Method for preparing 2-methyl-6-acyl naphthalene

Abstract

The invention discloses a method for preparing 2-methyl-6-acyl naphthalene, which comprises the following steps: S1, mixing aluminum trichloride crystals with triethylamine hydrochloride powder under the protective atmosphere and anhydrous condition to obtain ionic liquid; s2, under a protective atmosphere, dropwise adding acyl chloride into the ionic liquid to obtain an acylation reagent of acyl chloride; s3, dissolving 2-methylnaphthalene to obtain a 2-methylnaphthalene solution; s4, adding an acylation reagent into the 2-methylnaphthalene solution under a protective atmosphere and a low-temperature condition, and stirring to react; and S5, after the reaction, quenching the reaction product by using a hydrochloric acid solution, then extracting, neutralizing the extract, and drying to obtain the 2-methyl-6-acyl naphthalene product. The method for preparing the 2-methyl-6-acylnaphthalene is different from the prior art, the method abandons the use of a toxic polar solvent and a strong mixing mode, and many problems caused by the polar solvent and the strong mixing mode do not exist in the preparation process of the 2-methyl-6-acylnaphthalene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, in particular to a method for preparing 2-methyl-6-acylnaphthalene. BACKGROUND

[0002] 2,6-naphthalene dicarboxylic acid (2,6-NDA) is an important monomer for preparing high-performance polyester material polyethylene naphthalate (PEN). Compared with polyethylene terephthalate (PET), polyethylene naphthalate (PEN) has better performance, for example, the mechanical properties, mechanical properties, thermal stability, chemical properties and gas barrier properties of PEN are all better than those of PET material. It can be said that PEN is an excellent product to replace PET, therefore, due to the excellent performance of PEN, it has a wide range of applications in the fields of fibers, films, electronics and insulation materials. And 2-methyl-6-acylnaphthalene is a key intermediate for synthesizing 2,6-naphthalene dicarboxylic acid (2,6-NDA), so it is very meaningful to prepare 2-methyl-6-acylnaphthalene.

[0003] Currently, the main method for preparing 2-methyl-6-acylnaphthalene is to use 2-methylnaphthalene as raw material to realize Friedel-Crafts acylation reaction. For example, Chinese patent CN114621066A discloses a method for synthesizing 2-methyl-6-acylnaphthalene reaction. The method uses polar organic substances such as nitrobenzene as solvent, uses aluminum trichloride (Lewis acid) as catalyst, adjusts and optimizes process parameters, and uses strong mixing method to realize high product yield of 2-methyl-6-acylnaphthalene. However, although this method has high product yield and reaction efficiency, it also has some problems, for example: ① polar solvents such as nitrobenzene are used, and nitrobenzene is a highly toxic substance that can pose a threat to human health and the ecological environment. Extra precautions are needed when operating, which has safety hazards and makes subsequent "three wastes" treatment more complex and costly; ② nitrobenzene has certain hygroscopicity. If a small amount of water is mixed into the solvent or reaction system, it may cause the hydrolysis of anhydrous aluminum trichloride to generate hydrochloric acid and insoluble aluminum hydroxide. This not only deactivates the catalyst and reduces the reaction efficiency, but also corrodes the reaction equipment; ③ the Lewis acid (aluminum trichloride) and acylation reagent (such as acyl chloride) used in the reaction are highly corrosive, and the nitrobenzene as the solvent will mix with these substances and circulate in the whole system, thereby accelerating the corrosion of the reactor, pipeline, pump valve and other equipment, which not only increases the equipment maintenance cost, but also shortens the service life of the equipment; ④ strong mixing method is used. Friedel-Crafts acylation reaction is usually a strong exothermic reaction. Although the use of strong mixing method can improve the contact probability between reactants, increase the reaction efficiency and help heat distribution, if the mixing efficiency is insufficient or the heat cannot be removed in time, it may cause local overheating, accelerate the occurrence of side reactions (such as multi-acylation, aromatic ring alkylation, acyl chloride decomposition or polymerization), thereby reducing the selectivity of the target product (2-methyl-6-acylnaphthalene) and affecting the purity; ⑤ the strong mixing method has high requirements for the heat exchange system, which needs to quickly and accurately remove a large amount of reaction heat to avoid side reactions, resulting in high cost; ⑥ the reaction system usually contains corrosive media (such as Lewis acid, acyl chloride) and toxic solvents (such as nitrobenzene), so the strong mixing method has high requirements for the sealing performance, corrosion resistance of the material and mechanical stability of the reaction equipment, otherwise it is easy to cause leakage, equipment wear and tear or failure.

[0004] In summary, although the existing synthesis method of 2-methyl-6-acylnaphthalene has high product yield and reaction efficiency, the problems cannot be ignored. Therefore, there is an urgent need for a method for preparing 2-methyl-6-acylnaphthalene that has high product yield and does not have the above problems. SUMMARY

[0005] The present application aims to provide a method for preparing 2-methyl-6-acylnaphthalene, which aims to solve the problems existing in the prior art of synthesizing 2-methyl-6-acylnaphthalene, and meanwhile has high product yield and high product purity.

[0006] To achieve the above-mentioned purpose, the present application is realized by the following technical scheme: The present application provides a method for preparing 2-methyl-6-acylnaphthalene, which comprises the following steps: S1, mixing aluminum trichloride crystals with triethylamine hydrochloride powder under a protective atmosphere and in anhydrous conditions to obtain an ionic liquid; S2, adding acyl chloride to the ionic liquid under a protective atmosphere to obtain an acylating agent of acyl chloride; S3, dissolving 2-methylnaphthalene to obtain a 2-methylnaphthalene solution; S4, adding the acylating agent to the 2-methylnaphthalene solution under a protective atmosphere and in low-temperature conditions, and stirring to react; S5, after the reaction, quenching the reaction product with a hydrochloric acid solution, then extracting, neutralizing the extract, drying, and obtaining a 2-methyl-6-acylnaphthalene product.

[0007] Further, the method for preparing 2-methyl-6-acylnaphthalene comprises that the reaction temperature in step S1 is 20-30 DEG C, and oscillation is performed at a frequency of 100-140 Hz.

[0008] Further, the method for preparing 2-methyl-6-acylnaphthalene comprises that the amount-of-substance content of aluminum trichloride added in step S1 in the ionic liquid is 55-70%.

[0009] Further, the method for preparing 2-methyl-6-acylnaphthalene comprises that in step S2, acyl chloride at 0-3 DEG C is added to the ionic liquid at 0-5 DEG C under a protective atmosphere to obtain an acylating agent containing 5.0-20.0 wt% acyl chloride; wherein the acyl chloride is selected from acetyl chloride or propionyl chloride.

[0010] Further, the method for preparing 2-methyl-6-acylnaphthalene comprises that in step S3, 2-methylnaphthalene is dissolved in cyclohexane to obtain a 2-methylnaphthalene solution with a content of 20.0-40.0 wt%.

[0011] Further, the method for preparing 2-methyl-6-acylnaphthalene comprises that in step S4, the acylating agent is added dropwise to the 2-methylnaphthalene solution under a protective atmosphere and in low-temperature conditions not higher than 5 DEG C, and stirring is performed at a speed of 300-400 rpm to react.

[0012] Further, the method for preparing 2-methyl-6-acyl naphthalene comprises the following specific steps:

[0013] Advantages of the present application: The method for preparing 2-methyl-6-acyl naphthalene provided by the present application is a preparation method different from the prior art, which discards the use of toxic polar solvents (nitrobenzene, nitromethane and the like) and strong mixing mode, so that the problems caused by the polar solvents and the strong mixing mode do not exist in the preparation process. The method of the present application is a relatively green and environmentally friendly method, and the preparation process is simple, the product yield is high, and the yield can be more than 94%, and the product purity is high, and the content of 2-methyl-6-acyl naphthalene in the product can be more than 95%. DETAILED DESCRIPTION

[0014] The technical solutions of the present application will be described in detail below with specific examples. Obviously, the described examples are only a part of the examples of the present application, not all. The description of the at least one example is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0015] Example 1

[0016] The present example 1 provides a method for preparing 2-methyl-6-acyl naphthalene, which comprises the following specific steps: S1, under the conditions of nitrogen atmosphere and anhydrous, 10.0 g of aluminum chloride crystals is weighed and placed in a explosion-proof glass test tube, then white triethylamine hydrochloride powder is gradually added into the test tube, and the glass test tube is oscillated at 25℃ with a frequency of 120Hz to obtain a brown viscous transparent ionic liquid; Wherein, by adjusting the amount of triethylamine hydrochloride powder and the temperature, ionic liquids with different aluminum chloride contents (IL-X-AlCl3) can be obtained, X represents the amount of substance content of aluminum chloride in the ionic liquid, and in this example X=0.65, so the ionic liquid can be represented as IL-0.65-AlCl3; S2, under the nitrogen atmosphere, acetyl chloride (acyl chloride) at 0℃ is slowly added into the ionic liquid (IL-0.65-AlCl3) at 3℃ to prepare an acylation reagent containing 10.0wt% acetyl chloride; S3, weigh 2-methylnaphthalene, dissolve it in cyclohexane to prepare a 30.0wt% 2-methylnaphthalene solution 2-methylnaphthalene solution of 2-methylnaphthalene; S4, take 1.0g of the 2-methylnaphthalene solution and put it into a reaction tube, then put the reaction tube into an ethanol constant temperature liquid at 0℃, under a nitrogen atmosphere, drop the acylation reagent into the 2-methylnaphthalene solution (reaction tube), and start stirring at the same time, the stirring speed is 360rpm, after the dropping is completed, continue to stir for 0.5 hours to react; S5, after the reaction, quench the reaction product with 5.0mol / L hydrochloric acid solution, then extract it with cyclohexane for 3 times, neutralize the extract, dry it, and obtain the 2-methyl-6-acetylnaphthalene product, the yield is 95.9%.

[0017] After the reaction of step S5, the ionic liquid will be stratified, the lower precipitate is quenched with hydrochloric acid solution (the liquid in the upper layer is mainly ionic liquid, which can be used for ionic liquid after light components are removed under reduced pressure).

[0018] The product of the above embodiment 1 is respectively analyzed by liquid chromatography (HPLC analysis) and gas chromatography (GC analysis): ①HPLC analysis: Agilent 1100 type high performance liquid chromatograph; C18 separation column; flow rate 0.2mL / min; mobile phase ratio V(acetonitrile):V(water)=50:50; detector wavelength 245nm.

[0019] ②GC analysis: GC-2014C type gas chromatograph; KB-5 capillary column; split ratio 60; vaporization chamber temperature 280℃; initial column temperature 140℃, maintain for 2 minutes, increase to 320℃ at a rate of 20℃ / min, maintain for 5 minutes, and decrease; hydrogen flame detector.

[0020] Results: the product obtained in embodiment 1 is analyzed by liquid chromatography and gas chromatography, and the comprehensive results show that the content of 2-methyl-6-acetylnaphthalene in the product is 96.5wt%, which shows a high product purity.

[0021] Thanks to the optimization of the 2-methyl-6-acylnaphthalene preparation method, the content of the isomer (2-methyl-7-acylnaphthalene) in the product is small, which reduces the difficulty of purification.

[0022] The reaction system based on 2-methyl-6-acylnaphthalene is a fast and large heat release reaction system, The method of the application also carries out the reaction under low temperature conditions, which can be used for cooling, is beneficial to heat dissipation, reduces the occurrence of side reactions, and is beneficial to the improvement of product purity.

[0023] Example 2

[0024] This Example 2 provides a method for preparing 2-methyl-6-acylnaphthalene, which comprises the following specific steps: S1, under the conditions of nitrogen atmosphere and anhydrous, 10.0 g of aluminum chloride crystals were weighed into an explosion-proof glass test tube, then white triethylamine hydrochloride powder was gradually added into the test tube, and the glass test tube was oscillated at a frequency of 130 Hz at 20℃ to obtain a brown viscous transparent liquid; wherein by adjusting the amount of triethylamine hydrochloride powder added and the temperature, ionic liquids (IL-X-AlCl3) with different contents of aluminum chloride can be obtained, X represents the amount-of-substance content of aluminum chloride added in the ionic liquid, and in this example X = 0.60, so the ionic liquid can be represented as IL-0.60-AlCl3; S2, under the conditions of nitrogen atmosphere, propionyl chloride (acyl chloride) at 2℃ was slowly added into the ionic liquid (IL-0.60-AlCl3) at 5℃ to prepare an acylation reagent containing 15.0wt% acetyl chloride; S3, 2-methylnaphthalene was weighed and dissolved in cyclohexane to prepare a 2-methylnaphthalene solution containing 20.0wt% 2-methylnaphthalene; S4, 1.0 g of the 2-methylnaphthalene solution was taken into a reaction tube, and the reaction tube was placed in an ethanol constant temperature liquid at 0℃. Under the conditions of nitrogen atmosphere, the above-mentioned acylation reagent was added dropwise into the 2-methylnaphthalene solution (reaction tube), and stirring was started at the same time during the dropping process, and the stirring speed was 320 rpm. After the dropping was completed, the stirring was continued for 0.5 hours for reaction. S5, after the reaction, the reaction product was first quenched with 3.0 mol / L hydrochloric acid solution, and then extracted with an equal volume of cyclohexane for 5 times. The extracted liquid was neutralized, dried, and the 2-methyl-6-propionyl naphthalene product was obtained, with a yield of 94.6%.

[0025] The product of the above Example 2 was subjected to liquid chromatography analysis (HPLC analysis) and gas chromatography analysis (GC analysis) respectively: ①HPLC analysis: Agilent 1100 type high performance liquid chromatograph; C18 separation column; flow rate 0.2 mL / min; mobile phase ratio V(acetonitrile):V(water)=50:50; detector wavelength 245 nm.

[0026] ②GC analysis: GC-2014C type gas chromatograph; KB-5 capillary column; split ratio 60; vaporization chamber temperature 280℃; initial column temperature 140℃, maintained for 2 minutes, increased to 320℃ at a rate of 20℃ / min, maintained for 5 minutes, and then decreased; hydrogen flame detector.

[0027] Results: The product obtained in Example 2 was analyzed by liquid chromatography and gas chromatography, and the comprehensive results showed that the content of 2-methyl-6-propionyl naphthalene in the product was 95.5wt%, which showed a high product purity.

[0028] Example 3

[0029] Example 3 provides a method for preparing 2-methyl-6-acyl naphthalene, which comprises the following specific steps: S1, under the conditions of nitrogen atmosphere and anhydrous, 10.0g of aluminum chloride crystals were weighed into an explosion-proof glass test tube, then white triethylamine hydrochloride powder was gradually added into the test tube, and the glass test tube was oscillated at a frequency of 110Hz at 30℃ to obtain a brown viscous transparent liquid; wherein by adjusting the amount of triethylamine hydrochloride powder and the temperature, ionic liquid (IL-X-AlCl3) with different contents of aluminum chloride can be obtained, X represents the amount-of-substance content of aluminum chloride added in the ionic liquid, and in this example X=0.55, so the ionic liquid can be represented as IL-0.55-AlCl3; S2, under the conditions of nitrogen atmosphere, acetyl chloride at 0℃ was slowly added into ionic liquid (IL-0.55-AlCl3) at 0℃ to prepare an acylation reagent containing 20.0wt% acetyl chloride; S3, 2-methylnaphthalene was weighed and dissolved in cyclohexane to prepare a 2-methylnaphthalene solution containing 35.0wt% 2-methylnaphthalene; S4, 1.0g of the 2-methylnaphthalene solution was taken into a reaction tube, and the reaction tube was placed in an ethanol constant temperature liquid at 0℃. Under the conditions of nitrogen atmosphere, the above-mentioned acylation reagent was added dropwise into the 2-methylnaphthalene solution (reaction tube), and stirring was started at the same time during the dropping process, and the stirring speed was 400rpm. After the dropping was completed, the reaction was continued for 0.5 hours with stirring. S5, after the reaction, the reaction product was first quenched with 6.0mol / L hydrochloric acid solution, and then extracted with cyclohexane for 3 times, and the extracted liquid was neutralized, dried, and 2-methyl-6-acetylnaphthalene product was obtained, with a yield of 95.3%.

[0030] The product of the above Example 3 was analyzed by liquid chromatography (HPLC analysis) and gas chromatography (GC analysis): ①HPLC analysis: Agilent 1100 type high performance liquid chromatograph; C18 separation column; flow rate 0.2mL / min; mobile phase ratio V(acetonitrile):V(water)=50:50; detector wavelength 245nm.

[0031] ii) GC analysis: GC-2014C gas chromatograph; KB-5 capillary column; split ratio 60; vaporization chamber temperature 280℃; initial column temperature 140℃, holding for 2 minutes, increasing to 320℃ at a rate of 20℃ / min, holding for 5 minutes, decreasing; hydrogen flame detector.

[0032] Results: The comprehensive results of the product obtained in Example 3 after liquid chromatography analysis and gas chromatography analysis showed that the content of 2-methyl-6-acetylnaphthalene in the product was 95.8wt%, which exhibited high product purity. The method of the present application not only overcomes the problems faced by the existing 2-methyl-6-acetylnaphthalene synthesis method, but also has high product yield and high purity.

[0033] In addition, the aluminum trichloride in the prior art (CN114621066A) cannot be fully dissolved, and there are solid-liquid two phases, so the strong mixing method is advantageous, but this strong mixing method cannot achieve the effect of liquid-liquid mixing, while the ionic liquid of the present application can achieve it, and there is no solid-liquid reaction, and the mixing effect is obvious, therefore the present application uses ionic liquid as the reaction medium, which not only simplifies the preparation process, but also has high product yield and obvious advantages.

[0034] The above is only used to explain the present application, and is not used to limit the present application. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A method for preparing 2-methyl-6-acylnaphthalene, characterized in that, The method includes the following steps: S1. Under a protective atmosphere and anhydrous conditions, aluminum trichloride crystals are mixed with triethylamine hydrochloride powder to obtain an ionic liquid; S2. Under a protective atmosphere, acyl chloride is added dropwise to the ionic liquid to obtain an acylation reagent for acyl chloride; S3. Dissolve 2-methylnaphthalene to obtain a 2-methylnaphthalene solution; S4. Under a protective atmosphere and low temperature conditions, the acylation reagent is added to the 2-methylnaphthalene solution, and the mixture is stirred to carry out the reaction. S5. After the reaction, the reaction product is first quenched with hydrochloric acid solution, then extracted, the extract is neutralized and dried to obtain the 2-methyl-6-acylnaphthalene product.

2. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, In step S1, the reaction temperature is 20–30°C, and the reaction is oscillating at a frequency of 100–140 Hz.

3. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, The amount of aluminum trichloride added in step S1 in the ionic liquid is 55-70%.

4. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, Step S2: Under a protective atmosphere, acyl chloride at 0–3°C is added dropwise to an ionic liquid at 0–5°C to obtain an acylation reagent containing 5.0–20.0 wt% acyl chloride; wherein the acyl chloride is selected from acetyl chloride or propionyl chloride.

5. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, Step S3: Dissolve 2-methylnaphthalene in cyclohexane to obtain a 2-methylnaphthalene solution with a content of 20.0-40.0 wt%.

6. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, Step S4: Under a protective atmosphere and at a low temperature not exceeding 5°C, the acylation reagent is added dropwise to the 2-methylnaphthalene solution, and the mixture is stirred at a speed of 300-400 rpm.

7. The method for preparing 2-methyl-6-acylnaphthalene according to claim 1, characterized in that, Step S5: After the reaction, the reaction product is first quenched with a hydrochloric acid solution of concentration 3.0-8.0 mol / L, and then extracted 1-5 times with an equal volume of cyclohexane. The extract is then neutralized and dried to obtain the 2-methyl-6-acylnaphthalene product.