A method for synthesizing 2-pentylanthraquinone

Abstract

The application provides a synthesis method of 2-pentylanthraquinone, and belongs to the technical field of organic synthesis, and comprises the following steps: S1, adding lye to 2-(4-pentylbenzoyl) benzoic acid, stirring and dissolving under heating, filtering to obtain a 2-(4-pentylbenzoyl) benzoate solution, recrystallizing the 2-(4-pentylbenzoyl) benzoate solution to obtain 2-(4-pentylbenzoyl) benzoate, and recycling the mother liquor of the recrystallization; S2, adding sulfuric acid to the 2-(4-pentylbenzoyl) benzoate, stirring and dissolving to obtain a mixture, reacting the mixture after heating to obtain a reacted solution; S3, adding the reacted solution to ice water to precipitate a solid to obtain 2-pentylanthraquinone crude product, and purifying the 2-pentylanthraquinone crude product to obtain 2-pentylanthraquinone product. The preparation method realizes the purposes of improving the purity and yield of the product and reducing the generation amount of three wastes.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for synthesizing 2-pentylanthraquinone. Background Technology

[0002] Alkylanthraquinones are important fine chemical products widely used in pharmaceutical intermediates, dyes, resins, polymerization inhibitors, and hydrogen peroxide working fluid carriers. For example, 2-ethylanthraquinone, 2-butylanthraquinone, and 2-pentylanthraquinone are all essential components of the working fluid in hydrogen peroxide production. Compared to 2-ethylanthraquinone and 2-butylanthraquinone, 2-pentylanthraquinone has higher solubility in the working fluid, which is beneficial for expanding the capacity of hydrogen peroxide plants. In recent years, with the increasing demand for hydrogen peroxide and the continuous improvement of hydrogen peroxide processes, the market demand for the quality and quantity of 2-pentylanthraquinone has also been increasing daily.

[0003] Currently, Chinese patent application CN101602660A, entitled "A Production Process for 2-Pentylanthraquinone," discloses a process where 1 mol of phthalic anhydride and 2.33 mol of AlCl3 are added to a reaction flask, cooled to 15°C, and stirred for 30 minutes. Then, 6.38 mol of tert-amylbenzene and 0.1 mol of triethylamine are added to prepare 2-(4'-pentylbenzoyl)benzoic acid. The dried 2-(4'-pentylbenzoyl)benzoic acid is dissolved in trichlorobenzene, and fuming sulfuric acid is added dropwise while the mixture is cooled. The final reaction yields 2-pentylanthraquinone. This technical solution uses a large amount of tert-amylbenzene as both a reagent and a solvent in the reaction of pentylbenzene and phthalic anhydride, thus improving the conversion rate. While this process is simple and inexpensive, it generates a large amount of waste, which seriously harms the environment. Therefore, improving product purity and yield while reducing waste generation are key areas for process improvement. Summary of the Invention

[0004] In view of this, the present invention provides a method for synthesizing 2-pentylanthraquinone, which aims to improve the purity and yield of the product and reduce the amount of waste generated.

[0005] To achieve the above objective, the present invention provides a method for synthesizing 2-pentylanthraquinone, characterized by comprising the following steps:

[0006] S1. Add alkaline solution to 2-(4-pentylbenzoyl)benzoic acid, heat and stir to dissolve, filter to obtain 2-(4-pentylbenzoyl)benzoate solution, recrystallize the 2-(4-pentylbenzoyl)benzoate solution, filter, dry the filter cake to obtain 2-(4-pentylbenzoyl)benzoate, and recover the mother liquor of recrystallization. S2. Add sulfuric acid to 2-(4-pentylbenzoyl)benzoate, stir to dissolve and obtain a mixture. Heat the mixture and react to obtain a solution after reaction. S3. Add ice water to the solution after the reaction to precipitate the solid and obtain crude 2-pentylanthraquinone. Purify the crude 2-pentylanthraquinone to obtain the 2-pentylanthraquinone product.

[0007] Optionally, the purity of the 2-(4-pentylbenzoyl)benzoic acid is ≥85%.

[0008] Optionally, the purity of the 2-(4-pentylbenzoyl)benzoic acid is ≥90%.

[0009] Optionally, step S1 can be replaced by adding sulfate to 2-(4-pentylbenzoyl)benzoic acid, wherein the mass ratio of 2-(4-pentylbenzoyl)benzoic acid to sulfate is (5~7):1.

[0010] Optionally, the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide; the mass concentration of the alkaline solution is 20% to 30%.

[0011] Optionally, the mass ratio of 2-(4-pentylbenzoyl)benzoic acid to alkaline solution is (1.4~1.6):1.

[0012] Optionally, the recrystallization temperature is 5~15℃ and the recrystallization time is 1.5~2.5h.

[0013] Optionally, the mother liquor from the recrystallization can be recovered and used to prepare an alkaline solution.

[0014] Optionally, the sulfuric acid has a mass concentration of 98% to 105%.

[0015] Optionally, the reaction conditions after heating the mixture are as follows: the heating temperature is 80-120°C and the reaction time is 60-180 min.

[0016] Optionally, the organic solvent is toluene, xylene, or trimethylbenzene.

[0017] To achieve the above objectives, the present invention also provides a 2-pentylanthraquinone prepared by the above-mentioned synthetic method.

[0018] The above-described technical solution of the present invention has at least the following beneficial effects: This invention provides a method for synthesizing 2-pentylanthraquinone. By sequentially neutralizing and recrystallizing 2-(4-pentylbenzoyl)benzoic acid with alkali, the purity of the dehydration ring-closure reaction raw materials is improved, thereby reducing the generation of by-products in the ring-closure reaction. Furthermore, the sulfite generated after the reaction of 2-(4-pentylbenzoyl)benzoate with sulfuric acid can be used as an additive to increase the concentration of sulfite ions in sulfuric acid, thereby inhibiting the generation of by-products such as sulfonation, sulfones, and oxidation products. This further improves the yield and purity of the ring-closure reaction, while significantly reducing the generation of waste during the reaction process. The process is simple and easy to implement for industrial production. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0020] Example 1 Take 300g of 2-(4-pentylbenzoyl)benzoic acid (purity 95.1%) in a 1L glass beaker, add 200g of sodium hydroxide aqueous solution (mass fraction 20%) to the beaker, heat in a water bath to 70℃, stir to dissolve, filter out the insoluble matter, and obtain the filtrate as a 2-(4-pentylbenzoyl)benzoate solution. Place the 2-(4-pentylbenzoyl)benzoate solution in an ice-water bath, control the temperature of the filtrate at 15℃, and crystallize for 2 hours. After crystallization, filter by suction, and the filter cake is sodium 2-(4-pentylbenzoyl)benzoate. After drying, weigh 290.3g, and the crystallization yield is 90.1%. The mother liquor is recovered and can be reused for the preparation of the next batch of alkali solution.

[0021] The sodium 2-(4-pentylbenzoyl)benzoate obtained above was added to a 5L three-necked flask. 1305g of concentrated sulfuric acid (98.0% by mass) and 435g of fuming sulfuric acid (104.5% by mass) were added sequentially to the flask. After stirring and dissolving, the mixture was heated to 100℃ and reacted for 120 minutes. The reaction was then stopped and cooled to room temperature. The reaction solution was slowly added to 2000g of ice water, resulting in the precipitation of a solid. The solid was filtered, and the filter cake was crude 2-pentylanthraquinone. This was dissolved in 500g of toluene, and the insoluble matter was filtered off. The filtrate was a toluene solution of 2-pentylanthraquinone. The solution was washed twice with water, and the solvent was removed by rotary evaporation, yielding 246.2g of 2-pentylanthraquinone product. The product yield was 97.0%, and the product purity was 97.4%.

[0022] Example 2 Compared with Example 1, the only difference is that the 200g sodium hydroxide aqueous solution (20% by mass) in Example 1 was replaced with 200g potassium hydroxide aqueous solution (30% by mass), and the crystallization temperature was lowered from 15℃ to 5℃. All other raw materials and steps were the same as in Example 1. 315.7g of potassium 2-(4-pentylbenzoyl)benzoate was obtained, with a crystallization yield of 93.2%. 253.8g of 2-pentylanthraquinone product was obtained, with a product yield of 96.6% and a product purity of 96.9%.

[0023] Example 3 Compared with Example 1, the only difference is that the 1305g concentrated sulfuric acid (98.0% by mass) and 435g fuming sulfuric acid (104.5% by mass) in Example 1 were replaced with 1200g concentrated sulfuric acid (98% by mass), the reaction temperature was increased from 100℃ to 120℃, and the reaction time was reduced from 120min to 60min. All other raw materials and steps were the same as in Example 1. Sodium 2-(4-pentylbenzoyl)benzoate was obtained with a crystallization yield of 90.1%, yielding 221.3g of 2-pentylanthraquinone product with a product yield of 87.2% and a product purity of 95.5%.

[0024] Example 4 Compared with Example 1, the only difference is that the 200g sodium hydroxide aqueous solution (20%) in Example 1 was replaced with a sodium hydroxide solution prepared from 200g of crystallization mother liquor, and the 500g toluene was replaced with 500g of trimethylbenzene. All other raw materials and steps were the same as in Example 1. 292.0g of sodium 2-(4-pentylbenzoyl)benzoate was obtained with a crystallization yield of 90.6%, and 248.9g of 2-pentylanthraquinone product was obtained with a product yield of 97.5% and a product purity of 96.6%.

[0025] Example 5 Compared with Example 1, the only difference is that 300g of 2-(4-pentylbenzoyl)benzoic acid (purity 95.1%) and 50g of sodium sulfate were added to a 5L three-necked flask. 1350g of concentrated sulfuric acid (mass fraction 98.0%) and 450g of fuming sulfuric acid (mass fraction 104.5%) were added to the flask in sequence. After stirring and dissolving, the mixture was heated to 100℃ and reacted. After 120min, the reaction was stopped and cooled to room temperature. The reaction solution was then slowly added to 2000g of ice water, and a solid precipitated out. The mixture was filtered, and the filter cake was crude 2-pentylanthraquinone. After dissolving it in 500g of toluene, the insoluble matter was filtered out, and the filtrate was a toluene solution of 2-pentylanthraquinone. The mixture was washed twice with water, and the solvent was removed by rotary evaporation to obtain 247.5g of 2-pentylanthraquinone. The product yield was 87.8%, and the product purity was 96.2%.

[0026] Comparative Example 1 The difference from Example 1 is that step S1 was not performed.

[0027] Take 300g of 2-(4-pentylbenzoyl)benzoic acid (purity 95.1%) and add it to a 5L three-necked flask. Then add 1350g of concentrated sulfuric acid (mass fraction 98.0%) and 450g of fuming sulfuric acid (mass fraction 104.5%) to the flask. After stirring and dissolving, heat to 100℃ and react for 120 minutes. After cooling to room temperature, slowly add the reaction solution to 2000g of ice water. A solid precipitates out. Filter the solution. The filter cake is crude 2-pentylanthraquinone. Dissolve the crude product in 500g of toluene and filter out the insoluble matter. The filtrate is a toluene solution of 2-pentylanthraquinone. Wash twice with water and remove the solvent by rotary evaporation to obtain 240.5g of 2-pentylanthraquinone. The product yield is 85.3% and the product purity is 95.3%.

[0028] Comparative Example 2 Compared with Comparative Example 1, the difference is that the 1350g concentrated sulfuric acid (98.0% by mass) and 450g fuming sulfuric acid (104.5% by mass) in Comparative Example 1 were replaced with 1000g concentrated sulfuric acid (98.0% by mass) and 800g fuming sulfuric acid (104.5% by mass). The remaining steps and raw materials were the same as in Comparative Example 1, yielding 222.5g of 2-pentylanthraquinone, with a product yield of 78.9% and a product purity of 95.1%.

[0029] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing 2-pentylanthraquinone, characterized in that, Includes the following steps: S1. Add alkaline solution to 2-(4-pentylbenzoyl)benzoic acid, heat and stir to dissolve, filter to obtain 2-(4-pentylbenzoyl)benzoate solution, recrystallize the 2-(4-pentylbenzoyl)benzoate solution to obtain 2-(4-pentylbenzoyl)benzoate, and recover the mother liquor of the recrystallization. S2. Add sulfuric acid to 2-(4-pentylbenzoyl)benzoate, stir to dissolve and obtain a mixture. Heat the mixture and react to obtain a solution after reaction. S3. Add ice water to the solution after the reaction to precipitate the solid and obtain crude 2-pentylanthraquinone. Purify the crude 2-pentylanthraquinone to obtain the 2-pentylanthraquinone product.

2. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, Step S1 is replaced by adding sulfate to 2-(4-pentylbenzoyl)benzoic acid, wherein the mass ratio of 2-(4-pentylbenzoyl)benzoic acid to sulfate is (5~7):

1.

3. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide; the mass concentration of the alkaline solution is 20%~30%.

4. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The mass ratio of 2-(4-pentylbenzoyl)benzoic acid to alkaline solution is (1.4~1.6):

1.

5. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The recrystallization temperature is 5~15℃, and the recrystallization time is 1.5~2.5h.

6. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The sulfuric acid has a mass concentration of 98% to 105%.

7. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The mass ratio of 2-(4-pentylbenzoyl)benzoate to sulfuric acid is 1:(4~6).

8. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The reaction conditions after heating the mixture are as follows: the heating temperature is 80-120°C and the reaction time is 60-180 min.

9. The method for synthesizing 2-pentylanthraquinone according to claim 1, characterized in that, The crude 2-pentylanthraquinone is purified using an organic solvent, wherein the organic solvent is toluene, xylene, or trimethylbenzene.

10. 2-Pentylanthraquinone prepared by the synthetic method of 2-pentylanthraquinone as described in any one of claims 1-9.