Preparation method of 2, 5-diaminotoluene and sulfate thereof

Abstract

The invention discloses a preparation method of 2, 5-diaminotoluene and sulfate thereof, and relates to the technical field of chemical synthesis. According to the invention, 2-methyl-4-nitro-5-chloroaniline is adopted as a raw material, 2, 5-diaminotoluene is synthesized with high selectivity through a two-step process of nitro catalytic hydrogenation reduction and catalytic hydrogenation dechlorination, and the prepared 2, 5-diaminotoluene is adopted as a raw material and is mixed with sulfuric acid for salt forming reaction, so that sulfate can be obtained. Through the two-step hydrogenation process, the yield of the 2, 5-diaminotoluene can be improved, and the reaction conditions can be optimized, so that the 2, 5-diaminotoluene is suitable for industrial production. In addition, the preparation method conforms to the green chemistry principle, and the environmental protection pressure and the wastewater treatment cost are greatly reduced. Specifically, the yield of the prepared 2, 5-diaminotoluene sulfate can reach 85% or above, and the purity of the prepared 2, 5-diaminotoluene sulfate is larger than 99.5%.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing 2,5-diaminotoluene and its sulfate. Background Technology

[0002] 2,5-Diaminotoluene, chemical formula C7H 10 N2, CAS number 90-70-5, is widely used in pharmaceutical intermediates, hair dyes, polymer materials, and membrane treatment. For example, 2,5-diaminotoluene can be used as an auxiliary agent to improve relevant membrane performance parameters and as an intermediate raw material in the synthesis of new pigments or additives in cosmetics. 2,5-Diaminotoluene sulfate, also known as 2-methyl-p-phenylenediamine sulfate, CAS number 615-50-9, is mainly used as an artificial electron donor in dye intermediates, organic synthesis, and photosensitive system I research. It is prepared by a salt-forming reaction between 2,5-diaminotoluene and sulfuric acid.

[0003] In existing technologies, the synthesis process of 2,5-diaminotoluene mainly includes: (1) Using m-toluidine as a raw material: 4-Nitro-m-Toluidine was prepared by acetylation of the amino group, followed by nitration and hydrolysis. Then, 2,5-Diaminotoluidine was prepared by hydrogenation. The reaction formula for the hydrogenation reaction is shown below: ; In this synthetic process, the synthesis of 4-nitro-m-toluidine suffers from unstable raw material prices, a long process flow, and a yield of only 86% for the product obtained by the hydrogenation reaction of 4-nitro-m-toluidine. The molar yield of 2,5-diaminotoluene sulfate from m-toluidine is 46%, which is too low to meet the needs of industrialization.

[0004] Furthermore, using m-toluidine as a starting material, a coupling compound is obtained through a self-diazotization-coupling reaction in a mixed solvent of isopropanol and acetic acid, followed by bond-breaking reduction under the catalysis of Zn-HCl to yield 2,5-diaminotoluene. However, this synthetic route still suffers from low yield, high raw material costs, and severe environmental pollution during the reaction process, making it unsuitable for industrial production.

[0005] (2) Using m-nitrotoluene as raw material: p-Nitrotoluidine was synthesized from m-nitrotoluene as a starting material, acetamide as an amination reagent, and potassium hydroxide and pyridine as promoters in dimethyl sulfoxide. 2,5-Diaminotoluene was then obtained via hydrogenation. This synthetic process requires large amounts of organic solvents and expensive chemicals, resulting in high production costs. Furthermore, the low yield of the intermediate p-nitrotoluidine negatively impacts the yield of the final product, 2,5-diaminotoluene.

[0006] (3) Using o-toluidine as a raw material: Using o-toluidine as a starting material, after protection with p-methylbenzoyl chloride, a coupling reaction was carried out with the diazonium salt of p-aminobenzenesulfonic acid to obtain a coupling compound. This compound was then reduced in the presence of sodium dithionite to yield 2,5-diaminotoluene. The specific synthetic route is shown below: ; This synthesis process is lengthy, involves numerous auxiliary materials during the reaction, increases preparation costs, and also poses a serious environmental pollution problem.

[0007] (4) Using 2-chloro-5-nitrotoluene as a raw material: Using 2-chloro-5-nitrotoluene as a starting material, p-nitro-o-toluidine was synthesized via ammonolysis, followed by hydrogenation to obtain 2,5-diaminotoluene. The specific synthetic route is shown below: ; However, the above-mentioned ammonia synthesis needs to be carried out under high temperature and high pressure conditions, which places high demands on process equipment and operation. In addition, the raw materials are not easy to obtain, making it difficult to industrialize.

[0008] (5) Using o-nitrotoluene as a raw material: Using o-nitrotoluene as a raw material, 2,2-dimethylazobenzene oxide is prepared by reduction reaction, followed by nitration to prepare 4-nitro-2,2-dimethylazobenzene oxide, which is then reduced to 2,5-diaminotoluene in the presence of SnCl2-HCl catalyst. This synthetic process also produces o-toluidine and other phenylhydrazine compounds, making product separation difficult and resulting in high production costs due to the large amount of catalyst required.

[0009] (6) Using 2,5-dinitrotoluene as a raw material: Using 2,5-dinitrotoluene as a raw material, water as a solvent, sodium acetate as a promoter, and selenium as a catalyst, CO was introduced into a reactor, and the reaction was carried out under high pressure and controlled temperature to obtain o-nitro-m-toluidine. Then, 2,5-diaminotoluene was obtained by hydrogenation. The specific synthesis process is shown below: ; The synthesis process has drawbacks such as the difficulty in obtaining 2,5-dinitrotoluene as a raw material, high catalyst cost, and stringent reaction process requirements.

[0010] (7) Using 2-aminoazotoluene as a raw material: 2,5-Diaminotoluene was synthesized from 2-aminoazotoluene via a catalytic cracking reaction in the presence of a catalyst and solvent. The synthetic route is shown below: Because the catalysts / reaction solvents used in this process are expensive and consumed in large quantities, this method has not yet been industrialized.

[0011] In addition, CN101659620A discloses a synthetic route using 2-methyl-4-nitroaniline as a raw material, magnetic magnesium aluminum hydrotalcite as a catalyst, and hydrazine hydrate as a reducing agent, reacting at 0-100℃ for 1-20 h, and then separating and purifying to obtain 2,5-diaminotoluene. The synthetic route is shown below: .

[0012] However, in the above synthetic route, the self-production cost of 2-methyl-4-nitro-5-chloroaniline is high, at about 70,000 yuan / ton. When using hydrazine hydrate as a catalyst, excessive hydrazine hydrate is required, which greatly increases the production cost. In addition, the reaction of hydrazine hydrate generates a large amount of gas that is prone to boiling violently, posing a safety hazard.

[0013] It is evident that existing technologies use various substances, including m-toluidine, 2-methyl-4-nitroaniline, and 3-methyl-4-nitroaniline, as raw materials to synthesize 2,5-diaminotoluene. However, there are no reports on the preparation of 2,5-diaminotoluene using 2-methyl-4-nitro-5-chloroaniline (5-chloro-2-methylaniline) as a raw material. Summary of the Invention

[0014] The present invention addresses the aforementioned limitations of existing technologies by providing a method for preparing 2,5-diaminotoluene and its sulfate. This invention uses 2-methyl-4-nitro-5-chloroaniline as a raw material, employing a two-step process of nitro-catalyzed hydrogenation reduction and catalytic hydrogenation dechlorination to selectively synthesize 2,5-diaminotoluene. The obtained 2,5-diaminotoluene is then reacted with sulfuric acid to form a salt, yielding the sulfate. This invention, through a two-step hydrogenation process, improves the yield of 2,5-diaminotoluene and optimizes reaction conditions for industrial production. Furthermore, the preparation method of this invention conforms to green chemistry principles, significantly reducing environmental pressure and wastewater treatment costs. Specifically, the yield of the 2,5-diaminotoluene sulfate obtained by this invention can reach over 85%, with a purity >99.5%.

[0015] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a method for preparing 2,5-diaminotoluene, comprising the following steps: (1) After mixing 2-methyl-4-nitro-5-chloroaniline, water, hydrogenation catalyst and catalyst promoter, hydrogenation reaction is carried out in hydrogen atmosphere. After the reaction is completed, the temperature is lowered, filtered, and the filtered liquid is collected to obtain hydrogenation liquid. (2) After adding sodium hydroxide and dechlorination catalyst to the hydrogenation liquid, the dechlorination reaction is carried out under hydrogen atmosphere. After the reaction is completed, the liquid is cooled, filtered, and the filtered liquid is collected and purified to obtain 2,5-diaminotoluene.

[0016] Preferably, in step (1), the hydrogenation catalyst is Pt / C, and the catalyst promoter is ferrous sulfate and / or nickel sulfate.

[0017] Furthermore, the Pt loading in Pt / C is 1.5-2.5%.

[0018] Preferably, in step (1), the mass ratio of 2-methyl-4-nitro-5-chloroaniline, water, hydrogenation catalyst and catalyst promoter is (40-120):(120-360):(1-2):(0.2-0.3).

[0019] Preferably, the mixing speed is maintained at 600-1000 r / min during the mixing process.

[0020] Preferably, in step (1), the reaction pressure is 0.8-1.5 MPa, the reaction temperature is 70-95℃, and the reaction time is 15-25 min during the hydrogenation reaction.

[0021] Preferably, in step (1), the temperature is lowered to below 60-70°C.

[0022] Preferably, in step (2), the dechlorination catalyst is Pd / C.

[0023] Furthermore, the Pd loading in Pd / C is 1.5-2.5%.

[0024] Preferably, in step (2), the purity of sodium hydroxide is 99%.

[0025] Preferably, in step (2), the mass ratio of 2-methyl-5-chloro-p-phenylenediamine, sodium hydroxide, and dechlorination catalyst in the hydrogenation solution is (150-160):(40-45):(0.5-1). Preferably, in step (2), during the dechlorination reaction, the reaction pressure is 1.0-1.5 MPa and the reaction temperature is 90-120 °C; the reaction continues until the system pressure no longer decreases.

[0026] Preferably, in step (2), the temperature is lowered to below 60-70°C.

[0027] As a preferred option, in step (2), the specific operation of purification is as follows: the filtered liquid is heated to a temperature not higher than (80-90)℃ for dehydration under reduced pressure, and then the temperature is raised to 135-145℃ and the pressure is reduced to 0.8-1.2MPa. The fraction at 140-160℃ is collected to obtain 2,5-diaminotoluene.

[0028] Preferably, in step (2), the purity of 2,5-diaminotoluene is >99%.

[0029] A second aspect of the present invention provides a method for preparing 2,5-diaminotoluene sulfate, comprising the following steps: The 2,5-diaminotoluene obtained by the above method was added to water, cooled, and then concentrated sulfuric acid was added with stirring to carry out the reaction. After the reaction was completed, the product was filtered and purified to obtain 2,5-diaminotoluene sulfate.

[0030] Preferably, the mass ratio of 2,5-diaminotoluene to water is 1:(2-4).

[0031] As a preferred option, the temperature should be lowered to 15-25℃.

[0032] Preferably, the mass ratio of 2,5-diaminotoluene to concentrated sulfuric acid is (120-125):(95-100), and the mass fraction of concentrated sulfuric acid is 98%.

[0033] Preferably, the reaction temperature is 5-20℃ and the reaction time is 1.5-2.5h.

[0034] As a preferred method, the specific purification procedure is as follows: after dissolving the filtered solid in water, sulfuric acid is added dropwise while cooling, followed by separation and drying to obtain 2,5-diaminotoluene sulfate.

[0035] Preferably, the purity of 2,5-diaminotoluene sulfate is >99.5%.

[0036] The beneficial effects of this invention are: 1. This invention uses 2-methyl-4-nitro-5-chloroaniline as a raw material and synthesizes 2,5-diaminotoluene with high selectivity through a two-step continuous catalytic hydrogenation process involving nitration hydrogenation and dechlorination hydrogenation. The obtained 2,5-diaminotoluene is then reacted with sulfuric acid to form a salt, yielding 2,5-diaminotoluene sulfate. This invention, through a two-step hydrogenation process, not only improves the yield of 2,5-diaminotoluene but also optimizes the reaction conditions for industrial production. Furthermore, the preparation method of this invention conforms to green chemistry principles, significantly reducing environmental pressure and wastewater treatment costs.

[0037] 2. 2-Methyl-4-nitro-5-chloroaniline is prepared by reacting 5-chloro-o-toluidine, which is a low-cost byproduct. This effectively reduces the preparation cost of 2-methyl-4-nitro-5-chloroaniline to approximately RMB 46,000 per ton. Furthermore, this invention uses 2-methyl-4-nitro-5-chloroaniline as a raw material. The halogen group (-Cl) in its molecular structure can act as a nitro group, resulting in a selectivity of over 92% for nitration hydrogenation during the hydrogenation process. Additionally, using 2-methyl-4-nitro-5-chloroaniline as a raw material can increase the yield of 2,5-diaminotoluene to over 85%. Moreover, using 2-methyl-4-nitro-5-chloroaniline as a raw material significantly reduces the generation of waste during the reaction, meeting the requirements of green chemistry production.

[0038] 3. In the nitro hydrogenation process of this invention, ferrous sulfate and / or nickel sulfate are used as catalysts and auxiliaries, which not only ensures the orderly process of nitro-to-amino reduction, but also reduces tar production. Detailed Implementation

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 application pertains.

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0042] In this invention, the CAS number of 2-methyl-4-nitro-5-chloroaniline is 13852-51-2.

[0043] Example 1: Preparation method of 2,5-diaminotoluene sulfate (1) Mix 2-methyl-4-nitro-5-chloroaniline, water, 2% Pt / C and ferrous sulfate in a mass ratio of 40:120:1:0.2 and add them to the hydrogenation reactor. After closing the reactor lid, purge with nitrogen three times and with hydrogen three times in sequence. Stir at 800 r / min and then react at 85℃ and 1.2 MPa hydrogen pressure for 20 min. After the reaction is completed, cool down to below 70℃, vent and purge with nitrogen. Open the hydrogenation reactor to discharge the material, filter, and collect the filtered liquid to obtain the hydrogenation liquid. (2) Add sodium hydroxide and 2% Pd / C to the hydrogenation solution in step (1). The mass ratio of 2-methyl-5-chloro-p-phenylenediamine, sodium hydroxide and Pd / C in the hydrogenation solution is controlled to be 155:41:0.8. After closing the kettle lid, the solution is purged with nitrogen three times and hydrogen three times. The solution is then placed at 120℃ and 1.2MPa hydrogen pressure to react until the pressure of the system no longer changes. Then the temperature is lowered to below 70℃, the system is purged with nitrogen, the hydrogenation kettle is opened to discharge the material, filtered, and the filtered liquid is collected. The filtered liquid is heated to 80℃ for dehydration under reduced pressure. Then the temperature is raised to 140℃ and the pressure is reduced to 1.0MPa. The fraction at 140-160℃ is collected to obtain 2,5-diaminotoluene. (3) Mix 2,5-diaminotoluene and water at a mass ratio of 1:3, cool to 20°C, and add 98% concentrated sulfuric acid while stirring. The mass ratio of 2,5-diaminotoluene to concentrated sulfuric acid is 122:99. React at 15°C for 2 hours. After the reaction is complete, filter, collect the filtered solid, dissolve it in water, cool it, add sulfuric acid dropwise, centrifuge, and dry the centrifuged solid to obtain 2,5-diaminotoluene sulfate.

[0044] The yield of 2,5-diaminotoluene sulfate obtained in this embodiment was 86%. The purity of the obtained 2,5-diaminotoluene was 99.2% and the purity of 2,5-diaminotoluene sulfate was 99.8% as determined by high performance liquid chromatography.

[0045] Example 2: Preparation method of 2,5-diaminotoluene (1) Mix 2-methyl-4-nitro-5-chloroaniline, water, 2% Pt / C and nickel sulfate in a mass ratio of 80:240:1.5:0.25 and add them to the hydrogenation reactor. After closing the reactor lid, replace the reactor with nitrogen three times and then with hydrogen three times. Stir at 600 r / min and then react at 70℃ and 0.8 MPa hydrogen pressure for 15 min. After the reaction is completed, cool down to below 65℃, vent and replace with nitrogen. Open the hydrogenation reactor to discharge the material, filter, and collect the filtered liquid to obtain the hydrogenation liquid. (2) Add sodium hydroxide and 2% Pd / C to the hydrogenation solution in step (1). The mass ratio of 2-methyl-5-chloro-p-phenylenediamine, sodium hydroxide and Pd / C in the hydrogenation solution is controlled to be 150:40:0.5. After closing the kettle lid, the mixture is purged with nitrogen three times and hydrogen three times. The mixture is then placed at 90°C and 1.2 MPa hydrogen pressure to react until the pressure of the system no longer changes. The temperature is then lowered to 60°C, and after venting, nitrogen is purged. The hydrogenation kettle is then opened to discharge the material, filtered, and the filtered liquid is collected. The filtered liquid is heated to 85°C for dehydration under reduced pressure. Then the temperature is raised to 140°C and the pressure is reduced to 0.8 MPa. The fraction at 140-160°C is collected to obtain 2,5-diaminotoluene.

[0046] (3) Mix 2,5-diaminotoluene and water at a mass ratio of 1:2, cool to 15°C, and add 98% concentrated sulfuric acid while stirring. The mass ratio of 2,5-diaminotoluene to concentrated sulfuric acid is 122:99. React at 5°C for 2.5 hours. After the reaction is complete, filter, collect the filtered solid, dissolve it in water, cool it, add sulfuric acid dropwise, centrifuge, and dry the centrifuged solid mechanically to obtain 2,5-diaminotoluene sulfate.

[0047] The yield of 2,5-diaminotoluene sulfate obtained in this embodiment was 82%. The purity of the obtained 2,5-diaminotoluene was 99.0% and the purity of 2,5-diaminotoluene sulfate was 99.5% as determined by high performance liquid chromatography.

[0048] Example 3: (1) Mix 2-methyl-4-nitro-5-chloroaniline, water, 2% Pt / C 2g and nickel sulfate in a mass ratio of 120:360:2:0.3 and add them to the hydrogenation reactor. After closing the reactor lid, replace with nitrogen three times and with hydrogen three times in sequence. Stir at 1000 r / min and then react at 95℃ and 1.5 MPa hydrogen pressure for 25 min. After the reaction is completed, cool down to below 70℃, vent and replace with nitrogen. Open the hydrogenation reactor to discharge the material, filter, and collect the filtered liquid to obtain the hydrogenation liquid. (2) Add sodium hydroxide and 2% Pd / C to the hydrogenation solution in step (1). The mass ratio of 2-methyl-5-chloro-p-phenylenediamine, sodium hydroxide, and Pd / C in the hydrogenation solution is controlled to be 160:45:1. After closing the kettle lid, purge with nitrogen three times and with hydrogen three times in sequence. Then, place the kettle at 120°C and 1.5 MPa hydrogen pressure until the pressure of the system no longer changes. Then, cool down to 70°C, vent, and purge with nitrogen. Open the hydrogenation kettle to discharge the material, filter, collect the filtered liquid, heat the filtered liquid to 85°C for dehydration under reduced pressure, and then heat to 14°C. Reduce the pressure to 1.2 MPa at 5℃ and collect the fraction at 140-160℃ to obtain 2,5-diaminotoluene; (3) Mix 2,5-diaminotoluene and water at a mass ratio of 1:2, cool to 15℃, and add concentrated sulfuric acid with a mass fraction of 98% under stirring. The mass ratio of 2,5-diaminotoluene to concentrated sulfuric acid is 122:99. React at 5℃ for 2.5h. After the reaction is completed, filter, collect the filtered solid, dissolve it in water, cool it, add sulfuric acid dropwise, centrifuge, and dry the centrifuged solid mechanically to obtain 2,5-diaminotoluene sulfate.

[0049] The yield of 2,5-diaminotoluene sulfate obtained in this embodiment was 84%. The purity of the obtained 2,5-diaminotoluene was 99.3% and the purity of 2,5-diaminotoluene sulfate was 99.6% as determined by high performance liquid chromatography.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing 2,5-diaminotoluene, characterized in that, Includes the following steps: (1) After mixing 2-methyl-4-nitro-5-chloroaniline, water, hydrogenation catalyst and catalyst promoter, hydrogenation reaction is carried out in hydrogen atmosphere. After the reaction is completed, the temperature is lowered, filtered, and the filtered liquid is collected to obtain hydrogenation liquid. (2) After adding sodium hydroxide and dechlorination catalyst to the hydrogenation liquid, the dechlorination reaction is carried out under hydrogen atmosphere. After the reaction is completed, the liquid is cooled, filtered, and the filtered liquid is collected and purified to obtain 2,5-diaminotoluene.

2. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (1), the hydrogenation catalyst is Pt / C, the loading of Pt in Pt / C is 1.5-2.5%, and the catalyst promoter is ferrous sulfate and / or nickel sulfate.

3. The method for preparing 2,5-diaminotoluene as described in claim 1, characterized in that, In step (1), the mass ratio of 2-methyl-4-nitro-5-chloroaniline, water, hydrogenation catalyst and catalyst promoter is (40-120): (120-360): (1-2): (0.2-0.3).

4. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (1), during the hydrogenation reaction, the reaction pressure is 0.8-1.5 MPa, the reaction temperature is 70-95℃, and the reaction time is 15-25 min.

5. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (2), the dechlorination catalyst is Pd / C, and the loading of Pd in ​​Pd / C is 1.2-2.5%.

6. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (2), the mass ratio of 2-methyl-5-chloro-p-phenylenediamine, sodium hydroxide and dechlorination catalyst in the hydrogenation solution is (150-160): (40-45): (0.5-1).

7. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (2), during the dechlorination reaction, the reaction pressure is 1.0-1.5 MPa and the reaction temperature is 90-120℃; the reaction continues until the system pressure no longer decreases.

8. The method for preparing 2,5-diaminotoluene according to claim 1, characterized in that, In step (2), the specific operation of purification is to heat the filtered liquid to a temperature not higher than (80-90)℃ for dehydration under reduced pressure, then raise the temperature to 135-145℃ and reduce the pressure to 0.8-1.2MPa, and collect the fraction at 140-160℃ to obtain 2,5-diaminotoluene.

9. A method for preparing 2,5-diaminotoluene sulfate, characterized in that, Includes the following steps: The 2,5-diaminotoluene prepared according to any one of claims 1-8 is added to water, cooled to 15-25°C, and then concentrated sulfuric acid is added under stirring to carry out the reaction. After the reaction is completed, the product is filtered and purified to obtain 2,5-diaminotoluene sulfate.

10. The method for preparing 2,5-diaminotoluene sulfate as described in claim 9, characterized in that, The mass ratio of 2,5-diaminotoluene to water is 1:(2-4), the mass ratio of 2,5-diaminotoluene to concentrated sulfuric acid is (120-125):(95-100), the mass fraction of concentrated sulfuric acid is 98%, the reaction temperature is 5-20℃, and the reaction time is 1.5-2.5h.

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