JPH06135895A - Production of glycolic acid ester - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject compound useful as a boiler-cleansing agent, a plating additive, etc., under mild conditions by hydrogenating an oxalic acid diester with hydrogen in the presence of a solid catalyst produced by carrying copper metal and silver metal on a carrier in a gas phase. CONSTITUTION:The method for producing the glycolic acid ester comprises dissolving copper nitrate and silver nitrate in water, adding silica gel for a carrier to the solution, gradually dropping an preliminarily produced ammonium carbonate aqueous solution to the mixture, filtering out the produced precipitates, drying the separated precipitates at 40 deg.C for 12hr, reducing the dried precipitates in a hydrogen flow at 350 deg.C for 2hr, charging the produced solid catalyst comprising the copper metal and the silver metal carried on the carrier into a glass gas phase reaction tube, supplying hydrogen gas and an oxalic acid diester of formula: (COOR)2 (R is 1-6C lower alkyl) into the reaction tube, and simultaneously hydrogenating the oxalate diester at 237 deg.C under ordinary temperature in the gas phase, thus producing the objective glycolic acid ester in high selectively and in high yield.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a glycolic acid ester with a high selectivity and a high yield by subjecting an oxalic acid diester and hydrogen to a gas phase catalytic reaction using a novel solid catalyst. Regarding Glycolic acid ester is extremely useful as a cleaning agent for boilers, an additive for plating, an etching agent, a skin tanning agent, and an intermediate for the production of detergent builders and biodegradable polymers. It is a useful compound.

[0002]

2. Description of the Related Art As a method for producing a glycolic acid ester, as disclosed in Japanese Patent Publication No. 55-29771, US Pat. No. 4,112,245 and German Patent No. 459,603, carbon dioxide is used. A method for catalytically reacting an oxalic acid diester such as diethyl oxalate with hydrogen in the presence of a catalyst obtained from cupric acid and chromic acid is already known. However, in these methods, since this reaction is a sequential reaction, unless the catalyst is improved or the reaction conditions are optimized, the hydrogenation reaction proceeds further and ethylene glycol is produced as a by-product. There is a problem that the selectivity of the acid ester decreases, and the separation and purification of the glyco acid ester becomes complicated accordingly.

Further, since these methods use a copper-chromium-based catalyst as a catalyst, it is necessary to recover chromium from the waste catalyst after use. In that process, chromium is efficiently recovered and discarded. It was extremely difficult to prevent chrome from accommodating sewage and the like. Therefore, from the viewpoint of environmental hygiene, it has been desired to develop a manufacturing method that does not use chromium, which is extremely toxic.

In order to solve the above-mentioned problems, for example, in JP-A-55-40685, reaction conditions are changed in the presence of a catalyst selected from ruthenium, nickel and Raney-nickel to change the oxalic acid diester. Although a reaction product containing a relatively large amount of either ethylene glycol or glycolic acid ester is obtained by carrying out a catalytic reaction of hydrogen glycol with hydrogen, the glycolic acid ester is industrially produced. In order to do so, it is necessary to further increase the reaction rate to improve the selectivity and to carry out the reaction under mild reaction conditions using an inexpensive catalyst. In addition, Japanese Examined Sho 60-4
Japanese Patent No. 5938 discloses a method of carrying out a similar catalytic reaction using a catalyst in which a copper ammine complex is supported on a silica carrier, and Japanese Patent Publication No. 62-37030 discloses a catalyst in which silver or palladium is supported. However, these catalysts have low activity and low selectivity of glyco-acid ester, and are not sufficient for industrial use.

[0005]

As described above, in the known method for producing a glycolic acid ester, the hydrogenation reaction of oxalic acid diester is a sequential reaction, and when the reaction proceeds further, ethylene glycol is produced. However, there is a problem that the selectivity of the glyco-acid ester is lowered due to the side reaction. An object of the present invention is to carry out a hydrogenation reaction of oxalic acid diester with hydrogen under mild reaction conditions in the presence of a novel solid catalyst by a gas phase method which facilitates separation / recovery of a reaction product to give a glyco- An object of the present invention is to provide an industrially suitable method for producing a glycolic acid ester capable of producing a high-selectivity and high-yield acid ester.

[0006]

In order to overcome the above-mentioned problems in the heretofore known methods for producing glycolic acid esters, the present inventors have investigated the gas phase catalytic reaction between oxalic acid diester and hydrogen. As a result of diligent study, it was found that when the gas phase catalytic reaction of oxalic acid diester and hydrogen in the presence of a novel hydrogenation catalyst is carried out, the desired product glyco-acid ester can be obtained with extremely high activity and selectivity. The present invention has been reached by finding out.

That is, the present invention provides a method for producing a glycolic acid ester by hydrogenating an oxalic acid diester with hydrogen in a gas phase, wherein a general formula (COOR) ₂ (where R is a carbon number 1 to 6 represents a lower alkyl group)
In the presence of a solid catalyst in which at least copper metal and silver metal are supported on a carrier, oxalic acid diester represented by
The present invention relates to a method for producing a glycolic acid ester, which comprises synthesizing a glycolic acid ester by hydrogenating a gas phase with hydrogen.

The method of the present invention will be described in detail below. As the oxalic acid diester used in the present invention, it is preferable to use a diester of oxalic acid and a lower aliphatic monovalent alcohol having 1 to 6 carbon atoms. Specific examples thereof include dimethyl oxalate, diethyl oxalate, dipropyl oxalate, dibutyl oxalate, and diamyl oxalate. Particularly, the lower aliphatic monovalent alcohol having 1 to 4 carbon atoms described above is preferable. Oxalic acid diesters of alkanol are preferred, with dimethyl oxalate and diethyl oxalate being most preferred.

The catalyst used in the present invention is a solid catalyst in which at least copper metal and silver metal are supported on a carrier such as silica, alumina, titania, zirconia, diatomaceous earth, zinc oxide, lanthanum oxide, activated carbon, Further, in addition to the copper metal and the silver metal, a solid catalyst supporting a copper compound and / or a silver compound may be used.
The amount of copper metal and silver metal supported is preferably 5 to 50% by weight, and particularly preferably 5 to 30% by weight, in terms of metal, based on the carrier, and silver is preferably 0. 0.01 to 20% by weight, particularly preferably 0.02 to
It is preferably 10% by weight.

Further, the above-mentioned carrier is powder, granular carrier,
Alternatively, a molded product is used, but its size is not particularly limited, and a powder having a particle size of 20 to 100 μm which is usually used, and a granular product having a particle size of 4 to 2 are used.
Those having a mesh size of about 00 mesh and several mm in the case of a molded product are preferably used.

The solid catalyst used in the hydrogenation reaction of the present invention is prepared by preparing an aqueous solution of a copper compound and a silver compound in which water-soluble compounds such as copper and silver sulfates, nitrates, chlorides and complex salts are dissolved. It is prepared by adding the above-mentioned carrier to this, supporting the catalyst component on the carrier by an appropriate method, and then reducing the copper compound and the silver compound supported on the carrier with hydrogen gas or the like.

The method of loading the catalyst component on the carrier does not need to be special, and it is a commonly practiced method, that is,
Impregnation method (immersion adsorption method), kneading method, deposition method, evaporation-drying method,
A coprecipitation method or the like may be used, but a coprecipitation method, an impregnation method, or an evaporation-drying method is preferable because it is simple. The catalyst component is supported by, for example, gradually adding an alkalizing agent such as sodium hydroxide, sodium carbonate, ammonium carbonate, potassium hydroxide or aqueous ammonia to an aqueous solution of a copper compound and a silver compound in which the above carrier is suspended. A precipitation containing a copper compound and a silver compound is deposited on a carrier, and the precipitate in which the copper compound and the silver compound are carried on the carrier is separated by filtration or concentration. The catalyst component may be loaded on the carrier at the same time or sequentially.

To reduce the supported catalyst component, the above-mentioned precipitate is thoroughly washed with water and dried in air at a temperature of, for example, about 120 ° C., and then a general reducing agent such as hydrogen gas or hydrazine is used. However, in the reduction treatment using hydrogen gas, prior to the hydrogenation reaction of the oxalic acid diester,
It is preferable to perform a reduction treatment with a general hydrogen gas at a temperature of 150 to 400 ° C. for a reduction time of 1 to 2 hours to produce a solid catalyst mainly supporting copper metal and silver metal.

In the solid catalyst after the above reduction treatment, the copper compound and / or the silver compound, which has not been sufficiently reduced, together with the copper metal and the silver metal in a small proportion (supported on the carrier). The oxalic acid diester of the present invention is supported even if the residual ratio shown by the ratio of the total amount of the copper compound and the silver compound to the total amount of the metal and metal compound components is 20% by weight or less, particularly 10% by weight or less. There is no hindrance to the hydrogenation reaction, and it can be used as it is as a hydrogenation catalyst. In addition, the solid catalyst of the present invention may support a metal or a metal compound other than copper metal and silver metal as a catalyst component together with copper metal and silver metal.

The solid catalyst prepared by the above-mentioned method and carrying at least copper metal and silver metal is continuously maintained at a high level for the activity of hydrogenation reaction (for example, space-time yield: STY). Since the catalyst has high mechanical strength and does not disintegrate, it can be used stably for a long period of time and is a catalyst suitable for the hydrogenation reaction of the oxalic acid diester of the present invention.

In the present invention, the catalytic reaction between oxalic acid diester and hydrogen is carried out at a reaction temperature of 100 to 300 ° C., preferably 100 to 250 ° C., and a reaction pressure of atmospheric pressure to about 30 kg / cm ^2. It can be carried out under the conditions of.
The molar ratio of hydrogen and oxalic acid diester (hydrogen / oxalic acid diester) introduced into the reaction tube filled with the solid catalyst is preferably 2 to 100, particularly preferably 4 to 50. The contact time is preferably 0.01 to 20 seconds, and more preferably 0.2 to 8 seconds.

Further, in the present invention, hydrogen as a raw material gas and oxalic acid diester are fed to the solid catalyst for hydrogenation after being diluted with a lower alcohol vapor such as methanol or ethanol or an inert gas such as nitrogen gas. It is desirable to be done. Although its composition is not particularly limited from the viewpoint of reaction, for example, oxalic acid diester is obtained by evaporating an alcohol solution of oxalic acid diester having a concentration of 10 to 40% by weight, particularly 15 to 35% by weight. It is preferable that the hydrogen gas is supplied onto the solid catalyst together with the hydrogen gas. At this time, it is preferable to use an alcohol having the same alkyl group as the alkoxy group of the oxalic acid diester.

[0018]

EXAMPLES Next, the method of the present invention will be specifically described with reference to examples and comparative examples, but these do not limit the method of the present invention in any way. Among the reaction conditions in each of the examples and comparative examples, liquid hourly space velocity: LHSV
(G / ml · hr), space velocity: SV (hr ⁻¹ ) and contact time: CT (sec) were calculated by the following formulas, respectively.

[0019]

[Equation 1]

[0020]

[Equation 2]

[0021]

[Equation 3]

In each of the examples and comparative examples, the conversion rate (%) of oxalic acid diester, the selectivity rate (%) of glycolic acid ester, the selectivity rate (%) of ethylene glycol, and the STY of methyl glycolate. Was calculated by the following equation.

[0023]

[Equation 4]

[0024]

[Equation 5]

[0025]

[Equation 6]

[0026]

[Equation 7]

Examples 1 to 4 [Preparation of catalyst] Copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O)
39.2 g and 2.1 g of silver nitrate (AgNO ₃ ) were added to 200 parts of water.
It is dissolved in ml and commercial silica sol (manufactured by Catalyst Kasei:
(Cataroid S30L) 66.6 g was added and stirred.
To this solution, 14.4 g of ammonium carbonate was previously added to 85 parts of water.
The liquid dissolved in ml was slowly added dropwise over 30 minutes while stirring. After completion of dropping, the reaction product was aged for 1.5 hours with stirring, and then the generated precipitate was filtered and separated. The separated precipitate is washed with water and filtered with about 500 ml of water.
Repeated times. Take out the obtained blue-white cake and
It is dried at 40 ° C. for 12 hours to form a carrier (a precursor of a solid catalyst) in which a copper compound and a silver compound are supported on a carrier, and the carrier is further dried at 350 ° C. in a hydrogen stream at 2 ° C. for 2 hours.
After reduction treatment for a period of time, a solid catalyst (average particle diameter: 1 to 2 mm) supporting copper metal and silver metal was prepared.

[Synthesis of Methyl Glycolate] 20 ml of the solid catalyst obtained above was used, and the inner diameter was 20 mm and the length was 700 m.
After being filled in a glass gas-phase reaction tube of m, the reaction tube was installed vertically in an electric furnace and the temperature in the catalyst layer was controlled by heating so that the reaction temperature became the temperature shown in Table 1. From the top of these reaction tubes, the liquid hourly space velocity (LHS
V), space velocity (SV) and contact time (CT) so that the molar ratio of hydrogen and dimethyl oxalate is 12.0 to 12.3 (25) and the solution of dimethyl oxalate and methanol (25 (% By weight dimethyl oxalate in methanol) was fed to the reaction system at the reaction temperature under normal pressure to carry out hydrogenation reaction of dimethyl oxalate, and the reaction product passing through the reaction tube was cooled with ice. Collected in a trap.
From the results of analyzing the obtained collected liquid by gas chromatography, the conversion rate of dimethyl oxalate, the selectivity of glycolic acid ester and the space-time yield (STY), and the selectivity of ethylene glycol were determined, and Table 1 shows the results. Indicated.

Comparative Example 1 [Preparation of catalyst] A catalyst in which a copper ammine complex was supported on a silica carrier was prepared in the same manner as in Examples 8 to 11 described in JP-B-60-45938. Copper nitrate (Cu (NO
The _{3) 2 · 3H 2 O)} 38.0g was dissolved in water 200 ml, the pH about by adding concentrated aqueous ammonia 60ml to 1
As 1 to 12, a deep blue solution containing a copper ammine complex was obtained. To this deep blue solution, 66.6 g of 30 wt% colloidal silica sol was added and stirred at room temperature for several hours, then the temperature was raised to evaporate most of the water, and further at 120 ° C. for 12 hours.
Dried for hours. Then, the dried product was thoroughly washed with water, dried in air at 140 ° C. for 14 hours, and then dried in a hydrogen stream for 35 hours.
Reduction treatment was performed at 0 ° C. for 2 hours to prepare a solid catalyst.

[Synthesis of Methyl Glycolate] Using 10 ml of the solid catalyst obtained above, the liquid hourly space velocity (LHSV), the hourly space velocity (SV) and the contact time (C
In T), hydrogen and a solution of dimethyl oxalate and methanol (25% by weight dimethyl oxalate methanol solution) were supplied to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate was 25.0. While at a reaction temperature of 220 ° C,
The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The results obtained are shown in Table 1.

Comparative Example 2 [Preparation of catalyst] A catalyst in which silver was supported on a silica carrier was prepared in the same manner as in Example 1 described in JP-B-62-37030. 5 g of silver nitrate (AgNO ₃ ) was dissolved in 20 ml of water, and 145 g of 33% colloidal silica was added thereto. Aqueous sodium hydroxide solution (1.24 g of NaOH dissolved in 100 ml of water) was gradually added to this silica suspension, and aging was carried out for 1 hour after completion of the addition, and the resulting precipitate was collected by filtration. Filtered off, substantially AgOH-
The solid consisting of SiO ₂ was washed twice with water and then dried overnight at 140 ° C. to form a support. To 2 g of the thus obtained support, 40 ml of a 3% hydrazine aqueous solution was added, and the mixture was allowed to stand overnight, then the solid matter was collected by filtration, washed with water, and then dried under vacuum at room temperature, and then further 150 to 20.
The catalyst was prepared by drying at 0 ° C.

[Synthesis of Methyl Glycolate] Using 10 ml of the solid catalyst obtained above, the liquid hourly space velocity (LHSV), the hourly space velocity (SV) and the contact time (C
In T), hydrogen and a solution of dimethyl oxalate and methanol (25% by weight dimethyl oxalate methanol solution) were supplied to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate was 25.0. While at a reaction temperature of 249 ° C,
The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The results obtained are shown in Table 1.

Example 5 [Preparation of catalyst] Copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O)
19 g and 2.3 g of silver nitrate (AgNO ₃ ) in 200 m of water
1 and then heated to 75 to 80 ° C., and a commercially available silica sol (manufactured by Catalysis Kasei: Cataloid S30L) 66.
5 g was added and stirred. A solution prepared by previously dissolving 7 g of sodium hydroxide in 200 ml of water was slowly added dropwise to this solution while stirring for 30 minutes. After completion of dropping, the reaction product was aged for 2 hours while stirring, and the generated precipitate was separated by filtration. The separated precipitate is about 500 ml of water,
Washing with water and filtration were repeated twice. The cake thus obtained is taken out and dried at 140 ° C. for 12 hours to form a carrier (a precursor of a solid catalyst) in which a copper compound and a silver compound are supported on a carrier, and further, this carrier is 35 in a hydrogen stream
A reduction treatment was performed at 0 ° C. for 2 hours to prepare a solid catalyst (average particle diameter: 1 to 2 mm) carrying copper metal and silver metal.

[Synthesis of Methyl Glycolate] Using 10 ml of the solid catalyst obtained above, liquid hourly space velocity (LHSV), hourly space velocity (SV) and contact time (C
In T), hydrogen and a solution of dimethyl oxalate and methanol (25% by weight dimethyl oxalate methanol solution) were supplied to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate was 22.1. While at a reaction temperature of 237 ° C,
The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The results obtained are shown in Table 1.

Example 6 [Preparation of catalyst] Copper nitrate (Cu (NO ₃ ) ₂ .3H ₂ O)
19 g and 2.1 g of silver nitrate (AgNO ₃ ) in 200 m of water
After dissolving in 1 and adding 60 ml of 25 wt% ammonia water, 66.5 g of commercially available silica sol (Catalyst Kasei: Cataloid S30L) was added and stirred. The reaction was aged for 1 hour while stirring the solution, then 80-90.
The solution was concentrated in a warm bath at ℃, and the resulting precipitate was washed with about 200 ml of water four times and filtered. The cake obtained is taken out, and 12
After drying at 0 ° C. for 12 hours and further baking at 500 ° C. for 3 hours to form a carrier (a precursor of a solid catalyst) in which a copper compound and a silver compound are supported on a carrier, the carrier is treated with hydrogen. A solid catalyst (average particle diameter: 1 to 2 mm) carrying a copper metal and a silver metal was prepared by reduction treatment at 350 ° C. for 2 hours in an air stream.

[Synthesis of Methyl Glycolate] Using 10 ml of the solid catalyst obtained above, the liquid hourly space velocity (LHSV), the hourly space velocity (SV) and the contact time (C
In T), hydrogen and a solution of dimethyl oxalate and methanol (25% by weight dimethyl oxalate methanol solution) were supplied to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate was 5.65. However, at a reaction temperature of 225 ° C,
The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The results obtained are shown in Table 1.

Example 7 [Preparation of catalyst] Silver nitrate (AgNO ₃ ) in Example 5
Example 5 except that the amount used of 0.0633 g
A catalyst was prepared in the same manner as in. The catalyst supported about 20% by weight of copper and about 0.16% by weight of silver.

[Synthesis of Methyl Glycolate] Using 20 ml of the solid catalyst obtained above, the liquid hourly space velocity (LHSV), the hourly space velocity (SV) and the contact time (C
In T), hydrogen and a solution of dimethyl oxalate and methanol (25% by weight dimethyl oxalate methanol solution) were supplied to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate was 12.3. However, at a reaction temperature of 230 ° C,
The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The results obtained are shown in Table 1.

Example 8 [Synthesis of Ethyl Glycolate] Using 20 ml of the catalyst prepared in the same manner as in Example 1, the dimethyl oxalate in Example 1 was changed to diethyl oxalate, and the liquid space shown in Table 1 was used. Velocity (LHSV), space velocity (SV) and contact time (CT), the molar ratio of hydrogen to diethyl oxalate is 12.
While supplying hydrogen and a solution of diethyl oxalate and ethanol (25 wt% diethyl oxalate in ethanol) to the reaction system at a reaction temperature of 220 ° C.
In Example 1, the hydrogenation reaction of diethyl oxalate is carried out under normal pressure.
I went the same way. The results obtained are shown in Table 1.

Example 9 [Synthesis of butyl glycolate] Using 20 ml of the catalyst prepared in the same manner as in Example 1, the dimethyl oxalate in Example 1 was changed to dibutyl oxalate, and the liquid space shown in Table 1 was used. Velocity (LHSV), space velocity (SV) and contact time (CT), the molar ratio of hydrogen to dibutyl oxalate is 12.
While supplying hydrogen and a solution of dibutyl oxalate and butanol (25 wt% dibutyl oxalate butanol solution) to the reaction system at a reaction temperature of 220 ° C.
In Example 1, the hydrogenation reaction of dibutyl oxalate is carried out under normal pressure.
I went the same way. The results obtained are shown in Table 1.

Example 10 [Synthesis of Methyl Glycolate] Using 20 ml of the catalyst prepared in the same manner as in Example 1, the liquid hourly space velocity (LH
SV), space velocity (SV) and contact time (CT),
While supplying hydrogen, nitrogen, and dimethyl oxalate (dimethyl oxalate containing no methanol) to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate is 12.0, at a reaction temperature of 216 ° C., The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The obtained results are shown in Table 2.

Comparative Example 3 [Synthesis of Methyl Glycolate] Using 10 ml of the catalyst prepared in the same manner as in Comparative Example 1, the liquid hourly space velocity (LH
SV), space velocity (SV) and contact time (CT),
While supplying hydrogen, nitrogen, and dimethyl oxalate (dimethyl oxalate containing no methanol) to the reaction system so that the molar ratio of hydrogen and dimethyl oxalate is 25.0, at a reaction temperature of 220 ° C., The hydrogenation reaction of dimethyl oxalate was carried out under the normal pressure in the same manner as in Example 1. The obtained results are shown in Table 2.

Comparative Example 4 [Synthesis of Methyl Glycolate] Using 10 ml of the catalyst prepared in the same manner as in Comparative Example 2, the liquid hourly space velocity (LH
SV), space velocity (SV) and contact time (CT),
While supplying hydrogen, nitrogen, and a dimethyl oxalate solution (a solution of only dimethyl oxalate containing no methanol) to the reaction system so that the molar ratio of hydrogen to dimethyl oxalate is 25.0, The hydrogenation reaction of dimethyl oxalate was carried out at 249 ° C. under normal pressure in the same manner as in Example 1. The obtained results are shown in Table 2.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

The method of using the novel solid catalyst "solid catalyst in which at least copper metal and silver metal are supported on the carrier" of the present invention is used to produce ethylene glycol as a by-product and a target product by sequential reaction. It is easy to separate and collect reaction products under mild reaction conditions by solving the problems of conventionally known methods for producing glycolic acid ester, such as lowering the selectivity of glycolic acid ester. The hydrogenation reaction of oxalic acid diester with hydrogen can be carried out by a simple gas phase method to produce a glycolic acid ester with high selectivity and high yield.

Claims (1)

[Claims] 1. A method for producing a glycolic acid ester by hydrogenating an oxalic acid diester with hydrogen in a gas phase, wherein a compound represented by the general formula (COOR) ₂ (wherein R in the formula has 1 to 6 carbon atoms): An oxalic acid diester represented by a lower alkyl group) is subjected to a hydrogenation reaction in the gas phase with hydrogen in the presence of a solid catalyst in which at least copper metal and silver metal are supported on a carrier to give a glycolic acid ester. A method for producing a glycolic acid ester, which comprises synthesizing.