Method for producing α-methylene aldehyde compound, and methods for producing α-methylene carboxylic acid and α-methylene carboxylic acid ester

Abstract

The present invention provides a method for economically producing an α-methylene aldehyde compound via a condensation reaction between a formaldehyde and an aldehyde compound, while suppressing the use of a liquid acid. Used is a method for producing an α-methylene aldehyde compound, wherein an α-methylene aldehyde compound represented by general formula (2) is produced via a condensation reaction between a formaldehyde and an aldehyde compound represented by general formula (1) in the presence of a metal oxide catalyst and an amine. (In general formula (1), R1 represents a C1-7 aliphatic hydrocarbon group, and in general formula (2), R1 represents a C1-7 aliphatic hydrocarbon group.)

Description

Method for producing α-methylenealdehyde compounds and method for producing α-methylenecarboxylic acids and α-methylenecarboxylic acid esters

[0001] The present invention relates to a method for producing an α-methylenealdehyde compound and a method for producing an α-methylenecarboxylic acid and an α-methylenecarboxylic acid ester.

[0002] A reaction carried out in a liquid phase in the presence of an amine is known as a reaction for producing an α-methylenealdehyde compound by condensing formaldehyde with an aldehyde compound. Typically, an amine is used as a catalyst in this reaction in the form of a carboxylic acid salt or a mineral acid salt. However, the use of a liquid acid causes corrosion of production facilities, such as equipment used in the reaction. Therefore, when this reaction is used to industrially produce an α-methylenealdehyde compound, the cost of repairing corroded equipment has a significant impact on production costs.

[0003] As a method for producing an α-methylenealdehyde compound, Patent Document 1 describes a method in which paraformaldehyde and an aliphatic aldehyde are reacted in the presence of an aqueous solution of a mineral acid salt of a secondary amine, the solution being adjusted with a mineral acid other than hydrochloric acid and a secondary amine to a pH value of 2 to 5. Furthermore, Patent Document 2 describes a method in which a salt of a weakly acidic cation exchange resin and a secondary amine is used as a catalyst to produce α-methylenealdehyde by condensing formaldehyde and an aldehyde compound.

[0004] JP 2007-77110 A JP 2015-44775 A

[0005] However, the method described in Patent Document 1 requires the use of a mineral acid other than hydrochloric acid, making it difficult to avoid corrosion of equipment, etc., by liquid acid. On the other hand, the method described in Patent Document 2 does not use liquid acid as a reaction raw material. However, according to the description in the Examples, a treatment is performed in which a weakly acidic cation exchange resin is washed with concentrated hydrochloric acid and pure water before the reaction, making it clear that the use of liquid acid is unavoidable. As described above, no method has been found that avoids the use of liquid acid in a method for producing an α-methylenealdehyde compound by condensing formaldehyde and an aldehyde compound.

[0006] Therefore, an object of the present invention is to provide a method for economically producing an α-methylenealdehyde compound by the condensation reaction of formaldehyde with an aldehyde compound while minimizing the use of liquid acid, and a method for producing an α-methylenecarboxylic acid and an α-methylenecarboxylic acid ester from the α-methylenealdehyde compound thus obtained.

[0007] In view of the above-mentioned problems, the present inventors have conducted extensive research and found that the above-mentioned problems can be solved by condensing formaldehyde with an aldehyde compound in the presence of a metal oxide catalyst and an amine, thereby completing the present invention. That is, the present invention includes the following features.

[0008] [1] A method for producing an α-methylenealdehyde compound represented by the following general formula (2) by a condensation reaction of formaldehyde with an aldehyde compound represented by the following general formula (1) in the presence of a metal oxide catalyst and an amine:

[0009]

[0010] (In the general formula (1), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms);

[0011]

[0012] (In general formula (2), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms).

[0013] [2] The method for producing an α-methylenealdehyde compound according to [1], wherein the amine is a secondary amine. [3] The method for producing an α-methylenealdehyde compound according to [2], wherein the secondary amine is at least one amine selected from the group consisting of dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine, di-i-butylamine, di-2-ethylhexylamine, di-n-octylamine, methylethylamine, methyl-n-butylamine, diphenylamine, diethanolamine, morpholine, piperidine, piperazine, pyrazolidine, pyrrolidine, pyrazole, and indole. [4] The method for producing an α-methylenealdehyde compound according to any one of [1] to [3], wherein the molar ratio of the formaldehyde to the amine (formaldehyde / amine) is 0.1 or more and 1,000 or less. [5] The method for producing an α-methylenealdehyde compound according to any one of [1] to [4], wherein a solvent having a relative dielectric constant of 40.0 or less is used in the condensation reaction. [6] The method for producing an α-methylenealdehyde compound according to any one of [1] to [5], wherein the condensation reaction is carried out at a temperature of 10° C. to 100° C. [7] The method for producing an α-methylenealdehyde compound according to any one of [1] to [6], wherein the metal oxide catalyst is an oxide of at least one metal selected from the group consisting of magnesium, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, silver, cadmium, indium, tin, antimony, barium, lanthanum, hafnium, thallium, tungsten, tantalum, and rhenium. [8] The method for producing an α-methylenealdehyde compound according to any one of [1] to [6], wherein the metal oxide catalyst contains at least one metal selected from the group consisting of elements of Group 4 and Group 5. [9] The method for producing an α-methylenealdehyde compound according to any one of [1] to [8], wherein paraformaldehyde is used as the formaldehyde.

[10] The method for producing an α-methylenealdehyde compound according to any one of [1] to [9], wherein the aldehyde compound is propionaldehyde or n-butylaldehyde.

[0014]

[11] A method for producing an α-methylene carboxylic acid, comprising producing an α-methylene aldehyde compound by the production method according to any one of [1] to

[10] and oxidizing the α-methylene aldehyde compound, wherein the α-methylene carboxylic acid is methacrolein and methacrylic acid.

[12] A method for producing a methacrylic acid ester, comprising esterifying the methacrylic acid produced by the production method according to

[11] .

[13] A method for producing an α-methylene carboxylic acid ester, comprising oxidatively esterifying the α-methylene aldehyde compound produced by the production method according to any one of [1] to

[10] , wherein the α-methylene aldehyde compound is methacrolein and the α-methylene carboxylic acid ester is a methacrylic acid ester.

[0015] According to the present invention, the condensation reaction of formaldehyde and an aldehyde compound is carried out while reducing the use of liquid acid, thereby suppressing corrosion of equipment used in the reaction and reducing repair costs. As a result, an α-methylenealdehyde compound can be produced economically. Furthermore, according to the present invention, an α-methylenecarboxylic acid and an α-methylenecarboxylic acid ester can be produced from the α-methylenealdehyde compound thus obtained.

[0016] Hereinafter, embodiments of the present invention will be described in detail. The following description of the constituent elements shows an example of an embodiment of the present invention, and the present invention is not limited to these details. Furthermore, the expressions "XX or more and YY or less" and "XX to YY" that represent a numerical range mean a numerical range including the lower and upper limits that are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range and the numerical values ​​described in the examples can be arbitrarily combined to form a new numerical range.

[0017] <Method for Producing an α-Methylenealdehyde Compound> In the method for producing an α-methylenealdehyde compound according to the present invention, a condensation reaction between formaldehyde and an aldehyde compound is carried out in the presence of a metal oxide catalyst and an amine. The present invention can also be applied in the absence of a liquid acid. In this specification, "liquid acid" refers to a mineral acid or organic acid that exists in liquid form. Furthermore, "in the absence of a liquid acid" means that no liquid acid is present, or if present, only a trace amount, for example, 0.001 mole or less of liquid acid per mole of formaldehyde.

[0018] [Metal Oxide Catalyst] The metal oxide (metal oxide catalyst) used as a catalyst in the present invention includes an oxide of at least one metal selected from the group consisting of magnesium, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, silver, cadmium, indium, tin, antimony, barium, lanthanum, hafnium, thallium, tungsten, tantalum, and rhenium. That is, the metal oxide may include an oxide containing at least one metal selected from the above-mentioned metals. At least one of these metal oxides may be used, or two or more may be used in combination. Furthermore, the metal oxide may be an oxide (composite oxide) of two or more metals selected from the above-mentioned metals, such as zeolite. The metal oxide preferably contains at least one metal selected from the group consisting of Group 4 elements and Group 5 elements. Among the metal oxides, an oxide of at least one metal selected from the group consisting of magnesium, aluminum, silicon, titanium, zirconium, and niobium is preferred because the reaction proceeds quickly.

[0019] The amount of the metal oxide catalyst used is preferably 10 g or more, more preferably 20 g or more, per mole of the aldehyde compound described below, although the amount of the metal oxide catalyst used can be adjusted appropriately depending on the molecular weight of the metal oxide.

[0020] [Amine] The amine used in the present invention is usually a primary amine or a secondary amine. Examples of primary amines include aliphatic amines and aromatic amines having a linear, branched, or cyclic alkyl group, such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, ethylenediamine, and aniline. Examples of secondary amines include aliphatic amines, heterocyclic amines, and aromatic amines having a linear, branched, or cyclic alkyl group. The alkyl group of the aliphatic amine may be substituted with a hydroxyl group. Specific examples of secondary amines include dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine, di-i-butylamine, di-2-ethylhexylamine, di-n-octylamine, methylethylamine, methyl-n-butylamine, diphenylamine, diethanolamine, morpholine, piperidine, piperazine, pyrazolidine, pyrrolidine, pyrazole, and indole. At least one of these amines may be used, or two or more may be used in combination. The amine is preferably a secondary amine, and among secondary amines, aliphatic amines having a linear alkyl group are preferred because the reaction proceeds rapidly, with dimethylamine, diethylamine, di-n-propylamine, or di-n-butylamine being more preferred.

[0021] [Formaldehyde] As the formaldehyde, formaldehyde (formalin), trioxane, paraformaldehyde, etc. in the form of an aqueous solution can be used. Since the reaction proceeds rapidly, it is preferable to use paraformaldehyde as the formaldehyde. Furthermore, the molar ratio of formaldehyde to the amine used in the reaction (formaldehyde / amine) is preferably 0.1 or more and 1000 or less, more preferably 0.1 or more and 500 or less, even more preferably 0.1 or more and 100 or less, even more preferably 1 or more and 75 or less, and particularly preferably 2 or more and 50 or less. If the molar ratio is 0.1 or more, deterioration of the amine is suppressed, thereby suppressing a decrease in production efficiency. Furthermore, if the molar ratio is 1000 or less, the reaction proceeds rapidly, thereby suppressing side reactions.

[0022] [Aldehyde Compound] As the aldehyde compound, an aldehyde compound represented by the following general formula (1) is used.

[0023]

[0024] In general formula (1), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 7 carbon atoms include an alkyl group having 1 to 7 carbon atoms and a cycloalkyl group having 3 to 7 carbon atoms. Specific examples include linear or branched methyl, ethyl, propyl, butyl, pentyl, hexyl, or heptyl groups; and cyclic cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, or cycloheptyl groups. The aliphatic hydrocarbon group having 1 to 7 carbon atoms may contain both a linear or branched alkyl group and a cycloalkyl group. That is, for example, some of the carbon atoms constituting a linear alkyl group may form a cycloalkane.

[0025] Examples of the aldehyde compound represented by general formula (1) include propionaldehyde (propanal), n-butylaldehyde (butanal), valeraldehyde (pentanal), isovaleraldehyde, n-hexylaldehyde (hexanal), 3-methylvaleraldehyde, 4-methylvaleraldehyde, n-heptylaldehyde (heptanal), 3,3-dimethylpentanal, 3,4-dimethylpentanal, 4,4-dimethylpentanal, and 3-methylhexanal. , 4-methylhexanal, 5-methylhexanal, cyclopentylacetaldehyde, n-octylaldehyde, 3-methylheptanal, 4-methylheptanal, 5-methylheptanal, 6-methylheptanal, 3,4-dimethylhexanal, 3,5-dimethylhexanal, 4,5-dimethylhexanal, 3,3,4-trimethylpentanal, 3,4,4-trimethylpentanal, 3-cyclopentylpropanal, and nonylaldehyde. Among these, propionaldehyde and n-butylaldehyde are preferred because they have good contact with the catalyst and the reaction proceeds rapidly. Furthermore, propionaldehyde is particularly preferred because it is easy to recover unreacted raw materials and to separate the product from the catalyst.

[0026] The molar ratio of formaldehyde to the aldehyde compound used in the reaction (formaldehyde / aldehyde compound) is preferably 0.1 to 4, more preferably 0.2 to 3, and even more preferably 0.25 to 2.5. When the molar ratio is 0.1 or more, the reaction tends to proceed quickly. Furthermore, when the molar ratio is 4 or less, reaction inhibition due to excessive adsorption of formaldehyde onto the metal oxide is suppressed.

[0027] [Polymerization Inhibitor] The α-methylenealdehyde compound obtained by the present invention is polymerizable. Therefore, a polymerization inhibitor may be added to the reaction solution to suppress polymerization of the α-methylenealdehyde compound during the reaction. The polymerization inhibitor is not particularly limited, but examples include phenolic polymerization inhibitors such as hydroquinone and methoquinone, and nitroso-based polymerization inhibitors such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4H-TEMPO). When a polymerization inhibitor is added, the amount added is preferably 10 ppm to 5000 ppm, and more preferably 100 ppm to 2000 ppm, relative to the theoretical production amount of the α-methylenealdehyde compound. Adding the polymerization inhibitor so that the amount is 500 ppm to 1500 ppm relative to the theoretical production amount of the α-methylenealdehyde compound is even more preferred, as this facilitates removal of the polymerization inhibitor.

[0028] [Solvent] The condensation reaction according to the present invention may be carried out without a solvent or with a solvent. The type of solvent is not particularly limited, but examples include water, acetonitrile, propionitrile, butyronitrile, benzonitrile, dioxane, dichloromethane, dimethyl sulfoxide, hexane, diglyme, and tetrahydrofuran. Among these, a solvent having a relative dielectric constant of 40.0 or less is preferably used because the reaction proceeds rapidly. Furthermore, the boiling point of the solvent is preferably 200°C or less. Specifically, a solvent selected from acetonitrile, propionitrile, butyronitrile, benzonitrile, dioxane, dichloromethane, hexane, diglyme, and tetrahydrofuran is preferably used, with acetonitrile being particularly preferred. The solvent may be used alone or in combination of two or more. The amount of solvent used is not particularly limited and may be adjusted as appropriate.

[0029] [Condensation Reaction] In the present invention, the condensation reaction of formaldehyde and an aldehyde compound can be carried out using a flow reactor or a batch reactor. When a flow reactor is used, for example, a metal oxide is charged into a tubular reactor, and then formaldehyde, an aldehyde compound, and an amine are passed through the reactor to carry out the reaction. If raw materials remain in the reaction liquid recovered from the flow reactor, the recovered reaction liquid can be circulated back into the reactor to allow the reaction to proceed. On the other hand, side reactions can be suppressed by appropriately adjusting the residence time in the reactor to complete the reaction. When a batch reactor is used, for example, a metal oxide is charged into the reactor, and then formaldehyde, an aldehyde compound, and an amine are further added to carry out the reaction. After the reaction in the batch reactor is completed, the solid metal oxide and the reaction liquid containing the product α-methylenealdehyde compound can be separated by known methods such as filtration or centrifugation. The separated and recovered metal oxide can be reused as a catalyst in the production of the α-methylenealdehyde compound according to the present invention after being washed as appropriate.

[0030] Whether a flow reactor or a batch reactor is used, the reaction is preferably carried out by appropriately heating with a heat medium to a temperature of 10°C to 120°C. The reaction temperature is more preferably 10°C to 110°C, even more preferably 10°C to 100°C, even more preferably 20°C to 90°C, even more preferably 30°C to 70°C, and most preferably 35°C to 65°C. A reaction temperature of 10°C or higher allows the reaction to proceed rapidly. Furthermore, a reaction temperature of 120°C or lower can suppress side reactions and catalyst deterioration. However, when a flow reactor is used, if the reaction temperature is higher than the boiling point of the raw aldehyde compound, the aldehyde compound will boil. As a result, the contact efficiency between the aldehyde compound and the catalyst may decrease, resulting in a low conversion rate of the aldehyde compound. Therefore, in such cases, pressurizing the flow reactor to suppress boiling of the aldehyde compound can improve the contact efficiency and increase reactivity.

[0031] The reaction time is not particularly limited and can be adjusted as appropriate while checking, for example, the conversion rate of the aldehyde compound.

[0032] [α-Methylenealdehyde Compound] As described above, the method according to the present invention makes it possible to efficiently and economically produce an α-methylenealdehyde compound represented by the following general formula (2). As described above, the present invention is applicable even in the absence of a liquid acid.

[0033]

[0034] In general formula (2), R1 is as defined above. The α-methylenealdehyde compound represented by general formula (2) is an α-methylenealdehyde compound in which a methylene group has been introduced at the α-position of the aldehyde compound represented by general formula (1). Specific examples of the α-methylenealdehyde compound include α-methylenealdehyde compounds corresponding to the aldehyde compounds exemplified above. For example, methacrolein, in which R1 in general formula (2) is a methyl group, is a compound useful as an intermediate for methyl methacrylate, a raw material monomer for methacrylic resins and the like.

[0035] <Method for producing α-methylene carboxylic acid> The method for producing α-methylene carboxylic acid according to the present invention includes a step of oxidizing an α-methylene aldehyde compound produced by the method for producing an α-methylene aldehyde compound according to the present invention. This oxidation produces an α-methylene carboxylic acid corresponding to the α-methylene aldehyde compound. From the viewpoint of improving the selectivity of the product, the α-methylene aldehyde compound and the α-methylene carboxylic acid are preferably methacrolein and methacrylic acid, respectively.

[0036] The method for producing α-methylene carboxylic acid according to the present invention can be carried out by contacting a catalyst for producing α-methylene carboxylic acid with a feed gas containing an α-methylenealdehyde compound in a reactor. A known catalyst can be used as the catalyst, with a heteropolyacid catalyst being preferred. A reactor generally used for gas-phase oxidation can be used, with a tubular reactor having a reaction tube filled with a catalyst being preferred. From an industrial perspective, a multi-tubular reactor having a plurality of reaction tubes is preferred.

[0037] The concentration of the α-methylenealdehyde compound in the raw material gas is not particularly limited, but is preferably 1% by volume to 20% by volume, with a lower limit of 3% by volume and an upper limit of 10% by volume. The oxygen source for the raw material gas is not particularly limited, but it is industrially advantageous to use air. If necessary, a gas obtained by mixing pure oxygen with air or the like can also be used. The proportion of oxygen in the raw material gas is not particularly limited, but is preferably 40% by volume to 400% by volume relative to the α-methylenealdehyde compound, with a lower limit of 50% by volume and an upper limit of 300% by volume.

[0038] The raw material gas may be an α-methylenealdehyde compound and oxygen (or an oxygen source) diluted with an inert gas such as nitrogen or carbon dioxide. Furthermore, water vapor may be added to the raw material gas. By carrying out the reaction in the presence of water vapor, α-methylenecarboxylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1% by volume to 50% by volume, more preferably 1% by volume as the lower limit, and more preferably 40% by volume as the upper limit.

[0039] The contact time between the raw material gas and the catalyst is preferably 0.1 to 30 seconds, more preferably 1.0 second as the lower limit, and more preferably 10 seconds as the upper limit. The reaction pressure is preferably 0.1 MPa (G) to 1 MPa (G). Note that the MPa (G) in the reaction pressure means gauge pressure. There are no particular limitations on the reaction temperature, but it is preferably 200 to 450°C, more preferably 250°C as the lower limit, and 400°C as the upper limit.

[0040] <Method for producing α-methylene carboxylic acid ester> The method for producing an α-methylene carboxylic acid ester according to the present invention includes a step of esterifying α-methylene carboxylic acid produced by the method for producing α-methylene carboxylic acid according to the present invention. This esterification produces an α-methylene carboxylic acid ester corresponding to the α-methylene carboxylic acid. From the viewpoint of improving the selectivity of the products, the α-methylene carboxylic acid and the α-methylene carboxylic acid ester are preferably methacrylic acid and a methacrylic acid ester, respectively.

[0041] The alcohol to be reacted with α-methylenecarboxylic acid in the esterification reaction is not particularly limited, and examples thereof include methanol, ethanol, propanol, isopropanol, butanol, and isobutanol. Examples of the resulting α-methylenecarboxylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid cation exchange resin. The temperature of the esterification reaction is preferably 50°C to 200°C.

[0042] Another embodiment of the method for producing an α-methylene carboxylic acid ester according to the present invention includes a step of oxidatively esterifying an α-methylene aldehyde compound produced by the method for producing an α-methylene aldehyde compound according to the present invention. This oxidative esterification produces an α-methylene carboxylic acid ester corresponding to the α-methylene aldehyde compound. Note that "oxidative esterification" refers to oxidation followed by esterification. The methods described above in <Method for producing α-methylene carboxylic acid> and <Method for producing α-methylene carboxylic acid ester> can be applied to the oxidative esterification of an α-methylene aldehyde compound, i.e., a method of oxidizing an α-methylene aldehyde compound and then esterifying the α-methylene carboxylic acid produced by the oxidation.

[0043] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples. Quantitative analysis of the raw material aldehyde compound and the product α-methylene aldehyde compound was carried out using gas chromatography under the following conditions.

[0044] [Analysis conditions] Column: SHIMADZU SH-Rtx-WAX (trade name, manufactured by Shimadzu Corporation, inner diameter 0.25 mm × length 30 m, film thickness 0.50 μm) Sample injection port temperature and sample injection amount: 200°C, 2.0 μL of reaction solution injected by split method (split ratio 40:1) Detector and detector temperature: FID, 220°C Carrier gas and linear velocity: Nitrogen, 30.0 cm / sec Column temperature: Hold at 40°C for 5 minutes, then increase temperature to 110°C at 10°C / min; hold at 110°C for 3 minutes, then increase temperature to 200°C at 15°C / min; hold at 200°C for 3 minutes Quantitative method: Internal standard method using mesitylene as an internal standard

[0045] [Example 1] In a test tube with a cap, TiO as a metal oxide catalyst was ２ A mixture of 0.1 g of STR-100N (product name, manufactured by Sakai Chemical Industry Co., Ltd.), 0.5 mmol of paraformaldehyde in terms of formaldehyde, 0.5 mmol of propionaldehyde as an aldehyde compound, 5 ml of acetonitrile (relative dielectric constant: 35.9) as a solvent, 0.05 mmol of diethylamine as an amine, and 0.05 mmol of mesitylene as an internal standard substance was heated and stirred at 50°C for 2 hours to carry out a condensation reaction. After the reaction, the test tube was rapidly cooled in an ice bath, and the reaction mixture in the test tube was filtered using a filter to separate a reaction solution containing the product from a solid component containing the metal oxide catalyst. The metal oxide catalyst separated from the reaction solution can be repeatedly used in the production of the α-methylenealdehyde compound according to the present invention after appropriate washing treatment. The reaction solution after separation was analyzed using gas chromatography to calculate the propionaldehyde conversion rate and methacrolein yield. The propionaldehyde conversion was 98.3% and the methacrolein yield was 88.2%. The results are shown in Table 1.

[0046] [Example 2] Nb as a metal oxide catalyst ２ O ５ ・nH ２A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of PEG-100 (trade name: JRC-NBO-1, manufactured by Companhia Brasileira de Metalugia e Mineracao) was used. The results are shown in Table 1.

[0047] Example 3 A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of H-type USY zeolite (product name: CBV-720, manufactured by Zeolyst International) was used as the metal oxide catalyst. The results are shown in Table 1.

[0048] [Example 4] Al as a metal oxide catalyst ２ O ３ A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of (trade name: JRC-ALO-6, manufactured by Nikki-Universal Co., Ltd.) was used. The results are shown in Table 1.

[0049] [Example 5] ZrO as a metal oxide catalyst ２ A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of RC-100 (trade name, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was used. The results are shown in Table 1.

[0050] [Example 6] A condensation reaction was carried out in the same manner as in Example 1, except that dimethylamine was used as the amine. The results are shown in Table 1.

[0051] [Example 7] The above ZrO was used as a metal oxide catalyst. ２ The condensation reaction was carried out in the same manner as in Example 6, except that 0.1 g of the compound was used. The results are shown in Table 1.

[0052] Example 8 A condensation reaction was carried out in the same manner as in Example 1, except that di-n-propylamine was used as the amine. The results are shown in Table 1.

[0053] [Example 9] A condensation reaction was carried out in the same manner as in Example 1, except that piperidine was used as the amine. The results are shown in Table 1.

[0054] Example 10 A condensation reaction was carried out in the same manner as in Example 1, except that di-n-butylamine was used as the amine. The results are shown in Table 1.

[0055] [Examples 11 to 19] Condensation reactions were carried out in the same manner as in Example 1, except that the amount of paraformaldehyde charged was changed to the amount shown in Table 1, calculated as formaldehyde. The results are shown in Table 1.

[0056] Examples 20 and 21 Condensation reactions were carried out in the same manner as in Example 1, except that the amount of diethylamine charged was changed as shown in Table 1. The results are shown in Table 1.

[0057] [Example 22] Except for using propylamine as the amine, a condensation reaction was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0058] Comparative Example 1 A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of an ion exchange resin (trade name: Amberlyst-15DRY, manufactured by Organo Corporation) was used instead of the metal oxide catalyst. The results are shown in Table 1.

[0059]

[0060] As shown in Table 1, it was found that by carrying out a condensation reaction between formaldehyde and an aldehyde compound in the presence of a metal oxide catalyst and an amine, an α-methylene aldehyde compound (methacrolein) can be obtained while suppressing the use of liquid acid. Furthermore, a comparison of Examples 1 to 5 with Comparative Example 1 revealed that even with the same solid catalyst, when an ion exchange resin was used, the raw materials and products were adsorbed onto the ion exchange resin, preventing methacrolein from being obtained, whereas when the metal oxide according to the present invention was used, methacrolein was obtained in high yield. Furthermore, as shown in Examples 6 to 10 and 22, the present invention is also applicable when various amines other than diethylamine are used. Furthermore, as shown in Examples 11 to 21, the present invention is also applicable when the molar ratios of formaldehyde / amine and formaldehyde / aldehyde compound are appropriately changed.

[0061] While certain preferred embodiments of the present invention have been shown and described in detail above, it should be understood that the present invention is not limited to the above-described embodiments, but that various changes and modifications are possible without departing from the spirit or scope of the appended claims.

[0062] This application claims priority based on Japanese Patent Application No. 2024-120741, filed on July 26, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A method for producing an α-methylenealdehyde compound represented by the following general formula (2) by a condensation reaction of formaldehyde with an aldehyde compound represented by the following general formula (1) in the presence of a metal oxide catalyst and an amine: (In the general formula (1), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms); (In general formula (2), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms).

2. The method for producing an α-methylenealdehyde compound according to claim 1, wherein the amine is a secondary amine.

3. The method for producing an α-methylene aldehyde compound according to claim 2, wherein the secondary amine is at least one amine selected from the group consisting of dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine, di-i-butylamine, di-2-ethylhexylamine, di-n-octylamine, methylethylamine, methyl-n-butylamine, diphenylamine, diethanolamine, morpholine, piperidine, piperazine, pyrazolidine, pyrrolidine, pyrazole, and indole.

4. The method for producing an α-methylenealdehyde compound according to claim 1, wherein the molar ratio of the formaldehyde to the amine (formaldehyde / amine) is 0.1 or more and 1,000 or less.

5. The method for producing an α-methylenealdehyde compound according to claim 1, wherein a solvent having a relative dielectric constant of 40.0 or less is used in the condensation reaction.

6. The method for producing an α-methylenealdehyde compound according to claim 1, wherein the condensation reaction is carried out at a temperature of 10°C to 100°C.

7. The method for producing an α-methylene aldehyde compound according to any one of claims 1 to 6, wherein the metal oxide catalyst is an oxide of at least one metal selected from the group consisting of magnesium, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, silver, cadmium, indium, tin, antimony, barium, lanthanum, hafnium, thallium, tungsten, tantalum, and rhenium.

8. The method for producing an α-methylenealdehyde compound according to any one of claims 1 to 6, wherein the metal oxide catalyst contains at least one metal selected from the group consisting of Group 4 elements and Group 5 elements.

9. The method for producing an α-methylenealdehyde compound according to any one of claims 1 to 6, wherein paraformaldehyde is used as the formaldehyde.

10. A method for producing an α-methylene aldehyde compound according to any one of claims 1 to 6, wherein the aldehyde compound is propionaldehyde or n-butylaldehyde.

11. A method for producing α-methylenecarboxylic acid, comprising producing an α-methylenealdehyde compound by the production method according to any one of claims 1 to 6 and oxidizing the α-methylenealdehyde compound, wherein the α-methylenealdehyde compound is methacrolein and the α-methylenecarboxylic acid is methacrylic acid.

12. A method for producing a methacrylic acid ester, which comprises esterifying the methacrylic acid produced by the method according to claim 11.

13. A method for producing an α-methylenecarboxylic acid ester, which comprises oxidatively esterifying an α-methylenealdehyde compound produced by the method according to any one of claims 1 to 6, wherein the α-methylenealdehyde compound is methacrolein and the α-methylenecarboxylic acid ester is a methacrylic acid ester.

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