Catalyst, method for producing the same, and method for producing unsaturated nitrile or alkene

Abstract

Provided is a catalyst for a gas-phase catalytic oxidation reaction, containing: a metal oxide containing at least Mo, V and Sb; and Sb2O4.

Description

Catalyst and method for producing same, and method for producing unsaturated nitrile or alkene

[0001] The present invention relates to a catalyst and a method for producing the catalyst, and a method for producing an unsaturated nitrile or alkene.

[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 the use of a composite oxide as a catalyst for producing an unsaturated nitrile, the composite oxide comprising particles having a metal oxide containing molybdenum (Mo), vanadium (V), and antimony (Sb) and a silica support, in which the Sb is dispersed within the particles and the degree of dispersion of the Sb is 0.80 to 1.3.

[0004] Patent Document 2 proposes the use of an oxide catalyst as a catalyst for producing an unsaturated nitrile, the oxide catalyst comprising particles having a metal oxide containing molybdenum (Mo), vanadium (V), and antimony (Sb) and a silica support, in which the proportion of pentavalent Sb in the surface layer of the Sb particles is less than 70 atomic % and the average particle size of the Sb particles is 1.2 μm or less.

[0005] Patent No. 6310751 Patent No. 6717948

[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, the yield of unsaturated nitrile can be improved by improving the dispersion of Sb, which is a catalyst constituent element, and according to Patent Document 2, the yield of unsaturated nitrile can be improved by controlling the valence and average particle size of the surface layer of Sb particles, but neither document clarifies the form of Sb in the catalyst. In other words, although it can be said that control of the form of Sb is important, no prior art has reported on the form of Sb effective for producing unsaturated nitriles or the amount of Sb in the effective form.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a catalyst capable of producing an unsaturated nitrile or alkene with high efficiency by controlling the form of Sb in the catalyst, and a method for producing the same.

[0009] As a result of investigations to solve the above problems, the present inventors have found that, in addition to a metal oxide containing at least Mo, V and Sb, Sb ２ O ４ The present invention was completed based on the discovery that a catalyst containing

[0010] That is, the present invention is as follows: [1] A metal oxide containing at least Mo, V, and Sb, and Sb ２ O ４ [2] A catalyst for a gas-phase catalytic oxidation reaction, comprising: [1] a catalyst according to [1], wherein the gas-phase catalytic oxidation reaction is an ammoxidation reaction or an alkane oxidation reaction; [3] The catalyst has at least two types of Sb—O—Sb bonds and at least one type of Sb—O—Mo bond; and ２ O ４ Represented by quantitative parameters, Sb ２ O ４ [4] The catalyst according to [1] or [2], wherein the amount of Sb present as a metal oxide is 0.1 mass % or more and 50 mass % or less based on the amount of Sb in the catalyst. ２ O ４ [5] The catalyst according to any one of [1] to [3], wherein the metal oxide is represented by the following formula (1): Mo １ V ａ Sbｂ Nb ｃ T ｄ Z ｅ O ｎ ...(1) (in formula (1), T is at least one element selected from the group consisting of Ti, W, Mn, and Bi, Z is at least one element selected from the group consisting of La, Ce, Yb, and Y, a to e are atomic ratios of each element when Mo is defined as 1, and satisfy the following relationships: 0.05≦a≦0.35, 0.05≦b≦0.35, 0≦c≦0.25, 0≦d≦0.20, and 0≦e≦0.10, n is the number of oxygen atoms required to satisfy the valence requirements of other elements present). [6] The catalyst according to any of [1] to [5], wherein the average particle size of the catalyst is 35 μm or more and 75 μm or less. [7] The catalyst according to any of [1] to [6], wherein the catalyst includes a support. [8] The catalyst according to [7], wherein the support contains silica, and the amount of the silica is 30% by mass or more and 70% by mass or less, based on the mass of the catalyst. [9] A method for producing an unsaturated nitrile, comprising: a step 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 a gas phase in the presence of the catalyst according to any one of [1] to [8].

[10] A method for producing an alkene having 2 to 6 carbon atoms, comprising: a step of reacting an alkane having 2 to 6 carbon atoms with molecular oxygen in a gas phase in the presence of the catalyst according to any one of [1] to [8].

[11] A method for producing the catalyst according to any one of [1] to [8], wherein an untreated catalyst containing a metal oxide containing at least Mo, V, and Sb contains Sb. ２ O ４

[12] The production method according to

[11] , wherein the production step comprises calcining the untreated catalyst at 500°C to 700°C in an inert gas atmosphere containing water.

[13] The production method according to

[11] or

[12] , further comprising, before the production step, a step of adding an Sb-containing compound and / or a Mo-containing compound to the untreated catalyst.

[14] The production method according to any one of

[11] to

[13] , further comprising, before the production step, a step of carrying out a gas-phase catalytic oxidation reaction in the presence of the untreated catalyst.

[15] The production method according to any one of

[11] to

[13] , further comprising, before the production step, a step of adding an Sb-containing compound and / or a Mo-containing compound to the untreated catalyst. ２ O ５ Origin of Sb and Sb ６ O １３

[16] The method according to any one of

[11] to

[14] , wherein the total amount of Sb derived from the untreated catalyst is less than 0.1 mass% based on the mass of Sb in the untreated catalyst. ２ O ５ Origin of Sb and Sb ６ O １３

[16] The method according to any one of

[11] to

[15] , wherein the total amount of Sb derived from the catalyst is 0.1 mass% or more and 50 mass% or less based on the mass of Sb in the untreated catalyst.

[0011] The catalyst of the present invention is Sb ２ O ４ By including the above, the unsaturated nitrile or alkene can be produced in high yield.

[0012] 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.

[0013] <<Gas Phase Catalytic Oxidation Reaction Catalyst>> The catalyst of this embodiment is a catalyst containing a metal oxide containing at least Mo, V, and Sb, and Sb ２ O ４ The catalyst for gas-phase catalytic oxidation reaction is preferably an ammoxidation catalyst or an alkane oxidation catalyst. ２ O ４The amount of Sb present as Sb ２ O ４ The "quantitative parameter" (described in detail later) is preferably 0.1% by mass or more and 50% by mass or less.

[0014] In the catalyst of this embodiment, the metal oxide and Sb ２ O ４ The term "non-destructively separable" means that the metal oxide and Sb cannot be separated from each other without destroying the catalyst. ２ O ４ The term "non-destructively separable" means that the catalyst is in a particulate form and the particles contain metal oxide and Sb. ２ O ４ The state in which it cannot be separated non-destructively is, for example, a state in which a metal oxide and Sb are contained. ２ O ４ and Sb are integrated together. ２ O ４ and Sb are bonded to the metal oxide. ２ O ４ and Sb is supported on the metal oxide (for example, in the pores of the metal oxide). ２ O ４ Metal oxides and Sb that cannot be separated non-destructively are included. ２ O ４ is simply a mixture of metal oxides and Sb ２ O ４ It is clearly different from the simple mixed metal oxide and Sb ２ O ４ can be separated non-destructively, 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 an opening of 32 μm is used to remove particles smaller than 32 μm, thereby separating the Sb that is simply mixed. ２ O ４ can be separated.

[0015] Furthermore, the catalyst of this embodiment has an absorption spectrum obtained by X-ray absorption fine structure (XAFS) measurement based on the following <0>, and in the radial function distribution curve of the extended X-ray absorption fine structure (EXAFS) spectrum obtained using the parameters described in the following <1>, in the radial distance range of 2.5 Å to 4.5 Å, Sb ２ O ４ and at least one kind of Sb—O—Mo bond, and the Sb calculated under the conditions of <2> below. ２ O ４ The Sb-O-Sb bond coordination number (α) and Sb ２ O ４ The catalyst preferably satisfies the ratio (formula (2) in <3> below) of the total Sb—O—Sb bond coordination number (β) derived from other than the catalyst to the total Sb—O—Mo bond coordination number (γ) of the catalyst, which satisfies the ratio of 0.1 mass % to 50 mass %.

[0016] <0> Conditions for obtaining X-ray absorption spectra by XAFS Measurement facility: SPring-8 Beamline: BL14B2 X-ray source: Continuous X-rays Analyzing crystal: Si (311) Beam size: 1 mm x 5 mm Measurement method: Transmission method Detector: Ionization chamber I ０ Gas: Ar 75%, Kr 25% I １ Gas: Ar 50%, Kr 50% Measurement atmosphere: under air flow Dwell time: 120 msec Absorption edge: Sb K edge Measurement range: absorption edge -300 to 1300 eV Data analysis (Fourier transform) program: REX2000

[0017] <1> EXAFS vibration extraction parameters B.G. Method: Victoreen2 μ Method: Spline Smoothing k Range: 3.000-14.000 k Weight: 3

[0018] <2> Curve fitting conditions In fitting the radial function distribution curve of the EXAFS spectrum obtained under the conditions of <1> above in the radial distance range of 2.5 Å to 4.5 Å, the bulk coordination numbers of each structure were set as follows: Sb-O-Sb bond bulk coordination number (α'): 12 Sb-O-Sb bond bulk coordination number total (β'): 2 Sb-O-Mo bond bulk coordination number total (γ'): 6

[0019] <3> Sb ２ O ４ Quantitative calculation: From the fitting results of the radial function distribution curve in the radial distance range of 2.5 Å to 4.5 Å of the EXAFS spectrum obtained under the conditions of <1> above, Sb ２ O ４ The amount of Sb was determined by using the formula (2). ２ O ４ It is defined as a quantitative parameter. Although the calculation is unit-free, the coordination number ratio is equal to the mass ratio, so the value obtained by the following formula (2) means mass %. ２ O ４ The units of the quantitative parameters are mass %.

[0020] The catalyst of the present embodiment has the above-described configuration, and therefore can produce unsaturated nitriles or alkenes with high efficiency.

[0021] The process by which the present inventors came to design the catalyst of this embodiment having the above-mentioned performance will be explained below, focusing on the ammoxidation reaction. However, the mechanism of action in this embodiment is not intended to be limited to the following. First, when the present inventors carried out an ammoxidation reaction using the ammoxidation catalyst of this embodiment, Sb ２ O ４ It has been found that a higher yield of unsaturated nitrile can be obtained compared to an ammoxidation catalyst not containing Sb (hereinafter also referred to simply as a "conventional catalyst" or an "untreated catalyst"). Furthermore, when a reaction to obtain an unsaturated nitrile by an ammoxidation reaction is carried out for a certain period of time using a conventional catalyst, the yield of the unsaturated nitrile decreases. When this yield decreases, the conventional catalyst containing Sb ２ O４ It was found that a high yield of unsaturated nitrile was obtained by carrying out a process for producing an ammoxidation catalyst. Analysis of the ammoxidation catalyst using various techniques revealed that the antimony (Sb) content was changed by the method for producing the ammoxidation catalyst of the present invention. To investigate the changes in antimony that occurred in more detail, XAFS measurements were performed at the antimony (Sb) K-edge. XAFS is a type of X-ray absorption spectroscopy, and is an analytical technique that can evaluate element-selective valence and local structure by measuring and analyzing the X-ray absorption spectrum of a sample. Because element-selective measurements are possible, structural information can be obtained even when it is difficult to separate structural peaks from those of other elements in X-ray diffraction structure (XRD), etc. XAFS measurements and the EXAFS analysis methods obtained therefrom were performed based on the conditions and techniques described in <1> to <3> above. In this embodiment, measurements are performed in the range of absorption edge +1000 eV or more, which is k = 16 or more in wave number, and Fourier transform is performed in the range of absorption edge +750 eV, which is k = 14 in wave number, which is sufficient to analyze the absorption spectrum derived from the second coordination sphere. Note that, taking into account the degree of wave attenuation, weighting in EXAFS analysis is performed using k ３ The analysis is performed as follows. The parameter values ​​of the curve fitting performed for quantification are not particularly limited, but the curve fitting is performed so that the values ​​are theoretically possible from a physicochemical standpoint. The standard structure was calculated by FEFF calculation using the parameters in <4> below.

[0022] <4> Standard structural parameters Sb-O-Sb (Sb ２ O ４ Origin): Bond length = 3.478 Å, bulk coordination number = 12 Sb—O—Sb (Sb ２ O ４ Sb-O-Mo: bond length = 3.085 Å, at least one of 3.698 Å, bulk coordination number = 6. ２ O ４ The determination is in accordance with the above <2> and <3>.

[0023] As a result of investigation, the present inventors have found that when analyzing the EXAFS spectrum of conventional catalysts, the bond length of Sb ２ O ４ However, when the catalyst of the present invention produced by the catalyst production method of the present invention is subjected to EXAFS spectrum analysis, the Sb—O—Sb bond defined by a bond length of 3.478 Å is observed. ２ O ４ In other words, by subjecting a conventional catalyst to the method for producing the catalyst of the present invention, the presence of Sb—O—Sb bonds was confirmed. ２ O ４ By adjusting the conditions of the method for producing the catalyst described below to a specific range, a catalyst containing Sb can be obtained. ２ O ４ The present inventors have found that the quantitative parameters can be adjusted to a specific range, and that this catalyst can produce unsaturated nitriles in high yield. ２ O ４ Sb in the catalyst Sb, expressed as a quantitative parameter ２ O ４ It has been found that when the amount of Sb present as the catalyst is excessive, the amount of Sb composite oxide in the conventional catalyst is insufficient, resulting in a decrease in performance as an ammoxidation catalyst.

[0024] From the above viewpoint, in the catalyst of this embodiment, Sb ２ O ４ Represented by quantitative parameters, Sb ２ O ４ If the amount of Sb present as Sb is 0.1 mass % or more and 50 mass % or less based on the amount of Sb in the catalyst, the catalyst contains an appropriate amount of Sb. ２ O ４ As a result, unsaturated nitriles or alkenes can be produced in high yield. ２ O ４ Represented by quantitative parameters, Sb ２ O ４ The amount of Sb present as Sb is preferably 1% by mass or more and 25% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, based on the amount of Sb in the catalyst. ２O ４ The quantitative parameters can be adjusted to the above ranges by the degree of treatment described below (for example, calcination treatment in an inert gas atmosphere containing water, and ammoxidation reaction before the calcination treatment).

[0025] (Metal Oxide) In this embodiment, the gas phase catalytic oxidation reaction catalyst has a metal oxide. The metal oxide is preferably supported on a carrier. The metal oxide in this embodiment contains molybdenum (Mo), vanadium (V), and antimony (Sb) as metals, and may contain other metals as needed. In this embodiment, from the viewpoint of catalytic performance, the metal oxide preferably satisfies the following composition formula: Mo １ V ａ Sb ｂ Nb ｃ T ｄ Z ｅ O ｎ ... (1) (In the above formula, 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.)

[0026] (Particle Shape) The gas-phase catalytic oxidation catalyst of this embodiment preferably contains catalyst particles having a spherical shape. In this embodiment, the spherical shape of the catalyst particles can be confirmed, for example, by the circularity of an arbitrary cross section of the catalyst particles. Note that being circular means that the circularity is 0.95 or more.

[0027] (Average particle size: median size) In this embodiment, the median size of the gas-phase catalytic oxidation reaction catalyst particles is not particularly limited, but from the viewpoint of catalytic performance, it is preferably 20 μm or more and 150 μm or less, more preferably 30 μm or more and 100 μm or less, and even more preferably 35 μm or more and 75 μm or less. Here, the median size (average particle size) refers to the median size based on the volume-based particle size distribution, and means the particle size corresponding to a cumulative frequency of 50% in the particle size distribution. The median size (average particle size) can be measured, for example, by a laser diffraction / scattering method based on the Mie scattering theory.

[0028] (Carrier) In this embodiment, the gas-phase catalytic oxidation reaction catalyst particles preferably have a carrier supporting 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 of the catalyst (100 mass%) is SiO ２ In terms of conversion, the content is preferably 30% by mass or more and 70% by mass or less, and more preferably 40 to 60% by mass.

[0029] <<Method for Producing Unsaturated Nitrile>> A method for producing an unsaturated nitrile using the ammoxidation catalyst of the present invention includes a reaction step of reacting an alkane having 1 to 6 carbon atoms (preferably an alkane having 2 to 4 carbon atoms, more preferably an alkane having 3 or 4 carbon atoms, even more preferably propane or isobutane) or an alkene having 2 to 6 carbon atoms (preferably an alkene having 2 to 4 carbon atoms, more preferably an alkene having 3 or 4 carbon atoms, even more preferably propylene or isobutylene) with molecular oxygen and ammonia in the gas phase (gas-phase ammoxidation reaction) in the presence of the ammoxidation catalyst of this embodiment to produce an unsaturated nitrile. Known reaction systems such as fixed bed, fluidized bed, and moving bed systems can be used. Reaction conditions for the gas-phase ammoxidation reaction are not particularly limited, but examples include the following conditions. The molar ratio of oxygen to alkane or alkene supplied to the reaction is preferably 0.1 or more and 6.0 or less, more preferably 0.5 or more and 5.0 or less. The molar ratio of ammonia to alkane or alkene is preferably 0.3 to 1.5, more preferably 0.5 to 1.4. The reaction temperature is preferably 300°C to 500°C, more preferably 350°C to 500°C.

[0030] <<Method for Producing Alkenes Having 2 to 6 Carbon atoms>> A method for producing alkenes having 2 to 6 carbon atoms using the vapor-phase catalytic oxidation catalyst (alkane oxidation catalyst) of the present invention includes a reaction step of producing an alkene having 2 to 6 carbon atoms by reacting an alkane having 2 to 6 carbon atoms (preferably an alkane having 2 to 4 carbon atoms, more preferably ethane or propane, and even more preferably ethane) with molecular oxygen in the vapor phase in the presence of the vapor-phase catalytic oxidation catalyst of this embodiment. Known reaction systems such as fixed bed, fluidized bed, and moving bed systems can be used. Reaction conditions for the vapor-phase catalytic oxidation reaction are not particularly limited, but include the following conditions. The molar ratio of oxygen to alkane supplied to the reaction 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 reaction temperature is preferably 300°C or more and 500°C or less, more preferably 350°C or more and 500°C or less. Although not particularly limited, producing ethylene from ethane is preferred.

[0031] <<Method for Producing a Gas-Phase Catalytic Oxidation Reaction Catalyst>> The method for producing a gas-phase catalytic oxidation reaction catalyst is not particularly limited as long as it can produce the catalyst of this embodiment, but it can be preferably produced by the method described below. That is, a preferred method for producing a catalyst includes a step ("pre-reaction step") of carrying out a reaction to obtain unsaturated nitrile by ammoxidation using a conventional catalyst (untreated catalyst) for a certain period of time, a step ("addition step") of adding an Sb-containing compound and / or Mo-containing compound, and a step ("calcination step") of calcining the untreated catalyst in an inert gas atmosphere containing water. The production method of this embodiment is preferably configured as described above, and the calcination step is preferably carried out to obtain Sb. ２ O ４ Therefore, an appropriate amount of Sb can be used to produce unsaturated nitriles or alkenes in high yields. ２ O ４ It is possible to produce a catalyst comprising the following: The pre-reaction step and the addition step may be omitted, but it is preferable to carry out at least one of these steps, and it is more preferable to carry out both of these steps.

[0032] The untreated catalyst is a catalyst before being subjected to the calcination step. The untreated catalyst contains a metal oxide containing at least Mo, V, and Sb. The untreated catalyst preferably further contains a support. The metal oxide of the untreated catalyst is preferably the same as the metal oxide contained in the above-mentioned gas-phase catalytic oxidation reaction catalyst. The support of the untreated catalyst is preferably the same as the support contained in the above-mentioned gas-phase catalytic oxidation reaction catalyst.

[0033] Sb in untreated catalyst ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb and Sb derived from the untreated catalyst is preferably less than 0.1 mass% based on the mass of Sb in the untreated catalyst. Examples of such untreated catalysts include untreated catalysts prior to use in the ammoxidation reaction (pre-reaction step).

[0034] Sb in untreated catalyst ２ O ５ Origin of Sb and Sb ６ O １３The total amount of Sb and Sb derived from the untreated catalyst is preferably 0.1 mass % or more and 50 mass % or less based on the mass of Sb in the untreated catalyst. Examples of such untreated catalysts include untreated catalysts that have been used for a long period of time in the ammoxidation reaction (pre-reaction step). ２ O ５ and Sb ６ O １３ is Sb in the firing process ２ O ４ The Sb in the catalyst after the calcination step can be converted into ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from Sb is preferably less than 0.1 mass % based on the mass of Sb in the catalyst.

[0035] Specific examples of the pre-reaction step include the reactions described in the Examples below.

[0036] The Sb-containing compound used in the addition step is not particularly limited as long as it contains Sb. ２ O ４ The Mo-containing compound used in the addition step is not particularly limited as long as it contains Mo. The Mo-containing compound can contribute to, for example, improving the activity of the metal oxide.

[0037] The amount of Sb in the addition step is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 2 mass% or less, relative to the mass of the catalyst. The amount of Mo in the addition step is preferably 0.1 mass% to 20 mass% relative to the mass of the catalyst, more preferably 0.1 mass% to 10 mass% and even more preferably 0.5 mass% to 5 mass%.

[0038] The concentration of water vapor used in the firing step is preferably 10% to 90%, more preferably 15% to 80%, and even more preferably 20% to 70%. When the water vapor concentration is not 100%, there are no restrictions on the gas species other than water vapor as long as they are inert gases, but it is preferable to use common inert gases such as nitrogen, argon, krypton, and helium.

[0039] Solid-state reactions are significantly affected by the heating atmosphere. In particular, firing in the presence of water vapor promotes the formation, growth, and decomposition of certain compounds. While much remains unknown about the mechanism of action, it is speculated that the collision of water molecules with the solid surface promotes the severing and recombination of chemical bonds on the solid surface, and that this, in turn, temporarily creates defects in the structure, promoting the diffusion of ions and other substances. Compounds containing molybdenum are known to volatilize at temperatures above 700°C. The promotion effect of water vapor on solid-state reactions causes changes in reactive species that would not occur in conventional atmospheres that do not contain water, even at temperatures below 700°C.

[0040] The calcination furnace is not particularly limited, and a commonly used box-type calcination furnace or tunnel-type calcination furnace or the like may be used. There are no limitations on the type of calcination furnace, as long as it is capable of performing treatment under an inert gas atmosphere containing water, such as a flow-through type, a sealed device, or a circulation type, but a flow-through type or a circulation type is preferred in order to maintain a uniform water concentration in the calcination atmosphere.

[0041] The firing temperature in the firing step is preferably 500 to 700°C, more preferably 550 to 650°C. ２ O ４ Quantitative parameters tend to increase.

[0042] The firing time is preferably 1 to 72 hours, more preferably 1 to 12 hours. ２ O ４ Quantitative parameters tend to increase.

[0043] The firing step may be carried out in two or more steps with different firing temperatures. When firing is carried out in two or more steps, the firing temperature in the first step is 500 to 700°C, preferably 550 to 650°C, and the firing temperature in the second step is 400 to 600°C, preferably 450 to 550°C, and a preferred embodiment is that the firing temperature in the second step is lower than that in the first step. The firing time in the first step is preferably 1 to 72 hours, more preferably 1 to 12 hours. In the second step, the firing time is preferably 1 to 12 hours, more preferably 1 to 5 hours.

[0044] Furthermore, when the calcination step is transferred to the next step having a different calcination temperature, it is preferable to calcinate the catalyst continuously without removing the catalyst that has been added. However, for example, a temperature-lowering step may be carried out between the first step and the second step.

[0045] The present embodiment will be described in more detail below with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples as long as the gist of the present embodiment is not exceeded. Various physical properties and evaluations performed in the examples and comparative examples described below were measured by the following methods.

[0046] (Catalyst Performance Test: Ammoxidation Reaction of Propane) The catalyst performance test was carried out by filling a fixed-bed reactor (diameter 10 mm) with 2.0 g of the ammoxidation 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 Pn conversion was 89 to 90%. The yield of acrylonitrile was determined as follows. The number of moles of acrylonitrile produced was determined in advance by analyzing acrylonitrile gas of known concentration using gas chromatography (Shimadzu Corporation "GC2014") to obtain a calibration curve, and then the gas produced by the ammoxidation reaction was quantitatively injected into the GC and measured. The yield of acrylonitrile was calculated from the measured number of moles of acrylonitrile according to the following formula: Yield of acrylonitrile (%)=(number of moles of acrylonitrile produced) / (number of moles of propane fed)×100 Two hours after the start of the ammoxidation reaction, the reaction product gas was analyzed by gas chromatography.

[0047] (Catalyst Performance Test: Ethane Oxidation Reaction) The catalyst performance test was carried out by filling a fixed-bed reactor (diameter 10 mm) with 2.0 g of oxidation 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 was calculated as follows. The number of moles of ethylene produced was measured by analyzing ethylene gas with a known concentration in advance using gas chromatography (Shimadzu Corporation's "GC2014") to prepare a calibration curve. The gas produced by the oxidation reaction was then quantitatively injected into the GC and measured. 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. The reaction product gas was analyzed by gas chromatography two hours after the start of the oxidation reaction.

[0048] (Measurement of Average Particle Diameter) The average particle diameter was calculated using a Microtrac Bell MT3000II (laser diffraction particle size distribution analyzer) as the median diameter.

[0049] (Sb ２ O ５ Origin Sb and Sb ６ O １３ Determination of derived Sb) Sb in catalyst ２ O ５ Origin of Sb and Sb ６ O １３ The Sb content was determined by Rietveld analysis using data obtained from X-ray diffraction measurements. The X-ray diffraction measurement method and Rietveld analysis method are as follows.

[0050] <Measurement method> [X-ray diffraction measurement] X-ray diffraction patterns were obtained using a Bruker AXS D8 Advance under the following conditions. Under these X-ray diffraction conditions, an X-ray diffraction pattern was obtained in the range of 2θ = 5° to 70°. X-ray source: CuKα Detector: LYNXEYE XE (1D mode) Tube voltage: 40 kV Tube current: 25 mA DS (divergence slit): 0.3° Solar slit (incident, receiving side): 2.5° Detector projection width (PSD aperture width): 2.9° Air scatter screen: Used Measurement mode: Two Theta / Theta Mode: PSD high-speed scan Time: 0.5 (s) 2θ / start: 5.0° 2θ / stop: 70.0° Step width: 0.020°

[0051] [Rietveld analysis] Rietveld analysis is a well-known method for estimating a crystal structure. It is a method for estimating a crystal structure by measuring a certain crystal with an X-ray diffraction device (XRD) and defining the information of the measuring device (optical system) and the crystal structure present in the sample for the XRD data obtained, and then adjusting parameters such as the lattice constant and the proportion of crystalline phases so that the measured data and the calculated pattern match. By performing Rietveld analysis, Sb ２ O ５ and / or Sb ６ O １３ The crystal structure data of Sb ２ O ５ and Sb ６ O １３ The crystal structures of Sb and Sb are similar, making it difficult to distinguish between the X-ray diffraction patterns. ６ O １３ Rietveld analysis was performed using the structure of as the initial structure.

[0052] The catalyst according to this embodiment contains P1 crystals and P2 crystals containing Mo, V, and Sb. In this specification, "P1 crystals" refers to crystals having peaks at 22.1±0.5°, 28.1±0.5°, 36.1±0.5°, and 45.2±0.5° in an X-ray diffraction pattern. In this specification, "P2 crystals" refers to crystals having peaks at 7.8±0.5°, 8.9±0.5°, 22.1±0.5°, 27.1±0.5°, 35.2±0.5°, and 45.2±0.5° in an X-ray diffraction pattern.

[0053] The analysis software used was TOPAS (DIFFRAC.TOPAS Version 6) from Bruker AXS. ６ O １３ The crystals were subjected to Rietveld refinement using the structure published in AtomWorks by NIMS in June 2010 ("4296219569" in the NIMS database) as the initial structure. For the P1 crystal, the structure published in Bulletin de la Société Chimique de France, 1971, 3459-3463 ("EntryWithColleCode26303" in the ICSD database) was used as the initial structure. For the P2 crystal, the structure published in Applied Catalysis A: General, 2007, vol. 318, 20, 137-142 ("EntryWithColleCode157165" in the ICSD database) was used as the initial structure. Specifically, Rietveld analysis was performed according to the following procedure.

[0054] <Initial Settings> The optical system and apparatus information such as "Emission Profile (wavelength)" and "Instrument (apparatus constant)" were set according to the measurement conditions, and the background and sample surface height were made variable.

[0055] <Sample information input> Sb ６ O １３For the structure, the initial structure and refinement conditions were specified as follows. "Refine" means that the relevant item is set as a variable parameter and refined to fit the measurement data. "Scale" means the proportion (weight %) that the crystal occupies in the whole, and by refining this, it is possible to determine the proportion of the relevant crystal present in the sample. By enabling Stephens models, Rietveld analysis can be performed taking into account the anisotropy of the crystal. Furthermore, by enabling Strain G, Rietveld analysis can be performed taking into account the crystal strain.

[0056]

[0057] The calculation pattern and the measurement data were fitted under the above conditions. Note that fitting means refining each set parameter such as the lattice constant and the proportion of the crystalline phase so that the calculation pattern matches the measurement data. [Sb ６ O １３ The amount of Sb crystals listed in the table above. ６ O １３ It is obtained by refining the scale of the crystal structure.

[0058] By carrying out Rietveld refinement using the above-mentioned method, it is possible to obtain a calculated XRD pattern that closely matches the experimentally obtained XRD measurement data. ６ O １３ Since it is calculated assuming a crystal structure, the assumed Sb ６ O １３ [Sb ６ O １３ The amount of Sb actually present in the measured sample is ６ O １３ It can be thought of as representing a crystal.

[0059] <Reference Example 1-1> Composition formula is Mo １ V ０．２３ Sb ０．２３ Nb ０．０８ W ０．０３ O ｎ / 49.0% by mass-SiO２ A catalyst represented by the formula (silica-supported catalyst) was prepared as follows.

[0060] [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 was added, followed by Nb ２ O ５ 20.0 kg of niobic acid containing 76.0 mass% as niobium was added, and the two were mixed in water. This solution was heated and stirred at 70°C for 8 hours, to obtain an aqueous mixed solution, which was left to stand, ice-cooled, and then 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 obtained niobium raw material solution was used as a niobium raw material solution in the production of catalysts in the following Examples and Comparative Examples. 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 niobium raw material solution, and was found to be 0.889 mol / kg. 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. The mixture thus obtained was stirred in a water bath at a temperature of 70°C, and ¼ N KMnO ４ The titration was carried out using 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 +8H２ 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.

[0061] [Preparation of Mixture A] 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.

[0062] [Preparation of Slurry-like Aqueous Mixture A] 8.5 kg of niobium raw material solution was mixed with H ２ O ２ 1.7 kg of hydrogen peroxide solution containing 35.3 mass % of SiO was added thereto, and the mixture was stirred and mixed at room temperature for 30 minutes to prepare a mixed solution B. The obtained mixed solution A was cooled to 70°C, and then 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.

[0063] [Preparation of dried particles] The obtained 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 perform the firing step described below continuously, the preparation step of dried particles was repeated.

[0064] [Preparation of calcined particles] Calcination was carried out using a continuous SUS kiln with a diameter of 127 mm and a length of 1150 mm. Specifically, the obtained dried particles were fed at 220 g / Hr and calcined at 360°C for 2 hours in a countercurrent nitrogen flow of 3.6 NL / min to obtain a calcined product. The calcined product was then fed at 130 g / Hr and calcined at 660°C for 2 hours in a countercurrent nitrogen flow of 2.3 NL / min to obtain calcined particles. Protrusions consisting of protruding oxide crystals were present on the surface of the calcined particles.

[0065] [Removal of protrusions] 50 g of calcined particles were introduced into 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, while air was circulating. The airflow length in the airflow direction was 52 mm, and the average linear velocity of the airflow was 310 m / s. When the catalyst (Reference Example 1-1) obtained after 24 hours was examined by SEM, the presence of protrusions on the catalyst surface was not confirmed.

[0066] [Catalytic Performance Test] The AN yield in the ammoxidation reaction of the catalyst of Reference Example 1-1 was 54.8%. XAFS measurement was carried out according to the method described below, and EXAFS extraction and curve fitting were carried out using the parameters described below. As a result, Sb in the catalyst Sb was ２ O ４ The ratio was 0%. The average particle size was 56 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0067] Comparative Example 1-1 [Pre-reaction step] The catalyst (Reference Example 1-1) was subjected to a gas-phase catalytic ammoxidation reaction for producing acrylonitrile from propane. 40 g of the catalyst was packed into a Vycor glass fluidized-bed reactor tube having an inner diameter of 25 mm, and the catalyst was added to a mixed gas having a molar ratio of propane:ammonia:oxygen:helium=1:1.1:2.9:11.6 in accordance with the following definitions for a contact time of 3.0 (sec g / cm) at a reaction temperature of 445°C and a reaction pressure of 60 kPa. ３) was supplied. This reaction was continued for 180 days to obtain a catalyst (Comparative Example 1-1). A catalytic performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 53.9%. XAFS measurement was carried out according to the method described below, and EXAFS extraction and curve fitting were carried out using the parameters described below. As a result, the Sb content in the catalyst Sb was 1.0%. ２ O ４ The ratio was 0%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 3.74 mass % based on the mass of Sb in the catalyst.

[0068] In this embodiment, the contact time is defined by the following formula: Contact time (sec g / cm ３ ) = (W / F) × 273 / (273 + T) where W, F, and T are defined as follows: W = amount of loaded catalyst (g) F = standard condition (0°C, 1.013 × 10 ５ raw material mixed gas flow rate (Ncm ３ / sec) T = reaction temperature (°C)

[0069] Example 1-1 80 g of the above catalyst (Comparative Example 1-1) and ammonium molybdate ((NH ４ ) ６ Mo ７ O ２４ ・4H ２ After mixing 1.6 g of the above-mentioned catalysts (Sb, O, AHM), the mixture was packed into a quartz glass calcination tube having a diameter of 3 inches, and calcined at 600°C for 4 hours while rotating the tube under a flow of a mixed gas of nitrogen gas at 240 NL / min and water vapor at 160 NL / min to obtain a catalyst (Example 1-1). A catalytic performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 55.0%. XAFS measurement was carried out based on the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters, and the Sb content in the catalyst Sb was 1.0 g. ２ O ４ The ratio was 3.72%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0070] Example 1-2 80 g of the above catalyst (Comparative Example 1-1) and ammonium molybdate ((NH ４ ) ６ Mo ７ O ２４ ・4H ２ After mixing 1.6 g of the above-mentioned catalysts (Sb, O, AHM), the mixture was packed into a quartz glass calcination tube having a diameter of 3 inches, and calcined at 550°C for 66 hours while rotating the tube under a flow of a mixed gas of nitrogen gas at 240 NL / min and water vapor at 160 NL / min to obtain a catalyst (Example 1-2). A catalytic performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 55.0%. XAFS measurement was carried out based on the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters, and the Sb content in the catalyst Sb was 1.0 g. ２ O ４ The ratio was 3.69%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0071] Example 1-3 80 g of the above catalyst (Comparative Example 1-1) and ammonium molybdate ((NH ４ ) ６ Mo ７ O ２４ ・4H ２ O, AHM) 1.6 g and diantimony pentoxide (Sb ２ O ５) were mixed and packed into a quartz glass calcination tube having a diameter of 3 inches, and calcined at 550°C for 66 hours while rotating the tube under a flow of a mixed gas of nitrogen gas at 240 NL / min and water vapor at 160 NL / min to obtain a catalyst (Example 1-3). A catalytic performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 55.5%. XAFS measurement was carried out based on the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters, and the Sb in the catalyst Sb was ２ O ４ The ratio was 10.53%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0072] <Comparative Example 1-2> Using the catalyst (Reference Example 1-1), a reaction was continued for 120 days under the same conditions as in Comparative Example 1-1 to obtain a catalyst (Comparative Example 1-2). A catalytic performance test similar to that of Reference Example 1-1 was carried out, and the AN yield was 54.1%. XAFS measurement was carried out based on the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters. As a result, Sb in the catalyst Sb was ２ O ４ The ratio was 0%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 2.36 mass % based on the mass of Sb in the catalyst.

[0073] Example 1-4 80 g of the above catalyst (Comparative Example 1-2) and ammonium molybdate ((NH ４ ) ６ Mo ７ O ２４ ・4H ２After mixing 1.6 g of the above-mentioned catalysts (Sb, O, AHM), the mixture was packed into a quartz glass calcination tube having a diameter of 3 inches, and calcined at 600°C for 4 hours while rotating the tube under a flow of a mixed gas of nitrogen gas at 240 NL / min and water vapor at 160 NL / min to obtain a catalyst (Example 1-4). A catalyst performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 55.2%. XAFS measurement was carried out based on the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters, and the Sb content in the catalyst Sb was 1.0 g. ２ O ４ The ratio was 2.41%. The average particle size was 55 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0074] Example 1-5 80 g of the above catalyst (Reference Example 1-1) and ammonium molybdate ((NH ４ ) ６ Mo ７ O ２４ ・4H ２ O, AHM) 1.6 g and diantimony pentoxide (Sb ２ O ５ ) were mixed, and then packed into a quartz glass calcination tube having a diameter of 3 inches. The tube was rotated under a flow of a mixed gas of nitrogen gas at 240 NL / min and water vapor at 160 NL / min, and calcined at 600°C for 4 hours to obtain a catalyst (Example 1-5). A catalyst performance test was carried out in the same manner as in Reference Example 1-1, and the AN yield was 55.6%. XAFS measurement was carried out according to the method described below, and EXAFS extraction and curve fitting were carried out using the above-mentioned parameters. As a result, the Sb in the catalyst Sb was ２ O ４ The ratio was 6.63%. The average particle size was 56 μm. XRD measurement was performed and the Sb content was determined by the above-mentioned method. ２ O ５ Origin of Sb and Sb ６ O １３ The total amount of Sb derived from the catalyst was 0.0 mass % based on the mass of Sb in the catalyst.

[0075] <Reference Example 2-1> The catalyst (Reference Example 1-1) was subjected to the above-mentioned vapor phase catalytic oxidation reaction of ethane. The ethylene yield was 69.5%.

[0076] Comparative Example 2-1 The catalyst described in Comparative Example 1-1 was subjected to the same catalytic performance test as in Reference Example 2-1. The ethylene yield was 68.0%.

[0077] Example 2-1 The catalyst described in Example 1-1 was subjected to the same catalytic performance test as in Reference Example 2-1. The ethylene yield was 69.8%.

[0078] Example 2-2 The catalyst described in Example 1-2 was subjected to the same catalytic performance test as in Reference Example 2-1. The ethylene yield was 69.6%.

[0079] Example 2-3 The catalyst described in Example 1-3 was subjected to the same catalytic performance test as in Reference Example 2-1, and the ethylene yield was 69.9%.

[0080] Example 2-4 The catalyst described in Example 1-5 was subjected to the same catalytic performance test as in Reference Example 2-1, and the ethylene yield was 69.5%.

[0081] <XAFS Measurement> 1. Preparation for XAFS Measurement In preparation for XAFS measurement, coarse particles of 100 μm or larger and fine particles of 32 μm or smaller were removed from the catalyst using a sieve. The amount of sample used for measurement was calculated using the Victoreen formula, such that the X-ray absorption of the entire sample (Total μt) was 4 or less and the X-ray absorption of Sb (Δμt) was close to 1. Approximately twice the amount of sample determined by the above method was crushed for 1 hour using an automatic mortar (ANM-1000, Nitto). After crushing the sample, the amount of sample determined by the above method was weighed, placed in a powder molding die (φ10 mm, LabNect), and molded using a manual hydraulic pump (SSP-10A, Shimadzu Corporation). The pressure and pressure time during molding were not specified, but were approximately 2 tons and 1 minute, respectively. The molded sample was placed in a nylon-polyethylene bag (Hiryu, manufactured by Asahi Kasei Pax) and sealed.

[0082] 2. XAFS Measurement XAFS measurements were performed at beamline BL14B2 of the SPring-8 large synchrotron radiation facility, and Si(311) was selected as the analyzing crystal. The measurements were performed under air flow. Measurements were performed using the transmission method at the K absorption edge of Sb, measuring the range from 300 eV before the absorption edge to 1300 eV after the absorption edge. Detailed measurement conditions are as described above.

[0083] 3. Data Analysis Data analysis involved extraction of EXAFS vibrations and curve fitting using REX2000. Detailed analysis conditions were as described above. When curve fitting the radial function distribution curve, the difference in bond distance between Sb-O bonds in each Sb oxide was small, so curve fitting was performed over a radial distance range of 2.5 Å to 4.5 Å, where spectra originating from Sb-O-M bonds (M is Sb or Mo), where differences in bond distances are observed, appear. Note that each parameter in the curve fitting was considered positive when it reached a physicochemically appropriate value and the R factor, which indicates the accuracy of the fitting, was smallest.

[0084] 4. Sb ２ O ４ After performing curve fitting using the above method, the above Sb ２ O ４ By substituting the coordination number obtained by curve fitting and the bulk coordination number of each structure into the quantitative parameters, the Sb in the catalyst Sb was calculated. ２ O ４ The ratio was calculated.

[0085] As is clear from Table 2, the catalysts of Examples 1-1 to 1-5 obtained by calcining the catalysts obtained in Comparative Examples 1-1 and 1-2 in the presence of a mixed gas of nitrogen and water vapor were all capable of synthesizing acrylonitrile more efficiently than before calcination.

[0086] As is clear from Table 3, the catalysts of Examples 2-1 to 2-4 obtained by calcining the catalyst obtained in Comparative Example 2-1 in the presence of a mixed gas of nitrogen and water vapor were all capable of synthesizing ethylene more efficiently than before calcination.

[0087]

Claims

1. A metal oxide containing at least Mo, V, and Sb; and Sb ２ O ４ and a catalyst for a gas phase catalytic oxidation reaction, comprising:

2. The catalyst according to claim 1, wherein the gas-phase catalytic oxidation reaction is an ammoxidation reaction or an alkane oxidation reaction.

3. The catalyst has at least two types of Sb—O—Sb bonds and at least one type of Sb—O—Mo bond, and the Sb of the catalyst ２ O ４ Represented by quantitative parameters, Sb ２ O ４ The catalyst according to claim 1 or 2, wherein the amount of Sb present as Sb is 0.1 mass % or more and 50 mass % or less based on the amount of Sb in the catalyst.

4. The metal oxide and the Sb ２ O ４ The catalyst according to claim 1 or 2, wherein the catalyst is in a state in which it cannot be non-destructively separated.

5. 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 is at least one element selected from the group consisting of Ti, W, Mn, and Bi; Z is at least one element selected from the group consisting of La, Ce, Yb, and Y; a through e are atomic ratios of each element when Mo is defined as 1, and satisfy the following relationships: 0.05≦a≦0.35, 0.05≦b≦0.35, 0≦c≦0.25, 0≦d≦0.20, and 0≦e≦0.10; and n is the number of oxygen atoms necessary to satisfy the valence requirements of the other elements present).

6. The catalyst according to claim 1 or 2, wherein the average particle size of the catalyst is 35 μm or more and 75 μm or less.

7. The catalyst according to claim 1 or 2, wherein the catalyst comprises a support.

8. The catalyst according to claim 7, wherein the support contains silica, and the amount of the silica is 30% by mass or more and 70% by mass or less, based on the mass of the catalyst.

9. A method for producing an unsaturated nitrile, comprising the step 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 according to claim 1 or 2.

10. A method for producing an alkene having 2 to 6 carbon atoms, comprising the step of reacting an alkane having 2 to 6 carbon atoms with molecular oxygen in the gas phase in the presence of the catalyst according to claim 1 or 2.

11. The method for producing a catalyst according to claim 1, wherein Sb is added to an untreated catalyst containing metal oxides containing at least Mo, V and Sb. ２ O ４ A production process comprising:

12. The method of claim 11, wherein the producing step comprises calcining the untreated catalyst at 500°C to 700°C in an inert gas atmosphere containing water.

13. The method according to claim 11 or 12, further comprising the step of adding an Sb-containing compound and / or an Mo-containing compound to the untreated catalyst prior to the producing step.

14. The method according to claim 11 or 12, further comprising, prior to said generating step, a step of carrying out a gas-phase catalytic oxidation reaction in the presence of said untreated catalyst.

15. Sb in the untreated catalyst ２ O ５ Origin of Sb and Sb ６ O １３ The method according to claim 11 or 12, wherein the total amount of Sb derived from the catalyst is less than 0.1 mass % based on the mass of Sb in the untreated catalyst.

16. Sb in the untreated catalyst ２ O ５ Origin of Sb and Sb ６ O １３ The method according to claim 11 or 12, wherein the total amount of Sb derived from the catalyst is 0.1 mass % or more and 50 mass % or less based on the mass of Sb in the untreated catalyst.

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