CN114262285B - Method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide - Google Patents

Abstract

The invention discloses a method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide. The sulfur trioxide solution is added dropwise to p-toluidine solution to perform sulfonation reaction to obtain 4-aminotoluene-3-sulfonic acid; The sulfur trioxide solution is obtained by dissolving sulfur trioxide in an organic solvent. The present invention uses an organic solvent to dilute sulfur trioxide, and adopts the method of dripping, which greatly suppresses side reactions such as polymerization of sulfur trioxide and excessive sulfonation, reduces the viscosity of the reaction system, and prevents sulfur trioxide from Curing under low temperature conditions; thereby realizing the direct introduction of sulfur trioxide as sulfonating agent in the preparation process of 4-aminotoluene-3-sulfonic acid, the sulfonation reaction does not generate water, the consumption of sulfur trioxide is close to the theoretical amount, and the reaction The temperature is mild, the energy consumption is low, the use of a large amount of high boiling point solvents is avoided, the reaction solvent can be used continuously, and the reaction is rapid, the equipment is small, the three wastes are less, and the economy is reasonable.

Description

A kind of method that sulfur trioxide prepares 4-aminotoluene-3-sulfonic acid

technical field

The invention relates to a preparation method of a pigment intermediate, in particular to a method for preparing 4-aminotoluene-3-sulfonic acid (4B acid) from sulfur trioxide.

Background technique

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and is not necessarily taken as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

4B acid is a white or beige powder crystal. 4B acid can be diazotized with nitrite in dilute acid. It has general amine compatibility and is an important intermediate for the synthesis of various pigments and reactive dyes. Widely used in paints, coatings, color inks, rubber and plastic coloring, etc.

In recent years, due to the successive closure, conversion or transfer of foreign pigment and intermediate production plants, especially the closure of some production facilities in developed countries due to pollution problems, the demand for my country's PR57 pigment and 4B acid products has increased significantly. At present, the domestic production scale is relatively small, the technology is relatively backward, and there are still new and expanded 4B acid equipments being put into operation one after another, which makes the production capacity of 4B acid grow too fast, resulting in relatively insufficient investment in process technology research and equipment improvement. , limited to satisfy existing equipment and technology. Generally speaking, in the production of 4B acid in China, there are still low yields, troublesome separation operations, many control points, large differences between production batches, and serious wastes.

The methods for synthesizing 4B acid mainly include concentrated sulfuric acid salt-forming rearrangement method (direct baking method and solvent method), fuming sulfuric acid method, etc. In the patent CN 101747236 A, the stirring reaction is carried out at 210-220°C for 2-5 hours, and the crude product needs to undergo alkali dissolution, decolorization and acid precipitation. The inventor found that the process is relatively backward, the operating conditions are poor, the safety is low, the environmental pollution is serious, and the product yield is low, and the product needs to be refined and post-treated. In patent CN 102718687 A, p-toluidine and concentrated sulfuric acid are used in a sulfonation reaction kettle, heated to 180°C with heat transfer oil, and then sulfonation reaction is carried out. This process also requires alkali dissolution, decolorization, and acid analysis. The inventor found that the process is complicated to operate, the product yield is not clear, the amount of three wastes in the post-treatment process is relatively large, and a certain amount of iso-4B acid is generated. In patent CN 101143841 A, p-toluidine is dissolved in an organic solvent, concentrated sulfuric acid is added under stirring, and then the temperature is raised to 180-190° C. for sulfonation reaction. During the reaction process, the water produced by the reaction needs to be continuously distilled out, and after the reaction, the solvent is recovered by distillation under reduced pressure. The inventors have found that the process uses concentrated sulfuric acid as a sulfonating agent and uses a high-boiling solvent, which requires high energy consumption and requires purification of the product. Patent DE3401572 reported the preparation of 4B acid by sulfonation reaction with oleum at 65°C. The inventors have found that the process requires more sulfuric acid and the cost of raw materials is high.

In the existing synthetic method, sulfuric acid is used as the sulfonating agent, and whether it is produced by the solvent method or the baking method, the reaction temperature is relatively high, or a high boiling point solvent needs to be used. The reaction process requires dehydration and transposition, and the crude product 4B acid needs to undergo decolorization, filtration, acidification, dehydration, drying and other processes to obtain high-purity 4B acid. There is a certain amount of tar or oxide in the reaction process or purification process, which is easy to oxidize the amino group, and the product turns yellow, which affects the product quality.

To sum up, the traditional 4B acid production process mainly adopts sulfuric acid or oleum sulfonation method, which has problems such as large resource consumption, many side reactions, and large amount of three wastes, making the whole process uneconomical and environmentally friendly.

Contents of the invention

In order to solve the deficiencies in the prior art, the purpose of this invention is to provide a method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide, which solves the problems of high production cost, large risk factor, low product quality and The three wastes are large and other problems.

In order to achieve the above object, the technical solution of the present invention is:

A method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide, adding sulfur trioxide solution dropwise to p-toluidine solution to carry out sulfonation reaction to obtain 4-aminotoluene-3-sulfonic acid; the sulfur trioxide The solution is obtained by dissolving sulfur trioxide in an organic solvent.

Although sulfur trioxide is an excellent sulfonating agent, in the production process of 4B acid, sulfur trioxide has not yet been used due to difficulties in feeding due to the introduction of sulfur trioxide, high viscosity of the system, and side reactions caused by sulfur trioxide. A precedent for the preparation of 4B acid.

In order to solve the problems of difficult feeding caused by adding sulfur trioxide, high viscosity of the system, and side reactions caused by sulfur trioxide, the present invention uses organic solvents to dilute sulfur trioxide, and adopts the method of dripping, which greatly suppresses the production of sulfur trioxide. side reactions such as polymerization and excessive sulfonation, and reduce the viscosity of the reaction system. At the same time, it can prevent sulfur trioxide from solidifying at low temperature.

When the solvent of the sulfonation reaction system is one of dichloroethane, dichloromethane, tetrachloroethane, and petroleum ether, the solubility of the raw material and the product in the solvent is different. Among them, the solubility of the raw material is large, while the product is slightly soluble or even Insoluble, the product can be isolated by simple filtration.

The sulfonation reaction temperature can generate 4B acid at a temperature of 0-70°C. When the temperature is lower, the reaction rate is slower, the corresponding reaction time is longer, and the reaction selectivity is higher; when the reaction temperature is higher, the reaction rate is accelerated and the reaction time is shortened. , the product selectivity is somewhat reduced.

The beneficial effects of the present invention are:

(1) The present invention selects the solution of sulfur trioxide/organic solvent as the sulfonation reagent, and its main advantage is that it can directly generate sulfonic acid groups without generating water, and the dosage can be close to the theoretical amount, and the reaction cycle is short, the three wastes are few, and it is economical and environmentally friendly .

(2) Because sulfur trioxide possesses extremely strong electrophilic substitution ability, especially for the p-toluidine raw material of the present invention, sulfur trioxide is very high for the reactivity of amino ortho-position, only needs to adopt lower temperature, close to 1 Equivalent ratio of raw materials can make the product yield reach more than 98%, and the product purity reach 98.5%. Compared with the existing sulfuric acid sulfonation process, the reaction temperature is milder, and the energy consumption is greatly reduced; the product 4B is acid-insoluble or slightly soluble in the selected organic solvent of the present invention, and the reaction solution is directly filtered to obtain the product, and the filtrate can be applied to sulfonation without treatment. The chemical reaction can realize the continuous application of the reaction solvent, which reduces the environmental pollution and the production cost.

(3) In order to realize accurate feeding of sulfur trioxide, the present invention dissolves liquid sulfur trioxide in an organic solvent to prevent it from solidifying under low temperature conditions, which is beneficial to realize pipeline transportation and precise pumping. In addition, since the sulfur trioxide is diluted by the organic solvent and slowly added dropwise, side reactions such as the polymerization of sulfur trioxide and excessive sulfonation are greatly suppressed, and the viscosity of the reaction system is reduced.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is the nuclear magnetic spectrum of the 4B acid prepared by the embodiment of the present invention 1;

Figure 2 is a liquid chromatographic analysis chart of 4B acid prepared in Example 1 of the present invention.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In view of the problems of large resource consumption, many side reactions, and large amount of three wastes in the traditional 4B acid production process, the present invention proposes a method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide.

A typical embodiment of the present invention provides a method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide, in which sulfur trioxide solution is added dropwise to p-toluidine solution for sulfonation reaction to obtain 4-aminotoluene -3-sulfonic acid; the sulfur trioxide solution is obtained by dissolving sulfur trioxide in an organic solvent.

The invention uses an organic solvent to dilute the sulfur trioxide, and adopts the method of dropwise addition, which greatly suppresses side reactions such as the polymerization of the sulfur trioxide and excessive sulfonation, and reduces the viscosity of the reaction system. At the same time, it can prevent sulfur trioxide from solidifying at low temperature.

In some examples of this embodiment, the solvent of the sulfonation reaction system is dichloroethane, dichloromethane, tetrachloroethane or petroleum ether. When selecting these solvents, raw materials and products have different solubility in solvents, and the separation of products can be realized by simple filtration. When the solvent of the sulfonation reaction system is dichloroethane or dichloromethane, the products can be better separated.

In some examples of this embodiment, the temperature of the sulfonation reaction is 0-70°C. The main product that can guarantee to obtain under this reaction temperature is 4B acid, and when temperature is lower, reaction rate is slower, and corresponding reaction time is longer, and reaction selectivity is higher; When reaction temperature is higher, reaction rate accelerates, and reaction time shortens, The product selectivity is somewhat reduced. When the temperature of the sulfonation reaction is 30-60°C, both the selectivity of the reaction and the rate of the reaction can be guaranteed.

In some examples of this embodiment, during the dropwise addition of the sulfur trioxide solution, the temperature of the system is kept at the temperature of the sulfonation reaction. It is ensured that the sulfonation reaction is carried out during the dropwise addition of the sulfur trioxide solution, which greatly suppresses side reactions such as the polymerization of sulfur trioxide and excessive sulfonation, and reduces the viscosity of the reaction system. To ensure that the reaction proceeds.

In some examples of this embodiment, the time for adding the sulfur trioxide solution dropwise is 2-6 hours. Slowly adding the sulfur trioxide solution dropwise can ensure that the added sulfur trioxide reacts completely in the reaction system, thereby further inhibiting side reactions such as polymerization of sulfur trioxide and excessive sulfonation. When the time for dropping sulfur trioxide solution is 3-5 hours, the effect is better.

In some examples of this embodiment, the reaction is continued for 1-3 hours after the dropwise addition. It can ensure the complete sulfonation reaction.

In some examples of this embodiment, the molar ratio of sulfur trioxide to p-toluidine is 0.95˜1.2:1. It can ensure the complete reaction of materials. When the molar ratio of sulfur trioxide and p-toluidine is 1-1.1:1, complete reaction of p-toluidine can be ensured.

In some examples of this embodiment, the mass ratio of p-toluidine to the organic solvent in the p-toluidine solution is 1:2-5.

In some examples of this embodiment, the mass ratio of sulfur trioxide to the organic solvent is 1:2-5.

In some examples of this embodiment, the steps include:

Adding p-toluidine to an organic solvent for dissolving to prepare a p-toluidine solution;

Sulfur trioxide is added into an organic solvent to dissolve and prepare a sulfur trioxide solution;

Heat the p-toluidine solution to the sulfonation reaction temperature, then add the sulfur trioxide solution dropwise, continue the sulfonation reaction after the dropwise addition, and cool and filter to obtain 4-aminotoluene-3-sulfonic acid after the sulfonation reaction is completed.

In order to enable those skilled in the art to understand the technical solution of the present invention more clearly, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

Example 1

Dissolve 21.4g of p-toluidine in 42.8g of dichloroethane, stir well until the p-toluidine is completely dissolved, then add it into a three-necked flask with stirring, and slowly raise the temperature to 30°C. Dissolve 16g of sulfur trioxide in 42.8g of dichloroethane. After the temperature in the reaction flask reaches the set temperature, slowly add the sulfur trioxide solution to the p-toluidine solution dropwise for 3 hours. After the addition of sulfur trioxide, the reaction was continued for 1 h, cooled and filtered to obtain 37.13 g of 4B acid with a yield of 99.2% and a purity of 99.5%, as shown in Figures 1-2.

Wherein, the result data in Fig. 2 are shown in the following table.

Table LC data

Example 2

Dissolve 32.1g of p-toluidine in 100g of tetrachloroethane, stir well until the p-toluidine is completely dissolved, then add it into a three-necked flask with stirring, and control the system temperature to 0°C. Dissolve 25.2g of sulfur trioxide in 100g of tetrachloroethane. After the temperature in the reaction flask reaches the set temperature, slowly add the sulfur trioxide solution to the p-toluidine solution dropwise for 6 hours. After sulfur trioxide was added dropwise, the reaction was continued for 3 hours, cooled and filtered to obtain 55.48 g of 4B acid with a yield of 98.8% and a purity of 99.2%.

Example 3

Dissolve 21.4g of p-toluidine in 100g of dichloromethane, stir well until the p-toluidine is completely dissolved, then add it into a stirring three-necked flask, and slowly raise the temperature to 60°C. Dissolve 17.6g of sulfur trioxide in 100g of dichloromethane. After the temperature in the reaction flask reaches the set temperature, slowly add the sulfur trioxide solution to the p-toluidine solution dropwise for 5 hours. After the sulfur trioxide was added dropwise, the reaction was continued for 2 hours, cooled and filtered to obtain 37.10 g of 4B acid with a yield of 99.1% and a purity of 99.6%.

Example 4

Dissolve 21.4g of p-toluidine in 107g of petroleum ether, stir well until the p-toluidine is completely dissolved, then add it into a stirring three-necked flask, and slowly raise the temperature to 50°C. Dissolve 15.2g of sulfur trioxide in 107g of petroleum ether. After the temperature in the reaction flask reaches the set temperature, slowly add the sulfur trioxide solution to the p-toluidine solution for 3 hours. After the sulfur trioxide was added dropwise, the reaction was continued for 2 hours, cooled and filtered to obtain 37.02 g of 4B acid with a yield of 98.9% and a purity of 99.0%.

Example 5

Dissolve 21.4g of p-toluidine in 100g of dichloroethane mother liquor, stir well until p-toluidine is completely dissolved, then add it into a three-necked flask with stirring, and slowly raise the temperature to 70°C. Dissolve 19.2g of sulfur trioxide in 100g of dichloroethane mother liquor. After the temperature in the reaction flask reaches the set temperature, slowly add the sulfur trioxide solution to the p-toluidine solution dropwise for 2 hours. After the sulfur trioxide was added dropwise, the reaction was continued for 1 h, cooled and filtered to obtain 37.0 g of 4B acid with a yield of 98.8% and a purity of 99.1%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for preparing 4-aminotoluene-3-sulfonic acid by sulfur trioxide is characterized in that a sulfur trioxide solution is dropwise added into a p-toluidine solution for sulfonation reaction to obtain 4-aminotoluene-3-sulfonic acid; the sulfur trioxide solution is obtained by dissolving sulfur trioxide in an organic solvent;

the method comprises the following specific steps:

adding p-toluidine into an organic solvent to prepare a p-toluidine solution by dissolution;

adding sulfur trioxide into an organic solvent to dissolve to prepare a sulfur trioxide solution;

heating p-toluidine solution to sulfonation reaction temperature, dropwise adding sulfur trioxide solution, continuing sulfonation reaction after dropwise adding, cooling and filtering after sulfonation reaction is finished to obtain 4-aminotoluene-3-sulfonic acid;

the temperature of sulfonation reaction is 0-70 ℃;

the time for dropwise adding the sulfur trioxide solution is 2-6 hours;

the solvent of the sulfonation reaction system is dichloroethane, dichloromethane and tetrachloroethane;

the method comprises the steps of dissolving liquid sulfur trioxide in an organic solvent, adopting a slow dropwise adding mode, inhibiting polymerization of the sulfur trioxide and excessive sulfonation side reaction, reducing the viscosity of a reaction system, preventing the reaction system from solidifying under a low-temperature condition, and being beneficial to realizing pipeline transportation and accurate pumping.

2. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide as claimed in claim 1, wherein the solvent of the sulfonation reaction system is dichloroethane or dichloromethane.

3. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the temperature of the sulfonation reaction is 30 to 60 ℃.

4. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide as claimed in claim 1, wherein the temperature of the system is maintained at the temperature of sulfonation reaction during the dropping of the sulfur trioxide solution.

5. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the time for dropping the sulfur trioxide solution is 3 to 5 hours.

6. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the reaction is continued for 1 to 3 hours after the dropping.

7. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the molar ratio of sulfur trioxide to p-toluidine is 0.95-1.2:1.

8. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide as set forth in claim 7, wherein the molar ratio of sulfur trioxide to p-toluidine is 1 to 1.1:1.

9. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the mass ratio of para-toluidine to organic solvent in the para-toluidine solution is 1:2-5.

10. The method for preparing 4-aminotoluene-3-sulfonic acid from sulfur trioxide according to claim 1, characterized in that the mass ratio of sulfur trioxide to organic solvent is 1:2-5.

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