Method and equipment for preparing DCB through continuous loop transposition reaction

Abstract

The invention relates to the technical field of organic chemical synthesis, and discloses a method and equipment for preparing DCB through a continuous loop transposition reaction. The method comprises the following steps: step 1, adding a product material which contains DCB and hydrochloric acid and is used for preparing DCB through a pre-transposition reaction into a reaction kettle, and enabling the product material which contains DCB and is used for preparing DCB through the pre-transposition reaction to circulate in a circulation loop comprising the reaction kettle and a cooler; and step 2, adding a hydrochloric acid aqueous solution and a toluene solution of 2, 2 '-dichlorohydroazobenzene into the reaction kettle to carry out a transposition reaction, meanwhile, keeping materials in the reaction kettle to circulate, and leading out a transposition reaction product from an outlet of the cooler. According to the present invention, the transposition reaction can be completed only by using one reaction kettle to continuously prepare the DCB, the selectivity of the DCB in the obtained product is high, the by-product is less, and the DCB content is more than or equal to 90%.

Description

Technical Field

[0001] The present invention relates to the technical field of organic chemical synthesis, and in particular to a method and equipment for preparing DCB by continuous cyclic transposition reaction. Background Art

[0002] DCB is the abbreviation of 3,3'-dichlorobenzidine, which is an important intermediate in the production of dichlorobenzidine-based yellow organic pigments. The output of a series of yellow organic pigments made with it as raw material accounts for about 25% of the total organic pigments. These organic pigments are widely used in coloring inks, paints, rubber, plastics, etc. and in the production of coating printing slurries and coating dyeing slurries.

[0003] In the prior art, the DCB production process uses o-nitrochlorobenzene as a raw material, obtains a toluene solution of a DCB reduction product (2,2'-dichlorohydroazobenzene) through a hydrogenation reaction, and then undergoes a transposition reaction with hydrochloric acid to obtain a DCB mixed slurry solution. At present, intermittent reactor equipment and processes are used for transposition reactions at home and abroad, and continuous reactor reaction equipment and processes are rarely used. Although the invention patent with announcement number CN114249657B involves a method for continuous preparation of DCB, it still uses multiple reactors and dispersion pumps for intermittent reaction and transfer of materials. Since the material is relatively viscous during the reaction process and the reaction time is long, the reaction time for each batch is basically 30-40 hours. Not only does it require a large number of transposition reactors, but the equipment power consumption is also large, and the by-products are high. In order to save power, reduce the number of reactors and improve product yields, it is urgent to study the DCB continuous transposition reaction process and equipment. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to achieve efficient preparation of DCB by using a reactor.

[0005] In view of the above problems, the present invention provides a method for preparing DCB by continuous cyclic translocation reaction, comprising the following steps: Step 1, adding a product material containing DCB and hydrochloric acid prepared by a pre-metathesis reaction into a reactor, and circulating the product material containing DCB and hydrochloric acid prepared by a pre-metathesis reaction in a circulation loop including a reactor and a cooler; Step 2: Add hydrochloric acid aqueous solution and toluene solution of 2,2'-dichloroazobenzene into the reactor to carry out a metathesis reaction, while keeping the materials in the reactor circulating, and drawing out the metathesis reaction product at the outlet of the cooler.

[0006] In the above scheme, the product material of the pre-transposition reaction containing DCB and hydrochloric acid added in step 1 to prepare DCB can be the product material obtained from the previous transposition reaction, as long as it contains hydrochloric acid and DCB, or it can be the transposition product material obtained in this production. The circulation of step 1 is equivalent to a pre-reaction, which serves as a fuse to guide the subsequent transposition reaction. Under the strict temperature control of the cooler, the subsequent real transposition reaction continues in the circulation, so that the transposition reaction product DCB is continuously obtained. The chemical reaction formula involved is expressed as follows:

[0007] .

[0008] In a possible implementation, in both step 1 and step 2, the temperature in the reaction kettle is controlled to be 20-30° C. At this temperature, the efficiency of the transposition reaction is better.

[0009] In one possible embodiment, the volume of the product material of the pre-metathesis reaction containing DCB and hydrochloric acid added in step 1 to prepare DCB accounts for 50-80% of the volume of the reactor; And / or, during the circulation process of step 1, the volume of the material in the reactor is controlled to account for 50-70% of the volume of the reactor.

[0010] The volume ratio of the material added for the first time is very important, which is related to whether the guiding effect of the pre-reaction can be successful.

[0011] In a possible embodiment, the mass concentration of hydrochloric acid in the product material of the pre-transposition reaction containing DCB and hydrochloric acid added in step 1 to prepare DCB is 15-17%.

[0012] In the above scheme, the concentration of hydrochloric acid in the product material of the pre-added DCB and hydrochloric acid pre-metathesis reaction to prepare DCB is a key factor in whether it can play a guiding role in the subsequent metathesis reaction.

[0013] In a possible implementation manner, during the circulation process in step 2, the volume of the material in the reactor is controlled to account for 50-70% of the volume of the reactor.

[0014] In the above scheme, ensuring the stability of the material volume in the reactor is the key condition to ensure that the entire reaction process is carried out under steady-state conditions, so that DCB translocated materials can be continuously obtained from the reaction system. The extraction of the translocated materials and the continuous addition of the reaction raw materials jointly maintain the constant volume of the materials in the reactor, so that the entire reaction has good stability, high product selectivity, fewer by-products, low energy consumption, and less waste gas emissions.

[0015] In one possible embodiment, the mass concentration of hydrochloric acid in the hydrochloric acid aqueous solution added in step 2 is 20-30%; And / or, the weight ratio of 2,2'-dichlorohydroazobenzene in the toluene solution of 2,2'-dichlorohydroazobenzene added in step 2 is 40-50%.

[0016] In a possible implementation, the ratio of the aqueous hydrochloric acid solution and the toluene solution of 2,2'-dichlorohydroazobenzene added in step 2 is controlled such that the molar ratio of 2,2'-dichlorohydroazobenzene to hydrochloric acid is 1:4-1:5.

[0017] In the above scheme, the appropriate concentration of raw materials and the proportion of raw material addition are the key factors to ensure the efficient preparation of the product DCB.

[0018] The present invention also provides an apparatus for realizing a method for preparing DCB by continuous loop metathesis reaction, comprising a reactor, an ejector installed on the top of the reactor, an external pipeline connecting the bottom of the reactor with the ejector inlet, and a branch pipeline connecting the top of the reactor with the ejector inlet; a circulating pump, a cooler and a discharge port are arranged on the external pipeline, and the circulating pump, the cooler and the discharge port are arranged on an external pipeline.

[0019] Compared with the prior art, an ejector is used to continuously inject reaction raw materials into the reactor, and a circulating pump is used to discharge the materials in the reactor into a cooler for cooling, thereby ensuring that the reaction temperature in the reactor does not exceed the required reaction temperature range value. The setting of the discharge port facilitates the timely discharge of the transferred materials, ensuring that the materials in the reactor are within a constant volume range, and ensuring that the reaction is carried out under steady-state conditions.

[0020] In a possible implementation, the circulation pump is arranged between the bottom of the reactor and the cooler, and the outlet for leading out the shifted material is arranged at the outlet of the cooler; Preferably, the outlet for exporting the transposed material is connected to a regulating valve, and the outlet of the regulating valve is connected to a transposed material receiving tank.

[0021] In a possible implementation manner, a metering pump is connected to the branch pipe connecting the top of the reactor and the injector inlet.

[0022] In the above scheme, the circulating pump is arranged between the bottom of the reactor and the cooler, and can timely extract the transferred material in the reactor for cooling. The setting of the regulating valve can automatically control the discharge amount, and the setting of the metering pump is used to automatically control the feed amount.

[0023] The beneficial effects of the present invention are: 1. A method for preparing DCB by continuous loop transposition reaction. When a DCB transposition material is continuously prepared by continuous feeding and continuous discharging, the required reactor volume is small, and only one reactor is required to complete the transposition reaction to continuously prepare DCB. The obtained product has high selectivity and few by-products. The content of 3,3'-dichlorobenzidine in the DCB transposition material is ≥90%.

[0024] 2. The DCB transposition reaction is carried out in a closed jet loop continuous reactor, eliminating the large amount of toluene waste gas emissions generated during intermittent kettle reactions.

[0025] 3. The method for preparing DCB by continuous cyclic transposition reaction of the present invention has high reaction efficiency and can save a lot of electric energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure diagram of the equipment for preparing DCB by continuous cyclic translocation reaction of the present invention; Figure 2 Schematic diagram of the material flow of preparing DCB by continuous cyclic transposition reaction of the present invention.

[0027] In the figure, 1. reactor; 2. ejector; 3. external pipeline; 4. circulation pump; 5. cooler; 6. discharge port; 7. regulating valve; 8. transfer material receiving tank; 9. branch pipeline. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0029] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0030] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0031] like Figure 1 As shown, the device for preparing DCB by continuous loop metathesis reaction in the present invention comprises a reactor 1, an ejector 2 installed on the top of the reactor 1, an external pipeline 3 connecting the bottom of the reactor 1 with the inlet of the ejector 2, and a branch pipeline 9 connecting the top of the reactor 1 with the inlet of the ejector 2; the external pipeline 3 is used to realize material circulation, and the branch pipeline 9 is used to realize the addition of reaction raw materials. A metering pump is connected to the branch pipeline 9, which is not shown in the figure.

[0032] Specifically, the external pipeline 3 is provided with a circulation pump 4 for conveying materials, a cooler 5 for cooling materials, and a transposed material discharge port 6 for exporting transposed materials; the circulation pump 4, cooler 5, and discharge port 6 are arranged on an external pipeline 3, the transposed material discharge port 6 is connected to the transposed material receiving tank 8, and an automatic regulating valve 7 for controlling the discharge rate is arranged between the transposed material discharge port 6 and the transposed material receiving tank 8, which is used to automatically control the discharge speed. A liquid level transmitter LI01 is also arranged on the reactor 1, which is used to monitor the liquid level value in the reactor in real time; a temperature transmitter TI01 is also arranged on the reactor 1, which is used to monitor the temperature value in the reactor in real time.

[0033] During the reaction, the direction of all reaction raw materials and reaction materials can be found in Figure 2 As shown in the figure, the arrows indicate the direction of the material.

[0034] Combination Figure 2 The method for preparing DCB by continuous cyclic translocation reaction of the present invention comprises the following steps: Step 1: First, add the pre-reacted pre-metamorphosis product material containing DCB into the reactor 1 equipped with an ejector 2 at the top, start the injection loop continuous reactor 1 circulation pump 4 to circulate the material, and control the material temperature in the reactor 1 between 20-30° C. by the external cooler 5; preferably, the mass concentration of hydrochloric acid in the pre-metamorphosis product material containing DCB is 15%-17%, and the volume of the pre-metamorphosis product material containing DCB added accounts for 50%-80% of the volume of the reactor 1. At the same time, during the circulation process, the volume of the material in the reactor 1 is controlled to account for 50%-70% of the volume of the reactor 1.

[0035] Step 2: Under the condition of maintaining the circulation of the transposed material in the reactor 1, a hydrochloric acid aqueous solution is pumped into the injection loop continuous reactor 1 at a stable flow rate using a metering pump in a branch pipeline 9, and a quantitative toluene solution of 2,2'-dichloroazobenzene is pumped into the injection loop reactor 1 using another metering pump for transposition reaction, and the reaction temperature of the material in the reactor 1 is controlled at 20-30° C. by an external cooler 5, and the automatic regulating valve 7 of the discharge port 6 of the injection loop continuous reaction system is opened to transport the reacted DCB transposed material from the discharge port 6 to the transposed material receiving tank 8. Preferably, the volume of the material in the circulating control reactor 1 accounts for 50%-70% of the volume of the reactor 1, the mass concentration of the added hydrochloric acid aqueous solution is 20%-30%; the weight ratio of 2,2'-dichloroazobenzene in the added 2,2'-dichloroazobenzene toluene solution is 40%-50%, and the addition ratio of the hydrochloric acid aqueous solution and the 2,2'-dichloroazobenzene toluene solution is controlled according to the molar ratio of 2,2'-dichloroazobenzene to hydrochloric acid of 1:4-1:5. During the reaction process, the DCB product can be efficiently prepared by a reactor 1, and the rate of the material circulation pump 4 is preferably 150-200m 3 / h, and the DCB transfer material after the reaction was completed was analyzed by liquid chromatography, and its 3,3'-dichlorobenzidine (DCB) content was ≥90%.

[0036] The following are specific examples.

[0037] Example 1 In volume 1.2m 3 In the jet loop reactor 1, 0.6 m 3 The pre-reacted DCB-containing pre-metamorphosis material is started, and the injection loop continuous reactor 1 and the circulation pump 4 are started to circulate the DCB-containing pre-metamorphosis material, and the material temperature in the continuous reactor 1 is controlled to 20-25° C. by the external cooler 5.

[0038] Under the condition of keeping the transfer material circulation in the reactor 1, use the metering pump of branch pipe 9 to pump 0.12m 3 / h into the injection loop continuous reactor 1, a quantitative amount of 25% hydrochloric acid aqueous solution was pumped in, and at the same time, another metering pump was used to pump 0.1m 3 The toluene solution of 2,2'-dichlorohydroazobenzene is pumped into the injection loop continuous reactor 1 at a flow rate of / h, and the reaction temperature in the reactor 1 is controlled at 20-25°C by an external cooler 5, and the automatic regulating valve 7 at the online discharge port 6 of the injection loop continuous reaction system is opened to transport the DCB transposed material after the reaction is completed to the transposed material receiving tank 8, and the volume of the material in the injection reactor 1 is controlled to be between 50-70% of the effective volume of the reactor 1.

[0039] During the experimental reaction, samples were taken from the front of the inlet of the transfer material receiving tank 8 at regular intervals and analyzed by liquid chromatography. The specific experimental data are shown in Table 1 below: Table 1 Liquid chromatography analysis data in Example 1

[0040] It can be seen from Table 1 that the DCB (3,3'-dichlorobenzidine) content in the transposition product of Example 1 is ≥90%, and there are few by-products.

[0041] Example 2 In volume 1.2m 3 In the jet loop reactor 1, 0.6 m 3 The pre-reacted DCB-containing pre-transposed material is started, the injection loop continuous reactor 1 and the circulation pump 4 are started to circulate the material, and the temperature of the material in the continuous reactor 1 is controlled to 25-30°C through the external cooler 5; Under the condition of keeping the transfer material circulation in the reactor 1, use the metering pump of branch pipe 9 to pump 0.15m 3 / h into the injection loop continuous reactor 1, a quantitative amount of 20% hydrochloric acid aqueous solution was pumped in, and at the same time, another metering pump was used to pump 0.1m 3 The toluene solution of 2,2'-dichlorohydroazobenzene is pumped into the injection loop continuous reactor 1 at a flow rate of / h, and the reaction temperature in the reactor 1 is controlled at 25-30°C by an external cooler 5, and the automatic regulating valve 7 at the online discharge port 6 of the injection loop continuous reaction system is opened to transport the DCB transposition material after the reaction is completed to the transposition material receiving tank 8, and the volume of the material in the injection reactor 1 is controlled to account for 50-70% of the effective volume of the reactor 1.

[0042] During the experimental reaction, samples were taken from the front of the inlet of the transfer material receiving tank 8 at regular intervals and analyzed by liquid chromatography. The specific experimental data are shown in Table 2 below: Table 2 Liquid chromatography analysis data in Example 2

[0043] It can be seen from Table 2 that the DCB (3,3'-dichlorobenzidine) content in the transposition product of Example 2 is ≥90%, and there are few by-products.

[0044] In summary, the method and device for preparing DCB through the continuous cyclic translocation reaction of the present invention can achieve efficient preparation of DCB.

[0045] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for preparing DCB by continuous cyclic translocation reaction, characterized in that: The steps include: Step 1: adding a product material containing DCB and hydrochloric acid prepared by a pre-transposition reaction to prepare DCB into a reactor (1), and circulating the product material containing DCB and hydrochloric acid prepared by a pre-transposition reaction in a circulation loop including the reactor (1) and a cooler (5); Step 2: Adding a hydrochloric acid aqueous solution and a toluene solution of 2,2'-dichloroazobenzene into the reaction kettle (1) to carry out a metathesis reaction, while maintaining the circulation of the materials in the reaction kettle (1), and drawing out the metathesis reaction product at the outlet of the cooler (5).

2. The method for preparing DCB by continuous cyclic translocation reaction according to claim 1, characterized in that: In both step 1 and step 2, the temperature in the reaction kettle (1) is controlled to be 20-30°C.

3. The method for preparing DCB by continuous cyclic translocation reaction according to claim 1, characterized in that: The volume of the product material of the pre-metathesis reaction containing DCB and hydrochloric acid added in step 1 to prepare DCB accounts for 50-80% of the volume of the reactor (1); And / or, during the circulation process of step 1, the total volume of the materials in the reactor (1) is controlled to account for 50-70% of the volume of the reactor (1).

4. The method for preparing DCB by continuous cyclic translocation reaction according to claim 1, characterized in that: The mass concentration of hydrochloric acid in the product material of the pre-transposition reaction containing DCB and hydrochloric acid added in step 1 to prepare DCB is 15-17%.

5. The method for preparing DCB by continuous cyclic translocation reaction according to claim 1, characterized in that: During the circulation process of step 2, the volume of the material in the reaction kettle (1) is controlled to account for 50-70% of the volume of the reaction kettle (1).

6. The method for preparing DCB by continuous cyclic translocation reaction according to claim 1, characterized in that: The hydrochloric acid mass concentration in the hydrochloric acid aqueous solution added in step 2 is 20-30%; And / or, the weight ratio of 2,2'-dichlorohydroazobenzene in the toluene solution of 2,2'-dichlorohydroazobenzene added in step 2 is 40%-50%.

7. The method for preparing DCB by continuous cyclic translocation reaction according to claim 6, characterized in that: The ratio of the hydrochloric acid aqueous solution and the toluene solution of 2,2'-dichlorohydroazobenzene added in step 2 is controlled according to the molar ratio of 2,2'-dichlorohydroazobenzene to hydrochloric acid being 1:4-1:

5.

8. A device for implementing the method for preparing DCB by continuous cyclic metathesis reaction according to any one of claims 1 to 6, characterized in that: It comprises a reaction kettle (1), an ejector (2) installed on the top of the reaction kettle (1), an external pipeline (3) connecting the bottom of the reaction kettle (1) and the inlet of the ejector (2), and a branch pipeline (9) connecting the top of the reaction kettle (1) and the inlet of the ejector (2); The external pipeline (3) is provided with a circulation pump (4), a cooler (5) and a discharge port (6); the circulation pump (4), the cooler (5) and the discharge port (6) are arranged on an external pipeline (3).

9. The device according to claim 8, characterized in that The circulation pump (4) is arranged between the bottom of the reaction kettle (1) and the cooler (5), and the discharge port (6) is arranged at the outlet of the cooler (5); Preferably, the discharge port (6) is connected to a regulating valve (7), and the outlet of the regulating valve (7) is connected to a transfer material receiving tank (8).

10. The device according to claim 8, characterized in that A metering pump is connected to the branch pipe (9) connecting the top of the reaction kettle (1) and the inlet of the ejector (2).

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