KR20230142128A - CATALYTIC COMPOSITION FOR PRODUCING α-HYDROXY ACID AND METHOD OF PRODUCING α-HYDROXY ACID - Google Patents

Abstract

A catalyst composition for producing α-hydroxy acids and a method for producing α-hydroxy acids are disclosed. The catalyst composition for producing α-hydroxy acid includes a catalyst comprising N-heterocyclic carbene and iridium (Ir) bound thereto; and a base; and can promote a process in which an alcohol compound and an ethylene glycol compound react to produce α-hydroxy acid. The α-hydroxy acid production method includes a first step of preparing a reaction solution by dissolving a catalyst containing N-heterocyclic carbene and iridium bound thereto, a base, and an ethylene glycol compound in a liquid alcohol compound; and a second step of heating the reaction solution to react the alcohol compound and the ethylene glycol compound to synthesize α-hydroxy acid.

Description

Catalyst composition for producing α-hydroxy acid and method for producing α-hydroxy acid {CATALYTIC COMPOSITION FOR PRODUCING α-HYDROXY ACID AND METHOD OF PRODUCING α-HYDROXY ACID}

The present invention relates to a catalyst composition for producing α-hydroxy acids and a method for producing α-hydroxy acids.

Developing sustainable and carbon-neutral catalytic processes is important to maintain compound production and consumption processes without increasing carbon emissions. Sustainable processes include those that produce industrially useful α-hydroxy acids.

α-Hydroxy acids are a group of compounds that are industrially useful and valuable as ingredients for cosmetics and the like. In the prior art, glycolic acid, a 2-carbon α-hydroxy acid, and lactic acid, a 3-carbon α-hydroxy acid, are produced by a fermentation process using microorganisms or a chemical process. However, in the prior art, the process for producing α-hydroxy acids using biomass is generally limited to 2-carbon and 3-carbon α-hydroxy acids. Therefore, there is a need to develop a versatile process that can produce α-hydroxy acids of various carbon numbers.

One object of the present invention is to provide a catalyst composition for producing α-hydroxy acids that can produce α-hydroxy acids of various carbon numbers.

Another object of the present invention is to provide a method for producing α-hydroxy acid using the catalyst composition.

The catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention includes a catalyst and a base containing N-heterocyclic carbene and iridium (Ir) bound thereto, and the alcohol compound and the ethylene glycol compound react to produce α -Can promote the process of producing hydroxy acids.

In one embodiment, the catalyst may have any one of the following formulas (I) to (VI).

(Ⅰ)

(Ⅱ)

(Ⅲ)

(Ⅳ)

(Ⅴ)

(Ⅵ)

In one embodiment, the base may include one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), or barium hydroxide (Ba(OH) ₂ ).

The method for producing α-hydroxy acid according to an embodiment of the present invention includes the first step of preparing a reaction solution by dissolving a catalyst containing N-heterocyclic carbene and iridium bound thereto, a base, and an ethylene glycol compound in a liquid alcohol compound. step; and a second step of heating the reaction solution to react the alcohol compound and the ethylene glycol compound to synthesize α-hydroxy acid.

In one embodiment, the reaction in the second step may proceed at 160 to 200 °C for 4 to 24 hours.

In one embodiment, the catalyst may have any one of the following formulas (I) to (VI).

(Ⅰ)

(Ⅱ)

(Ⅲ)

(Ⅳ)

(Ⅴ)

(Ⅵ)

In one embodiment, the concentration of the catalyst in the reaction solution may be 0.01 to 0.1 mol%.

In one embodiment, the base may include one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), or barium hydroxide (Ba(OH) ₂ ).

In one embodiment, the reaction solution contains 1 to 2 equivalents of the base per 1 equivalent of the ethylene glycol compound, and the base can reduce a carbonyl group.

In one embodiment, the catalyst can induce a dehydrogenation reaction of the alcohol compound.

In one embodiment, the alcohol compound may have an alkyl group having 1 to 10 carbon atoms.

In one embodiment, the alcohol compound may include one or more of methanol, ethanol, propanol, butanol, or pentanol.

In one embodiment, the reaction solution may contain 15 to 30 equivalents of the alcohol compound per 1 equivalent of the ethylene glycol compound.

In one embodiment, the α-hydroxy acid synthesized in the second step may have a carbon number of 3 to 12.

In one embodiment, the yield of α-hydroxy acid synthesized in the second step may be 40 to 76%.

In one embodiment, the method for producing α-hydroxy acid further includes a third step of preparing a reaction solution by adding an alcohol compound and an ethylene glycol compound to the reaction solution after the second step is completed, By performing the second step by heating the reaction solution of the third step, the catalyst can be reused in the α-hydroxy acid production method.

The catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention can promote the reaction of producing α-hydroxy acid by reacting an alcohol compound with an ethylene glycol compound, and the catalyst composition can be recovered and reused. there is.

An α-hydroxy acid having 3 or more carbon atoms can be produced through the α-hydroxy acid production method according to an embodiment of the present invention.

Figure 1 is a schematic diagram schematically showing the operation of a catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention.
Figure 2 is a flow chart showing a method for producing α-hydroxy acid according to an embodiment of the present invention.
Figure 3 is a diagram schematically showing how reactants react in a method for producing α-hydroxy acid according to an embodiment of the present invention.
Figure 4 is a diagram showing an example of the route of the α-hydroxy acid production method according to an embodiment of the present invention.
Figure 5 is a flow chart showing a method for producing α-hydroxy acid according to an embodiment of the present invention.
Figures 6 and 7 are diagrams showing experimental results according to an experimental example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention can be subject to various changes and can have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components. In the attached drawings, the dimensions of the structures are enlarged from the actual size for clarity of the present invention.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, or a combination thereof described in the specification, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not exclude in advance the possibility of the existence or addition of steps, operations, components, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

In one aspect, the present invention provides a catalyst composition for producing α-hydroxy acids.

Figure 1 is a schematic diagram schematically showing the operation of a catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention.

Referring to Figure 1, in one aspect of the present invention, the catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention includes a catalyst containing N-heterocyclic carbene and iridium (Ir) bound thereto, and a base. And, it can promote the process in which an alcohol compound and an ethylene glycol compound react to produce α-hydroxy acid.

In the context of this specification, “heterocyclic” means a ring-shaped molecule or functional group having two or more ring elements. The cyclic molecule may contain carbon and nitrogen. Therefore, in the context of this specification, “N-heterocyclic” means a cyclic molecule containing nitrogen and one or more other elements.

In the context of this specification, “carben” means a molecule containing a divalent neutral carbon atom and two unpaired valence electrons or a functional group derived therefrom. Therefore, in the context of the present specification, "N-heterocyclic carbene" refers to a cyclic molecule containing nitrogen and carbon, or a functional group derived therefrom, and a molecule containing a divalent neutral carbon atom and two unpaired valence electrons, or a functional group derived therefrom. It means one functional group.

The catalyst includes N-heterocyclic carbene and iridium (Ir) bound thereto, and is not particularly limited as long as it meets the above definition. In one embodiment, the catalyst may have any one of the following formulas (I) to (VI).

(Ⅰ)

(Ⅱ)

(Ⅲ)

(Ⅳ)

(Ⅴ)

(Ⅵ)

Here, COD refers to 1,5-cyclooctadienyl, CO refers to a carbonyl group, and Cp refers to cyclopentadienyl.

The above formulas (I) to (VI) are non-limiting examples, and the catalyst is not limited thereto.

The type of the base is not particularly limited. In one embodiment, the base may include one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), or barium hydroxide (Ba(OH) ₂ ).

The catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention can promote the reaction of producing α-hydroxy acid by reacting an alcohol compound with an ethylene glycol compound, and the catalyst composition can be recovered and reused. there is.

In another aspect, the present invention provides a method for producing α-hydroxy acids.

Figure 2 is a flow chart showing a method for producing α-hydroxy acid according to an embodiment of the present invention.

Referring to FIG. 2, in another aspect of the present invention, the method for producing α-hydroxy acid according to an embodiment of the present invention includes a catalyst including N-heterocyclic carbene and iridium bound thereto, a base, and an ethylene glycol compound. A first step of preparing a reaction solution by dissolving it in a liquid alcohol compound (S110); and a second step (S120) of heating the reaction solution to react the alcohol compound and the ethylene glycol compound to synthesize α-hydroxy acid.

Figure 3 is a diagram schematically showing how reactants react in a method for producing α-hydroxy acid according to an embodiment of the present invention.

Referring to FIGS. 2 and 3 together, in the synthesis step (S120), the alcohol compound and the ethylene glycol compound react to produce α-hydroxy acid. “Alcohol compound” in the context of this specification is a general term for compounds having a hydroxy group (-OH). Therefore, in the context of the present specification, “main group” may mean the remainder of the alcohol compound to which the hydroxy group is attached. Consequently, “alcohol compound” in the context of this specification is a general term for compounds having a hydroxy group attached to the cycle. Also, “ethylene glycol compounds” in the context of this specification means 1,2-ethanediol and compounds derived therefrom. Referring to Figure 3, as the method for producing α-hydroxy acid according to an embodiment of the present invention progresses, the cycle of the alcohol compound and the 2-carbon chain of the ethylene glycol compound are combined to increase the number of carbon atoms in the cycle of the alcohol compound. Produces increased α-hydroxy acid by 2.

The method for producing α-hydroxy acid according to an embodiment of the present invention may proceed through various routes depending on the reactants and reaction conditions. There may be more than one path. Figure 4 is a diagram showing an example of the route of the α-hydroxy acid production method according to an embodiment of the present invention. The above route is an example of the route along which the method for producing α-hydroxy acid according to an embodiment of the present invention proceeds, and does not limit the scope of the present invention.

Referring to FIG. 4, a dehydrogenation reaction may occur in an alcohol compound and an ethylene glycol compound. “Dehydrogenation reaction” in the context of this specification means a reaction in which two hydrogen atoms bonded to adjacent carbon atoms in the chain of an organic compound are generated and removed in the form of hydrogen gas, and the degree of unsaturation of the chain increases. The reaction can be promoted by a catalyst.

After the dehydrogenation reaction, an aldol reaction may proceed between the dehydrogenation reaction product of the alcohol compound and the dehydrogenation reaction product of the ethylene glycol compound. “Aldol reaction” in the context of this specification means a reaction in which two carbonyl compounds combine to produce a β-hydroxy compound. Therefore, through an aldol reaction, the dehydrogenation reaction product of the alcohol compound and the dehydrogenation reaction product of the ethylene glycol compound combine to produce one β-hydroxy compound.

In the context of the present specification, the Greek letter α, β or γ preceding a functional group refers to a bond site spaced by 1, 2 or 3 bonds from the carbon contained in the carbonyl group to which it is referred, respectively, as will be apparent to those skilled in the art. site). For example, an α-hydroxy group refers to a hydroxy group bonded to a carbon directly bonded to a carbon included in a carbonyl group. As another example, the γ-carbon refers to the carbon in the carbonyl group separated by three bonds.

After the aldol reaction, a dehydration reaction may proceed in the β-hydroxy compound. “Dehydration reaction” in the context of this specification means a reaction in which two hydrogen atoms and one oxygen atom are created and removed in the form of water within or between molecules of an organic compound, as will be apparent to those skilled in the art. In one embodiment, the dehydration reaction removes hydrogen atoms and hydroxy groups each bonded to adjacent carbon atoms in the form of water, and the degree of unsaturation of the bond between adjacent carbon atoms may increase. In one embodiment, the dehydration reaction may occur at a hydrogen atom bonded to the α-carbon and a hydroxy group bonded to the β-carbon of a β-hydroxy compound. As a result of the dehydration reaction, a compound in which a double bond is formed between the α-carbon and the β-carbon may be produced.

After the dehydration reaction, hydrogen transfer may occur in the α, β-double bond compound. “Hydrogen transfer” in the context of the present specification means the process of changing the bonding site of a hydrogen atom within or between molecules, and in particular the process of changing the bonding site of a hydrogen atom within a molecule to produce isomers. In one embodiment, the hydrogen transfer may occur from the hydrogen of the hydroxyl group of the α-carbon to the β-carbon. As a result, a dicarbonyl compound in which a carbonyl group is also formed at the α-site can be produced.

After the hydrogen transfer, a Cannizzaro reaction may proceed in the dicarbonyl compound. "Cannizzaro reaction" in the context of the present specification means a reaction in which two carbonyl groups are reduced to a carboxylic acid and an alcohol, respectively, by the action of a base, as will be apparent to those skilled in the art, wherein the two carbonyl groups It may be a carbonyl group located on one dicarbonyl compound molecule. In one embodiment, the terminal carbonyl group (aldehyde) of the dicarbonyl compound may be reduced to a carboxylic group, and the carbonyl group at the α-site may be reduced to a hydroxy group through Cannizzaro reaction. As a result, α-hydroxy acids may be produced.

The above series of reaction mechanisms are non-limiting mechanisms proposed according to an embodiment of the present invention, and do not limit the scope and spirit of the present invention.

The temperature and time of the reaction system may be selected depending on the type and desired yield of the catalyst, base, alcohol compound, and ethylene glycol compound. In one embodiment, the reaction in the second step (S120) may proceed at 160 to 200 ° C. for 4 to 24 hours. For example, the reaction may proceed at about 180° C. for about 16 hours. For example, the reaction may proceed at about 180° C. for about 4 hours. Considering the yield of the reaction, the process is efficient by minimizing the cost input into the process at the above temperature and reaction time.

The catalyst includes N-heterocyclic carbene and iridium bonded thereto, and is not particularly limited as long as it meets the above definition. In one embodiment, the catalyst may have any one of the following formulas (I) to (VI).

(Ⅰ)

(Ⅱ)

(Ⅲ)

(Ⅳ)

(Ⅴ)

(Ⅵ)

The concentration of the catalyst may be selected depending on the reactants and reaction conditions. In one embodiment, the concentration of the catalyst in the reaction solution may be about 0.01 to 0.1 mol%. By limiting the concentration of the catalyst, the process can be made more efficient by minimizing the reaction time and the cost of using the catalyst.

The type of the base is not particularly limited. In one embodiment, the base may include one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), or barium hydroxide (Ba(OH) ₂ ). For example, the base may be cesium hydroxide. In one embodiment, the reaction solution may contain 1 to 2 equivalents of the base per equivalent of the ethylene glycol compound. The base can reduce the carbonyl group during the second step (S120).

In one embodiment, the catalyst can induce a dehydrogenation reaction of the alcohol.

Referring to Figures 3 and 4, the type of α-hydroxy acid produced through the α-hydroxy acid production method according to an embodiment of the present invention can be determined depending on the cycle of the alcohol. Therefore, the alcohol cycle can be selected depending on the α-hydroxy acid to be produced. In one embodiment, the period may be an alkyl group. In one embodiment, the alcohol compound may have an alkyl group having about 1 to 10 carbon atoms. In one embodiment, the alcohol compound may include one or more of methanol, ethanol, propanol, butanol, or pentanol.

The amount of reactant present in the reaction solution may be selected depending on the ethylene glycol compound, the alcohol compound, and reaction conditions. In one embodiment, the reaction solution may contain 15 to 30 equivalents of the alcohol compound per 1 equivalent of the ethylene glycol compound.

The method for producing α-hydroxy acids provides a general method for producing α-hydroxy acids having 3 or more carbon atoms. As described above, in one embodiment, the alcohol compound may have an alkyl group having about 1 to 10 carbon atoms, and the α-hydroxy acid prepared through the α-hydroxy acid production method by reacting it with an ethylene glycol compound has about It may have 3 to 12 carbon atoms. For example, the α-hydroxy acid synthesized in the second step (S120) may have a carbon number of about 3 to 12.

In one embodiment, the yield of α-hydroxy acid synthesized in the second step (S120) may be about 40 to 76%.

Figure 5 is a flow chart showing a method for producing α-hydroxy acid according to an embodiment of the present invention.

Referring to Figure 5, in the method for producing α-hydroxy acid according to an embodiment of the present invention, after the second step (S120) is completed, an alcohol compound and an ethylene glycol compound are further added to the reaction solution to prepare a reaction solution. It further includes a third step (S130), and the second step (S120) is performed by heating the reaction solution of the third step (S130), so that the catalyst can be reused in the α-hydroxy acid production method. there is. In one embodiment, the catalyst can be recovered and reused in the α-hydroxy acid production method. In one embodiment, the catalyst can be recovered and reused in the α-hydroxy acid production method about 6 to 8 times.

An α-hydroxy acid having 3 or more carbon atoms can be produced through the α-hydroxy acid production method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the examples described below are only some embodiments of the present invention, and the scope of the present invention is not limited to the following examples.

Yield comparison according to catalyst, base and reaction time

The reaction yield according to the catalyst composition contained in the catalyst composition for producing α-hydroxy acid according to an example of the present invention, the type of base, and the reaction time were analyzed. Methanol and ethylene glycol were used as reactants. The reaction was carried out at 180°C for 16 hours, and in the case of Example 10 below, it was carried out for 4 hours only. The reaction formula for the above reaction is as follows.

The yields of Forms 1 to 3 depending on whether a catalyst is used, the type of catalyst, whether a base is used, and the type of base are shown in the table below.

division catalyst
(mole%) base
(equivalent weight) Form 1 yield
(%) Form 2 Yield
(%) Form 3 Yield
(%) Example 1 Ⅰ
(0.05) KOH
(1.5) 69 1.8 0.5 Example 2 Ⅱ
(0.05) KOH
(1.5) 46 2.7 0.6 Example 3 Ⅲ
(0.05) KOH
(1.5) 46 4.7 0.5 Example 4 Ⅳ
(0.05) KOH
(1.5) 63 2.3 0.2 Example 5 Ⅴ
(0.05) KOH
(1.5) 70 1.9 0.2 Example 6 Ⅵ
(0.05) KOH
(1.5) 41 12 0.6 Comparative Example 1 [Ir(COD)Cl] ₂
(0.025) KOH
(1.5) 20 1.3 0.1 Comparative Example 2 - KOH
(1.5) 4.8 1.1 0.1 Example 7 Ⅰ
(0.05) NaOH
(1.5) 67 4.9 0.1 Example 8 Ⅰ
(0.05) CsOH
(1.5) 70 3.7 0.3 Example 9 Ⅰ
(0.05) Ba(OH) ₂
(0.75) 56 4.4 0.2 Comparative Example 3 Ⅰ
(0.05) NaOMe
(1.5) One 1.6 - Comparative Example 4 Ⅰ
(0.05) - - - - Example 10
(4 hour reaction) Ⅰ
(0.05) CsOH
(1.5) 69 4.3 0.5 Example 11 Ⅰ
(0.0125) CsOH
(1.5) 72 2.8 0.3

The chemical formulas of the catalysts (I) to (VI) are as follows.

(Ⅰ)

(Ⅱ)

(Ⅲ)

(Ⅳ)

(Ⅴ)

(Ⅵ)

Referring to Table 1, the yields according to the use of catalyst and the type of catalyst were analyzed in Examples 1 to 6 and Comparative Examples 1 and 2. The catalyst of Comparative Example 1 did not contain N-heterocyclic carbene, and Comparative Example 2 did not use a catalyst. It can be seen that both Comparative Examples 1 and 2 showed significantly lower yields compared to Examples 1 to 6.

In Examples 7 to 9 and Comparative Examples 3 and 4, the yield according to the use and type of base was analyzed. NaOMe added as a base in Comparative Example 3 showed a low yield of less than 3%, and in Comparative Example 4 where no base was used, the reaction did not proceed at all. Meanwhile, CsOH of Example 8 showed the highest yield.

Example 10 is the result of reaction for 4 hours. When compared to Example 8, which was reacted for 16 hours under the same conditions, it can be seen that there is no significant difference in yield.

Example 11 is the result of a reaction using a catalyst concentration of 0.0125 mol%. When compared to Example 8, which was reacted under the same conditions using a catalyst concentration of 0.05 mol%, it can be seen that there is no significant difference in yield.

Reaction of ethylene glycol with alcohol

Ethylene glycol and different types of alcohol were reacted with the catalyst composition for producing α-hydroxy acid according to an embodiment of the present invention to produce α-hydroxy acid. The general reaction formula for the above reaction is as follows.

The above catalyst (I) or (IV) was used as the catalyst, and KOH or CsOH was used as the base. Ethylene glycol was used at 5 mmol, and alcohol was used at 100 mmol each. The reaction proceeded at 180°C for 16 hours.

Figure 6 is a diagram showing the produced α-hydroxy acid and yield. Referring to FIG. 6 and the above reaction formula together, the alcohol used in the examples and comparative examples of FIG. 6 corresponds to the produced α-hydroxy acid. When using the catalyst composition for producing α-hydroxy acid according to an example of the present invention, a yield of 50 to 75% can be achieved. In the case of Comparative Example 5 of Figure 6, it can be seen that the α-hydroxy acid produced when benzyl alcohol was used further underwent dehydration and hydrogenation reactions to form saturated aliphatic carboxylic acid.

Reuse of catalyst

In the process of carrying out the method for producing α-hydroxy acid according to an embodiment of the present invention using ethylene glycol and methanol, the catalyst (I) was recovered and reused to evaluate reusability. 1.5 equivalents of CsOH were used as catalyst (Ⅰ) and base, and 5 mmol of ethylene glycol and 100 mmol of methanol were used for each reaction. For each reaction, the reaction was carried out at 180°C for 4 hours, and the catalyst was reused repeatedly.

Figure 7 is a diagram showing the results of the above experiment. The bar graph in FIG. 7 represents yield, and the line graph represents turnover number (TON). Referring to Figure 7, as the reaction cycle progresses up to 7 times, the reaction yield does not show any significant change, confirming that the performance of the catalyst is maintained even when reused. TON also increases roughly linearly, which confirms that the activity of the catalyst is maintained even when reused.

Although the present invention has been described above with reference to preferred embodiments, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it is possible.

Claims (16)

A catalyst comprising N-heterocyclic carbene and iridium (Ir) bound thereto; and a base;
Promotes the process by which alcohol compounds and ethylene glycol compounds react to produce α-hydroxy acids,
Catalyst composition for producing α-hydroxy acids. According to paragraph 1,
The catalyst is characterized in that it contains one or more selected from the group consisting of the following formulas (I) to (VI),
Catalyst composition for producing α-hydroxy acids:
(Ⅰ)
(Ⅱ)
(Ⅲ)
(Ⅳ)
(Ⅴ)
(Ⅵ). According to paragraph 1,
The base is characterized in that it includes one or more selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), and barium hydroxide (Ba(OH) ₂ ).
Catalyst composition for producing α-hydroxy acids. A first step of preparing a reaction solution by dissolving a catalyst containing N-heterocyclic carbene and iridium bound thereto, a base, and an ethylene glycol compound in a liquid alcohol compound; and
A second step of heating the reaction solution to react the alcohol compound and the ethylene glycol compound to synthesize α-hydroxy acid.
Method for producing α-hydroxy acids. According to paragraph 4,
The second stage reaction is characterized in that it proceeds for 4 to 24 hours at 160 to 200 ° C.
Method for producing α-hydroxy acids. According to paragraph 4,
The catalyst is characterized in that it contains one or more selected from the group consisting of the following formulas (I) to (VI),
Method for preparing α-hydroxy acid:
(Ⅰ)
(Ⅱ)
(Ⅲ)
(Ⅳ)
(Ⅴ)
(Ⅵ). According to clause 6,
Characterized in that the concentration of the catalyst in the reaction solution is 0.01 to 0.1 mol%,
Method for producing α-hydroxy acids. According to paragraph 4,
The base is characterized in that it includes one or more selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), and barium hydroxide (Ba(OH) ₂ ).
Method for producing α-hydroxy acids. According to clause 8,
The reaction solution contains 1 to 2 equivalents of the base per 1 equivalent of the ethylene glycol compound,
The base is characterized in that it reduces the carbonyl group,
Method for producing α-hydroxy acids. According to paragraph 4,
The catalyst is characterized in that it induces a dehydrogenation reaction of the alcohol compound,
Method for producing α-hydroxy acids. According to paragraph 4,
The alcohol compound is characterized in that it has an alkyl group having 1 to 10 carbon atoms.
Method for producing α-hydroxy acids. According to clause 11,
The alcohol compound is characterized in that it includes one or more selected from the group consisting of methanol, ethanol, propanol, butanol, and pentanol,
Method for producing α-hydroxy acids. According to paragraph 4,
The reaction solution is characterized in that it contains 15 to 30 equivalents of the alcohol compound per 1 equivalent of the ethylene glycol compound.
Method for producing α-hydroxy acids. According to paragraph 4,
The α-hydroxy acid synthesized in the second step is characterized in that it has a carbon number of 3 to 12.
Method for producing α-hydroxy acids. According to clause 14,
Characterized in that the yield of α-hydroxy acid synthesized in the second step is 40 to 76%,
Method for producing α-hydroxy acids. According to paragraph 4,
After the second step is completed, it further includes a third step of preparing a reaction solution by adding an alcohol compound and an ethylene glycol compound to the reaction solution,
Characterized in that the second step is performed by heating the reaction solution of the third step, so that the catalyst is reused in the α-hydroxy acid production method.
Method for producing α-hydroxy acids.