalyst surface can be observed by SEM-EDX (SU-70, manufactured by Hitachi High-Technologies Corporation). As a preparation for the measurement, coarse particles of 100 μm or more and fine particles of 32 μm or less were removed from the catalyst using a sieve. The catalyst was applied to carbon tape, and after osmium coating, SEM-EDX measurement was performed at an accelerating voltage of 10 kV to quantify the antimony-containing compounds. The amount of antimony on the catalyst surface of comparative catalyst A was 25 mass %. The measurement conditions for the SEM-EDX measurement were as follows: Acceleration voltage: 10 kV Measurement magnification: 300x Accumulation time: 300 s Measurement electrons: Mo_L, V_K, Sb_L, Nb_L, W_M, Si_K

[0070] Comparative Example 2: Comparative Catalyst B 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed reactor tube having an inner diameter of 25 mm, and the same mixed gas as in Comparative Example 1 was pumped at a reaction temperature of 445° C., a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３ ) was supplied to the reaction tube via a hopper. After confirming that the reaction state was stable, a powdered molybdenum-containing compound (ammonium molybdate) was mixed with Comparative Catalyst A at a concentration of 1 mass % relative to the weight of Comparative Catalyst A while continuing the reaction process, and the mixture was added to the reaction tube via a hopper. After confirming that the reaction state was stable after the addition, the reaction was stopped, and Comparative Catalyst B was obtained. "Reaction stopped" refers to a state in which the reactants were not supplied to the reaction tube and the temperature was lowered while the reaction tube was filled with an inert gas. Comparative Catalyst B was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the acrylonitrile yield was determined 2 hours after the start of the ammoxidation reaction test in the same manner as Reference Example 1, and was found to be 54.1%. Comparative Catalyst B was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the ethylene yield was determined 2 hours after the start of the ethane oxidation reaction test in the same manner as Reference Example 1, and was found to be 68.2%. The average particle size of Comparative Catalyst B was measured in the same manner as Comparative Example 1, and was found to be 56 μm. When comparative catalyst B was subjected to SEM-EDX measurement in the same manner as in Comparative Example 1, the amount of antimony on the catalyst surface of comparative catalyst B was found to be 26 mass %.

[0071] [Example 1: Catalyst A] 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed type reaction tube having an inner diameter of 25 mm, and the same mixed gas as in Comparative Example 1 was poured into the reaction tube at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３ ) was supplied. After confirming that the reaction state was stable, a powdered antimony-containing compound (diantimony pentoxide) and a powdered molybdenum-containing compound (ammonium molybdate) were mixed at 0.5% by mass and 1% by mass, respectively, relative to the weight of Comparative Catalyst A, while continuing the reaction process, and the mixture was added to the reaction tube through a hopper. After confirming that the reaction state was stable after the addition, the reaction was stopped, and Catalyst A was obtained. "Reaction stopped" refers to a state in which the reactants were not supplied to the reaction tube and the temperature was lowered while the reaction tube was filled with an inert gas. Catalyst A was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the yield of acrylonitrile 2 hours after the start of the ammoxidation reaction test was determined as in Reference Example 1 and was 54.4%. The yield of acrylonitrile 30 days after the start of the ammoxidation reaction test was also determined as in Comparative Example 1 and was 54.4%. Thermal stability was evaluated in the same manner as in Comparative Example 1, and Catalyst A was evaluated as having "good thermal stability" during the ammoxidation reaction. For catalyst A, catalytic performance test 2 similar to Reference Example 1 was carried out, and the ethylene yield was determined 2 hours after the start of the ethane oxidation reaction test in the same manner as Reference Example 1, and was 68.3%. The ethylene yield was determined 30 days after the start of the ethane oxidation reaction test in the same manner as Comparative Example 1, and was 68.3%. As a result of evaluating thermal stability in the same manner as Comparative Example 1, catalyst A was evaluated as having "good thermal stability" under the ethane oxidation reaction. For catalyst A, the average particle size was measured in the same manner as Comparative Example 1, and the average particle size of catalyst A was 56 μm. For catalyst A, SEM-EDX measurement similar to Comparative Example 1 was carried out, and the amount of antimony on the catalyst surface of catalyst A was 31 mass%.

[0072] (Evaluation of the State of Sb-Containing Compounds) The composite oxide catalyst was evaluated for a state in which the added antimony-containing compound could not be non-destructively separated from the catalyst. Fine particles of 32 μm or less were removed from the catalyst using a sieve, and the proportion of the antimony-containing compound removed by classification was calculated using the following formula (I): The amount of Sb oxide (mass % relative to the total amount of catalyst) was determined by the fundamental parameter (FP) method using fluorescent X-ray analysis (Rigaku Corporation, trade name "ZSX Primus III"). {(Amount of Sb oxide before classification) - (Amount of Sb oxide after classification)} / (Amount of added antimony-containing compound) × 100 [%] (I) The proportion of the antimony-containing compound removed by classification was 34%.

[0073] [Example 2: Catalyst B] 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed reactor tube having an inner diameter of 25 mm, and the same mixed gas as in Comparative Example 1 was poured into the reactor at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３ ) was supplied to Comparative Catalyst A. After confirming that the reaction state was stable, a powdered antimony-containing compound (diantimony pentoxide) and a powdered molybdenum-containing compound (ammonium molybdate) were mixed together so that the amounts were 1% by mass and 2% by mass, respectively, relative to the weight of Comparative Catalyst A, while continuing the reaction process, and the mixture was added to the reaction tube through a hopper. After confirming that the reaction state was stable after the addition, the reaction was stopped, and Catalyst B was obtained. Catalyst B was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the acrylonitrile yield was determined to be 54.6% two hours after the start of the ammoxidation reaction test. Catalyst B was subjected to Catalytic Performance Test 2 similar to Reference Example 1, and the ethylene yield was determined to be 68.6% two hours after the start of the ethane oxidation reaction test. The average particle size of Catalyst B was measured in the same manner as Comparative Example 1, and the average particle size of Catalyst B was 55 μm. Catalyst B was subjected to SEM-EDX measurement in the same manner as Comparative Example 1, and the amount of antimony on the catalyst surface of Catalyst B was 33% by mass. When the state of the Sb-containing compounds in catalyst B was evaluated in the same manner as in Example 1, the proportion of antimony-containing compounds removed by classification was 28%.

[0074] [Example 3: Catalyst C] 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed reactor tube having an inner diameter of 25 mm, and the same mixed gas as in Comparative Example 1 was pumped at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３ ) was supplied to Comparative Catalyst A. After confirming that the reaction state was stable, a powdered antimony-containing compound (diantimony pentoxide) and a powdered molybdenum-containing compound (ammonium molybdate) were mixed together so that the amounts were 0.5% by mass and 1% by mass, respectively, relative to the weight of Comparative Catalyst A, while continuing the reaction process, and the mixture was added to the reaction tube through a hopper. After confirming that the reaction state was stable after the addition, the mixture was reacted for 7 days, and then a powdered antimony-containing compound (diantimony pentoxide) and a powdered molybdenum-containing compound (ammonium molybdate) were mixed together so that the amounts were 0.5% by mass and 1% by mass, respectively, relative to the weight of Comparative Catalyst A, and the mixture was added again to the reaction tube through the hopper. After confirming that the reaction state was stable after the addition, the reaction was stopped, and Catalyst C was obtained. Catalyst C was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the yield of acrylonitrile 2 hours after the start of the ammoxidation reaction test was determined to be 54.8%. For catalyst C, catalytic performance test 2 was carried out in the same manner as in Reference Example 1, and the ethylene yield was determined to be 68.8% two hours after the start of the ethane oxidation reaction test. For catalyst C, the average particle size was measured in the same manner as in Comparative Example 1, and the average particle size of catalyst C was found to be 56 μm. For catalyst C, SEM-EDX measurement was carried out in the same manner as in Comparative Example 1, and the amount of antimony on the catalyst surface of catalyst C was found to be 34 mass%.

[0075] [Example 4: Catalyst D] 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed reactor tube having an inner diameter of 25 mm, and the catalyst was heated at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a mixed gas of helium and steam in a volume ratio of 80:20 was added for a contact time of 3.0 (sec g / cm) in accordance with the above definition. ３) was supplied to the reaction tube. After confirming that the temperature state was stable, a powdered antimony-containing compound (diantimony pentoxide) and a powdered molybdenum-containing compound (ammonium molybdate) were mixed so that the amounts were 0.5% by mass and 1% by mass, respectively, relative to the weight of Comparative Catalyst A, while continuing the reaction treatment, and the mixture was added to the reaction tube through a hopper. After confirming that the reaction state was stable after the addition, heating was stopped, and Catalyst D was obtained. Catalyst D was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the acrylonitrile yield was determined to be 54.5% two hours after the start of the ammoxidation reaction test. Catalyst D was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the ethylene yield was determined to be 68.6% two hours after the start of the ethane oxidation reaction test. The average particle size of Catalyst D was measured in the same manner as in Comparative Example 1, and the average particle size of Catalyst D was 55 μm. Catalyst D was subjected to SEM-EDX measurement in the same manner as in Comparative Example 1, and the amount of antimony on the catalyst surface of Catalyst D was 32% by mass.

[0076] [Example 5: Catalyst E] 40 g of the comparative catalyst A obtained in Comparative Example 1 was packed into a Vycor glass fluidized bed reactor tube having an inner diameter of 25 mm, and the same mixed gas as in Comparative Example 1 was pumped at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３) was supplied to the reaction tube via a hopper. After confirming that the reaction state was stable, a powdered antimony-containing compound (diantimony pentoxide) was weighed out to 0.5% by mass relative to the weight of Comparative Catalyst A, and added to the reaction tube via a hopper while continuing the reaction process. After confirming that the reaction state was stable after the addition, the reaction was stopped, and Catalyst E was obtained. Catalyst E was subjected to Catalytic Performance Test 1 similar to Reference Example 1, and the acrylonitrile yield was determined to be 54.3% two hours after the start of the ammoxidation reaction test. Catalyst E was subjected to Catalytic Performance Test 2 similar to Reference Example 1, and the ethylene yield was determined to be 68.3% two hours after the start of the ethane oxidation reaction test. The average particle size of Catalyst E was measured in the same manner as in Comparative Example 1, and the average particle size of Catalyst E was 55 μm. Catalyst E was subjected to SEM-EDX measurement in the same manner as in Comparative Example 1, and the amount of antimony on the catalyst surface of Catalyst E was 31% by mass.

[0077] [Example 6: Catalyst F] 40 g of the comparative catalyst A obtained in Comparative Example 1, 0.2 g (0.5 mass % relative to the weight of the comparative catalyst A) of a powdered antimony-containing compound (diantimony pentoxide), and 0.4 g (1 mass % relative to the weight of the comparative catalyst A) of a powdered molybdenum-containing compound (ammonium molybdate) were mixed and then packed into a Vycor glass fluidized-bed reactor tube having an inner diameter of 25 mm. The mixture was then subjected to a reaction at a temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ). ３) was supplied at a temperature of 100°C. After confirming that the reaction state was stable after the addition, the reaction was stopped to obtain catalyst F. Catalyst F was subjected to catalytic performance tests 1 and 2 similar to those in Reference Example 1. The acrylonitrile yield was determined 2 hours after the start of the ammoxidation reaction test to be 54.5%. The acrylonitrile yield was also determined 30 days after the start of the ammoxidation reaction test to be 54.5%. Thermal stability was evaluated in the same manner as in Comparative Example 1, and catalyst F was evaluated as having "good thermal stability" in the ammoxidation reaction. Catalyst F was subjected to catalytic performance tests 1 and 2 similar to those in Reference Example 1. The ethylene yield was determined 2 hours after the start of the ethane oxidation reaction test to be 68.6%. The ethylene yield was also determined 30 days after the start of the ethane oxidation reaction test to be 68.6%. Thermal stability was evaluated in the same manner as in Comparative Example 1, and catalyst F was evaluated as having "good thermal stability" in the ethane oxidation reaction. The average particle diameter of catalyst F was measured in the same manner as in Comparative Example 1, and was found to be 55 μm. SEM-EDX measurement was performed on catalyst F in the same manner as in Comparative Example 1, and the amount of antimony on the catalyst surface of catalyst F was found to be 32 mass%.

[0078] [Comparative Example 3: Catalyst G] 40 g of the comparative catalyst A obtained in Comparative Example 1, 0.4 g (1.0 mass % relative to the weight of comparative catalyst A) of a powdered antimony-containing compound (antimony tetroxide), and 0.8 g (2 mass % relative to the weight of comparative catalyst A) of a powdered molybdenum-containing compound (ammonium molybdate) were mixed and then packed into a Vycor glass fluidized-bed reactor tube having an inner diameter of 25 mm. The same mixed gas as in Comparative Example 1 was then pumped at a reaction temperature of 445°C, a reaction pressure of 60 kPa, and a contact time of 3.0 (sec g / cm ３) was supplied at a temperature of 1000°C. After confirming that the reaction state was stable after the addition, the reaction was stopped to obtain catalyst G. Catalyst G was subjected to catalytic performance test 1 similar to that of Reference Example 1, and the acrylonitrile yield was 54.1% two hours after the start of the ammoxidation reaction test. Similarly to Comparative Example 1, the acrylonitrile yield was 53.9% 30 days after the start of the ammoxidation reaction test. Similarly to Comparative Example 1, the thermal stability was evaluated, and catalyst G was evaluated as having "poor thermal stability" in the ammoxidation reaction. Similarly to Reference Example 1, catalyst G was subjected to catalytic performance test 2 similar to that of Reference Example 1, and the ethylene yield was 68.3% two hours after the start of the ethane oxidation reaction test. Similarly to Comparative Example 1, the ethylene yield was 68.0% 30 days after the start of the ethane oxidation reaction test. Similarly to Comparative Example 1, the thermal stability was evaluated, and catalyst G was evaluated as having "poor thermal stability" in the ethane oxidation reaction. The average particle diameter of catalyst G was measured in the same manner as in Comparative Example 1, and was found to be 55 μm. Catalyst G was subjected to SEM-EDX measurement in the same manner as in Comparative Example 1, and the amount of antimony on the catalyst surface of catalyst G was found to be 28 mass %. The state of Sb-containing compounds in catalyst G was evaluated in the same manner as in Example 1, and the proportion of antimony-containing compounds removed by classification was found to be 68%.

[0079] <Results of Examples> The acrylonitrile yield (2 hours and 30 days after the start of the test) and the evaluation results of its thermal stability in Catalyst Performance Test 1, the ethylene yield (2 hours and 30 days after the start of the test) and the evaluation results of its thermal stability in Catalyst Performance Test 2, the amount of antimony on the catalyst surface, and the average particle size are summarized in Table 1 below for Examples 1 to 6 and Comparative Examples 1 and 2.

[0080]

[0081] ａ） Divide the amount indicated in half and add the other half seven days after the first addition. ｂ） Sb under a helium / water vapor mixed gas flow ２ O ５ and AHM was added. ｃ） Before the reaction treatment, Sb ２O ５ and AHM was added.

[0082] As is clear from Table 1, the antimony-containing compounds (Sb ２ O ５ The catalysts of Examples 1 to 6 obtained by adding an antimony-containing compound (Sb) and optionally a molybdenum-containing compound and calcining them in the presence of water vapor were all compared to those before calcination (Comparative Example 1), when only a molybdenum-containing compound was added (Comparative Example 2), and when an antimony-containing compound (Sb) having a melting point of 450°C or higher was added. ２ O ４ In addition, acrylonitrile and ethylene were synthesized in a higher yield than in the case where an antimony-containing compound (Sb ２ O ５ The catalysts (Examples 1 to 6) containing an antimony-containing compound (Sb) having a melting point of 450°C or higher were used instead. ２ O ４ ) was added (Comparative Example 3), the thermal stability of which was superior.

[0083] This application claims priority to Japanese Patent Application No. 2024-105021 filed on June 28, 2024 and Japanese Patent Application No. 2025-003109 filed on January 8, 2025, the entire contents of which are considered to be part of the disclosure of this application and are incorporated herein by reference.

Claims

A method for producing a gas-phase catalytic oxidation reaction catalyst, comprising: a step (X) of calcining a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher but lower than 450°C in a reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor, thereby obtaining a gas-phase catalytic oxidation reaction catalyst.

2. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 1, wherein in the step (X), the composite oxide, the antimony-containing compound, and the molybdenum-containing compound are calcined in the reactor. a step (A1) of adding a composite oxide containing at least Mo, V, and Sb to a reactor, and maintaining the inside of the reactor at a temperature of 300°C or higher and in a gas atmosphere containing water vapor; a step (A2) of adding an antimony-containing compound having a melting point of 375°C or higher but lower than 450°C to the reactor, and calcining the compound in the reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor, thereby obtaining a gas-phase catalytic oxidation reaction catalyst; or a step (B1) of adding a composite oxide containing at least Mo, V, and Sb and an antimony-containing compound having a melting point of 375°C or higher and lower than 450°C to a reactor, and maintaining the inside of the reactor at a temperature of 300°C or higher and in a gas atmosphere containing water vapor; and (B2) a step of calcining the catalyst in the reactor at a temperature of 400°C or higher in a gas atmosphere containing water vapor to obtain a gas-phase catalytic oxidation reaction catalyst. A method for producing the vapor phase catalytic oxidation catalyst according to claim 1.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 3, wherein in the step (A2), the antimony-containing compound is added to the reactor under a temperature condition of not less than the melting point of the antimony-containing compound and in a gas atmosphere containing water vapor.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 3, wherein in the steps (A2) and (B1), the antimony-containing compound is added to the reactor at a temperature below a melting point of the antimony-containing compound, and in the steps (A2) and (B1) or (B2), the temperature inside the reactor is raised to a temperature equal to or higher than the melting point of the antimony-containing compound in a gas atmosphere containing water vapor.

4. The method for producing a catalyst for a gas-phase catalytic oxidation reaction according to claim 3, wherein in steps (A2) and (B1), a molybdenum-containing compound is added to the reactor together with the antimony-containing compound.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 3, wherein in the steps (A1) and (B1), an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms is reacted with ammonia and molecular oxygen in a gas phase at 300°C or higher to generate water vapor, and the reaction vessel is placed under a gas atmosphere containing water vapor.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 3, wherein in the steps (A2) and (B2), the alkane having 1 to 6 carbon atoms or the alkene having 2 to 6 carbon atoms is reacted with ammonia and molecular oxygen in the gas phase in the reactor while being calcined in a gas atmosphere containing water vapor.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 1, wherein the composite oxide comprises a composite oxide obtained by drying and calcining a raw material mixed liquid containing at least a molybdenum-containing compound, a vanadium-containing compound, and an antimony-containing compound.

4. The method for producing a catalyst for a gas-phase catalytic oxidation reaction according to claim 1, wherein the concentration of water vapor contained in the gas atmosphere is 5% by volume or more.

4. The method for producing a gas-phase catalytic oxidation catalyst according to claim 1, wherein the average particle size of the gas-phase catalytic oxidation catalyst is 35 μm or more and 75 μm or less. 　 The gas-phase catalytic oxidation reaction catalyst contains a metal oxide, and the metal oxide is represented by the following formula (1): Mo １ V ａ Sb ｂ Nb ｃ T ｄ Z ｅ O ｎ ・・・(1) (In formula (1), T represents at least one element selected from the group consisting of Ti, W, Mn, and Bi; Z represents at least one element selected from the group consisting of La, Ce, Yb, and Y; a, b, c, d, and e represent atomic ratios of each element when Mo is defined as 1, and are in the ranges of 0.05≦a≦0.35, 0.05≦b≦0.35, 0≦c≦0.25, 0≦d≦0.20, and 0≦e≦0.10, respectively; and n is a value that satisfies the valence balance.) The method for producing the catalyst for gas-phase catalytic oxidation reaction according to claim 1 or 3, wherein the catalyst is represented by the formula: 　 The method for producing a gas-phase catalytic oxidation catalyst according to claim 1 or 3, wherein the gas-phase catalytic oxidation catalyst comprises a support.

14. The method for producing a vapor phase catalytic oxidation catalyst according to claim 13, wherein the support comprises a silica support.

4. The method for producing a catalyst for a gas-phase catalytic oxidation reaction according to claim 1, wherein the reactor is a fluidized bed reactor.

4. The method for producing a gas-phase catalytic oxidation reaction catalyst according to claim 1, wherein the amount of antimony on the surface of the gas-phase catalytic oxidation reaction catalyst is 10 mass % or more and 50 mass % or less when the gas-phase catalytic oxidation reaction catalyst is measured using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX) (accelerating voltage 10 kV). 　 A method for producing an unsaturated nitrile, comprising: a step (N) of reacting an alkane having 1 to 6 carbon atoms or an alkene having 2 to 6 carbon atoms with ammonia and molecular oxygen in the presence of a gas-phase catalytic oxidation catalyst produced by the production method according to claim 1 or 3, to obtain an unsaturated nitrile. 　 A method for producing an alkene having 2 to 6 carbon atoms, comprising: a step (O) of reacting an alkane having 2 to 6 carbon atoms with molecular oxygen in the gas phase in the presence of the gas-phase catalytic oxidation catalyst produced by the production method according to claim 1 or 3, to obtain an alkene having 2 to 6 carbon atoms.

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