阅读说明：本技术 一种微通道反应器合成芳香类硝基化合物的方法 (Method for synthesizing aromatic nitro compound by using microchannel reactor ) 是由 吴孝举 姜友法 王振峰 姜瑞 董前进 孙鹏 于 2020-09-04 设计创作，主要内容包括：本发明公开了一种微通道反应器合成芳香类硝基化合物的方法,以对甲砜基甲苯、硫酸、硝酸为原料,将原料连续化输送至微通道反应器中进行反应。本发明将微通道反应器用于2-硝基-4-磺酰甲基甲苯的制备,微通道反应器的高比面积能够实现快速传热并保持恒温,反应物料在瞬间混合快速反应,热量可以及时导出,消除局部过热,降低生产危险性并且大大提高了生产效率。(The invention discloses a method for synthesizing aromatic nitro compounds by a microchannel reactor, which takes p-methylsulfonyl toluene, sulfuric acid and nitric acid as raw materials, and continuously conveys the raw materials to the microchannel reactor for reaction. The microchannel reactor is used for preparing the 2-nitro-4-sulfonyl methyl toluene, the high specific area of the microchannel reactor can realize rapid heat transfer and keep constant temperature, reaction materials are instantly mixed and rapidly react, heat can be timely led out, local overheating is eliminated, production danger is reduced, and production efficiency is greatly improved.)

1. A method for synthesizing aromatic nitro compounds by using a microchannel reactor takes p-methylsulfonyl toluene, sulfuric acid and nitric acid as raw materials, and the raw materials are continuously conveyed into the microchannel reactor for reaction, and is characterized by comprising the following steps:

(1) preparing a p-methylsulfonyl toluene sulfuric acid solution: at room temperature, according to the mass ratio of 1: 2.0-5.0 mixing and stirring p-methylsulfonyl toluene and sulfuric acid, and slowly dripping water under the condition of ice water bath to obtain a p-methylsulfonyl toluene sulfuric acid solution for later use, wherein the mass concentration of the sulfuric acid is 70-95%;

(2) synthesis of 2-nitro-4-sulfonylmethyltoluene: respectively conveying fuming nitric acid and the p-methylsulfonyl toluene sulfuric acid solution obtained in the step (1) to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, and controlling the molar ratio of the fuming nitric acid to the p-methylsulfonyl toluene to be 1.0-1.5: instantly mixing two streams of liquid in a microchannel reactor at 20-60 ℃, controlling the reaction residence time of the materials in the microchannel reactor to be 0.5-3.0 min, controlling the discharge flow of a discharge port through a needle valve so as to control the reaction pressure of the microchannel reactor to be 0.1-1.5 Mpa, transferring the reaction liquid into ice water after the reaction is finished, and sequentially carrying out cooling, suction filtration, ice water leaching and vacuum drying treatment to obtain the aromatic nitro compound, namely 2-nitro-4-sulfonylmethyl toluene.

2. The method as claimed in claim 1, wherein in the step (1), the mass ratio of the p-methylsulfonyltoluene to the sulfuric acid is 1: 3.0-5.0.

3. The method according to claim 1, wherein in the step (1), the concentration of the sulfuric acid is 70-90%.

4. The method of claim 3, wherein the sulfuric acid concentration is 80%.

5. The method according to claim 1, wherein in the step (2), the molar ratio of fuming nitric acid to p-methylsulfonyltoluene is 1.0-1.2: 1.

6. the method according to claim 1, wherein in the step (2), the reaction temperature of the microchannel reactor is 40-60 ℃.

7. The method of claim 1, wherein in step (2), the residence time of the material in the microchannel reactor is 1.0-3.0 min.

8. The method as claimed in claim 1, wherein the microchannel reactor is made of PDMS or Hasc, the cross-sectional shape of the microchannel is circular, square or rectangular, the diameter of the microchannel is 200-500 μm, the length of the microchannel is 500-1000mm, and the layout of the microchannel is linear, L-shaped, continuous S-shaped or spiral.

Technical Field

The invention relates to a synthetic method of an aromatic nitro compound, in particular to a method for synthesizing the aromatic nitro compound by a microchannel reactor, belonging to the technical field of synthesis of energetic compounds.

Background

The 2-nitro-4-sulfonylmethyl toluene is an important intermediate for synthesizing the herbicide mesotrione, has a melting point of 120-121 ℃, is insoluble in water, diethyl ether and ethanol, is easily soluble in solvents such as chloroform, acetonitrile and ethyl acetate, and is a white powdery solid in appearance.

The main synthesis method of 2-nitro-4-sulfonyl methyl toluene is to react p-methylsulfonyl toluene, nitric acid and sulfuric acid as raw materials to ensure that hydrogen on methyl ortho-position carbon on benzene ring is replaced by-NO₂And (4) substitution, wherein a substitution reaction is carried out to generate a product.

The literature reports that the 2-nitro-4-sulfonyl methyl toluene synthesis reaction has violent heat release, and the explosion risk exists in the reaction process due to improper temperature control. In addition, in the conventional kettle type reaction process, if the adding speed of nitric acid is not stable and the materials are not uniformly mixed, the reaction liquid is easily overheated locally, and organic materials are easily coked in a concentrated sulfuric acid system, so that dinitro byproducts and other oxidation byproducts are easily generated. Meanwhile, a large amount of 2-nitro-4-sulfonyl methyl toluene is easy to crystallize and separate out in the later reaction stage, so that the fluidity of the reaction liquid is poor, the materials are bound to the wall, and the reaction risk is greatly improved. Therefore, the solving of safety problems, the control of byproducts and the improvement of the fluidity of reaction liquid are key technical problems in the synthesis and production process of the 2-nitro-4-sulfonyl methyl toluene.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for synthesizing aromatic nitro compounds by a microchannel reactor, aiming at the defects in the prior art, and the method is a method for synthesizing 2-nitro-4-sulfonyl methyl toluene by the microchannel reactor, which has high safety, less byproducts and high production efficiency.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for synthesizing aromatic nitro compounds by a microchannel reactor takes p-methylsulfonyl toluene, sulfuric acid and nitric acid as raw materials, and the raw materials are continuously conveyed into the microchannel reactor for reaction, and the method comprises the following steps:

(1) preparing a p-methylsulfonyl toluene sulfuric acid solution: at room temperature, according to the mass ratio of 1: 2.0-5.0 mixing and stirring p-methylsulfonyl toluene and sulfuric acid, and slowly dripping water under the condition of ice water bath to obtain a p-methylsulfonyl toluene sulfuric acid solution for later use, wherein the mass concentration of the sulfuric acid is 70-95%;

(2) synthesis of 2-nitro-4-sulfonylmethyltoluene: respectively conveying fuming nitric acid and the p-methylsulfonyl toluene sulfuric acid solution obtained in the step (1) to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, and controlling the molar ratio of the fuming nitric acid to the p-methylsulfonyl toluene to be 1.0-1.5: instantly mixing two streams of liquid in a microchannel reactor at 20-60 ℃, controlling the reaction residence time of the materials in the microchannel reactor to be 0.5-3.0 min, controlling the discharge flow of a discharge port through a needle valve so as to control the reaction pressure of the microchannel reactor to be 0.1-1.5 Mpa, transferring the reaction liquid into ice water after the reaction is finished, and sequentially carrying out cooling, suction filtration, ice water leaching and vacuum drying treatment to obtain the aromatic nitro compound, namely 2-nitro-4-sulfonylmethyl toluene.

In the technical scheme, in the step (1), the mass ratio of the p-methylsulfonyltoluene to the sulfuric acid is preferably 1: 3.0-5.0.

In the above technical solution, in the step (1), the concentration of the sulfuric acid is preferably 70 to 90%, and more preferably 80%.

In the above technical scheme, in the step (2), the molar ratio of fuming nitric acid to p-methylsulfonyl toluene is preferably 1.0-1.2: 1.

in the above technical scheme, in the step (2), the reaction temperature of the microchannel reactor is preferably 40-60 ℃.

In the technical scheme, in the step (2), the reaction residence time of the material in the microchannel reactor is preferably 1.0-3.0 min.

In the above technical solution, the microchannel reactor is made of PDMS or Hash C, the cross section of the microchannel is circular, square or rectangular, the diameter of the microchannel is 200-500 μm, the length of the microchannel is 500-1000mm, and the microchannel is arranged in a linear, L-shaped, continuous S-shaped or spiral shape.

The microchannel reactor is used for preparing the 2-nitro-4-sulfonyl methyl toluene, the high specific area of the microchannel reactor can realize rapid heat transfer and keep constant temperature, reaction materials are instantly mixed and rapidly react, heat can be timely led out, local overheating is eliminated, production danger is reduced, and production efficiency is greatly improved.

Compared with the prior art, the invention has the following remarkable advantages:

(1) the invention utilizes the microchannel reactor to prepare the 2-nitro-4-sulfonyl methyl toluene, realizes the continuous production of the methyl toluene and is easy to amplify.

(2) Due to the high specific area of the microchannel reactor, the heat exchange performance of the reaction system is far higher than that of a conventional reactor, the problem of local overheating of the reaction system is avoided, the risk coefficient is greatly reduced, and meanwhile, the use of a large-scale cooling system is avoided, and the energy consumption is reduced.

(3) The reaction is carried out in the microchannel reactor in a continuous flow mode, and the reaction time of the reaction liquid in the microchannel reactor can be accurately controlled by adjusting the flow rate of reactants and the length of the microchannel.

(4) Reactant fluid flows in a laminar flow state in the microchannel, mixing is carried out by diffusion, materials can be instantly mixed in the microchannel reactor, the reaction is fast, and the production efficiency is greatly improved.

(5) The yield and the purity of the 2-nitro-4-sulfonyl methyl toluene prepared by the invention are both obviously improved.

In conclusion, the method has the advantages of simple process, convenience in operation, high safety, capability of realizing industrial production and good application value.

Drawings

FIG. 1 is a process flow diagram for preparing 2-nitro-4-sulfonylmethyltoluene by using a microchannel reactor.

FIG. 2 is a graph showing the results of the effect of sulfuric acid concentration on the synthesis of 2-nitro-4-sulfonylmethyltoluene in example 1 (wherein ▇ represents conversion and ● represents purity).

FIG. 3 is a graph showing the results of the effect of temperature on the synthesis of 2-nitro-4-sulfonylmethyltoluene in example 2 (wherein ▇ represents conversion and ● represents purity).

FIG. 4 is a graph showing the results of the effect of microchannel residence time on the synthesis of 2-nitro-4-sulfonylmethyltoluene in example 3 (wherein ▇ represents conversion and ● represents purity).

FIG. 5 is a graph showing the effect of the molar ratio of p-methylsulfonyltoluene to nitric acid on the synthesis of 2-nitro-4-sulfonylmethyltoluene in example 4 (wherein ▇ represents conversion and ● represents purity).

FIG. 6 is a graph showing the results of the effect of microchannel pressure on the synthesis of 2-nitro-4-sulfonylmethyltoluene in example 5 (wherein ▇ represents conversion and ● represents purity).

Detailed Description

The following detailed description of the embodiments of the present invention is provided, but the present invention is not limited to the following descriptions:

in the following embodiments of the present invention, the layout of the microchannel reactor is linear, the cross-sectional shape of the microchannel is circular, the material of the microchannel counter chip is PDMS, the diameter of the microchannel is 200-500 μm, and the length of the microchannel is 500-1000 mm.

The invention will now be illustrated with reference to specific examples:

example 1:

(1) at room temperature, according to the mass ratio of 1: and 3, mixing and dissolving the p-methylsulfonyl toluene and the sulfuric acid, stirring, and slowly dripping water in an ice water bath to ensure that the concentrations of the sulfuric acid are respectively 70%, 75%, 80%, 85% and 90%, so as to obtain a p-methylsulfonyl toluene sulfuric acid solution.

(2) The method comprises the steps of respectively conveying a p-methylsulfonyl toluene sulfuric acid solution and fuming nitric acid to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, controlling the molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid to be 1:1.2, instantly mixing and contacting two streams of liquid in the microchannel reactor at 45 ℃ to react, controlling the discharge flow through a needle valve at a discharge outlet, controlling the reaction pressure of the microchannel to be 0.3MPa, conveying the reaction liquid to ice water, filtering, washing with the ice water, and drying in vacuum to obtain the 2-nitro-4-sulfonylmethyl toluene. The reaction liquid stays in the microchannel reactor for 2 min. The conversion and purity of 2-nitro-4-sulfonylmethyltoluene are shown in Table 1 and FIG. 2.

TABLE 1 Effect of sulfuric acid concentration on the Synthesis of 2-nitro-4-sulfonylmethyltoluenes

Sulfuric acid concentration%	70	75	80	85	90
						Conversion rate%	90.54	93.58	98.47	98.45	98.50
Purity%	91.10	94.03	98.89	98.75	98.81

Analysis data shows that the concentration of sulfuric acid has certain influence on nitration synthesis, and the synthesis conversion rate is in direct proportion to the concentration of sulfuric acid. When the concentration of the sulfuric acid is more than or equal to 80 percent, the conversion rate tends to be stable.

Example 2:

(1) a p-methylsulfonyl toluene sulfuric acid solution was prepared in the same manner as in example 1, wherein the sulfuric acid concentration was 80%.

(2) The method comprises the steps of respectively conveying a p-methylsulfonyl toluene sulfuric acid solution and fuming nitric acid to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, controlling the molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid to be 1:1.2, instantly mixing and contacting two streams of liquid in the microchannel reactor at 40-60 ℃ to react, controlling the discharge flow through a needle valve at a discharge outlet, controlling the reaction pressure of a microchannel to be 0.2MPa, conveying a reaction liquid to ice water, filtering, washing the ice water, and drying in vacuum to obtain the 2-nitro-4-sulfonylmethyl toluene. The reaction liquid stays in the microchannel reactor for 2 min. The conversion and purity of 2-nitro-4-sulfonylmethyltoluene are shown in Table 2 and FIG. 3.

TABLE 2 Effect of temperature on the Synthesis of 2-nitro-4-sulfonylmethyltoluenes

T/℃	40	45	50	55	60
						Conversion rate%	96.54	97.58	99.17	99.05	98.03
Purity%	97.02	98.21	99.26	99.10	98.19

The analysis data shows that when the reaction temperature is lower than 40 ℃, the material in the microreactor is crystallized out to cause channel blockage, and the conversion rate and the purity of the 2-nitro-4-sulfonyl methyl toluene are gradually increased along with the increase of the temperature; but when the temperature is 50 ℃, the conversion rate and the purity respectively reach 99.17 percent and 99.26 percent; when T is more than or equal to 55 ℃, the conversion rate and the purity have obvious reduction tendency, probably because the high temperature is not beneficial to the forward proceeding of the nitration reaction and dinitro by-products are generated.

Example 3:

(1) a solution of p-methylsulfonyltoluenesulfuric acid was prepared in the same manner as in example 2.

(3) The method comprises the steps of respectively conveying a p-methylsulfonyl toluene sulfuric acid solution and fuming nitric acid to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, controlling the molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid to be 1:1.15, instantly mixing and contacting two streams of liquid in the microchannel reactor at 55 ℃ to react, controlling the discharge flow through a needle valve at a discharge outlet, controlling the reaction pressure of the microchannel to be 0.3MPa, conveying the reaction liquid to ice water, filtering, washing with the ice water, and drying in vacuum to obtain the 2-nitro-4-sulfonylmethyl toluene. And changing the residence time of the reaction liquid by serially connecting microchannel reactors for 1.0-3.0 min. The conversion and purity of 2-nitro-4-sulfonylmethyltoluene are shown in Table 2 and FIG. 4.

TABLE 3 influence of microchannel residence time on the synthesis of 2-nitro-4-sulfonylmethyltoluenes

t/min	1.0	1.5	2.0	2.5	3.0
						Conversion rate%	95.34	98.05	99.21	99.25	99.33
Purity%	96.02	98.34	99.35	99.28	99.31

Analysis data shows that the conversion rate of the 2-nitro-4-sulfonyl methyl toluene tends to increase and the purity tends to be stable with the increase of the residence time of the reaction liquid. When t is more than or equal to 2min, the conversion rate and the purity both reach more than 99 percent and tend to be stable.

Example 4:

(1) a solution of p-methylsulfonyltoluenesulfuric acid was prepared in the same manner as in example 2.

(2) The method comprises the steps of respectively conveying a p-methylsulfonyl toluene sulfuric acid solution and fuming nitric acid to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, enabling reaction liquid to stay for 2min, controlling the molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid, instantly mixing and contacting two streams of liquid in the microchannel reactor at 55 ℃ to react, controlling discharge flow through a needle valve at a discharge port, controlling the reaction pressure of the microchannel to be 0.3MPa, conveying the reaction liquid to ice water, filtering, washing the ice water, and drying in vacuum to obtain the 2-nitro-4-sulfonylmethyl toluene. The molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid is 1: 1.0-1.2. The conversion and purity of 2-nitro-4-sulfonylmethyltoluene are shown in Table 3 and FIG. 5.

TABLE 4 influence on the molar ratio of methylsulfonyltoluene to nitric acid on the synthesis of 2-nitro-4-sulfonylmethyltoluene

Molar ratio of	1:1.0	1:1.05	1:1.10	1:1.15	1:1.20
						Conversion rate%	94.84	97.58	99.27	99.3	99.22
Purity%	95.15	97.81	99.36	99.4	99.41

Analysis data shows that the conversion rate of the 2-nitro-4-sulfonyl methyl toluene tends to increase and the purity tends to be stable with the increase of the amount of fuming nitric acid. When the molar ratio of the p-methylsulfonyltoluene to the fuming nitric acid is 1:1.15, the conversion rate reaches 99.4 percent; when the amount of nitric acid is continuously increased, the conversion rate tends to be stable.

Example 5:

(1) a solution of p-methylsulfonyltoluenesulfuric acid was prepared in the same manner as in example 1.

(2) The method comprises the steps of respectively conveying a p-methylsulfonyl toluene sulfuric acid solution and fuming nitric acid to two inlets of a microchannel reactor through an advection pump with accurately controlled flow, enabling reaction liquid to stay for 2min, controlling the molar ratio of the p-methylsulfonyl toluene to the fuming nitric acid to be 1:1.15, instantly mixing and contacting two streams of liquid in the microchannel reactor at 50 ℃ to react, controlling discharge flow through a needle valve at a discharge port, controlling reaction pressure of a microchannel, conveying the reaction liquid to ice water, filtering, washing the ice water, and drying in vacuum to obtain the 2-nitro-4-sulfonylmethyl toluene. The micro-channel reaction pressure is 0.1 MPa-0.5 MPa. The conversion and purity of 2-nitro-4-sulfonylmethyltoluene are shown in Table 5 and FIG. 6.

TABLE 5 Effect of Microchannel pressure on 2-Nitro-4-sulfonylmethyltoluene Synthesis

P/Mpa	0.1	0.2	0.3	0.4	0.5
						Conversion rate%	99.14	99.18	99.21	99.29	99.25
Purity%	99.20	99.21	99.31	99.34	99.31

Analysis data shows that with the increase of the reaction pressure of the microchannel, the reaction conversion rate and the material purity have smaller growth tendency, and the whole body tends to be stable.

The above examples are only for illustrating the technical concept and features of the present invention, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.