A process for preparing propionyl chloride from thionyl chloride and removing sulfur

Abstract

The invention relates to a process for preparing propionyl chloride from thionyl chloride and removing sulfur, the process comprising a main reaction step, a first refining step, a second refining step and a third refining step controlled by different temperatures, equipment and processes. The high-purity propionyl chloride product prepared by the process of the invention has very few trace impurities, especially the residual sulfur content in the reaction product, and at the same time ensures the high-efficiency and continuous production of the high-purity propionyl chloride product, and is particularly suitable for the preparation of raw materials in the fine chemical and pharmaceutical industries.

Description

Technical Field

[0001] The invention relates to the preparation of chemical products and the purification and impurity removal process of chemical products. Specifically, the invention relates to a process for preparing propionyl chloride from thionyl chloride and removing sulfur. Background Art

[0002] With the rapid development of industrial upgrading and various industrial sectors, existing material products need to be continuously improved according to industrial upgrading. With the rapid development of fine chemicals and pharmaceutical industries, the demand for refined raw materials and high-purity raw materials is increasing.

[0003] For example, propionyl chloride is a widely used organic synthesis intermediate, which is widely used in fine chemicals and pharmaceutical industries. In existing reports, propionyl chloride synthesis methods include phosphorus trichloride method and phosgene method, among which the more common ones are phosphorus chloride method and phosgene method. Existing studies have been extensively studied for the synthesis of propionyl chloride. For example, the Chinese patent publication No. CN113999110A uses phosphorus trichloride and propionic acid to produce propionyl chloride by a continuous method, but the addition method of the raw materials is an intermittent method, and the propionyl chloride yield is about 95% and the product purity is ≥98%. However, when propionyl chloride is generated by the phosphorus trichloride method, phosphorous acid by-product is produced, causing environmental pollution. In addition, this type of method does not consider the residual raw materials in the reaction product and the fine further impurity removal process.

[0004] Therefore, it is necessary to develop a new and efficient process for the fine chemical manufacture of propionyl chloride. Summary of the invention

[0005] The present invention aims to solve one or more deficiencies in the above-mentioned prior art, and utilizes multiple steps of reaction, impurity removal, and refining steps, and utilizes SOCl2 as one of the reaction raw materials to efficiently and accurately synthesize propionyl chloride and remove impurities remaining in the reaction raw materials, thereby broadening and further refining the propionyl chloride synthesis route.

[0006] The embodiment of the present invention provides a process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent, and the process comprises the following steps:

[0007] The main reaction step comprises: preparing propionic acid and thionyl chloride as raw materials, mixing the raw materials according to a molar ratio of propionic acid to thionyl chloride of (1-1.1):(0.8-0.9), and carrying out a main reaction. In the main reaction, thionyl chloride is added dropwise into a reaction kettle containing propionic acid, and the reaction temperature is controlled to be maintained at 25° C. to 35° C. for 3-8 hours to obtain crude propionyl chloride of a preliminary reaction;

[0008] The first refining step: adding N,N-dimethylformamide (DMF) to the crude propionyl chloride obtained in the above step to remove residual sulfur compounds, for example, typically removing thionyl chloride, adding N,N-dimethylformamide (DMF) according to 2% to 10% of the mass of the crude propionyl chloride to react for 1-3 hours, controlling the reaction temperature to be 30° C. to 50° C., to obtain a first refined material;

[0009] A second refining step: the first refined material in the first refining step is subjected to a second refining step at 90° C. to 110° C. to obtain a second refined material;

[0010] The third refining step: reacting the second refined material in the second refining step at 30° C. to 40° C. for 0.5 to 3 hours to obtain a third refined material;

[0011] Refining and collecting steps: placing the third refined material in an environment of 70° C. to 85° C., controlling the ambient pressure at 0.80 MPa to 0.95 MPa, and collecting the propionyl chloride product obtained by distillation.

[0012] In a further optional scheme, the second refining step is performed by feeding the first refined material in the first refining step into a vacuum jet pump, so that the material is quickly sprayed from the top to the bottom through the inlet of the vacuum jet pump, and at the same time, nitrogen gas at 100°C to 110°C is transported from the top of the vacuum jet pump, thereby performing the second refining step.

[0013] In a further optional scheme, the process of preparing propionyl chloride using thionyl chloride as an acyl chloride reagent is completed by a propionyl chloride preparation and impurity removal device, and the propionyl chloride preparation and impurity removal device comprises:

[0014] Propionic acid intermediate tank (101), reaction kettle (102), high-level tank (103), material transfer pump (104), propionyl chloride first refining tower (105), tail gas collector (106), heat exchanger (107), vacuum jet pump (108), precipitation liquid tank (109), propionyl chloride collection tower (110), product collector (111); and

[0015] The inlet of the reactor (102) is connected to the propionic acid intermediate tank (101) and the high-level tank (103) respectively; the outlet of the reactor (102) is connected to the first propionyl chloride refining tower (105) through a material transfer pump (104); the bottom outlet of the first propionyl chloride refining tower (105) is connected to the material inlet of a vacuum jet pump (108); the top of the vacuum jet pump (108) is connected to the heat exchanger (107); the bottom of the vacuum jet pump (108) is connected to the precipitate tank (109); the outlet of the precipitate tank (109) is connected to a propionyl chloride collecting tower (110); the top outlet of the propionyl chloride collecting tower (110) is connected to a product collector (111) for collecting products.

[0016] In a further optional solution, the high-level tank (103) is disposed above the reaction kettle (102) and is used to drop thionyl chloride into the reaction kettle (102); and

[0017] The tail gas collector (106) is connected to the top of the first propionyl chloride refining tower (105).

[0018] In a preferred embodiment, the main reaction, the first refining step, the second refining step and the third refining step are respectively implemented by the following specific processes:

[0019] The main reaction step is: after measuring the propionic acid from the propionic acid intermediate tank (101) with a flow meter, the propionic acid is pumped into a stirred reactor (102), the reactor temperature is maintained at 20-25° C., and the required thionyl chloride is measured with an overhead tank (103), and dropwise addition is started, the dropwise addition temperature is maintained at about 20-25° C., the dropwise addition time is 6-8 hours, and after the dropwise addition is completed, the temperature is kept at 30° C. for 4-6 hours, wherein a small amount of sulfur dioxide and hydrogen chloride as byproducts are drawn out from the top of the reactor (101) for collection and / or post-treatment, and wherein the molar ratio of propionic acid to thionyl chloride is controlled to be 1:0.9, to obtain crude propionyl chloride;

[0020] The first refining step: the preliminary synthesis material including the crude propionyl chloride is pumped into the first propionyl chloride refining tower (105) through a transfer pump (104), a desulfurization component N,N-dimethylformamide (DMF) is added according to 5% of the calculated mass of the crude propionyl chloride to react for 2 hours, the temperature is controlled between 45-50° C., and the by-products flowing out from the top of the tower are sent to the tail gas collector (106), and the first refined material is obtained at the bottom of the first propionyl chloride refining tower (105);

[0021] The second refining step is: the first refined material obtained at the bottom of the first propionyl chloride refining tower (105) is sent to the vacuum jet pump (108), so that the material is sprayed from the upper part to the lower part through the inlet of the vacuum jet pump, and at the same time, nitrogen gas at 100° C. to 105° C. is transported from the top of the vacuum jet pump through the heat exchanger (107), so that the co-produced material further flows downward into the precipitation liquid tank (109) to obtain the second refined material;

[0022] The third refining step: reacting the second refined material flowing into the precipitation liquid tank (109) at 30-35°C for 1 hour to obtain a third refined material;

[0023] Refining and collecting step: the third refined material is sent to the propionyl chloride collecting tower (110), the temperature of the collecting tower is controlled at 75 to 80° C., and the pressure is controlled at 0.90 MPa to 0.95 MPa to collect the propionyl chloride product to the product collector (111); the by-products such as methylformamide hydrochloride remaining after the gas stripping process flow out from the bottom of the propionyl chloride collecting tower (110).

[0024] According to the technical solution of the present invention, the process also satisfies one or more of the following conditions:

[0025] In the final propionyl chloride product obtained by the process, the residual thionyl chloride content is less than 30 ppm, preferably, the residual thionyl chloride content is between 15 and 20 ppm;

[0026] The APHA color number of the final propionyl chloride product obtained by the process is less than 20; preferably between 15 and 20;

[0027] In the device for preparing and removing impurities from propionyl chloride, the vacuum jet pump (108) has a nozzle structure (203) that is narrow in the middle and relatively wider on both sides; the vacuum jet pump (108) is configured to allow the first refined material to be discharged at a speed of 0.3 to 0.8 m 3 / h rate enters into the interior of the vacuum jet pump through the inlet of the vacuum jet pump.

[0028] As can be seen from the above-described scheme and the implementation scheme to be described, the present application utilizes multiple steps of reaction, impurity removal, and refining steps, and utilizes SOCl2 as one of the reaction raw materials to efficiently and accurately synthesize propionyl chloride and remove impurities remaining in the reaction raw materials. The propionyl chloride synthesis route is broadened and further refined.

[0029] In the following, the technical solutions and advantages of the present invention will be explained and described in more detail in conjunction with specific implementation methods. It should be understood that the contents presented in the specification and specific implementation methods are only for the purpose of more clearly illustrating the technical solutions and advantages of the present invention, and do not limit the protection scope of the present invention. Those skilled in the art can obtain the changed technical solutions based on the disclosure of the specification for various reasonable transformations. As long as they do not deviate from the spirit of the present invention, the various changed technical solutions should be understood to be included in the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the technical solution of the present disclosure and constitute a part of the specification. Together with the specific embodiments of the present application, they are used to explain the technical solution of the present disclosure and do not constitute a limitation on the technical solution of the present disclosure.

[0031] Figure 1 Schematic diagram of the equipment for preparing propionyl chloride from thionyl chloride according to Example 1 of the present invention;

[0032] Figure 2 This is a gas phase spectrum of the test of high-purity propionyl chloride prepared according to the process of Example 1;

[0033] Figure 3 The figure is a schematic longitudinal cross-sectional view of a typical pump body of a jet vacuum pump which can be used to implement the process of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described in more detail hereinafter to facilitate understanding of the invention.

[0035] Before describing the specific implementation scheme, it should be noted that those skilled in the art can select appropriate raw materials according to the enlightenment and teaching of the present disclosure, and use relevant testing equipment to perform relevant tests and obtain corresponding results. For raw materials without specific manufacturers or pathways, those skilled in the art can select raw materials that meet corresponding requirements as reaction starting materials according to the disclosure and requirements of this specification. The reaction raw materials of the process part compounds are derived from the initial products synthesized in the preamble step of the present invention, which can also be understood according to the present disclosure.

[0036] First, the main raw materials used in the present invention and the corresponding acquisition channels or raw material origins are listed in Table 1. It should be noted that the raw materials not described in the present invention are raw material varieties that can be obtained by those skilled in the art based on common technical knowledge and existing market products.

[0037] Table 1: Description of main raw materials / equipment used in the present invention

[0038]

[0039] The raw materials of the present invention can be further physically / chemically purified according to actual application needs. The raw material purification and purification can be carried out according to existing technologies and processes to ensure the purity of the final product.

[0040] The various devices and components used in the embodiments of the present invention can be obtained from existing industrial products or commercial purchases. For example, the jet vacuum pump can adopt the product of the 5PS0.04-(10+4) / 0.5 series produced by Hangzhou Hechen Energy Technology Co., Ltd. However, the present embodiment is not limited thereto, and other necessary vacuum pump equipment can also be used. For the equipment components and applications including the jet vacuum pump, necessary explanations will also be made in this specification.

[0041] It should be noted that percentages indicated in the technical solution, embodiments of the specification and the content of the invention of the present invention will generally be specifically described. If no special description is given for the concentration or percentage, it will refer to the molar ratio (mol%) or mass percentage (wt%), or units related to mass and substance.

[0042] In fact, the inventors do not wish to be constrained by any chemical theory to limit the process of the present invention. However, in a sense, the inventors are willing to try to explain some principles of the technical solution of the present invention. Those skilled in the art are fully capable of understanding and implementing the technical solution of the present invention based on the contents of this disclosure.

[0043] First, in the main preparation process of the present invention, propionic acid is reacted with thionyl chloride to generate propionyl chloride. The main reaction can be referred to the chemical formula expressed by the following formula 1:

[0044] CH3CH2COOH+SOCl2=CH3CH2COCl+SO2+HCl——Formula (1)

[0045] Compared with the traditional technical route of preparing propionyl chloride from phosphorus trichloride and propionic acid, this technical route reduces environmental pollution and significantly reduces the cost of industrial production, which will also be described in more detail below.

[0046] However, with the attempt of the preparation process, the inventors found that during the main reaction, regardless of whether propionic acid is in excess, a small amount of SOCl2 will remain in the product system after the reaction. One of the technical difficulties is that SOCl2 and CH3CH2COCl have relatively similar boiling points and separation points, which makes it difficult to further scale up and effectively separate propionyl chloride with high purity after the main reaction.

[0047] To this end, one can try adding N,N-dimethylformamide (DMF, ). When DMF comes into contact with residual or significant amounts of SOCl2, a hydrochlorination reaction will occur, which can be described by the following formula 2:

[0048]

[0049] The main product obtained by the reaction of formula (2) can be mainly called "formamide hydrochloride (formamide hydrochloride, Vilsmeier)", which has a significantly higher boiling point than SOCl2, so in the distillation process, it can be left at the bottom of the distillation container, while the relatively higher purity propionyl chloride is collected at the top.

[0050] However, the reaction can significantly improve the content of propionyl chloride and reduce the content of S impurities (mainly SOCl2), but there are still some shortcomings. One reason is that there are literature reports and practice showing that the thermal stability of formamide hydrochloride is not good. When the reaction temperature is greater than 90°C or higher, a decomposition reaction may occur; and the above formula (2) tends to be conducive to advancing to the right side of the reaction formula at high temperatures. Therefore, the inventors have found through research that in a more preferred scheme, it is advantageous to find that the above reaction can be fully reacted at a higher temperature (greater than 90°C) in a shorter time to remove impurities, and avoid the problem of long-term decomposition of unstable products, which will also be described in detail in the following embodiments.

[0051] In a typical process of the present invention, a propionyl chloride preparation system (equipment) is used to perform the process. In a non-limiting manner, the device for performing the process will be constructed as follows: Figure 1 The device 100 for performing the method for preparing propionyl chloride and removing impurities comprises a propionic acid intermediate tank 101, a reactor 102, a high-level tank 103, a transfer pump 104, a first propionyl chloride refining tower 105, a tail gas collector 106, a heat exchanger 107, a vacuum jet pump 108, a precipitation liquid tank 109, a propionyl chloride collecting tower 110, and a product collector 111. In a typical device connection relationship, the inlet of the reactor 102 is respectively connected to the propionic acid intermediate tank 101 and the high-level tank 103 for inputting reaction raw materials. The outlet of the reactor 102 is connected to the first propionyl chloride refining tower 105 through the transfer pump 104, the bottom outlet of the first propionyl chloride refining tower 105 is connected to the material inlet of the vacuum jet pump 108, and the top of the vacuum jet pump 108 is connected to a heat exchanger 107 for heating and inputting hot inert gas (such as nitrogen); the bottom of the vacuum jet pump 108 is connected to a precipitation liquid tank 109, and the outlet of the precipitation liquid tank 109 is connected to a propionyl chloride collection tower 110 for further collecting highly purified propionyl chloride; the top outlet of the propionyl chloride collection tower 110 is connected to a product collector 111 for collecting products. Those skilled in the art can reasonably implement the device and method according to the contents disclosed in this specification.

[0052] Example 1

[0053] Hereinafter, the specific process and technology of preparing propionyl chloride according to the present invention will be described in detail.

[0054] refer to Figure 1 , after being measured by a flow meter from the propionic acid intermediate tank 101, the propionic acid is pumped into the stirred (enamel) reactor 102, the reactor temperature is maintained at 20-25°C, and the required thionyl chloride (SOCl2) is measured by a high-level tank 103, and the dripping begins, the dripping temperature is maintained at about 20-25°C, the dripping time is 6 hours, and after the dripping is completed, the temperature is kept at 30°C for 4 hours (a small amount of sulfur dioxide and hydrogen chloride produced as by-products can be drawn out from the top of the reactor 101 for collection and / or post-treatment, Figure 1 ), wherein the molar ratio of propionic acid to thionyl chloride is controlled to be 1:0.9, and under the control of the above-mentioned medium and low temperature, the main reaction of thionyl chloride and propionic acid is fully carried out; after the reaction is completed, the preliminary synthesis material is pumped into the first propionyl chloride refining tower 105 through the transfer pump 104, and the desulfurization component N,N-dimethylformamide (DMF) is added according to 5% of the calculated mass of crude propionyl chloride to react for 2 hours, and the temperature is controlled between 45-50°C; in the medium temperature range, a small amount of thionyl chloride remaining in the reactant reacts with DMF to generate formamide hydrochloride salt, which has a relatively high decomposition temperature and melting point / boiling point. At this time, a small amount of SO2 or HCl may be generated at the top of the tower, which is sent to the tail gas collector 106 for corresponding treatment through the top of the tower, which will not be repeated in this embodiment. After that, the reacted material in the first propionyl chloride refining tower 105 is sent to the vacuum jet pump 108, so that the material is quickly sprayed from the upper part to the lower part through the inlet of the vacuum jet pump. At the same time, nitrogen at 100° C. to 105° C. is transported from the top of the vacuum jet pump through the heat exchanger 107, and then the co-produced material further flows downward into the precipitation liquid tank 109, and the temperature is controlled at 30-35° C. to react for another hour; then the material is sent to the propionyl chloride collection tower 110, and the collection tower temperature is controlled at 75 to 80° C., and the pressure is controlled at 0.90 MPa to 0.95 MPa (slightly negative pressure environment) to collect high-purity propionyl chloride products to the product collector 111. The by-products such as methylformamide hydrochloride remaining after the gas stripping process flow out from the bottom of the propionyl chloride collection tower 110.

[0055] The high-purity propionyl chloride prepared by the process of the present invention was tested by gas chromatography, and the results were as follows: Figure 2 And as shown in Table 2.

[0056] Table 2: Gas phase spectrum test results of high-purity propionyl chloride of the present invention

[0057] Peak Retention time Peak height Peak area content 1 4.852 49596.726 352350.875 99.9923％ 2 5.431 281.314 27.287 0.0077％

[0058] From the graph test, we can see that Figure 2The main peak on the left represents the material gas chromatography peak of propionyl chloride, and the peak on the right corresponds to the sulfur compound impurities, especially the SOCl2 compound contained therein. The propionyl chloride synthesis and impurity removal process provided by the embodiment of the present invention can reach more than 99.99% (mass ratio), wherein the residual amount of SOCl2 is less than 20ppm, and in Example 1, SOCl2 can reach a trace level of 15-20ppm.

[0059] The inventors also tested the APHA color number of the crude propionyl chloride obtained in the reactor in Example 1 and the propionyl chloride after further impurity removal and purification according to the standard DIN EN 1557. The lower the color number of the propionyl chloride after refining and purification, the better the purification effect. The test showed that the APHA color number of the crude propionyl chloride was 105, while the APHA color number after purification and impurity removal in Example 1 was only 18, which was better than the 50% color number reduction or 75% color number reduction mentioned in the relevant standards.

[0060] The propionyl chloride product prepared by the embodiment of the present invention is particularly suitable for the process of intermediates or raw materials in the fields of fine chemicals and pharmaceuticals, and is suitable for continuous and uninterrupted production.

[0061] Comparative experiments and tests

[0062] In the following, the preparation process and route of propionyl chloride which are different from the experimental conditions or applied equipment of the embodiment of the present invention will be described.

[0063] Comparative Example 1

[0064] In this comparative experiment, a process similar to that of Example 1 was performed. The difference is that in Comparative Example 1, after the main reaction of the reaction raw materials was completed, the preliminary synthesis material was pumped into the first propionyl chloride refining tower 105 through the transfer pump 104, and the desulfurization component N,N-dimethylformamide (DMF) was added according to 5% of the calculated mass of the crude propionyl chloride to react for 2 hours, and the temperature was controlled between 45-50°C; thereafter, the product did not undergo the high-temperature jet refining process of the vacuum jet pump 108 in Example 1, but the product was directly flowed into the precipitation liquid tank 109, and the remaining process of Example 1 was performed, and finally the refined product was collected.

[0065] Comparative Example 2

[0066] In this comparative experiment, a process similar to that of Example 1 was performed. The difference is that in Comparative Example 1, after the main reaction of the reaction raw materials was completed, the preliminary synthesis material was pumped into the first propionyl chloride refining tower 105 through the transfer pump 104, and the desulfurization component N,N-dimethylformamide (DMF) was added according to 5% of the calculated mass of crude propionyl chloride to react for 2 hours, and the temperature was controlled between 45-50°C; thereafter, the product was sent to another high-temperature distillation tower (not shown in the attached drawings), the temperature was controlled, and distilled at 100-105°C for 1-2 hours, and the refined product propionyl chloride was collected.

[0067] Comparative Example 3

[0068] This experiment carried out an experimental process similar to that of Comparative Example 1, except that, in the batching stage of the initial reaction, the molar ratio of propionic acid to thionyl chloride was controlled to be 2:0.9, and a greater theoretical excess of propionic acid was controlled. The rest of the process flow was the same as that of the aforementioned Comparative Example 1, and the refined product propionyl chloride was finally collected.

[0069] Comparative Example 4

[0070] Comparative Example 4 performs a process similar to that of Comparative Example 1. Unlike Comparative Example 1, in the scheme of Comparative Example 4, the preliminary synthesis material is pumped into the first propionyl chloride refining tower 105 through the material transfer pump 104, and the desulfurization component N,N-dimethylformamide (DMF) is added according to 10% of the calculated mass of crude propionyl chloride to react for 2 hours, and then the same process as Comparative Example 1 is performed.

[0071] The propionyl chloride product synthesized in the comparative example was subjected to the same performance and component tests as in the example. The results are shown in the following table:

[0072] Table 3: Comparison of propionyl chloride properties prepared in Examples and Comparative Examples

[0073] Experimental examples / characteristics Product purity (mass ratio) <![CDATA[SOCl2 content]]> APHA color number Example 1 >99.99％ 15-20ppm 18 Comparative Example 1 99.50％ 150-180ppm 35 Comparative Example 2 98.89％ More than 300ppm 52 Comparative Example 3 99.55％ 150-180ppm 37 Comparative Example 4 99.60％ 150-180ppm 38

[0074] As can be seen from the comparative experiment, when the crude propionyl chloride prepared in the experiment carries out traditional medium temperature and low temperature purification desulfurization process (such as comparative example 1), the purification preparation of crude propionyl chloride can be carried out to a certain extent, but only the DMF refining process of medium temperature (such as 40-50 ℃) is not enough to remove foreign components, particularly SOCl2 component, in the parallel repeated test of the inventor, it exists with a content greater than 100ppm all the time, and the product still does not meet the demand of some high-end medicines and fine chemical intermediates for synthesis of raw materials. And the inventor further finds that when performing a long high temperature distillation process in the impurity removal step (such as comparative example 2), then the refining effect declines instead, and the intermediate formamide hydrochloride in the formula 2 discussed with the foregoing content decomposes at a long high temperature, so that part SOCl2 component is reversely generated, thus relevant with refining propionyl chloride being collected together again. Therefore, for the high temperature refining process implemented by the present invention, it is preferred to select a decontamination stage in which DMF and the residual S compound component are in high temperature and short time contact, so that the relatively high boiling point but easily thermally decomposed formamide hydrochloride can remain in its original state, and the short-time high temperature reaction stage promotes Formula 2 to move in the positive direction. The inventors also found that even if the proportion of raw material propionic acid is increased in large quantities (such as comparative example 3), so that the raw material propionic acid is fully excessive compared to the sulfur chloride compound in the main reaction stage, it is also impossible to ensure that the subsequent SOCl2 content exists in a very low form. Of course, a large proportion of raw material propionic acid and the DMF refining stage shown in the comparative example can meet the requirements of partial chloropropionyl synthesis, preparation and application. In addition, the inventors found that the decontamination stage does not require the addition of a high proportion of DMF, which, compared with using DMF to enter the main reaction stage as a catalytic and partial reaction starting compound, reduces the raw material usage ratio to a greater extent and optimizes the target and effect of later S removal in a more targeted manner. In a typical process of the present invention, the desulfurization component N, N-dimethylformamide (DMF) is added according to 2-5% of the calculated crude propionyl chloride mass.

[0075] In addition, it can be seen from the above description that the embodiment of the present invention adds a short-time relatively high-temperature impurity removal process on the basis of effective improvement, and this process can be achieved by, for example, the vacuum jet pump of the present invention. It should be noted that the vacuum jet pump used in this process can be purchased from an existing vacuum jet device in industrial production, which can use the vacuum condition in the pump to quickly suck in the material and make the material flow in a directional manner. Non-limitingly, the typical vacuum jet pump structure can be as follows Figure 3 It should be noted that those skilled in the art can obtain and implement the corresponding vacuum injection device and process through the additional description of this specification and relevant technical knowledge. Figure 3, shows a schematic longitudinal section diagram of a typical vacuum jet pump. Among them, the main body of the vacuum jet pump mainly includes an injection nitrogen inlet 201, which provides an inlet for heated nitrogen; and a suction material inlet 202, which provides an entry for the material to be sucked. When liquid phase material is selected to enter, in order to ensure the normal operation of the pump body and the full mixing of the material, it is preferred to limit the entry rate of the sucked material through a metering device. In a typical implementation scheme of the present invention, the feed rate of the mixed material at the suction material inlet 202 can be controlled to be 1m 3 / h or less, for example, more preferably controlled at 0.3 to 0.8m 3 / h, so that the liquid phase material is fully dispersed and mixed. A nozzle structure 203 with a narrow middle and relatively wider sides is arranged below the spray nitrogen inlet 201. This structure helps the nitrogen entering the vacuum environment to be further squeezed and accelerated, and sprayed downward at a faster speed. Subsequently, the incoming material and the spray nitrogen are mixed in the nozzle cavity 204, so that the required mixing and reaction are enhanced. In the middle and lower parts of the pump body, a temperature-controlled nitrogen inlet 205 and a temperature-controlled nitrogen outlet 206 are arranged to adjust the reaction temperature in the pump body. When applied to the embodiment of the present invention, the temperature control can be maintained between 100-105°C. In addition, a pressure expansion structure 207 is also arranged in the middle and lower part of the pump body to further compress the material and increase its flow rate; typically, the width of the expansion structure is 30% to 50% smaller than the width of other positions of the pump body channel. Finally, a material outlet 208 is arranged below the pump body, and the material is discharged to the next process downstream through this.

[0076] In addition, it is noted that the inventors have found that the reaction and continuous manufacturing system of the present invention also effectively improves the cost and expense of the synthesis route compared to the traditional phosphorus-chlorine system. In a non-limiting manner, in a typical industrial production system, the relevant cost accounting can be simply described by the following table.

[0077] Table 4:

[0078]

[0079] In addition, even considering the DMF purification process of the present invention, since the amount of DMF used in the present invention is very small and the price of the commercial product is not high, in the industrial flow production system, the cost generated is very small, the entire process system also belongs to continuous and uninterrupted production, and the production efficiency is also correspondingly guaranteed and improved.

[0080] According to the implementation scheme and technical contents recorded in the specification of the present invention, the present invention can at least provide the following technical solutions: Although the present disclosure includes specific embodiments, it is obvious to those skilled in the art that various formal and detailed replacements or changes can be made to these embodiments without departing from the gist and scope of the invention of the present claims and their equivalent technical solutions. The embodiments described herein should be considered to be illustrative only and not for the purpose of limitation. The description of the features and aspects in each embodiment is considered to be applicable to similar features and aspects in other embodiments. Therefore, the scope of the present disclosure should not be limited by the specific description, but by the technical solutions of the claims, and all changes within the scope of the claims and their equivalents are interpreted as being included in the technical solutions of the present disclosure.

Claims

1. A process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent, characterized in that: The process comprises the following steps: The main reaction step comprises: preparing propionic acid and thionyl chloride as raw materials, mixing the raw materials according to a molar ratio of propionic acid to thionyl chloride of (1-1.1):(0.8-0.9), and carrying out a main reaction. In the main reaction, thionyl chloride is added dropwise into a reaction kettle containing propionic acid, and the reaction temperature is controlled to be maintained at 25° C. to 35° C. for 3-8 hours to obtain crude propionyl chloride of a preliminary reaction; The first refining step: adding N,N-dimethylformamide (DMF) to the crude propionyl chloride obtained in the above step to remove residual sulfur compounds, for example, typically removing thionyl chloride, adding N,N-dimethylformamide (DMF) according to 2% to 10% of the mass of the crude propionyl chloride to react for 1-3 hours, controlling the reaction temperature to be 30° C. to 50° C., to obtain a first refined material; A second refining step: the first refined material in the first refining step is subjected to a second refining step at 90° C. to 110° C. to obtain a second refined material; The third refining step: reacting the second refined material in the second refining step at 30° C. to 40° C. for 0.5 to 3 hours to obtain a third refined material; Refining and collecting steps: placing the third refined material in an environment of 70° C. to 85° C., controlling the ambient pressure at 0.80 MPa to 0.95 MPa, and collecting the propionyl chloride product obtained by distillation.

2. The process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent according to claim 1, characterized in that: The second refining step is performed by delivering the first refined material in the first refining step into a vacuum jet pump, so that the material is quickly sprayed from the top to the bottom through the inlet of the vacuum jet pump, and at the same time, nitrogen gas at 100°C to 110°C is delivered from the top of the vacuum jet pump, thereby performing the second refining step.

3. The process for preparing propionyl chloride by thionyl chloride as an acyl chloride reagent according to claim 1 or 2, characterized in that: The process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent is completed by a propionyl chloride preparation and impurity removal device, and the propionyl chloride preparation and impurity removal device comprises: Propionic acid intermediate tank (101), reaction kettle (102), high-level tank (103), material transfer pump (104), propionyl chloride first refining tower (105), tail gas collector (106), heat exchanger (107), vacuum jet pump (108), precipitation liquid tank (109), propionyl chloride collection tower (110), product collector (111); and The inlet of the reactor (102) is connected to the propionic acid intermediate tank (101) and the high-level tank (103) respectively; the outlet of the reactor (102) is connected to the first propionyl chloride refining tower (105) through a material transfer pump (104); the bottom outlet of the first propionyl chloride refining tower (105) is connected to the material inlet of a vacuum jet pump (108); the top of the vacuum jet pump (108) is connected to the heat exchanger (107); the bottom of the vacuum jet pump (108) is connected to the precipitate tank (109); the outlet of the precipitate tank (109) is connected to a propionyl chloride collecting tower (110); the top outlet of the propionyl chloride collecting tower (110) is connected to a product collector (111) for collecting products.

4. The process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent according to claim 3, wherein: The high-level tank (103) is arranged above the reaction kettle (102) and is used for dripping thionyl chloride into the reaction kettle (102); and The tail gas collector (106) is connected to the top of the first propionyl chloride refining tower (105).

5. according to the process for preparing propionyl chloride by thionyl chloride as acyl chloride reagent described in claims 1 to 4, it is characterized in that, The main reaction, the first refining step, the second refining step and the third refining step are respectively achieved by the following specific processes: The main reaction step is: after measuring the propionic acid from the propionic acid intermediate tank (101) with a flow meter, the propionic acid is pumped into a stirred reactor (102), the reactor temperature is maintained at 20-25° C., and the required thionyl chloride is measured with an overhead tank (103), and dropwise addition is started, the dropwise addition temperature is maintained at about 20-25° C., the dropwise addition time is 6-8 hours, and after the dropwise addition is completed, the temperature is kept at 30° C. for 4-6 hours, wherein a small amount of sulfur dioxide and hydrogen chloride as byproducts are drawn out from the top of the reactor (101) for collection and / or post-treatment, and wherein the molar ratio of propionic acid to thionyl chloride is controlled to be 1:0.9, to obtain crude propionyl chloride; The first refining step: the preliminary synthesis material including the crude propionyl chloride is pumped into the first propionyl chloride refining tower (105) through a transfer pump (104), a desulfurization component N,N-dimethylformamide (DMF) is added according to 5% of the calculated mass of the crude propionyl chloride to react for 2 hours, the temperature is controlled between 45-50° C., and the by-products flowing out from the top of the tower are sent to the tail gas collector (106), and the first refined material is obtained at the bottom of the first propionyl chloride refining tower (105); The second refining step is: the first refined material obtained at the bottom of the first propionyl chloride refining tower (105) is sent to the vacuum jet pump (108), so that the material is sprayed from the upper part to the lower part through the inlet of the vacuum jet pump, and at the same time, nitrogen gas at 100° C. to 105° C. is transported from the top of the vacuum jet pump through the heat exchanger (107), so that the co-produced material further flows downward into the precipitation liquid tank (109) to obtain the second refined material; The third refining step: reacting the second refined material flowing into the precipitation liquid tank (109) at 30-35°C for 1 hour to obtain a third refined material; Refining and collecting step: the third refined material is sent to the propionyl chloride collecting tower (110), the temperature of the collecting tower is controlled at 75 to 80° C., and the pressure is controlled at 0.90 MPa to 0.95 MPa to collect the propionyl chloride product to the product collector (111); the by-products such as methylformamide hydrochloride remaining after the gas stripping process flow out from the bottom of the propionyl chloride collecting tower (110).

6. The process for preparing propionyl chloride by using thionyl chloride as an acyl chloride reagent according to claims 1 to 5, characterized in that: The process also satisfies one or more of the following conditions: In the final propionyl chloride product obtained by the process, the residual thionyl chloride content is less than 30 ppm, preferably, the residual thionyl chloride content is between 15 and 20 ppm; The APHA color number of the final propionyl chloride product obtained by the process is less than 20; preferably between 15 and 20; In the device for preparing and removing impurities from propionyl chloride, the vacuum jet pump (108) has a nozzle structure (203) that is narrow in the middle and relatively wider on both sides; the vacuum jet pump (108) is configured to allow the first refined material to be discharged at a speed of 0.3 to 0.8 m 3 / h rate enters into the interior of the vacuum jet pump through the inlet of the vacuum jet pump.

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