A process for the preparation of dibenzoyl-p-benzoquinone dioxime

Abstract

The application provides a preparation method of dibenzoyl-p-benzoquinone dioxime. The method comprises the following steps: (1) adding a heteropoly acid catalyst into an ethanol solution of p-benzoquinone dioxime to obtain a mixed solution; (2) adding an ethanol solution of benzoic acid into the obtained mixed solution, and then performing a reaction; after the reaction is completed, filtering the obtained reaction liquid, drying and screening the obtained filter residue to obtain dibenzoyl-p-benzoquinone dioxime. The method uses p-benzoquinone dioxime and benzoic acid as raw materials, uses ethanol as a reaction solvent, uses a heteropoly acid as a catalyst for a condensation reaction, and synthesizes dibenzoyl-p-benzoquinone dioxime in one step. The solvent ethanol used in the method can be recovered and reused through reduced pressure distillation, and the catalyst heteropoly acid can be recycled and reused after being filtered, so that the output of acidic production wastewater is reduced, the generation of strong corrosive hydrogen chloride gas is avoided, and the green environmental protection requirement is met.

Description

Technical Field

[0001] This invention belongs to the field of synthesis and preparation technology of dibenzoyl-p-benzoquinone dioxime, specifically relating to a green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime. Background Technology

[0002] Benzoyl-p-benzoquinone dioxime is a high-performance rubber vulcanizing agent commonly used in butyl rubber, natural rubber, and styrene-butadiene rubber. Its properties are similar to p-benzoquinone dioxime, but due to the presence of a benzoyl group in its structure, it exhibits stronger vulcanization retardation and better scorch resistance. During vulcanization, diphenylpropizoazole disulfide is typically used as an accelerator in the vulcanization system, resulting in faster vulcanization, better aging resistance of the rubber, and improved heat resistance and ozone resistance of rubber products. Furthermore, benzoyl-p-benzoquinone dioxime can also be used as a highly effective vulcanization accelerator in peroxide vulcanization, offering rapid vulcanization and high elongation, making it particularly suitable for butyl rubber used in the production of inner tubes, water tires, vulcanized bladders, insulation layers for wires and cables, and general rubber products.

[0003] In existing industrial processes, the main methods for synthesizing benzoyl-p-benzoquinone dioxime include: Chinese patent document CN101293857A discloses a method for preparing benzoyl-p-benzoquinone dioxime, which uses chloroform as a solvent and p-benzoquinone dioxime and benzoyl chloride as raw materials to synthesize benzoyl-p-benzoquinone dioxime in one step. While this method is simple and easy to implement, it suffers from long reaction times, high material consumption, low product yield, and lacks detailed information on product quality. Furthermore, chloroform has a low boiling point and is highly volatile; it is also easily oxidized by light into highly toxic phosgene, which is detrimental to human health and environmental protection requirements. Additionally, because benzoyl-p-benzoquinone dioxime is soluble in chloroform, a portion of it dissolves in the chloroform solvent, resulting in a low product yield. Moreover, the portion of the product dissolved in chloroform is difficult to recover, leading to cost losses. Chinese patent document CN102617398A discloses a method for manufacturing p,p-dibenzoylbenzoquinone dioxime compounds. This method uses ethylene glycol dimethyl ether as a solvent, p-benzoquinone dioxime and benzoyl chloride as raw materials, and triethylamine as a chelating agent to synthesize p-benzoylbenzoquinone dioxime. This synthesis process consumes a large amount of organic solvent, approximately 5 to 10 times the mass of p-benzoquinone dioxime, resulting in significant space consumption and wasted equipment space during industrial production. Furthermore, the high price of ethylene glycol dimethyl ether hinders cost control. In conclusion, this synthesis method is not suitable for large-scale industrial production.

[0004] Furthermore, both of the above synthesis methods use p-benzoquinone dioxime and benzoyl chloride as raw materials, and hydrogen chloride gas is generated during the synthesis process. Hydrogen chloride gas is highly corrosive and can form explosive mixtures with air. Moreover, in industrial production, it inevitably causes chloride ion corrosion to reaction equipment, thus creating safety hazards and increasing the difficulty of waste treatment. In addition, both the raw material benzoyl chloride and the generated hydrogen chloride gas have strong, pungent odors, which are detrimental to human health. Therefore, neither of these synthesis methods is suitable for large-scale industrial production.

[0005] Therefore, it is of great significance to study a simple, mild, and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime. The method uses p-benzoquinone dioxime and benzoic acid as raw materials, ethanol as the reaction solvent, and a heteropoly acid as a catalyst for the condensation reaction, synthesizing dibenzoyl-p-benzoquinone dioxime in one step. The ethanol solvent used in this method can be recovered and reused through vacuum distillation, and the heteropoly acid catalyst can be recovered and reused after filtration, reducing the generation of acidic production wastewater and avoiding the generation of highly corrosive hydrogen chloride gas, thus meeting green environmental protection requirements. Furthermore, the method of this invention is simple and easy to implement, shortens the reaction process, reduces side reactions, lowers production costs, and minimizes waste. The obtained dibenzoyl-p-benzoquinone dioxime is a purplish-gray powder with high purity, providing a new approach for the synthesis of dibenzoyl-p-benzoquinone dioxime.

[0007] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime includes the following steps:

[0008] (1) Add a heteropolyacid catalyst to an ethanol solution of p-benzoquinone dioxime to obtain a mixed solution;

[0009] (2) Add an ethanol solution of benzoic acid to the resulting mixed solution and then react; after the reaction is completed, filter the resulting reaction solution, dry and sieve the resulting filter residue to obtain dibenzoyl-p-benzoquinone dioxime.

[0010] According to a preferred embodiment of the present invention, the mass ratio of p-benzoquinone dioxime to ethanol in the ethanol solution of p-benzoquinone dioxime in step (1) is 1:(0.5~2).

[0011] According to a preferred embodiment of the present invention, the heteropolyacid catalyst in step (1) is a Dawson-type phosphotungsten heteropolyacid with the molecular formula H6P2W. 18 O 62·nH₂O, where n is an integer from 8 to 15; the mass ratio of the heteropolyacid catalyst to p-benzoquinone dioxime is (0.1~0.5):1; the particle size of the heteropolyacid catalyst is 0.8mm-1cm, and it is a blocky solid; the preparation method of the heteropolyacid catalyst is existing technology in this field, and can be found in the reference (Cao Xiaohua, Wang Yuanping, Xu Changlong, et al. H6P2W). 18 O 62 / Preparation, characterization and catalytic synthesis of acetylsalicylic acid from kaolin [J]. Chemical Industry and Engineering Progress, 2014, 33(05):1205-1209+1241.)

[0012] According to a preferred embodiment of the present invention, in step (2), the mass ratio of benzoic acid to ethanol in the benzoic acid ethanol solution is 1:(1.5~3); and the molar ratio of benzoic acid to p-benzoquinone dioxime is (2.0~2.5):1.

[0013] According to a preferred embodiment of the present invention, the ethanol solution of benzoic acid in step (2) is added dropwise to the mixed solution for a time of 30 min to 60 min and a temperature of 30 °C to 40 °C.

[0014] According to a preferred embodiment of the present invention, the temperature of the reaction in step (2) is 35°C to 40°C, and the reaction time is 1h to 3h.

[0015] According to a preferred embodiment of the present invention, in step (2), the obtained reaction solution is filtered, and the obtained filtrate is subjected to vacuum distillation to recover the solvent ethanol.

[0016] According to a preferred embodiment of the present invention, the drying in step (2) is performed at 80°C to 90°C until constant weight.

[0017] According to a preferred embodiment of the present invention, in step (2), the filter residue is a mixture of dibenzoyl-p-benzoquinone dioxime and a heteropoly acid catalyst; the dried filter residue is sieved through a 60-mesh sieve to obtain a powdered dibenzoyl-p-benzoquinone dioxime product, and the heteropoly acid catalyst is recovered from the sieve residue; the product of the present invention is in powder form, and the catalyst is a large particle solid. After sieving through a 60-mesh sieve, a powdered product and a granular sieve residue are obtained. The sieve residue is the catalyst, which can be recycled.

[0018] The reaction route of this invention is shown below:

[0019]

[0020] The technical features and beneficial effects of this invention are as follows:

[0021] 1. In this invention, ethanol is used as the reaction solvent, which improves the dispersibility of the reaction system, accelerates the reaction rate, shortens the reaction time, and makes the reaction more complete. Meanwhile, both p-benzoquinone dioxime and benzoic acid are readily soluble in ethanol, while the product dibenzoyl-p-benzoquinone dioxime is insoluble in ethanol, facilitating post-reaction processing, improving product yield, and reducing energy consumption. Furthermore, the solvent ethanol can be recovered and reused in the filtrate, reducing material consumption and helping to reduce production costs.

[0022] 2. This invention uses benzoic acid as the raw material for synthesizing dibenzoyl-p-benzoquinone dioxime, which is safer and more reliable than benzoyl chloride in traditional processes. This is because traditional synthesis processes generate highly corrosive hydrogen chloride gas, which easily causes severe corrosion to reaction equipment. Furthermore, hydrogen chloride gas can react with various metals to produce hydrogen gas, can form explosive mixtures with air, and react with cyanide to produce highly toxic hydrogen cyanide, posing a significant safety hazard. However, by using weakly acidic benzoic acid instead of benzoyl chloride, the byproduct changes from hydrogen chloride gas to water. The reaction process is safe and mild, avoiding the generation of highly corrosive gases and acidic wastewater, resulting in high safety and facilitating industrial production.

[0023] 3. This invention uses heteropolyacids as catalysts for the synthesis of dibenzoyl-p-benzoquinone dioxime. Heteropolyacids, as a novel type of multifunctional catalyst, exhibit high catalytic activity compared to other catalysts (such as concentrated sulfuric acid). They are safer and more stable during the reaction process, cause no environmental pollution, and have low corrosiveness to equipment, making them a promising green catalyst. Furthermore, this type of solid catalyst can be recovered and reused from the residue of the filter residue through filtration, drying, and sieving, avoiding the generation of organic waste and reducing production costs.

[0024] 4. The synthesis method of the present invention involves no water throughout the entire process, and the filtrate obtained by filtration can be reused as an organic solvent, avoiding the generation of production wastewater and facilitating the implementation of green and environmentally friendly requirements.

[0025] 5. The synthesis method used in this invention has optimized and adjusted the relevant process parameters, reduced the consumption of raw materials, and shortened the reaction time, thereby enabling the rapid and simple synthesis of the target product dibenzoyl-p-benzoquinone dioxime. The synthesis method of this invention is simple and easy to implement, with mild conditions, high safety, few side reactions, low waste production, short reaction time, high efficiency, and is easy to scale up for industrial production. Detailed Implementation

[0026] 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 embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The methods and apparatus not described in detail in this invention are all prior art and will not be elaborated further.

[0028] To further understand the present invention, the following detailed description of the synthesis and preparation method of dibenzoyl-p-benzoquinone dioxime provided by the present invention is provided in conjunction with the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0029] The Dawson-type phosphotungsten heteropolyacid catalyst used in the examples has the structural formula H6P2W. 18 O 62 ·13H2O, with a particle size of 1mm-1cm, is a blocky solid.

[0030] Example 1

[0031] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime includes the following steps:

[0032] 1) Add 50g of p-benzoquinone dioxime and 75g of ethanol to a reaction vessel and stir to obtain an ethanol solution of p-benzoquinone dioxime; add 15g of Dawson-type phosphotungsten heteropolyacid catalyst to the obtained ethanol solution of p-benzoquinone dioxime to obtain a mixed solution.

[0033] 2) Dissolve 101.67g of benzoic acid in 200g of ethanol, mix well to obtain an ethanol solution of benzoic acid;

[0034] 3) Add the ethanol solution of benzoic acid from step 2) dropwise to the mixed solution obtained in step 1), at a temperature of 35℃~38℃ for 40 min; after the addition is complete, continue stirring the reaction at 38℃ for 1.5 h to obtain the reaction solution;

[0035] 4) Filter the reaction solution obtained in step 3). After filtration, filter residue and filtrate are obtained. The solvent ethanol is recovered by vacuum distillation of the filtrate. The filter residue is a mixture of dibenzoyl-p-benzoquinone dioxime and heteropolyacid catalyst.

[0036] 5) The filter residue obtained in step 4) is dried to constant weight at 85°C and then sieved through a 60-mesh sieve. The dibenzoyl-p-benzoquinone dioxime product is in powder form, while the catalyst is a large solid particle that will not break during the reaction. After sieving through a 60-mesh sieve, powdered dibenzoyl-p-benzoquinone dioxime product and granular residue are obtained. The heteropolyacid catalyst is recovered from the residue.

[0037] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 1 was 123.68 g, the yield (based on p-benzoquinone dioxime) was 98.66%, the appearance was a purplish-gray powder, and the purity (HPLC) was 98.71%.

[0038] Example 2

[0039] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is described in Example 1, except that the 15g phosphotungstic heteropolyacid catalyst in step 1) is replaced with 5g phosphotungstic heteropolyacid catalyst.

[0040] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 2 was 123.04 g, the yield (based on p-benzoquinone dioxime) was 98.15%, the appearance was a purplish-gray powder, and the purity (HPLC) was 98.27%.

[0041] Example 3

[0042] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is described in Example 1, except that the 15g phosphotungstic heteropolyacid catalyst in step 1) is replaced with 25g phosphotungstic heteropolyacid catalyst.

[0043] According to the test and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 3 was 123.35 g, the yield (based on p-benzoquinone dioxime) was 98.39%, the appearance was a purplish-gray powder, and the purity (HPLC) was 98.14%.

[0044] Example 4

[0045] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is as described in Example 1, except that in step 2), dissolving 101.67g of benzoic acid in 200g of ethanol is replaced by dissolving 92.83g of benzoic acid in 185g of ethanol.

[0046] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 4 was 121.81 g, the yield (based on p-benzoquinone dioxime) was 97.17%, the appearance was a purplish-gray powder, and the purity (HPLC) was 97.69%.

[0047] Example 5

[0048] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is as described in Example 1, except that in step 2), dissolving 101.67g of benzoic acid in 200g of ethanol is changed to dissolving 110.51g of benzoic acid in 220g of ethanol.

[0049] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 5 was 123.12 g, the yield (based on p-benzoquinone dioxime) was 98.21%, the appearance was a purplish-gray powder, and the purity (HPLC) was 98.23%.

[0050] Example 6

[0051] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is described in Example 1, except that the reaction time in step 3) is changed from 1.5 h to 1 h.

[0052] According to the test and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 6 was 122.53 g, the yield (based on p-benzoquinone dioxime) was 97.74%, the appearance was a purplish-gray powder, and the purity (HPLC) was 97.96%.

[0053] Example 7

[0054] A green and environmentally friendly method for preparing dibenzoyl-p-benzoquinone dioxime is described in Example 1, except that the reaction time in step 3) is changed from 1.5 h to 3 h.

[0055] According to the test and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Example 7 was 123.41 g, the yield (based on p-benzoquinone dioxime) was 98.44%, the appearance was a purplish-gray powder, and the purity (HPLC) was 98.08%.

[0056] Comparative Example 1

[0057] A method for preparing dibenzoyl-p-benzoquinone dioxime is described in Example 1, except that phosphotungstic heteropoly acid catalyst is not added in step 1).

[0058] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Comparative Example 1 was 88.62 g, the yield (based on p-benzoquinone dioxime) was 70.69%, the appearance was a purplish-brown powder, and the purity (HPLC) was 84.57%.

[0059] Comparative Example 2

[0060] A method for preparing dibenzoyl-p-benzoquinone dioxime is as described in Example 1, except that the ethanol solution of benzoic acid in steps 2) and 3) is replaced with 117.15g of benzoyl chloride.

[0061] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Comparative Example 2 was 121.06 g, the yield (based on p-benzoquinone dioxime) was 96.57%, the appearance was a purplish-gray powder, and the purity (HPLC) was 97.32%.

[0062] Comparative Example 3

[0063] A method for preparing dibenzoyl-p-benzoquinone dioxime is as described in Comparative Example 2, except that: in step 1), no phosphotungsten heteropolyacid catalyst is added.

[0064] After testing and measurement, the mass of dibenzoyl-p-benzoquinone dioxime prepared in Comparative Example 3 was 84.35 g, the yield (based on p-benzoquinone dioxime) was 67.28%, the appearance was a purplish-brown powder, and the purity (HPLC) was 79.66%.

[0065] Table 1 Comparison of results for dibenzoyl-p-benzoquinone dioxime obtained in the examples and comparative examples

[0066]

[0067] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing dibenzoyl-p-benzoquinone dioxime, comprising the following steps: (1) A heteropolyacid catalyst was added to an ethanol solution of p-benzoquinone dioxime to obtain a mixed solution; the heteropolyacid catalyst was a Dawson-type phosphotungsten heteropolyacid with the molecular formula H6P2W 18 O 62 ·nH2O, where n is an integer from 8 to 15; (2) Add an ethanol solution of benzoic acid to the obtained mixed solution and then carry out the reaction; after the reaction is completed, filter the obtained reaction solution, dry and sieve the obtained filter residue to obtain dibenzoyl-p-benzoquinone dioxime; the molar ratio of benzoic acid to p-benzoquinone dioxime is (2.0~2.5):

1.

2. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, In step (1), the mass ratio of p-benzoquinone dioxime to ethanol in the ethanol solution is 1:(0.5~2).

3. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, The mass ratio of the heteropolyacid catalyst to p-benzoquinone dioxime in step (1) is (0.1~0.5):1; the particle size of the heteropolyacid catalyst is 0.8mm-1cm.

4. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, In step (2), the mass ratio of benzoic acid to ethanol in the benzoic acid ethanol solution is 1:(1.5~3).

5. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, In step (2), the ethanol solution of benzoic acid is added dropwise to the mixed solution over a period of 30 min to 60 min, and at a temperature of 30°C to 40°C.

6. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, The reaction temperature in step (2) is 35℃~40℃, and the reaction time is 1h~3h.

7. The method for preparing dibenzoyl-p-benzoquinone dioxime according to claim 1, characterized in that, In step (2), the filter residue is a mixture of dibenzoyl-p-benzoquinone dioxime and heteropoly acid catalyst; the dried filter residue is sieved through a 60-mesh sieve to obtain powdered dibenzoyl-p-benzoquinone dioxime product, and the heteropoly acid catalyst is recovered from the sieve residue.

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