JP2012250972A - METHOD FOR PRODUCING α,β-UNSATURATED CARBOXYLIC ACID - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an α,β-unsaturated carboxylic acid in high productivity by oxidizing an olefin or an α,β-unsaturated aldehyde with molecular oxygen in a liquid phase.SOLUTION: The method for producing the α,β-unsaturated carboxylic acid includes oxidizing an olefin or an α,β-unsaturated aldehyde with molecular oxygen in a liquid phase in the presence of a supported catalyst containing a palladium, wherein a mixed solvent containing water, alcohol, and an organic carboxylic acid is used as a solvent for the liquid phase, and when X:Y:Z is a mass ratio of water, alcohol, and the organic carboxylic acid in the mixed solvent, the mixed solvent satisfies the following formula (1) and any one of the following conditions (2) to (4): (1) X+Y+Z=1.00; (2) when X<0.20, 0.25≤Y≤0.65; (3) when 0.20≤X<0.40, 0.01≤Y≤0.45; and (4) when 0.40≤X, 0.01≤Y≤0.20.

Description

  The present invention relates to a process for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen in a liquid phase.

  Many α, β-unsaturated carboxylic acids are industrially useful. For example, acrylic acid and methacrylic acid are used in extremely large quantities for applications such as synthetic resin raw materials. As a method for producing an α, β-unsaturated carboxylic acid, a method of oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in a liquid phase has been studied.

  Patent Document 1 includes organic carboxylic acid, alcohol or ketone as a reaction solvent for efficiently obtaining α, β-unsaturated carboxylic acid by liquid phase oxidation of α, β-unsaturated aldehyde with molecular oxygen. It describes that it is carried out with a water-containing organic solvent comprising an organic solvent and water.

  Patent Document 2 includes water, ketone and carboxylic acid as a reaction solvent for efficiently obtaining α, β-unsaturated carboxylic acid by liquid phase oxidation of α, β-unsaturated aldehyde with molecular oxygen. Mixed solvents have been proposed.

International Publication No. 02/083299 Japanese Patent Laid-Open No. 2005-220069

  However, even if the methods described in Patent Documents 1 and 2 are used, sufficient productivity of α, β-unsaturated carboxylic acid cannot be realized, and further improvement is desired.

  An object of the present invention is to provide a method for producing an α, β-unsaturated carboxylic acid with high productivity by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in a liquid phase. .

The method for producing an α, β-unsaturated carboxylic acid according to the present invention comprises oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen in the liquid phase in the presence of a palladium-containing supported catalyst. A method for producing a saturated carboxylic acid, using a mixed solvent containing water, an alcohol and an organic carboxylic acid as a solvent for the liquid phase, and
Α, β-unsaturation satisfying any of the following formulas (1) and (2) to (4) when the mass ratio of water, alcohol and organic carboxylic acid in the mixed solvent is X: Y: Z. A method for producing carboxylic acid.

X + Y + Z = 1.00 (1)
When X <0.20, 0.25 ≦ Y ≦ 0.65 (2)
When 0.20 ≦ X <0.40, 0.01 ≦ Y ≦ 0.45 (3)
When 0.40 ≦ X, 0.01 ≦ Y ≦ 0.20 (4)

  According to the present invention, an α, β-unsaturated carboxylic acid can be produced with high productivity by oxidizing an olefin or an α, β-unsaturated aldehyde with molecular oxygen in a liquid phase.

It is the graph which plotted the methacrylic acid (MAA) productivity with respect to the methacrolein density | concentration in Example group 4, 5 and the comparative example groups 2 and 3. FIG. It is the graph which plotted methacrylic acid (MAA) productivity with respect to composition (alcohol) in mixed solvent in Example group 6 and Comparative example group 4. It is the graph which plotted the methacrylic acid (MAA) productivity with respect to the composition (alcohol) in a mixed solvent in Example group 7 and Comparative example group 5. It is the graph which plotted the methacrylic acid (MAA) productivity with respect to the composition (alcohol) in a mixed solvent in Example 8 and the comparative example group 6. FIG.

  The palladium-containing supported catalyst according to the present invention is a catalyst for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde. This catalyst is suitable for use in the liquid phase. Hereinafter, the production of α, β-unsaturated carboxylic acid by oxidation in the liquid phase with molecular oxygen is referred to as “liquid phase oxidation” as appropriate.

  The present invention relates to a process for producing an α, β-unsaturated carboxylic acid by liquid phase oxidation of an olefin or α, β-unsaturated aldehyde with molecular oxygen.

  In the present invention, as a result of intensive studies, it has been found that the productivity of α, β-unsaturated carboxylic acid is further improved by using a mixed solvent containing water, alcohol and organic carboxylic acid in a predetermined ratio. It was. The mixed solvent is desirably uniform, but may be used in a non-uniform state.

  The organic carboxylic acid contained in the mixed solvent can be appropriately selected from known organic carboxylic acids that can be used as a solvent, but is preferably an organic carboxylic acid having 1 to 6 carbon atoms. Specifically, it is more preferable to use one or more selected from the group consisting of acetic acid, propionic acid, valeric acid and butyric acid, and acetic acid is more preferable. Since the organic carboxylic acid is a solvent, the organic carboxylic acid does not include α, β-unsaturated carboxylic acid generated by the reaction.

  As alcohol contained in a mixed solvent, it can select suitably from well-known alcohols which can be used as a solvent, However, C1-C6 alcohol is preferable. Specifically, it is more preferable to use one or more selected from the group consisting of methanol, ethanol, propanol and t-butanol, and methanol and t-butanol are more preferable.

The mixed solvent contains water, alcohol, and organic carboxylic acid, and when the mass ratio of water, alcohol, and organic carboxylic acid is X: Y: Z, the following formulas (1) and (2) to (2)- Satisfy any of (4).
X + Y + Z = 1.00 (1)
When X <0.20, 0.25 ≦ Y ≦ 0.65 (2)
When 0.20 ≦ X <0.40, 0.01 ≦ Y ≦ 0.45 (3)
When 0.40 ≦ X, 0.01 ≦ Y ≦ 0.20 (4)
By using a mixed solvent that satisfies all of the conditions of the formulas (1) to (4), for example, when a high concentration α, β-unsaturated aldehyde is used as a raw material, it is not clear for what reason it is effective. However, the decrease in activity can be reduced. Thereby, even when the concentration of the α, β-unsaturated aldehyde in the reaction solution is high, the α, β-unsaturated carboxylic acid can be produced with high productivity.

  In the formula (2), when X <0.20, 0.30 ≦ Y ≦ 0.65 is preferable, and 0.35 ≦ Y ≦ 0.65 is more preferable. In the formula (3), when 0.20 ≦ X <0.40, 0.05 ≦ Y ≦ 0.40 is preferable, and 0.10 ≦ Y ≦ 0.35 is more preferable. In the formula (4), when 0.40 ≦ X, it is preferably 0.05 ≦ Y ≦ 0.20, and more preferably 0.08 ≦ Y ≦ 0.20. X is preferably 0.01 or more, and more preferably 0.05 or more. X is preferably 0.70 or less, and more preferably 0.60 or less.

  The reason why the productivity of α, β-unsaturated carboxylic acid is increased by using a mixed solvent containing water, alcohol and organic carboxylic acid in a predetermined ratio as in the present invention is as follows. Conceivable. Water is essential in the reaction for producing an α, β-unsaturated carboxylic acid from an olefin or an α, β-unsaturated aldehyde using a palladium-containing supported catalyst. In addition, it is considered that the organic carboxylic acid works effectively to accelerate the reaction cycle. On the other hand, when the desorption process of hydrogen adsorbed on the palladium-containing supported catalyst surface in the reaction is rate-limiting, it is necessary to increase the dissolved oxygen concentration in the liquid in order to improve the reaction rate, and alcohol with high oxygen solubility. The use of is considered to work effectively. Furthermore, by using alcohol, the dispersibility of the raw material olefin or α, β-unsaturated aldehyde in the solvent was improved, and the productivity of α, β-unsaturated carboxylic acid was further improved. I guess that. In addition, since alcohol is less volatile than ketone, alcohol is easier to handle than ketone when used industrially.

  The solvent mixture according to the present invention may contain other solvents other than water, alcohol and organic carboxylic acid. In that case, as content of the other solvent with respect to the whole mixed solvent, it is preferable that it is 50 mass% or less, and it is more preferable that it is 30 mass% or less.

  The concentration of the olefin or α, β-unsaturated aldehyde used as the raw material for liquid phase oxidation is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass per 100 parts by mass of the solvent present in the reactor. preferable.

  The amount of molecular oxygen used is preferably from 0.1 to 20 mol, more preferably from 0.2 to 15 mol, based on 1 mol of olefin or α, β-unsaturated aldehyde used as a raw material for liquid phase oxidation. 3-10 mol is more preferable.

  The amount of the catalyst used is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and further preferably 1 to 15 parts by mass per 100 parts by mass of the solution present in the reactor.

  The reaction temperature and reaction pressure for liquid phase oxidation are appropriately selected depending on the solvent and reaction raw materials used. The reaction temperature is preferably 30 to 200 ° C, more preferably 50 to 150 ° C. The reaction pressure is preferably atmospheric pressure (0 MPa) to 10 MPa, more preferably 0.1 to 7 MPa.

  Examples of the carrier for the palladium-containing supported catalyst used in the present invention include activated carbon, carbon black, silica, alumina, magnesia, calcia, titania, zirconia, etc. Among them, silica, alumina, and zirconia are preferably used. One type of these carriers may be used, or a plurality of components may be combined.

  The palladium loading rate of the palladium-containing supported catalyst is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, and still more preferably 4 to 20% by mass with respect to the mass of the carrier before supporting.

  In addition, the mass of the palladium element used for calculation of the loading rate is calculated from the palladium content and the blending amount in the raw material of the palladium element to be used. The same applies to the ratio of palladium element and Te / Pd when other elements such as tellurium described later are included.

  The catalyst according to the present invention may contain a base metal element such as antimony, thallium, lead and tellurium, for example. Among these, the catalyst according to the present invention preferably contains a tellurium element. Another element may contain 1 type and may contain 2 or more types. From the viewpoint of developing a high catalytic activity, the proportion of the palladium element in the metal element (excluding the carrier metal component) contained in the palladium-containing supported catalyst is preferably 50% by mass or more, and 80% by mass or more. Is more preferable.

  When the catalyst according to the present invention contains palladium element and tellurium element, by making the number of moles of tellurium element per mole of palladium element (that is, the molar ratio of tellurium element and palladium element: Te / Pd) within a predetermined range, An α, β-unsaturated carboxylic acid can be produced with higher productivity from an olefin or an α, β-unsaturated aldehyde. Te / Pd is preferably 0.005 to 0.35, and more preferably 0.01 to 0.3. This Te / Pd can be adjusted by the blending ratio of the palladium raw material and the tellurium raw material used for the production of the palladium-containing supported catalyst.

  The catalyst according to the present invention can be produced by supporting a palladium raw material on a carrier.

  The raw material of palladium is not particularly limited, and examples thereof include palladium metal, palladium salt, palladium oxide and the like. Of these, palladium salts are preferred. Examples of the palladium salt include palladium chloride, palladium acetate, palladium nitrate, palladium sulfate, tetraammine palladium chloride and bis (acetylacetonato) palladium. Of these, palladium chloride, palladium acetate, palladium nitrate and tetraamminepalladium chloride are preferable, and palladium nitrate is particularly preferable. These may be used alone or in combination of two or more.

  When the catalyst according to the present invention contains the base metal element, the base material may be supported on the support together with the palladium raw material.

  The tellurium raw material used when producing a catalyst containing tellurium element other than palladium element is not particularly limited, and examples include tellurium metal, tellurium salt, telluric acid and salt thereof, telluric acid and salt thereof, and tellurium oxide. it can. Examples of tellurium salts include hydrogen telluride, tellurium tetrachloride, tellurium dichloride, tellurium hexafluoride, tellurium tetraiodide, tellurium tetrabromide, tellurium dibromide, and the like. Examples of tellurate include sodium tellurate and potassium tellurate. Examples of tellurite include sodium tellurite and potassium tellurite. Of these, telluric acid and its salt, telluric acid and its salt, and tellurium oxide are preferred. These may be used alone or in combination of two or more. The tellurium element contained in the tellurium raw material may be in an oxidized state, a reduced state, or a metal state.

  The method for supporting the raw material on the carrier is not particularly limited, and examples thereof include a precipitation method, an ion exchange method, an impregnation method, an immersion method, and a deposition method.

  Alternatively, the palladium raw material may be supported on the support and then heat-treated so that the palladium oxide is supported on the support. As the range of the heat treatment temperature, 150 to 800 ° C is preferable, and 200 to 700 ° C is more preferable. The heat treatment time is not particularly limited, but is preferably in the range of 1 to 12 hours.

  Then, a palladium-containing supported catalyst can be produced by reducing with a reducing agent while the oxidized palladium element is supported on the support.

  The reducing agent to be used is not particularly limited. For example, hydrazine, formaldehyde, sodium borohydride, hydrogen, formic acid, formic acid salt, ethylene, propylene, 1-butene, 2-butene, isobutylene, 1,3-butadiene, 1- Examples include heptene, 2-heptene, 1-hexene, 2-hexene, cyclohexene, allyl alcohol, methallyl alcohol, acrolein, and methacrolein. Only 1 type may be used for a reducing agent and it may use 2 or more types together. In the reduction in the gas phase, it is preferable to use hydrogen as the reducing agent. In the reduction in the liquid phase, it is preferable to use a hydrazine, formaldehyde, formic acid, or formic acid salt as a reducing agent.

  Water is preferable as the solvent used in the reduction in the liquid phase, but depending on the dispersibility, alcohols such as ethanol, 1-propanol, 2-propanol, n-butanol, t-butanol; acetone, methyl ethyl ketone, Ketones such as methyl isobutyl ketone and cyclohexanone; organic acids such as acetic acid, n-valeric acid and isovaleric acid; and organic solvents such as hydrocarbons such as heptane, hexane and cyclohexane can be used alone or in combination. A mixed solvent of these and water can also be used.

  When the reducing agent is a gas, the reduction is preferably performed in a pressure device such as an autoclave in order to increase the solubility in the solution. At that time, the inside of the pressurizer is pressurized with a reducing agent. The pressure is preferably in the range of 0.1 MPa (gauge pressure; hereinafter, pressure is expressed as gauge pressure) to 1.0 MPa.

  Further, when the reducing agent is a liquid, there is no limitation on the apparatus for performing the reduction, and the reduction can be performed by adding the reducing agent to the solution. Although the usage-amount of a reducing agent at this time is not specifically limited, The range of 1-100 mol is preferable with respect to 1 mol of palladium elements of an oxidation state.

  Although the reduction temperature and reduction time vary depending on the reducing agent and the like, the reduction temperature is preferably −5 to 150 ° C., more preferably 15 to 80 ° C. or less. The reduction time is preferably 0.1 to 4 hours, more preferably 0.25 to 3 hours, and further preferably 0.5 to 2 hours.

  The palladium-containing supported catalyst prepared by reduction is preferably washed with water, a solvent or the like. By washing with water, a solvent or the like, impurities derived from raw materials such as chloride, acetate radical, nitrate radical and sulfate radical are removed. The cleaning method and the number of times are not particularly limited. However, depending on the impurities, liquid phase oxidation of the olefin or the α, β-unsaturated aldehyde may be inhibited. Therefore, it is preferable to perform the cleaning so that the impurities can be sufficiently removed. The washed catalyst may be recovered by filtration or centrifugation and used for the reaction as it is.

  Further, the recovered catalyst may be dried. The drying method is not particularly limited, but it is usually dried in air or in an inert gas using a dryer. The dried catalyst can be activated prior to use for liquid phase oxidation if desired. The activation method is not particularly limited, and examples thereof include a heat treatment method in a reducing atmosphere in a hydrogen stream. According to this method, the oxide film on the palladium surface and impurities that could not be removed by washing can be removed. The physical properties of the prepared catalyst can be confirmed by BET specific surface area measurement, XRD (X-ray Diffraction) measurement, CO pulse adsorption method, TEM (Transmission Electron Microscope) measurement, XPS (X-ray Photoelectron Spectroscopy) measurement and the like.

  Next, a method for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in the liquid phase in the presence of the palladium-containing supported catalyst according to the present invention. explain.

  Examples of the raw material olefin include propylene, isobutylene, and 2-butene. Among these, propylene and isobutylene are preferable. Only one type of olefin may be used, or two or more types may be used in combination. The raw material olefin may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities.

  An α, β-unsaturated carboxylic acid produced from an olefin is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin. Specifically, acrylic acid is obtained when the raw material is propylene, and methacrylic acid is obtained when the raw material is isobutylene. In addition, α, β-unsaturated aldehyde is usually obtained from olefin at the same time. This α, β-unsaturated aldehyde is an α, β-unsaturated aldehyde having the same carbon skeleton as the olefin. For example, acrolein is obtained when the raw material is propylene, and methacrolein is obtained when the raw material is isobutylene.

  Examples of the raw α, β-unsaturated aldehyde include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein). Of these, acrolein and methacrolein are preferable. As the α, β-unsaturated aldehyde, only one type may be used, or two or more types may be used in combination. The raw α, β-unsaturated aldehyde may contain a small amount of saturated hydrocarbon and / or lower saturated aldehyde as impurities.

  The α, β-unsaturated carboxylic acid produced from the α, β-unsaturated aldehyde is an α, β-unsaturated carboxylic acid in which the aldehyde group of the α, β-unsaturated aldehyde is changed to a carboxyl group. Specifically, acrylic acid is obtained when the raw material is acrolein, and methacrylic acid is obtained when the raw material is methacrolein.

  As a raw material for liquid phase oxidation, only one of olefin and α, β-unsaturated aldehyde may be used, or a mixture of both may be used.

  Liquid phase oxidation may be carried out in either a continuous type or a batch type, but in view of productivity, the continuous type is preferred industrially.

  As the source of molecular oxygen used for liquid phase oxidation, air is economical and preferable. However, pure oxygen or a mixed gas of pure oxygen and air can also be used, and if necessary, air or pure oxygen is nitrogen, A mixed gas diluted with carbon dioxide, water vapor or the like can also be used. Such a gas containing molecular oxygen is usually preferably supplied in a pressurized state in a reaction vessel such as an autoclave.

  According to the method of the present invention, α, β-unsaturated carboxylic acid can be produced from olefin or α, β-unsaturated aldehyde with high productivity.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to an Example. The “parts” in the following examples and comparative examples are parts by mass.

  Te / Pd and the mass of palladium element and tellurium element used for calculating the loading ratio were calculated from the palladium content and blending amount in the raw material of the palladium element used, and the tellurium content and blending amount in the raw material of the tellurium element used. .

(Analysis of raw materials, products and by-products in the production of α, β-unsaturated carboxylic acids)
The productivity of the α, β-unsaturated carboxylic acid produced is defined as follows.

Productivity of α, β-unsaturated carboxylic acid (g / g / hr) = (A / B / C) × 100
Here, A is the mass (g) of the produced α, β-unsaturated carboxylic acid, B is the mass (g) of palladium used in the reaction, and C is the reaction time (hr).

[Example 1]
(Catalyst preparation)
To 0.054 parts of telluric acid, 10 times the mass of distilled water was added to obtain a homogeneous solution. To this homogeneous solution, 2.185 parts of a palladium solution (manufactured by NE Chemcat: 22.88% by mass palladium nitrate-containing nitric acid aqueous solution) was added, and distilled water was further added to a total of 20.0 parts. After 20 parts of a granular silica support (specific surface area 450 m ² / g, pore volume 0.68 cc / g, median diameter 53.58 μm) is completely immersed in this solution, the immersion solvent is removed by evaporation, Firing was performed at 200 ° C. for 3 hours. The obtained catalyst precursor was added to 20 parts of a 37% by weight aqueous formaldehyde solution, heated to 70 ° C., and stirred for 2 hours. After suction filtration, it was filtered and washed with 1000 parts of warm water to obtain a palladium-containing supported catalyst. The catalyst had a Te / Pd of 0.05.

(Reaction evaluation)
In the autoclave, 4.03 parts of the catalyst obtained by the above method and 100 parts of a mixed solvent containing 12% by weight of water, 44% by weight of methanol and 44% by weight of acetic acid as a reaction solvent were added. Next, 10.0 parts of methacrolein was introduced, and the autoclave was sealed. Then, stirring (rotation speed 1000rpm) was started and it heated up to 90 degreeC. After completion of the temperature increase, compressed air was introduced into the autoclave up to an internal pressure of 3.2 MPa. Thereafter, the reaction was terminated when 30 minutes passed.

  After completion of the reaction, the inside of the autoclave was ice-cooled 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 collecting the gas that was opened by opening the gas outlet. The reaction solution containing the catalyst was taken out from the autoclave, the catalyst was separated with a membrane filter, and the reaction solution was recovered. The recovered reaction solution and the collected gas were analyzed by gas chromatography, and the productivity of methacrylic acid (MAA) was calculated. The results are shown in Table 1. In addition to this example, it was confirmed that the alcohol used as the solvent in all the examples was not oxidized.

[Example 2]
The reaction was performed in the same manner as in Example 1 except that 100 parts of a mixed solvent containing 12% by mass of water, 44% by mass of ethanol, and 44% by mass of acetic acid was used. The results are shown in Table 1.

[Example 3]
The reaction was performed in the same manner as in Example 1 except that 100 parts of a mixed solvent containing 12% by mass of water, 44% by mass of t-butanol and 44% by mass of acetic acid was used. The results are shown in Table 1.

[Comparative Example 1]
The reaction was performed in the same manner as in Example 1 except that 100 parts of a mixed solvent containing 12% by mass of water and 88% by mass of acetic acid was used. The results are shown in Table 1.

[Example groups 4, 5 and comparative example groups 2, 3]
Using a catalyst prepared by the same method as in Example 1, the reaction was evaluated by changing the composition ratio of the mixed solvent and the methacrolein concentration conditions. Table 2 shows the mixed solvent composition. Moreover, the reaction evaluation result is shown in FIG. In FIG. 1, the methacrolein concentration is the mass part of methacrolein per 100 parts by mass of the mixed solvent. Further, the example group 5 includes the example 1, and the comparative example group 3 includes the comparative example 1.

[Example Group 6, Comparative Example Group 4]
Using the catalyst prepared by the same method as in Example 1, water (X) in the total mixed solvent of 1.00 was fixed at 0.12, and the methacrolein concentration per 100 parts by mass of the mixed solvent was fixed at 10.0 parts by mass. The reaction was evaluated by changing the composition other than water (X) in the mixed solvent. The composition of water (X) is shown in Table 3, and the reaction evaluation results are shown in FIG. In FIG. 2, the composition in the mixed solvent (alcohol) is a mass ratio of the alcohol (Y) when the total mixed solvent is 1.00.

[Example Group 7, Comparative Example Group 5]
Using the catalyst prepared by the same method as in Example 1, water (X) in the mixed solvent total 1.00 was fixed at 0.30, and the methacrolein concentration per 100 parts by mass of the mixed solvent was fixed at 10.0 parts by mass. The reaction was evaluated by changing the composition other than water (X) in the mixed solvent. The composition of water (X) is shown in Table 3, and the reaction evaluation results are shown in FIG. In FIG. 3, the composition in the mixed solvent (alcohol) is a mass ratio of the alcohol (Y) when the total mixed solvent is 1.00.

[Example 8, comparative group 6]
Using a catalyst prepared by the same method as in Example 1, water (X) in the mixed solvent total 1.00 was fixed at 0.50, and the methacrolein concentration per 100 parts by mass of the mixed solvent was fixed at 10.0 parts by mass. The reaction was evaluated by changing the composition other than water (X) in the mixed solvent. The composition of water (X) is shown in Table 3, and the reaction evaluation results are shown in FIG. In FIG. 4, the composition in the mixed solvent (alcohol) is a mass ratio of the alcohol (Y) when the total mixed solvent is 1.00.

  The data related to FIG. 1 is shown in Table 4, and the data related to FIGS.

  By using a mixed solvent containing water, alcohol and organic carboxylic acid according to the present invention, α, β-unsaturated carboxylic acid can be produced with high productivity. In particular, by using a mixed solvent having a predetermined composition ratio, an α, β-unsaturated carboxylic acid can be produced with high productivity even when the α, β-unsaturated aldehyde concentration is high.

Claims (1)

A process for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in the liquid phase in the presence of a palladium-containing supported catalyst, comprising water, alcohol and organic carbon A mixed solvent containing an acid as the solvent of the liquid phase, and
Α, β-unsaturation satisfying any of the following formulas (1) and (2) to (4) when the mass ratio of water, alcohol and organic carboxylic acid in the mixed solvent is X: Y: Z. A method for producing carboxylic acid.
X + Y + Z = 1.00 (1)
When X <0.20, 0.25 ≦ Y ≦ 0.65 (2)
When 0.20 ≦ X <0.40, 0.01 ≦ Y ≦ 0.45 (3)
When 0.40 ≦ X, 0.01 ≦ Y ≦ 0.20 (4)

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