Method for producing aldehyde

Abstract

Provided is a method for producing an aldehyde, with which a target aldehyde can be obtained at a high conversion rate and high selectivity. The method for producing an aldehyde involves a hydrogenation step in which an α,β-unsaturated aldehyde represented by formula (1) is hydrogenated in the presence of a palladium-containing catalyst and a carbonate to obtain an aldehyde represented by formula (2), wherein the amount of the carbonate is 1-2 equivalents relative to the acid content in the α,β-unsaturated aldehyde, and the carbonate is at least one selected from the group consisting of sodium carbonate and potassium carbonate. In the formula, R1 is an alkyl group having 1-6 carbon atoms, and R2 is a hydrogen atom or a methyl group.

Description

Aldehyde production method

[0001] The present invention relates to a method for producing aldehydes.

[0002] It is known that some aldehyde 3-phenylpropanal compounds are useful as raw materials for compounded fragrances. For example, 3-(p-tert-butylphenyl)-2-methylpropanal (p-tert-butyl-α-methylhydrocinnamic aldehyde, lilial) is a fragrance with a lily of the valley-like odor.

[0003] One method for synthesizing a 3-phenylpropanal compound is to hydrogenate a cinnamaldehyde compound. For example, Patent Document 1 discloses a method for producing 3-phenylpropionaldehyde in high yield and selectivity by adding 1 to 5 wt % of water relative to the amount of cinnamaldehyde to the reaction mixture. Patent Document 1 also discloses that the selectivity of hydrogenation can be further increased by adding an alkali salt of a weak acid, such as potassium acetate, to the reaction mixture.

[0004] Special Publication No. 10-508008

[0005] As described above, some 3-phenylpropanal compounds have a distinctive fragrance and are useful as fragrances. In particular, 3-(4-alkylphenyl)propenals, in which the phenyl group is substituted with an alkyl group, are useful as fragrances. However, if impurities are contained in the resulting compound due to side reactions during production, even small amounts can have a significant impact on the fragrance. Furthermore, removing these impurities to obtain the desired fragrance compound requires a purification step, which requires a great deal of labor. Therefore, a production method for obtaining 3-phenylpropanal compounds with higher yields and higher purity is desired. Therefore, an object of the present invention is to provide a method for producing an aldehyde that can obtain the desired aldehyde with high conversion and high selectivity.

[0006] The present inventors have found that the above-mentioned problems can be solved by a production method in which hydrogenation is carried out in the presence of a specific catalyst and a specific type and amount of carbonate, and have thus completed the present invention.

[0007] That is, the present invention is as follows: [1] A method for producing an aldehyde, comprising a hydrogenation step of hydrogenating an α,β-unsaturated aldehyde represented by the following formula (1) in the presence of a palladium-containing catalyst and a carbonate to obtain an aldehyde represented by the following formula (2), wherein the amount of the carbonate is 1 to 2 equivalents relative to the acid content of the α,β-unsaturated aldehyde, and the carbonate is at least one selected from the group consisting of sodium carbonate and potassium carbonate. (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２ is a hydrogen atom or a methyl group. ２ [3] The method for producing an aldehyde according to the above [1], wherein R is a hydrogen atom. １ is an isobutyl group or a normal butyl group. [4] The method for producing an aldehyde according to any one of [1] to [3] above, wherein the α,β-unsaturated aldehyde used in the hydrogenation step has an acid value of 0.3 to 3.0 mgKOH / g. [5] The method for producing an aldehyde according to any one of [1] to [4] above, wherein the acid component contained in the α,β-unsaturated aldehyde includes at least one selected from the group consisting of a carboxylic acid represented by the following formula (3) and a carboxylic acid represented by the following formula (4): (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２is a hydrogen atom or a methyl group.) [6] The method for producing an aldehyde according to any one of [1] to [5] above, wherein the carbonate is potassium carbonate. [7] The method for producing an aldehyde according to any one of [1] to [6] above, wherein the hydrogen pressure in the hydrogenation step is 0.5 to 2 MPaG. [8] The method for producing an aldehyde according to any one of [1] to [7] above, wherein the temperature in the hydrogenation step is 40 to 90°C. [9] The method for producing an aldehyde according to any one of [1] to [8] above, comprising an aldol condensation step of aldol condensing an alkylbenzaldehyde with acetaldehyde or propionaldehyde to obtain an α,β-unsaturated aldehyde represented by formula (1), wherein the alkylbenzaldehyde has an acid value of 0.05 to 1.0 mgKOH / g.

[10] The method for producing an aldehyde according to any one of [1] to [9] above, further comprising a step of measuring the acid value of the α,β-unsaturated aldehyde used in the hydrogenation step and calculating the amount of acid contained in the α,β-unsaturated aldehyde.

[0008] According to the present invention, it is possible to provide a method for producing an aldehyde, which can produce a target aldehyde with high conversion and high selectivity.

[0009] Hereinafter, in this specification, the expression "XX to YY" means "XX or more and YY or less."

[0010] The method for producing an aldehyde of the present invention includes a hydrogenation step of hydrogenating an α,β-unsaturated aldehyde represented by the following formula (1) in the presence of a palladium-containing catalyst and a carbonate to obtain an aldehyde represented by the following formula (2), wherein the amount of the carbonate is 1 to 2 equivalents relative to the acid content of the α,β-unsaturated aldehyde, and the carbonate is at least one selected from the group consisting of sodium carbonate and potassium carbonate. (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２ is a hydrogen atom or a methyl group.

[0011] [Hydrogenation Step] The method for producing an aldehyde of the present invention includes a hydrogenation step of hydrogenating an α,β-unsaturated aldehyde represented by the formula (1) in the presence of a palladium-containing catalyst and a carbonate to obtain an aldehyde represented by the formula (2).

[0012] <α,β-Unsaturated aldehyde represented by formula (1)> The α,β-unsaturated aldehyde used in this step is a raw material for the target aldehyde represented by formula (2). １ is an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 2 to 4 carbon atoms, even more preferably an alkyl group having 3 to 4 carbon atoms, and even more preferably an alkyl group having 4 carbon atoms. More specifically, R １ includes a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a normal pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a 3-pentyl group, a neopentyl group, a normal hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, and a neohexyl group, and is preferably a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, or a sec-butyl group. Preferably, the alkyl group is an ethyl group, more preferably an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, or a sec-butyl group, even more preferably a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, or a sec-butyl group, and even more preferably a normal butyl group, an isobutyl group, or a sec-butyl group. From the viewpoints of conversion rate, selectivity, and the aroma of the obtained aldehyde, even more preferably a normal butyl group or an isobutyl group, and even more preferably an isobutyl group.

[0013] In formula (1), R ２ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom from the viewpoints of conversion rate, selectivity, and the aroma of the resulting aldehyde. １ and R２ is the same as the α,β-unsaturated aldehyde represented by formula (1) that is the raw material.

[0014] The acid value of the α,β-unsaturated aldehyde used in this hydrogenation step is preferably 0.3 to 3.5 mgKOH / g, more preferably 0.3 to 3.2 mgKOH / g, even more preferably 0.3 to 3.0 mgKOH / g, still more preferably 0.5 to 3.0 mgKOH / g, still more preferably 0.7 to 2.8 mgKOH / g, and even more preferably 0.9 to 2.5 mgKOH / g. From the viewpoint of reducing impurities generated from acids (carboxylic acid compounds) that cause the acid value, it is preferable that the acid value of the α,β-unsaturated aldehyde is low. However, in order to fully exert the effects of the present invention, it is preferable that the acid value of the α,β-unsaturated aldehyde is within the above range. The reason why the α,β-unsaturated aldehyde contains acids is not clear, but it is thought to be due to residual acids contained in the alkylbenzaldehyde used as the raw material. Furthermore, it is believed that the carbonyl group is oxidized to a carboxy group by contact with oxygen during the reaction in the production or during storage of the α,β-unsaturated aldehyde.

[0015] As described above, the α,β-unsaturated aldehyde contains an acid component, and the acid component contained in the α,β-unsaturated aldehyde preferably contains at least one selected from the group consisting of a carboxylic acid represented by the following formula (3) and a carboxylic acid represented by the following formula (4): (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２ is a hydrogen atom or a methyl group.

[0016] When the acid component contained in the α,β-unsaturated aldehyde is one of the above compounds, the effects of the present invention can be fully exhibited.

[0017] <Catalyst> The hydrogenation in this step is carried out in the presence of a catalyst containing palladium. The catalyst used in this step contains palladium, and is preferably a supported heterogeneous hydrogenation catalyst in which palladium is supported on a carrier. Examples of the carrier include carbon, silica, alumina, and diatomaceous earth, with alumina being preferred.

[0018] The amount of the catalyst used in this step is 0.01 to 20% by mass, more preferably 0.05 to 15% by mass, even more preferably 0.1 to 10% by mass, still more preferably 0.5 to 8% by mass, even more preferably 0.8 to 5% by mass, and still more preferably 1 to 3% by mass, relative to the α,β-unsaturated aldehyde.

[0019] <Carbonate> The hydrogenation in this step is carried out in the presence of a carbonate. The carbonate is at least one selected from the group consisting of sodium carbonate and potassium carbonate, and from the viewpoints of conversion rate and selectivity, potassium carbonate is preferred. Alternatively, both sodium carbonate and potassium carbonate may be present.

[0020] The amount of the carbonate used during the hydrogenation is 1 to 2 equivalents, preferably 1 to 1.8 equivalents, more preferably 1 to 1.5 equivalents, even more preferably 1 to 1.3 equivalents, still more preferably 1.05 to 1.3 equivalents, still more preferably 1.1 to 1.3 equivalents, and still more preferably 1.15 to 1.3 equivalents, relative to the acid content of the α,β-unsaturated aldehyde. The amount of the carbonate is the total amount of sodium carbonate and potassium carbonate. The amount of the carbonate is the molar amount of the carbonate relative to the molar amount of the acid content of the α,β-unsaturated aldehyde calculated by the following formula. In other words, "the amount of the carbonate is 1 to 2 equivalents relative to the acid content of the α,β-unsaturated aldehyde" means "the total molar amount of sodium carbonate and the molar amount of potassium carbonate is 1 to 2 molar amount relative to the molar amount of the acid content of the α,β-unsaturated aldehyde calculated by the following formula." Acid content (molar amount) contained in α,β-unsaturated aldehyde=acid value of α,β-unsaturated aldehyde (mg KOH / g) / KOH molecular weight (g / mol) / 1000×mass of α,β-unsaturated aldehyde (g)

[0021] As described above, the reason why the use of a specific amount of a specific carbonate during the hydrogenation of the α,β-unsaturated aldehyde allows the target aldehyde to be obtained at a high conversion rate and high selectivity is not clear, but it is thought to be as follows: When the acid content and carbonate contained in the α,β-unsaturated aldehyde are present in amounts within the above ranges, the pH of the reaction solution changes, which affects catalytic activity, and the target aldehyde is obtained at a high conversion rate and high selectivity.

[0022] <Reaction conditions for hydrogenation step> The hydrogen pressure in the hydrogenation step is preferably 0.1 to 5 MPaG, more preferably 0.5 to 2 MPaG, even more preferably 0.6 to 1.8 MPaG, still more preferably 0.7 to 1.5 MPaG, and even more preferably 0.8 to 1.2 MPaG. Note that "G" in "MPaG" indicates gauge pressure. When the hydrogen pressure in the hydrogenation step is within the above range, the reaction rate is high and side reactions due to excessive hydrogenation are suppressed, which is preferable.

[0023] The temperature in the hydrogenation step is preferably 20 to 150° C., more preferably 30 to 100° C., even more preferably 40 to 90° C., still more preferably 50 to 80° C., and still more preferably 50 to 70° C. When the temperature in the hydrogenation step is within the above range, the reaction rate is high and side reactions due to excessive hydrogenation and aldol reaction are suppressed, which is preferable.

[0024] The reaction time in the hydrogenation step is not particularly limited, but is preferably 3 minutes or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and is preferably 24 hours or less, more preferably 12 hours or less, even more preferably 8 hours or less.

[0025] The hydrogenation reaction may be carried out in the presence of a solvent. The solvent to be used is not particularly limited as long as it does not inhibit the hydrogenation reaction, but is preferably a hydrocarbon solvent, more preferably an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon, and even more preferably an aliphatic hydrocarbon. Examples of aliphatic hydrocarbons include pentane, hexane, isopentane, heptane, octane, and isooctane, with heptane being preferred. Examples of alicyclic hydrocarbons include cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane. Examples of aromatic hydrocarbons include benzene, toluene, ethylbenzene, and xylene. These may be used alone or in combination of two or more.

[0026] The method for purifying the target aldehyde represented by formula (2) from the solution after completion of the reaction is not particularly limited, and any known method may be appropriately selected and used. Specific examples include filtration, chromatography, distillation purification, etc., and the target aldehyde with high purity can be obtained by appropriately combining these methods for purification.

[0027] [Step of Calculating the Amount of Acid Content] In the hydrogenation step in the aldehyde production method of the present invention, hydrogenation is performed in the presence of 1 to 2 equivalents of a carbonate relative to the acid content contained in the α,β-unsaturated aldehyde. Therefore, the acid content contained in the α,β-unsaturated aldehyde is important. This step is a step of determining the amount of acid content contained in the α,β-unsaturated aldehyde prior to the hydrogenation step. That is, this step is a step of measuring the acid value of the α,β-unsaturated aldehyde used in the hydrogenation step and calculating the amount of acid content contained in the α,β-unsaturated aldehyde. Preferably, the aldehyde production method of the present invention further includes a step of measuring the acid value of the α,β-unsaturated aldehyde used in the hydrogenation step and calculating the amount of acid content contained in the α,β-unsaturated aldehyde.

[0028] The acid value of the α,β-unsaturated aldehyde can be determined by neutralization titration, more specifically, by measurement according to JIS K 0070:1992. The amount of acid contained in the α,β-unsaturated aldehyde is then calculated from the acid value. This can be determined by converting the acid value obtained by the above method into the number of moles of carboxylic acid. By having the above steps, the amount of acid contained in the α,β-unsaturated aldehyde can be accurately determined, and by carrying out the subsequent hydrogenation step, the target aldehyde can be obtained with high conversion and high selectivity.

[0029] [Aldol Condensation Step (Production of α,β-Unsaturated Aldehyde)] The α,β-unsaturated aldehyde represented by formula (1) can be suitably used as a raw material regardless of the method used to obtain it, but one produced by the following method is preferred. That is, in addition to the hydrogenation step, the production method of the present invention preferably includes an aldol condensation step in which an alkylbenzaldehyde and acetaldehyde or propionaldehyde are subjected to aldol condensation to obtain the α,β-unsaturated aldehyde represented by formula (1). The acid value of the alkylbenzaldehyde is preferably 0.05 to 1.0 mgKOH / g.

[0030] The alkylbenzaldehyde used in this step serves as a raw material for the target α,β-unsaturated aldehyde represented by formula (1). Therefore, the alkylbenzaldehyde is a 4-alkylbenzaldehyde. The alkyl group of the alkylbenzaldehyde is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 2 to 4 carbon atoms, still more preferably an alkyl group having 3 to 4 carbon atoms, and even more preferably an alkyl group having 4 carbon atoms. More specifically, examples of the alkyl group of the alkylbenzaldehyde include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a normal pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a 3-pentyl group, a neopentyl group, a normal hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, and a neohexyl group, and preferably a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, or a sec-butyl group.

[0033] The alkylbenzaldehyde used in this step may be one produced by any method, and examples of its production include a method using a formylation reaction in which an alkylbenzene is reacted with carbon monoxide.

[0031] The acid value of the alkylbenzaldehyde used in this step is preferably 0.05 to 1.0 mgKOH / g, more preferably 0.05 to 0.8 mgKOH / g, even more preferably 0.05 to 0.7 mgKOH / g, still more preferably 0.06 to 0.6 mgKOH / g, even more preferably 0.07 to 0.5 mgKOH / g, and even more preferably 0.08 to 0.3 mgKOH / g. From the viewpoint of reducing impurities generated from the acid content (carboxylic acid compound) that causes the acid value, it is preferable that the acid value of the alkylbenzaldehyde is low. However, in order to fully exert the effects of the present invention, it is preferable that the acid value of the alkylbenzaldehyde is within the above range. Note that the reason why the alkylbenzaldehyde contains acid content is not clear, but it is thought that this is because the carbonyl group moiety is oxidized to a carboxy group upon contact with oxygen during the reaction during production or during storage of the alkylbenzaldehyde.

[0032] In this step, acetaldehyde or propionaldehyde is used, but acetaldehyde is preferred from the viewpoints of the conversion rate and selectivity when obtaining the aldehyde represented by formula (2) and the aroma of the aldehyde represented by formula (2).

[0033] The aldol condensation reaction in this step preferably uses a basic compound as a catalyst. Examples of basic compounds used as catalysts include sodium hydroxide, potassium hydroxide, sodium bicarbonate, and mixtures thereof. The amount of the basic compound is preferably 0.05 mol or more, more preferably 0.1 mol or more, and even more preferably 0.2 mol or more, and is preferably 3 mol or less, more preferably 1 mol or less, and even more preferably 0.5 mol or less, per mol of the alkylbenzaldehyde raw material.

[0034] The amount of acetaldehyde or propionaldehyde added is preferably 0.5 mol or more, more preferably 0.8 mol or more, and preferably 1.5 mol or less, more preferably 1.1 mol or less, relative to 1 mol of the alkylbenzaldehyde raw material. The addition of acetaldehyde or propionaldehyde is preferably carried out gradually or continuously over a period of time, for example, by dropwise addition.

[0035] The aldol condensation reaction in this step is preferably carried out in a solvent. Examples of the solvent include various water-miscible organic solvents, and specific preferred examples include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, tert-butanol, allyl alcohol, ethylene glycol, propylene glycol, and diethylene glycol, with methanol, ethanol, 1-propanol, 2-propanol, tert-butanol, ethylene glycol, propylene glycol, and diethylene glycol being more preferred.

[0036] The reaction temperature in the aldol condensation reaction of this step is not particularly limited, but from the viewpoint of reaction rate, it is preferably −10° C. or higher, more preferably 0° C. or higher, and from the viewpoint of suppressing side reactions, it is preferably 40° C. or lower, more preferably 30° C. or lower, and even more preferably 25° C. or lower. The reaction time is not particularly limited as long as the condensation is sufficiently carried out, but is preferably 10 minutes or longer, more preferably 30 minutes or longer, even more preferably 1 hour or longer, and preferably 24 hours or shorter, more preferably 12 hours or shorter, even more preferably 6 hours or shorter, and even more preferably 4 hours or shorter.

[0037] The reaction can be stopped by neutralization, for example, by adding an acid such as acetic acid.

[0038] The method for isolating the α,β-unsaturated aldehyde represented by formula (1) from the solution after completion of the reaction is not particularly limited, and may be an appropriate combination of separation and extraction procedures and distillation purification. For example, a low-polarity or non-polar organic solvent is added to the solution after completion of the reaction to transfer the aldehyde mixture to an oil phase, and the resulting oil phase is dried, for example, with magnesium sulfate, followed by filtration to obtain a filtrate, which is then concentrated and further purified by distillation to isolate the α,β-unsaturated aldehyde.

[0039] The present invention will be specifically described based on the following examples, but the present invention is not limited to these examples.

[0040] [Analysis and Evaluation] <Purity, Conversion Rate, and Selectivity> The purity of the raw material was calculated from the area % (area %) of the chromatogram (GC) obtained by the following gas chromatography analysis. The conversion rate was calculated by converting the area % (area %) of the chromatogram (GC) obtained by the following gas chromatography analysis into a molar amount using the following formula: Conversion rate (mol %) = 100 - [molar amount of 3-(4-alkylphenyl)propenal in the product] / [molar amount of 3-(4-alkylphenyl)propenal in the feedstock] × 100 The 3-(4-alkylphenyl)propanal selectivity was calculated by converting the area % (area %) of the chromatogram (GC) obtained by the following gas chromatography analysis into a molar amount using the following formula. 3-(4-Alkylphenyl)propanal selectivity (mol %)=[molar amount of 3-(4-alkylphenyl)propanal in the product] / ([molar amount of 3-(4-alkylphenyl)propenal in the feed]×conversion / 100) 3-(4-Alkylphenyl)propanol selectivity was calculated by converting the area % (area %) of a chromatogram (GC) obtained by the following gas chromatography analysis into a molar amount and using the following formula: 3-(4-Alkylphenyl)propanol selectivity (mol %)=[molar amount of 3-(4-alkylphenyl)propanol in the product] / ([molar amount of 3-(4-alkylphenyl)propenal in the feed]×conversion / 100)

[0041] (Gas Chromatography Analysis) For the gas chromatography analysis, a gas chromatograph (GC-2010Plus, manufactured by Shimadzu Corporation) was used. As a capillary column, an HR-1 (inner diameter 0.32 mmφ, film thickness 0.50 μm, length 30 m) manufactured by Shinwa Kako Co., Ltd. was used. The temperature increase program was to increase the temperature from 100°C to 280°C at a rate of 5°C / min and hold the temperature for 30 minutes.

[0042] <Acid value> Measured according to the neutralization titration method (JIS K 0070:1992).

[0043] <Amount of Carbonate> The acid content (molar amount) contained in the α,β-unsaturated aldehyde was calculated from the acid value using the following formula. Table 1 shows the amount (molar amount) of the carbonate (potassium carbonate or sodium carbonate) used in the examples and comparative examples relative to the acid content in terms of equivalents (molar equivalents). Acid content (molar amount) contained in α,β-unsaturated aldehyde = acid value of α,β-unsaturated aldehyde (mg KOH / g) / molecular weight of KOH (g / mol) / 1000 × mass of α,β-unsaturated aldehyde (g).

[0044] [Production of 3-(4-Alkylphenyl)propenal] Production Example 1 (Production of 3-(4-isobutylphenyl)propenal (1)) Methanol (600.0 g), 50% sodium hydroxide solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 71.0 g), and isobutylbenzaldehyde (manufactured by Mitsubishi Gas Chemical Co., Ltd., acid value 0.2 mgKOH / g, 600.0 g) were charged into a 2000 mL round-bottom flask equipped with a stirrer, a thermometer, and a dropping funnel, and after cooling to 0°C with stirring, acetaldehyde (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 172.0 g) was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was maintained at 0°C for 3 hours to complete the reaction. After neutralization by adding acetic acid (53.3 g), water and heptane were added, and the mixture was shaken and separated, and the aqueous phase was separated and removed. Next, the heptane was distilled off to obtain a crude intermediate. This crude intermediate was distilled (130-131°C / 2 torr) in a distillation column with two theoretical plates to obtain 3-(4-isobutylphenyl)propenal (1) (195 g, purity 99.1 G Carea%, acid value 0.8 mg KOH / g).

[0045] Production Example 2 (Production of 3-(4-isobutylphenyl)propenal (2)) A 2000 mL round-bottom flask equipped with a stirrer, a thermometer, and a dropping funnel was charged with methanol (600.0 g), a 50% sodium hydroxide solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 71.0 g), and isobutylbenzaldehyde (manufactured by Mitsubishi Gas Chemical Co., Ltd., acid value 0.1 mgKOH / g, 600.0 g). After cooling to 0°C with stirring, acetaldehyde (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 172.0 g) was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was maintained at 0°C for 3 hours to complete the reaction. After neutralization by adding acetic acid (53.3 g), water and heptane were added, the mixture was shaken, and the liquids were separated to separate and remove the aqueous phase. Next, the heptane was distilled off to obtain a crude intermediate. This crude intermediate was distilled (130-131°C / 2 torr) in a distillation column with two theoretical plates to obtain 3-(4-isobutylphenyl)propenal (2) (206.0 g, purity 98.8 G Carea%, acid value 0.7 mg KOH / g).

[0046] A crude intermediate was obtained in the same manner as in Production Example 1, except that normal butylbenzaldehyde (manufactured by Mitsubishi Gas Chemical Co., Inc., acid value 0.6 mgKOH / g, 600.0 g) was used instead of isobutylbenzaldehyde. This crude intermediate was distilled (132 to 134°C / 1 torr) in a distillation column with two theoretical plates to obtain 3-(4-normal butylphenyl)propenal (200.5 g, purity 98.5 G Carea%, acid value 2.0 mgKOH / g).

[0047] [Production of 3-(4-Alkylphenyl)propanal] Example 1 (Production of 3-(4-isobutylphenyl)propanal) 3-(4-isobutylphenyl)propenal (1) (80.0 g, purity 99.1 G Carea%, acid value 0.8 mg KOH / g) obtained in Production Example 1, a 5% aqueous sodium carbonate solution (3.2 g), and a 5% palladium-alumina catalyst (manufactured by N.E. Chemcat Corporation, 1.6 g) were charged into a 200 mL stainless steel autoclave equipped with a magnetic induction stirrer and capable of controlling the internal temperature using a jacket, and a hydrogenation reaction was carried out at 60°C and a hydrogen pressure of 1.0 MPa until hydrogen absorption ceased. The reaction liquid was filtered to remove the catalyst, and heptane and water were added and the mixture was shaken, followed by liquid separation, and the aqueous phase was separated and removed. Next, the heptane was distilled off to obtain a product containing 3-(4-isobutylphenyl)propanal. The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained products are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-isobutylphenyl)propenal is also shown in Table 1.

[0048] Example 2 (Production of 3-(4-isobutylphenyl)propanal) A product containing 3-(4-isobutylphenyl)propanal was obtained in the same manner as in Example 1, except that the 5% aqueous sodium carbonate solution (3.2 g) in Example 1 was changed to a 5% aqueous potassium carbonate solution (3.2 g). The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained product are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-isobutylphenyl)propenal is also shown in Table 1.

[0049] Example 3 (Production of 3-(4-isobutylphenyl)propanal) A product containing 3-(4-isobutylphenyl)propanal was obtained in the same manner as in Example 2, except that the 3-(4-isobutylphenyl)propenal (1) (80.0 g, purity 99.1 G Carea%, acid value 0.8 mg KOH / g) used in Example 2 was replaced with 3-(4-isobutylphenyl)propenal (2) (80.0 g, purity 98.8 G Carea%, acid value 0.7 mg KOH / g) obtained in Production Example 2. The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained product are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-isobutylphenyl)propenal is also shown in Table 1.

[0050] Example 4 (Production of 3-(4-normal butylphenyl)propanal) 3-(4-normal butylphenyl)propenal obtained in Production Example 3 (80.0 g, purity 98.5 G Carea%, acid value 2.0 mgKOH / g), 15% aqueous potassium carbonate solution (3.2 g), and 5% palladium-alumina catalyst (manufactured by N.E. Chemcat Corporation, 1.6 g) were charged into a 200 mL stainless steel autoclave equipped with a magnetic induction stirrer and capable of controlling the internal temperature with a jacket, and a hydrogenation reaction was carried out at 60°C and a hydrogen pressure of 1.0 MPa until hydrogen absorption ceased. The reaction liquid was filtered to remove the catalyst, and heptane and water were added, followed by shaking and liquid separation, and the aqueous phase was separated and removed. Next, the heptane was distilled off to obtain a product containing 3-(4-normal butylphenyl)propanal. The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained products are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-normal butylphenyl)propenal is also shown in Table 1.

[0051] Comparative Example 1 (Production of 3-(4-normal butylphenyl)propanal) A product containing 3-(4-normal butylphenyl)propanal was obtained in the same manner as in Example 4, except that the 15% aqueous potassium carbonate solution (3.2 g) in Example 4 was changed to a 5% aqueous potassium carbonate solution (3.2 g). The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained product are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-normal butylphenyl)propenal is also shown in Table 1.

[0052] Comparative Example 2 (Production of 3-(4-normal butylphenyl)propanal) A product containing 3-(4-normal butylphenyl)propanal was obtained in the same manner as in Example 4, except that the 15% aqueous potassium carbonate solution (3.2 g) in Example 4 was changed to a 7.5% aqueous potassium carbonate solution (3.2 g). The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained product are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-normal butylphenyl)propenal is also shown in Table 1.

[0053] Comparative Example 3 (Production of 3-(4-normal butylphenyl)propanal) A product containing 3-(4-normal butylphenyl)propanal was obtained in the same manner as in Example 4, except that the 15% aqueous potassium carbonate solution (3.2 g) in Example 4 was changed to a 5% aqueous sodium carbonate solution (47.7 g). The conversion rate, 3-(4-alkylphenyl)propanal selectivity, and 3-(4-alkylphenyl)propanol selectivity of the obtained product are shown in Table 1. The amount of carbonate relative to the acid content contained in 3-(4-normal butylphenyl)propenal is also shown in Table 1.

[0054]

[0055] The results in Table 1 show that the aldehyde obtained by the production method of the Examples has a high conversion rate, a high selectivity for the target product, 3-(4-alkylphenyl)propanal, and a low selectivity for the by-product, 3-(4-alkylphenyl)propanol, and therefore the target aldehyde, 3-(4-alkylphenyl)propanal, can be obtained with high purity and in high yield. This shows that the production method of the present invention can obtain the target aldehyde with high conversion rate and high selectivity. Therefore, the production method of the present invention is useful as a method for producing aldehydes used as fragrances.

Claims

1. A method for producing an aldehyde, comprising a hydrogenation step of hydrogenating an α,β-unsaturated aldehyde represented by the following formula (1) in the presence of a palladium-containing catalyst and a carbonate to obtain an aldehyde represented by the following formula (2), wherein the amount of the carbonate is 1 to 2 equivalents relative to the acid content of the α,β-unsaturated aldehyde, and the carbonate is at least one selected from the group consisting of sodium carbonate and potassium carbonate. (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２ is a hydrogen atom or a methyl group.

2. R ２ The method for producing an aldehyde according to claim 1, wherein is a hydrogen atom.

3. R １ The method for producing an aldehyde according to claim 1 or 2, wherein is an isobutyl group or a normal butyl group.

4. The method for producing an aldehyde according to any one of claims 1 to 3, wherein the α,β-unsaturated aldehyde used in the hydrogenation step has an acid value of 0.3 to 3.0 mgKOH / g.

5. The method for producing an aldehyde according to any one of claims 1 to 4, wherein the acid component contained in the α,β-unsaturated aldehyde includes at least one selected from the group consisting of a carboxylic acid represented by the following formula (3) and a carboxylic acid represented by the following formula (4): (In the formula, R １ is an alkyl group having 1 to 6 carbon atoms, and R ２ is a hydrogen atom or a methyl group.

6. The method for producing an aldehyde according to any one of claims 1 to 5, wherein the carbonate is potassium carbonate.

7. The method for producing an aldehyde according to any one of claims 1 to 6, wherein the hydrogen pressure in the hydrogenation step is 0.5 to 2 MPaG.

8. The method for producing an aldehyde according to any one of claims 1 to 7, wherein the temperature in the hydrogenation step is 40 to 90°C.

9. A method for producing an aldehyde according to any one of claims 1 to 8, comprising an aldol condensation step of subjecting an alkylbenzaldehyde to aldol condensation with acetaldehyde or propionaldehyde to obtain an α,β-unsaturated aldehyde represented by formula (1), wherein the alkylbenzaldehyde has an acid value of 0.05 to 1.0 mgKOH / g.

10. The method for producing an aldehyde according to any one of claims 1 to 9, further comprising a step of measuring the acid value of the α,β-unsaturated aldehyde used in the hydrogenation step and calculating the amount of acid contained in the α,β-unsaturated aldehyde.

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