A kind of preparation method of diethyltoluenediamine

Abstract

The invention provides a method for preparing diethyltoluenediamine by alkylating toluenediamine. The method adopts an ethylene composite gas instead of pure ethylene. Compared with the prior art, the method can greatly reduce the reaction temperature and reaction pressure, eliminate the deamination and demethylation side reactions, avoid the N-alkylation side reaction, and reduce the over-alkylation of toluenediamine, so that the DETDA reaction yield is significantly improved, which can reach up to 99%.

Description

Technical Field

[0001] The invention belongs to the field of preparation of diethyltoluenediamine, and more specifically relates to a method for preparing diethyltoluenediamine by alkylation of toluenediamine. Background Art

[0002] Diethyltoluenediamine, referred to as DETDA, is a low-viscosity, non-toxic, odorless light yellow liquid. It is mainly used in the fields of chain extenders for polyurethane and polyurea elastomers, polyurethane and epoxy resin curing agents, coatings, lubricants, industrial oil antioxidants, chemical synthesis intermediates, etc. Commercialized DETDA is a mixture of 3,5-diethyl-2,4-toluenediamine (about 80%) and 3,5-diethyl-2,6-toluenediamine (about 20%). The structural formula is as follows:

[0003]

[0004] DETDA is usually made of toluenediamine (TDA) and ethylene as raw materials. In the presence of a catalyst, a Friedel-Crafts alkylation reaction occurs under high temperature and high pressure conditions to obtain crude DETDA. The catalyst is further separated and removed, and pure DETDA is obtained by distillation. The main reaction is as follows:

[0005]

[0006] The key to this reaction is the catalyst, which must provide a certain Lewis acidity to promote the alkylation of the benzene ring. Considering factors such as production cost, operational stability, and especially reaction effect, the current large-scale production of DETDA generally uses aluminum powder, zinc powder and / or AlCl3 as catalysts, but the process conditions are extremely harsh, with the reaction temperature usually as high as 200-300°C and the reaction pressure up to 50MPa. Although the harsh process conditions are conducive to the polarization of ethylene, so that it reacts with toluenediamine to form DETDA, they also increase the possibility of DETDA further reacting with ethylene to form triethyltoluenediamine (ETDA); and excessively high temperature and pressure will promote the occurrence of a large number of side reactions, such as the demethylation and deamination reactions of toluenediamine. These demethylation and deamination products will continue to react with ethylene to generate a large number of ethylated byproducts; in addition, Lewis acid can also promote the occurrence of N-alkylation reactions on the benzene ring, resulting in a large number of N-alkylation substitution byproducts of toluenediamine. Therefore, how to avoid the occurrence of side reactions and promote the reaction to DETDA has become the key to improving the efficiency of the alkylation reaction of toluenediamine. Summary of the invention

[0007] To solve the above problems, the present invention provides a method for preparing diethyltoluenediamine. The method uses an ethylene composite gas instead of pure ethylene. Compared with the prior art, the method can significantly reduce the reaction temperature and reaction pressure, eliminate the deamination and demethylation side reactions, avoid the N-alkylation side reactions, and reduce the over-alkylation of toluenediamine, thereby significantly improving the DETDA reaction yield, up to 99%.

[0008] To achieve the purpose of the present invention, the present invention can adopt the following technical scheme: a method for preparing diethyltoluenediamine, comprising the following steps:

[0009] (1) Adding toluenediamine and Lewis acid catalyst into the kettle, and then replacing with nitrogen;

[0010] (2) heating the reactor to 200-250° C. and stirring for 1-5 hours to form a catalytic system;

[0011] (3) After the temperature of the reactor drops to 100-120°C, nitrogen and ethylene are used for replacement in sequence, and then ethylene composite gas is introduced into the reactor;

[0012] (4) After the reactor is heated to 150-200° C., ethylene composite gas is continuously introduced, the reaction pressure is maintained at 5-8 MPa, and the reaction is carried out for 2-5 hours;

[0013] (5) Cooling, releasing the pressure, and discharging the material to obtain a DETDA reaction solution.

[0014] In step (1) of the present invention, the Lewis acid catalyst is one or more of aluminum powder, zinc powder, aluminum / zinc alloy, aluminum chloride, and aluminum alkylate.

[0015] In step (1) of the present invention, the amount of the Lewis acid catalyst added is 1 to 10% of the mass of toluenediamine, preferably 2 to 5%.

[0016] In step (2) of the present invention, the preferred temperature for forming the catalyst system is 200 to 220° C. and the time is 1 to 2 hours.

[0017] In step (3) of the present invention, the ethylene composite gas mainly includes ethylene, protonic acid gas, ammonia gas and reaction inert gas.

[0018] The ethylene composite gas comprises the following components in volume fractions:

[0019] The volume fraction of ethylene is 80-99%, preferably 85-95%; the volume fraction of protonic acid gas is 0-20%, preferably 2-5%; the volume fraction of ammonia gas is 0-20%, preferably 2-5%; the volume fraction of reaction inert gas is 0-15%, preferably 1-10%.

[0020] In the ethylene composite gas, the volume fractions of the protonic acid gas and the ammonia gas are not zero at the same time.

[0021] Preferably, in the step 3), the pressure after the ethylene composite gas is introduced is 3-4 MPa.

[0022] In the ethylene composite gas, the protonic acid gas includes one or more of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen sulfide, and fluorosilicic acid gas.

[0023] In the ethylene composite gas, the ammonia gas includes one or more of ammonia, monomethylamine, dimethylamine, and trimethylamine.

[0024] In the ethylene composite gas, the reaction inert gas includes one or more of nitrogen, helium, argon, krypton, xenon and radon.

[0025] In step (4) of the present invention, the reaction temperature can be 150°C, 160°C, 170°C, 180°C, or 190°C, preferably 160-170°C, with a reaction pressure of 5-6 MPa and a reaction time of 2-3 hours.

[0026] Preferably, the amount of ethylene added in the total amount of the ethylene composite gas added is greater than the theoretical amount of ethylene and toluenediamine reacted, that is, the amount of ethylene is excessive.

[0027] The present invention has the following beneficial effects:

[0028] 1. By using ethylene composite gas, the temperature and pressure of the toluene diamine alkylation reaction are greatly reduced, the occurrence of side reactions is reduced, and the DETDA reaction yield can reach up to 99%, greatly reducing the production cost.

[0029] 2. Compared with pure ethylene, ethylene composite gas can improve reaction activity and reduce the occurrence of side reactions. Among them, protonic acid gas can provide highly active Brewster acid (B acid), which cooperates with Lewis acid (L acid) to make ethylene easier to polarize, while increasing the electron cloud density on the aromatic ring of toluenediamine, making it easier for the carbon cation formed by ethylene to form a π complex with the aromatic ring, and then form a σ complex, and dehydrogenate to obtain an ethylated product. The synergistic effect of this BL acid can make ethylene react with toluenediamine at a lower temperature and pressure, thereby avoiding deamination and demethylation reactions at high temperatures. Ammonia gases such as ammonia and monomethylamine can provide lone pairs of electrons. The activity of these lone pairs of electrons will not weaken the occurrence of diethyl substitution, but can significantly prevent the occurrence of over-alkylation reactions of triethyl substitution, so that the entire reaction is controlled at the diethyl substitution stage that is more likely to occur; in addition, a certain amount of inert gas can also adjust the ethylene partial pressure to further prevent the generation of over-alkylated products. DETAILED DESCRIPTION

[0030] Toluenediamine (≥99% (GC)) was purchased from Wanhua Chemical, aluminum powder (AR), zinc powder (AR), anhydrous aluminum chloride (AR), and zinc / aluminum alloy were all purchased from Aladdin Reagent, and gases such as ethylene and hydrogen chloride were all purchased from Wanhua Chemical.

[0031] Gas chromatography analysis method: Agilent GC-6890; DB-5 chromatographic column; temperature increased from 80°C to 230°C at 10°C / min, then increased to 300°C at 20°C / min and maintained for 12 min.

[0032] Example 1

[0033] 300g toluenediamine, 3g aluminum powder, 3g zinc powder and 3g anhydrous aluminum chloride were added to a 500ml high-pressure reactor, and after nitrogen replacement was performed 5 times, the temperature in the reactor was raised to 205°C and maintained for 1.5 hours; thereafter, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were used for replacement 5 times respectively; ethylene, hydrogen chloride, ammonia and nitrogen were used to prepare ethylene composite gas, and the volume fractions of each component were adjusted to 95%, 2%, 2% and 1% respectively, and the prepared ethylene composite gas was passed into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 160°C, and ethylene composite gas was continuously passed to maintain the reaction pressure at 5MPa, and the reaction was performed for 2 hours; finally, the temperature was lowered, the pressure was released and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 99.1%.

[0034] Example 2

[0035] 300g toluenediamine and 3g aluminum powder were added to a 500ml high-pressure reactor, and after nitrogen replacement was performed 3 times, the temperature in the reactor was raised to 200°C and maintained for 2 hours; thereafter, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were used for replacement 5 times respectively; ethylene, hydrogen chloride, hydrogen fluoride, ammonia, monomethylamine, and helium were used to prepare ethylene composite gas, and the volume fractions of each component were adjusted to 80%, 5%, 5%, 2%, 3%, and 5%, respectively, and the prepared ethylene composite gas was passed into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 165°C, and ethylene composite gas was continuously passed to maintain the reaction pressure at 5MPa, and the reaction was performed for 3 hours; finally, the temperature was lowered, the pressure was released, and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 97.6%.

[0036] Example 3

[0037] 300g toluenediamine, 12g aluminum powder and 12g zinc powder were added to a 500ml high-pressure reactor, and after nitrogen replacement was performed 5 times, the temperature in the reactor was raised to 210°C and maintained for 1 hour; thereafter, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were used for replacement 5 times respectively; ethylene, hydrogen fluoride, monomethylamine and trimethylamine were used to prepare ethylene composite gas, and the volume fractions of each component were adjusted to 90%, 5%, 3% and 2% respectively, and the prepared ethylene composite gas was passed into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 170°C, and ethylene composite gas was continuously passed to maintain the reaction pressure at 6MPa, and the reaction was performed for 2 hours; finally, the temperature was lowered, the pressure was released and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 98.5%.

[0038] Example 4

[0039] 300g toluenediamine and 15g aluminum / zinc alloy powder were added to a 500ml high-pressure reactor, and after nitrogen replacement was performed 5 times, the temperature in the reactor was raised to 200°C and maintained for 2 hours; thereafter, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were used to replace the temperature 5 times each; ethylene and hydrogen chloride were used to prepare ethylene composite gas, wherein the volume fraction of ethylene was 85%, the volume fraction of hydrogen chloride was 10%, and the volume fraction of ammonia was 5%, and the prepared ethylene composite gas was introduced into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 160°C, and the ethylene composite gas was continuously introduced to maintain the reaction pressure at 6MPa, and the reaction was performed for 2.5 hours; finally, the temperature was lowered, the pressure was released, and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 98.3%.

[0040] Example 5

[0041] 300g toluenediamine and 15g aluminum / zinc alloy powder were added to a 500ml high-pressure reactor, and after nitrogen replacement was performed 5 times, the temperature in the reactor was raised to 200°C and maintained for 2 hours; then, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were used to replace 5 times respectively; ethylene and hydrogen chloride were used to prepare ethylene composite gas, wherein the volume fraction of ethylene was 85% and the volume fraction of hydrogen chloride was 15%, and the prepared ethylene composite gas was introduced into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 160°C, and ethylene composite gas was continuously introduced to maintain the reaction pressure at 6MPa, and the reaction was performed for 2.5 hours; finally, the temperature was lowered, the pressure was released, and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 97.5%.

[0042] Example 6

[0043] 300g toluenediamine, 15g zinc powder and 15g anhydrous aluminum chloride were added to a 500ml high-pressure reactor, and after nitrogen replacement for 5 times, the temperature was raised and stirred, and the temperature in the reactor was raised to 205°C and maintained for 1.5 hours; then, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were replaced for 5 times respectively; ethylene and ammonia were used to prepare ethylene composite gas, wherein the volume fraction of ethylene was 85% and the volume fraction of ammonia was 15%, and the prepared ethylene composite gas was introduced into the reactor to raise the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 170°C, and ethylene composite gas was continuously introduced to maintain the reaction pressure at 5MPa, and the reaction was carried out for 3 hours; finally, the temperature was lowered, the pressure was released, and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was 96.8%.

[0044] Comparative Example 1

[0045] 300g toluenediamine, 3g aluminum powder, 3g zinc powder and 3g anhydrous aluminum chloride were added to a 500ml high-pressure reactor, and after nitrogen replacement for 5 times, the temperature was raised and stirred, and the temperature in the reactor was raised to 205°C and maintained for 1.5 hours; then, cooling water was passed to reduce the temperature in the reactor to 100-120°C, and nitrogen and ethylene were replaced for 5 times respectively; ethylene was introduced into the reactor to increase the pressure in the reactor to 3-4MPa; then, the temperature was raised and stirred, the temperature in the reactor was maintained at 160°C, and ethylene composite gas was continuously introduced to maintain the reaction pressure at 5MPa, and the reaction was carried out for 2 hours; finally, the temperature was lowered, the pressure was released, and the material was discharged to obtain a DETDA reaction solution. According to chromatographic analysis and calculation, the total yield of the product DETDA was only 72.1%.

Claims

1. A method for preparing diethyltoluenediamine, characterized in that: The steps include: (1) Adding toluenediamine and Lewis acid catalyst into the kettle, and then replacing with nitrogen; (2) heating the reactor to 200-250° C. and stirring for 1-5 hours to form a catalytic system; (3) After the temperature of the reactor drops to 100-120°C, nitrogen and ethylene are used for replacement in sequence, and then ethylene composite gas is introduced into the reactor; (4) After the reactor is heated to 150-200° C., ethylene composite gas is continuously introduced, the reaction pressure is maintained at 5-8 MPa, and the reaction is carried out for 2-5 hours; (5) cooling, releasing pressure, and discharging to obtain a DETDA reaction solution; The ethylene composite gas comprises the following components in volume fractions: The volume fraction of ethylene is 80-99%, the volume fraction of protonic acid gas is 0-20%, the volume fraction of ammonia gas is 0-20%, and the volume fraction of reaction inert gas is 0-15%, wherein the volume fraction of ammonia gas is not zero.

2. The method according to claim 1, characterized in that The added amount of the Lewis acid catalyst is 1 to 10% of the mass of toluenediamine.

3. The method according to claim 2, characterized in that The added amount of the Lewis acid catalyst is 2-5% of the mass of toluenediamine.

4. The method according to claim 1 or 2, characterized in that: In the step (1), the Lewis acid catalyst is one or more of aluminum powder, zinc powder, aluminum / zinc alloy, aluminum chloride, and aluminum alkylate.

5. The method according to claim 1, characterized in that In the step (2), the temperature for forming the catalyst system is 200 to 220° C. and the time is 1 to 2 hours.

6. The method according to any one of claims 1 to 3, characterized in that: The ethylene composite gas comprises the following components in volume fractions: The volume fraction of ethylene is 85-95%; the volume fraction of protonic acid gas is 2-5%; the volume fraction of ammonia gas is 2-5%; and the volume fraction of reaction inert gas is 1-10%.

7. The method according to any one of claims 1 to 3, characterized in that: In the ethylene composite gas, the volume fractions of the protonic acid gas and the ammonia gas are not zero.

8. The method according to any one of claims 1 to 3, characterized in that: The protonic acid gas includes one or more of hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen sulfide, and fluorosilicic acid gas.

9. The method according to any one of claims 1 to 3, characterized in that: The ammonia gas includes one or more of ammonia, monomethylamine, dimethylamine, and trimethylamine.

10. The method according to any one of claims 1 to 3, characterized in that: The reaction inert gas includes one or more of nitrogen, helium, argon, krypton, xenon, and radon.

11. The method according to any one of claims 1 to 3, characterized in that: In step (4), the reaction temperature is 160-170° C., the reaction pressure is 5-6 MPa, and the reaction time is 2-3 hours.

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