A mixed dinitrobenzene synthesis process and system

Abstract

The present invention relates to the technical field of organic intermediate preparation, and in particular to a mixed dinitrobenzene synthesis process and system thereof, comprising the following steps: S1, mixing concentrated nitric acid and sulfuric acid, cooling to obtain a primary mixed acid, passing benzene and the primary mixed acid into a primary nitration microreactor equipped with a composite catalyst for nitration to carry out a primary nitration reaction, and separating to obtain nitrobenzene and dilute sulfuric acid; S2, mixing concentrated nitric acid and sulfuric acid, cooling to obtain a secondary mixed acid, passing nitrobenzene and the secondary mixed acid into a primary nitration microreactor equipped with a composite catalyst for nitration to carry out a secondary nitration reaction, and obtaining mixed dinitrobenzene and sulfuric acid. The present invention adopts a nitration microreactor to carry out a two-stage nitration reaction, which can enhance the mass transfer efficiency and the rapid exchange of heat between reactants, effectively avoid the side reactions caused by local overheating, reduce the generation of by-products, thereby improving the utilization rate of raw materials and the purity of products.

Description

Technical Field

[0001] The invention relates to the technical field of organic intermediate preparation, and in particular to a mixed dinitrobenzene synthesis process and a system thereof. Background Art

[0002] Mixed dinitrobenzene (DNB) is a nitro derivative of benzene, including m-dinitrobenzene, p-dinitrobenzene and o-dinitrobenzene. It has a yellow transparent crystalline appearance, with volatility and bitter almond odor. It is toxic and can be inhaled through the skin or respiratory organs. It is irritating to the eyes and is flammable and explosive. In industry, mixed dinitrobenzene is mainly used in dyes, pigments and organic synthesis intermediates, among which m-dinitrobenzene is particularly widely used.

[0003] In the prior art, there are various methods for producing mixed dinitrobenzene, but there are some common problems. For example, although the traditional high-acidity continuous nitration process has a large production capacity, it has a poor operating environment, a violent exothermic production, is difficult to control, and produces a large amount of waste acid. The intermittent operation process has the disadvantages of small production capacity, poor production process stability, poor operating environment, and high labor intensity. Summary of the invention

[0004] In order to solve the problems mentioned in the above background technology, the present invention provides a mixed dinitrobenzene synthesis process and system thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A mixed dinitrobenzene synthesis process comprises the following steps:

[0007] S1. In a primary acid mixer, concentrated nitric acid (HNO3 mass fraction ≥ 98.0%) and sulfuric acid with a mass fraction of 80-82% are mixed and cooled with circulating water or water below 7°C to obtain a primary mixed acid. Benzene (purity ≥ 99.9%) and the primary mixed acid are introduced into a primary nitration microreactor equipped with a composite catalyst for nitration to carry out a primary nitration reaction. After the reaction is completed, they are introduced into an extraction pot for extraction to separate nitrobenzene and 72% dilute sulfuric acid. The extracted acidic benzene is returned to the primary nitration microreactor, and the 72% dilute sulfuric acid is sent to a waste acid concentration device;

[0008] S2. In a secondary mixed acid mixer, concentrated nitric acid (HNO3 mass fraction ≥ 98.0%) and 90-95% sulfuric acid are mixed and cooled with 7°C water to obtain a secondary mixed acid. Nitrobenzene and the secondary mixed acid are introduced into a secondary nitration microreactor equipped with a composite catalyst for nitration to carry out a secondary nitration reaction. The reaction product is diluted by spraying water and cooled to room temperature before entering a nitration separator for separation to obtain mixed dinitrobenzene and 82% sulfuric acid. The residual sulfuric acid in the mixed dinitrobenzene is separated by a nitration acid separator and recovered to the primary nitration microreactor.

[0009] Furthermore, the composite catalyst for nitration in step S2 comprises the following steps:

[0010] A1. Add styrene and divinylbenzene into a reaction kettle, exhaust the air in the kettle with nitrogen, add dibenzoyl peroxide, heat to 75-85°C, stir at 200-300 rpm, keep warm for 20-26 hours, and centrifuge to obtain polystyrene-divinylbenzene microspheres;

[0011] A2. Add polystyrene-divinylbenzene microspheres to toluene and disperse them with an ultrasonic disperser for 20-30 minutes to obtain a polystyrene-divinylbenzene suspension. Add titanium zirconium oxide powder to anhydrous ethanol and stir until a transparent or translucent solution is formed to obtain a titanium zirconium oxide solution. Use a constant flow pump to slowly drop the titanium zirconium oxide solution into the polystyrene-divinylbenzene suspension at a rate of 5 mL / min, heat to 45-55° C., stir at a speed of 200-300 rpm, keep the reaction warm for 6-8 hours, centrifuge, wash, and dry to obtain a composite catalyst for nitration.

[0012] Furthermore, in step S1, the temperature of the primary nitration reaction is controlled to be 75-95° C., and the reaction pressure is 0.9-1.60 MPa.

[0013] Furthermore, in step S2, the temperature of the secondary nitration reaction is 85-105° C., and the reaction pressure is 0.70-1.55 MPa.

[0014] Furthermore, in step S1, the primary mixed acid is cooled to 41-54°C, and in step S2, the secondary mixed acid is cooled to 8-24°C.

[0015] Furthermore, in step S1, the feed mass ratio of concentrated nitric acid and 80-82% sulfuric acid is (6-7):1, and the feed mass ratio of benzene, primary mixed acid and composite catalyst for nitration is 1:(1-1.5):(0.04-0.08).

[0016] Furthermore, in step S2, the feed mass ratio of sulfuric acid with a mass fraction of 90-95% to concentrated nitric acid is (4-5):1, and the feed mass ratio of nitrobenzene, secondary mixed acid and composite catalyst for nitration is 1:(1.2-2):(0.08-0.14).

[0017] Furthermore, in step A1, the mass ratio of styrene, divinylbenzene and dibenzoyl peroxide is (8-9): (2-3): (0.05-0.1).

[0018] Furthermore, in step A2, the mass ratio of the polystyrene-divinylbenzene suspension to the titanium zirconium oxide solution is (10-12):1.

[0019] According to another aspect of the present invention, there is provided a system for synthesizing mixed dinitrobenzene as described above, comprising a raw material processing unit, a mixed acid preparation unit, a nitration reaction unit and a post-processing unit, wherein the raw material processing unit comprises a feeding pump and a raw material storage tank, the mixed acid preparation unit comprises a primary acid mixer, a primary cooler, a secondary acid mixer and a deep cooler, the nitration reaction unit comprises a primary nitration microreactor and a secondary nitration microreactor, and the post-processing unit comprises an extraction pot, a waste acid concentration device and a nitration separator.

[0020] Beneficial effects of the present invention:

[0021] 1. In this technical solution, the composite catalyst for nitration is composed of a polystyrene-divinylbenzene microsphere core and a titanium zirconium oxide modified layer. The microsphere core is prepared by free radical polymerization, and the interior of the microsphere is composed of cross-linked polymer chains, forming a stable network structure, ensuring the shape stability and excellent mechanical properties of the microsphere. Titanium zirconium oxide is loaded on the surface of the microsphere to form a uniform and dense covering layer. Titanium atoms are embedded in the modified layer with a specific lattice structure, which serves as a catalytic active site and provides sufficient reaction space for the nitration reaction. The composite catalyst for nitration can effectively reduce the activation energy of the nitration reaction, significantly accelerate the reaction rate, and at the same time improve the selective generation of the target product mixed dinitrobenzene, reduce the generation of by-products, thereby improving the utilization rate of raw materials and the purity of the product.

[0022] 2. In this technical solution, a two-stage nitration reaction is carried out using a nitration microreactor, which can enhance the mass transfer efficiency and rapid heat exchange between the reactants, effectively avoid side reactions caused by local overheating, and ensure the stability of product quality.

[0023] 3. In this technical solution, different concentrations of primary mixed acid and secondary mixed acid are prepared according to the requirements of different nitration stages, which is conducive to the production of the target product mixed dinitrobenzene, while reducing the situation of excessive nitration or incomplete nitration. The 72% dilute sulfuric acid and 82% sulfuric acid produced in the process can be reused in other chemical processes or as raw materials after proper treatment, which not only reduces the demand for fresh sulfuric acid, but also reduces the pollution of waste acid emissions to the environment. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0026] Preparation Example 1

[0027] The composite catalyst for nitration comprises the following steps to prepare:

[0028] A1. 8 kg of styrene and 2 kg of divinylbenzene were put into a reaction kettle, the air in the kettle was exhausted with nitrogen, 0.05 kg of dibenzoyl peroxide was added, the reaction was heated to 75 ° C, stirred at a speed of 200 rpm, and the reaction was kept warm for 20 hours. After centrifugation, polystyrene-divinylbenzene microspheres were obtained;

[0029] A2. Add polystyrene-divinylbenzene microspheres to toluene and disperse them with an ultrasonic disperser for 20 minutes at a power of 200 W to obtain a polystyrene-divinylbenzene suspension. Add titanium zirconium oxide powder to anhydrous ethanol and stir until a transparent or translucent solution is formed to obtain a titanium zirconium oxide solution. Use a constant flow pump to slowly drop 1 kg of the titanium zirconium oxide solution into 10 kg of the polystyrene-divinylbenzene suspension at a rate of 5 mL / min. Heat to 45°C, stir at a speed of 200 rpm, keep the reaction warm for 6 hours, centrifuge, wash, and dry to obtain a composite catalyst for nitration.

[0030] Preparation Example 2

[0031] The composite catalyst for nitration comprises the following steps to prepare:

[0032] A1. 8.5 kg of styrene and 2.5 kg of divinylbenzene were put into a reaction kettle, the air in the kettle was exhausted with nitrogen, 0.07 kg of dibenzoyl peroxide was added, the reaction mixture was heated to 80°C, stirred at 250 rpm, and kept warm for 23 hours. After centrifugation, polystyrene-divinylbenzene microspheres were obtained;

[0033] A2. Add polystyrene-divinylbenzene microspheres to toluene and disperse them with an ultrasonic disperser for 25 minutes at a power of 200 W to obtain a polystyrene-divinylbenzene suspension. Add titanium zirconium oxide powder to anhydrous ethanol and stir until a transparent or translucent solution is formed to obtain a titanium zirconium oxide solution. Use a constant flow pump to slowly drop 1 kg of the titanium zirconium oxide solution into 11 kg of the polystyrene-divinylbenzene suspension at a rate of 5 mL / min. Heat to 50°C, stir at a speed of 250 rpm, keep the reaction warm for 7 hours, centrifuge, wash, and dry to obtain a composite catalyst for nitration.

[0034] Preparation Example 3

[0035] The composite catalyst for nitration comprises the following steps to prepare:

[0036] A1. 9 kg of styrene and 3 kg of divinylbenzene were put into a reaction kettle, the air in the kettle was exhausted with nitrogen, 0.1 kg of dibenzoyl peroxide was added, the reaction was heated to 85 ° C, stirred at a speed of 300 rpm, and the reaction was kept warm for 26 hours. After centrifugation, polystyrene-divinylbenzene microspheres were obtained;

[0037] A2. Add polystyrene-divinylbenzene microspheres to toluene and disperse them with an ultrasonic disperser for 30 minutes at a power of 200 W to obtain a polystyrene-divinylbenzene suspension. Add titanium zirconium oxide powder to anhydrous ethanol and stir until a transparent or translucent solution is formed to obtain a titanium zirconium oxide solution. Use a constant flow pump to slowly drop 1 kg of the titanium zirconium oxide solution into 12 kg of the polystyrene-divinylbenzene suspension at a rate of 5 mL / min. Heat to 55° C. and stir at a speed of 300 rpm. Keep the reaction warm for 8 hours, centrifuge, wash, and dry to obtain a composite catalyst for nitration. Example 1

[0038] A mixed dinitrobenzene synthesis process comprises the following steps:

[0039] S1. In a primary acid mixer, 60 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 10 kg of sulfuric acid with a mass fraction of 80% are mixed, and cooled to 41 ° C with 5 ° C water to obtain a primary mixed acid, 10 kg of benzene (with a purity of 99.9%) and 10 kg of the primary mixed acid are passed into a primary nitration microreactor equipped with 0.4 kg of the composite catalyst for nitration obtained in Preparation Example 1, and a primary nitration reaction is carried out at 75 ° C and 0.9 MPa for 6 hours. After the reaction is completed, it is passed into an extraction pot for extraction to separate nitrobenzene and 72% dilute sulfuric acid;

[0040] S2. In a secondary mixed acid mixer, 10 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 40 kg of 90% sulfuric acid with a mass fraction are mixed, and the mixture is cooled to 8 ° C with 7 ° C water to obtain a secondary mixed acid. 10 kg of nitrobenzene and 12 kg of the secondary mixed acid are introduced into a secondary nitration microreactor containing 0.8 kg of the composite catalyst for nitration prepared in Preparation Example 1, and the secondary nitration reaction is carried out at 85 ° C and 0.70 MPa for 12 hours. The reaction product is diluted by spraying water and cooled to room temperature, and then enters a nitration separator for separation to obtain mixed dinitrobenzene and 82% sulfuric acid. The residual sulfuric acid in the mixed dinitrobenzene is separated by a nitration acid separator and recovered to the primary nitration microreactor. Example 2

[0041] A mixed dinitrobenzene synthesis process comprises the following steps:

[0042] S1. In a primary acid mixer, 65 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 10 kg of sulfuric acid with a mass fraction of 81% are mixed, and cooled to 50 ° C with 5 ° C water to obtain a primary mixed acid. 10 kg of benzene (with a purity of 99.9%) and 12.5 kg of the primary mixed acid are introduced into a primary nitration microreactor equipped with 0.6 kg of the composite catalyst for nitration obtained in Preparation Example 2, and a primary nitration reaction is carried out at 86 ° C and 1.21 MPa for 10 hours. After the reaction is completed, it is introduced into an extraction pot for extraction to separate nitrobenzene and 72% dilute sulfuric acid;

[0043] S2. In a secondary mixed acid mixer, 10 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 46 kg of 93% sulfuric acid with a mass fraction are mixed and cooled to 12 ° C with 7 ° C water to obtain a secondary mixed acid. 10 kg of nitrobenzene and 18 kg of the secondary mixed acid are introduced into a secondary nitration microreactor equipped with 1.1 kg of the composite catalyst for nitration prepared in Preparation Example 2, and the secondary nitration reaction is carried out at 95 ° C and 1.05 MPa for 18 hours. The reaction product is diluted by spraying water and cooled to room temperature and then enters a nitration separator for separation to obtain mixed dinitrobenzene and 82% sulfuric acid. The residual sulfuric acid in the mixed dinitrobenzene is separated by a nitration acid separator and recovered to the primary nitration microreactor. Example 3

[0044] A mixed dinitrobenzene synthesis process comprises the following steps:

[0045] S1. In a primary acid mixer, 70 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 10 kg of sulfuric acid with a mass fraction of 82% are mixed, and cooled to 54 ° C with 5 ° C water to obtain a primary mixed acid, 10 kg of benzene (with a purity of 99.9%) and 15 kg of the primary mixed acid are passed into a primary nitration microreactor equipped with 0.8 kg of the composite catalyst for nitration obtained in Preparation Example 3, and a primary nitration reaction is carried out at 95 ° C and 1.60 MPa for 12 hours. After the reaction is completed, it is passed into an extraction pot for extraction to separate nitrobenzene and 72% dilute sulfuric acid;

[0046] S2. In a secondary mixed acid mixer, 10 kg of concentrated nitric acid (HNO3 with a mass fraction of 98.5%) and 50 kg of 95% sulfuric acid are mixed and cooled to 24 ° C with 7 ° C water to obtain a secondary mixed acid. 10 kg of nitrobenzene and 20 kg of the secondary mixed acid are introduced into a secondary nitration microreactor equipped with 1.4 kg of the composite catalyst for nitration prepared in Preparation Example 3. The secondary nitration reaction is carried out at 105 ° C and 1.55 MPa for 24 hours. The reaction product is diluted by spraying water and cooled to room temperature and then enters a nitration separator for separation to obtain mixed dinitrobenzene and 82% sulfuric acid. The residual sulfuric acid in the mixed dinitrobenzene is separated by a nitration acid separator and recovered to the primary nitration microreactor.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that polystyrene is used instead of the composite catalyst for nitration, and the remaining steps are the same as those in Example 1.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 2 is that titanium zirconium oxide is used instead of the composite catalyst for nitration, and the remaining steps are the same as those in Example 2.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 3 is that divinylbenzene is used instead of the composite catalyst for nitration, and the remaining steps are the same as those in Example 3.

[0053] The yield and purity of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1:

[0054] Table 1. Purity and yield results of Examples 1-3 and Comparative Examples 1-3

[0055] serial number Yield (%) purity(%) Example 1 85.7 98.9 Example 2 86.5 98.9 Example 3 86.8 98.8 Comparative Example 1 71.3 97.9 Comparative Example 2 74.2 98.1 Comparative Example 3 70.6 97.5

[0056] As shown in Table 1, when the composite catalyst for nitration is used in Examples 1-3, the yield and purity of mixed dinitrobenzene are significantly higher than that of the single catalyst or substitute used in Comparative Examples 1-3, indicating that the composite catalyst for nitration has a certain catalytic effect in the synthesis process of mixed dinitrobenzene.

[0057] The composite catalyst for nitration is composed of polystyrene-divinylbenzene microspheres and titanium zirconium oxide, and these two components may have a synergistic catalytic effect. As a carrier, polystyrene-divinylbenzene microspheres have good dispersibility and stability, which can increase the active surface area of ​​the catalyst; while titanium zirconium oxide may be used as an active ingredient to promote the nitration reaction. This synergistic effect enables the composite catalyst to show excellent catalytic performance in the synthesis of mixed dinitrobenzene. In addition, polystyrene-divinylbenzene microspheres have a porous structure, which can provide more active sites, which is conducive to the adsorption and conversion of reactants. At the same time, the addition of titanium zirconium oxide may further improve the structural characteristics of the catalyst, making it more conducive to the nitration reaction.

[0058] In summary, the composite catalyst for nitration prepared in Preparation Examples 1-3 exhibits a significant catalytic effect in the synthesis of mixed dinitrobenzene, so that the mixed dinitrobenzene prepared in Examples 1-3 has a higher purity and yield.

[0059] In the description of the specification, the description with reference to the terms "preparation example", "embodiment", "various embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or preparation example are included in at least one embodiment or preparation example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or preparation examples in a suitable manner.

[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A mixed dinitrobenzene synthesis process, characterized in that: The following steps are involved: S1. Mix concentrated nitric acid and sulfuric acid with a mass fraction of 80-82%, and after cooling, obtain a primary mixed acid. Pass benzene and the primary mixed acid into a primary nitration microreactor equipped with a composite catalyst for nitration to carry out a primary nitration reaction. After the reaction is completed, pass it into an extraction pot for extraction to separate nitrobenzene and 72% dilute sulfuric acid; S2, mixing concentrated nitric acid and sulfuric acid with a mass fraction of 90-95%, cooling to obtain a secondary mixed acid, passing nitrobenzene and the secondary mixed acid into a primary nitration microreactor equipped with a composite catalyst for nitration to carry out a secondary nitration reaction, and separating the reaction product after dilution by spraying water and cooling to room temperature to obtain mixed dinitrobenzene and 82% sulfuric acid; Wherein, the composite catalyst for nitration in step S1 and step S2 comprises the following steps to prepare: A1. Add styrene and divinylbenzene into a reaction kettle, exhaust the air in the kettle with nitrogen, add dibenzoyl peroxide, heat to 75-85°C, stir at 200-300 rpm, keep warm for 20-26 hours, and centrifuge to obtain polystyrene-divinylbenzene microspheres; A2, adding polystyrene-divinylbenzene microspheres to toluene, dispersing for 20-30 minutes with an ultrasonic disperser to obtain a polystyrene-divinylbenzene suspension, adding titanium zirconium oxide powder to anhydrous ethanol, stirring to form a transparent or translucent solution to obtain a titanium zirconium oxide solution, slowly adding the titanium zirconium oxide solution dropwise to the polystyrene-divinylbenzene suspension at a speed of 5 mL / min with a constant flow pump, heating to 45-55 ° C, stirring at a speed of 200-300 rpm, keeping the reaction warm for 6-8 hours, centrifuging, washing, and drying to obtain a composite catalyst for nitration; In step S1, the feed mass ratio of concentrated nitric acid and 80-82% sulfuric acid is (6-7):1, and the feed mass ratio of benzene, primary mixed acid and composite catalyst for nitration is 1:(1-1.5):(0.04-0.08); In step S2, the feed mass ratio of 90-95% sulfuric acid to concentrated nitric acid is (4-5):1, and the feed mass ratio of nitrobenzene, secondary mixed acid and composite catalyst for nitration is 1:(1.2-2):(0.08-0.14); In step A1, the mass ratio of styrene, divinylbenzene and dibenzoyl peroxide is (8-9): (2-3): (0.05-0.1); The mass ratio of the polystyrene-divinylbenzene suspension to the titanium zirconium oxide solution in step A2 is (10-12):

1.

2. A mixed dinitrobenzene synthesis process according to claim 1, characterized in that: The temperature of the primary nitration reaction in step S1 is controlled to be 75-95° C., and the reaction pressure is 0.9-1.60 MPa.

3. A mixed dinitrobenzene synthesis process according to claim 1, characterized in that: The temperature of the secondary nitration reaction in step S2 is 85-105° C., and the reaction pressure is 0.70-1.55 MPa.

4. A mixed dinitrobenzene synthesis process according to claim 1, characterized in that: In step S1, the primary mixed acid is cooled to 41-54°C, and in step S2, the secondary mixed acid is cooled to 8-24°C.