A method for preparing high-purity acyl chloride products

Abstract

The present invention relates to the field of chemical synthesis technology, and in particular to a preparation method of a high-purity acyl chloride product, the preparation method is: S1, organic acid, thionyl chloride and amide catalyst are mixed, and multi-stage heating is used to react under agitation to obtain crude acyl chlorides; the multi-stage temperature-raising process is: the first-stage reaction temperature is 20-25 DEG C, and the reaction time is 30-40min; the second-stage reaction temperature is 35-45 DEG C, and the reaction temperature is 30-40min; the third-stage reaction temperature is 50-100 DEG C, and the reaction time is 40-70min; S2, crude acyl chlorides are distilled and purified to obtain the acyl chloride product. The preparation method of the present invention can prepare acyl chlorides in a continuous manner, so as to improve the production efficiency of acyl chlorides, reduce production time, and product purity is high, yield is high, and unreacted organic acid and catalyst can be reused as raw materials for next reaction, so as to save production cost.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-purity acyl chloride product, and belongs to the technical field of chemical synthesis. Background Art

[0002] Acyl chloride series products are mostly colorless to light yellow transparent liquids with a pungent odor. They react with water, alkali, alcohol, and oxidants to release heat. Common acyl chlorides include acetyl chloride, propionyl chloride, trimethylacetyl chloride, oxalyl chloride, isophthaloyl chloride, and terephthaloyl chloride.

[0003] Acid chloride is an important organic synthesis intermediate, widely used in medicine, pesticides and other organic synthesis industries. For example, propionyl chloride can be used as a pharmaceutical intermediate to produce naproxen, methoxytoin, choleretic acid, etc., and as a pesticide intermediate to produce herbicides such as clethodim, etc., and is used as a propionylating agent in organic synthesis; trimethylacetyl chloride can be used as a pharmaceutical intermediate to produce (hydroxy)ampicillin, ceftriaxone, cefazolin antibiotics, etc.; as a pesticide intermediate, it can produce insecticides such as triazolam and herbicides such as clomazone in synthesis. In actual pesticide and pharmaceutical production, the purity requirement for acyl chloride is usually ≥99%. Therefore, it is very necessary to develop an efficient, fast, environmentally friendly and low-cost method for producing acyl chloride.

[0004] At present, the most commonly used raw materials for preparing acyl chlorides are: SOCl2, phosphorus trichloride, phosphorus pentachloride, triphosgene, etc. Xin Jianfeng, Ma Jihai, etc. of the School of Science of Hebei University of Science and Technology introduced the preparation method and mechanism of acyl chloride in "A Review of Acyl Chloride Preparation Methods" (Hebei Chemical Industry, 2006, 29 (11)). At present, acyl chlorides are mostly produced by phosphorus trichloride method and phosgene method in China. Chinese patent application CN 109942416A proposes a preparation method of aromatic acyl chlorides using phosphorus trichloride as a chlorinating agent and synthesizing the corresponding acyl chlorides from aromatic carboxylic acids. This method is suitable for preparing low-boiling acyl chlorides because phosphorous acid generated in the reaction is not easy to volatilize, thereby facilitating the distillation of acyl chlorides. For the preparation of high-boiling acyl chloride products, its by-products are not easy to separate, the product loss is large, and the yield is low. Zhou Xiaoqian et al. (Study on the synthesis of propionyl chloride by phosgene method, Liaoning Chemical Industry, 2003, 32(1):9-11) introduced a process for synthesizing propionyl chloride using propionic acid and phosgene as raw materials in the presence of a catalyst. This process is semi-continuous production with a product yield of 97% and a product purity of ≥98%. It has the characteristics of high product purity, good appearance, low cost, and less waste. However, phosgene is highly toxic and is a verification chemical specified in the International Convention on the Prohibition of Chemical Weapons. It has strict requirements in terms of labor protection and safety, and the tail gas treatment is difficult. The environmental protection problem is severe, so it is more suitable for manufacturers with phosgene resources.

[0005] Based on the above problems existing in the prior art, it is very necessary to find a relatively safe and efficient method for preparing high-purity acyl chloride products. Summary of the invention

[0006] The invention aims at the deficiencies in the prior art and provides a method for preparing a high-purity acyl chloride product. The acyl chloride can be prepared continuously, thereby improving the production efficiency of the acyl chloride and reducing the production time. The product has high purity and high yield, and unreacted organic acid and catalyst can be reused as raw materials for the next reaction, thereby saving production costs.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a high-purity acyl chloride product, the preparation method comprising:

[0008] S1, an organic acid, thionyl chloride and an amide catalyst are mixed and reacted by multi-stage heating under stirring conditions to obtain a crude acyl chloride;

[0009] The multi-stage temperature rising process is as follows: the first stage reaction temperature is 20-25°C, and the reaction time is 30-40min; the second stage reaction temperature is 35-45°C, and the reaction temperature is 30-40min; the third stage reaction temperature is 50-100°C, and the reaction time is 40-70min;

[0010] The organic acid is selected from any one of the following compounds:

[0011] ;

[0012] R1, R2, and R3 are each independently selected from H, C1-C18 alkyl, C2-C18 alkenyl, substituted C1-C18 alkyl, substituted C2-C18 alkenyl, halogen, nitro, or amino; the substituents in the substituted C1-C18 alkyl and substituted C2-C18 alkenyl are independently selected from halogen, nitro, or amino;

[0013] S2, distilling and purifying the crude acyl chloride to obtain the acyl chloride product.

[0014] Furthermore, the amide catalyst is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and caprolactam.

[0015] Furthermore, the molar ratio of the organic acid to thionyl chloride is (1.0-1.3):1; and the amount of the amide catalyst added is 0.3-0.9% of the mass of thionyl chloride.

[0016] Furthermore, in step S1, when the raw materials are mixed, the order of adding the raw materials is organic acid, thionyl chloride, and amide catalyst.

[0017] Furthermore, in step S1, during the multi-stage heating process, the heating rate between each stage is 2-3°C / min.

[0018] Furthermore, R1, R2, and R3 are each independently selected from H, C1-C15 alkyl, C2-C6 alkenyl, substituted C1-C15 alkyl, substituted C2-C6 alkenyl, halogen, nitro or amino; and the substituents in the substituted C1-C15 alkyl and substituted C2-C6 alkenyl are independently selected from F, Cl, Br, I, nitro or amino.

[0019] Preferably, R1, R2, and R3 are each independently selected from H, C1-C6 alkyl, C2-C3 alkenyl, substituted C1-C6 alkyl, substituted C2-C3 alkenyl, halogen, nitro or amino; and the substituents in the substituted C1-C6 alkyl and substituted C2-C3 alkenyl are independently selected from F, Cl, Br, I, nitro or amino.

[0020] Preferably, the organic acid is any one of propionic acid, acetic acid, butyric acid, isobutyric acid, trimethylacetic acid, 2-methylbutyric acid, heptanoic acid, octanoic acid, decanoic acid, stearic acid, acrylic acid, chloroacetic acid, chlorotrimethylacetic acid, o-chlorobenzoic acid, benzoic acid, o-nitrobenzoic acid, terephthalic acid, and isophthalic acid.

[0021] Furthermore, in step S2, the distillation temperature is 50-150°C.

[0022] Furthermore, in step S2, the crude acyl chloride is distilled and purified to obtain the acyl chloride product, and then the organic acid and amide catalyst are recovered and reused for 2-8 times.

[0023] The beneficial effects of the present invention are:

[0024] The preparation method of the acyl chloride product of the present invention can continuously prepare the acyl chloride product, thereby improving the production efficiency of the acyl chloride product, shortening the production cycle, and the acyl chloride product has high purity (purity>99.0%) and high yield (yield≥96.7%), and the prepared product can meet the purity requirements of the raw materials required for the production of pesticides and medicines; and the unreacted organic acid and catalyst can be reused as raw materials for the next reaction, thereby saving production costs. The preparation method of the present invention uses thionyl chloride as the chlorination raw material, and its by-product is mainly gas, and can be separated from the system in time, which is conducive to the separation of the product. At the same time, thionyl chloride is a relatively safe chlorination reagent, which is very suitable for industrial application.

[0025] In the preparation method of the present invention, the reactants organic acid, thionyl chloride and catalyst are heated step by step from room temperature to high temperature, so as to avoid the problem that the raw material thionyl chloride is too violent to cause the gas generated by the acylation reaction to escape, which is conducive to the full reaction of the organic acid and thionyl chloride, improves the conversion rate, and the reaction process is more controllable, and the occurrence of side reactions is reduced. At the same time, the main component catalyst and a small amount of unreacted organic acid in the high boiling point residual in the distillation stage can still be reused as raw materials for the next reaction, thereby reducing waste generation and reducing production costs.

[0026] In addition, in the preparation method described in the present invention, the order of adding each raw material when the raw materials are mixed is organic acid, thionyl chloride, and amide catalyst. Add organic acid first and then add thionyl chloride. The specific gravity of thionyl chloride is large. The order of adding materials defined in the present invention can avoid stratification of the system, which is more conducive to uniform mixing of the raw materials in the system and improves the reaction efficiency. Moreover, the feeding method defined in the present invention can make all raw materials be added to the reactor at one time compared with the dripping speed control feeding method. When applied industrially, the complexity of feeding is reduced, and there is no need to add a dripping speed control device, which reduces the equipment cost, and the reaction efficiency is high, shortening the production cycle; by cooperating with multi-stage heating conditions, it is beneficial to control the reaction state in the system to obtain high-yield, high-purity acyl chloride products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The following is a simplified flow chart of the preparation process of the acyl chloride products of the present invention;

[0028] Figure 2 The NMR spectrum of the finished product propionyl chloride prepared in Example 1;

[0029] Figure 3 The gas chromatogram of the finished product propionyl chloride prepared in Example 1;

[0030] Figure 4 This is the NMR spectrum of the finished product trimethylacetyl chloride prepared in Example 5. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0033] like Figure 1As shown, a method for preparing a high-purity acyl chloride product, the preparation method is:

[0034] S1, an organic acid, thionyl chloride and an amide catalyst are mixed and reacted by multi-stage heating under stirring conditions to obtain a crude acyl chloride;

[0035] The multi-stage temperature rising process is as follows: the first stage reaction temperature is 20-25°C, and the reaction time is 30-40min; the second stage reaction temperature is 35-45°C, and the reaction temperature is 30-40min; the third stage reaction temperature is 50-100°C, and the reaction time is 40-70min;

[0036] The organic acid is selected from any one of the following compounds:

[0037] ;

[0038] R1, R2, and R3 are each independently selected from H, C1-C18 alkyl, C2-C18 alkenyl, substituted C1-C18 alkyl, substituted C2-C18 alkenyl, halogen, nitro, or amino; the substituents in the substituted C1-C18 alkyl and substituted C2-C18 alkenyl are independently selected from halogen, nitro, or amino;

[0039] S2, distilling and purifying the crude acyl chloride to obtain the acyl chloride product.

[0040] Specifically, the amide catalyst is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and caprolactam.

[0041] Specifically, the molar ratio of the organic acid to thionyl chloride is (1.0-1.3):1; and the amount of the amide catalyst added is 0.3-0.9% of the mass of thionyl chloride.

[0042] Preferably, the molar ratio of the organic acid to thionyl chloride is (1.0-1.2):1.

[0043] More preferably, the molar ratio of the organic acid to thionyl chloride is 1.05:1.

[0044] Specifically, in step S1, when the raw materials are mixed, the order of adding the raw materials is organic acid, thionyl chloride, and amide catalyst.

[0045] Specifically, in step S1, during the multi-stage heating process, the heating rate between each stage is 2-3°C / min.

[0046] More specifically, the alkyl group in the C1-C18 alkyl group and the substituted C1-C18 alkyl group is preferably a C1-C15 alkyl group, more preferably a C1-C6 alkyl group, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl or n-hexyl;

[0047] The alkenyl group in the C2-C18 alkenyl group and the substituted C2-C18 alkenyl group is preferably a C2-C6 alkenyl group, more preferably a C2-C3 alkenyl group, such as vinyl;

[0048] The halogen substituent in R1, R2 and R3 is F, Cl, Br or I, preferably Cl.

[0049] Preferably, the is propionic acid, acetic acid, butyric acid, isobutyric acid, trimethylacetic acid, 2-methylbutyric acid, heptanoic acid, octanoic acid, decanoic acid, stearic acid, acrylic acid, chloroacetic acid or chlorotrimethylacetic acid;

[0050] Said is o-chlorobenzoic acid, benzoic acid or o-nitrobenzoic acid;

[0051] Said It is terephthalic acid or isophthalic acid.

[0052] More specifically, there is no strict restriction on the stirring speed in step S1, and it is only necessary to ensure that the system is mixed evenly. The stirring speed in the embodiment of the present invention is 300-500 rpm.

[0053] Specifically, in step S2, the distillation temperature is 50-150°C. The specific operation is determined according to the prepared acyl chloride product and the boiling point of the catalyst. For example: (1) from organic acid The synthesized crude acyl chloride is purified by atmospheric distillation; or The synthesized crude acyl chloride is purified by a vacuum distillation apparatus, and the vacuum degree is preferably 0.8-1.0 MPa; (2) If the boiling point of the acyl chloride product is lower than the boiling point of the catalyst, the distillation temperature is determined based on the boiling point of the acyl chloride, such as acetyl chloride, propionyl chloride, n-butyryl chloride, isobutyryl chloride, trimethylacetyl chloride, etc.; the acyl chloride fraction can be directly collected; if the boiling point of the acyl chloride product is higher than the boiling point of the catalyst, the vacuum distillation temperature is determined based on the boiling point of the catalyst, the catalyst is distilled off, and then the acyl chloride product, such as terephthalic acid, isophthalic acid, etc., is evaporated.

[0054] Specifically, in step S2, the crude acyl chloride is distilled and purified to obtain the acyl chloride product, and then the organic acid and amide catalyst are recovered and reused for 2-8 times.

[0055] Preferably, the organic acid and amide catalyst are recovered and reused 3-5 times.

[0056] Example 1

[0057] (1) Add 81.49 g (1.1 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 60 °C for 40 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0058] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0059] The NMR spectrum of the propionyl chloride product obtained in this example is as follows Figure 2 As shown in the figure, the NMR measurement conditions are: sample size 10 mg, deuterated chloroform as solvent, and tetramethylsilane as internal standard. The gas chromatogram of propionyl chloride is shown in the figure Figure 3 As shown, the gas chromatography analysis data is shown in Table 1 below.

[0060] Table 1 Gas chromatography analysis data

[0061]

[0062] Example 2

[0063] (1) Add 81.49 g (1.1 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylformamide (DMF) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 35 min at 25 °C, stir for 30 min at 40 °C, and reflux and stir for 40 min at 60 °C. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0064] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0065] Example 3

[0066] (1) Add 85.19 g (1.15 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylformamide (DMF) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 60 °C for 40 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0067] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0068] Example 4

[0069] (1) Add 88.90 g (1.2 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylformamide (DMF) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 60 °C for 40 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0070] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0071] Example 5

[0072] (1) Add 112.34 g (1.1 mol) of trimethylacetic acid, 118.97 g (1 mol) of thionyl chloride and 0.59 g (0.5 wt%) of N-methylpyrrolidone to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 70 °C for 40 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0073] (2) Add the crude trimethylacetyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 105-106° C. to obtain the finished trimethylacetyl chloride.

[0074] The NMR spectrum of the trimethylacetyl chloride product obtained in this example is as follows Figure 4 As shown, the NMR measurement conditions are as follows: the sample amount is 10 mg, deuterated chloroform is used as the solvent, and tetramethylsilane is used as the internal standard.

[0075] Example 6

[0076] (1) Add 122.12g (1mol) benzoic acid, 118.97g (1mol) thionyl chloride and 0.36g (0.3wt%) caprolactam to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, a tail gas absorber and a constant pressure dropping funnel, turn on the stirring, set the speed to 400rpm, stir at 20℃ for 40min, at 35℃ for 40min, and at 100℃ for 50min. The heating rate between each stage is 2-3℃ / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0077] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and perform reduced pressure distillation to obtain the finished product benzoyl chloride.

[0078] Example 7

[0079] (1) Add 215.97 g (1.3 mol) of terephthalic acid, 118.97 g (1 mol) of thionyl chloride and 1.07 g (0.9 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 500 rpm. Stir at 25°C for 40 min, at 45°C for 40 min, and at 50°C for 70 min. The heating rate between each stage is 2-3°C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0080] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, start stirring, set the rotor speed to 400 rpm, turn on heating, and perform vacuum distillation to obtain the catalyst N,N-dimethylacetamide and the finished product terephthaloyl chloride, respectively.

[0081] Comparative Example 1

[0082] Propionyl chloride was prepared by the same method as in Example 1, except that only one-stage heating was used in step (1). The specific preparation process is as follows:

[0083] (1) Add 81.49 g (1.1 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel, turn on the stirring, set the speed to 400 rpm, and stir at 60°C for 100 min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0084] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0085] Comparative Example 2

[0086] The same method as in Example 1 was used to prepare propionyl chloride, except that only two-stage heating was used in step (1). The specific preparation process is as follows:

[0087] (1) Add 81.49 g (1.1 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring, set the speed to 400 rpm, stir at 25 °C for 30 min, and reflux and stir at 60 °C for 70 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0088] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0089] Comparative Example 3

[0090] Propionyl chloride was prepared by the same method as in Example 1, except that, in the multi-stage heating process of step (1), the heating rate between each stage was 5-6°C / min (higher than the heating rate specified in the present invention). The specific preparation process is as follows:

[0091] (1) Add 81.49 g (1.1 mol) of propionic acid, 118.97 g (1 mol) of thionyl chloride and 0.72 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 60 °C for 40 min. The heating rate between each stage is 5-6 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0092] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0093] Comparative Example 4

[0094] The same method as in Example 1 was used to prepare propionyl chloride, except that the feeding method was changed in step (1). The specific preparation process is as follows:

[0095] (1) Add 81.49 g (1.1 mol) of propionic acid and 0.72 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring, set the speed to 400 rpm, raise the system temperature to 60°C, and then slowly drop 118.97 g (1 mol) of thionyl chloride into the system. After the dropwise addition is complete, stir at 60°C for 40 minutes. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0096] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0097] Comparative Example 5

[0098] Propionyl chloride was prepared by the same method as in Example 1, except that the molar ratio of the organic acid to the thionyl chloride was changed. In this comparative example, the molar ratio of propionic acid to thionyl chloride was 1:1.1. The specific preparation process was as follows:

[0099] (1) Add 81.49 g (1.1 mol) of propionic acid, 143.95 g (1.21 mol) of thionyl chloride and 0.86 g (0.6 wt%) of N,N-dimethylacetamide (DMAc) to a three-necked flask equipped with a magnetic stirrer, a thermometer, a condenser, an exhaust gas absorber and a constant pressure dropping funnel. Turn on the stirring and set the speed to 400 rpm. Stir for 30 min at 25 °C, stir for 30 min at 40 °C, and stir under reflux at 60 °C for 40 min. The heating rate between each stage is 2-3 °C / min. The gas generated by the reaction is absorbed by water and sodium hydroxide solution in turn.

[0100] (2) Add the crude propionyl chloride prepared in step (1) into a three-necked flask equipped with a magnetic stirrer, a thermometer, a distillation head, and a condenser, turn on stirring, set the rotor speed to 400 rpm, turn on heating, and collect the fraction with a boiling range of 75-78° C. to obtain the finished propionyl chloride.

[0101] The acyl chloride products prepared in the above examples and comparative examples were subjected to gas chromatography purity test, and the test results are shown in Table 2 below.

[0102] Table 2 Content and yield data of acyl chloride products

[0103]

[0104] It can be seen from the above table data that: Example 1-Example 7 adopts the preparation method of the present invention to prepare acyl chloride products, and the product purity and yield are high. The prepared products can meet the purity requirements of the raw materials needed for the production of pesticides and medicines. Moreover, the operation is simple and suitable for industrial application. In addition, the propionic acid and N, N-dimethylacetamide recovered by distillation in Example 1 are reused. After being reused 8 times, the purity of the acyl chloride products can still reach 99.0%, and the yield is 96.5%. Therefore, the unreacted organic acid and catalyst in the preparation method of the present invention can be reused as raw materials for the next reaction, thereby saving production costs and reducing environmental protection treatment pressure.

[0105] From the comparison of the experimental data of Comparative Example 1 and Example 1, it can be seen that: if only one-stage heating is used in the reaction process, the reaction in the system is relatively violent during the reaction process, and more thionyl chloride will be volatilized, resulting in a worse working environment. At the same time, it is more likely for side reactions to occur, generating impurity propionic anhydride, resulting in a decrease in propionic acid conversion rate and a decrease in product yield.

[0106] From the comparison of the experimental data of Comparative Example 2 and Example 1, it can be seen that if only two-stage heating is used in the reaction process, the yield and purity of the product will also decrease. Therefore, the three-stage heating conditions defined in the present invention are more conducive to directly obtaining high-yield, high-purity acyl chloride products.

[0107] From the comparison of the experimental data of Comparative Example 3 and Example 1, it can be seen that if the heating rate between each stage in step (1) is high, it is not conducive to the stability of the reaction system, resulting in the escape of thionyl chloride, an increase in side reactions, and ultimately a decrease in product purity and yield.

[0108] It can be seen from the comparison of the experimental data of Comparative Example 4 and Example 1 that: if the acyl chloride products are prepared by the method of dripping raw materials, thionyl chloride is added dropwise to the reaction system, and part of thionyl chloride is rapidly volatilized, resulting in a deterioration of the working environment, and thionyl chloride is directly added dropwise to the reaction system with a higher temperature, and the reaction process is also relatively rapid and intense, resulting in a decrease in product purity and yield. In addition, by adopting this dripping method, the dripping process takes more time, resulting in an extension of the production cycle, and if the equipment for dripping needs to be separately configured in industrialization, the equipment cost is high, and the preparation method of the present invention is compared with the method of Comparative Example 4, and the preparation method of the present invention is more conducive to industrial application.

[0109] From the comparison of the experimental data of Comparative Example 5 and Example 1, it can be seen that: during the reaction process, if the thionyl chloride in the raw material is excessive, what remains in the reaction system is thionyl chloride, and the boiling point difference between thionyl chloride and acyl chloride products is relatively small, thereby affecting the distillation purification effect, resulting in a decrease in the yield and purity of the product; in the preparation method of the present invention, the excess of organic acid can improve the product conversion rate, and at the same time, the boiling point difference between acyl chloride products and organic acids is large, which is more conducive to obtaining high-purity acyl chloride products by distillation purification, and the organic acid can be reused, while thionyl chloride is highly volatile and is not conducive to reuse.

[0110] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for preparing a high-purity acyl chloride product, characterized in that: The preparation method is: S1, an organic acid, thionyl chloride and an amide catalyst are mixed and reacted by multi-stage heating under stirring conditions to obtain a crude acyl chloride; the molar ratio of the organic acid to the thionyl chloride is (1.0-1.3): 1; when the raw materials are mixed, the order of adding the raw materials is organic acid, thionyl chloride, and amide catalyst; The multi-stage heating process is as follows: the first stage reaction temperature is 20-25°C, and the reaction time is 30-40min; the second stage reaction temperature is 35-45°C, and the reaction temperature is 30-40min; the third stage reaction temperature is 50-100°C, and the reaction time is 40-70min; in the multi-stage heating process, the heating rate between each stage is 2-3°C / min; The organic acid is selected from any one of the following compounds: ； R1 is selected from C1-C18 alkyl, C2-C18 alkenyl, substituted C1-C18 alkyl or substituted C2-C18 alkenyl; R2 and R3 are each independently selected from H, C1-C18 alkyl, C2-C18 alkenyl, substituted C1-C18 alkyl, substituted C2-C18 alkenyl, halogen, nitro or amino; The substituents in the substituted C1-C18 alkyl and substituted C2-C18 alkenyl are independently selected from halogen, nitro or amino; S2, distilling and purifying the crude acyl chloride to obtain the acyl chloride product; In step S2, the crude acyl chloride is distilled and purified to obtain the acyl chloride product, and then the organic acid and amide catalyst are recovered and reused for 2-8 times.

2. A method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: The amide catalyst is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and caprolactam.

3. A method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: The amount of the amide catalyst added is 0.3-0.9% of the mass of thionyl chloride.

4. A method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: R1 is selected from C1-C15 alkyl, C2-C6 alkenyl, substituted C1-C15 alkyl or substituted C2-C6 alkenyl; R2 and R3 are each independently selected from H, C1-C15 alkyl, C2-C6 alkenyl, substituted C1-C15 alkyl, substituted C2-C6 alkenyl, halogen, nitro or amino; the substituents in the substituted C1-C15 alkyl and substituted C2-C6 alkenyl are independently selected from F, Cl, Br, I, nitro or amino.

5. A method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: R1 is selected from C1-C6 alkyl, C2-C3 alkenyl, substituted C1-C6 alkyl or substituted C2-C3 alkenyl; R2 and R3 are each independently selected from H, C1-C6 alkyl, C2-C3 alkenyl, substituted C1-C6 alkyl, substituted C2-C3 alkenyl, halogen, nitro or amino; the substituents in the substituted C1-C6 alkyl and substituted C2-C3 alkenyl are independently selected from F, Cl, Br, I, nitro or amino.

6. The method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: The organic acid is any one of propionic acid, acetic acid, butyric acid, isobutyric acid, trimethylacetic acid, 2-methylbutyric acid, heptanoic acid, octanoic acid, decanoic acid, stearic acid, acrylic acid, chloroacetic acid, chlorotrimethylacetic acid, o-chlorobenzoic acid, benzoic acid, o-nitrobenzoic acid, terephthalic acid, and isophthalic acid.

7. The method for preparing a high-purity acyl chloride product according to claim 1, characterized in that: In step S2, the distillation temperature is 50-150°C.

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