CN110054566A - The method of mesitylene continuous nitrification production 2,4,6- trimethyl nitrobenzene - Google Patents

Abstract

The invention discloses a method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene. The method is as follows: mesitylene, sulfuric acid, nitric acid and dichloroethane are continuously fed in proportion by a pump through a flowmeter The nitrification reaction is carried out in three-tank series-tank type continuous nitrification reaction, and the nitrification liquid in the 3# nitrification kettle is continuously separated to obtain waste acid and acid nitrification, and part of the waste acid in the lower layer is recycled back to the 1# nitrification kettle. The upper layer of acid nitrate is neutralized, washed with water, solvent recovered, and distilled to obtain the solvent dichloroethane and the product 2,4,6-trimethylnitrobenzene, and the dichloroethane is recycled and applied. The invention has the following advantages: 1. The method is simple, the device investment is low, and the labor intensity is low; 2. The process parameters are stable, the raw material conversion rate and product yield are stable; 3. The nitrification waste acid can be recycled and applied, the production cost is reduced, and clean 4. Due to the small change of process conditions, it is conducive to safe production and easy to realize automatic control.

Description

Method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene

technical field

The invention relates to the technical field of organic synthesis, in particular to a method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene.

Background technique

Mesitylene (1,3,5-trimethylbenzene) can be nitrified to obtain 2,4,6-trimethylnitrobenzene, and then reduced to obtain 2-amino-mesitylene (also known as mesitylene). 2-amino-mesitylene is an intermediate of weakly acidic and reactive dyes. Dyes synthesized with it, such as weakly acidic brilliant blue RAW, reactive emerald green, reactive brilliant blue, etc., have bright colors and good leveling properties, and can be used for The dyeing of wool, silk and polyamide fiber fabrics can be dyed in a single color or with other weak acid dyes.

At present, the domestic production of 2,4,6-trimethylnitrobenzene adopts the traditional batch nitrification method, that is, sulfuric acid, nitric acid and water are mixed into mixed acid, and then nitrified with mesitylene at a temperature below 10 °C, and the obtained product is left to stand for fractionation. layer, let go of the waste acid, and then wash with water and neutralize to obtain 2,4,6-trimethylnitrobenzene. The batch nitrification method adopts kettle type batch production, the reaction speed is slow, the process is not easy to control, the output is low, the product yield is low, the waste acid is difficult to handle and utilize, and the waste of resources is serious.

Therefore, the pilot-scale research on the method of continuous nitration of mesitylene to produce 2,4,6-trimethylnitrobenzene is carried out, which will improve the technical level of the 2,4,6-trimethylnitrobenzene production unit and achieve clean , Automatic production is of great significance.

SUMMARY OF THE INVENTION

The purpose of this invention is to solve the above-mentioned problems, and the method for the continuous nitration of mesitylene that proposes produces 2,4,6-trimethylnitrobenzene.

In order to achieve the above purpose, the present invention discloses a method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene, and the method is as follows:

Mesitylene, sulfuric acid, nitric acid, and dichloroethane are continuously fed in proportion by a pump through a flow meter to carry out a three-tank series-tank continuous nitrification reaction, and the nitrification liquid is continuously separated in the 3# nitrification tank to obtain waste acid and acid nitrification. The lower part of the waste acid is recycled back to the 1# nitrification kettle, and the rest of the waste acid is recycled after extraction and concentration. 6-Trimethylnitrobenzene and dichloroethane are recycled.

Preferably, the mass fraction of mesitylene is 99.0%;

The mass fraction of sulfuric acid is 98%;

The mass fraction of nitric acid is 98%;

The mass fraction of dichloroethane is 99.0%;

The mass fraction of liquid caustic soda is 8%.

The mechanism of nitrification reaction is as follows:

First, nitric acid reacts with sulfuric acid to generate nitric acid hydrogen ion and negative hydrogen sulfate, and then the nitrate hydrogen ion is decomposed into water and NO ₂ ⁺ nitroxyl cation, and NO ₂ ⁺ nitroxyl cation reacts with mesitylene to form a cation complex , and then the complex decomposes to obtain nitrates and hydrogen ions, and hydrogen ions and hydrogen sulfate are combined to form sulfuric acid, and the reaction formula is:

During the reaction process, dinitration may also occur, and the reaction formula is:

Compared with the traditional preparation process, the present invention has the following advantages:

1. The method is simple, the device investment is low, and the labor intensity is low;

2. The process parameters are stable, the raw material conversion rate and product yield are stable;

3. The nitrification waste acid can be recycled, the production cost is reduced, and clean production can be realized;

4. Due to the small changes in process conditions, the workers are easy to operate, which is conducive to safe production and easy to achieve automatic control.

Description of drawings

Fig. 1 is the method flow chart of the continuous nitration of mesitylene proposed by the present invention to produce 2,4,6-trimethylnitrobenzene.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

Example 1

Referring to Fig. 1, continuous feeding to 1# nitrification kettle and waste acid extraction kettle, wherein mesitylene 140L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), sulfuric acid 48.4L/h, nitric acid 46.3L /h, dichloroethane 70L/h, sulfuric acid, nitric acid, dichloroethane are all put into 1# nitrification kettle, control different temperatures to carry out nitrification reaction, other processing steps are carried out according to the method shown in Figure 1, and the nitrification temperature is investigated by the temperature The effect of the reaction is shown in Table 1.1.

Table 1.1 Influence of temperature on nitrification reaction

serial number temperature(℃) Conversion rate(%) Yield (%) 1 -15～-10 95.0 85.6 2 -10～-5 97.2 90.8 3 -5～0 98.8 93.7 4 0～5 100 94.3 5 5 to 10 100 93.8 6 10～15 100 93.7 7 15～20 100 89.6 8 20～25 100 85.2 9 25～30 100 82.7

Since there is a methyl group on each of the 1, 3, and 5 positions of the mesitylene ring, and the methyl group is an electron donating group, the increase in the electron cloud density on the benzene ring facilitates the nitration reaction. When the temperature is high, the reaction speed will be accelerated, and the electron cloud density on the benzene ring will increase, and side reactions will easily occur, resulting in dinitro compounds, the content of which can reach 2.5% to 3.5%. Therefore, attention should be paid to controlling the temperature during the nitrification process. The data in Table 1.1 show that the optimum temperature for the nitrification reaction is controlled between 0 and 5 °C.

Embodiment 2

Referring to Fig. 1, continuous feeding to 1# nitrification kettle and waste acid extraction kettle, wherein mesitylene 140L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), nitric acid 46.3L/h, dichloroethane 70L/h of alkane, sulfuric acid, nitric acid, and dichloroethane are all put into 1# nitrification kettle, and the temperature is controlled between 0 and 5 °C. Other processing steps are carried out according to the method shown in Figure 1, and the effect of sulfuric acid effective concentration (φ) on the nitrification reaction is investigated by changing the sulfuric acid feed amount, and the results are shown in Table 1.2.

Table 1.2 The effect of the effective concentration of sulfuric acid (φ) on the nitrification reaction

serial number Sulfuric acid feed amount (L/h) Effective concentration of sulfuric acid (φ) Conversion rate(%) Yield (%) 1 40.0 65% 97.2 87.8 2 41.9 66% 98.8 90.7 3 43.9 67% 99.6 92.5 4 46.1 68% 100 93.9 5 48.4 69% 100 94.3 6 50.8 70% 100 93.8 7 53.5 71% 100 93.1 8 56.3 72% 100 92.7 9 59.4 73% 100 90.5

There are two functions of sulfuric acid in mixed acid:

1. Sulfuric acid is an activator, it dissociates nitric acid into NO ⁺ ₂ nitroxyl cation, and NO ⁺ ₂ nitroxyl cation is the strongest activating nitrifying agent;

2. Sulfuric acid is a strong dehydrating agent. It can combine with the water generated by the nitrification reaction to form a hydrate of sulfuric acid, so that the nitric acid is not diluted by water, and even the nitric acid does not contain water, so as to avoid acid ionization of nitric acid and improve the utilization of nitric acid. Rate.

It can be seen from Table 1.2 that within a certain range, the effective concentration of sulfuric acid (φ) increases, and the conversion and yield increase and become stable, but when the effective concentration of sulfuric acid (φ) is increased, the yield begins to decline. This is due to The effective concentration of sulfuric acid (φ) increases, and the side reaction of dinitration occurs. The data in Table 1.2 shows that the effective concentration of sulfuric acid (φ) suitable for the nitrification reaction is 69%.

Embodiment 3

Referring to Figure 1, continuous feeding is made to 1# nitrification kettle and waste acid extraction kettle, wherein mesitylene 140L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), sulfuric acid 48.4L/h, dichloroethane 70L/h of alkane, sulfuric acid, nitric acid, and dichloroethane are all put into 1# nitrification kettle, and the temperature is controlled between 0 and 5 °C. Other processing steps are carried out according to the method shown in Figure 1. The effect of nitric acid ratio on the nitrification reaction is shown in Table 1.3.

Table 1.3 Effect of nitric acid ratio on nitrification reaction

serial number Nitric acid feed amount (L/h) Nitric acid ratio Conversion rate(%) Yield (%) 1 42.9 1.00 92.1 82.4 2 43.7 1.02 98.4 87.5 3 44.6 1.04 99.6 91.1 4 45.4 1.06 99.9 93.8 5 46.3 1.08 100 94.2 6 47.1 1.10 100 93.9 7 48.0 1.12 100 93.6 8 48.9 1.14 100 92.6 9 49.7 1.16 100 90.5

The theoretical value of the nitric acid ratio in the mesitylene nitration reaction is 1.00, and the nitric acid ratio in the actual reaction is greater than the theoretical value. When the nitric acid ratio increases, the number of nitroxyl cations also increases accordingly, and the reaction speed is accelerated, but the dinitration side reaction occurs when the nitric acid ratio increases to a certain extent. It can be seen from Table 1.3 that within a certain range, the ratio of nitric acid increases, and the conversion rate and yield increase, but if the ratio of nitric acid is increased again, the yield begins to decline. The data indicated that the suitable ratio of nitric acid for nitrification reaction was 1.08.

Embodiment 4

Referring to Fig. 1, continuous feeding to 1# nitrification kettle and waste acid extraction kettle, wherein mesitylene 140L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), sulfuric acid 48.4L/h, nitric acid 46.3L /h, sulfuric acid, nitric acid, and dichloroethane are all put into 1# nitrification kettle, and the temperature is controlled between 0 and 5 °C. Other processing steps are carried out as shown in Figure 1. The effect of solvent ratio on the nitration reaction was investigated, and the results are shown in Table 1.4.

Table 1.4 Effect of solvent ratio on nitration reaction

Since the freezing point of 2,4,6-trimethylnitrobenzene is between 41 and 44°C and the temperature is between 0 and 5°C, when no solvent is added, the reaction system is a liquid-solid heterogeneous system, which cannot be guaranteed. sufficiency of the response. Adding dichloroethane solvent to the reaction system can increase the mutual solubility of the system, make the reactants fully contact, and achieve better mass transfer conditions. It can be seen from Table 1.4 that within a certain range, the solvent ratio increases, the conversion rate and The yields are all improved. When the solvent ratio reaches more than 0.5, the conversion rate and yield tend to be stable. If the solvent ratio increases, it will inevitably lead to a decrease in equipment utilization and an increase in solvent recovery costs. The data in Table 1.5 show that the suitable solvent ratio for the nitration reaction is 0.5.

Embodiment 5

1, continuous feeding to 1# nitrification still and waste acid extraction still, wherein mesitylene 140L/h, sulfuric acid 48.4L/h, nitric acid 46.3L/h, dichloroethane 70L/h, sulfuric acid, nitric acid, All the dichloroethane was put into the 1# nitrification kettle, and the temperature was controlled between 0 and 5 °C. Other processing steps were carried out as shown in Figure 1. The effect of toluene feed ratio on the nitration reaction is shown in Table 1.5.

Table 1.5 Influence of mesitylene feed ratio on nitration reaction

Mesitylene is added to the waste acid extraction kettle as an extractant for two purposes: one is to extract nitrates in waste acid to improve yield and reduce consumption; In the denitration operation of waste acid, the waste acid is directly concentrated. The experimental data show that changing the feed ratio of mesitylene has little effect on the conversion rate, but has a certain effect on the yield of the product, mainly because the addition of mesitylene into the waste acid extraction kettle can play an extraction role, and the waste acid can be extracted. The dissolved organics and nitric acid are extracted out. However, after the feed ratio of mesitylene in the waste acid extraction kettle is increased to a certain extent, the yield does not increase but decreases. This is because the activity of mesitylene is very high. When the nitric acid content in the waste acid is not high, the nitrification ability Insufficient, mesitylene will undergo resinization reaction, showing that the waste acid is black and red, and the waste acid is black and red because the complex (C9H12) (HNSO5)2(H2SO4)3 is formed, which can be seen from the structure of the complex. , the complex is composed of one part of mesitylene, two parts of nitroso sulfuric acid, and three parts of sulfuric acid. Therefore, the amount of mesitylene added in the waste acid extraction kettle should not only meet the extraction amount, but also not be large, resulting in waste acid The nitrification capacity of the extraction kettle is insufficient. The data in Table 1.5 shows that the suitable feeding ratio of mesitylene is: 92.5% for the 1# nitrification kettle and 7.5% for the extraction kettle.

Embodiment 6

Referring to Figure 1, continuous feeding to 1# nitrification kettle and waste acid extraction kettle, wherein mesitylene 140 L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), sulfuric acid 48.4 L/h, nitric acid 46.3 L/h, dichloroethane 70L/h, sulfuric acid, nitric acid, and dichloroethane are all put into 1# nitrification kettle, and the temperature is controlled between 0 and 5 °C. Other processing steps are carried out by the method shown in Figure 1, by changing the 3# nitrification kettle to the 1# nitrification kettle waste acid circulation volume to adjust the modulus, investigate the influence of the modulus on the nitrification reaction, the results are shown in Table 1.6.

Table 1.6 Influence of modulus on nitrification reaction

serial number modulus Conversion rate(%) Yield (%) 1 0 76.5 75.1 2 0.5 84.2 80.2 3 1.0 92.6 86.7 4 1.5 99.2 92.6 5 2.0 99.6 93.3 6 2.5 100 93.8 7 3.0 100 94.2 8 3.5 99.6 93.8 9 4.0 99.2 92.3

During the nitration reaction, the modulus increases, the reaction speed increases, and the oxidation side reaction decreases. Due to the different distribution coefficients of nitric acid in the waste acid and organic phase, the amount of nitric acid in the waste acid and organic phase is very different. Nitric acid in acid is used for nitrification, while nitric acid in nitrate is used for oxidation, the waste acid in the nitrification kettle increases, and the organic phase decreases. Within a certain range, the modulus increases, and the conversion rate and yield increase, but the modulus is too large , the oxidation side reaction will also increase, and the conversion rate and yield will decrease accordingly. The data in Table 1.6 show that the appropriate modulus of the nitrification reaction is 3.0.

Embodiment 7

To 1# nitrification kettle and waste acid extraction kettle continuous feeding, wherein mesitylene 140L/h (1# nitrification kettle 92.5%, waste acid extraction kettle 7.5%), sulfuric acid 48.4L/h, nitric acid 46.3L/h, two Ethyl chloride 70L/h, sulfuric acid, nitric acid, and dichloroethane are all put into 1# nitrification kettle, and the temperature is controlled between 0 and 5 °C. Other treatment steps were carried out according to the method shown in Figure 1, and the effect of the recycling of waste acid on the nitrification reaction was investigated. The results are shown in Table 1.7.

Table 1.7 Influence of waste acid recycling on nitrification reaction

serial number Cycle time Conversion rate(%) Yield (%) 1 (3) 100 94.2 2 6 100 94.2 3 9 100 94.1 4 12 100 94.0 5 15 100 94.2 6 18 100 94.2 7 twenty one 100 94.0 8 twenty four 100 94.1 9 27 100 94.2

Mixed acid nitration will produce a large amount of waste acid. If it is directly discharged, it will not only increase the consumption of raw materials, increase the production cost, but also seriously pollute the environment.

In the present invention, adopt the waste acid after concentration to replace fresh sulfuric acid to carry out nitrification reaction. Seen from the data in Table 1.7 that the recycling of waste acid has little effect on conversion rate and yield, and thus recycling of waste acid is feasible.

In the embodiment of the present invention 1-7, the mass fraction of raw material is as follows:

The mass fraction of mesitylene is 99.0%;

The mass fraction of sulfuric acid is 98%;

The mass fraction of nitric acid is 98%;

The mass fraction of dichloroethane is 99.0%;

The mass fraction of liquid caustic soda is 8%.

The main equipment of the experiment is shown in Table 2.

Table 2 List of equipment specifications and models

The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the claims linguistically, wherein reference to elements in the singular is not intended to be used unless specifically stated otherwise. Means "there is only one", but "one or more". The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term "some" refers to one or more. Elements of the various aspects described throughout this disclosure are all structural and functional equivalents now or hereafter known to those of ordinary skill in the art, which are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be contributed to the public, whether or not such disclosure is expressly recited in the claims. No claim element should be construed as means-plus-function unless the element is explicitly recited using the phrase "means for."

Claims (8)

1. the method for continuous nitration of mesitylene to produce 2,4,6-trimethylnitrobenzene, is characterized in that, the method is as follows: Mesitylene, sulfuric acid, nitric acid and ethylene dichloride are continuously fed in proportion by the pump and flow meter, and the continuous nitrification reaction of three kettles in series is carried out. Part of the waste acid in the lower layer is recycled back to the 1# nitrification kettle, and the rest of the waste acid is extracted and concentrated to be recycled and applied. 6-Trimethylnitrobenzene and dichloroethane are recycled. 2. the method for continuous nitration of mesitylene according to claim 1 to produce 2,4,6-trimethylnitrobenzene, is characterized in that: The mass fraction of mesitylene is 99.0%; The mass fraction of sulfuric acid is 98%; The mass fraction of nitric acid is 98%; The mass fraction of dichloroethane is 99.0%; The mass fraction of liquid caustic soda is 8%. 3. The method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene according to claim 1, wherein the nitration reaction temperature is 0-5°C. The method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene according to claim 1, wherein the effective concentration (φ) of sulfuric acid in the nitration reaction is 69%. 5. The method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene according to claim 1, wherein the nitric acid ratio of the nitration reaction is 1.08. 6. The method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene according to claim 1, wherein the solvent ratio of the nitration reaction is 0.5. 7. mesitylene continuous nitration according to claim 1 produces the method for 2,4,6-trimethylnitrobenzene, the feed ratio of described mesitylene is: 1# nitrification kettle 92.5%, extraction kettle 7.5%. 8. The method for producing 2,4,6-trimethylnitrobenzene by continuous nitration of mesitylene according to claim 1, wherein the modulus of the nitration reaction is 3.0.