JP6185255B2 - 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.

  It is known that transition metals such as molybdenum, bismuth, and iron become so-called composite oxides obtained by solid solutions of a plurality of types of metals in addition to oxides obtained by oxidizing each of them. . Complex oxides have different characteristics from single metal oxides, and the characteristics change greatly depending on the selection of metal species and composition ratios. Therefore, various kinds of pigments, battery electrode materials, catalysts, etc. Studies are underway in the field.

  For example, many metal oxide catalysts containing molybdenum, bismuth, and iron have been reported as catalysts for producing unsaturated aldehydes by oxidizing olefins and alcohols. In addition, many composite oxide catalysts containing molybdenum, bismuth and iron as essential components and obtained by heat treatment by adding an organic compound have been reported.

  As described above, the characteristics of the oxide catalyst differ depending on the composition ratio. Therefore, in order to improve the catalytic activity and the production rate of the target compound, the catalytic characteristics of the composite oxide having various composition ratios. And preparation conditions are being studied. For example, Patent Document 1 describes a method for producing a catalyst in which a catalyst precursor containing molybdenum, bismuth and iron is calcined in an atmosphere of a molecular oxygen-containing gas and then heat-treated in the presence of a reducing substance. Yes. Further, in Patent Document 2, in order to obtain a target product with high yield, in an oxide catalyst containing molybdenum, bismuth, iron, cobalt and cerium, the atomic ratio of Fe to Mo12 atoms is 0 <Fe ≦ 2. 5 is described.

JP 2007-117866 A International publication 95/35273 pamphlet

Patent Document 1 describes that in a catalyst containing molybdenum, bismuth and iron, the Fe composition ratio c is 0 <c ≦ 10. However, in practice, even when the Fe composition ratio c is 3 or more, a single oxide of iron or a binary composite oxide of trivalent iron and molybdenum is formed, and is dissolved in CoMoO ₄ . Does not increase the amount of iron. On the other hand, when the Fe composition ratio c is 3 or more and the Fe content increases, Fe ₂ O ₃ is generated in the catalyst. When Fe ₂ O ₃ is present, by-products such as CO and CO ₂ tend to increase when a gas phase catalytic oxidation reaction is performed using the catalyst. Therefore, as described in Patent Document 2, it is a practical range that the atomic ratio of Fe to Mo12 atoms is 0 <Fe ≦ 2.5.

  The bismuth-molybdenum-based (Bi-Mo) catalyst used in the gas phase catalytic oxidation reaction tends to increase the reoxidation rate and improve the activity when it contains iron. As a result, a catalyst containing a large amount of iron can accelerate the reaction even under a low oxygen partial pressure, and the target product can be produced in a high yield without generating an oxygen addition compound (for example, carbon dioxide) other than aldehyde. Makes it possible to get in. Furthermore, when a catalyst containing a large amount of iron is used, redox during the reaction is facilitated, so that an effect of extending the life of the catalyst is also expected.

Since the above effects are expected, it is preferable that a large amount of iron is contained in the oxide serving as a catalyst. However, as described above, the amount of iron dissolved in CoMoO ₄ has a limit, and the composition ratio cannot be set freely high. In other words, in the oxide catalyst containing molybdenum, bismuth, iron, cobalt, and lanthanoid elements, the design of the composition ratio is not free compared to the composition ratio concept that prevents by-products such as carbon dioxide, and the concept is realized. It has not reached.

  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 carbon dioxide is suppressed and unsaturated aldehydes are produced in a high yield. It is an object of the present invention to provide an oxide catalyst that can be produced, a method for producing the oxide catalyst, and a method for producing an unsaturated aldehyde using the oxide catalyst.

  The present inventors diligently studied to solve the above problems. As a result, when the oxide catalyst containing molybdenum, bismuth, iron, cobalt and a lanthanoid element contains a predetermined amount of a complex oxide of trivalent iron and molybdenum, or an iron compound such as iron oxide, this oxidation. It has been found that when a product catalyst is used in an unsaturated aldehyde production reaction, an undesired combustion reaction is promoted and the yield of the target product is not improved.

  The present inventors have found that the cause of the above-mentioned unwanted combustion reaction is due to the fact that a predetermined amount or more of iron forms a complex oxide or a single oxide in a trivalent state. That is, not only the composition of the metal but also the valence of each metal has been found to affect the function of the composite oxide, and all of the iron compounds do not exhibit the negative effects as described above. It has been found that a favorable catalytic action can be exhibited in the state of valence. As described above, the present inventors have found that a catalyst containing an oxide with a controlled redox degree can solve the above-mentioned problems, and have reached the present invention.

  Furthermore, as a result of intensive studies on the means for achieving the control of the oxidation-reduction degree of the oxide catalyst, the present inventors have found that the use of an oxidizing agent and / or a reducing agent, and a reduction firing, Found that an oxide catalyst containing iron in a state can be produced, thereby realizing a composition of a composite oxide catalyst that cannot be obtained by conventional oxidation firing, and finding a method for producing an oxide catalyst that can solve the above-mentioned problems, The present invention has been conceived.

That is, the present invention is as follows.
[1]
Contains molybdenum, bismuth, iron, cobalt and lanthanoid elements,
The ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.3 or more and 0.9 or less,
An oxide catalyst for producing an unsaturated aldehyde using olefin and / or alcohol as a raw material .
[2]
The atomic ratio a of bismuth to 12 atoms of molybdenum is 1.5 ≦ a ≦ 6, the atomic ratio b of iron is 3 ≦ b ≦ 7, and the atomic ratio c of cobalt is 2 ≦ The oxide catalyst according to [1], wherein c ≦ 8 and the atomic ratio d of the lanthanoid element is 0.5 ≦ d ≦ 6.
[3]
The oxide catalyst according to [1] or [2], which has a composition represented by the following composition formula (1).
_{Mo 12 Bi a Fe b Co c} A d B e C f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt,
A represents at least one lanthanoid element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, and europium,
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, and lead;
C represents at least one alkali element selected from the group consisting of cesium, rubidium, and potassium;
a to f indicate the atomic ratio of each element to the Mo12 atom, 1.5 ≦ a ≦ 6, 3 ≦ b ≦ 7, 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. )
[4]
Containing a composite oxide containing the cobalt and the molybdenum;
In the X-ray diffraction, the X-ray diffraction angle (2θ) of the (002) plane of the complex oxide containing cobalt and molybdenum shows a peak (maximum intensity) at 26.15 ° to 26.35 °, The oxide catalyst according to any one of [1] to [3].
[5]
The method for producing an oxide catalyst according to any one of [1] to [4] above,
A mixing step of mixing a raw material containing molybdenum, bismuth, iron, cobalt and a lanthanoid element and an oxidizing agent and / or 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 firing step, the reduction rate of the temporary fired body is controlled to be 60% or more and less than 100%.
[6]
Using the oxide catalyst according to any one of [1] to [4] above, from at least one olefin and / or isobutanol selected from the group consisting of propylene and isobutylene, and t-butyl alcohol A method for producing an unsaturated aldehyde, comprising a step of oxidizing at least one alcohol selected from the group consisting of:

  ADVANTAGE OF THE INVENTION According to this invention, in the manufacture of the unsaturated aldehyde which uses olefin and / or alcohol as a raw material, the production | generation of the oxide catalyst which can suppress the production | generation of a carbon dioxide and can produce an unsaturated aldehyde with a high yield, and its manufacture It is an object of the present invention to provide a method and a method for producing an unsaturated aldehyde using the oxide catalyst.

2 is a diagram showing X-ray diffraction peaks of the oxide catalysts obtained in Example 1, Comparative Example 1, and Comparative Example 2. FIG. It is a figure which shows the enlarged view of 2 (theta) = 25-27 degree of the X-ray-diffraction peak in FIG. 2 is a diagram showing a Mossbauer spectrum of the oxide catalyst obtained in Example 1. FIG. In the figure, δ is an isomer shift, Δ is a quadrupole split, and H is an internal magnetic field. 2 is a graph showing a Mossbauer spectrum of the oxide catalyst obtained in Comparative Example 1. FIG. 4 is a diagram showing a Mossbauer spectrum of the oxide catalyst obtained in Comparative Example 2. FIG. It is a figure which shows the structure and specification of an iron valence measuring device.

  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 this embodiment contains molybdenum, bismuth, iron, cobalt, and a lanthanoid element, and the ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.3 or more and 0.9 or less. The ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is preferably 0.5 or more and 0.8 or less, and more preferably 0.6 or more and 0.8 or less. The content of Fe ²⁺ and Fe ^{3+ in} the oxide catalyst can be measured by the method described in Examples. In this way, by reducing the proportion of trivalent iron (Fe ³⁺ ) and controlling the proportion of divalent iron (Fe ²⁺ ) to an appropriate range, unsaturated aldehydes derived from olefins and / or alcohols are used as raw materials. In production, it is possible to suppress the production of carbon dioxide and produce an unsaturated aldehyde in a high yield.

  The oxide catalyst according to this embodiment includes molybdenum (hereinafter also referred to as “Mo”), bismuth (hereinafter also referred to as “Bi”), iron (hereinafter also referred to as “Fe”), cobalt (hereinafter referred to as “Fe”). And a lanthanoid element (hereinafter also referred to as “A”). As described above, in the Mo—Bi-based metal oxide, each metal element can form a composite oxide by containing Mo, Bi, Fe, Co, and a lanthanoid element. In the oxide catalyst of this embodiment, the atomic ratio a of bismuth with respect to 12 atoms of molybdenum is preferably 1.5 ≦ a ≦ 6, and the atomic ratio b of iron with respect to 12 atoms of molybdenum is 3 ≦ a. It is preferable that b ≦ 7, the atomic ratio c of cobalt to 12 atoms of molybdenum is preferably 2 ≦ c ≦ 8, and the atomic ratio d of lanthanoid element to 12 atoms of molybdenum is 0.5 ≦ d. It is preferable that ≦ 6.

  In the oxide catalyst according to the present embodiment, the atomic ratio a of Bi to Mo12 atoms is preferably 1.5 ≦ a ≦ 6, more preferably 2 ≦ a ≦ 4.5, and 2 ≦ a More preferably, ≦ 4. When the atomic ratio a is in the above range, the selectivity of the target product tends to be higher.

  The atomic ratio b of Fe to Mo12 atoms is preferably 3 ≦ b ≦ 7, more preferably 3.5 ≦ b ≦ 6, and further preferably 3.5 ≦ b ≦ 5. When the atomic ratio b is in the above range, the selectivity of the unsaturated aldehyde tends to be higher.

  The atomic ratio c of Co to Mo12 atoms 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, the yield of unsaturated aldehyde tends to be higher.

  The atomic ratio d of the lanthanoid element to the Mo12 atom is preferably 0.5 ≦ d ≦ 6. It is more preferable that 0.8 ≦ d ≦ 4, and it is further preferable that 1.4 ≦ d ≦ 2. When the atomic ratio d is in the above range, the selectivity of the unsaturated aldehyde tends to be higher.

[Bi-A-Mo-O composite oxide]
The oxide catalyst according to this embodiment includes Bi and Mo. Bi and Mo can be combined to form Bi-Mo-O composite oxides such as Bi ₂ Mo ₃ O ₁₂ and Bi ₂ MoO ₆ that are active species such as gas phase catalytic oxidation and ammoxidation reaction. Such a complex oxide can act as an active species such as gas phase catalytic oxidation and ammoxidation reaction.

  In addition, the oxide catalyst according to the present embodiment further includes a lanthanoid element A. The Bi—Mo—O composite oxide can be combined with the lanthanoid element A to form a Bi—A—Mo—O composite oxide. Such a complex oxide is more excellent in heat resistance. By being excellent in heat resistance, it becomes an oxide catalyst more suitable for reaction at high temperature.

As will be described later, in the present embodiment, in the production of the oxide catalyst, it is preferable to precisely control the oxidation-reduction degree of the oxide catalyst in an inert gas atmosphere at the time of firing. As described above, Mo, Bi, and element A preferably form a Bi-A-Mo-O composite oxide. For that purpose, it is preferable to control the redox degree so as not to overreduce. When excessively reduced, MoO ₂ , metal Mo, metal Bi, and metal lanthanoid are formed. Therefore, by controlling the oxidation-reduction degree of the oxide catalyst to form a Bi-A-Mo-O composite oxide, the target product when the reaction is performed using the oxide catalyst according to the present embodiment. The yield is further improved.

^[Co 2+ ^-Fe 2+ -Mo-O composite oxide]
Moreover, the oxide catalyst according to the present embodiment contains Fe. Fe can increase the catalytic activity without reducing the selectivity of the target product, and is an essential element for industrially synthesizing the target product in the same manner as Mo and Bi. In the oxide catalyst according to this embodiment, the Fe content is preferably controlled within the above range.

Usually, in the production of an oxide catalyst, when firing in an oxidizing atmosphere containing oxygen, when the Fe content is increased, Fe ₂ O ₃ is generated, and a by-product such as CO and CO ₂ tends to increase, There is a problem that the selectivity of the target product is lowered. In this regard, the present inventors aim to suppress by-products such as Fe ₂ O ₃ in the production of oxide catalysts containing lanthanoid elements in addition to Mo, Bi, Fe, and Co, and an inert gas atmosphere In particular, a method for controlling the oxidation-reduction degree of the oxide catalyst and controlling the valence of Fe to 2 was found. By this control, the inventors succeeded in creating an oxide catalyst having a composition range having a larger Fe ratio than before, and found that the yield of the target product can be further increased. From this result, if it is divalent Fe, even if the atomic ratio of Fe to Mo12 atoms is 3 or more, it is dissolved in CoMoO ₄ , and a ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O is formed Became clear. By controlling the oxidation-reduction degree of the oxide catalyst in this way, substitutional solid solution of Fe in CoMoO ₄ can be made regardless of the composition. In the oxide catalyst, the composition ratio can be freely set and Co the crystals of 3 components ²⁺ -Fe ²⁺ -Mo-O can be produced. That is, in order to appropriately oxidize the oxide catalyst, the formation of a divalent iron compound in the oxide catalyst is promoted, and the ratio of Mo, Bi, Fe, Co, and lanthanoid element A is appropriately adjusted. Thus, by suppressing the production of the trivalent iron compound, it is possible to create an oxide catalyst in a new state in which Fe is dissolved in CoMoO ₄ even when the Fe ratio is large.

Fe in the three component crystals of Co ²⁺ -Fe ²⁺ -Mo-O and the lanthanoid element A in the Bi-A-Mo-O composite oxide described above oxidize and reduce each other, thereby providing a valence. Changes occur, gas phase oxygen uptake into the catalyst and lattice oxygen propagation in the catalyst are promoted, and unsaturated aldehydes can be obtained in high yields.

The oxide catalyst according to this embodiment includes Co. Co, like Mo, Bi, and Fe, is an essential element for industrially synthesizing the target product. In the oxide catalyst according to the present embodiment, Co forms a composite oxide CoMoO ₄ , and the CoMoO ₄ plays a role as a support for highly dispersing active species such as Bi—A—Mo—O and the like. It is presumed to play a role of taking oxygen from the phase and supplying it to Bi-A-Mo-O or the like. In order to obtain an unsaturated aldehyde in a high yield with an oxide catalyst containing Mo, Bi, Fe, Co and a lanthanoid element A, Co is compounded with Mo in the oxide catalyst, and the composite oxide CoMoO ₄ is formed. It is preferable to form. In the unsaturated aldehyde production, if a single oxide such as Co ₃ O ₄ or CoO is present, a side reaction may occur. Therefore, the formation of a single oxide such as Co ₃ O ₄ or CoO is reduced in the oxide catalyst. It is preferable to do.

The oxide catalyst according to the present embodiment preferably has a composition represented by the following composition formula (1).
_{Mo 12 Bi a Fe b Co c} A d B e C f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt,
A represents at least one lanthanoid element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, and europium,
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, and lead;
C represents at least one alkali element selected from the group consisting of cesium, rubidium, and potassium;
a to f indicate the atomic ratio of each element to Mo12 atom, and 1.5 ≦ a ≦ 6, 3 ≦ b ≦ 7, 2 ≦ c ≦ 8, 0.5 ≦ d ≦ 6, 0, 0.01 ≦ satisfy 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 represents at least one lanthanoid element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, and europium. When A is contained in the oxide catalyst, a Bi—A—Mo—O composite oxide can be formed, and the heat resistance tends to be further improved.

C represents at least one alkali element selected from the group consisting of cesium, rubidium and potassium. C is considered to exhibit a role of neutralizing acid sites such as MoO ₃ that have not been complexed in the oxide catalyst. Note that whether or not cesium and / or rubidium are contained does not affect the crystal structure of Fe—Co—Mo—O. In the composition represented by the composition formula (1), the atomic ratio f of these elements to Mo12 atoms relative to Mo12 atoms is preferably 0 ≦ f <2, more preferably 0.1 ≦ f ≦ 1.5, More preferably, 0.2 ≦ f ≦ 1.0. When the atomic ratio f is in the above numerical range, the activity tends to be higher.

  B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, and lead. B is considered to show a role of assisting oxygen uptake from the gas phase in the oxide catalyst. The atomic ratio e is preferably 0.01 ≦ e ≦ 2, more preferably 0.03 ≦ e ≦ 1, and further preferably 0.05 ≦ e ≦ 0.4. When the atomic ratio e of the alkali element is in the above numerical range, the catalytic activity of the oxide catalyst having the composition represented by the composition formula (1) tends to be more excellent. Further, when the atomic ratio e of the alkali element is 2 or less, the oxide catalyst is not easily made basic, and in the oxidation reaction of olefin or alcohol, the raw material olefin or alcohol is easily adsorbed by the catalyst, and the catalytic activity is increased. It tends to be better.

(2) [Crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O composite oxide]
In order to promote the formation of the ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O in the above-described oxide catalyst from the viewpoint of increasing the yield of unsaturated aldehyde, the divalent Fe in the oxide catalyst is promoted. The proportion of is important. In the oxide catalyst of the present embodiment, the ratio (atomic ratio) of divalent iron to divalent and trivalent iron, that is, the ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.3 or more and 0.9 or less. Preferably, it is 0.5 or more and 0.8 or less, More preferably, it is 0.6 or more and 0.8 or less. Hereinafter, the ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) will be described in more detail.

When an oxide containing Mo, Bi, Fe, and Co is measured by X-ray diffraction (XRD) in an X-ray diffraction angle range of 2θ = 5 ° to 60 °, the complex oxide (002) of Co and Mo is (002). ) The peak due to the X-ray diffraction angle (2θ) of the surface is shown at 26.40 °. When Fe is mixed in a complex oxide composed of Co and Mo in a solid solution, this peak shift occurs due to the difference in ionic radius between Co ²⁺ and Fe ²⁺ . Since Fe has a structure in which the solid solution is formed as a solid solution, a peak due to a composite oxide containing Co and Mo (hereinafter, also referred to as “composite oxide made of Fe, Co, and Mo”) The shift value is α °, and it appears at 26.40 ° −α ° (0 <α).

Although the detailed mechanism by which the peak due to the X-ray diffraction angle (2θ) of the (002) plane of the composite oxide composed of Fe, Co, and Mo shifts is not clear, the present inventors estimated as follows. ing. When the oxide catalyst is produced, when calcined in an air atmosphere containing oxygen, when the Fe atomic ratio b is 3 or less, the composite oxide composed of Fe, Co, and Mo is further trivalent. Fe is dissolved. Accordingly, it is estimated that the peak due to the composite oxide composed of Fe, Co, and Mo is slightly shifted as described above. This peak shift value (α °) is considered to be in the range of 0 ≦ α <0.05. On the other hand, when the Fe atomic ratio b to Mo atom 12 is greater than ₃ , a two-component oxide of Fe and Mo such as Fe ₂ Mo ₃ O ₁₂ tends to be formed. Therefore, further solid solution of trivalent Fe in a composite oxide composed of Fe, Co, and Mo does not occur, and the peak shift value (α °) is considered to be 0.05.

On the other hand, when the valence of Fe is bivalent, a peak shift occurs even in a composition having an Fe atomic ratio b to Mo atom 12 of more than 3, and the peak shift value (α °) is 0.05 ≦ α ≦ 0.25. It becomes. This is because a new crystal structure of a composite ternary system of Co ²⁺ -Fe ²⁺ -Mo-O is newly formed by further dissolving divalent Fe in a composite oxide composed of Co and Mo. It is thought that it was done. The reason why the ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O is formed in this way is that when Fe becomes divalent, the ionic radius of Fe becomes close to the ionic radius of divalent Co. It is presumed that substitutional solid solution with Co becomes possible. The ionic radius of divalent Co is 0.72０．７, the ionic radius of trivalent Fe is 0.64Å, and the ionic radius of divalent Fe is 0.74Å.

Moreover, when the atomic ratio b of Fe to Mo12 atoms is 3 ≦ b ≦ 7, the crystal structure of the Co ²⁺ —Fe ²⁺ —Mo—O composite oxide tends to be easily formed. Furthermore, when the atomic ratio b is within the above range, the crystal structure of the Co ²⁺ -Fe ²⁺ -Mo-O composite oxide can be easily formed, and the generation of CO _x (CO ₂ , CO, etc.) can be suppressed during the reaction. An oxide catalyst is obtained, and the selectivity of the target product tends to be higher. As a result, when such an oxide catalyst is used, the yield of unsaturated aldehyde tends to be improved.

The oxide catalyst according to the present embodiment preferably contains a composite oxide containing Co and Mo. In the X-ray diffraction of the oxide catalyst according to this embodiment, a composite containing at least Co and Mo is used. The X-ray diffraction angle (2θ) of the (002) plane of the oxide preferably exhibits a peak (maximum intensity) at 26.15 ° to 26.35 °. The range of the X-ray diffraction angle 2θ in which the peak (maximum intensity) due to the composite oxide containing Co and Mo in the oxide catalyst according to the present embodiment is more preferably 26.15 ° to 26.30. °, more preferably 26.20 ° to 26.30 °. The fact that the peak is in the above range indicates that a Co ²⁺ -Fe ²⁺ -Mo-O composite oxide is produced. When the Co ²⁺ -Fe ²⁺ -Mo-O composite oxide is generated, the selectivity of the target product and the yield of the unsaturated aldehyde tend to be further improved.

As described above, as a composite index of the ternary crystal structure Co ²⁺ -Fe ²⁺ -Mo-O composite oxide, the peak shift from the X-ray diffraction angle 2θ = 26.40 ° may be used as a reference. it can. Moreover, it can judge from a Mossbauer spectrum as a parameter | index of the bivalence of a Fe valence and a trivalence. As a more detailed measurement method using XRD and Mossbauer spectrum, the method described in Examples can be used. The oxide catalyst according to the present embodiment can be obtained by, for example, a manufacturing method described later.

[2] Catalyst [support]
The oxide catalyst of this embodiment may contain a support for supporting the above-described oxide. The inclusion of the support is preferable in that the oxide catalyst can be highly dispersed and the supported oxide catalyst can be provided with high wear resistance.

  Although it does not specifically limit as a support | carrier, For example, a silica, an alumina, a titania, a zirconia is mentioned. In general, silica is an inert carrier and is a preferred carrier in that it has a good binding action on the above-mentioned oxide catalyst without reducing selectivity for the target product compared to other carriers. . Further, the silica support is also preferable in that it can give higher wear resistance to the supported oxide catalyst. The content of the carrier with respect to the total mass of the catalyst is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and further preferably 40 to 60% by mass.

In the case of the catalyst used in the fluidized bed reactor, it is preferable to include 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. Further, the lower limit of the content of the carrier is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more with respect to the total mass of the catalyst. When the content is 80% by mass or less, the Co ²⁺ -Fe ²⁺ -Mo-O crystal structure is hardly affected, the apparent specific gravity can be adjusted, and the fluidity tends to be further improved. Moreover, when it uses as a catalyst which requires intensity | strength like a fluid bed reaction catalyst because content is 20 mass% or more, there exists a tendency for crushing resistance, abrasion resistance, etc. to improve more.

  When producing acrolein or methacrolein in a fixed bed reactor, when used as a tablet-molded catalyst, the oxide catalyst according to this embodiment may not contain a support. Further, when the oxide catalyst is molded by the extrusion molding method, the oxide catalyst according to the present embodiment may not include a carrier component, and an organic binder may be used instead of the carrier.

[3] [Production method of oxide catalyst]
The method for producing an oxide catalyst according to the present embodiment includes a mixing step of mixing a raw material containing Mo, Bi, Fe, Co and a lanthanoid element and an oxidizing agent and / or a reducing agent to obtain a raw material slurry,
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 firing step and the main firing 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 60% or more and less than 100%.

As described above, the present inventors do not use Fe and Mo alone and / or binary oxides, but dilute Fe into solid solutions in binary oxides of Co and Mo. Focusing on obtaining a Co ²⁺ -Fe ²⁺ -Mo-O composite oxide in which three components are complexed, the composition ratio and the preparation method were comprehensively studied.

Surprisingly, the inventors have set the valence of Fe so that a new crystal structure in which the three components of Co ²⁺ -Fe ²⁺ -Mo-O in the oxide catalyst after the main calcination are compatible is formed. By controlling the degree of oxidation-reduction so that Mo, Bi and lanthanoid elements form crystals of the composite oxide Bi-A-Mo-O, the raw material is olefin and / or alcohol. In the production of unsaturated aldehydes, it has been found that an oxide catalyst capable of producing unsaturated aldehydes in a high yield can be obtained by suppressing the production of carbon dioxide.

Simply increasing the Fe content does not cause complexation of the three components Co ²⁺ -Fe ²⁺ -Mo-O, but (a) a specific composition ratio, (b) a specific valence By using a new manufacturing technology that satisfies the three conditions of using Fe and (c) using a specific firing method, divalent Fe is dissolved in a binary composite oxide of Co and Mo. ^{A 2 +} -Fe2 ⁺ -Mo-O composite oxide can be obtained. In addition, by a new manufacturing technique that satisfies the above three conditions, two-component complex oxides such as Co—Mo—O and Fe—Mo—O, and simple oxides such as Fe ₂ O ₃ , MoO ₃ , and CoO are used. Generation is suppressed. Note that the Co ²⁺ -Fe ²⁺ -Mo-O composite oxide is formed because the X-ray diffraction angle (2θ) of the (002) plane of the composite oxide containing Co and Mo is 26.15 ° to It can be confirmed by having a peak at 26.35 °.

The oxide catalyst manufactured by the manufacturing method according to the present embodiment is included in the ternary crystal structure of the lanthanoid element A and Co ²⁺ -Fe ²⁺ -Mo-O in the Bi-A-Mo-O crystal. Fe becomes a redox couple with each other, the reoxidation rate is further improved, the activity is further increased, and the reaction further proceeds even under a low oxygen partial pressure. For this reason, the by-product of an oxygen addition compound can be suppressed as much as possible, and it becomes an oxide catalyst with a higher yield of unsaturated aldehyde.

  The method for producing an oxide catalyst according to the present embodiment obtains a raw material slurry by mixing a raw material constituting an oxide catalyst containing Mo, Bi, Fe, Co, and a lanthanoid element 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 for obtaining an oxide catalyst. Hereinafter, each step will be described in detail.

(1) Preparation of raw materials [mixing step]
In the mixing step, a raw material slurry is obtained by mixing a raw material constituting an oxide catalyst containing Mo, Bi, Fe, Co, and a lanthanoid element with an oxidizing agent and / or a reducing agent. In the finally obtained oxide catalyst, the Bi atomic ratio a to Mo12 atoms is 1.5 ≦ a ≦ 6, the Fe atomic ratio b is 3 ≦ b ≦ 7, and the Co atomic ratio c is 2 ≦. It is preferable to adjust the mixing ratio of each raw material so that b ≦ 8 and the atomic ratio d of the lanthanoid element is 0.5 ≦ a ≦ 6.

  The raw material of each metal element constituting the oxide catalyst is not particularly limited as long as it contains Mo, Bi, Fe, Co, and lanthanoid elements such as cerium, lanthanum, cerium, praseodymium, and neodymium. , Cesium, rubidium, potassium, nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, lead. 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 oxidation-reduction degree so that Bi-A-Mo-O crystals are formed by controlling the valence of Fe to be bivalent, combining Mo, Bi, and the lanthanoid element A, the above raw material mixture An oxidizing agent and / or a reducing agent is added to the slurry. Among these, it is preferable to use it together with a reducing agent and an oxidizing agent so that elements other than Fe are reduced and metal is 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, Polyhydric carboxylic acids, such as water-soluble polymers, such as polyethyleneglycol, polyvinyl alcohol, polyacrylic acid, polycarboxylic acid, polyacrylamide; 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 the mixing step, the raw materials used as each element source may contain the oxidizing agent and reducing agent from the beginning. For example, the raw material which comprises an oxide catalyst is used as nitrate, hydrochloride, ammonium salt, organic acid salt, and carbonate. Thus, when using the raw material containing an oxidizing agent, it is sufficient to add only a reducing agent to the raw material slurry separately. Moreover, when using the raw material containing a reducing agent, it is sufficient only to add an oxidizing agent separately to the raw material slurry.

  Although the addition amount of an oxidizing agent is not specifically limited, 0.5-50 mass% is preferable with respect to a metal oxide, 10-40 mass% is more preferable, 20-40 mass% is further more preferable. When the addition amount is in the above range, the uniformity of the degree of oxidation and reduction of the catalyst tends to be more excellent.

1-40 mass% is preferable with respect to a metal oxide, as for the addition amount of a reducing agent, 1-30 mass% is more preferable, and 3-20 mass% is further more preferable. When the addition amount is in the above range, the degree of oxidation and reduction tends to be more easily controlled. Moreover, by being 40 mass% or less, Fe is completely overreduced to bivalent, Mo is overreduced to MoO ₂ or metal Mo, Bi is overreduced to metal Bi, or a lanthanoid element is a metal. It tends to be able to suppress excessive reduction to lanthanoids.

  The method for preparing the raw slurry is not particularly limited as long as it is a commonly used method. For example, a solution in which an ammonium salt of Mo is dissolved in warm water and Bi, Ce, Fe, Co, and an alkali metal as nitrate are added to water or It can be prepared by mixing a solution dissolved in an aqueous nitric acid 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 of the catalyst tends to be more excellent.

  When the ammonium salt of Mo and the nitrates of other metals are mixed, precipitation occurs to form a slurry. Therefore, homogenizer treatment and aging may be appropriately performed on the raw slurry. The purpose of homogenizer treatment and aging is to pulverize the solids, promote the formation of oxide catalyst precursors, and make a finer and more uniform slurry. When the content of Bi is large, it is easy to form a slurry with a large amount of nitric acid and low dispersibility. Therefore, it is preferable to perform a homogenizer treatment and aging. When homogenizer treatment is performed, in order to pulverize the solid content to a smaller extent, the rotation speed of the homogenizer is preferably 5000 to 30000 rpm, and the treatment time is generally in the range of 5 minutes to 2 hours. Is preferred. When the slurry is aged, in order to obtain the target composite crystal, it is preferable to heat the slurry to a temperature higher than room temperature and keep the slurry medium in a liquid state. The aging time is not particularly limited, but is preferably 1 to 24 hours.

(2) [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, the composite oxide tends to be more easily formed.

(3) [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. This pre-baking is performed in an inert gas atmosphere. The purpose of pre-firing is removal of nitric acid remaining in the dried product, ammonium nitrate and other raw materials such as ammonium salt and ammonium nitrate produced from raw materials such as nitrate, etc., oxidizing agent, reducing agent, dispersed in water It is to gently burn organic substances such as a surfactant when the produced oxide is used as a raw material. When the dry product contains both an oxidizing agent and a reducing agent, it is preferable to use an oxide catalyst amount as small as possible to suppress heat generation, so that the oxidation and reduction can be controlled with high accuracy. It is preferable. Note that oxidation and reduction can be controlled 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, not only may there be a possibility of heat generation when the reducing agent decomposes, but it becomes difficult to accurately control the firing time for reduction. In the method for producing an oxide catalyst, calcination is performed in an inert gas atmosphere. Although it does not specifically limit as an inert gas used by this embodiment, For example, helium, argon, and nitrogen are mentioned. Among these, nitrogen is preferable from the economical aspect.

  An apparatus for performing the above-described preliminary firing and main firing described later is not particularly limited, and examples thereof include firing furnaces such as a rotary furnace, a tunnel furnace, and a muffle furnace.

Pre-baking is controlled so that the reduction rate is 60% or more and less than 100%. The reduction rate is defined by the following formula. 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 ratio of the calcined product is less than 60%, Fe in the catalyst after the main calcination tends to be trivalent. From the viewpoint of promoting the formation of crystals having a predetermined amount of divalent Fe after the main firing, the reduction rate is 60% or more and less than 100%, preferably 70% or more and less than 90%, more preferably 80% or more and less than 90%. It is. When the reduction rate reaches 100%, MoO ₂ and metal Bi are generated and tend to be overreduced.

  The reduction rate of the calcined product can be adjusted by the mass ratio of the oxidizing agent and the reducing agent in the raw slurry. The combination of the oxidizing agent and the reducing agent is not particularly limited. For example, a combination of hydrogen peroxide solution and tartaric acid, a combination of hydrogen peroxide solution and oxalic acid, a combination of hydrogen peroxide solution and ammonium polycarboxylate, nitric acid and A combination of hydrazine, a combination of nitric acid and ethylenediamine, and a combination of nitric acid and ethylenediaminetetraacetic acid.

  The pre-baking temperature is preferably 120 to 350 ° C, more preferably 150 to 350 ° C, and further preferably 200 to 350 ° C. By setting it to such a temperature, removal of nitric acid remaining in the dried body, ammonium nitrate produced from a raw material such as an ammonium salt and a raw material such as nitrate, an oxidizing agent, and a reducing agent, When using an oxide dispersed in water as a raw material, organic substances such as surfactants tend to be burned more gently.

The calcination time is preferably 0.1 to 24 hours, more preferably 1 to 12 hours, and further preferably 3 to 10 hours. In the case of a low temperature of 150 ° C. or lower, it is preferable to carry out temporary baking for a long time. When the temperature and / or time of calcination is within the above range, it tends to be suppressed from the growth of binary oxides of Co and Mo at the stage of calcination, and in the main calcination described later, Co ²⁺ − The crystal structure of Fe ²⁺ -Mo-O tends to be more easily generated.

  In the preliminary calcination, it is preferable that the rate of temperature increase is slow from the viewpoint of suppressing a rapid combustion reaction. In the manufacturing method of this embodiment, the obtained oxide catalyst 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. For this reason, in order to form a more homogeneous composite structure in the production of an oxide catalyst, the temperature is raised slowly, combustion and decomposition components such as nitric acid and organic substances are removed, and Fe is changed from trivalent to 2 It is preferable to reduce to a valence. 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.

[Main firing process]
In the step, the obtained calcined body is subjected to main calcination to obtain an oxide catalyst. The purpose of this firing is to facilitate the formation of the 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 temperature for the main baking is preferably higher than the temperature for the temporary baking from the viewpoint of generating Co ²⁺ -Fe ²⁺ -Mo-O crystals. The firing temperature for such firing is preferably 400 to 700 ° C., more preferably 400 to 650 ° C., and still more preferably, from the viewpoint of easy formation of a Co ²⁺ -Fe ²⁺ -Mo—O crystal structure. It is 450 degreeC-600 degreeC. When firing at such a temperature, the formation of Co ²⁺ -Fe ²⁺ -Mo-O crystals can be promoted by making the product of the firing temperature and the firing time appropriate. From this viewpoint, the main baking time is preferably 0.1 to 24 hours, more preferably 2 to 12 hours, and further preferably 3 to 10 hours. More specifically, from the viewpoint of making the firing temperature and firing time appropriate for generating the crystal structure, for a low temperature of 400 ° C. or lower, the main firing is performed for a long time, for example, about 24 to 72 hours. In the case of a high temperature of 600 ° C. or higher, from the viewpoint of preventing the surface activity of the resulting oxide catalyst from becoming too small and reducing the catalytic activity, it is possible to perform a main firing in a short time of 1 hour or less. preferable.

By performing all of the above steps, a complex Co ²⁺ -Fe ²⁺ -Mo-O ternary crystal structure is easily formed.

Whether or not a ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O is generated in the main baking step can be confirmed by performing an X-ray structural analysis of the oxide obtained after the main baking. When the X-ray structural analysis of the oxide catalyst is performed after the main calcination, if a ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O is generated, as described above, 26.40 ° -α A peak is observed at °. When an oxide crystal composed of Co and Mo is generated, a peak appears at 26.40 °. However, in the case of a ternary system of Co ²⁺ -Fe ²⁺ -Mo-O, this peak shifts. Generation of ternary crystals can be confirmed using the shift as an index.

Specifically, the magnitude of this shift (α °) is examined, and the X-ray diffraction angle of the composite oxide composed of Co and Mo having a peak at 26.40 ° is examined. In this embodiment, if the X-ray diffraction angle (2θ) of the (002) plane of the complex oxide containing Co and Mo shows a peak at 26.15 ° to 26.35 °, Co ²⁺ -Fe ^It is judged that a 2 ⁺ -Mo-O ternary crystal structure was formed. The valence of Fe is calculated from a Mossbauer spectrum.

[4] [Production method of unsaturated aldehyde]
The method for producing an unsaturated aldehyde according to the present embodiment uses the oxide catalyst, and a group consisting of at least one olefin selected from the group consisting of propylene and isobutylene and / or isobutanol, and t-butyl alcohol. A step of oxidizing at least one alcohol selected from the above. Although it does not specifically limit as an unsaturated aldehyde manufactured by this, For example, a methacrolein and acrolein are mentioned.

  The methacrolein or acrolein can be obtained, for example, by performing a gas phase catalytic oxidation reaction of isobutylene, propylene, isobutanol and t-butyl alcohol using the oxide catalyst of the present embodiment. In the gas phase catalytic oxidation reaction, for example, in the presence of the above-mentioned catalyst, the molecular oxygen concentration is 1 to 20% by volume with respect to 1 to 10% by volume of isobutylene, propylene, isobutanol and t-butyl alcohol. In addition, a raw material gas composed of a mixed gas obtained by adding a molecular oxygen-containing gas and a dilution gas to the catalyst layer in the fixed bed reactor under a temperature range of 250 to 450 ° C. and a pressure of atmospheric pressure to 5 atm. It can carry out by introduce | transducing under 400-4000 / hr [Normal temperature pressure (NTP) conditions]. The molar ratio of oxygen to isobutylene, propylene, isobutanol and t-butyl alcohol is preferably 1.0-2. From the viewpoint of controlling the outlet oxygen concentration of the reactor in order to improve the yield of unsaturated aldehyde. It is 0, More 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, air from an industrial point of view are preferred. 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. Regarding the mixing ratio of the molecular oxygen-containing gas and the diluent gas in the mixed gas, it is preferable that the following inequality condition is satisfied by the volume ratio. Furthermore, the concentration of molecular oxygen in the source gas is preferably 1 to 20% by volume.
0.01 <molecular oxygen-containing gas / (molecular oxygen-containing gas + dilution gas) <0.3

  Water vapor in the raw material gas may be included in order to prevent coking of the oxide catalyst, but on the other hand, it is diluted as much as possible to suppress by-production of carboxylic acids such as methacrylic acid, acetic acid and acrylic acid. It is preferable to lower the water vapor concentration in the gas. 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 in the range of 2 to 20% by volume, and 3 to 10% by volume. More preferably, it is used in the range of.

  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.

<Measurement of powder X-ray diffraction (XRD)>
XRD is measured by measuring the (111) plane and the (200) plane of the LaB ₆ compound as defined by National Institute of Standards & Technology as the standard reference material 660, and the measured values are 37.441 °, 43.43 °, respectively. It normalized so that it might become 506 degrees.

  Bruker D8 ADVANCE was used as the XRD measuring device. The XRD measurement conditions are: X-ray output: 40 kV-40 mA, divergent slit (DS): 0.3 °, Step width: 0.01 ° / step, counting time: 2.0 sec, measurement range: 2θ = 5 ° to The angle was 45 °.

<Measurement of iron valence>
Information on the valence of iron was obtained from Mossbauer spectroscopy (transmission method). The measurement conditions are shown below.
Measurement conditions of iron valence (1) Preparation of measurement sample: About 55 to 60 mg of a sample was measured as it was.
(2) Configuration and specifications of the apparatus: FIG. 6 shows the configuration and specifications of the iron valence measuring apparatus.
(3) Transition used for observation: Transition between ground state and lowest excited state of ⁵⁷ Fe
(Energy: 14.4 [keV])
(4) Measurement method: uniform acceleration mode, room temperature, normal pressure (5) Storage device: card type multi-channel analyzer
MCS mode 512 channel (6) source: ⁵⁷ Co / Rh matrix, 1.85 [GBq]
(7) Velocity axis calibration method: Pure iron has the following four peak center positions among the six magnetic splitting peaks of the spectrum at room temperature: x ₂ , x ₃ , x ₄ , x ₅ [channel] Obtained by the formula.
x0 [channel] = (x ₂ + x ₃ + x ₄ + x ₅ ) / 4
r [mm / s / (channel)] = 20.422 / {3.0835 (x ₅ −x ₂ ) +0.8385 (x ₄ −x ₃ )}

<Measurement method of reduction rate>
The reduction rate was measured using the following formula. The oxide catalyst was weighed in a beaker, 20 ml of 50% sulfuric acid was added, 180 ml of purified water was added, and the mixture was stirred for 60 minutes. Thereafter, titration with potassium permanganate was performed using an automatic potentiometric titrator AT-510 (Kyoto Electronics). The reduction rate was calculated from the amount of potassium permanganate consumed by oxidation of the oxide catalyst.
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.)

In Examples and Comparative Examples, the conversion rate, selectivity, and yield used to represent reaction results are defined by the following equations.
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]
50.5 g of molybdenum trioxide is added to a mixed solution of 81.5 g of ion-exchanged water and 120.5 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. In addition, 106.5% by weight of bismuth oxide aqueous dispersion having an average particle diameter of 51 nm, 266.5 g, 10% by weight of lanthanum oxide aqueous dispersion having an average particle diameter of 40 nm, 75.8 g of cobalt nitrate, and 15% by weight of average particles. To a solution obtained by mixing 59.0 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.51 g of a 10% by mass cesium hydroxide solution, 8.57 g of tartaric acid was added as a reducing agent to obtain a solution (solution B).

The raw material slurry obtained by mixing both liquid A and liquid B is stirred at room temperature for 2 h, then sent to a spray dryer and spray dried at an inlet temperature of 250 ° C. and an outlet temperature of about 130 ° C. to obtain a dried product. It was. The dried product was heated from room temperature to 210 ° C. at a rate of 1.16 ° C./min in a nitrogen gas atmosphere, held for 1 h, and then heated to 300 ° C. at a rate of 0.5 ° C./min. And the temporary baked body was obtained by hold | maintaining for 3 hours. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined body was heated up to 520 ° C. at a temperature rising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 3 hours to obtain the oxide catalyst of Example 1. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are shown in Table 3.

  For the reaction evaluation of the catalyst, 4.3 g of the oxide catalyst of Example 1 was charged in a jacketed SUS reaction tube with a diameter of 14 mm, isobutylene 8 vol%, oxygen 12.8 vol%, steam 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.

[Example 2]
50.1 g of molybdenum trioxide is added to a mixed solution of 80.8 g of ion-exchanged water and 119.5 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. Further, 104.3% by weight of an average particle diameter of 51 nm bismuth oxide aqueous dispersion 264.3 g, 10% by weight of an average particle diameter 20 nm cerium oxide aqueous dispersion 74.9 g, cobalt nitrate 25.6 g, 15% by weight of average particles A reducing agent was added to a solution obtained by mixing 58.5 g of an iron oxide aqueous dispersion having a diameter of 39 nm, 10% by mass of 8.7 g of a tin oxide aqueous dispersion having an average particle diameter of 20 nm, and 3.48 g of a 10% by mass cesium hydroxide liquid. As a result, 8.57 g of tartaric acid was added to obtain a solution (liquid B).

Using the liquid A and liquid B prepared as described above, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined product was heated up to 530 ° C. at a temperature raising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 3 hours to obtain an oxide catalyst of Example 2. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are 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]
55.5 g of molybdenum trioxide is added to a mixed solution of 89.5 g of ion-exchanged water and 132.4 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. In addition, 165.1 g of a bismuth oxide aqueous dispersion having an average particle diameter of 51 nm of 10% by mass, 14.7 g of praseodymium nitrate, 51.0 g of cobalt nitrate, 51.1 g of an iron oxide aqueous dispersion having an average particle diameter of 39 nm of 15% by mass, 17.5 g of tartaric acid as a reducing agent was added to a liquid obtained by mixing 3.85 g of 10 mass% cesium hydroxide liquid and 1.81 g of 10 mass% potassium hydroxide liquid to obtain a solution (liquid B).

Using the liquid A and liquid B prepared as described above, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined body was heated to 530 ° C. at a temperature rising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 4 hours to obtain an oxide catalyst of Example 3. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are shown in Table 3.

  As a reaction evaluation of the catalyst, 4.7 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]
Except having changed the usage-amount of tartaric acid into 11.6g, operation similar to Example 3 was performed and the oxide catalyst of Example 4 was obtained. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  As a catalyst reaction evaluation, 4.0 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]
53.9 g of molybdenum trioxide is added to a mixed solution of 87.0 g of ion-exchanged water and 128.7 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. Also, 108.0% by weight of bismuth oxide aqueous dispersion with an average particle diameter of 51 nm, 248.0 g, 10 mass% of lanthanum oxide aqueous dispersion with an average particle diameter of 40 nm, 41.2 g of cobalt nitrate, 15% by weight of average particles. 8.73 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 56.3 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 3.74 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

Using the liquid A and liquid B prepared as described above, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined body was heated up to 520 ° C. at a temperature rising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 3 hours to obtain an oxide catalyst of Example 5. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are shown in Table 3.

  As a reaction evaluation of the catalyst, 5.4 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]
67.0 g of ammonium heptamolybdate was dissolved in 200.9 g of hot water at about 90 ° C. (solution A). Further, 52.0 g of bismuth nitrate, 12.5 g of europium nitrate, 43.2 g of iron nitrate, 1.38 g of rubidium nitrate, 9.3 g of nickel nitrate, 5.6 g of magnesium nitrate, and 15.7 g of cobalt nitrate are mixed with 18% by mass of nitric acid. 21.5 g of ethylenediaminetetraacetic acid as a reducing agent was added to a solution obtained by dissolving in 19.3 g of an aqueous solution and mixed with 178.9 g of hot water at about 90 ° C. to obtain a solution (solution B).

Using the liquid A and liquid B prepared as described above, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined body was heated to 540 ° C. at a temperature rising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 5 hours to obtain an oxide catalyst of Example 6. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are shown in Table 3.

  As a catalyst reaction evaluation, 5.5 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]
The same operation as in Example 1 was performed except that tartaric acid, which is a reducing agent, was not added, and an oxide catalyst of Comparative Example 1 was obtained. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  As a reaction evaluation of the catalyst, 5.8 g of the oxide catalyst of Comparative Example 1 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 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. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  As a reaction evaluation of the catalyst, 5.5 g of the oxide catalyst of Comparative 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.

[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. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  As a reaction evaluation of the catalyst, 5.7 g of the oxide catalyst of Comparative Example 3 was charged 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]
In 218.0 g of hot water at about 90 ° C., 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 were dissolved (solution A). ). Further, 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 are dissolved in 38.4 g of an 18% by mass nitric acid aqueous solution, and heated at about 90 ° C. 126.2 g was added (Liquid B).

Both liquid A and liquid B were mixed and stirred and mixed at 95 ° C. for about 3 hours to obtain a raw material slurry. This raw material slurry was sent to a spray dryer and spray dried at an inlet temperature of 220 ° C. and an outlet temperature of about 170 ° C. to obtain a dried product. The dried body was heated to 260 ° C. at a temperature rising rate of 0.43 ° C./min and held for 4 hours to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined product was calcined at 500 ° C. for 6 hours in a nitrogen gas atmosphere to obtain an oxide catalyst of Comparative Example 4. Table 3 shows the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value and the powder X-ray diffraction measurement result of the obtained fired body.

  As a reaction evaluation of the catalyst, 5.9 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.

[Comparative Example 5]
Except having changed the usage-amount of tartaric acid into 5.4g, operation similar to Example 1 was performed and the oxide catalyst of the comparative example 5 was obtained. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  For the reaction evaluation of the catalyst, 4.8 g of the oxide catalyst of Comparative 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 7]
50.6 g of molybdenum trioxide is added to a mixed solution of 81.7 g of ion-exchanged water and 120.8 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. (Liquid A) was obtained. Further, 267.1 g of 10% by mass bismuth oxide aqueous dispersion having an average particle diameter of 51 nm, 71.6 g of 10% by mass lanthanum oxide aqueous dispersion having an average particle diameter of 40 nm, 25.8 g of cobalt nitrate, and 15% by mass of average particles 8.57 g of tartaric acid as a reducing agent was added to a solution obtained by mixing 59.1 g of an iron oxide aqueous dispersion having a diameter of 39 nm and 1.32 g of a 10% by mass cesium hydroxide solution to obtain a solution (solution B).

Using the liquid A and liquid B prepared as described above, the same operation as in Example 1 was performed to obtain a temporarily fired body. Table 3 shows the reduction rate of this temporarily fired body. The obtained calcined body was heated up to 520 ° C. at a temperature rising rate of 3.67 ° C./min in a nitrogen gas atmosphere, and was calcined by holding for 3 hours to obtain an oxide catalyst of Example 7. . The composition of the obtained oxide catalyst is shown in Table 2, and the value of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) and the measurement result of powder X-ray diffraction of the fired body are shown in Table 3.

  For the reaction evaluation of the catalyst, 4.7 g of the oxide catalyst of Example 7 was charged in a jacketed SUS reaction tube with a diameter of 14 mm, and at a reaction temperature of 430 ° C., 8% by volume propylene, 12.8% by volume oxygen, and 3. Acrolein synthesis reaction was performed by aeration of a mixed gas consisting of 0 vol% and nitrogen volume 76.2% at a flow rate of 120 mL / min (NTP). The reaction evaluation results are shown in Table 5.

[Comparative Example 6]
An oxide catalyst of Comparative Example 6 was obtained in the same manner as in Example 7 except that the preliminary firing and the final firing were performed in an air atmosphere. Table 3 shows the reduction rate of the pre-fired body, the Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) value of the fired body, and the measurement results of powder X-ray diffraction.

  As a catalyst reaction evaluation, 5.8 g of the oxide catalyst of Comparative Example 6 was charged into 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.

<X-ray diffraction peaks of the oxide catalysts obtained in Example 1, Comparative Example 1 and Comparative Example 2>
The X-ray diffraction peaks of the oxide catalysts obtained in Example 1, Comparative Example 1, and Comparative Example 2 are shown in FIG. FIG. 2 shows an enlarged view of the range of 2θ = 25 to 27 ° of the X-ray diffraction peak in FIG. 1 and 2, the X-ray diffraction angle (2θ) of the (002) plane of the complex oxide of cobalt and molybdenum in the X-ray diffraction of the oxide obtained in Example 1 is 26.26 °. It was found to show a peak. The X-ray diffraction angle (2θ) of the (002) plane of the complex oxide of cobalt and molybdenum in Example 1 is shifted from 26.40 ° to 26.26 °. That is, in the oxide catalyst obtained in Example 1, divalent Fe was further dissolved in the composite oxide composed of Co and Mo, so that the composite Co ²⁺ -Fe ²⁺ -Mo-O was mixed. It is thought that a new ternary crystal structure was newly formed.

On the other hand, in the X-ray diffraction of the oxide catalyst obtained in Comparative Example 1, the X-ray diffraction angle (2θ) of the (002) plane of the composite oxide composed of Co and Mo both peaks at 26.40 °. I found out. That is, in the oxide catalyst obtained in Comparative Example 1, it is considered that a new ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O was not formed.

On the other hand, in the X-ray diffraction of the oxide catalyst obtained in Comparative Example 1, the X-ray diffraction angle (2θ) of the (002) plane of the composite oxide composed of Co and Mo both peaks at 26.40 °. It was found that a peak of Fe ₂ Mo ₃ O ₁₂ which is a trivalent iron compound was formed. That is, in the oxide catalyst obtained in Comparative Example 1, it is considered that a new ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O was not formed and iron was not reduced.

On the other hand, in the X-ray diffraction of the oxide catalyst obtained in Comparative Example 2, the (002) plane X-ray diffraction angle (2θ) of the composite oxide composed of Co and Mo shows a peak at 26.14 °. From the fact that MoO ₂ and metal Bi were produced, it was found that they were overreduced. That is, in the oxide catalyst obtained in Comparative Example 1, it is considered that a new ternary crystal structure of Co ²⁺ -Fe ²⁺ -Mo-O was not formed.

<Mossbauer spectrum of the oxide catalyst obtained in Example 1, Comparative Example 1 and Comparative Example 2>
FIG. 3 shows the Mossbauer spectrum of the oxide catalyst obtained in Example 1, FIG. 4 shows the Mossbauer spectrum of the oxide catalyst obtained in Comparative Example 1, and the oxide catalyst obtained in Comparative Example 2 The Mossbauer spectrum is shown in FIG. In the figure, δ is an isomer shift, Δ is a quadrupole split, and H is an internal magnetic field.
From FIG. 3, the oxide catalyst obtained in Example 1 has a divalent iron ratio of 75%, a trivalent iron ratio of 25%, and Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ). The ratio was found to be 0.75.
From FIG. 4, the oxide catalyst obtained in Comparative Example 1 has a divalent iron ratio of 0%, a trivalent iron ratio of 100%, and Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ). The ratio was found to be zero.
From FIG. 5, the oxide catalyst obtained in Comparative Example 2 has a ratio of divalent iron of 93%, a ratio of trivalent iron of 7%, and Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ). The ratio was found to be 0.93.

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

Claims (6)

Contains molybdenum, bismuth, iron, cobalt and lanthanoid elements,
The ratio of Fe ²⁺ / (Fe ²⁺ + Fe ³⁺ ) is 0.3 or more and 0.9 or less,
An oxide catalyst for producing an unsaturated aldehyde using olefin and / or alcohol as a raw material .   The atomic ratio a of bismuth to 12 atoms of molybdenum is 1.5 ≦ a ≦ 6, the atomic ratio b of iron is 3 ≦ b ≦ 7, and the atomic ratio c of cobalt is 2 ≦ The oxide catalyst according to claim 1, wherein c ≦ 8 and the atomic ratio d of the lanthanoid element is 0.5 ≦ d ≦ 6. The oxide catalyst of Claim 1 or 2 which has a composition represented by the following compositional formula (1).
_{Mo 12 Bi a Fe b Co c} A d B e C f O g (1)
(In the formula (1), Mo represents molybdenum, Bi represents bismuth, Fe represents iron, Co represents cobalt,
A represents at least one lanthanoid element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, and europium,
B represents at least one element selected from the group consisting of nickel, manganese, copper, zinc, magnesium, calcium, strontium, barium, tin, and lead;
C represents at least one alkali element selected from the group consisting of cesium, rubidium, and potassium;
a to f indicate the atomic ratio of each element to the Mo12 atom, 1.5 ≦ a ≦ 6, 3 ≦ b ≦ 7, 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. ) Containing a composite oxide containing the cobalt and the molybdenum;
The X-ray diffraction angle (2θ) of the (002) plane of the composite oxide containing cobalt and molybdenum shows a peak (maximum intensity) at 26.15 ° to 26.35 ° in X-ray diffraction. The oxide catalyst according to any one of 1 to 3. A method for producing an oxide catalyst according to any one of claims 1 to 4,
A mixing step of mixing a raw material containing molybdenum, bismuth, iron, cobalt and a lanthanoid element and an oxidizing agent and / or 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 firing step, the reduction rate of the temporary fired body is controlled to be 60% or more and less than 100%.   From the group consisting of at least one olefin selected from the group consisting of propylene and isobutylene and / or isobutanol and t-butyl alcohol using the oxide catalyst according to any one of claims 1 to 4. A method for producing an unsaturated aldehyde comprising a step of oxidizing at least one selected alcohol.