JP6180754B2 - Oxide catalyst, method for producing the same, and method for producing unsaturated aldehyde - Google Patents

Description

  The present invention relates to an oxide catalyst, a method for producing the same, and a method for producing an unsaturated aldehyde using the oxide catalyst.

  Oxidative esterification using at least one selected from the group consisting of propylene and isobutylene and / or at least one selected from the group consisting of t-butyl alcohol and isobutanol as raw materials and an unsaturated aldehyde as an intermediate As a method for producing methyl acrylate or methyl methacrylate by reaction, a method comprising two reaction steps called a direct methacrolein method (hereinafter referred to as “direct meta method”) and a direct methacrylic acid method (hereinafter referred to as “ A method consisting of three reaction steps called the “direct acid method”) is known.

  According to the "Petrochemical Process" (edited by the Petroleum Society of Japan, pages 172 to 176, Kodansha Scientific), the direct acid method uses acrylic acid in three steps: a first oxidation step, a second oxidation step, and an esterification step. This is a process for producing methyl or methyl methacrylate. In the first oxidation step, at least one starting material selected from the group consisting of propylene, isobutylene, and t-butyl alcohol is reacted with molecular oxygen in the presence of a catalyst in a gas phase catalytic oxidation reaction to produce acrolein or methacrochlor. This is a process for producing rain. The second oxidation step is a step of producing acrylic acid or methacrylic acid by subjecting acrolein or methacrolein obtained in the first oxidation step and molecular oxygen to gas phase catalytic oxidation reaction in the presence of a catalyst. It is. The esterification step is a step in which the acrylic acid or methacrylic acid obtained in the second oxidation step is further esterified, and when methanol is used as the alcohol, methyl acrylate or methyl methacrylate is obtained. is there.

  In contrast, in the direct meta method, propylene, isobutylene, and / or t-butyl alcohol are used as raw materials, and a first reaction for producing acrolein or methacrolein by a gas phase catalytic oxidation reaction using a molecular oxygen-containing gas. 2 of the process and the 2nd reaction process of reacting the obtained acrolein or methacrolein, for example, methanol as an alcohol, and molecular oxygen to produce methyl acrylate or methyl methacrylate all at once. It consists of two catalytic reaction steps.

  As described above, an unsaturated aldehyde is produced in the course of both the direct acid method and the direct meta method. The catalyst used for producing such an unsaturated aldehyde as a main component has so far been reported, for example, a composite oxide containing Mo and Bi as essential components, which was found by Sohio in the old days. Catalysts have been reported. Patent Document 1 describes a catalyst that focuses on Mo, Bi, Ce, K, Fe, Co, Mg, Cs, and Rb as the metal constituting the catalyst.

  Such advanced analysis of the structure of the catalyst has become possible due to advances in measurement technology of X-ray absorption continuous fine structure (XAFS) using the large synchrotron radiation facility SPring-8. XAFS is classified into an X-ray absorption near-fine structure (XANES) and an X-ray absorption wide-area continuous fine structure (EXAFS) according to the energy region. According to Non-Patent Document 1, the X-ray absorption spectrum of a substance has a wedge-shaped absorption band in which the absorption coefficient rises sharply for each wavelength unique to each element contained in the substance, and a skirt is drawn on the short wavelength side. Appears. In general, a sharp structure is observed in the vicinity of the absorption band, and a gentle wave is observed in the range of 50 to 1000 eV in terms of photon energy from the absorption edge. The former is XANES and the latter is EXAFS.

  XANES was generated in connection with the process of inner-shell electrons being excited to discontinuous levels, and the information obtained is the symmetry of the arrangement of ligand atoms around the central metal and the average oxidation number of the central metal. Value. EXAFS is caused by the probability of the continuous level being modulated by scattering by surrounding atoms, and the information obtained is the peripheral elements around the central metal and the peripheral structure such as the bond distance. For example, Patent Document 2 describes a catalyst for producing methacrylic acid using XAFS and focusing on Mo, P, and Cu.

International publication 95/35273 pamphlet JP 2012-30212 A

“Characteristics of Solid Catalysts”, Catalysis Society, pp. 124-132, Kodansha Scientific

  As described above, both the direct acid method and the direct meta method produce unsaturated aldehydes in the process, but the requirements for the catalyst differ between the direct acid method and the direct meta method. In the direct acid method, since the final oxidation product is an unsaturated carboxylic acid, the merit of reducing methacrylic acid in the step of obtaining an intermediate unsaturated aldehyde is small, and the higher the total yield of methacrolein and methacrylic acid, the higher the yield. This is a desirable catalyst. In contrast, in the direct meta method, an unsaturated aldehyde is formed in the second reaction step after an unsaturated aldehyde is generated in the first reaction step, and therefore there is no step using an unsaturated carboxylic acid as the target compound. . For this reason, in the oxidation process using a catalyst, only an unsaturated aldehyde is desired to be produced, and the production of an unsaturated carboxylic acid is not preferred.

  Thus, when aiming at optimizing the catalyst for the 1st reaction process of a direct meta method, directionality differs clearly from the catalyst for a direct acid method. The direct meta method does not aim to increase the total yield of unsaturated aldehyde and unsaturated carboxylic acid, but rather a catalyst with a high yield of unsaturated aldehyde and a low yield of unsaturated carboxylic acid. Would be desirable.

  Bismuth-molybdenum catalyst (Bi-Mo) used in the field of the direct meta method from the viewpoint of a catalyst having a high yield of unsaturated aldehyde and a low yield of unsaturated carboxylic acid, Patent Document 1 The catalyst for unsaturated aldehyde production in which iron, cerium or the like is added to the catalyst was studied. As a result, it was found from iron K absorption edge X-ray absorption fine structure analysis that the valence of iron contained in such a conventional catalyst is trivalent. Since the oxide catalyst containing trivalent iron has a relatively strong oxidizing power, the target compound (unsaturated aldehyde) is further oxidized to produce unsaturated carboxylic acid and carbon dioxide. There is a problem that the selectivity of saturated aldehyde is lowered.

  The present invention has been made in view of the above problems, and in the production of unsaturated aldehydes using olefins and / or alcohols as raw materials, the production of unsaturated carboxylic acids is low, and the oxidation of unsaturated aldehydes is highly selective. It is an object of the present invention to provide a product catalyst, a production method thereof, and a production method of an unsaturated aldehyde using an oxide catalyst.

  The present inventors diligently studied to solve the above problems. As a result, an oxide catalyst having a predetermined first inflection point in the pattern obtained by first-order differentiation of the iron K absorption edge X-ray absorption fine structure spectrum is suitable for generating an unsaturated aldehyde. The present invention has been found by finding that it has a sufficient oxidizing power and can solve the above problems.

  In addition, by performing firing in an inert gas atmosphere and controlling the oxidation-reduction degree of the temporarily fired body, the production of the trivalent iron compound of the finally obtained oxide catalyst is suppressed, and the bivalent As a result, it was found that an oxide catalyst capable of suppressing the above-mentioned problems can be produced.

That is, the present invention is as follows.
[1]
Contains molybdenum, bismuth, iron, cobalt, and cerium,
An olefin in which a first inflection point in a pattern obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of the iron combined with the molybdenum appears in X-ray energy of 715.5 to 7127.0 eV And / or an oxide catalyst for producing an unsaturated aldehyde using alcohol as a raw material .
[2]
The oxide catalyst according to [1], which has a composition represented by the following composition formula (1).
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt, and Ce represents cerium.
A represents at least one element selected from the group consisting of potassium, cesium, and rubidium;
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, praseodymium, neodymium, and europium,
a to f indicate the atomic ratio of each element to the Mo12 atom, and 1.5 ≦ a ≦ 6, 2 ≦ b ≦ 6, 2 ≦ c ≦ 8, 0.5 ≦ d ≦ 6, 0.01 ≦ e ≦ 2 and 0 ≦ f <2,
g is the number of oxygen atoms determined by the valence of the constituent elements other than oxygen. )
[3]
A method for producing the oxide catalyst according to [1] or [2],
A mixing step of mixing a raw material containing molybdenum, bismuth, iron, cobalt, and cerium with an oxidizing agent and a reducing agent to obtain a raw material slurry;
A drying step of drying the raw slurry to obtain a dried body;
A pre-baking step of pre-baking the dried body to obtain a pre-fired body;
A main calcination step of subjecting the temporary calcination body to an oxide catalyst;
Including
The preliminary firing step and the main firing step are performed in an inert gas atmosphere,
The method for producing an oxide catalyst, wherein, in the preliminary calcination step, the reduction rate of the calcined product is controlled to be 10% or more and less than 100%.
[4]
The method for producing an oxide catalyst according to [3], further comprising an aging step of aging the raw slurry at a temperature of 20 ° C or higher.
[5]
The method for producing an oxide catalyst according to [3] or [4], wherein 1 to 40% by mass of the reducing agent is added to the raw material.
[6]
Using the oxide catalyst according to [1] or [2], at least one olefin selected from the group consisting of propylene and isobutylene, and / or selected from the group consisting of isobutanol and t-butyl alcohol A method for producing an unsaturated aldehyde, comprising a step of oxidizing at least one alcohol.

  According to the present invention, in the production of unsaturated aldehydes using olefins and / or alcohols as raw materials, an oxide catalyst that produces less unsaturated carboxylic acids and has a high selectivity for unsaturated aldehydes, a method for producing the same, and oxides A method for producing an unsaturated aldehyde using a catalyst can be provided.

2 is a diagram showing first-order differential X-ray absorption spectra for the catalysts of Example 1 and Comparative Example 1. FIG.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified within the scope of the gist.

[Oxide catalyst]
The oxide catalyst according to the present embodiment contains molybdenum, bismuth, iron, cobalt, and cerium,
The first inflection point in the pattern obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of the iron complexed with the molybdenum appears in the X-ray energy of 715.5 to 7127.0 eV.

(1) Crystal structure
The oxide catalyst according to the present embodiment contains molybdenum, bismuth, iron, cobalt, and cerium, and is obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of iron complexed with molybdenum. One inflection point appears in X-ray energy of 715.5 to 7127.0 eV. Table 1 shows the relationship between the valence of Fe and the first inflection point in the pattern obtained by first-order differentiation of the iron K absorption edge X-ray absorption fine structure spectrum.

As shown in Table 1, in the complete Fe ³⁺ state such as Fe ₂ Mo ₃ O ₁₂ , the first inflection point appears in the X-ray energy of 7127.8 ± 0.1 eV. On the other hand, in a complete Fe ²⁺ state such as FeMoO ₄ , the first inflection point appears in the X-ray energy of 715.3 ± 0.1 eV. Here, the “first inflection point” referred to in the present specification refers to a pattern obtained by first-order differentiation of the X-ray absorption fine structure spectrum as shown in FIG. 1 7100.0 to 7150.0 eV. It means the point that takes the maximum value within the range of.

As described above, when the first inflection point is in the range of 715.5 to 7127.0 eV, the selectivity of the unsaturated aldehyde of the oxide catalyst is improved. The reason for this is not clear, but if the first inflection point is within this range, it is suggested that the iron in the catalyst has an intermediate valence that is neither trivalent nor divalent. Therefore, the iron in the catalyst is not in a complete Fe ³⁺ state such as Fe ₂ Mo ₃ O ₁₂ , whereas it is not in a Fe ²⁺ state such as FeMoO ₄ but in the form of Fe ^3-δ or Fe ^{2 + δ} . Suggests it exists. When the value of the X-ray energy is in the above range, the iron atom is dissolved in an active species such as Bi—Mo—O of the catalyst or Co—Mo—O, and the oxidation state of the iron atom, Bi—Mo—O, etc. And the coordinated state of iron to Co—Mo—O are optimized. This is considered to be because Fe ₂ Mo ₃ O ₁₂ and Fe ₂ O ₃ crystals, which are compounds that generate unsaturated carboxylic acid and carbon dioxide, are not generated even during redox during the reaction.

  The first inflection point in the pattern obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of iron combined with molybdenum appears in the X-ray energy of 7125.5 to 7127.0 eV, preferably 7125 It appears in X-ray energy of 0.5 to 7126.5 eV, and more preferably appears in X-ray energy of 715.6 to 7126.0 eV. When the X-ray energy is smaller than 715.3 ± 0.1 eV, the valence of iron becomes completely divalent, and is in an overreduced state, resulting in a decrease in yield. On the other hand, when the X-ray energy is higher than 7127.0 eV, iron is completely trivalent and oxidized, the production of unsaturated carboxylic acid and carbon dioxide is promoted, and the selectivity of unsaturated aldehyde is lowered.

As shown in Table 1, the first inflection point of αF ₂ O ₃ (iron oxide (III)) is known to appear in the range of 716.1 ± 0.1, but is a simple oxide. Since iron (III) oxide is not complexed with molybdenum, it does not exhibit useful activity in the production of unsaturated aldehydes. In addition, Fe foil exists as metallic iron (zero valent), and FeO (divalent iron oxide) exists as divalent iron oxide. Both are outside the range of 715.5-7127.0 eV and are not complexed with molybdenum and therefore do not exhibit useful activity in the production of unsaturated aldehydes.

  In addition, it can be confirmed by XRD whether the oxide catalyst according to the present embodiment has iron complexed with molybdenum. Specifically, the diffraction angle (2θ) in an X-ray diffraction diagram obtained using CuKα rays as an X-ray source is at least 12.99 ° ± 0.3 °, 18.30 ° ± 0.3 °, 23.02. If there is a diffraction peak in the range of ° ± 0.3 °, 28.20 ° ± 0.3 °, 33.65 ° ± 0.3 °, 46.15 ° ± 0.3 °, the oxide catalyst Judged to have iron complexed with molybdenum.

<Method for Measuring Fe-K Absorption Edge X-ray Absorption Fine Structure (XAFS) Spectrum>
The measurement of the X-ray absorption fine structure of the K absorption edge of iron can be performed under the following conditions in the beam line BL08B2 of the SPring-8, a large synchrotron radiation research center, a high-intensity photoscience research center. The Fe-K XAFS can be measured by other methods, and the measurement method is not limited.

Optical system and detector: X-ray energy is dispersed using a Si (111) double crystal spectrometer and XAFS measurement is performed by a transmission method. An ion chamber is used for the detector. N ₂ 100% gas is circulated in the ion chamber on the incident X-ray (I0) side, and a gas containing Ar25% and N ₂ 75% is circulated in the ion chamber on the X-ray (I1) side after passing through the sample. . Regarding the electrode length of the ion chamber, the electrode length of the ion chamber on the incident X-ray (I0) side is 140 mm, and the electrode length of the ion chamber on the X-ray (I1) side after passing through the sample is 280 mm. The applied voltage at each electrode of the ion chamber is 960V. The measurement is performed with the gain setting of the current amplifier performing voltage conversion and amplification of the current signal in the ion chamber of the X-ray (I0) and X-ray (I1) being 1E + 8V / A.

  Energy calibration: Measurement is performed using a 3.4 μm-thick Fe foil, and the first inflection point is obtained to obtain an energy value of 7110.08 eV. In the XAFS analysis method used in the present invention, the X-ray absorption fine structure (XAFS) of the iron K absorption edge is measured, and the X-ray absorption near structure (XANES: X-ray) is measured. By analyzing the Absorption Near Edge Structure portion, the electronic state (valence and bonding state) of the metal can be evaluated. The XAFS measurement method as described above is described in "X-ray absorption fine structure-measurement and analysis of XAFS-, Spectroscopical Society Measurement Method Series 26, pages 8-10" and the like.

  A more specific measuring method is shown below. The sample oxide catalyst and 3-10 mg of the standard substance are sufficiently pulverized using an agate mortar, an appropriate amount of boron nitride is added as a diluent, and further mixed and pulverized to obtain a sample. This sample is formed into a pellet having a thickness of 1 mm and a diameter of 10 mm using a stainless steel mold, and the sample is arranged so that the incident beam is substantially at the center of the pellet. Irradiate X-rays in the range absorbed by iron atoms, measure the values of X-ray intensities I0 and I1 before and after the sample, the X-ray energy on the horizontal axis, and the absorbance μ = ln (I0 / I1) on the vertical axis The X-ray absorption spectrum is plotted in FIG. The X-ray absorption spectrum is normalized by the method described in “X-ray absorption spectroscopy -XAFS and its application-, published by IPC Co., Ltd., pages 59-60”, and a pattern obtained by first-order differentiation is obtained on the first floor. Let it be a differential X-ray absorption spectrum.

  The first inflection point is read from the X-ray absorption data and is set as the energy value E0 at the absorption edge. The absorption edge energy position of the XANES spectrum corresponds to the binding energy, and the absorption edge shifts to the higher energy side as the valence of the absorption atom increases, and the absorption edge shifts to the lower energy side as the valence of the absorption atom decreases.

(2) Composition The oxide catalyst according to the present embodiment preferably has a composition represented by the following composition formula (1). By having such a composition, in the production of unsaturated aldehydes using olefins and / or alcohols as raw materials, the production of unsaturated carboxylic acids is less, and the selectivity of unsaturated aldehydes tends to be higher.
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt, and Ce represents cerium.
A represents at least one element selected from the group consisting of potassium, cesium, and rubidium;
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, praseodymium, neodymium, and europium,
a to f indicate the atomic ratio of each element to the Mo12 atom, and 1.5 ≦ a ≦ 6, 2 ≦ b ≦ 6, 2 ≦ c ≦ 8, 0.5 ≦ d ≦ 6, 0.01 ≦ e ≦ 2 and 0 ≦ f <2,
g is the number of oxygen atoms determined by the valence of the constituent elements other than oxygen. )

  The oxide catalyst according to the present embodiment includes Mo, Bi, Ce, and Fe. Thereby, each metal element is compounded in the Mo-Bi metal oxide.

Bi and Mo are easy to form complex oxides such as Bi ₂ Mo ₃ O ₁₂ and Bi ₂ MoO ₆ which are active species such as gas phase catalytic oxidation and ammoxidation reaction, and have high catalytic activity. On the other hand, these composite oxides have a low melting point and low heat resistance. On the other hand, Ce and Mo hardly form a composite oxide such as Ce ₂ Mo ₃ O _12, but these composite oxides have a high melting point and high heat resistance. Therefore, the oxide catalyst according to the present embodiment includes Mo, Bi, and Ce, and by appropriately combining these, Bi is solid-solved and combined into heat-resistant Ce ₂ Mo ₃ O _12. A complex oxide having a high structure and having both high activity and heat resistance is formed. From such a viewpoint, the atomic ratio a of Bi with respect to the Mo12 atom is preferably 1.5 ≦ a ≦ 6, more preferably 2 ≦ a ≦ 5, and further preferably 2 ≦ a ≦ 4. . When the atomic ratio a is within the above range, the selectivity of the unsaturated aldehyde tends to be higher. The atomic ratio d of Ce is preferably 0.5 ≦ d ≦ 6, more preferably 1 ≦ d ≦ 5, and further preferably 1 ≦ d ≦ 4. When the atomic ratio d is within the above range, the heat resistance tends to be higher.

The oxide catalyst according to this embodiment includes Fe. By including Fe, the catalytic activity can be enhanced without lowering the selectivity of the target product. Therefore, Fe is an essential element for industrially synthesizing a target product, like Mo and Bi. However, as described above, when the trivalent Fe content increases, Fe ₂ O ₃ is generated, and by-products such as CO and CO ₂ increase, and the selectivity of the target product tends to decrease. In conventional oxide catalysts, since Fe exists in a trivalent state, Fe has not been effectively used. In this regard, the present inventors have found that the oxidation state of Fe in the oxide catalyst containing trivalent Fe can be changed by devising the preparation method and the calcining method than in the past, and in a predetermined oxidation state. It has been found that the selectivity of the target product (unsaturated aldehyde) can be further increased if it exists. Specifically, if the first inflection point in the pattern obtained by first-order differentiation of the iron K absorption edge X-ray absorption fine structure spectrum is an oxidation state appearing in X-ray energy of 715.55.57127.0 eV The inventors have found that the selectivity of the target product (unsaturated aldehyde) can be further increased.

  The atomic ratio b of Fe to Mo12 atoms in the oxide catalyst according to this embodiment is 2 ≦ b ≦ 6, preferably 2.5 ≦ b ≦ 5, and more preferably 3 ≦ b ≦ 4.5. By being in such a range, the selectivity of the target product (unsaturated aldehyde) tends to be higher.

The oxide catalyst according to this embodiment includes Co. Co is an essential element for industrially synthesizing a target product like Mo, Bi, and Fe, and forms a composite oxide CoMoO ₄ to highly disperse active species such as Bi—Mo—O. It plays a role as a carrier of oxygen and takes in oxygen from the gas phase and supplies it to Bi-Mo-O or the like. In order to obtain an unsaturated aldehyde in a high yield, it is preferable that Co is complexed with Mo to form a complex oxide CoMoO ₄ . The atomic ratio c of Co is preferably 2 ≦ c ≦ 8, more preferably 2.5 ≦ c ≦ 6, and further preferably 3 ≦ c ≦ 5. When the atomic ratio c is in the above range, formation of single oxides such as Co ₃ O ₄ and CoO tends to be reduced.

The oxide catalyst according to this embodiment may include A. A represents at least one element selected from the group consisting of potassium, cesium, and rubidium. A is considered to exhibit a role of neutralizing acid sites such as MoO ₃ that have not been complexed by the catalyst in the catalyst for producing an unsaturated aldehyde. In addition, even if it does not contain potassium, cesium, and rubidium in an oxide catalyst, it does not affect the valence of iron. The atomic ratio e of these elements to Mo12 atoms is preferably 0.01 ≦ e ≦ 2, more preferably 0.03 ≦ e ≦ 1, and 0.05 ≦ e from the viewpoint of catalytic activity. More preferably, ≦ 0.4. When the atomic ratio e is in the above range, the catalyst is hardly made basic, and is easily adsorbed by the catalyst in the oxidation reaction of olefin or alcohol as a raw material, and the catalytic activity tends to be more excellent.

B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, praseodymium, neodymium, and europium. Among them, nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, and lead are substituted with some cobalt in the oxide to stabilize the crystal structure of CoMoO ₄ in the catalyst. It is considered to be. In addition, lanthanum, praseodymium, neodymium, and europium are considered to have a role of forming a composite oxide with molybdenum and improving activity. The atomic ratio f of B is preferably 0 ≦ f <2, more preferably 0.1 ≦ f ≦ 1.5, and further preferably 0.2 ≦ f ≦ 1. When the atomic ratio f is within the above range, the yield of the unsaturated aldehyde tends to be further improved. The element represented by B stabilizes the crystal structure of CoMoO _{4 in} the catalyst or improves the activity of the catalyst, does not affect the valence of iron, and has a content of zero (f = 0 ) May be positioned as an optional component.

(3) Components other than metal oxide The oxide catalyst according to the present embodiment may contain a carrier for supporting the above-described oxide. By including the support, the oxide catalyst can be highly dispersed, and the supported metal oxide tends to have high wear resistance. When the catalyst is molded by an extrusion molding method, it is preferable to include a carrier component.

  Although it does not specifically limit as a support | carrier, For example, a silica, an alumina, a titania, a zirconia is mentioned. Among these, silica is a preferable support in that it is inactive as compared with other supports and has a good binding action on metal oxides without reducing the selectivity to the target product. Further, the silica support is preferable in that it can easily impart higher wear resistance to the supported metal oxide. When the catalyst is molded by the extrusion molding method, the content of the carrier with respect to the whole catalyst is preferably 5 to 10% by mass.

  In the case of a catalyst used in a fluidized bed reactor, it is preferable to use silica as a support from the same viewpoint as described above. The upper limit of the content of the carrier in the catalyst is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less with respect to the total mass of the catalyst. 20 mass% or more is preferable with respect to the total mass of a catalyst, as for the minimum of content of a support | carrier, 30 mass% or more is more preferable, and 40 mass% or more is further more preferable. When the upper limit of the content of the carrier is 80% by mass or less, it is difficult to affect the valence of Fe, the apparent specific gravity can be adjusted, and the fluidity tends to be further improved. Further, when the lower limit of the content of the support is 20% by mass or more, in the case of a catalyst that requires strength such as for fluidized bed reaction, the resistance to crushing and abrasion resistance tend to be higher.

  In addition, when producing methacrolein in a fixed bed reactor, a support may not be included in the case of making a tablet-molded catalyst.

[3] [Production method of oxide catalyst]
In the method for producing an oxide catalyst according to the present embodiment, a raw material slurry is obtained by mixing a raw material for forming an oxide catalyst containing molybdenum, bismuth, iron, cobalt, and cerium with an oxidizing agent and / or a reducing agent. A mixing step;
A drying step of drying the obtained raw material slurry to obtain a dried body,
A pre-baking step of pre-baking the obtained dry body to obtain a pre-fired body;
A main firing step of subjecting the obtained temporary fired body to a main firing to obtain an oxide catalyst;
Including
The preliminary baking step and the main baking step are performed in an inert gas atmosphere,
In the temporary firing step, the reduction rate of the temporary fired body is controlled to be 10% or more and less than 100%.

  As described above, the present inventors have focused on obtaining crystals in which the valence of iron in the catalyst has an intermediate valence between trivalent and divalent, and comprehensively studied its preparation method. did. However, simply optimizing the composition ratio does not result in a crystal in which iron like the oxide catalyst according to the present embodiment has an intermediate valence between trivalent and divalent.

  It has been found that by controlling the oxidation-reduction degree in the oxide catalyst, crystals in which iron has an intermediate valence between trivalent and divalent can be obtained for the first time. Surprisingly, by controlling the iron in the oxide catalyst after the main calcination to an intermediate valence between trivalent and divalent, and controlling the oxidation-reduction degree, Mo, Bi and Ce are It has been found that a composite oxide Bi—Ce—Mo—O can be formed, and an oxide catalyst as described above can be obtained.

  That is, by a new manufacturing technology that satisfies the three conditions of (a) a specific constituent element, (b) a specific slurry preparation method, and (c) a specific firing method, iron is between trivalent and divalent. Crystals with intermediate valences can be obtained

  By controlling the valence of iron in the oxide catalyst to an intermediate valence between trivalent and divalent by a new manufacturing technology that satisfies the above three conditions, the K absorption edge X-ray absorption of iron The first inflection point in the pattern obtained by first-order differentiation of the fine structure spectrum appears in the X-ray energy of 715.5 to 7127.0 eV. Thus, when the valence of iron is controlled to an intermediate valence between trivalent and divalent, the yield of unsaturated aldehyde is further improved.

  As described above, the iron valence is controlled to be an intermediate valence between trivalent and divalent, and the redox degree is such that Mo, Bi, and Ce form Bi—Ce—Mo—O. The design concept of the oxide catalyst that controls the catalyst is a completely new finding that has never existed before. According to this embodiment, it is possible to synthesize a novel structure oxide catalyst containing a large amount of iron having a valence which is not found in conventional oxide catalysts. When used as a catalyst, such an oxide containing a large amount of iron of valence increases the reoxidation rate, becomes more active, and makes the redox cycle of the catalyst during the reaction more advantageous. But the reaction proceeds. For this reason, the by-product of an oxygen addition compound can be suppressed as much as possible.

  In the method for producing an oxide catalyst according to the present embodiment, a raw material slurry is obtained by mixing a raw material for forming an oxide catalyst containing molybdenum, bismuth, iron, cobalt, and cerium with an oxidizing agent and / or a reducing agent. A mixing step, a drying step of drying the obtained raw material slurry to obtain a dried body, a temporary firing step of temporarily firing the obtained dried body to obtain a temporarily fired body, and a main firing of the obtained temporarily fired body And a main firing step of obtaining an oxide catalyst. Hereinafter, the preferable aspect of each process is demonstrated in detail.

(1) Preparation of raw materials [mixing step]
In the mixing step, a raw material slurry is obtained by mixing a raw material for forming an oxide catalyst containing molybdenum, bismuth, iron, cobalt, and cerium with an oxidizing agent and / or a reducing agent.
If necessary, each element source of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, praseodymium, neodymium, and europium can be included in the raw slurry. These can be used as ammonium salts, nitrates, hydrochlorides, organic acid salts, oxides, hydroxides, carbonates and the like soluble in water or nitric acid. When used as an oxide, a dispersion in which the oxide is dispersed in water or an organic solvent is preferable, and a dispersion in which the oxide is dispersed in water is more preferable. In the case of being dispersed in water, a surfactant such as a polymer may be contained in order to suppress aggregation of the oxide and highly disperse it. The particle diameter of the oxide is preferably 1 to 500 nm, more preferably 10 to 80 nm. When producing an oxide catalyst containing a support, it is preferable to add silica sol as a silica raw material to the raw slurry.

  In order to control the valence of iron, to combine molybdenum, bismuth, and cerium, and to control the redox degree so that Bi-Ce-Mo-O is formed, an oxidizing agent and / or Add reducing agent. From the viewpoint of controlling the degree of reduction of the calcined product described later, the reducing agent is preferably more than the oxidizing agent. It is preferable to use both a reducing agent and an oxidizing agent so that elements other than iron are reduced and other metals are not excessively reduced.

  Although it does not specifically limit as an oxidizing agent, For example, nitric acid, hydrogen peroxide, and perchloric acid are mentioned. These oxidizing agents may be used alone or in combination of two or more.

  Although it does not specifically limit as a reducing agent, For example, water-soluble polymers, such as polyethyleneglycol, polyvinyl alcohol, polyacrylic acid, polycarboxylic acid, polyacrylamide; Polycarboxylic acid, such as aminocarboxylic acids, malonic acid, succinic acid, Examples include amines such as hydrazine, ethylenediamine, and ethylenediaminetetraacetic acid; and organic acids such as glycolic acid, malic acid, oxalic acid, tartaric acid, and citric acid. These reducing agents may be used alone or in combination of two or more.

  In addition, the said oxidizing agent and a reducing agent may be contained from the beginning in the raw material used as each element source in a mixing process. For example, the raw material which comprises an oxide catalyst is used as nitrate, hydrochloride, ammonium salt, organic acid salt, and carbonate.

  The addition amount of the oxidizing agent is preferably added in the range of 0.5 to 50% by mass with respect to the metal oxide, more preferably 10 to 40% by mass, and still more preferably 20 to 40% by mass. When the addition amount is within the above range, the uniformity of the degree of oxidation and reduction tends to be excellent.

The addition amount of the reducing agent is preferably 1 to 40% by mass, more preferably 1 to 30% by mass, and further preferably 3 to 20% by mass with respect to the raw material. When the addition amount is within the above range, the degree of oxidation and reduction tends to be more easily controlled. In addition, when the addition amount is 40% by mass or less, Fe is completely reduced to bivalent, Mo is excessively reduced to MoO ₂ or metal Mo, or Bi is excessively reduced to metal Bi. There is a tendency to be able to suppress.

  The method of preparing the raw slurry is not particularly limited as long as it is a commonly used method. It can be prepared by mixing a solution dissolved in an aqueous solution. The metal element concentration in the slurry after mixing is preferably 1 to 50% by mass, more preferably 10 to 40% by mass, and still more preferably 20 to 40% by mass. When the metal element concentration is within the above range, the uniformity of the degree of oxidation and reduction tends to be excellent.

(Aging process)
When the ammonium salt and nitrate are mixed, precipitation occurs and the slurry is likely to be a raw material slurry. It is preferable to further include an aging step of aging at a temperature of 20 ° C. or higher. By having an aging step, it tends to be a more uniform raw material slurry. In the present specification, “aging” of the slurry means holding the slurry in a suspended state. In order to suspend the slurry, it is preferable to stir the slurry continuously and / or intermittently. In this stirring step, the solid content is pulverized to promote the formation of the catalyst precursor, and to a finer and more uniform slurry. can do. When an oxidizing agent and a reducing agent are mixed, the viscosity of the slurry becomes high, a uniform slurry cannot be formed, and it is difficult to perform uniform reduction in the firing step described later.

  When the raw material slurry is aged, in order to obtain the target composite crystal and / or precursor thereof, it is desirable to heat the raw material slurry to a temperature at which the medium of the raw material slurry is kept in a liquid state. Is preferably 20 ° C to 90 ° C, more preferably 30 ° C to 80 ° C, and still more preferably 50 ° C to 70 ° C. By being in this temperature range, a divalent iron compound and a trivalent iron compound are not generated separately, and the iron valence in the catalyst is an intermediate valence between trivalent and divalent. There is a tendency to obtain crystals. Specifically, when an aging step is performed, a composite oxide represented by AB-Fe (between divalent and trivalent) -Mo-O tends to be generated. On the other hand, when the aging step is not performed, two or more composite oxides such as A-Fe (trivalent) -Mo-O and B-Fe (divalent) -Mo-O are likely to be generated. Tend to be. Among these, from the viewpoint of the conversion rate of the unsaturated aldehyde, it is preferable that a composite oxide represented by AB—Fe (an intermediate between divalent and trivalent) —Mo—O is generated.

  For stirring the raw material slurry, a general stirring means such as a stirring blade or a stirring bar can be used. The stirring can be appropriately selected according to the viscosity of the raw material slurry, but the stirring speed is preferably 50 to 3000 rpm. The aging time required for the production of the catalyst precursor varies depending on the temperature of the slurry and the stirring energy. The higher the temperature and the larger the stirring energy, the shorter the appropriate aging time tends to be. For example, when the slurry temperature is 20 ° C. to 90 ° C. and stirring is performed using a stirrer, the aging time is preferably 1 to 24 hours from the viewpoint of productivity, more preferably 1 to 20 hours, still more preferably 1 to 10 hours.

(2) Drying [drying process]
In the drying step, the raw material slurry obtained in the mixing step is dried to obtain a dried body (for example, dry particles). The drying method is not particularly limited, and can be performed by a generally used method. For example, the drying method can be performed by an arbitrary method such as an evaporation drying method, a spray drying method, or a reduced pressure drying method. As the spray-drying method, a centrifugal method, a two-fluid nozzle method, a high-pressure nozzle method, or the like, which are usually implemented industrially, can be employed. The drying heat source is not particularly limited, but it is preferable to use air heated by, for example, steam or an electric heater. At this time, the temperature at the inlet of the dryer of the spray dryer is preferably 150 to 400 ° C, more preferably 180 to 400 ° C, and further preferably 200 to 350 ° C. By being in the above temperature range, a complex oxide tends to be easily formed.

(3) Firing [temporary firing step]
In the temporary firing step, the dried body obtained in the drying step is temporarily fired to obtain a temporary fired body. The pre-baking step is performed in an inert gas atmosphere. The purpose of the pre-firing is to remove nitric acid remaining in the dried body, and to gently burn the ammonium nitrate and the oxidizing and reducing agents derived from the raw material that is an ammonium salt and the raw material that is the nitrate, and trivalent iron. It is to reduce gradually so that it does not become bivalent. When the dry product contains both an oxidizing agent and a reducing agent, it is preferable to use as little oxide catalyst as possible in order to suppress heat generation, so that the oxidation and reduction can be controlled accurately. Is preferred. It is possible to control oxidation and reduction not with an inert gas such as nitrogen but with oxygen or air diluted with nitrogen. However, if oxygen is contained during the heat treatment, it is difficult to control the heat generation when the reducing agent decomposes and to accurately control the firing time, so firing is preferably performed in an inert gas atmosphere. Although it does not specifically limit as an inert gas, For example, although helium, argon, and nitrogen are mentioned, Nitrogen is preferable from an economical surface.

  Although the said temporary baking process and the main baking process mentioned later are not specifically limited, For example, it can carry out using baking furnaces, such as a rotary furnace, a tunnel furnace, and a muffle furnace.

The temperature range of pre-baking is preferably 120 to 350 ° C, more preferably 150 to 350 ° C, and still more preferably 200 to 350 ° C. The pre-baking time is preferably 0.1 to 24 hours, more preferably 1 to 24 hours, and further preferably 3 to 10 hours. Further, when the temperature is low at 150 ° C. or lower, it is preferable to perform long-time temporary baking, and when the temperature is higher than 330 ° C., it is preferable to perform temporary baking for a short time of 2 hours or less. By setting such temperature and time, crystals of oxide (Fe ₂ Mo ₃ O ₁₂ ) composed of trivalent iron and molybdenum are hardly generated in the preliminary firing stage. As a result, an oxide catalyst having an intermediate valence between trivalent and divalent tends to be easily formed in the main firing described later. Therefore, it is preferable to set the upper limit of the calcination temperature and time to such an extent that crystals of oxide (Fe ₂ Mo ₃ O ₁₂ ) composed of trivalent iron and molybdenum do not occur.

  From the viewpoint of suppressing a rapid combustion reaction at the time of pre-baking, it is preferable that the rate of temperature increase is slow. In the manufacturing method of this embodiment, the obtained oxidizing agent is a multi-component system. Therefore, when the raw material is, for example, a metal nitrate, the decomposition temperature of each metal nitrate is different and the nitric acid moves during the temperature rise, so that the oxide composition after firing tends to be heterogeneous. Moreover, when there are many reducing agents, a sudden heat_generation | fever may occur. Since the degree of oxidation-reduction changes with heat, in order to reduce iron from trivalent to an intermediate valence between trivalent and divalent in the production of an oxide catalyst, there is no sudden heat generation. It is preferable to slowly raise the temperature to remove combustion and decomposition components such as nitric acid and organic matter. From the above viewpoint, the rate of temperature rise is preferably 0.01 ° C / min to 100 ° C / min, more preferably 0.01 ° C / min to 75 ° C / min, and still more preferably 0.01 ° C / min. min to 50 ° C./min. Note that “the nitric acid moves” means that the nitrate is decomposed by heat treatment, the nitric acid is desorbed, and the pre-fired body is moved. This movement of nitric acid dissolves the elements contained in the catalyst, and the elements can also move in the catalyst particles. When the rate of temperature rise is in the above range, the movement of nitric acid and elements is suppressed, and the composition after firing tends to be uniform.

It is defined by an expression. By treating the catalyst with sulfuric acid, the reducing element in the catalyst can be dissolved in a reduced state with little oxidation. This is titrated with potassium permanganate, and the reduction rate of the catalyst is determined from the titration amount.
Reduction rate (%) = x / n × 100
MnO ₄ ⁻ + 5e ⁻ + 8H ⁺ → Mn ²⁺ + 4H ₂ O
Mn ^(n−x) → Men ⁺ + Xe ⁻
(In the formula, x represents the number of electrons, n represents the oxidation number of the metal, Me represents the metal element, and X represents the number of electrons.)

  An example of the reduction rate measurement is shown below. Several hundred mg of the oxide catalyst is weighed in a beaker, 20 ml of 50% sulfuric acid is added, 180 ml of purified water is added, and the mixture is stirred for 60 minutes. Thereafter, titration with potassium permanganate is performed using an automatic potentiometric titrator AT-510 (Kyoto Electronics). The reduction rate is calculated from the amount of potassium permanganate consumed for the oxidation of the catalyst.

  When the reduction rate is 10% or more, iron in the catalyst after the main calcination tends not to be trivalent. In order to prevent overreduction, the reduction rate is preferably less than 100%. The reduction rate is more preferably 20% or more and less than 80%, and further preferably 30% or more and less than 60%. When the reduction rate is within the above range, the iron tends to easily form crystals having an intermediate valence between trivalent and divalent after the main calcination.

[Main firing process]
In the main firing step, the calcined body obtained in the preliminary firing step is finally fired to obtain an oxide catalyst. The purpose of this firing step is to facilitate the formation of a desired crystal structure. According to the knowledge of the present inventors, since the crystal structure is affected by the product of the firing temperature and the firing time, it is preferable to appropriately set the firing temperature and the firing time. The firing temperature is preferably higher than the preliminary firing temperature from the viewpoint of growing crystals. The firing temperature for such firing is preferably 400 to 700 ° C., more preferably 400 to 650 ° C., from the viewpoint of easy formation of crystals in which iron has an intermediate valence between trivalent and divalent. More preferably, it is 450 degreeC-600 degreeC. When firing at such a temperature, the formation of crystals in which iron has an intermediate valence between trivalent and divalent can be promoted by making the product of the firing temperature and the firing time appropriate. From this viewpoint, the firing time is preferably 0.1 to 24 hours, more preferably 1 to 24 hours, and further preferably 3 to 10 hours. From the viewpoint of appropriately adjusting the firing temperature and firing time for the generation of the crystal structure, it is preferable to perform main firing for a long time of about 24 to 72 hours, for example, at a low temperature of 400 ° C. or lower, and a high temperature of 600 ° C. or higher. In this case, from the viewpoint of preventing the surface area of the resulting oxide from becoming too small and reducing the catalytic activity, it is preferable to perform the main firing for a short time of 1 hour or less.

  By performing all of the above steps, a crystal in which iron has an intermediate valence between trivalent and divalent is easily formed.

In the main calcination step, whether or not crystals having an intermediate valence which is neither trivalent nor divalent has been generated can be determined by performing an X-ray absorption fine structure analysis of the oxide catalyst obtained after the main calcination. I can confirm. When the X-ray absorption fine structure analysis of the oxide catalyst is performed after the main calcination, if iron has a crystal having an intermediate valence between trivalent and divalent, as described above, K absorption of iron The first inflection point in the pattern obtained by first-order differentiation of the edge X-ray absorption fine structure spectrum is observed in the X-ray energy of 715.5 to 7127.0 eV. When a crystal of an oxide composed of trivalent iron and molybdenum (Fe ₂ Mo ₃ O ₁₂ ) is generated, a peak appears at 7127.8 ± 0.1 eV, and an oxide composed of divalent iron and molybdenum (FeMoO ₄ ), A peak appears at 715.3 ± 0.1 eV, but in the case of a crystal having an intermediate valence of iron that is neither trivalent nor divalent, the peak is at 7125.5-7127.0 eV. Appears. Using this X-ray energy as an index, it is possible to confirm the formation of crystals in which iron has an intermediate valence between trivalent and divalent. In the present embodiment, if the first inflection point in the pattern obtained by first-order differentiation of the iron K-absorption edge X-ray absorption fine structure spectrum is represented by X-ray energy of 715.5 to 7127.0 eV, It is judged that a crystal in which iron has an intermediate valence between trivalent and divalent is formed.

[Method for producing unsaturated aldehyde]
The method for producing an unsaturated aldehyde according to the present embodiment uses at least one olefin selected from the group consisting of propylene and isobutylene and / or isobutanol and t-butyl alcohol using the oxide catalyst. A step of oxidizing at least one alcohol selected from the group consisting of: Although it does not specifically limit as an unsaturated aldehyde manufactured by this, For example, a methacrolein and acrolein are mentioned. Hereinafter, although the specific example is demonstrated, the manufacturing method of this embodiment is not limited to the following specific examples.

(1) Method for producing methacrolein or acrolein The methacrolein or acrolein is, for example, gas phase catalytic oxidation of propylene, isobutylene, isobutanol, and / or t-butyl alcohol using the oxide catalyst according to the present embodiment. It can be obtained by carrying out the reaction. In the gas phase catalytic oxidation reaction, 1 to 10% by volume of propylene, isobutylene, isobutanol, t-butyl alcohol alone, or a mixed oxygen of these molecules is added to the catalyst layer in the fixed bed reactor. A raw material gas composed of a mixed gas to which a molecular oxygen-containing gas and a diluent gas are added is introduced so that the gas content becomes 1 to 20% by volume. The concentration of propylene, isobutylene, isobutanol, t-butyl alcohol, or a mixed gas thereof is usually preferably 1 to 10% by volume, more preferably 6 to 10% by volume, and still more preferably 7 to 9% by volume. The reaction temperature is preferably from 300 to 480 ° C, more preferably from 350 to 450 ° C, still more preferably from 400 to 450 ° C. The pressure is normal pressure to 5 atm, and the reaction can be carried out by introducing the raw material gas at a space velocity of 400 to 4000 / hr (under normal temperature pressure (NTP) conditions). The molar ratio of oxygen and propylene, isobutylene, isobutanol, t-butyl alcohol alone, or a mixed gas thereof is used from the viewpoint of controlling the outlet oxygen concentration of the reactor in order to improve the yield of unsaturated aldehyde. Usually, it is 1.0-2.0, Preferably it is 1.1-1.8, More preferably, it is 1.2-1.8.

The molecular oxygen-containing gas is not particularly limited, for example, pure oxygen gas, and N _{2 O,} include gas containing oxygen such as air. Among these, air is preferable from an industrial viewpoint. Although it does not specifically limit as a dilution gas, For example, nitrogen, a carbon dioxide, water vapor | steam, and these mixed gas are mentioned. The mixing ratio of the molecular oxygen-containing gas and the diluent gas in the mixed gas preferably satisfies the following inequality condition in terms of volume ratio. Furthermore, the concentration of molecular oxygen in the source gas is preferably 1 to 20% by volume.
0.01 <molecular oxygen / (molecular oxygen-containing gas + dilution gas) <0.3

  Water vapor in the raw material gas may be contained from the viewpoint of preventing coking of the oxide catalyst. On the other hand, in order to suppress by-production of carboxylic acids such as acrylic acid, methacrylic acid, and acetic acid, it is preferable to reduce the water vapor concentration in the dilution gas as much as possible. From such a viewpoint, it is preferable that the water vapor in the raw material gas is usually used in the range of 0 to 30% by volume, more preferably 2 to 20% by volume, and more preferably 3 to 10% by volume. More preferably, it is used in a range.

  Hereinafter, the present embodiment will be described in more detail with reference to examples. However, the present embodiment is not limited to the examples described below.

  The atomic ratio of oxygen atoms in the oxide catalyst is determined by the valence conditions of other elements. In the examples and comparative examples, the atomic ratio of oxygen atoms in the formulas representing the composition of the catalyst is Omitted. Further, the composition ratio of each element in the oxide catalyst was calculated from the composition ratio of preparation.

[Measuring method of Fe-K absorption edge X-ray absorption fine structure (XAFS) spectrum]
The measurement of the X-ray absorption fine structure of the K absorption edge of iron was performed under the following conditions in the beam line BL08B2 of SPring-8, a large synchrotron radiation research center, a high-intensity photoscience research center.

Optical system and detector: X-ray energy was dispersed using a Si (111) double crystal spectrometer, and XAFS measurement was performed by a transmission method. An ion chamber was used as a detector. In the ion chamber, a gas of N ² 100% was passed through incident X-rays (I 0) and Ar 25% + N ² 75% was passed through the ion chamber after the sample was transmitted. The electrode length of the ion chamber was 140 mm for I0, 280 mm for I1, and the applied voltage was 960V. The gain setting of the current amplifier that performs voltage conversion and amplification of the current signal for I0 and I1 was measured at 1E + 8 V / A.

  Energy calibration: Measurement was performed using an Fe foil having a thickness of 3.4 μm, and the first inflection point was obtained to obtain an energy value of 7110.08 eV. In the XAFS analysis method used in the present invention, the X-ray absorption fine structure (XAFS) of the iron K absorption edge is measured, and the X-ray absorption near structure (XANES: X-ray) is measured. The electronic state (valence and bonding state) of the metal was evaluated by analyzing the Absorption Near Edge Structure) portion.

  A more specific measuring method is shown below. The oxide catalyst and 3 to 10 mg of the standard substance were sufficiently pulverized using an agate mortar, an appropriate amount of boron nitride was added as a diluent, and further mixed and pulverized to obtain a sample. This sample was formed into a pellet shape having a thickness of 1 mm and a diameter of 10 mm using a stainless steel mold, and the sample was arranged so that the incident beam was substantially at the center of the pellet. Irradiate X-rays in the range absorbed by iron atoms, measure the X-ray intensities I0 and I1 before and after the sample. The X-ray absorption spectrum was plotted in FIG. The X-ray absorption spectrum is normalized by the method described in “X-ray absorption spectroscopy -XAFS and its application-, published by IPC Co., Ltd., pages 59-60”, and a pattern obtained by first-order differentiation is obtained on the first floor. A differential X-ray absorption spectrum was used. The first inflection point was read from the first-order differential X-ray absorption spectrum data.

[Reduction rate]
After the calcination step, the oxide catalyst was acid-treated with sulfuric acid to dissolve the reducing element in the catalyst. This was titrated with potassium permanganate, and the reduction rate of the catalyst was determined from the titration amount. The reduction rate is expressed by the following formula.
Reduction rate (%) = x / n × 100
MnO ₄ ⁻ + 5e ⁻ + 8H ⁺ → Mn ²⁺ + 4H ₂ O
Mn ^(n−x) → Men ⁺ + Xe ⁻

In Examples and Comparative Examples, the conversion rate, selectivity, and yield used to show the reaction results are defined by the following equations, respectively.
Conversion rate = (number of moles of reacted raw material / number of moles of supplied raw material) × 100
Selectivity = (number of moles of compound produced / number of moles of reacted raw material) × 100
Yield = (Mole number of produced compound / Mole number of supplied raw material) × 100

[Example 1]
In a mixed solution containing 86.5 g of ion-exchanged water and 128.0 g of hydrogen peroxide water having a concentration of 30% by mass as an oxidant, 53.6 g of molybdenum trioxide is stirred and mixed at about 70 ° C. and dissolved. A solution (liquid A) was obtained. In addition, 210.4 g of 10% by mass bismuth oxide aqueous dispersion having an average particle diameter of 51 nm, 101.5 g of 10% by mass cerium oxide aqueous dispersion having an average particle diameter of 20 nm, 29.2 g of cobalt nitrate, and 15% by mass of average particles To a liquid obtained by mixing 52.7 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.72 g of a 10% by mass cesium hydroxide liquid, 4.36 g of tartaric acid was added as a reducing agent to obtain a solution (liquid B).

  The oxide catalyst of Example 1 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy of the first inflection point in the pattern obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of iron complexed with molybdenum. Table 3 shows values (hereinafter, also simply referred to as “value of X-ray energy at the first inflection point”).

  For the reaction evaluation of the catalyst, 4.2 g of the oxide catalyst of Example 1 was charged in a jacketed SUS reaction tube having a diameter of 14 mm, isobutylene 8 vol%, oxygen 12.8 vol%, water vapor 3. A mixed gas composed of 0% by volume and 76.2% by volume of nitrogen was aerated at a flow rate of 120 mL / min (NTP) to perform a methacrolein synthesis reaction. The reaction evaluation results are shown in Table 4. Moreover, the first-order differential X-ray absorption spectrum for the oxide catalyst of Example 1 is shown in FIG.

[Example 2]
55.7 g of molybdenum trioxide is added to a mixed solution of 89.8 g of ion-exchanged water and 132.9 g of hydrogen peroxide solution having a concentration of 30% by mass as an oxidant, and the mixture is stirred and mixed at about 70 ° C., and dissolved. (Liquid A) was obtained. Moreover, 103.3 mass g of bismuth oxide aqueous dispersion having an average particle diameter of 51 nm, 103.2 g cerium oxide aqueous dispersion having an average particle diameter of 20 nm, 102.6 g, 42.6 g cobalt nitrate, and 15 mass% average particles. A mixture of 51.3 g of an iron oxide aqueous dispersion having a diameter of 39 nm, 3.87 g of a 10% by mass cesium hydroxide solution and 1.81 g of a 10% by mass potassium hydroxide solution, and 4.57 g of tartaric acid as a reducing agent. This was added to obtain a solution (liquid B).

  The oxide catalyst of Example 2 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  As a reaction evaluation of the catalyst, 4.5 g of the oxide catalyst of Example 2 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Example 3]
48.8 g of molybdenum trioxide is put into a mixed solution containing 78.7 g of ion-exchanged water and 116.5 g of hydrogen peroxide solution having a concentration of 30% by mass as an oxidant, and stirred and mixed at about 70 ° C. to dissolve. A solution (liquid A) was obtained. Further, 107.2% by weight of an aqueous dispersion of bismuth oxide having an average particle diameter of 51 nm, 297.2 g, 103.0% by weight of an aqueous cerium oxide dispersion having an average particle diameter of 20 nm, 22.4 g of cobalt nitrate, and 15% by weight of average particles. 8.72 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 57.0 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.39 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

  The mixed solution obtained by mixing both the A and B solutions was aged at 65 ° C. and a stirring speed of 2500 rpm for 4 hours to obtain a raw material slurry. Using this raw material slurry, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 2 shows the reduction rate of this temporarily fired body. The obtained calcined product was calcined at 510 ° C. for 4 hours in a nitrogen gas atmosphere to obtain an oxide catalyst of Example 3. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  As a reaction evaluation of the catalyst, 5.6 g of the oxide catalyst of Example 3 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Example 4]
A mixed solution of 87.3 g of ion-exchanged water and 129.2 g of hydrogen peroxide solution having a concentration of 30% by mass as an oxidant is charged with 54.1 g of molybdenum trioxide, stirred and mixed at about 70 ° C., dissolved, and dissolved. (Liquid A) was obtained. Also, 10% by mass of an average particle diameter of 51 nm bismuth oxide aqueous dispersion 205.0 g, 10% by mass of an average particle diameter 20 nm cerium oxide aqueous dispersion 97.1 g, cobalt nitrate 25.8 g, 15% by mass of average particles 4.38 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 61.5 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.76 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

  The oxide catalyst of Example 4 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  For the reaction evaluation of the catalyst, 4.5 g of the oxide catalyst of Example 4 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Example 5]
51.5 g of molybdenum trioxide is added to a mixed solution of 83.0 g of ion-exchanged water and 122.8 g of hydrogen peroxide solution having a concentration of 30% by mass as an oxidizing agent, and the mixture is stirred and mixed at about 70 ° C. (Liquid A) was obtained. Also, 106.7% bismuth oxide aqueous dispersion with an average particle diameter of 51 nm, 102.8% cerium oxide aqueous dispersion with an average particle diameter of 20 nm, 112.8 g, cobalt nitrate 26.3 g, and 15 mass% average particles. 4.26 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 47.4 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.57 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

  A mixed liquid obtained by mixing both liquid A and liquid B was aged at 65 ° C. and a stirring speed of 2000 rpm for 4 hours to obtain a raw slurry. Using this raw material slurry, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 2 shows the reduction rate of this temporarily fired body. The obtained calcined product was calcined at 510 ° C. for 4 hours in a nitrogen gas atmosphere to obtain an oxide catalyst of Example 5. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  For the reaction evaluation of the catalyst, 4.8 g of the oxide catalyst of Example 5 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Example 6]
67.6 g of ammonium heptamolybdate was dissolved in 202.7 g of warm water at about 90 ° C. to obtain a solution (solution A). Further, 43.2 g of bismuth nitrate, 22.0 g of cerium nitrate, 42.3 g of iron nitrate, 1.40 g of rubidium nitrate, 9.3 g of nickel nitrate, 4.0 g of magnesium nitrate, and 18.6 g of cobalt nitrate are mixed with 18% by mass of nitric acid. 13.1 g of ascorbic acid as a reducing agent was added to a solution obtained by dissolving in 20.5 g of an aqueous solution and 202.0 g of warm water at about 90 ° C. to obtain a solution (solution B).

  The oxide catalyst of Example 6 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  For the reaction evaluation of the catalyst, 4.7 g of the oxide catalyst of Example 6 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Comparative Example 1]
An oxide catalyst of Comparative Example 1 was obtained by performing the same operation as in Example 1 except that tartaric acid as a reducing agent was not added. The composition of the obtained oxide catalyst is shown in Table 2, and the reduction rate of the calcined product and the value of the X-ray energy at the first inflection point are shown in Table 3.

  As a reaction evaluation of the catalyst, 5.3 g of the oxide catalyst of Comparative Example 1 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4. A first-order differential X-ray absorption spectrum of the oxide catalyst of Comparative Example 1 is shown in FIG.

[Comparative Example 2]
The same operation as in Example 1 was carried out except that no hydrogen peroxide solution as an oxidizing agent was added, and an oxide catalyst of Comparative Example 2 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the reduction rate of the calcined product and the value of the X-ray energy at the first inflection point are shown in Table 3.

  As a reaction evaluation of the catalyst, 5.8 g of the oxide catalyst of Comparative Example 2 was filled in a reaction tube, and a methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Comparative Example 3]
An oxide catalyst of Comparative Example 3 was obtained in the same manner as in Example 1 except that the preliminary firing and the final firing were performed in an air atmosphere. The composition of the obtained oxide catalyst is shown in Table 2, and the reduction rate of the calcined product and the value of the X-ray energy at the first inflection point are shown in Table 3.

  For the reaction evaluation of the catalyst, 5.5 g of the oxide catalyst of Comparative Example 3 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Comparative Example 4]
A solution (A) was prepared by dissolving 72.7 g of ammonium heptamolybdate, 3.9 g of antimony oxide, 3.4 g of paratungsten ammonium, 3.30 g of cesium nitrate, and 10.0 g of bismuth oxide in 218.0 g of warm water at about 90 ° C. Liquid). Also, 4.6 g of lead nitrate, 30.3 g of iron nitrate, 11.0 g of nickel nitrate, 0.67 g of phosphoric acid, and 66.1 g of cobalt nitrate were dissolved in 38.4 g of an 18% by mass nitric acid aqueous solution, 126.2 g of warm water was added to obtain a solution (Liquid B).

  The oxide catalyst of Comparative Example 4 was obtained. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  For the reaction evaluation of the catalyst, 4.9 g of the oxide catalyst of Comparative Example 4 was filled in a reaction tube, and methacrolein synthesis reaction was performed under the same conditions as in Example 1. The reaction evaluation results are shown in Table 4.

[Example 7]
(Production example of acrolein)
A mixed solution of 86.7 g of ion-exchanged water and 128.3 g of hydrogen peroxide solution having a concentration of 30% by mass as an oxidant is charged with 53.7 g of molybdenum trioxide, stirred and mixed at about 70 ° C., dissolved, and dissolved. (Liquid A) was obtained. Further, 100.8% by weight of an average particle diameter of 51 nm bismuth oxide aqueous dispersion 210.8 g, 10% by weight of an average particle diameter 20 nm cerium oxide aqueous dispersion 101.7 g, cobalt nitrate 29.3 g, 15% by weight of average particles 4.36 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 52.8 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 1.40 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

  A mixed solution obtained by mixing both of the liquid A and the liquid B was aged at 65 ° C. with a stirring speed of 2000 rpm for 4 hours to obtain a raw material slurry. Using this raw material slurry, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 2 shows the reduction rate of this temporarily fired body. The obtained calcined product was calcined at 520 ° C. for 4 hours in a nitrogen gas atmosphere to obtain an oxide catalyst of Example 7. The composition of the obtained oxide catalyst is shown in Table 2, and the X-ray energy value at the first inflection point is shown in Table 3.

  As an evaluation of the reaction of the catalyst, 4.8 g of the oxide catalyst of Example 7 was charged into a jacketed SUS reaction tube having a diameter of 14 mm, and at a reaction temperature of 430 ° C., 8% by volume of propylene, 12.8% by volume of oxygen, and 3. Acrolein synthesis reaction was performed by aeration of a mixed gas composed of 0% by volume and 76.2% by volume of nitrogen at a flow rate of 120 mL / min (NTP). The reaction evaluation results are shown in Table 5.

[Comparative Example 5]
An oxide catalyst of Comparative Example 5 was obtained by performing the same operation as in Example 7 except that the preliminary calcination and the main calcination were performed in an air atmosphere. The composition of the obtained oxide catalyst is shown in Table 2, and the reduction rate of the calcined product and the value of the X-ray energy at the first inflection point are shown in Table 3.

  As a catalyst reaction evaluation, 4.9 g of the oxide catalyst of Comparative Example 5 was filled in a reaction tube, and an acrolein synthesis reaction was performed under the same conditions as in Example 7. The reaction evaluation results are shown in Table 5.

  The present invention has industrial applicability as an oxide catalyst used in the production of unsaturated aldehydes by gas phase catalytic oxidation of olefins or alcohols.

Claims (6)

Contains molybdenum, bismuth, iron, cobalt, and cerium,
An olefin in which a first inflection point in a pattern obtained by first-order differentiation of the K absorption edge X-ray absorption fine structure spectrum of the iron combined with the molybdenum appears in X-ray energy of 715.5 to 7127.0 eV And / or an oxide catalyst for producing an unsaturated aldehyde using alcohol as a raw material . The oxide catalyst of Claim 1 which has a composition represented by the following compositional formula (1).
_{Mo 12 Bi a Fe b Co c} Ce d A e B f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt, and Ce represents cerium.
A represents at least one element selected from the group consisting of potassium, cesium, and rubidium;
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead, lanthanum, praseodymium, neodymium, and europium,
a to f indicate the atomic ratio of each element to the Mo12 atom, and 1.5 ≦ a ≦ 6, 2 ≦ b ≦ 6, 2 ≦ c ≦ 8, 0.5 ≦ d ≦ 6, 0.01 ≦ e ≦ 2 and 0 ≦ f <2,
g is the number of oxygen atoms determined by the valence of the constituent elements other than oxygen. ) A method for producing an oxide catalyst according to claim 1 or 2,
A mixing step of mixing a raw material containing molybdenum, bismuth, iron, cobalt, and cerium with an oxidizing agent and a reducing agent to obtain a raw material slurry;
A drying step of drying the raw slurry to obtain a dried body;
A pre-baking step of pre-baking the dried body to obtain a pre-fired body;
A main calcination step of subjecting the temporary calcination body to an oxide catalyst;
Including
The preliminary firing step and the main firing step are performed in an inert gas atmosphere,
The method for producing an oxide catalyst, wherein, in the preliminary calcination step, the reduction rate of the calcined product is controlled to be 10% or more and less than 100%.   The method for producing an oxide catalyst according to claim 3, further comprising an aging step of aging the raw slurry at a temperature of 20 ° C or higher.   The manufacturing method of the oxide catalyst of Claim 3 or 4 which adds 1-40 mass% of said reducing agents with respect to the said raw material.   Using the oxide catalyst according to claim 1 or 2, at least one olefin selected from the group consisting of propylene and isobutylene, and / or at least selected from the group consisting of isobutanol and t-butyl alcohol. A method for producing an unsaturated aldehyde, comprising a step of oxidizing one alcohol.