Synthetic method of p-chloromethyl styrene

Abstract

The invention discloses a method for synthesizing p-chloromethyl styrene, which comprises the following steps: carrying out chloromethylation reaction on beta-bromophenylethane, paraformaldehyde and thionyl chloride to generate p-chloromethyl bromophenylethane, then carrying out toluene extraction and static layering, carrying out water washing and alkali washing on an organic phase in sequence, and carrying out reduced pressure distillation to obtain p-chloromethyl styrene. Under the action of strong base, hydrogen bromide is removed through elimination reaction to synthesize crude p-chloromethyl styrene, and the crude p-chloromethyl styrene is acidified and rectified to obtain the product p-chloromethyl styrene. The method solves the problem of generation of a large amount of three wastes in a conventional production route, optimizes the production process, improves the reaction conversion rate from 60-80% to 95% or above, and further improves the yield from 50-60% to 85% or above.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical material preparation, and particularly relates to a method for synthesizing p-chloromethylstyrene. Background Art

[0002] Due to its special functional group structure, p-chloromethylstyrene has many important chemical properties, so it has very important applications in the chemical industry and is an indispensable chemical raw material. Its application fields include coatings, inks, pharmaceuticals, pesticides, dyes, pigments, etc.

[0003] Due to the wide application of polymer materials at the present stage, p-chloromethylstyrene has a wide range of applications. For example, p-chloromethylstyrene can be polymerized on the surface of a silicon material with double bonds, and then quaternized to prepare a new type of strong anion chromatography column packing; it can also be attached to the surface of carbon nanotubes after polymerization of p-chloromethylstyrene, realizing the chemical modification of carbon nanotubes; related derivatives of p-chloromethylstyrene can also be used as organic photosensitive materials to replace inorganic selenium photosensitive materials, etc.

[0004] However, due to the factors of the current process itself, a large amount of waste acid, waste alkali, etc. are generated during the production process, resulting in high three-waste treatment costs. Isomer impurities and polymerization impurities are easily generated during the production of p-chloromethylstyrene, the overall yield is low, and it is difficult to obtain a product with a purity greater than 95.0%.

[0005] There are mainly the following several synthesis methods for chloromethylstyrene: 1. Using the phase transfer catalysis method, with p-chloromethyl-α-bromoethylbenzene and potassium hydroxide as raw materials, toluene as a solvent, and adding a phase transfer catalyst to synthesize p-chloromethylstyrene:

[0006] The raw materials used in this method are difficult to synthesize, mostly custom products, so the price is high and they are not easily available, making the cost of synthesizing p-chloromethylstyrene relatively high; 2. Using 1-(2-chloroethyl)-4-(chloromethyl)benzene dissolved in a tetrahydrofuran solvent to carry out an elimination reaction under alkaline conditions to synthesize p-chloromethylstyrene:

[0007] During the synthesis process of this method, isomer impurities are easily generated, and the two-step yield is only about 70%, with a relatively low yield, which is not suitable for industrial production; 3. Under the catalysis of a Lewis acid, directly carrying out chloromethylation on styrene to obtain p-chloromethylstyrene:

[0008] This synthetic process route is short and the raw materials are easily available. However, the yield is relatively low, the direct chloromethylation selectivity is not good, and the later separation is difficult, so it is not suitable for the production of p-chloromethylstyrene with high purity.

[0009] 4. Using p-methylbenzonitrile as the starting material, first carry out chlorination, then convert the cyano group into an aldehyde group, and then synthesize phenylethyl alcohol, and dehydrate to synthesize p-chloromethylstyrene:

[0010] This synthetic route is too long, there are many side reactions, it is not easy to purify, and the overall yield is relatively low. Summary of the Invention

[0011] The present invention overcomes the problems in the common production process: 1. Using zinc chloride for chloromethylation will cause a large amount of hazardous waste and high costs for the treatment of the three wastes; 2. Reasonably collecting the tail gas and solid waste during the process can be used as by-products to reduce the cost of treating the three wastes; this process uses a new chloromethylation route and optimizes the process of converting the three wastes into by-products, greatly saving the production cost.

[0012] The object of the present invention is to solve the generation of a large amount of three wastes in the conventional production route, optimize the production process, improve the reaction conversion rate from 60 - 80% to more than 95%, and further improve the yield from 50 - 60% to more than 85%.

[0013] To achieve the above object, the present invention discloses the following technical content: A method for synthesizing p-chloromethylstyrene, which is characterized by the following steps: (1) Chloromethylation reaction: Using sulfuric acid and acetic acid as solvents, mix β-bromoethylbenzene and paraformaldehyde in a molar ratio of 1:1 - 1:1.5, add 98% sulfuric acid and 99% acetic acid, control the temperature at 30 - 50 °C, and dropwise add thionyl chloride, where the molar ratio of β-bromoethylbenzene to thionyl chloride is 1:0.9 - 1:1.1, keep the temperature at 30 - 80 °C and react for 8 - 15 hours. After the reaction is completed, add toluene to dissolve, carry out water washing and layering, then carry out alkali washing and filtration. The obtained crude intermediate is then distilled to remove the residual water to obtain the intermediate p-chloromethylbromoethane; (2) Elimination reaction: Using toluene as a solvent, mix p-chloromethylbromoethane and sodium hydroxide in a molar ratio of 1:1 - 1:1.5, add an appropriate amount of polyethylene glycol (400 - 2000: 7g - 10g) as a phase transfer catalyst, control the temperature at 20 - 40 °C, keep the temperature and react for 5 - 15 hours. After the reaction is completed, first separate the aqueous phase, wash the organic phase with hydrobromic acid, and the aqueous phase can be treated to obtain sodium bromide as a by-product; the organic phase is concentrated, toluene is distilled off, and the residue is purified by rectification to obtain p-chloromethylstyrene with high purity The present invention is described in more detail as follows: β-bromoethylbenzene, paraformaldehyde and thionyl chloride undergo a chloromethylation reaction to generate p-chloromethylbromoethylbenzene. Then, toluene extraction and static layering are carried out. After the organic phase is washed with water and then with alkali successively, hydrogen bromide is removed by an elimination reaction under the action of a strong base to synthesize crude p-chloromethylstyrene. The crude product is acidified and rectified to obtain the product p-chloromethylstyrene.

[0014] (1) Chloromethylation reaction: Using sulfuric acid and acetic acid as solvents, the main raw material β-bromoethylbenzene reacts with paraformaldehyde and thionyl chloride. The reaction equation is as follows:

[0015] β-bromoethylbenzene and paraformaldehyde are mixed in a molar ratio of 1:1 to 1:1.5, 98% sulfuric acid and 99% acetic acid are added, the temperature is controlled at 30 - 50 °C, and thionyl chloride is added dropwise. The molar ratio of β-bromoethylbenzene to thionyl chloride is 1:0.9 to 1:1.1. After heat preservation at 30 - 80 °C for 8 - 15 hours, toluene is added for dissolution after the reaction is completed, followed by water washing and layering, and then alkali washing and filtration. The residual water in the obtained intermediate crude product is distilled off to obtain the intermediate p-chloromethylbromoethylbenzene, with a conversion rate of 95 - 98% and a yield of 90 - 95%.

[0016] (2) Elimination reaction: Using toluene as a solvent, the main raw material p-chloromethylbromoethylbenzene undergoes elimination under alkaline conditions to obtain p-chloromethylstyrene. The reaction equation is as follows:

[0017] p-chloromethylbromoethylbenzene and sodium hydroxide are mixed in a molar ratio of 1:1 to 1:1.5, and an appropriate amount of polyethylene glycol (400 - 2000) is added as a phase transfer catalyst. The temperature is controlled at 20 - 40 °C, and the reaction is carried out with heat preservation for 5 - 15 hours. After the reaction ends, the aqueous phase is separated first, and the organic phase is washed with hydrobromic acid. Sodium bromide can be obtained from the treatment of the aqueous phase as a by-product; the organic phase is concentrated, toluene is distilled off, and the residue is purified by rectification to obtain p-chloromethylstyrene with a higher purity. The reaction conversion rate is 95 - 98% and the yield is 94.5%.

[0018] This invention mainly examines two aspects: 1. A new production process for chloromethylation to replace the traditional process of methylation using Lewis acid: (In the CN_110452089_A patent, anhydrous zinc chloride is used for chloromethylation, and the yield is ~68.5%). The key point is to solve the problem of generating a large amount of difficult-to-treat solid waste during the traditional chloromethylation production process. The difficulty of the invention lies in the screening of the process. Since the traditional process is already very mature and widely used in actual production, it is very difficult to screen out a suitable process plan; Conclusion: Chloromethylation with conventional Lewis acids not only has low selectivity and poor yield, but also generates a large amount of hazardous waste. However, using β-bromoethylbenzene, paraformaldehyde and thionyl chloride to carry out chloromethylation reaction under the conditions of sulfuric acid and acetic acid to produce p-chloromethylbromoethylbenzene can have a selectivity of more than 90%, reducing the difficulty of later separation. Conclusion: After the reaction is optimized, the yield can be increased to more than 90%, the purification burden is small, and the waste liquid is neutralized with hydrobromic acid, which can improve the material utilization rate without affecting the conversion rate, and by-products can be obtained through recovery treatment.

[0019] In the elimination reaction, acidification with hydrobromic acid can unify the components in the three wastes. The key is to solve the difficult treatment of mixed salts in the waste liquid and the low recovery and utilization rate. The difficulty of the invention lies in cost control and the rational disposal of later waste.

[0020] This method uses β-bromoethylbenzene as the main raw material, synthesizes the intermediate p-chloromethylbromoethylbenzene through chloromethylation reaction, then reacts with strong base for elimination reaction to obtain crude p-chloromethylstyrene, and purifies it through rectification operation to obtain p-chloromethylstyrene with higher purity. The invention focuses on optimizing the chloromethylation process in the reaction, using thionyl chloride instead of Lewis acids such as zinc chloride in the traditional process, which can avoid generating a large amount of difficult-to-treat hazardous waste, optimize the composition of the three wastes, rationally produce by-products, overall improve the reaction conversion rate, and optimize the production cost.

[0021] The innovation points of the invention are: 1. Using sulfuric acid / acetic acid as the solvent, β-bromoethylbenzene reacts with thionyl chloride and paraformaldehyde for chloromethylation. This method not only has a conversion rate of more than 95%, but also completely avoids the generation of a large amount of hazardous waste, and the acidic tail gas generated by the reaction can be absorbed and used as a by-product; 2. Neutralization treatment with hydrobromic acid can improve the material utilization rate without affecting the conversion rate, and by-products can be obtained through recovery treatment.

[0022] The positive effects of the chloromethylation process and dehydration acidification process disclosed by the invention compared with the prior art are: 1. The total reaction conversion rate of the two-step reaction reaches 90-96%, greatly improving the production yield; 2. No hazardous waste is generated during chloromethylation, ensuring green production while also improving production efficiency; 3. Reasonably optimize the treatment of the three wastes, improve the material utilization rate, protect the environment, and reduce the production cost. Specific embodiments

[0023] The present invention will be described below through specific implementation examples. Unless otherwise specified, the technical means used in the present invention are all methods well known to those skilled in the art. In addition, the implementation examples should be understood as illustrative and not limiting the scope of the present invention. The essence and scope of the present invention are only defined by the claims. For those skilled in the art, various changes or modifications to the material components and dosages in these implementation examples without departing from the essence and scope of the present invention also fall within the protection scope of the present invention. The raw materials and reagents used in the present invention are all commercially available. Example

[0024] Step 1: Charge 597 g of β-bromoethylbenzene into a reaction flask, start stirring, add 99 g of paraformaldehyde, add 20 g of 98% sulfuric acid and 10 g of 99% acetic acid, control the temperature at 40 - 45°C, add dropwise 378 g of thionyl chloride, complete the addition dropwise in about 3 hours, keep the temperature at 50 - 55°C and react for 7 hours. Detect that the product conversion rate is 96%. After the reaction is completed, add 600 g of toluene to dissolve, then add 500 g of water for washing and layering. Slowly add 40 g of sodium carbonate to the organic phase, stir for 2 h, cool down to 0 - 30°C, filter. The mother liquor is the crude intermediate product. Distill off the residual water under reduced pressure at 60 - 70°C to obtain the intermediate p-chloromethylbromoethylbenzene. Weigh: 691.3 g, and the yield is 91.9%.

[0025] Step 2: Charge 691.3 g of p-chloromethylbromoethylbenzene into a reaction flask, start stirring, add 140 g of sodium hydroxide, add 7 g of polyethylene glycol 400, control the temperature at 30 - 35°C, keep the temperature and react for 12 hours. Detect that the product conversion rate is 95%. After the reaction ends, add 80 g of 48% hydrobromic acid and stir for 1 hour, let it stand for layering. Concentrate the aqueous phase to dryness to obtain sodium bromide. Concentrate the organic phase under reduced pressure, distill off toluene, and purify the residue by vacuum distillation to obtain p-chloromethylstyrene. Weigh: 428 g, and the yield is 94.7%. Example

[0026] Step 1: Charge 597 g of β-bromoethylbenzene into a reaction flask, start stirring, add 102 g of paraformaldehyde, add 22 g of 98% sulfuric acid and 12 g of 99% acetic acid, control the temperature at 40 - 45°C, add dropwise 403 g of thionyl chloride, complete the addition dropwise in about 3 hours, keep the temperature at 50 - 55°C and react for 6 hours. Detect that the product conversion rate is 97.2%. After the reaction is completed, add 600 g of toluene to dissolve, then add 500 g of water for washing and layering. Slowly add 48 g of sodium carbonate to the organic phase, stir for 2 h, cool down to 0 - 30°C, filter. The mother liquor is the crude intermediate product. Distill off the residual water under reduced pressure at 60 - 70°C to obtain the intermediate p-chloromethylbromoethylbenzene. Weigh: 696.6 g, and the yield is 92.6%.

[0027] Step 2: Charge 696.6 g of p-(chloromethyl)phenethyl bromide into the reaction flask, start stirring, add 150 g of sodium hydroxide, add 7 g of polyethylene glycol 1000, control the temperature at 30 - 35 °C, keep the reaction for 12 hours, and detect that the product conversion rate is 95.7%. After the reaction is completed, add 86 g of 48% hydrobromic acid and stir for 1 hour. Let it stand for liquid separation. The aqueous phase is concentrated to dryness to obtain sodium bromide. The organic phase is concentrated under reduced pressure. After toluene is distilled off, the residue is purified by vacuum distillation to obtain p-(chloromethyl)styrene. Weighing: 432.5 g, and the yield is 95.0%.

[0028] After the preferred embodiments of the detailed description, those skilled in the art can clearly understand that various changes and modifications can be made without departing from the above-mentioned scope and spirit of the patent application. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention all belong to the scope of the technical solution of the present invention. And the present invention is not limited by the implementation manners of the examples given in the specification either.

Claims

1. A method for synthesizing p-chloromethylstyrene, characterized in that Proceed as follows: (1) Chloromethylation reaction: using sulfuric acid and acetic acid as solvents, β-bromobenzene ethyl and polyformaldehyde are mixed in a molar ratio of 1:1 to 1:1.5, 98% sulfuric acid and 99% acetic acid are added, the temperature is controlled at 30-50°C, thionyl chloride is added dropwise, wherein the molar ratio of β-bromobenzene ethyl to thionyl chloride is 1:0.9 to 1:1.1, and the temperature is kept at 30-80°C for 8-15 hours. After the reaction is completed, toluene is added to dissolve, the mixture is washed with water and separated, and then washed with alkali and filtered. The residual water of the obtained intermediate crude product is evaporated to obtain the intermediate p-chloromethyl bromobenzene ethyl; (2) Elimination reaction: Using toluene as solvent, p-chloromethyl bromide and sodium hydroxide are mixed at a molar ratio of 1:1-1:1.5, and polyethylene glycol 400-2000:7g-10g is added as a phase transfer catalyst. The temperature is controlled at 20-40°C and the reaction is kept warm for 5-15 hours. After the reaction is completed, the aqueous phase is separated first, and the organic phase is washed with hydrobromic acid. Sodium bromide can be obtained as a by-product by treating the aqueous phase. The organic phase is concentrated, and after toluene is evaporated, the residue is purified by distillation to obtain p-chloromethylstyrene with high purity.

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