Method for preparing cresol

Abstract

The present invention relates to a method for preparing cresol, the method comprising a step of reacting halotoluene with potassium t-butoxide (K(O-C(CH3)3)). The present invention can lower the reaction temperature and increase the selectivity and yield of m-cresol, compared to when NaOH is used.

Description

Method for producing cresol

[0001] The present invention relates to a method for producing cresol. More specifically, the present invention relates to a method for producing cresol using KotBu, which can lower the reaction temperature and increase the selectivity and yield of m-cresol compared to when NaOH is used.

[0002] Cresol is a phenolic compound that includes three isomers of methylphenol: o-cresol, m-cresol, and p-cresol. Each isomer is determined by the position of the methyl group attached to the phenol ring. These cresols can be used in various industrial applications, such as disinfectants, bactericides, and preservatives. In particular, m-cresol has excellent stability, high solubility in various solvents, and relatively low toxicity, making it suitable for various applications, including antioxidants, preservatives, pharmaceuticals, pesticides, and herbicides.

[0003] Conventional cresol production methods involve reacting halotolene with a basic aqueous solution of NaOH at a high temperature of approximately 350°C. This method not only has a significantly low selectivity for m-cresol, but also requires a long reaction time and a low yield. Furthermore, to achieve the desired cresol yield and purity, an additional byproduct treatment step is required, reducing productivity.

[0004] To solve this problem, a method is required to increase the selectivity and yield of m-cresol.

[0005] Related prior art includes Korean Patent Registration No. 10-1819216.

[0006] The purpose of the present invention is to provide a method for producing cresol using KotBu, which can lower the reaction temperature compared to the case where NaOH is used.

[0007] Another object of the present invention is to provide a method for producing cresol capable of increasing the selectivity and yield of m-cresol.

[0008] The above and other objects of the present invention can all be achieved by the present invention described below.

[0009] 1. One aspect of the present invention relates to a method for producing cresol, comprising a step of reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)).

[0010] 2. In the above 1 specific example, the method may have a selectivity ratio of m-cresol: o-cresol of 3:1 or more.

[0011] 3. In the above 1 to 2 specific examples, the method may have a yield of m-cresol of 90% or more.

[0012] 4. In the above 1 to 3 specific examples, the method for producing the cresol may include a first step of forming a precursor of the cresol by reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)); and a second step of adding an acid to the precursor of the cresol.

[0013] 5. In the above 1 to 4 specific examples, the first step is performed in the presence of a first solvent, and the first solvent may include an aromatic solvent.

[0014] 6. In the above 1 to 5 specific examples, the first step can be performed without a solvent.

[0015] 7. In the above specific examples 1 to 6, the first step can be performed without NaOH.

[0016] 8. In the above specific examples 1 to 7, the acid in the second step may have a pKa of -6 or less.

[0017] 9. In the above 1 to 8 specific examples, after the second step, a step of extracting cresol by introducing a second solvent may be further included.

[0018] 10. In the above 1 to 9 specific examples, the halotoluene may include one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene.

[0019] 11. In the above 1 to 10 specific examples, the molar ratio of the halotoluene and potassium t-butoxide (K(OC(CH3)3)) may be 3:1 to 1:2.

[0020] 12. In the above specific examples 1 to 11, the reaction can be performed at a temperature of 200°C or lower.

[0021] 13. Another aspect of the present invention relates to a method for improving the selectivity of m-cresol. The method comprises a step of reacting halotoluenes by adding a base, and potassium t-butoxide (K(OC(CH3)3)) is used as the base.

[0022] 14. In the above 13 specific examples, the reaction of the halotoluene and potassium t-butoxide (K(OC(CH3)3)) can be performed at a temperature of 200°C or lower.

[0023] 15. In the above 13 to 14 specific examples, the method may have a selectivity ratio of m-cresol: o-cresol of 3:1 or more.

[0024] 16. In the above 13 to 15 specific examples, the base may not include NaOH.

[0025] 17. In the above 13 to 16 specific examples, the halotoluene may include one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene.

[0026] 18. In the above 13 to 17 specific examples, the reaction can be performed in an aromatic solvent or in the absence of a solvent.

[0027] The purpose of the present invention is to provide a method for producing cresol using KotBu, which can lower the reaction temperature and increase the selectivity and yield of m-cresol compared to the case where NaOH is used.

[0028] Hereinafter, the present invention will be described in more detail. In the present specification, where the terms "includes," "has," and "consists of," are used, other parts may be added, unless "only" is used. When a component is expressed in the singular, it also includes the plural, unless otherwise explicitly stated.

[0029] When interpreting a component, it is interpreted as including the error range even if there is no separate explicit description.

[0030]

[0031] The present invention relates to a method for producing cresol.

[0032] The method for producing cresol of the present invention includes a step of reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)).

[0033] The above halotoluene is a form in which one of the hydrogen atoms of the benzene ring in toluene is replaced with a halogen atom containing chlorine, and may include one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene. When o-chlorotoluene is used, the reaction pathway is simplified and the selectivity and yield of m-cresol can be increased. In addition, when only p-chlorotoluene is used, the selectivity of m-cresol can be similar to that of the prior art, and therefore, in the present invention, the selectivity and yield of m-cresol can be increased by using a combination of o-chlorotoluene and p-chlorotoluene.

[0034] The above potassium t-butoxide (K(OC(CH3)3)) is a strong base with high reactivity, which may be advantageous in removing the chlorine atom of chlorotoluene. In addition, when using the above potassium t-butoxide, the reaction temperature can be lowered compared to when using NaOH, and the reaction with halotoluenes can be promoted, thereby increasing the selectivity and yield of m-cresol.

[0035] Specifically, the method for producing the cresol may include a first step of forming a precursor of the cresol by reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)); and a second step of adding an acid to the precursor of the cresol.

[0036] In the first step, the molar ratio of halotoluene and potassium t-butoxide (K(OC(CH3)3)) may be about 3:1 to 1:2. In a specific example, the molar ratio may be about 2.8:1 to 1:1.8, for example, about 2.5:1 to 1:1.5. In addition, when a combination of o-chlorotoluene and p-chlorotoluene is used as the halotoluene, the mixing molar ratio may be about 5:1 to 1:5, in a specific example, about 4:1 to 1:4, for example, about 3:1 to 1:3. In the above range, the selectivity and yield of m-cresol can be increased.

[0037] The above first step is performed in the presence of a first solvent, and the first solvent may include an aromatic solvent. The aromatic solvent may include, for example, tBuPh, toluene, xylene, mesitylene, etc., but is not limited to the solvents described above. When the above aromatic solvent is used, the amount of impurities produced can be reduced, and the reaction between halotoluenes and potassium t-butoxide can be promoted, thereby increasing the selectivity and yield of m-cresol.

[0038] The first solvent may be used in an amount of from about 0 to about 1000 parts by weight relative to 100 parts by weight of the reaction mixture containing halotoluene and potassium t-butoxide. In a specific example, the first solvent may be used in an amount of from about 0 to about 800 parts by weight or less, for example, from about 0 to about 600 parts by weight or less. Within the above range, the purity of the cresol can be increased.

[0039] Additionally, the first step can be performed without a solvent. By not using a solvent, the process can be simplified, processing time can be shortened, and the amount of impurities generated by the solvent can be reduced.

[0040] The above first step can be performed without NaOH. Conventional cresol production methods involve reacting a basic aqueous solution of NaOH with a halotoluene. The reaction occurs at high temperatures, such as about 200°C to about 450°C, which can lengthen the reaction time and necessitate additional byproduct treatment steps to achieve the desired cresol yield and purity. Therefore, the present invention utilizes potassium t-butoxide instead of NaOH to increase the selectivity and yield of m-cresol.

[0041] The above reaction can be carried out at a temperature of about 200°C or less. In a specific example, the temperature can be about 150°C or more and 200°C or less, for example, about 170°C or more and 200°C or less. When reacting halotoluenes with NaOH, the reaction temperature is about 200°C to 450°C, but when potassium t-butoxide is used instead of NaOH, the reaction is carried out at a temperature of about 200°C or less, and the selectivity of m-cresol can be increased. That is, m-cresol with higher selectivity can be obtained under simple reaction conditions at a low reaction temperature.

[0042] The above reaction can be carried out at a pressure of about 1 atm or more and 30 atm or less. In a specific example, the pressure can be about 1 atm or more and 5 atm or less, for example, about 1.5 atm or more and 4.5 atm or less. Within the above range, the selectivity and yield of m-cresol can be increased.

[0043] The second step is an acidifying step, and the acid may have a pKa of -6 or lower. The acid can neutralize the basic byproducts remaining after the reaction, facilitating the separation of the cresol from the organic layer and efficiently performing the extraction of the cresol. In specific examples, the acid may include a strong acid such as hydrobromic acid, nitric acid, hydrochloric acid, chloric acid, chlorous acid, perchloric acid, phosphoric acid, or diluted sulfuric acid, and is preferably hydrochloric acid. However, the acid is not limited to the strong acids described above.

[0044] The second step may be adjusted to a pH of about 2.5 or lower. In specific embodiments, the pH may be adjusted to about 0 to about 2.5, for example, about 0 to about 1.5. Within this range, a significant amount of the cresol compound does not remain in the aqueous layer, allowing efficient extraction of the cresol using an organic solvent.

[0045] After the second step, a step of extracting cresol by introducing a second solvent may be further included. The second solvent is an organic solvent that can efficiently separate cresol in the aqueous layer. In a specific example, the organic solvent may include diethyl ether, methylene chloride, methyl-t-butyl ether (MTBE), methyl isobutyl ketone (MIBK), isobutyl acetate (iBA), ethyl acetate (EA), benzene, toluene, hexane, heptane, cyclohexane, xylene, or a mixture thereof. However, the organic solvent is not limited to the organic solvents described above.

[0046] The second solvent may be used in an amount of about 100 to about 10,000 parts by weight relative to 100 parts by weight of the reaction product mixture containing cresol. In a specific example, the second solvent may be used in an amount of about 150 to about 8,000 parts by weight, for example, about 200 to about 6,000 parts by weight. Within this range, cresol separation within the aqueous layer is facilitated and the purity of the cresol can be increased. It may be preferable to repeat the step of extracting cresol with the second solvent two or more times.

[0047] When the above method for producing cresol is used, the selectivity ratio of m-cresol:o-cresol may be about 3: 1 or more. In a specific example, the selectivity ratio may be about 3.4: 1 or more, for example, about 4.2: 1 or more, and preferably about 5.0: 1 or more. In addition, the method may have a yield of m-cresol of about 90% or more. In a specific example, the yield may be about 94% or more, for example, about 96% or more, and preferably about 99% or more.

[0048]

[0049] Another aspect of the present invention relates to a method for improving the selectivity of m-cresol. The method comprises a step of reacting a halotoluene with a base, and potassium t-butoxide (K(OC(CH3)3)) is used as the base. The halotoluene may include one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene. The reaction of the halotoluene and potassium t-butoxide (K(OC(CH3)3)) may be performed at a temperature of about 200°C or lower. The reaction may be performed in the presence of an aromatic solvent or in the absence of a solvent. The aromatic solvent may include, but is not limited to, tBuPh, toluene, xylene, mesitylene, etc., for example. The base may not include NaOH. The method may have a selectivity ratio of m-cresol: o-cresol of about 3: 1 or greater. In a specific embodiment, the selectivity ratio may be about 3.4: 1 or greater, for example, about 4.2: 1 or greater, and preferably about 5.0: 1 or greater. In addition, the method may have a yield of m-cresol of about 90% or greater. In a specific embodiment, the yield may be about 94% or greater, for example, about 96% or greater, and preferably about 99% or greater.

[0050]

[0051] Hereinafter, the present invention will be described in more detail through examples; however, these examples are for the purpose of explanation only and should not be construed as limiting the present invention.

[0052]

[0053] Example

[0054] Example 1

[0055] O-chlorotoluene and potassium t-butoxide were introduced into the reactor at a molar ratio of 2:1, and the reaction was carried out at 170°C and atmospheric pressure for 18 hours in the presence of tBuPh (1.5 M) solvent. At this time, 159 g of the tBuPh solvent was introduced relative to 100 g of the reaction mixture containing o-chlorotoluene and potassium t-butoxide.

[0056] 450 g of hydrochloric acid (12 M) was added to 100 g of the cresol precursor prepared from the above reaction to adjust the pH to a value less than 1. Thereafter, the mixture was stirred at 100°C for 30 minutes in the absence of a solvent, and the cresol was separated from the aqueous layer using an extraction solvent. At this time, the extraction solvent used was 500 g of a mixture of methyl-t-butyl ether (MTBE), diethyl ether, and ethyl acetate (EA) compared to 100 g of a reaction mixture containing o-chlorotoluene and potassium t-butoxide.

[0057]

[0058] Example 2

[0059] The same procedure as Example 1 was followed, except that the molar ratio of o-chlorotoluene and potassium t-butoxide was 1:2.

[0060]

[0061] Example 3

[0062] The same procedure as Example 1 was followed, except that o-chlorotoluene and potassium t-butoxide were added in a molar ratio of 1:2 and the reaction was conducted for 4 hours.

[0063]

[0064] Example 4

[0065] The same procedure as Example 1 was followed, except that the molar ratio of o-chlorotoluene and potassium t-butoxide was 1:1.1 and the reaction was conducted for 4 hours.

[0066]

[0067] Example 5

[0068] The same procedure as Example 2 was followed, except that the reaction was carried out at 150°C for 4 hours in the absence of a solvent other than tBuPh (1.5 M).

[0069]

[0070] Example 6

[0071] The same procedure as Example 2 was followed, except that the reaction was carried out at 150°C for 16 hours in the absence of a solvent other than tBuPh (1.5 M).

[0072]

[0073] Example 7

[0074] The same procedure as in Example 1 was followed, except that the reaction was carried out at 150°C for 4 hours in the absence of a solvent other than tBuPh (1.5 M).

[0075]

[0076] Example 8

[0077] The reaction was performed in the same manner as in Example 1, except that the reaction was carried out at 200°C for 1 hour in the absence of a solvent other than tBuPh (1.5 M).

[0078]

[0079] Example 9

[0080] The same procedure as in Example 1 was followed, except that the reaction was carried out at 200°C for 15 minutes in the absence of a solvent other than tBuPh (1.5 M).

[0081]

[0082] Example 10

[0083] The same procedure as in Example 1 was followed, except that o-chlorotoluene, p-chlorotoluene, and potassium t-butoxide were added in a molar ratio of 1: 1: 1 and the reaction was carried out at 200°C for 15 minutes.

[0084]

[0085] Comparative Example 1

[0086] The same procedure as in Example 2 was followed except that NaOH was used instead of potassium t-butoxide.

[0087]

[0088] Comparative Example 2

[0089] The same procedure as in Example 3 was followed except that NaOEt was used instead of potassium t-butoxide.

[0090]

[0091] Comparative Example 3

[0092] The same procedure as in Example 2 was followed, except that a combination of potassium t-butoxide and NaOH in a molar ratio of 1:1 was used instead of potassium t-butoxide.

[0093]

[0094] Comparative Example 4

[0095] The same procedure as in Example 2 was followed, except that the reaction was carried out for 3 hours in an N-methyl-2-pyrrolidone (1.5 M) solvent instead of a tBuPh (1.5 M) solvent.

[0096]

[0097] The content of cresol in the above examples and comparative examples was analyzed using liquid chromatography, and the results are shown in Table 1:

[0098]

[0099] HalotolueneAlkoxide BaseHalotoluene: BaseSolventReaction temperature(℃)Reaction time(h)m-Cresol: o-CresolSelectivitySpecific yield(%)Example 1AKOtBuA:KOtBu = 2:1tBuPh170184.8:189Example 2AKOtBuA:KOtBu = 1:2tBuPh170185.5:152Example 3AKOtBuA:KOtBu = 1:2tBuPh17044.2:185Example 4AKOtBuA:KOtBu = 1:1.1tBuPh17044.7:167Example 5AKOtBuA:KOtBu = 1:2X15045.0:159Example 6AKOtBuA:KOtBu = 1:2X150164.8:134Example 7AKOtBuA:KOtBu = 2:1X15044.9:169Example 8AKOtBuA:KOtBu = 2:1X20013.4:196Example 9AKOtBuA:KOtBu = 2:1X2000.253.4:194Example 10A+BKOtBuA:B:KOtBu = 1:1:1tBuPh2000.256.9:199Comparative Example 1ANaOHA:NaOH = 1:2tBuPh17018Not measurable0Comparative Example 2ANaOEtA:NaOEt = 1:2tBuPh1704Not measurable0Comparative Example 3AKOtBu +NaOHA:KotBu;NaOH = 1:1:1tBuPh17018Not measurable37Comparative example 4ANaOHA:NaOH = 1:2NMP1703Not measurable0

[0100] * o-chlorotoluene: A, p-chlorotoluene: B

[0101] As shown in Table 1 above, the results of measuring the content of m-cresol show that Examples 1 to 10 have higher selectivity and yield of m-cresol than Comparative Examples 1 to 4.

[0102] This shows that when KotBu base is used to react with halotoluenes, m-cresol can be obtained with higher selectivity and yield under simple reaction conditions at a lower reaction temperature than when NaOH or NaOEt base is used.

[0103]

[0104] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

[0105]

[0106] The method for producing cresol according to one embodiment of the present invention has industrial applicability.

Claims

1. A method for producing cresol, comprising a step of reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)).

2. A method for producing cresol in the first paragraph, wherein the method has a selectivity ratio of m-cresol:o-cresol of 3:1 or more.

3. A method for producing cresol in the first paragraph, wherein the method has a yield of m-cresol of 90% or more.

4. In paragraph 1, The above method for producing cresol is A first step of forming a precursor of cresol by reacting halotoluene and potassium t-butoxide (K(OC(CH3)3)); and A method for producing cresol, comprising a second step of adding an acid to the precursor of the cresol.

5. In paragraph 4, The above first step is performed in the presence of a first solvent, A method for producing cresol, wherein the first solvent comprises an aromatic solvent.

6. In paragraph 4, A method for producing cresol, wherein the first step is performed without a solvent.

7. In paragraph 4, A method for producing cresol, wherein the first step is performed without NaOH.

8. In paragraph 4, A method for producing cresol, wherein in the second step, the acid has a pKa of -6 or less.

9. In paragraph 4, A method for producing cresol, further comprising, after the second step, a step of extracting cresol by introducing a second solvent.

10. In paragraph 1, A method for producing cresol, wherein the halotoluene comprises one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene.

11. In paragraph 1, A method for producing cresol in which the molar ratio of the above halotoluene and potassium t-butoxide (K(OC(CH3)3)) is 3:1 to 1:

2.

12. In paragraph 1, A method for producing cresol, wherein the above reaction is performed at a temperature of 200°C or lower.

13. A method for improving the selectivity of m-cresol, the method comprising: It includes a step of reacting by adding a base to halotoluene, A method for improving the selectivity of m-cresol, characterized in that potassium t-butoxide (K(OC(CH3)3)) is used as the base.

14. In paragraph 13, A method for improving the selectivity of m-cresol, wherein the reaction of the above halotoluene and potassium t-butoxide (K(OC(CH3)3)) is performed at a temperature of 200°C or lower.

15. In paragraph 13, The above method is a method for improving the selectivity of m-cresol, wherein the selectivity ratio of m-cresol: o-cresol is 3:1 or more.

16. In paragraph 13, A method for improving the selectivity of m-cresol, wherein the base does not contain NaOH.

17. In paragraph 13, A method for improving the selectivity of m-cresol, wherein the halotoluene comprises one selected from the group consisting of o-chlorotoluene; and a combination of o-chlorotoluene and p-chlorotoluene.

18. In paragraph 13, A method for improving the selectivity of m-cresol, wherein the above reaction is performed in an aromatic solvent or in the absence of a solvent.