JP2015110543A - Benzoic acid production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, for production of benzoic acid, which is an important compound in synthesizing an organic compound, a novel synthesis method and an industrially suitable production method using ingredients originating from non-fossil resources as main ingredients.SOLUTION: In the benzoic acid production method, an ingredient represented by the general formula (I) in the figure is subjected to liquid phase oxidation with a molecular oxygen-containing gas in the presence of a catalyst comprising a bromine compound and a transition metal compound. (In the formula, R represents a carboxy group, an alkoxycarbonyl group or an amide group.)

Description

The present invention relates to a method for producing benzoic acid.

  Benzoic acid is widely used in antiseptics, aniline dyes, pharmaceuticals, fragrances, resin coating materials and the like. The production method of benzoic acid includes (1) a method of treating benzoyl chloride with a hot solution of salashi powder, (2) a method of directly oxidizing toluene with manganese persulfate or manganese dioxide, and (3) removal from phthalic acid. A method of producing by a carbonic acid reaction is common.

Benzoic acid is an important organic compound, and several attempts have been made to synthesize it efficiently. In particular, as a production method using a raw material having a similar skeleton of phenyllactic acid, for example, a compound represented by the following general formula (II) is synthesized in air in the presence of sodium hydride to synthesize benzoic acid in a high yield. A method has been reported (see Non-Patent Document 1).

いずれの反応もα位にヒドロキシル基を有する化合物が原料であり、選択的にα位を酸化しやすいと考えられる。 In addition, a method of synthesizing benzoic acid in a high yield by adding 2-chloroanthraquinone to the compound represented by the following general formula (III) and oxidizing in air has been reported (Non-patent Document 2). reference).

In any reaction, a compound having a hydroxyl group at the α-position is a raw material, and it is considered that the α-position is easily oxidized selectively.

Further, as an example in which the benzyl position (α position) is other than the hydroxyl group, a method of synthesizing benzoic acid in a high yield from a compound represented by the following general formula (IV) using Bi (III) mandelic acid as a catalyst. It has been reported (see Non-Patent Document 3).

  This synthesis example also has a substituent at the α-position, and the α-position is considered to be easily oxidized selectively.

  However, all of these methods use compounds represented by the above general formulas (II), (III), and (IV), that is, compounds derived from petroleum resources as raw materials, and in the process of industrially producing benzoic acid, A large amount of heat and carbon dioxide are emitted, which may contribute to global warming.

  On the other hand, based on the idea of using non-fossil resources, a method of converting glucose derived from renewable resources into benzoic acid by a microorganism is known (for example, see Patent Document 1).

  However, in order to industrially synthesize benzoic acid in large quantities using the method described in Patent Document 1 using microorganisms, there are problems such as the fact that the concentration cannot be increased and the culture takes a long time.

JP 2011-83288 A

Sunhae kang, 4 others, Tetrahedron Letters, 2011, 52, p. 502-504 Yoko Matsusaki, 4 others, Synlett, 2012, 23, p. 2059-2063 Veronique LE Boisselier, 3 others, Tetrahedron, 1995, 51, p. 4991-4996

  In recent years, there has been a strong demand for the creation of an organic compound production method that does not depend on petroleum resources.

  An object of the present invention is to provide an industrially suitable production method using a novel synthetic method and a raw material derived from a non-fossil resource as a main raw material in the production of benzoic acid which is an important compound in the synthesis of an organic compound. Is an issue.

  As a result of intensive studies in order to solve the above problems, the present inventors have found the present invention.

（式中Ｒはカルボキシ基、アルコキシカルボニル基またはアミド基を示す。） That is, the present invention is a method for producing benzoic acid by oxidizing a compound represented by the following general formula (I) with a molecular oxygen-containing gas in the presence of a catalyst comprising a transition metal compound and a bromine compound. .

(In the formula, R represents a carboxy group, an alkoxycarbonyl group or an amide group.)

  According to the production method of the present invention, even if the compound does not have a substituent at the α-position (benzyl position), the α-position can be selectively selected by air oxidation if the compound has a hydroxyl group at the β-position (phenethyl position). It can be oxidized and benzoic acid can be produced in an efficient industrially suitable manner.

  According to the present invention, for example, phenyl lactic acid is synthesized by a known technique from L-phenylalanine produced by fermentation from a sugar source, or phenyl lactic acid is produced by fermentation, and then the phenyl lactic acid is oxidized by air. Benzoic acid can be produced. Therefore, it is possible to manufacture benzoic acid by an efficient industrially suitable method using raw materials derived from non-fossil resources.

  A carboxy group is preferable as R in the general formula (I). The transition metal compound is preferably at least one transition metal selected from manganese, tungsten, molybdenum, chromium, vanadium, cobalt, and cerium, or a compound thereof. Further, the liquid phase oxidation is preferably performed at a reaction pressure of 0 to 6 MPa.

  Hereinafter, the present invention will be described in detail.

（式中、Ｒはカルボキシ基、アルコキシカルボニル基またはアミド基を示す。） In the production method of the present invention, a compound represented by the following general formula (I) is used as a starting material.

(In the formula, R represents a carboxy group, an alkoxycarbonyl group or an amide group.)

  In the general formula (I), R is a carboxy group, an alkoxycarbonyl group or an amide group, preferably a carboxy group. Since the compound represented by the general formula (I) has a hydroxyl group at the β-position (phenethyl position), the α-position can be selectively oxidized by air oxidation, and benzoic acid can be produced efficiently. For this reason, it is expected that benzoic acid is efficiently produced even when R is an alkyl group or a phenyl group.

  The compound represented by the general formula (I) where R is a carboxy group is phenyllactic acid.

The alkoxycarbonyl group is represented by a general formula —CO—OR ¹ (R ¹ represents an alkyl group), and examples thereof include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group. The number of carbon atoms of the alkoxycarbonyl group is preferably 2 to 7, more preferably 2 to 4. Examples of the compound represented by the general formula (I) in which R is an alkoxycarbonyl group include 3-phenyl methyl lactate, 3-phenyl ethyl lactate, 3-phenyl propyl lactate, and 3-phenyl butyl lactate.

The amide group is represented by the general formula —CO—NR ² R ³ (R ² and R ³ each independently represents hydrogen or an alkyl group). R ² and R ³ are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms. Examples of the amide group R include an amide group (—CONH ₂ ), a methylamide group, an ethylamide group, a propylamide group, a dimethylamide group, a methylethylamide group, and a diethylamide group. Examples of the compound represented by the general formula (I) in which R is an amide group include 2-hydroxy-3-phenylpropionamide, N-methyl-2-hydroxy-3-phenylpropionamide, N, N-dimethyl- Examples include 2-hydroxy-3-phenylpropionamide.

  The alkyl group is preferably an alkyl group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, and a tert-butyl group. Examples of the compound represented by the general formula (I) in which R is an alkyl group include 1-phenyl-2-propanol, 1-phenyl-2-butanol, 1-phenyl-2-heptanol, and 1-phenyl-2- Examples include hexanol.

  Moreover, the compound represented by the said general formula (I) whose R is a phenyl group is 1, 2- diphenylethanol.

  Among the compounds represented by the general formula (I), it is preferable to use phenyllactic acid as a starting material. Phenyllactic acid can be produced by a known technique using L-phenylalanine, which is generally produced by fermentation from a sugar source derived from a non-fossil resource.

  In the production method of the present invention, the solvent used for the reaction includes organic acids such as formic acid, acetic acid, propionic acid and butyric acid, halogen-containing solvents such as carbon tetrachloride, dichloromethane, chloroform, 1,2-dichloroethane and chlorobenzene, methanol Alcohols such as ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, acetonitrile Nitriles such as tetrahydrofuran, cyclopentyl methyl ether, diethyl ether, and other ethers, acetone, acetylacetone, ethyl methyl ketone, 3-heptanone, 4-heptanone, 2-pentanone, 3-pen Non-ketones such as N, N′-dimethylformamide, dimethyl sulfoxide, hexamethylphosphotriamide, and water, preferably organic acids such as formic acid, acetic acid, propionic acid, butyric acid, methanol, ethanol, propanol, Examples include alcohols such as isopropanol, butanol, isobutanol, sec-butanol and tert-butanol, ethers such as tetrahydrofuran, cyclopentylmethyl ether and diethyl ether, and water, and more preferred is acetic acid.

  The production method of the present invention is characterized in that benzoic acid is produced by subjecting the above-mentioned starting material to liquid phase oxidation with a molecular oxygen-containing gas in the presence of a catalyst comprising a transition metal compound and a bromine compound.

  The amount of the transition metal compound used is preferably 0.5 wt% or less with respect to the solvent used, in terms of transition metal. Use of an amount exceeding this increases the labor and cost of separating the transition metal compound from the product.

  As the transition metal used as the transition metal compound, a metal selected from Group 5 to 10 is preferably used, and a plurality of types may be used in combination in order to increase the catalytic activity. Preferably, at least one selected from manganese, tungsten, molybdenum, chromium, vanadium, cobalt, and cerium is used. More preferably, it is cobalt. As the transition metal compound, the above-described transition metals and / or compounds of these transition metals can be used. As the transition metal compound, manganese acetate and cobalt acetate are preferable.

  As the bromine compound, inorganic bromine compounds such as hydrogen bromide, hydrobromic acid, alkali metal bromide, and ammonium bromide, and organic bromine compounds such as tetrabromoethane, bromoacetic acid, and benzyl bromide can be used. As the bromine compound, hydrogen bromide and hydrobromic acid are more preferable.

  The weight ratio of the transition metal compound to the bromine compound is preferably 1: 0.1 to 1: 100. More preferably, it is 1: 0.1 to 1:30. More preferably, it is 1: 0.1 to 1:20.

  The oxidation reaction according to the present invention is preferably a liquid phase oxidation reaction, and the reaction is preferably performed at 80 to 250 ° C, more preferably 90 to 200 ° C, and further preferably 150 to 200 ° C. If the reaction temperature is too high, side reactions occur, and if it is too low, the reaction rate is undesirably low.

  In the present invention, a molecular oxygen-containing gas is used as the oxidizing agent. Although pure oxygen or industrial exhaust gas can be used as the molecular oxygen-containing gas, industrially, normal air or a mixed gas of air and industrial exhaust gas is suitable.

  The reaction pressure of the liquid phase oxidation reaction is a gauge pressure and can be in a range between normal pressure (0 MPa) and 6 MPa, preferably 0 to 3 MPa, more preferably 0 to 2 MPa. At this time, it is preferable to control the reaction pressure so that the oxygen concentration in the exhaust gas from the reactor is below the explosion limit concentration.

  The production method of the present invention is characterized in that the reaction is possible even at normal pressure (0 MPa), and it is industrially easy without requiring a special pressure reactor.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

  In the examples, the yield of benzoic acid was measured and quantified by the following method using high performance liquid chromatography (HPLC).

Analytical condition column for high performance liquid chromatography (HPLC): Inertsil ODS-3 (manufactured by GL Sciences Inc.)
Mobile phase: Liquid A 100% acetonitrile (methanol for high performance liquid chromatography)
Liquid B Phosphoric acid aqueous solution (pH 2.3)
Gradient: 0 to 5 minutes B solution / A solution = 10/90
5-30 minutes B solution / A solution = 10/90 → 90/10
30-31 minutes B solution / A solution = 90/10
35 minutes Liquid B / Liquid A = 10/90
Flow rate: 1.0ml
Column temperature: 40 ° C
Detector: UV (210 nm)
Retention time: 17.8 minutes (benzoic acid)
15.8 minutes (phenyl lactic acid)
20.2 minutes (phenylpyruvic acid)
4.7 minutes (phenylalanine)
20.3 minutes (cinnamic acid)

Example 1
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (9.0 mmol) of S-(−)-3-phenyllactic acid, acetic acid 120 g, 0.61 g of cobalt (II) acetate tetrahydrate, 0.031 g of manganese (II) acetate tetrahydrate, 0.84 g of hydrobromic acid (47 to 49% by weight) were added, and the air was added to 200 to 300 mL. Bubbling was started in the liquid at a flow rate of / min.

  Then, it heated up at 90-95 degreeC and stirred for 6 hours, and obtained the reaction liquid as a blue uniform solution.

  When the reaction solution was quantitatively analyzed by HPLC, the production of benzoic acid was confirmed at a yield of 58%.

  Benzoic acid was identified by HPLC, GC and GC-MS.

Example 2
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (9.0 mmol) of S-(−)-3-phenyllactic acid, acetic acid 120 g, 0.61 g of cobalt (II) acetate tetrahydrate, 0.031 g of manganese (II) acetate tetrahydrate, 0.84 g of hydrobromic acid (47 to 49% by weight) were added, and the air was added to 200 to 300 mL. Bubbling was started in the liquid at a flow rate of / min.

  Then, it heated up at 90-95 degreeC and stirred for 6 hours, and obtained the reaction liquid as a blue uniform solution. When the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 57%, which was the same as in Example 1.

  Further, 0.61 g of cobalt (II) acetate tetrahydrate, 0.031 g of manganese acetate (II) tetrahydrate, and 0.84 g of hydrobromic acid (47 to 49% by weight) were added, and 90 to The mixture was stirred at 95 ° C. for 7 hours, and the yield of benzoic acid was 58%.

Example 3
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (9.0 mmol) of S-(−)-3-phenyllactic acid, acetic acid 120 g, 0.61 g of cobalt (II) acetate tetrahydrate, 0.031 g of manganese (II) acetate tetrahydrate, 0.84 g of hydrobromic acid (47 to 49% by weight) were added, and the air was added to 200 to 300 mL. Bubbling was started in the liquid at a flow rate of / min.

  Then, it heated up at 85-90 degreeC and stirred for 6 hours, and obtained the reaction liquid as a blue uniform solution.

  When the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 58%, the same as in Example 1. Even when the reaction temperature was lowered by 5 ° C., the yield did not change.

Example 4
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (9.0 mmol) of S-(−)-3-phenyllactic acid, acetic acid 120 g, cobalt acetate (II) tetrahydrate 1.22 g, manganese acetate (II) tetrahydrate 0.068 g, hydrobromic acid (47 to 49% by weight) 1.68 g are added, and the air is 200 to 300 mL. Bubbling was started in the liquid at a flow rate of / min.

  Then, it heated up at 85-90 degreeC, and stirred for 5 hours, and the reaction liquid was obtained as a blue uniform solution.

  When the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 63%.

  Furthermore, although it stirred at 85-90 degreeC for 2 hours, the yield of benzoic acid did not change with 63%.

Example 5
A 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer, a dropping funnel and an air circulation pump through a flow meter was charged with 100 g of acetic acid, 1.22 g of cobalt (II) acetate tetrahydrate, acetic acid. Manganese (II) tetrahydrate 0.068 g, hydrobromic acid (47-49 wt%) 1.68 g were added, and bubbling was started in the liquid at a flow rate of 200-300 mL / min. The temperature was raised to ° C.

  Thereafter, a solution obtained by dissolving 1.5 g (9.0 mmol) of S-(−)-3-phenyllactic acid in 20 g of acetic acid was added dropwise while maintaining 90 to 95 ° C. over 1.5 hours.

  After completion of dropping, the mixture was stirred at 90 to 95 ° C. for 5 hours to obtain a reaction solution as a blue uniform solution.

  When the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 61%.

Example 6
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(-)-3-phenyllactic acid, 300 g of acetic acid, 1.5 g of cobalt acetate (II) tetrahydrate, manganese acetate (II) 0.085 g of tetrahydrate and 2.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in under a reaction pressure of 1.5 MPa and a reaction temperature of 95 to 100 ° C. for 75 minutes. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, when the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 61%.

Example 7
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(-)-3-phenyllactic acid, 300 g of acetic acid, 1.5 g of cobalt acetate (II) tetrahydrate, manganese acetate (II) 0.085 g of tetrahydrate and 2.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in for 70 minutes under conditions of a reaction pressure of 1.5 MPa and a reaction temperature of 110 to 120 ° C. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, when the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 61%.

Example 8
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(-)-3-phenyllactic acid, 300 g of acetic acid, 1.5 g of cobalt acetate (II) tetrahydrate, manganese acetate (II) 0.085 g of tetrahydrate and 2.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in for 70 minutes under conditions of a reaction pressure of 1.5 MPa and a reaction temperature of 165 to 175 ° C. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, when the reaction solution was quantitatively analyzed by HPLC, the yield of benzoic acid was 74%.

Example 9
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(-)-3-phenyllactic acid, 300 g of acetic acid, 1.5 g of cobalt acetate (II) tetrahydrate, manganese acetate (II) 0.085 g of tetrahydrate and 2.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in for 3 hours under conditions of a reaction pressure of 1.5 MPa and a reaction temperature of 185 to 195 ° C. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, the reaction solution was quantitatively analyzed by HPLC. The yield of benzoic acid was 78%.

Example 10
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(-)-3-phenyllactic acid, 300 g of acetic acid, 1.5 g of cobalt acetate (II) tetrahydrate, manganese acetate (II) 0.085 g of tetrahydrate and 2.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in under a reaction pressure of 1.5 MPa and a reaction temperature of 195 to 200 ° C. for 7 hours. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, the reaction solution was quantitatively analyzed by HPLC. As a result, the yield of benzoic acid was 80%.

Example 11
In a 1 L titanium autoclave equipped with a reflux condenser and a rotating blade stirrer, 10 g (60 mmol) of S-(−)-3-phenyllactic acid, 300 g of acetic acid, 0.76 g of cobalt (II) acetate tetrahydrate, manganese acetate (II) 0.045 g of tetrahydrate and 1.1 g of hydrobromic acid (47 to 49% by weight) were added, and air was blown in for 6 hours under conditions of a reaction pressure of 1.5 MPa and a reaction temperature of 195 to 200 ° C. I let you. During this time, the amount of air blown was adjusted so that the exhaust gas from the autoclave had an oxygen concentration of 11% or less and an exhaust gas flow rate of 0.5 to 2.0 L / min. After cooling, the reaction mixture was quantitatively analyzed by HPLC. The yield of benzoic acid was 77%.

Comparative Example 1
In a 100 mL four-necked flask equipped with a thermometer, condenser, stirrer, and nitrogen balloon, S-(−)-3-phenyllactic acid 0.5 (3.0 mmol), acetic acid 40 g, cobalt acetate (II) tetrahydrate 0.21 g, 0.10 g of manganese (II) acetate tetrahydrate, and 0.28 g of hydrobromic acid (47-49 wt%) were added.

  Then, it heated up at 90-100 degreeC and stirred for 3 hours, and obtained the reaction liquid.

  When the reaction solution was quantitatively analyzed by HPLC, the production of benzoic acid was less than 1%.

Comparative Example 2
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (10.1 mmol) cinnamic acid, 120 g acetic acid, four cobalt acetate (II) Add 0.61 g of hydrate, 0.32 g of manganese (II) acetate tetrahydrate, and 0.84 g of hydrobromic acid (47-49 wt%), and start bubbling with air at a flow rate of 200-300 mL / min. did.

  Then, it heated up at 90-95 degreeC and stirred for 6 hours, and the reaction liquid was obtained.

  The reaction solution was quantitatively analyzed by HPLC, but no benzoic acid was produced and the raw material was recovered.

Comparative Example 3
L-phenylalanine 1.5 g (9.1 mmol), acetic acid 120 g, cobalt acetate (II) were added to a 200 mL four-necked flask equipped with an air introduction line from a thermometer, condenser, stirrer and air circulation pump via a flow meter. Add 0.61 g of tetrahydrate, 0.31 g of manganese (II) acetate tetrahydrate, and 0.84 g of hydrobromic acid (47 to 49% by weight), and bubbling air at a flow rate of 200 to 300 mL / min. Started.

  Then, it heated up at 95-100 degreeC and stirred for 3 hours, and obtained the reaction liquid.

  The reaction solution was quantitatively analyzed by HPLC, but production of benzoic acid was not observed.

Comparative Example 4
To a 200 mL four-necked flask equipped with an air introduction line from a thermometer, a condenser, a stirrer and an air circulation pump via a flow meter, 1.5 g (9.1 mmol) of phenylpyruvic acid, 120 g of acetic acid, cobalt (II) acetate Add 0.61 g of tetrahydrate, 0.31 g of manganese (II) acetate tetrahydrate, and 0.84 g of hydrobromic acid (47 to 49% by weight), and bubbling air at a flow rate of 200 to 300 mL / min. Started.

  Then, it heated up at 95-100 degreeC and stirred for 6 hours, and obtained the reaction liquid as a blue uniform solution.

  When the reaction solution was quantitatively analyzed by HPLC, it was confirmed that benzoic acid was produced at a yield of 10%.

Claims (5)

A method for producing benzoic acid, comprising subjecting a compound represented by the following general formula (I) to liquid phase oxidation with a molecular oxygen-containing gas in the presence of a catalyst comprising a transition metal compound and a bromine compound.

(In the formula, R represents a carboxy group, an alkoxycarbonyl group or an amide group.)   The method for producing benzoic acid according to claim 1, wherein R is a carboxy group.   The benzoic acid production according to claim 1 or 2, wherein the transition metal compound is at least one transition metal selected from manganese, tungsten, molybdenum, chromium, vanadium, cobalt, and cerium, or a compound thereof. Method.   The method for producing benzoic acid according to claim 1, 2 or 3, wherein the liquid phase oxidation is performed at a reaction pressure of 0 to 6 MPa.   3. The production method according to claim 2, wherein phenyl lactic acid obtained by chemical synthesis from L-phenylalanine obtained by fermentation or phenyl lactic acid obtained by fermentation is used as the raw material.