A preparation method of 2,3-dimethylphenol

Abstract

The invention belongs to the technical field of organic synthesis, and in particular to a kind of preparation method of 2,3-dimethylphenol. The preparation method of 2,3-dimethylphenol provided by the present invention comprises the following steps: 2,3-dimethylaniline, inorganic acid and water are subjected to salt-hydrolysis reaction to obtain crude 2,3-dimethylphenol; The crude 2,3-dimethylphenol is extracted to obtain oil phase and aqueous phase; The oil phase is sequentially neutralized, washed and distilled under reduced pressure to obtain the 2,3-dimethylphenol. The preparation method provided by the present invention is direct hydrolysis of salt under acidic conditions using 2,3-dimethylaniline as raw material, and step is simple, safe and efficient, and the ammonium salt of by-product can be recycled, and recovery process is relatively simple and environmentally friendly. Meanwhile, the 2,3-dimethylphenol product synthesized using this method has high purity and stable quality, and has good industrial value.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing 2,3-dimethylphenol. Background Art

[0002] 2,3-Dimethylphenol is an important organic compound used primarily in the manufacture of phenolic resins, plasticizers, dyes, flotation agents, insecticides, fungicides, mold adhesives, wood preservatives, antioxidants, and lubricant additives. It can also be used as an intermediate in other organic syntheses. Furthermore, high-purity 2,3-dimethylphenol can be used as an intermediate in electronic materials, providing a key chemical raw material for many areas of modern science and technology.

[0003] 2,3-Dimethylphenol was originally obtained by distillation and purification of mixed xylenes from coal tar. Currently, it is primarily produced using 2,3-dimethylaniline as a raw material. Chinese patent CN111943823A synthesizes 2,3-dimethylphenol from 2,3-dimethylaniline through diazotization, hydrolysis, and purification. However, the diazotization reaction employed in this method is highly hazardous and the process is complex, making efficient production difficult. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a method for preparing 2,3-dimethylphenol. The preparation method provided by the present invention has simple steps and is safe and efficient.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for preparing 2,3-dimethylphenol, comprising the following steps:

[0007] 2,3-dimethylaniline, inorganic acid and water are subjected to a salt-hydrolysis reaction to obtain crude 2,3-dimethylphenol;

[0008] Extracting the crude 2,3-dimethylphenol to obtain an oil phase and an aqueous phase;

[0009] The oil phase is sequentially neutralized, washed with water and distilled under reduced pressure to obtain the 2,3-dimethylphenol.

[0010] Preferably, the inorganic acid comprises phosphoric acid, sulfuric acid or hydrochloric acid.

[0011] Preferably, the molar ratio of the 2,3-dimethylaniline to the inorganic acid is 1:1-6.

[0012] Preferably, the molar ratio of the 2,3-dimethylaniline to water is 1:50-150.

[0013] Preferably, the temperature of the salt formation-hydrolysis reaction is 200-300° C., and the time is 6-24 hours.

[0014] Preferably, the reaction atmosphere of the salt formation-hydrolysis reaction is an inert atmosphere.

[0015] Preferably, the extraction agent used in the extraction is ethyl acetate, methyl isopropyl ketone, methyl isobutyl ketone or toluene.

[0016] Preferably, the neutralizing agent is an aqueous solution of sodium bicarbonate.

[0017] Preferably, the aqueous phase can replace water to perform a salt-hydrolysis reaction.

[0018] Preferably, the aqueous phase is neutralized and concentrated in sequence to obtain the ammonium salt.

[0019] The present invention provides a method for preparing 2,3-dimethylphenol, comprising the following steps: subjecting 2,3-dimethylaniline, an inorganic acid, and water to a salification-hydrolysis reaction to obtain a crude 2,3-dimethylphenol product; extracting the crude 2,3-dimethylphenol product to obtain an oil phase and an aqueous phase; and sequentially neutralizing, washing, and distilling the oil phase under reduced pressure to obtain the 2,3-dimethylphenol. The preparation method provided by the present invention utilizes 2,3-dimethylaniline as a raw material and directly hydrolyzes the salified product under acidic conditions. The method is simple, safe, and efficient. The reaction solvent is water, eliminating the need for complex catalysts and ensuring environmental friendliness. The method avoids the hazards of diazotization reactions and eliminates the generation of sodium salts after the reaction, minimizing the amount of waste to be treated. The ammonium salt produced as a byproduct can be recycled, resulting in a relatively simple and environmentally friendly recovery process. Furthermore, the 2,3-dimethylphenol product synthesized using this method exhibits high purity and stable quality. As shown in the examples, the yield of 2,3-dimethylphenol obtained by this method exceeds 90%, with a purity exceeding 95%, demonstrating its excellent industrial value. DETAILED DESCRIPTION

[0020] The present invention provides a method for preparing 2,3-dimethylphenol, comprising the following steps:

[0021] 2,3-dimethylaniline, inorganic acid and water are subjected to a salt-hydrolysis reaction to obtain crude 2,3-dimethylphenol;

[0022] Extracting the crude 2,3-dimethylphenol to obtain an oil phase and an aqueous phase;

[0023] The oil phase is sequentially neutralized, washed with water and distilled under reduced pressure to obtain the 2,3-dimethylphenol.

[0024] In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0025] The invention conducts a salt-forming-hydrolysis reaction on 2,3-dimethylaniline, an inorganic acid and water to obtain a crude 2,3-dimethylphenol product.

[0026] In the present invention, the inorganic acid preferably includes phosphoric acid, sulfuric acid or hydrochloric acid, more preferably phosphoric acid or sulfuric acid, and most preferably phosphoric acid; the molar ratio of the 2,3-dimethylaniline to the inorganic acid is preferably 1:1-6, more preferably 1:1-4, and most preferably 1:1-2; the present invention has no special limitation on the concentration of the inorganic acid, and a conventional concentration well known to those skilled in the art can be used.

[0027] In the present invention, the molar ratio of 2,3-dimethylaniline to water is preferably 1:50-150, more preferably 1:80-140, and most preferably 1:100-130.

[0028] In the present invention, the order of adding materials in the salt formation-hydrolysis reaction is preferably to add water, inorganic acid and 2,3-dimethylaniline in sequence.

[0029] In the present invention, the temperature of the salt formation-hydrolysis reaction is preferably 200-300°C, more preferably 220-280°C, most preferably 230-260°C; the time is preferably 6-24h, more preferably 7-18h, most preferably 8-12h.

[0030] In the present invention, the reaction atmosphere of the salt formation-hydrolysis reaction is preferably an inert atmosphere; the inert atmosphere is preferably nitrogen; the method of providing the inert atmosphere is preferably inert atmosphere replacement; the number of inert atmosphere replacements is preferably 3 to 5 times, more preferably 4 to 5 times.

[0031] In the present invention, the lining material of the reactor for the salt formation-hydrolysis reaction is preferably zirconium, tantalum, zirconium alloy or monel alloy, more preferably zirconium, tantalum or zirconium alloy, most preferably zirconium or zirconium alloy.

[0032] In the present invention, the use of the above-mentioned type of reactor lining material for the salt formation-hydrolysis reaction can, on the one hand, solve the corrosion of the reactor lining material by inorganic acid under high temperature conditions, and on the other hand, reduce the generation of tar.

[0033] In the present invention, the chemical equation of the salt formation-hydrolysis reaction is:

[0034]

[0035] After obtaining the crude 2,3-dimethylphenol, the present invention extracts the crude 2,3-dimethylphenol to obtain an oil phase and an aqueous phase.

[0036] In the present invention, the extraction agent used in the extraction is preferably ethyl acetate, methyl isopropyl ketone, methyl isobutyl ketone or toluene, more preferably ethyl acetate, methyl isopropyl ketone or toluene, and most preferably ethyl acetate or toluene; the number of extractions is preferably 1 to 4 times, more preferably 2 to 3 times, and most preferably 3 times; the mass ratio of the extraction agent to water is preferably 0.1 to 1, more preferably 0.1 to 0.6, and most preferably 0.2 to 0.4; the extraction temperature is preferably 30 to 80°C, more preferably 30 to 50°C, and most preferably 40°C.

[0037] In the present invention, the extraction preferably further includes standing and separating the layers.

[0038] In the present invention, the aqueous phase can preferably replace water to carry out the salt-hydrolysis reaction; the number of times the aqueous phase is used to carry out the salt-hydrolysis reaction is preferably 1 to 8 times, more preferably 1 to 5 times, and most preferably 3 times.

[0039] After obtaining the oil phase, the present invention sequentially neutralizes, washes with water, and performs reduced pressure distillation on the oil phase to obtain the 2,3-dimethylphenol.

[0040] In the present invention, the neutralizing agent is preferably a sodium bicarbonate aqueous solution; the mass percentage of sodium bicarbonate in the sodium bicarbonate aqueous solution is preferably 1-30%, more preferably 1-15%, and most preferably 1-5%; the mass ratio of the sodium bicarbonate aqueous solution to the oil phase is preferably 0.2-1:1, more preferably 0.2-0.8:1, and most preferably 0.3-0.6:1.

[0041] In the present invention, the number of water washings is preferably 1 to 4 times, more preferably 2 to 3 times, and most preferably 2 times; the water washing further includes standing for stratification; the present invention does not have any special limitation on the process of vacuum distillation, and the solvent of the oil phase can be removed by a method well known to those skilled in the art.

[0042] After obtaining the aqueous phase, the present invention preferably sequentially neutralizes and concentrates the aqueous phase to obtain an ammonium salt.

[0043] In the present invention, the reagent for neutralizing the aqueous phase is preferably liquid ammonia; the present invention has no special limitation on the neutralization process, and the pH value of the aqueous phase can be adjusted to 11-12 by a method well known to those skilled in the art; the concentration is preferably reduced-pressure concentration; the present invention has no special limitation on the reduced-pressure concentration process, and the ammonium salt in the aqueous phase can be crystallized and precipitated by a method well known to those skilled in the art.

[0044] The preparation method provided by the present invention uses 2,3-dimethylaniline as a raw material and directly hydrolyzes the salt under acidic conditions. The steps are simple, safe, and efficient. The reaction solvent is water, and no complex catalyst is required. This is environmentally friendly and avoids the dangers of diazotization reactions. In addition, no sodium salt is generated after the reaction, the amount of three wastes to be treated is small, and the ammonium salt of the byproduct can be recycled. The recovery process is relatively simple and environmentally friendly. At the same time, the 2,3-dimethylphenol product synthesized by this method has high purity and stable quality. The data in the examples show that the yield of 2,3-dimethylphenol obtained by this method is greater than 90%, and the purity reaches greater than 95%, which has great industrial value.

[0045] In order to further illustrate the present invention, the preparation method of 2,3-dimethylphenol provided by the present invention is described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] To a 1L zirconium autoclave were added 360g of water, 30g (0.3mol) of 98% sulfuric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline. The reactor was nitrogen-purged five times, then sealed and heated to 260°C for 8 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 90g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 390g of aqueous phase and 112g of oil phase. The oil phase was neutralized with 56g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.5g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis revealed a 94.0% pure product, for a yield of 94.3%.

[0048] Example 2

[0049] To a 1L zirconium autoclave were added 355g of water, 34.5g (0.3mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline. The reactor was nitrogen-purged five times, then sealed and heated to 260°C for 8 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 90g of ethyl acetate. The oil and aqueous phases were combined to obtain 389g of aqueous phase and 111g of oil phase, which was used for the next batch of reactions. The oil phase was neutralized with 55.5g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.3g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis revealed a 97.0% pure product, for a yield of 96.6%.

[0050] Example 3

[0051] In a 1L zirconium autoclave, 390g of the aqueous phase from Example 2, 23.0g (0.2mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline were added in sequence. The reactor was nitrogen-purged five times, then sealed, heated to 260°C, and kept warm for 8 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 100g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 415g of aqueous phase and 120g of oil phase, which was used for the next batch of reactions. The oil phase was neutralized with 60g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for stratification. After stratification, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.0g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) determined the pure product to be 96.5% by mass, with a yield of 94.7%.

[0052] Example 4

[0053] 410 g of the aqueous phase from Example 3, 23.0 g (0.2 mol) of 85% phosphoric acid, and 24.4 g (0.2 mol) of 2,3-dimethylaniline were added sequentially to a 1 L zirconium autoclave. The reactor was nitrogen-purged five times, then sealed, heated to 260° C., and kept warm for 8 h. After the hydrolysis reaction, the temperature was lowered to 40° C. The reaction solution was extracted three times with 105 g of ethyl acetate. The extracted oil phase and aqueous phase were combined to obtain 438 g of aqueous phase and 120 g of oil phase. The aqueous phase was adjusted to a pH of 11-12 with liquid ammonia, concentrated under reduced pressure, and crystallized to obtain 100 g of ammonium phosphate. The oil phase was neutralized with 60 g of a 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, obtaining 24.2 g of 2,3-dimethylphenol. High performance liquid chromatography (HPLC) determined that the pure product had a mass percentage of 95.8%, with a yield of 95.0%.

[0054] Example 5

[0055] To a 1L zirconium autoclave were added 355g of water, 34.5g (0.3mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline. The reactor was nitrogen-purged five times, then sealed and heated to 230°C for 16 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 90g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 389g of aqueous phase and 110g of oil phase. The oil phase was neutralized with 55g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.0g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis revealed a 97.5% pure product, for a yield of 95.9%.

[0056] Example 6

[0057] To a 1L zirconium autoclave were added 355g of water, 34.5g (0.3mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline. The reactor was nitrogen-purged five times, then sealed and heated to 300°C for 4 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 90g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 390g of aqueous phase and 111g of oil phase. The oil phase was neutralized with 55g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.2g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis revealed a 95.0% pure product, for a yield of 94.2%.

[0058] Example 7

[0059] In a 1L zirconium autoclave, 177g of water, 34.5g (0.3mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline were added in sequence. The reactor was nitrogen-purged five times, then sealed and heated to 260°C for 8 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 45g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 211g of aqueous phase and 66g of oil phase. The oil phase was neutralized with 33g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 23.9g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis revealed a 96.0% pure product, for a yield of 94.0%.

[0060] Example 8

[0061] In a 1L zirconium autoclave, 535g of water, 34.5g (0.3mol) of 85% phosphoric acid, and 24.4g (0.2mol) of 2,3-dimethylaniline were added in sequence. The reactor was nitrogen-purged five times, then sealed and heated to 260°C for 8 hours. After the hydrolysis reaction, the temperature was lowered to 40°C. The reaction solution was extracted three times with 135g of ethyl acetate. The extracted oil and aqueous phases were combined to obtain 570g of aqueous phase and 155g of oil phase. The oil phase was neutralized with 78g of 5% sodium bicarbonate aqueous solution, washed twice with water, and allowed to stand for separation. After separation, the oil phase was distilled under reduced pressure to remove the solvent, yielding 24.1g of 2,3-dimethylphenol. High-performance liquid chromatography (HPLC) analysis showed a pure product content of 97.6%, for a yield of 96.4%.

[0062] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing 2,3-dimethylphenol, characterized in that: The specific steps are as follows: 2,3-dimethylaniline, inorganic acid and water are subjected to a salt-hydrolysis reaction to obtain crude 2,3-dimethylphenol; Extracting the crude 2,3-dimethylphenol to obtain an oil phase and an aqueous phase; The oil phase is sequentially neutralized, washed with water and distilled under reduced pressure to obtain the 2,3-dimethylphenol; The molar ratio of the 2,3-dimethylaniline to water is 1:50-150.

2. The preparation method according to claim 1, characterized in that The inorganic acid includes phosphoric acid, sulfuric acid or hydrochloric acid.

3. The preparation method according to claim 1, characterized in that The molar ratio of the 2,3-dimethylaniline to the inorganic acid is 1:1-6.

4. The preparation method according to claim 1, characterized in that The temperature of the salt formation-hydrolysis reaction is 200-300° C., and the time is 6-24 hours.

5. The preparation method according to claim 1 or 4, characterized in that The reaction atmosphere of the salt formation-hydrolysis reaction is an inert atmosphere.

6. The preparation method according to claim 1, characterized in that The extraction agent used in the extraction is ethyl acetate, methyl isopropyl ketone, methyl isobutyl ketone or toluene.

7. The preparation method according to claim 1, characterized in that The neutralizing reagent is a sodium bicarbonate aqueous solution.

8. The preparation method according to claim 7, characterized in that The aqueous phase can replace water to perform a salt-hydrolysis reaction.

9. The preparation method according to claim 1, characterized in that The aqueous phase is sequentially neutralized and concentrated to obtain an ammonium salt.

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