JP2004141863A - Method of producing palladium-containing catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or α, β-unsaturated aldehyde with high selectivity, a method of producing the catalyst, and a method of producing α, β-unsaturated carboxylic acid with high selectivity. <P>SOLUTION: In this production process of the palladium-containing catalyst for producing α, β-unsaturated carboxylic acid from the olefin or α, β-unsaturated aldehyde, a compound containing a palladium atoms in an oxidized state is reduced at -5 to 50°C. By using thus produced palladium-containing catalyst, the α, β-unsaturated carboxylic acid is produced by liquid phase oxidation of the olefin or α, β-unsaturated aldehyde by molecular oxygen. <P>COPYRIGHT: (C)2004,JPO

Description

<< The present invention relates to a method for producing a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde. The present invention also relates to a catalyst for producing an α, β-unsaturated carboxylic acid and a method for producing an α, β-unsaturated carboxylic acid.

As a method for producing a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid by subjecting an olefin to liquid phase oxidation with molecular oxygen, for example, Patent Document 1 discloses that oxidized palladium has 3 to 6 carbon atoms. A method for reduction with an olefin is described. Patent Document 1 also describes that a supported catalyst can be produced by the above method.
JP-A-60-155148

When the inventor of the present application produced acrylic acid from propylene using a palladium-containing catalyst produced according to the method described in the example of Patent Document 1, the by-products (acetaldehyde, acetone , Acrolein, acetic acid, carbon dioxide) in addition to various polymers and oligomers. In Patent Document 1, these polymers and oligomers were not captured, and it was found that the actual selectivity including these by-products was lower than that described in Examples of Patent Document 1. As described above, the selectivity of the α, β-unsaturated carboxylic acid of the catalyst produced by the method described in Patent Document 1 is not yet sufficient, and the production of a catalyst for producing an α, β-unsaturated carboxylic acid having a higher selectivity is not yet completed. A method is desired.

Accordingly, an object of the present invention is to provide a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde with high selectivity, a method for producing the catalyst, and an α, β-unsaturated catalyst. It is to provide a method for producing a saturated carboxylic acid with high selectivity.

The present invention relates to a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde having a step of reducing a compound containing a palladium atom in an oxidized state at −5 to 50 ° C. Is a manufacturing method.

The reducing agent used for the reduction of the compound containing a palladium atom in the oxidation state is selected from the group consisting of ethanol, 2-propanol, hydrazine, formalin, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene. At least one compound selected is preferred.

パ ラ ジ ウ ム The produced palladium-containing catalyst is preferably a supported catalyst in which a reduced product obtained by reducing a compound containing a palladium atom is supported on a carrier.

The present invention is also a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde produced by the above method.

The present invention is also a method for producing an α, β-unsaturated carboxylic acid in which an olefin or an α, β-unsaturated aldehyde is liquid-phase oxidized with molecular oxygen using the above catalyst.

According to the method for producing a palladium-containing catalyst of the present invention, when an α, β-unsaturated carboxylic acid is produced from an olefin or an α, β-unsaturated aldehyde, the production of polymers and oligomers as by-products is small, and α , Β-unsaturated carboxylic acid can be produced at a high selectivity.

When a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from the olefin or α, β-unsaturated aldehyde of the present invention is used, the production of polymers and oligomers as by-products is small, and α, β It is possible to produce unsaturated carboxylic acids with high selectivity.

Further, according to the method of the present invention for producing an α, β-unsaturated carboxylic acid in which liquid phase oxidation of an olefin or an α, β-unsaturated aldehyde with molecular oxygen, the production of polymers and oligomers as by-products is reduced, α, β-unsaturated carboxylic acids can be produced with high selectivity.

In the method for producing a palladium-containing catalyst of the present invention, the compound containing a palladium atom in an oxidized state is reduced at -5 to 50C. Examples of the compound containing a palladium atom in an oxidized state, which is a catalyst raw material, include a palladium salt, palladium oxide, a palladium oxide alloy and the like, and among them, a palladium salt is preferable. Examples of the palladium salt include palladium chloride, palladium acetate, palladium nitrate, palladium sulfate, tetraammine palladium chloride, bis (acetylacetonato) palladium, and the like. Among them, palladium chloride, palladium acetate, tetraammine palladium chloride Is preferred.

還 元 The reduction of the catalyst raw material may be performed in the gas phase, but is preferably performed in the liquid phase in the present invention. Hereinafter, a method for reducing a palladium salt in a liquid phase will be described.

Palladium salt is dissolved in a solvent and reduced using a reducing agent. As a result, the desired palladium metal-containing catalyst is deposited. The method for adding the reducing agent is not particularly limited, and examples thereof include a method of performing reduction while dropping the reducing agent, and a method of performing reduction after adding the entire amount of the reducing agent. Among them, a method of performing reduction while dropping a reducing agent is preferable.

In the present invention, it is particularly important to reduce the palladium salt at −5 to 50 ° C., preferably 0 to 45 ° C., more preferably 10 to 40 ° C., and particularly preferably 15 to 35 ° C. If the reduction temperature exceeds 50 ° C., the selectivity of the resulting catalyst for α, β-unsaturated carboxylic acid will decrease. The time of the reduction treatment is not particularly limited, but is usually 0.1 to 4 hours, preferably 0.25 to 3 hours, more preferably 0.5 to 2 hours.

As the reducing agent, any one can be used as long as it has the ability to reduce the oxidized palladium atoms in the catalyst raw material. As the reducing agent when the catalyst raw material is a palladium salt, for example, ethanol, 2-propanol, hydrazine, formalin, formic acid, oxalic acid, sodium borohydride, lithium aluminum hydride, calcium hydride, hydrogen, ethylene, propylene, Examples thereof include 1-butene, 2-butene, and isobutylene. Among them, ethanol, 2-propanol, hydrazine, formalin, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene are preferred, and hydrazine, formalin, hydrogen and propylene are particularly preferred. Two or more reducing agents may be used in combination for the reduction.

化合物 Further, a compound containing no sulfur in the reducing agent is preferable. Here, the compound containing no sulfur means that no sulfur element is contained in the structure of the compound, that is, it is not a sulfur-containing compound, and the sulfur or the sulfur compound is contained in the reducing agent as a small amount of impurities. Does not mean the case. In the present invention, since the reduction is performed at a relatively low temperature, when a reducing agent containing sulfur is used, the sulfur is strongly adsorbed on the carrier or palladium, so that the catalyst may be poisoned.

When a supported catalyst is prepared, reduction may be performed in the same manner as when no carrier is used, except that the carrier is dispersed in a palladium salt solution. Examples of the carrier include activated carbon, carbon black, silica, alumina, magnesia, calcia, titania, zirconia, and the like. Among them, activated carbon, silica, and alumina are preferable. Since the surface area of the support varies depending on the type of the support and the like, it cannot be said unconditionally. In the case of activated carbon, it is usually 100 to 5000 m ² / g, preferably 300 to 4000 m ² / g. The smaller the surface area of the carrier, the more the useful component can be produced on the surface of the catalyst. The larger the surface area of the carrier, the more the useful component can be produced.

In the preparation of the activated carbon-supported catalyst, when the carrier and the solution containing the palladium salt come into contact with each other before contacting with the reducing agent, palladium is reduced and precipitated by the reaction with the active group present on the outer surface of the carrier, and the palladium is deposited on the carrier. The catalyst may be unevenly distributed on the outer surface. In order to prevent such unintended reduction and to obtain a supported catalyst in which palladium is uniformly dispersed in the inside of the carrier, for example, hydrogen peroxide, nitric acid, hypochlorous acid, etc. are added to the palladium salt solution before contacting with the reducing agent. Preferably, an oxidizing agent such as Even when no carrier is used, palladium may be reduced unintentionally depending on the preparation conditions. Also in this case, reduction can be prevented in the same manner.

In the case of a supported catalyst, the loading ratio of palladium metal is usually 0.1 to 40%, preferably 1 to 30%, more preferably 2 to 20%, and particularly preferably 4 to 15% based on the weight of the carrier. .

As a solvent used in the reduction, water is generally used, but depending on the solubility of the palladium salt or the reducing agent or the dispersibility of the carrier, ethanol, 1-propanol, 2-propanol, n-butanol, t-butanol, Alcohols such as butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; organic acids such as acetic acid, n-valeric acid and iso-valeric acid; and organic solvents such as hydrocarbons such as heptane, hexane and cyclohexane, or these. A mixed solvent of water and water can also be used. When the catalyst raw material is palladium chloride, a mixed solvent of ethanol and water, a mixed solvent of acetone and water, and a mixed solvent of acetic acid and water are preferable.

パ ラ ジ ウ ム A palladium metal-containing catalyst (hereinafter, referred to as a catalyst) precipitated by reduction is usually washed with warm water and filtered. Washing with warm water removes, for example, impurities derived from palladium salts such as chloride, acetate, nitrate, and sulfate. Although the washing method and the number of washing are not particularly limited, there is a possibility that the liquid phase oxidation reaction of the olefin or the α, β-unsaturated aldehyde may be inhibited depending on the impurities. Therefore, it is preferable that the washing is performed to such an extent that the impurities can be sufficiently removed. For example, when palladium chloride is used as a catalyst raw material, impurities are chloride ions, and silver nitrate can be used for this detection. Specifically, the palladium metal-containing catalyst is washed with warm water, a small amount of silver nitrate is added to the washing filtrate after filtering off the catalyst, and the end point of the washing is determined based on whether white precipitation or cloudiness of silver chloride occurs. I can judge.

Next, the filtered catalyst is dried. The drying method is not particularly limited, but is usually dried in the air using a dryer. The dried catalyst must be activated before it can be used in a liquid phase oxidation reaction. The method of activation is not particularly limited, and includes, for example, a method of performing heat treatment in a reducing atmosphere in a hydrogen stream. According to this method, it is possible to remove the oxide film on the surface of the palladium metal and impurities that cannot be removed by washing. The physical properties of the prepared catalyst can be confirmed by BET surface area measurement, XRD measurement, CO pulse adsorption method, TEM measurement and the like.

Next, a method for producing an α, β-unsaturated carboxylic acid by subjecting an olefin or an α, β-unsaturated aldehyde to liquid phase oxidation with molecular oxygen will be described. Examples of the starting olefin include propylene, isobutylene, 1-butene, 2-butene and the like. Among them, propylene and isobutylene are preferable. Examples of the α, β-unsaturated aldehyde as a raw material include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), cinnamaldehyde (β-phenylacrolein), and among others, acrolein and methacrolein are included. It is suitable. The raw material olefin or α, β-unsaturated aldehyde may contain a small amount of a saturated hydrocarbon, a lower saturated aldehyde, or the like as an impurity.

(4) The liquid phase oxidation reaction may be carried out in any of a continuous system and a batch system. However, in view of productivity, the continuous system is preferably used industrially.

As a reaction solvent for the liquid phase oxidation reaction, for example, tertiary butanol, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid, iso-valeric acid, It is preferable to use at least one compound selected from the group consisting of ethyl acetate and methyl propionate. Among them, tertiary butanol, methyl isobutyl ketone, acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid and iso-valeric acid are more preferred. Further, in order to produce the α, β-unsaturated carboxylic acid with good selectivity, it is preferable to make water coexist with these organic solvents. The amount of coexisting water is not particularly limited, but is usually 2 to 70%, preferably 5 to 50% based on the total mass of the organic solvent and water. It is desirable that the mixture of the organic solvent and water is in a uniform state. However, in the case of an organic solvent having low compatibility with water, the mixture may be in a non-uniform state.

濃度 The concentration of the olefin or α, β-unsaturated aldehyde as a raw material for the reaction is usually 0.1 to 20% by mass, preferably 0.5 to 10% by mass, based on the solvent present in the reactor. The amount of molecular oxygen is usually from 0.1 to 20 mol, preferably from 0.3 to 15 mol, more preferably from 0.5 to 10 mol, per mol of the starting olefin or the starting α, β-unsaturated aldehyde. is there.

The amount of the catalyst used is usually 0.1 to 30% by mass, preferably 0.5 to 20% by mass, and more preferably 1 to 15% by mass, based on the solvent present in the reactor.

The reaction temperature and the reaction pressure are appropriately selected depending on the solvent and the reaction raw materials used. The reaction temperature is generally from 30 to 200C, preferably from 50 to 150C. The reaction pressure is generally from atmospheric pressure to 10 MPa, preferably from 0.5 to 5 MPa.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the examples. "Parts" in the following Examples and Comparative Examples are parts by mass, and the analysis of the raw materials and products was performed using gas chromatography. The reaction rate of the olefin or the α, β-unsaturated aldehyde, the selectivity of the formed α, β-unsaturated aldehyde, the selectivity of the formed polymer and oligomer, and the selectivity of the formed α, β-unsaturated carboxylic acid And yield are defined as follows:

Reaction rate of olefin or α, β-unsaturated aldehyde (%)
= (B / A) × 100
Selectivity of α, β-unsaturated aldehyde (%) = (C / B) × 100
Selectivity (%) of α, β-unsaturated carboxylic acid = (D / B) × 100
Selectivity (%) of polymer and oligomer = (E / B) × 100
α, β-unsaturated carboxylic acid yield (%) = (D / A) × 100
Here, A is the number of moles of the supplied olefin or α, β-unsaturated aldehyde, B is the number of moles of the reacted olefin or α, β-unsaturated aldehyde, and C is the mole of the generated α, β-unsaturated aldehyde. Number, D is the number of moles of the formed α, β-unsaturated carboxylic acid, and E is calculated by dividing the total mass (unit: g) of the polymer and oligomer by the molecular weight of the supplied olefin or α, β-unsaturated aldehyde. Of olefins or polymers and oligomers in terms of α, β-unsaturated aldehyde.

{Selectivity (%) of other detected products = 100 × {1− (C / B) − (D / B) − (E / B)}. Here, in the case of the α, β-unsaturated aldehyde oxidation reaction, C / B = 0.

[Example 1]
(Catalyst preparation)
In a three-necked round-bottom flask equipped with a dropping funnel, a condenser and a thermometer, 24.0 parts of activated carbon powder (surface area: 3081 m ² / g) serving as a catalyst carrier were added, and 103.9 parts of ethanol and 400 parts of pure water were added thereto, followed by magnetism. After refluxing at 85 ° C. for 30 minutes while stirring with a tick stirrer, the mixture was cooled to 20 ° C. using an ice bath.

２．０ After 2.0 parts of palladium chloride was dissolved in 23.7 parts of 1M hydrochloric acid by heating, 25.6 parts of 30% hydrogen peroxide solution and 100 parts of pure water were added, and the obtained palladium chloride solution was charged into a dropping funnel. While stirring the inside of the flask, a palladium chloride solution was added dropwise at 20 ° C. over 15 minutes, and stirring was continued at 20 ° C. for 1 hour.

１１11.3 parts of hydrazine monohydrate was dissolved in 100 parts of pure water, and the obtained hydrazine aqueous solution was charged into a dropping funnel. While stirring the inside of the flask, an aqueous hydrazine solution was added dropwise at 20 ° C. over 10 minutes, and stirring was continued at 20 ° C. for 1 hour.

Thereafter, the stirring was stopped, and a black precipitate was separated by suction filtration. At this time, a small amount of hydrazine monohydrate was added to the filtrate, and it was confirmed that palladium did not precipitate. The powdery black precipitate that had been filtered off was washed with warm water until no silver chloride appeared. In addition, the presence or absence of silver chloride was confirmed by adding a small amount of silver nitrate to the filtrate after washing and by the presence or absence of white precipitation or cloudiness of silver chloride.

The washed precipitate was dried at 100 ° C overnight. The obtained dried powder was heat-treated at 200 ° C. for 3 hours under a hydrogen stream to obtain a palladium-supported catalyst. The palladium loading of this catalyst was 5% by mass.

(Reaction evaluation)
120 parts of a 75% tertiary-butanol aqueous solution was added as a reaction solvent to the autoclave, 10.0 parts of the above catalyst and 1.7 parts of methacrolein as a raw material were added, and the autoclave was sealed. Next, stirring was started and the temperature was raised to 90 ° C. After introducing nitrogen into the autoclave to an internal pressure of 1.0 MPa, air was introduced to an internal pressure of 3.5 MPa. In this state, an oxidation reaction of methacrolein was performed for 40 minutes. During the reaction, the pressure change behavior in the reactor was tracked.

終了 After the reaction was completed, the inside of the autoclave was cooled to 20 ° C in an ice bath. A gas collection bag was attached to the gas outlet of the autoclave, and the pressure in the reactor was released while opening the gas outlet and collecting the coming out gas. The reaction solution containing the catalyst was taken out of the autoclave, the catalyst was separated by centrifugation, and only the reaction solution was recovered. The collected reaction solution and the collected gas were analyzed by gas chromatography.

As a result, the methacrolein conversion was 77.2%, the methacrylic acid selectivity was 69.5%, the polymer / oligomer selectivity was 20.3%, and the methacrylic acid yield was 53.7%.

[Example 2]
The same procedure as in Example 1 was carried out except that activated carbon powder having a surface area of 3230 m ² / g was used as the catalyst carrier and only air was introduced up to an internal pressure of 3.5 MPa without introducing nitrogen in the oxidation reaction of methacrolein. The catalyst was prepared and the reaction was evaluated. As a result, the conversion of methacrolein was 77.7%, the selectivity of methacrylic acid was 68.1%, the selectivity of polymer / oligomer was 23.2%, and the yield of methacrylic acid was 52.9%.

[Example 3]
Catalyst preparation and reaction evaluation were performed in the same manner as in Example 2 except that the heat treatment time under a hydrogen stream in the catalyst preparation was set to 1 hour, and 120 parts of a 70% aqueous acetic acid solution was used as a reaction solvent for the oxidation reaction of methacrolein. . As a result, the methacrolein conversion was 79.7%, the methacrylic acid selectivity was 69.3%, the polymer / oligomer selectivity was 24.3%, and the methacrylic acid yield was 55.2%.

[Example 4]
Instead of hydrogen-reducing the precipitate after washing, the precipitate was dispersed in 75 parts of a 70% acetic acid aqueous solution, heat-treated in an autoclave under a propylene pressure of 0.5 MPa at 50 ° C. for 1 hour, and filtered to obtain a catalyst. A catalyst was prepared in the same manner as in Example 2. Using this catalyst, a reaction was evaluated under the same conditions as in Example 3. As a result, the conversion of methacrolein was 65.2%, the selectivity of methacrylic acid was 73.0%, the selectivity of polymer / oligomer was 22.3%, and the yield of methacrylic acid was 47.6%.

[Example 5]
In a three-necked round-bottom flask equipped with a dropping funnel, a condenser, and a thermometer, 12.0 parts of spherical activated carbon (surface area: 930 m ² / g) serving as a catalyst carrier was added, and 31.2 parts of ethanol and 150 parts of pure water were added thereto to form a magnet. After refluxing at 85 ° C for 30 minutes while stirring with a tick stirrer, the mixture was cooled to 40 ° C using an ice bath.

２．０ After 2.0 parts of palladium chloride was dissolved in 14.2 parts of 1M hydrochloric acid by heating, 15.3 parts of 30% hydrogen peroxide solution and 50 parts of pure water were added, and the obtained palladium chloride solution was charged into a dropping funnel. A palladium chloride solution was added dropwise at 40 ° C. over 15 minutes while stirring the flask, and stirring was continued at 40 ° C. for 1 hour.

3.4 parts of formalin was dissolved in 50 parts of pure water, and the obtained aqueous solution of formalin was charged into a dropping funnel. An aqueous formalin solution was added dropwise at 40 ° C. over 10 minutes while stirring the inside of the flask, then a solution of 0.5 part of sodium hydroxide dissolved in 50 parts of pure water was similarly added dropwise, and the mixture was stirred at 40 ° C. for 1 hour. Continued.

Thereafter, the stirring was stopped, and a black precipitate was separated by suction filtration. At this time, a small amount of hydrazine monohydrate was added to the filtrate, and it was confirmed that palladium did not precipitate. The powdery black precipitate that had been filtered off was washed with warm water until no silver chloride appeared.

The washed precipitate was dried at 100 ° C overnight. The obtained dry powder was heat-treated at 200 ° C. for 1 hour under a hydrogen stream to obtain a palladium-supported catalyst. The palladium loading of this catalyst was 10% by mass.

The reaction was evaluated in the same manner as in Example 1. As a result, the methacrolein conversion was 35.6%, the methacrylic acid selectivity was 68.1%, the polymer / oligomer selectivity was 23.8%, and the methacrylic acid yield was 24.3%. Met.

[Example 6]
The reaction was evaluated in the same manner as in Example 1, except that the amount of the catalyst used for the reaction evaluation was changed to 2.0 parts. As a result, the conversion of methacrolein was 45.7%, the selectivity of methacrylic acid was 72.0%, the selectivity of polymer / oligomer was 18.9%, and the yield of methacrylic acid was 32.9%.

[Example 7]
The autoclave was charged with 120 parts of a 75% tertiary-butanol aqueous solution as a reaction solvent, 10.0 parts of the catalyst prepared in Example 1 was added, the autoclave was sealed, and 6.6 parts of liquefied isobutylene was introduced into the autoclave. Next, stirring was started and the temperature was raised to 90 ° C. Air was introduced into the autoclave up to 3.5 MPa, and isobutylene oxidation reaction was performed for 40 minutes in this state. During the reaction, the pressure change behavior in the reactor was tracked.

終了 After the reaction was completed, the inside of the autoclave was cooled to 20 ° C in an ice bath. A gas collection bag was attached to the gas outlet of the autoclave, and the pressure in the reactor was released while opening the gas outlet and collecting the coming out gas. The reaction solution containing the catalyst was taken out of the autoclave, the catalyst was separated by centrifugation, and only the reaction solution was recovered. The collected reaction solution and the collected gas were analyzed by gas chromatography.

As a result, the conversion of isobutylene was 38.2%, the selectivity of methacrolein was 61.9%, the selectivity of methacrylic acid was 13.7%, the selectivity of polymer / oligomer was 14.5%, and the yield of methacrylic acid was 5.2%. .

[Comparative Example 1]
A catalyst was prepared in the same manner as in Example 5 except that a palladium chloride solution was added dropwise at 60 ° C and stirring was continued at 60 ° C, and a hydrazine monohydrate solution was added dropwise at 60 ° C and stirring was continued at 60 ° C. went. The reaction evaluation was performed in the same manner as in Example 1 using the catalyst thus obtained. As a result, the methacrolein conversion was 12.6%, the methacrylic acid selectivity was 6.9%, the polymer / oligomer selectivity was 90.7%, and the methacrylic acid yield was 0.9%.

[Comparative Example 2]
Instead of hydrogen reducing the precipitate after washing, the precipitate was dispersed in 75 parts of a 70% aqueous acetic acid solution, heat-treated at 80 ° C. for 1 hour under a propylene pressure of 0.5 MPa in an autoclave, and filtered to obtain a catalyst. A catalyst was prepared in the same manner as in Comparative Example 1. Using this catalyst, a reaction was evaluated under the same conditions as in Example 3. As a result, the conversion of methacrolein was 39.1%, the selectivity of methacrylic acid was 17.0%, the selectivity of polymer / oligomer was 76.9%, and the yield of methacrylic acid was 6.7%.

[Comparative Example 3]
The reaction was evaluated in the same manner as in Example 7 except that the catalyst in Comparative Example 1 was used. As a result, the conversion of isobutylene was 30.1%, the selectivity of methacrolein was 28.0%, the selectivity of methacrylic acid was 3.0%, the selectivity of polymer / oligomer was 61.3%, and the yield of methacrylic acid was 0.9%. .

Claims (5)

(4) A method for producing a palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde, comprising a step of reducing a compound containing a palladium atom in an oxidized state at −5 to 50 ° C. A reducing agent used for reduction of a compound containing a palladium atom in an oxidized state is selected from the group consisting of ethanol, 2-propanol, hydrazine, formalin, sodium borohydride, hydrogen, ethylene, propylene, 1-butene, 2-butene and isobutylene. The method for producing a palladium-containing catalyst according to claim 1, which is at least one compound selected. 3. The method for producing a palladium-containing catalyst according to claim 1, wherein the produced palladium-containing catalyst is a supported catalyst in which a reduced product obtained by reducing a compound containing a palladium atom is supported on a carrier. A palladium-containing catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde produced by the method according to claim 1. A process for producing an α, β-unsaturated carboxylic acid, comprising subjecting an olefin or an α, β-unsaturated aldehyde to liquid phase oxidation with molecular oxygen using the catalyst according to claim 4.