JP2011115681A - Catalyst for synthesizing unsaturated aldehyde and unsaturated carboxylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for synthesizing unsaturated aldehyde and unsaturated carboxylic acid excellent in catalytic activity and selectivity. <P>SOLUTION: The catalyst for synthesizing unsaturated aldehyde and unsaturated carboxylic acid is made of a particle of a composite oxide containing at least molybdenum, iron and cobalt, wherein the particle satisfies the following formulas (i) B/A≤0.8 and (ii) D/C≤0.7. In the formulas, A presents Fe/Mo atomic ratio in bulk composition of the particle, B presents Fe/Mo atomic ratio in surface composition, C presents Co/Mo atomic ratio in bulk composition of the particle and D presents Co/Mo atomic ratio in surface composition of the particle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an unsaturated aldehyde and unsaturated carboxylic acid synthesis catalyst. More specifically, propylene, isobutylene, tertiary butanol (hereinafter abbreviated as TBA) or methyl tertiary butyl ether (hereinafter abbreviated as MTBE) is subjected to gas phase catalytic oxidation with molecular oxygen, respectively. It relates to a catalyst used in the synthesis of the corresponding unsaturated aldehyde and unsaturated carboxylic acid.

  Conventionally, a plurality of elements such as molybdenum and iron are used as catalysts used in the production of unsaturated aldehydes and unsaturated carboxylic acids corresponding to gas phase catalytic oxidation of propylene, isobutylene, TBA or MTBE at high temperatures. A composite oxide containing is used as a catalyst component. Many proposals have been made on such a catalyst and its production method. For example, in Patent Document 1, an aqueous slurry containing a predetermined catalyst component is heat-treated, and the resulting slurry is dried and fired to obtain a composite oxidation. When obtaining a product, the peak intensity attributed to the crystal phase of antimony trioxide in the X-ray diffraction image of the solid matter in the slurry after heat treatment is set to 20% or less of the peak intensity attributed to cobalt molybdate. It is disclosed. Further, Patent Document 2 discloses a method in which particles of an aqueous slurry containing a catalyst component are atomized and then made into spherical particles using a spray dryer and fired. Patent Document 3 discloses a method in which a raw material salt solution containing a catalyst component is subjected to a heat treatment to obtain a catalyst precursor powder containing 1% to 5% of a sparkling raw material, which is molded and fired.

JP-A-9-57106 JP 10-258233 A JP 2001-96162 A

However, the catalyst obtained by the conventional method does not necessarily have sufficient catalytic activity, and the reaction rate of raw materials such as isobutylene may be low. Further, the selectivity is not always sufficient, and a by-product may be generated. Since these problems affect the yields of unsaturated aldehydes and unsaturated carboxylic acids, further improvements in performance are desired.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the catalyst for unsaturated aldehyde and unsaturated carboxylic acid synthesis | combination excellent in catalyst activity and selectivity.

As a result of intensive studies, the present inventors have determined that the composite oxide particles containing at least molybdenum, iron and cobalt have the same bulk composition, but the ratio of molybdenum, iron and cobalt on the particle surface differs depending on the production conditions. Was found to affect the catalyst performance of the catalyst using the particles, and the present invention was completed based on such findings.
The present invention is a catalyst for synthesizing unsaturated aldehydes and unsaturated carboxylic acids, comprising particles of a composite oxide containing at least molybdenum, iron and cobalt, and the particles satisfy the following formulas (i) and (ii).
B / A ≦ 0.8 (i)
D / C ≦ 0.7 (ii)
[In the formula, A represents the Fe / Mo atomic ratio in the bulk composition of the particles, B represents the Fe / Mo atomic ratio in the surface composition of the particles, and C represents the Co / Mo atomic ratio in the bulk composition of the particles. D represents the Co / Mo atomic ratio in the surface composition of the particles. ]

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst for unsaturated aldehyde and unsaturated carboxylic acid synthesis | combination excellent in catalyst activity and selectivity can be provided.

The unsaturated aldehyde and unsaturated carboxylic acid synthesis catalyst of the present invention (hereinafter referred to as the catalyst of the present invention) comprises composite oxide particles containing at least molybdenum, iron and cobalt, and the particles are represented by the following formula (i): And (ii) is satisfied.
B / A ≦ 0.8 (i)
D / C ≦ 0.7 (ii)
[In the formula, A represents the Fe / Mo atomic ratio in the bulk composition of the particles, B represents the Fe / Mo atomic ratio in the surface composition of the particles, and C represents the Co / Mo atomic ratio in the bulk composition of the particles. D represents the Co / Mo atomic ratio in the surface composition of the particles. ]

In the present invention, the “bulk composition of particles” refers to the composition (atomic ratio) of all elements constituting the particle, that is, the composition (atomic ratio) of the composite oxide. The bulk composition is obtained by performing elemental analysis on the solution in which the particles are dissolved by ICP (inductively coupled radio frequency plasma) emission spectrometry, atomic absorption spectrometry, or the like. It can also be calculated from the amount of raw material used for the production of the particles.
The “particle surface composition” refers to the composition (atomic ratio) of the elements constituting the surface layer (exposed surface) of the particle. This surface composition is calculated | required by performing the X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy) analysis which uses Al-k alpha ray as an X-ray source about the said particle | grain.

In formula (i), B / A is the ratio of the Fe / Mo atomic ratio in the particle surface composition to the Fe / Mo atomic ratio in the bulk composition of the particles. B / A is 0.8 or less, and preferably 0.75 or less. When B / A exceeds 0.8, the catalyst activity is reduced. The lower limit of B / A is not particularly limited, but is preferably 0.3 or more, and more preferably 0.4 or more. When B / A is less than 0.3, the catalyst activity is unnecessarily improved, and there is a risk that problems such as a decrease in selectivity of the target product may occur during the synthesis of unsaturated aldehydes and unsaturated carboxylic acids.
In formula (ii), D / C is the ratio of the Co / Mo atomic ratio in the particle surface composition to the Co / Mo atomic ratio in the bulk composition of the particles. D / C is 0.7 or less. When D / C exceeds 0.7, the selectivity is lowered, and consequently the yield of the target product (particularly unsaturated aldehyde) is lowered. The lower limit of D / C is not particularly limited, but is preferably 0.3 or more. If D / C is less than 0.3, thermal stability may be disadvantageous.

The bulk composition of the particles only needs to include at least molybdenum, iron, and cobalt, and may include elements other than these three types as a catalyst component. A preferable bulk composition is a composition represented by the following formula (1).
_{Mo a Bi b Fe c M d} X e Y f Z g Si h O i ... (1)
[Wherein, Mo, Bi, Fe, Si and O represent molybdenum, bismuth, iron, silicon and oxygen, respectively. M represents cobalt or cobalt and nickel. X represents at least one element selected from chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum and zinc. Y represents at least one element selected from phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony and titanium. Z represents at least one element selected from lithium, sodium, potassium, rubidium, cesium and thallium. a, b, c, d, e, f, g, h, and i represent atomic ratios of the respective elements. When a = 12, b = 0.01-3, c = 0.01-5, d = 1 -12, e = 0 to 8, f = 0 to 5, g = 0.001 to 2, and h = 0 to 20, and i is an oxygen atomic ratio necessary to satisfy the valence of each component. is there. ]

  When M represents cobalt and nickel, that is, when the composite oxide contains both cobalt and nickel, d represents their total atomic ratio. When X contains two or more elements, e represents the total atomic ratio of the two or more elements, and the same applies to f in Y and g in Z.

Composite oxide particles (hereinafter referred to as composite oxide particles) can be produced, for example, by preparing an aqueous slurry containing at least molybdenum, iron, and cobalt, heating the aqueous slurry, and then drying and firing. . At this time, by adjusting the heat treatment conditions, composite oxide particles satisfying the above formulas (i) and (ii) can be obtained. Specifically, the composite oxide particles can be obtained by performing the heat treatment at a temperature of 80 ° C. or higher and 110 ° C. or lower for a predetermined time.
Hereinafter, the method for producing composite oxide particles will be described in more detail.

First, an aqueous slurry containing a catalyst component corresponding to the bulk composition of the composite oxide particles to be obtained is prepared. The catalyst component contains at least molybdenum, iron, and cobalt, and may optionally contain an element as shown in the above formula (1).
As a method for producing an aqueous slurry containing each catalyst component, it is not necessary to be limited to a special method, and as long as there is no significant uneven distribution of components, a conventionally well-known evaporation-drying method, precipitation method, oxide Various methods such as a mixing method can be used.
For example, it can be prepared by dissolving or suspending the required amount of the raw material of each catalyst component in an aqueous medium such as water.
As raw materials for the catalyst component, oxides, sulfates, nitrates, carbonates, hydroxides, ammonium salts, halides, and the like of each element can be used. Examples of the molybdenum raw material include ammonium paramolybdate and molybdenum trioxide. Examples of the bismuth raw material that can be used include bismuth trioxide, bismuth nitrate, bismuth carbonate, and bismuth hydroxide. As an iron raw material, ferric nitrate, ferric chloride, etc. can be used, for example. As the cobalt raw material, for example, cobalt nitrate, cobalt hydroxide, cobalt oxide, cobalt chloride and the like can be used.
The raw material of the catalyst component may be one kind for each element or two or more kinds may be used in combination. In addition, a raw material insoluble in water such as bismuth nitrate may be dissolved in an aqueous solution of an acid such as nitric acid in advance.

Next, the aqueous slurry is heat-treated.
The heat treatment temperature is 80 ° C. or higher and 110 ° C. or lower, and preferably 85 ° C. or higher and 105 ° C. or lower. Within this temperature range, the higher the heat treatment temperature, the smaller the B / A value and the higher the D / C value.
On the other hand, when the heat treatment temperature is less than 80 ° C., it is difficult to make the B / A value 0.8 or less, and the effect of the present invention cannot be sufficiently obtained. This is presumably because the catalyst structure is difficult to be stabilized and therefore the catalyst performance is hardly improved. When the heat treatment temperature exceeds 110 ° C., it is difficult to make the D / C value 0.7 or less, and the effect of the present invention cannot be obtained sufficiently. In addition, the evaporation of water is large, handling is complicated, and it is extremely disadvantageous in terms of economy and operability.
The heat treatment time may be appropriately set in consideration of desired B / A and D / C values and desired properties (specific gravity, viscosity, etc.) of the aqueous slurry after the heat treatment. From the viewpoint of improving the catalyst performance, the heat treatment is usually carried out for 30 minutes or more, and the upper limit is appropriately set within the range in which the aqueous slurry maintains a slurry state after the heat treatment, but the values of B / A and D / C Is preferably 2 hours or longer and 8 hours or shorter, more preferably 2.5 hours or longer and 6 hours or shorter. Within this range, the longer the heat treatment time, the smaller the value of B / A and the larger the value of D / C.
The specific gravity of the aqueous slurry after the heat treatment is preferably 1.3 g / mL or more and 1.8 g / mL or less. When the specific gravity is less than 1.3 g / mL, the processing time becomes long in the subsequent drying step, and when it exceeds 1.8 g / mL, handling is difficult.
Further, the viscosity of the aqueous slurry after the heat treatment is preferably 100 mPa · s or more, and more preferably 300 mPa · s or more. The viscosity is preferably 3000 mPa · s or less. When the viscosity is less than 100 mPa · s, the drying time in the drying step is long, which is disadvantageous in terms of economy. When it exceeds 3000 mPa · s, handling of the slurry is difficult and disadvantageous in terms of operability.

Next, the aqueous slurry after the heat treatment is dried to obtain a granular dried product (hereinafter referred to as dry particles). The target composite oxide particles are obtained by firing the dried particles.
As a drying method, various methods can be used, and examples thereof include an evaporation to dryness method, a spray drying method, a drum drying method, and an airflow drying method. The model of the dryer used for drying, the temperature at the time of drying, etc. are not specifically limited, The dried material according to the objective can be obtained by changing drying conditions suitably. Among these, it is preferable to use a spray drying method because the average particle diameter of the dried particles and thus the obtained composite oxide particles can be easily controlled.
There is no limitation in particular in drying conditions, A well-known condition can be applied and it is normally performed at the temperature of 150-300 degreeC.
There are no particular limitations on the firing conditions as well, and known conditions can be applied, usually at 200 to 550 ° C. The calcination time is appropriately selected depending on the target catalyst. Firing may be performed a plurality of times.
In this invention, 20-150 micrometers is preferable and, as for the average particle diameter of the said composite oxide particle, 40-110 micrometers is more preferable. The average diameter is a value (average median diameter) measured by a laser diffraction / scattering method, and can be measured, for example, using a laser diffraction particle size distribution analyzer SALD-7000 manufactured by Shimadzu Corporation.

The composite oxide particles can be used as a granular catalyst as it is. In this case, it is preferably used in a fluidized bed.
The composite oxide particles may be molded and used as a molded body.
As a method for molding the composite oxide particles, known molding methods such as pressure molding, tablet molding, mold molding, extrusion molding, and rolling granulation can be applied.
When molding, known additives may be added as long as the effects of the present invention are not impaired. Examples of the additive include organic compounds such as polyvinyl alcohol, carboxymethyl cellulose, polyvinyl alcohol, and carboxymethyl cellulose; inorganic compounds such as graphite and diatomaceous earth; inorganic fibers such as glass fiber, ceramic fiber, and carbon fiber.
The shape of the molded body is not particularly limited, and may be any shape such as a columnar shape, a ring shape, a spherical shape, an indefinite shape, or the like.
The composite oxide particles may be supported on a carrier and used as a support.
Examples of the carrier include silica, alumina, silica-alumina, magnesia, titania, silicon carbide and the like.
The molded body or the support is preferably used on a fixed bed.

The catalyst of the present invention has high catalytic activity, and contributes to an improvement in the reaction rate when propylene, isobutylene, TBA or MTBE is subjected to gas phase catalytic oxidation using molecular oxygen. Moreover, selectivity is high and the selectivity of the unsaturated aldehyde and unsaturated carboxylic acid to produce | generate is also high. Therefore, the reacted propylene, isobutylene, TBA or MTBE efficiently becomes the corresponding unsaturated aldehyde and unsaturated carboxylic acid. Therefore, unsaturated aldehydes and unsaturated carboxylic acids can be obtained in high yields by using the catalyst of the present invention.
Although it is not clear why B / A and D / C can be obtained in a high yield by setting the B / A and D / C to be within a predetermined range, the values of B / A and D / C are small. In the particle structure of the catalyst, there is little exposure of Fe and Co to the particle surface. Therefore, it can be considered that the structural stability of the catalyst particles is improved by the catalyst particles having such a structure.

The production of unsaturated aldehydes and unsaturated carboxylic acids using the catalyst of the present invention is carried out, for example, by vapor phase catalytic oxidation of propylene, isobutylene, TBA or MTBE with molecular oxygen in the presence of the catalyst of the present invention. it can. Thereby, the unsaturated aldehyde and unsaturated carboxylic acid corresponding to a raw material (propylene, isobutylene, TBA, or MTBE) are obtained. For example, when isobutylene is used as a raw material, methacrolein and methacrylic acid are obtained.
At this time, the catalyst of the present invention may be diluted with a support. Examples of the carrier are the same as those mentioned as the carrier of the carrier.
The ratio (molar ratio) between the raw material and molecular oxygen in the gas phase catalytic oxidation reaction is preferably in the range of raw material: molecular oxygen = 1: 0.5 to 1: 3.
The gas phase catalytic oxidation can be carried out by a known method except that the catalyst of the present invention is used. For example, the gas phase catalytic oxidation can be carried out by contacting a raw material gas containing a raw material and molecular oxygen with the catalyst.
The raw material propylene, isobutylene, TBA or MTBE is preferably diluted with an inert gas such as nitrogen gas, carbon dioxide gas or rare gas. Further, if necessary, the raw material gas may contain water vapor. The concentration of the raw material in the raw material gas is preferably about 1 to 10% by volume.
As the molecular oxygen source, pure oxygen gas may be used, but industrially, air is advantageous.
The reaction pressure is from normal pressure to several atmospheres. The reaction temperature is preferably in the range of 300 to 450 ° C.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the following examples and comparative examples, “parts” means parts by mass.
Reaction rate of raw material (isobutylene) used, selectivity of methacrolein (hereinafter abbreviated as MAL) and methacrylic acid (hereinafter abbreviated as MAA) generated by gas phase catalytic oxidation reaction, total of MAL and MAA The yield was calculated by the following formula. Reaction test analysis (measurement of the number of moles of reacted raw materials and the number of moles of MAL and MAA produced) was performed by gas chromatography.

In Examples and Comparative Examples, the specific gravity (g / mL) of the slurry is obtained by sampling a part of the slurry, measuring the volume (mL) and the mass (g) at a slurry temperature of 20 ° C., and dividing the mass by the volume. Calculated.
The viscosity (mPa · s) of the slurry was measured using a B-type viscometer after sampling a part of the slurry, setting the slurry temperature to 20 ° C., and sufficiently stirring so that the solid content does not separate.
The average particle diameter (average median diameter) of the composite oxide particles was measured using a particle size distribution analyzer SALD-7000 manufactured by Shimadzu Corporation.
The Fe / Mo atomic ratio and Co / Mo atomic ratio in the bulk composition of composite oxide particles are determined by quantifying the amount of catalyst components in a solution of composite oxide particles dissolved in hydrochloric acid by ICP emission spectrometry and atomic absorption spectrometry. Asked.
Regarding the surface composition of the composite oxide particles, first, using an X-ray photoelectron spectrometer (ESCALAB220iXL manufactured by VG), measurement was performed using Al-kα rays as an X-ray source, and an XPS spectrum obtained by the measurement was obtained. First, the peak area intensity of Mo3d, the peak area intensity of Fe2p3, and the peak area intensity of Co2p3 are calculated, and then the ratio is obtained after correcting each peak area intensity by the relative sensitivity factor specific to the apparatus. By the procedure, the Fe / Mo atomic ratio and the Co / Mo atomic ratio in the surface composition were determined.

[Example 1]
To 2000 parts of pure water at 60 ° C., 500 parts of ammonium paramolybdate, 12.4 parts of ammonium paratungstate, 23.0 parts of cesium nitrate, 27.4 parts of antimony trioxide and 33.0 parts of bismuth trioxide are added. Stirred (Liquid A).
Separately from this, 1000 parts of pure water at room temperature, 209.8 parts of ferric nitrate, 75.5 parts of nickel nitrate, 453.3 parts of cobalt nitrate, 31.3 parts of lead nitrate and 5.6% of 85% phosphoric acid. Parts were added sequentially and dissolved (Liquid B).
After mixing liquid A and liquid B to obtain a slurry, heat treatment was performed at 95 ° C. for 3 hours with stirring. A part of the slurry-like material after the heat treatment was collected and measured for specific gravity and viscosity at a slurry temperature of 20 ° C. As a result, the specific gravity was 1.4 g / mL and the viscosity was 470 mPa · s.
Subsequently, the slurry was dried with a rotary disk spray dryer while controlling the temperature at the hot air inlet at 220 ° C. and the temperature at the outlet at 170 ° C. The obtained dried particles were fired at 300 ° C. for 1 hour in an air atmosphere, and further fired at 500 ° C. for 6 hours in an air atmosphere.
Of the bulk composition of the composite oxide particles thus obtained, the composition of elements other than oxygen is
It was _{Mo 12 Bi 0.6 Fe 2.2 Sb 0.8} Ni 1.1 Co 6.6 Pb 0.4 P 0.2 W 0.2 Cs 0.5. In addition, X-ray photoelectron spectroscopic analysis of the composite oxide particles was performed to determine the Fe / Mo atomic ratio and Co / Mo atomic ratio in the surface composition, and from these results, the values of B / A and D / C were determined. As a result, B / A was 0.72 and D / C was 0.49.

The obtained composite oxide particles were pressure-molded to obtain a ring-shaped molded product (dimensions: outer diameter 5 mm, inner diameter 2 mm, height 4 mm).
The molded product is filled in a stainless steel reaction tube, and a raw material gas of 5% isobutylene, 12% molecular oxygen, 10% water vapor and 73% nitrogen (both volume%) is supplied, and the contact time is 3 at normal pressure. The reaction was carried out for 6 seconds at a reaction temperature of 340 ° C., and isobutylene was vapor-phase contact oxidized with molecular oxygen.
As a result, the reaction rate of isobutylene was 98.5%, the selectivity of MAL was 92.5%, the selectivity of MAA was 2.9%, and the total yield was 94.0%.

[Example 2]
In the same manner as in Example 1, a slurry was obtained by mixing the liquid A and the liquid B, and the obtained slurry was heat-treated at 105 ° C. for 3 hours with stirring. A part of the slurry-like material after the heat treatment was collected and measured for specific gravity and viscosity at a slurry temperature of 20 ° C. As a result, the specific gravity was 1.7 g / mL and the viscosity was 2750 mPa · s.
Subsequently, the slurry was spray-dried in the same manner as in Example 1 and fired to obtain composite oxide particles. With respect to the composite oxide particles, the Fe / Mo atomic ratio and the Co / Mo atomic ratio were determined in the same manner as in Example 1. As a result, B / A was 0.53 and D / C was 0.69. .
The composite oxide particles were formed into a molded product in the same manner as in Example 1, and the reaction was performed using the molded product in the same manner as in Example 1 using the same raw material mixed gas. As a result, the reaction rate of isobutylene was 99.0%, the selectivity of MAL was 91.3%, the selectivity of MAA was 2.7%, and the total yield was 93.1%.

[Comparative Example 1]
In the same manner as in Example 1, a slurry-like product obtained by mixing the liquid A and the solution B was obtained. A portion of the obtained slurry-like product was collected without performing heat treatment, and the specific gravity at a slurry temperature of 20 ° C. When the viscosity was measured, the specific gravity was 1.25 g / mL, and the viscosity was 35 mPa · s.
Subsequently, the slurry was spray-dried in the same manner as in Example 1 and fired to obtain composite oxide particles. With respect to the composite oxide particles, the Fe / Mo atomic ratio and the Co / Mo atomic ratio were determined in the same manner as in Example 1. As a result, B / A was 0.95 and D / C was 0.36. .
The composite oxide particles were formed into a molded product in the same manner as in Example 1, and the reaction was performed using the molded product in the same manner as in Example 1 using the same raw material mixed gas. As a result, the reaction rate of isobutylene was 96.3%, the selectivity of MAL was 91.4%, the selectivity of MAA was 0.9%, and the total yield was 88.9%.

[Comparative Example 2]
In the same manner as in Example 1, a slurry-like product obtained by mixing the liquid A and the solution B was obtained, and the obtained slurry-like product was heat-treated at 115 ° C. for 4 hours with stirring. A part of the slurry-like material after the heat treatment was collected and measured for specific gravity and viscosity at a slurry temperature of 20 ° C. As a result, the specific gravity was 1.82 g / mL and the viscosity was 3050 mPa · s.
Subsequently, the slurry was spray-dried in the same manner as in Example 1 and fired to obtain composite oxide particles. With respect to the composite oxide particles, the Fe / Mo atomic ratio and the Co / Mo atomic ratio were determined in the same manner as in Example 1. As a result, B / A was 0.57 and D / C was 0.81. .
The composite oxide particles were formed into a molded product in the same manner as in Example 1, and the reaction was performed using the molded product in the same manner as in Example 1 using the same raw material mixed gas. As a result, the reaction rate of isobutylene was 98.8%, the selectivity of MAL was 87.2%, the selectivity of MAA was 2.7%, and the total yield was 88.8%.

[Comparative Example 3]
In the same manner as in Example 1, a slurry-like product obtained by mixing solution A and solution B was obtained, and the resulting slurry-like product was heat-treated at 75 ° C. for 1 hour with stirring. A part of the slurry-like material after the heat treatment was collected and measured for specific gravity and viscosity at a slurry temperature of 20 ° C. As a result, the specific gravity was 1.3 g / mL and the viscosity was 89 mPa · s.
Subsequently, the slurry was spray-dried in the same manner as in Example 1 and fired to obtain composite oxide particles. With respect to the composite oxide particles, the Fe / Mo atomic ratio and the Co / Mo atomic ratio were determined in the same manner as in Example 1. As a result, B / A was 0.91, and D / C was 0.45. .
The composite oxide particles were formed into a molded product in the same manner as in Example 1, and the reaction was performed using the molded product in the same manner as in Example 1 using the same raw material mixed gas. As a result, the reaction rate of isobutylene was 97.2%, the selectivity of MAL was 90.4%, the selectivity of MAA was 1.2%, and the total yield was 89.0%.

[Comparative Example 4]
In the same manner as in Example 1, a slurry-like product obtained by mixing solution A and solution B was obtained, and the obtained slurry-like product was heat-treated at 90 ° C. for 1.5 hours with stirring. A part of the slurry-like material after the heat treatment was collected and measured for specific gravity and viscosity at a slurry temperature of 20 ° C. As a result, the specific gravity was 1.35 g / mL and the viscosity was 210 mPa · s.
Subsequently, the slurry was spray-dried in the same manner as in Example 1 and fired to obtain composite oxide particles. With respect to the composite oxide particles, the Fe / Mo atomic ratio and the Co / Mo atomic ratio were determined in the same manner as in Example 1. As a result, B / A was 0.91, and D / C was 0.47. .
The composite oxide particles were formed into a molded product in the same manner as in Example 1, and the reaction was performed using the molded product in the same manner as in Example 1 using the same raw material mixed gas. As a result, the reaction rate of isobutylene was 98.0%, the selectivity of MAL was 91.2%, the selectivity of MAA was 1.5%, and the total yield was 90.8%.

As shown in the above results, when the catalysts of Examples 1 and 2 were used, both the reaction rate of the raw materials and the selectivity of MAL and MAA to be produced were high, compared with the case of using the catalysts of Comparative Examples 1 to 3, The total yield was improved.
On the other hand, compared with Examples 1-2, the catalyst of the comparative example 1 had a low reaction rate and the selectivity of MAA, and the total yield was also low. The catalyst of Comparative Example 2 had a lower MAL selectivity and a lower total yield than Examples 1-2. The catalysts of Comparative Examples 3 to 4 had a lower reaction rate, MAL selectivity, and MAA selectivity, and a lower total yield than Examples 1-2.

Claims (1)

A catalyst for synthesizing unsaturated aldehydes and unsaturated carboxylic acids, comprising particles of a composite oxide containing at least molybdenum, iron and cobalt, wherein the particles satisfy the following formulas (i) and (ii).
B / A ≦ 0.8 (i)
D / C ≦ 0.7 (ii)
[In the formula, A represents the Fe / Mo atomic ratio in the bulk composition of the particles, B represents the Fe / Mo atomic ratio in the surface composition of the particles, and C represents the Co / Mo atomic ratio in the bulk composition of the particles. D represents the Co / Mo atomic ratio in the surface composition of the particles. ]