A method for separating a diaminotoluene mixture to prepare a single component thereof
A selective crystallization process using a dibasic acid with a substituent forms inner salts with 2,4-diaminotoluene but not 2,6-diaminotoluene, enabling efficient and environmentally friendly separation and purification of both isomers for industrial use.
Patent Information
- Application Number
- CN202010931704.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-09-02
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2040-09-02
AI Technical Summary
Existing methods for separating 2,4-diaminotoluene and 2,6-diaminotoluene are inefficient, costly, environmentally harmful, and difficult to implement on an industrial scale due to their reliance on chemical derivatization crystallization, molecular sieves, and resin methods, which fail to achieve complete separation and generate hazardous residues.
A method involving dissolving the diaminotoluene mixture in a polar solvent with a dibasic acid having a substituent, forming an inner salt with 2,4-diaminotoluene while avoiding strong reactions, allowing for selective crystallization and subsequent acid-base treatment to separate and purify both isomers.
The method achieves complete separation of 2,4-diaminotoluene and 2,6-diaminotoluene with high yield and purity, reduces waste, avoids hazardous operations, and is suitable for industrial production with low energy consumption and cost.
Smart Images
Figure GSB0000190787650000011 
Figure GSB0000190787650000012 
Figure GSB0000190787650000021
Abstract
Description
[0001] 1. Technical field: The present invention belongs to the technical field of chemical raw material synthesis, and in particular to a method for separating a diaminotoluene mixture to prepare a single component thereof.
[0002] 2. Background technology: There are many isomers of diaminotoluene. The present invention refers to the separation of a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene. The separate production of 2,4-diaminotoluene and 2,6-diaminotoluene has certain difficulties and safety risks in terms of technology and production, and the process is relatively complicated and the cost is high. In order to solve this problem, in the case of large-scale production of mixed diaminotoluene in the current polyurethane industry, some of its products are separated to prepare qualified single components of 2,4-diaminotoluene and 2,6-diaminotoluene, which plays a role in the effective utilization of resources, is safe and environmentally friendly, simplifies the production process of the two diaminotoluenes, and reduces their cost structure and investment ratio.
[0003] 2,4-Diaminotoluene: English name 2,4-Diaminotoluene, colorless to light brown needle-shaped crystals or prismatic crystals, easily soluble in hot water, ethanol, and ether. Melting point 97-99℃, boiling point 283-285℃, flash point 149℃. Toxic items, flammable in case of open flames, high heat decomposition to produce toxic nitrogen oxide fumes.
[0004] Molecular formula and molecular weight: C7H10N2=122.17
[0005] Structural formula:
[0006]
[0007] 2,4-Diaminotoluene is used as an organic synthesis intermediate to produce high-quality toluene diisocyanate and dyes such as fur black DB, sulphur yellow brown 5G, sulphur yellow brown 6G, sulphur red brown B3R, etc. The dyes produced can directly oxidize fur and hair into black, etc.
[0008] 2,6-Diaminotoluene: English name 2,6-Diaminotoluene, colorless to light brown needle-shaped crystals or prismatic crystals, easily soluble in hot water, ethanol, and ether. Melting point 104-106℃, boiling point 289℃; toxic items, flammable in case of open flame; high heat decomposition to produce toxic nitrogen oxide fumes.
[0009] Molecular formula and molecular weight: C7H10N2=122.17
[0010] Structural formula:
[0011]
[0012] 2,6-Diaminotoluene is an important chemical intermediate that can be used in the synthesis of polyurethane soft foam plastics, coatings, rubber and adhesives. 2,6-Diaminotoluene can also be used as a dye intermediate for the synthesis of a variety of dyes.
[0013] In recent years, with the continuous promotion of the application of 2,6-diaminotoluene downstream products, the market demand has increased rapidly. my country's technical development of 2,6-diaminotoluene is relatively late, and currently only a few factories are mass-producing it, and the product is in short supply. Investing in 2,6-diaminotoluene projects in my country has broad market prospects.
[0014] 2,4-diaminotoluene and 2,6-diaminotoluene are important intermediates. The method for synthesizing the mixture of 2,4-diaminotoluene and 2,6-diaminotoluene in industry is usually to first nitrate toluene to obtain mixed dinitrotoluene, and then obtain meta-mixed dinitrotoluene after distillation separation and removal of ortho-dinitrotoluene, and then reduce to obtain mixed diaminotoluene, wherein the content of 2,4-diaminotoluene and 2,6-diaminotoluene mainly has two ratios (mass isomer ratio): about 80:20 or about 65:35. The main reaction process is as follows:
[0015]
[0016] Because the dyes synthesized from pure 2,4-diaminotoluene and 2,6-diaminotoluene are of better quality, the polyurethane polymerized from pure diaminotoluene has better performance, and only pure 2,4-diaminotoluene and 2,6-diaminotoluene can be used as organic intermediates for further application in dyes, pesticides, medicines and further processing of downstream products; after further reaction, 2,6-diaminotoluene can be used for more professional purposes such as daily chemical products, anticancer drugs, special materials, etc. Therefore, the economical and efficient purification of diaminotoluene has broad industrial prospects.
[0017] However, 2,4-diaminotoluene and 2,6-diaminotoluene have the same molecular weight and similar molecular structure. It is very difficult to completely separate and prepare a single component of a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene, especially a mixture of the two diaminotoluenes with a component ratio close to 1:1.
[0018] At present, although there are relevant reports on the separation and preparation of 2,4-diaminotoluene and 2,6-diaminotoluene from mixed diaminotoluene at home and abroad, for example, in patents CN201310290516.X, CN106699572A and US4256671A, a derivatization crystallization method is used to separate and purify 2,4-diaminotoluene and 2,6-diaminotoluene: it is said that a small amount of sodium chloride is added to an aqueous solution, and the pH value is adjusted by hydrochloric acid so that 2,6-diaminotoluene is precipitated into hydrochloric acid crystals and separated from 2,4-diaminotoluene. In theory, there is a reasonable separation principle, but the separation effect is not ideal after experimental verification; in patents CN104402732A and US6469212B1, only 60%-85% of 2,4-diaminotoluene and 15% to Part of 2,4-diaminotoluene is separated from a mixture of about 40% 2,6-diaminotoluene, and the remaining mixture of 2,4-diaminotoluene and 2,6-monoaminotoluene in a ratio of about 1:1 cannot be separated further; in the document "Adsorption Separation of Diaminotoluene", a modified molecular sieve is used as an adsorbent, methanol, ethanol, cyclohexylamine, and o-toluidine are used as eluents, and a fixed bed pulse feeding dynamic adsorption method is used to perform adsorption separation of a mixture of 2,4-TDA and 2,6-TDA. This method requires large equipment investment, is cumbersome to operate, and has weak industrial production capacity; in the document "Adsorption Separation of 2,4- / 2,6-Diaminotoluene on D151 Resin", D151 resin is used to study the adsorption separation of 2,4-diaminotoluene and 2,6-diaminotoluene, but industrialization has certain difficulties.
[0019] Therefore, the resin method and molecular sieve method have low output and cannot meet the needs of industrial production, while the chemical derivatization crystallization method cannot be completely separated, the residual liquid is difficult to handle, and it is easy to cause secondary pollution. Therefore, the separation and purification technology of 2,4-diaminotoluene and 2,6-diaminotoluene with low environmental pollution, simple production process and low energy consumption has extremely high market value. 3. Summary of the invention:
[0021] (1) Purpose of the invention: The purpose of the method for separating a diaminotoluene mixture and preparing its single component is to provide a simple, effective, mild, environmentally friendly and energy-saving method for separating a mixture of 2,4-diaminotoluene and 2,6-diaminotoluene, which has good quality and high yield and is suitable for industrial production.
[0022] (2) Technical solution: The present invention provides a method for separating a diaminotoluene mixture to prepare a single component thereof, wherein a mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene is dissolved in a certain amount of polar solvent, and then a certain amount of a dibasic acid with a substituent is added, and the mixture is heated and stirred to react, so that 2,4-diaminotoluene and the dibasic acid with a substituent form a complex inner salt and crystallize out. 2,3-dihydroxysuccinic acid is used as an example as follows:
[0023]
[0024] However, 2,6-diaminotoluene is difficult to form a compound inner salt with a dibasic acid having a substituent due to the steric hindrance formed by the methyl group on the benzene ring and the substituent in the dibasic acid. 2,3-dihydroxysuccinic acid is used as an example as follows:
[0025]
[0026] Therefore, the free body of 2,6-diaminotoluene or the open salt formed by 2,6-diaminotoluene and the dibasic acid of the substituent is dissolved in a polar solvent, and then after cooling, filtering and washing, a mother liquor and a crystallization filter cake are obtained, and the mother liquor is concentrated and crystallized or purified by changing the solvent for crystallization to obtain qualified 2,6-diaminotoluene, and the crystallization filter cake is added to the solvent again, and an alkaline substance is added to form a salt with the dibasic acid of the substituent to precipitate (or dissolve), so that 2,4-diaminotoluene is free and dissolved (or precipitated), and qualified 2,4-diaminotoluene is obtained after separation. The present invention solves the separation problem of diaminotoluene mixture, and the conditions are mild, and it can be used for industrial production.
[0027] The separation and purification of 2,4-diaminotoluene and 2,6-diaminotoluene of the present invention adopts a special crystallization separation method in which a dibasic acid having a substituent on the carbon atom between two carboxyl groups and 2,4-diaminotoluene can form an inner salt, and there is almost no strong chemical combination and decomposition reaction, only a simple acid-base reaction, so that 2,4-diaminotoluene and 2,6-diaminotoluene are completely separated and purified, and no difficult-to-treat residual liquid is generated. The two dangerous process operations of nitration and hydrogenation are avoided, all relevant solvents are recycled, and almost no waste water is generated.
[0028] (3) Technical effects:
[0029] The separation and purification of 2,4-diaminotoluene and 2,6-diaminotoluene of the present invention adopts a special crystallization separation method in which a dibasic acid having a substituent on the carbon atom between two carboxyl groups can form an inner salt with 2,4-diaminotoluene but cannot form an inner salt with 2,6-diaminotoluene. There is almost no strong chemical combination and decomposition reaction, only a simple acid-base reaction, so that 2,4-diaminotoluene and 2,6-diaminotoluene are completely separated and purified, and no difficult-to-treat residual liquid is generated. The two dangerous process operations of nitration and hydrogenation are avoided, all related solvents are recycled and reused, and almost no waste water is generated. Continuous production has a high degree of automation, safety and environmental protection, energy saving and consumption reduction, good quality and low cost, and can be used for industrial production.
[0030] It is specifically reflected in the following aspects:
[0031] 1. A method for separating a diaminotoluene mixture to prepare a single component thereof, utilizing the special molecular structures of 2,4-diaminotoluene and 2,6-diaminotoluene, and using the stereoselectivity of a dibasic acid having a substituent on the carbon atom between two carboxyl groups, to separate 2,4-diaminotoluene and 2,6-diaminotoluene, with high selectivity and good separation effect.
[0032] 2. The method for separating a diaminotoluene mixture to prepare a single component of the present invention has a process for separating 2,4-diaminotoluene and 2,6-diaminotoluene, and the entire process is an acid-base reaction process with mild conditions, energy conservation, environmental protection, and safe operation.
[0033] 3. The method for separating a diaminotoluene mixture and preparing a single component thereof according to the present invention can recycle and utilize the dibasic acid of the substituent.
[0034] 4. The specific implementation methods of the present invention are as follows:
[0035] Example 1: 80 g (0.656 mol) of a mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene (mass ratio of 1:1) was added with 270 g of methanol and stirred to dissolve, and then 51.6 g of 2,3-dihydroxysuccinic acid was added, and the temperature was raised to 65°C and stirred to react for 10 hours, so that 2,4-diaminotoluene and 2,3-dihydroxysuccinic acid were precipitated as salts, and after cooling, filtering, and washing the filter cake with 70 g of methanol, 330 g of mother liquor and 114 g of wet weight and 88.2 g of dry weight of the crystallized filter cake were obtained.
[0036] The mother liquor was concentrated to 80-90 g under normal pressure, and then cooled to 15°C for crystallization. The filter cake was washed with cold methanol to obtain 34 g (dry weight, yield 85%) of qualified 2,6-diaminotoluene; the crystallized filter cake was added to 150 g of methanol, 33 g of 90% calcium hydroxide was added, heated and stirred for 2 hours, filtered after cooling, and the filter cake was washed with 50 g of methanol. The mother liquor was vacuum demethanolized to a residual weight of 80-90 g, cooled to 15°C for crystallization, the filter cake was washed with methanol, and 31 g (dry weight, yield 77.5%) of 2,4-diaminotoluene was obtained after drying.
[0037] Example 2: 80 g (0.656 mol) of a mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene (mass ratio of 1:1) was added with 100 g of methanol, and 200 g of the mother liquor (two pieces of mother liquor) from the previous batch was used, stirred and dissolved, and then 51.6 g of 2,3-dihydroxysuccinic acid was added, and the temperature was raised to 65°C and stirred for reaction for 10 hours, so that 2,4-diaminotoluene and 2,3-dihydroxysuccinic acid were precipitated as salts, and after cooling, filtering, and washing the filter cake with 70 g of methanol, 345 g of mother liquor and 136 g of wet weight and 107 g of dry weight of the crystallized filter cake were obtained.
[0038] The mother liquor was concentrated to 90°C under normal pressure, and then cooled to 15°C for crystallization. The filter cake was washed with cold methanol to obtain 38.9 g (dry weight, yield 97.3%) of qualified 2,6-diaminotoluene; the crystallized filter cake was added to 150 g of methanol, 33 g of 90% calcium hydroxide was added, heated and stirred for 2 hours, filtered after cooling, and the filter cake was washed with 50 g of methanol. The mother liquor was vacuum-demethanolized to a residual weight of 80-90 g, cooled to 15°C for crystallization, the filter cake was washed with methanol, and 38.2 g (dry weight, purity 99.2%, yield 95.5%) of 2,4-diaminotoluene was obtained after drying.
[0039] Example 3 (Comparative Example): 80 g (0.656 mol) of a mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene (mass ratio of 1:1) was added with 270 g of methanol and stirred to dissolve, and then 42.6 g of 1,4-butanedioic acid was added, and the temperature was raised to 65°C and stirred to react for 10 hours, so that salt crystals were precipitated. After cooling, filtering, and washing the filter cake with 70 g of methanol, 319 g of mother liquor and 111 g of crystalline filter cake were obtained. The filter cake was quantitatively analyzed by HPLC, and the purities of 2,4-diaminotoluene and 2,6-diaminotoluene were 62.5% and 36.8%, respectively. There was no significance for further separation in this experiment.
[0040] Example 4: 80 g (0.656 mol) of a mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene (mass ratio of 1:1) was added with 270 g of methanol and stirred to dissolve, and then 49 g of 2-hydroxysuccinic acid was added, and the temperature was raised to 65°C and stirred to react for 10 hours, so that 2,4-diaminotoluene and 2-hydroxysuccinic acid were salted and crystallized. After cooling, filtering, and washing the filter cake with 70 g of methanol, 335 g of mother liquor and 109 g of crystalline filter cake with a wet weight and a dry weight of 86.8 g were obtained.
[0041] The mother liquor is concentrated to 80-90 g under normal pressure, cooled to 15°C for crystallization, and the filter cake is washed with cold methanol to obtain 35 g (dry weight, yield 87.5%) of qualified 2,6-diaminotoluene; the crystallized filter cake is added to 150 g of methanol, 33 g of 90% calcium hydroxide is added, heated and stirred for 2 hours, filtered after cooling, and the filter cake is washed with 50 g of methanol, the mother liquor is vacuum-demethanolized to a residual weight of 80-90 g, cooled to 15°C for crystallization, the filter cake is washed with methanol, and 30.2 g (dry weight, yield 75.5%) of 2,4-diaminotoluene is obtained after drying.
[0042] The present invention discloses a method for separating a diaminotoluene mixture to prepare a single component thereof. The method adopts a special crystallization separation method in which a dibasic acid having a substituent on the carbon atom between two carboxyl groups can form an inner salt with 2,4-diaminotoluene but cannot form an inner salt with 2,6-diaminotoluene. There are almost no strong reaction conditions such as combination and decomposition, so that 2,4-diaminotoluene and 2,6-diaminotoluene are completely separated and purified, and no difficult-to-treat residual liquid is generated. The two dangerous process operations of nitration and hydrogenation are avoided, and all related solvents are recycled and reused, and almost no waste water is generated. The method is continuous in production, has a high degree of automation, is safe and environmentally friendly, saves energy and reduces consumption, has good quality and low cost, and can be used for industrial production. The present invention has a low investment cost, a low production start-up risk, and a lucrative business profit.
[0043] Finally, it should be noted that the above is only a preferred intermittent synthesis embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above examples, it is still possible for a person skilled in the art to modify the technical solutions described in the above embodiments, or to replace some of the technical features, or to simply use the technology of the present invention to convert it into a continuous process. Any modification, replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for separating a diaminotoluene mixture to prepare a single component thereof, characterized in that: A mixture containing 2,4-diaminotoluene and 2,6-diaminotoluene is dissolved in a certain amount of polar solvent, and then a certain amount of dibasic acid of a substituent is added, and the temperature is raised to 45-145° C. and stirred for reaction, so that 2,4-diaminotoluene and the dibasic acid of the substituent are salted and crystallized and precipitated, and after cooling, filtering, and washing, a mother liquor and a crystallization filter cake are obtained, and the mother liquor is concentrated and crystallized or purified by changing the solvent for crystallization to obtain qualified 2,6-diaminotoluene, and the crystallization filter cake is redissolved in a solvent, and an alkaline substance is added to form a salt with the dibasic acid of the substituent to precipitate or dissolve, so that 2,4-diaminotoluene is free dissolved or precipitated, and qualified 2,4-diaminotoluene is obtained after separation; The polar solvent is methanol, ethanol, isopropanol, butanol, acetone, ethylene glycol, tetrahydrofuran, cyclohexanol and a mixture thereof; The substituent dibasic acid is a dibasic acid having two carboxyl groups in its molecular structure, and the two carboxyl groups can simultaneously form an inner salt with two amino groups in 2,4-diaminotoluene, and at least one carbon atom is spaced between the two carboxyl groups, and the carbon atom spaced between the two carboxyl groups has other substituents except hydrogen atoms, and the substituents are sufficient to hinder the dibasic acid of the substituent from forming an inner salt with the two amino groups of 2,6-diaminotoluene due to the steric hindrance of the methyl group and the substituent of the dibasic acid of the substituent, when the dibasic acid of the substituent contacts and reacts with 2,6-diaminotoluene. The substituent dibasic acid is selected from: 2-hydroxysuccinic acid, itaconic acid, oxaloacetic acid, 2,3-dihydroxysuccinic acid, 2-methylsuccinic acid, 2,3-dimethylsuccinic acid, 2-chlorosuccinic acid, 2,3-dichlorosuccinic acid, 2,3-dimercaptotartaric acid, bromosuccinic acid, trimethylglutaric acid, and its spatial structure does not distinguish between chirality, but a single chiral substituent dibasic acid can be used.
2. The method for separating a diaminotoluene mixture and preparing a single component thereof according to claim 1, characterized in that: The diaminotoluene mixture used is a mixture obtained by reducing nitro groups of dinitrotoluene, a TDA mixture as an intermediate for TDI production, and a mixture obtained by separating part of 2,4-diaminotoluene from the TDA mixture.
3. A method for separating and preparing a single component of a diaminotoluene mixture according to any one of claims 1 and 2, characterized in that: The ratio of 2,4-diaminotoluene to 2,6-diaminotoluene in the diaminotoluene mixture used is 1:0.1-10.
4. A method for separating and preparing a single component of a diaminotoluene mixture according to claim 1, characterized in that: The amount ratio of the added quantitative substituent dibasic acid to the amount of 2,4-diaminotoluene in the diaminotoluene mixture is 1:0.5-1.
5.
5. The method for separating a diaminotoluene mixture and preparing a single component thereof according to claim 1, characterized in that: The crystallized filter cake is redissolved in a solvent, and the alkaline substances added are: ammonia, monomethylamine, dimethylamine, trimethylamine, tetramethylammonium hydroxide, monoethylamine, diethylamine, triethylamine, calcium hydroxide, calcium oxide, sodium hydroxide, and magnesium hydroxide.