Production method for α-methylene aldehyde compound and production method for α-methylene carboxylic acid and α-methylene carboxylic acid ester

Abstract

Provided is a novel method that makes it possible to economically produce an α-methylene aldehyde compound by condensation of formaldehyde and an aldehyde compound. The present invention is a production method for an α-methylene aldehyde compound that involves condensing formaldehyde and an aldehyde compound represented by general formula (1) in the presence of a metal oxide catalyst to produce an α-methylene aldehyde compound represented by general formula (2). (In general formula (1), R1 represents a C1–7 aliphatic hydrocarbon group.) (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 and an aldehyde compound. For example, a carboxylic acid salt or mineral acid salt of a secondary amine (see Patent Document 1) is used as a catalyst in this reaction. However, in a reaction for producing an α-methylenealdehyde compound using a secondary amine salt as a catalyst, it is known that the reactivity of the catalyst decreases as the secondary amine changes to a tertiary amine. Therefore, Patent Document 2 studies how to suppress the change in the secondary amine by maintaining a mixture of a catalyst and formaldehyde at 0 to 50°C and adding a specific amount of an aldehyde compound to the formaldehyde to carry out the reaction.

[0003] JP 2007-77110 A JP 2016-124790 A

[0004] In order to reduce the production cost of an α-methylenealdehyde compound, it is necessary to repeatedly use the amine catalyst. However, in the conventional methods described in Patent Documents 1 and 2, the repeated use of the catalyst inevitably leads to deterioration and loss of the secondary amine, and therefore, a drastic measure has been required.

[0005] Therefore, an object of the present invention is to provide a novel method for producing an α-methylenealdehyde compound by a condensation reaction of formaldehyde with an aldehyde compound, which method can economically produce an α-methylenealdehyde compound, and a method for producing an α-methylenecarboxylic acid and an α-methylenecarboxylic acid ester from the α-methylenealdehyde compound thus obtained.

[0006] 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 and an aldehyde compound using a metal oxide catalyst, thereby completing the present invention. That is, the present invention includes the following features.

[0007] [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:

[0008]

[0009] (In the general formula (1), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms);

[0010]

[0011] (In general formula (2), R1 represents an aliphatic hydrocarbon group having 1 to 7 carbon atoms).

[0012] [2] The method for producing an α-methylenealdehyde compound according to [1], wherein the condensation reaction is carried out in a state where the amount of amine is less than 0.001 mole per mole of formaldehyde. [3] The method for producing an α-methylenealdehyde compound according to [1] or [2], wherein the condensation reaction is carried out at a temperature exceeding 70°C. [4] The method for producing an α-methylenealdehyde compound according to any of [1] to [3], wherein the condensation reaction is carried out at a temperature of 250°C or less. [5] The method for producing an α-methylenealdehyde compound according to any of [1] to [4], wherein the molar ratio of the formaldehyde to the aldehyde compound (formaldehyde / aldehyde compound) is 1.5 or more and 4.0 or less. [6] The method for producing an α-methylenealdehyde compound according to any one of [1] to [5], 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. [7] The method for producing an α-methylenealdehyde compound according to any one of [1] to [5], wherein the metal oxide catalyst contains at least one metal selected from the group consisting of Group 4 elements and Group 5 elements. [8] The method for producing an α-methylenealdehyde compound according to any one of [1] to [7], wherein paraformaldehyde is used as the formaldehyde. [9] The method for producing an α-methylenealdehyde compound according to any one of [1] to [8], wherein the aldehyde compound is propionaldehyde or n-butylaldehyde.

[0013]

[10] 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 [9] and oxidizing the α-methylene aldehyde compound, wherein the α-methylene aldehyde compound is methacrolein and the α-methylene carboxylic acid is methacrylic acid.

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

[10] .

[12] 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 [9], wherein the α-methylene aldehyde compound is methacrolein and the α-methylene carboxylic acid ester is a methacrylic acid ester.

[0014] According to the present invention, by carrying out a condensation reaction between formaldehyde and an aldehyde compound using a metal oxide as a catalyst, the product α-methylenealdehyde compound and the metal oxide catalyst can be easily separated and recovered by a simple method such as filtration or centrifugation. The recovered metal oxide catalyst can be repeatedly used to produce an α-methylenealdehyde compound. Furthermore, according to the present invention, an α-methylenealdehyde compound can be produced even in the absence of an amine, eliminating the need to consider amine deterioration and the energy required to separate the amine from the product. As described above, according to the present invention, an α-methylenealdehyde compound can be economically produced from formaldehyde and an aldehyde compound. 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.

[0015] 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.

[0016] <Method for Producing an α-methylenealdehyde Compound> In the method for producing an α-methylenealdehyde compound according to the present invention, a condensation reaction of formaldehyde with an aldehyde compound is carried out using a metal oxide catalyst. Note that the present invention can also be applied in the absence of an amine.

[0017] [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 metal oxides, oxides of at least one metal selected from the group consisting of magnesium, aluminum, silicon, titanium, zirconium, niobium, and hafnium are preferred because the reaction proceeds quickly, and oxides of at least one metal selected from the group consisting of titanium, niobium, and hafnium are more preferred.

[0018] 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.

[0019] [Formaldehyde] As formaldehyde, formaldehyde (formalin) in the form of an aqueous solution, trioxane, paraformaldehyde, etc. It is preferable to use paraformaldehyde as formaldehyde because the reaction proceeds quickly.

[0020] [Aldehyde Compound] As the aldehyde compound, an aldehyde compound represented by the following general formula (1) is used.

[0021]

[0022] 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.

[0023] 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.

[0024] The molar ratio of formaldehyde to the aldehyde compound used in the reaction (formaldehyde / aldehyde compound) is preferably 0.1 or more and 4.0 or less, and more preferably 1.5 or more and 4.0 or less. When the molar ratio is 0.1 or more, the reaction tends to proceed quickly. Furthermore, when the molar ratio is 4.0 or less, reaction inhibition due to excessive adsorption of formaldehyde onto the metal oxide is suppressed.

[0025] [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.

[0026] [Solvent] The condensation reaction according to the present invention may be carried out without a solvent or using 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 selected from acetonitrile, propionitrile, butyronitrile, benzonitrile, dioxane, dichloromethane, hexane, diglyme, and tetrahydrofuran is preferably used because the reaction proceeds quickly. The boiling point of the solvent is preferably 210°C or lower. One solvent may be used alone, or two or more solvents may be used in combination. The amount of solvent used is not particularly limited and may be adjusted as appropriate.

[0027] [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 and an aldehyde compound 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 and an aldehyde compound 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.

[0028] Whether a flow reactor or a batch reactor is used, the reaction is preferably carried out by appropriately heating with a heat medium so that the temperature exceeds 70°C. The lower limit of the reaction temperature is more preferably 100°C, more preferably 110°C, more preferably 115°C, even more preferably 120°C, and most preferably 140°C. The upper limit of the reaction temperature is preferably 250°C, more preferably 230°C, and even more preferably 210°C. If the reaction temperature is above 70°C, the reaction proceeds rapidly. Furthermore, if the reaction temperature is 250°C or less, side reactions and catalyst deterioration can be suppressed. 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, the contact efficiency can be improved and reactivity can be increased by pressurizing the flow reactor to suppress boiling of the aldehyde compound.

[0029] The reaction time is not particularly limited and can be adjusted as appropriate while checking, for example, the conversion rate of the aldehyde compound.

[0030] As described above, the present invention can be applied even in the absence of an amine. In this specification, "in the absence of an amine" means that no amine is present, or even if present, only a trace amount of amine is present. In other words, the condensation reaction of formaldehyde and an aldehyde compound according to the present invention can be carried out even in a state where the amount of amine is less than 0.001 mole per mole of formaldehyde.

[0031] [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 an amine. Therefore, the present invention is a novel method that can economically produce an α-methylenealdehyde compound by a condensation reaction of formaldehyde and an aldehyde compound using a metal oxide catalyst in the absence of an amine.

[0032]

[0033] 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.

[0034] <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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] <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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] [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 toluene as an internal standard

[0044] Example 1 2.5 mmol of propionaldehyde and 0.25 mmol of toluene as an internal standard were dissolved in 1,4-dioxane to prepare 10 ml of a propionaldehyde solution. Then, a 25 ml autoclave with a Teflon (registered trademark) inner cylinder was charged with Nb as a metal oxide catalyst. ２ O ５ ・nH ２ 0.1 g of propionaldehyde (trade name: JRC-NBO-1, manufactured by Companhia Brasileira de Metalugia e Mineraçao) and 7.5 mmol of paraformaldehyde equivalent to formaldehyde were added to the autoclave. Next, 10 ml of the previously prepared propionaldehyde solution was added to the autoclave, and the mixture was heated and stirred at 160°C for 3 hours to carry out a condensation reaction. After the reaction, the autoclave was quenched in an ice bath, and the reaction mixture in the autoclave was filtered using a membrane filter to separate the reaction liquid containing the product from a solid component containing the metal oxide catalyst. The reaction liquid after separation was analyzed using gas chromatography, and the propionaldehyde conversion and methacrolein yield were calculated. The propionaldehyde conversion was 45.9%, and the methacrolein yield was 29.0%. The results are shown in Table 1. The metal oxide catalyst separated from the reaction solution can be washed as needed and then reused in the production of the α-methylenealdehyde compound according to the present invention.

[0045] Example 2 Synthesis of Hf-Beta Zeolite A 50 ml Teflon (registered trademark) beaker was charged with a PTFE stirrer, 54 mmol of a 35% by mass aqueous solution of tetraammonium hydroxide (manufactured by Sigma-Aldrich), 6.9 g of Milli-Q water, and HfCl. ４ 1 mmol of HfCl was added, and the mixture was heated and stirred at 60°C for 30 minutes. ４ The resulting solution was cooled to room temperature, and then 100 mmol of tetraethyl orthosilicate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added. Heating and stirring at 70°C was continued until the mass decreased by 26 g. The solution was then cooled to room temperature, and 50 mmol of 46% by mass hydrofluoric acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added and stirred to obtain a white powder. The resulting white powder was pulverized in a mortar, placed in a PTFE-lined autoclave, and heated at 150°C for 21 days. The resulting powder was suction-filtered while being washed with ethanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and Milli-Q water, and the washed powder was dried overnight at 60°C. The dried powder was then calcined at 580°C for 6 hours to obtain Hf-Beta zeolite.

[0046] A condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of the Hf-Beta zeolite prepared above was used as the metal oxide catalyst. The results are shown in Table 1.

[0047] [Example 3] TiO as a metal oxide catalyst ２ The condensation reaction was carried out in the same manner as in Example 1, except that 0.1 g of STR-100N (trade name, manufactured by Sakai Chemical Industry Co., Ltd.) was used. The results are shown in Table 1.

[0048] Comparative Example 1 A condensation reaction was carried out in the same manner as in Example 1, except that no metal oxide catalyst was added. The results are shown in Table 1.

[0049] Example 4 A condensation reaction was carried out in the same manner as in Example 1, except that the condensation reaction temperature was 110° C. The results are shown in Table 1.

[0050] Example 5 A condensation reaction was carried out in the same manner as in Example 1, except that the condensation reaction temperature was 210° C. The results are shown in Table 1.

[0051]

[0052] As shown in Table 1, it was found that by using the metal oxide according to the present invention as a catalyst, an α-methylene aldehyde compound can be produced from formaldehyde and an aldehyde compound even in the absence of an amine. Note that in Examples 1 to 5, the propionaldehyde conversion rate was about 20% to 50%, but the propionaldehyde conversion rate and methacrolein yield can be appropriately improved by changing various reaction conditions, such as extending the reaction time, adjusting the reaction temperature, or adding a polymerization inhibitor.

[0053] 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.

[0054] This application claims priority based on Japanese Patent Application No. 2024-120742, 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: (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 condensation reaction is carried out in a state where the amount of the amine is less than 0.001 mole per mole of the formaldehyde.

3. The method for producing an α-methylenealdehyde compound according to claim 2, wherein the condensation reaction is carried out at a temperature exceeding 70°C.

4. The method for producing an α-methylenealdehyde compound according to claim 3, wherein the condensation reaction is carried out at a temperature of 250°C or less.

5. A method for producing an α-methylenealdehyde compound according to any one of claims 1 to 4, wherein the molar ratio of the formaldehyde to the aldehyde compound (formaldehyde / aldehyde compound) is 1.5 or more and 4.0 or less.

6. The method for producing an α-methylene aldehyde compound according to any one of claims 1 to 4, 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.

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

8. The method for producing an α-methylenealdehyde compound according to any one of claims 1 to 4, wherein paraformaldehyde is used as the formaldehyde.

9. A method for producing an α-methylene aldehyde compound according to any one of claims 1 to 4, wherein the aldehyde compound is propionaldehyde or n-butylaldehyde.

10. A method for producing an α-methylenecarboxylic acid, comprising producing an α-methylenealdehyde compound by the production method according to any one of claims 1 to 4 and oxidizing the α-methylenealdehyde compound, wherein the α-methylenealdehyde compound is methacrolein and the α-methylenecarboxylic acid is methacrylic acid.

11. A method for producing a methacrylic acid ester, which comprises esterifying the methacrylic acid produced by the method according to claim 10.

12. 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 4, wherein the α-methylenealdehyde compound is methacrolein and the α-methylenecarboxylic acid ester is a methacrylic acid ester.

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