A process for the manufacture of 3-aminomethyl-3,5,5-trimethylcyclohexylamine

Abstract

The present application relates to a kind of preparation methods of 3-aminomethyl-3,5,5-trimethylcyclohexylamine, the preparation method described includes: first isophorone nitrile and liquid ammonia occur imination reaction in the presence of imination catalyst, the obtained imination reaction liquid is mixed with methanol and then enters hydrogenation reactor, and hydrogenation reaction occurs in the presence of hydrogenation catalyst to obtain 3-aminomethyl-3,5,5-trimethylcyclohexylamine.Using the method provided in the present application, relatively low reaction pressure can be used to obtain a reaction solution with a lower content of difficult-to-separate impurities, which reduces the difficulty of separation and reduces the difficulty of separation.In addition, the mixing heat of methanol and liquid ammonia can be used for hydrogenation preheating, reducing energy waste, in line with the current low-carbon development trend, further reducing the operating cost of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for producing 3-aminomethyl-3,5,5-trimethylcyclohexylamine, belonging to the field of organic synthesis. BACKGROUND

[0002] 3-aminomethyl-3,5,5-trimethylcyclohexylamine, abbreviated as IPDA, is a cycloaliphatic diamine, which can be used as a curing agent in epoxy resin production, as a crosslinking agent, coupling agent and hydroxyl stabilizer in polyurethane production, and as a special monomer, and can also be used to prepare the corresponding diisocyanate, isophorone diisocyanate, which is a versatile diisocyanate that is compatible with almost all solvents and all resins, and has the advantages of mild curing conditions, good chemical resistance, heat resistance and water resistance, etc. Moreover, it can be used to produce paints, elastomers, adhesives and special fibers, and can also be used as a basic raw material for organic synthesis.

[0003] The current mainstream production process of IPDA is IPN amination hydrogenation: IPN reacts on a cobalt catalyst in the presence of water and excess ammonia, first generating isophorone nitrile imine IPNI from IPN and ammonia through dehydration, and then hydrogenating IPNI to IPDA:

[0004]

[0005] DuPont (US5491264) and BASF (US5371292A, CN1561260A) have both reported the synthesis process of IPN amination hydrogenation for preparing IPDA. In their patent reports, it can be seen that they use liquid ammonia as the imination reactant and as the hydrogenation reaction solvent at the same time, which has the advantage of not needing to add additional solvents, but has the disadvantage of needing to use a relatively high reaction pressure due to the high ammonia partial pressure in the hydrogenation reaction system.

[0006] Deggusa (US5679860, US4429157A) and Sumitomo (US5395972A, US5589596A) introduce a solvent, methanol, into the reaction system. Due to the presence of the solvent effect, the operating pressure is relatively low, which reduces the material requirement grade and the equipment investment, but at the same time, it is found that due to the introduction of the methanol solvent, a methylated product of IPDA appears in the hydrogenation product, which is difficult to separate from IPDA, increases the energy consumption for separation, and reduces the product quality.

[0007] In summary, the existing methods for preparing IPDA have problems such as high pressure (liquid ammonia as the hydrogenation solvent) or high content of impurities (IPDA methylated product) that are difficult to separate (introduction of methanol as a solvent). SUMMARY

[0008] The application aims to provide a preparation method of IPDA, by which a reaction liquid with low content of difficult-to-separate impurities can be obtained at a relatively low reaction pressure, and the separation difficulty is reduced. In addition, the mixing heat of methanol and liquid ammonia can be used for hydrogenation preheating, energy waste is reduced, the current low-carbon development trend is met, and the operation cost of the device is further reduced.

[0009] Through the research on the synthesis process of IPDA, we found that the causes of N-methylated product and methylated product are the acidity of imination catalyst. The N-methylated product is generated by the methanol and liquid ammonia in the presence of imination catalyst to generate methylamine, the imination reaction of methylamine and IPN in the presence of imination catalyst, and further hydrogenation reaction to generate N-methylated product of IPDA; the methylated product is generated by the alkylation reaction of IPN and methanol in the presence of imination catalyst to generate methylated product of IPN, then the imination reaction with liquid ammonia to generate methylated product of IPNI, and further hydrogenation reaction to generate methylated product of IPDA. The specific reaction process is as follows:

[0010]

[0011] N-methylated product generation process Methylated product generation process

[0012] Since the N-methylated product and the methylated product of IPDA are similar in structure to IPDA, the separation difficulty is large in the actual operation process, so it is necessary to avoid the generation of the two compounds.

[0013] According to our research results, we designed a new feeding scheme, that is, methanol as a solvent was introduced into the system between the imination reactor and the hydrogenation reactor, that is, isophorone nitrile and liquid ammonia were allowed to undergo imination reaction in the presence of imination catalyst, and then the obtained imination reaction liquid was mixed with methanol and then entered the hydrogenation reactor to undergo hydrogenation reaction. This feeding mode can not only utilize the solvent effect of methanol to reduce the reaction pressure, but also avoid the generation of N-methylated product and methylated product in the imination stage, reduce the separation difficulty, and increase the device benefit.

[0014] In addition, the mixing and dissolving of methanol and liquid ammonia releases heat, if methanol is introduced before the imination reaction, because the imination reaction temperature is low, a heat exchanger is needed to remove the heat, and the hydrogenation reaction needs a higher temperature, the imination reaction liquid needs to be heated by a heat exchanger before entering the hydrogenation reactor, so the mixing and dissolving heat of methanol and liquid ammonia is not utilized, causing energy waste. By using the new feeding scheme, the energy can be better utilized, methanol is not introduced into the system before the imination reaction, and a heat exchanger is not needed to remove the heat before the imination reaction, after the imination reaction is completed, the imination reaction and methanol release heat, which can increase the temperature of the imination reaction liquid, so that a heat exchanger is not needed to heat and increase the temperature or a small amount of energy is needed to heat and increase the temperature by using a heat exchanger, the mixing and dissolving heat of methanol and liquid ammonia is fully utilized, energy waste is reduced, which accords with the current low-carbon development trend, and further reduces the operation cost of the device.

[0015] Based on the above research, in order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0016] A method for preparing IPDA, first, isophorone nitrile and liquid ammonia are subjected to imination reaction in the presence of an imination catalyst, the obtained imination reaction liquid is mixed with methanol and then enters a hydrogenation reactor, and hydrogenation reaction occurs in the presence of a hydrogenation catalyst to obtain 3-aminomethyl-3,5,5-trimethylcyclohexylamine.

[0017] In the preparation method of the present application, the imination reaction and the hydrogenation reaction need to be completed in two independent reaction vessels (referred to as imination reactor and hydrogenation reactor, respectively).

[0018] In the preparation method of the present application, the imination reaction needs at least one imination catalyst, and the reaction is carried out under solvent-free conditions.

[0019] The imination catalyst can be an acidic metal oxide, preferably active alumina or titanium oxide.

[0020] The treatment capacity of the imination catalyst is 0.01-0.5 g IPN / (g catalyst·hour), preferably 0.05-0.2 g IPN / (g catalyst·hour).

[0021] The mass ratio of liquid ammonia to IPN is 2-50:1, preferably 3-10:1.

[0022] The imination reaction conditions are: 20-100℃, 5-20 MPa.

[0023] According to our research, the generation rate of N-methylated product and methylated product of IPDA is positively correlated with the imidization reaction temperature, thus, in the current production process, in order to inhibit the content of N-methylated product and methylated product of IPDA in the reaction solution, the imidization reaction temperature is preferably 20-40°C. In the preparation method of the present application, since methanol is not introduced in the imidization stage, the imidization temperature range can be wider.

[0024] Further, in a specific embodiment, the imidization reaction is carried out in a fixed bed packed with imidization catalyst, and the mixture of IPN and liquid ammonia continuously passes through the fixed bed packed with imidization catalyst from bottom to top to obtain an imidization reaction solution.

[0025] In the preparation method of the present application, the methanol is introduced into the system between the imidization reactor and the hydrogenation reactor as a hydrogenation solvent,

[0026] The mass ratio of methanol to imidization reaction solution is 0.5-10:1, preferably 1-3:1;

[0027] The synthesis process of IPDA prepared by IPN ammoniation hydrogenation is a technology well known to those skilled in the art, and the hydrogenation catalyst used is mainly a nickel-based or cobalt-based catalyst selected from a supported catalyst or a Raney catalyst or a combination of the two, wherein the supported catalyst is a catalyst in which active metals nickel and / or cobalt are supported on a carrier framework, and the carrier is preferably one or more of Al2O3, diatomite, SiO2, and MgO, and the active metal loading is preferably 30-50%; preferably, the catalyst is a supported catalyst. Since the occurrence of methylation reaction needs to be inhibited in the hydrogenation reaction, the catalyst carrier is preferably a neutral or weakly basic carrier;

[0028] The mass of the hydrogenation catalyst is 1-3 times the mass of the imidization catalyst;

[0029] The conditions of the hydrogenation reaction are 90-160°C and 5-20 MPa.

[0030] Further, in a specific embodiment, the hydrogenation reaction is carried out in a fixed bed packed with hydrogenation catalyst, and the mixture of imidization reaction solution and methanol passes through the fixed bed packed with hydrogenation catalyst from top to bottom.

[0031] In the preparation method of the present application, the hydrogenation reaction solution can obtain IPDA product after separation and purification. In a specific embodiment, the specific separation step is that the hydrogenation reaction solution is first completely or partially separated from hydrogen, inert gas, ammonia, methanol, low-boiling-point impurities, and part of water in one or more rectifying columns, wherein the methanol and liquid ammonia can be recycled; other low-boiling-point impurities, water, and high-boiling-point impurities are completely or partially separated in the rectifying column, and IPDA is obtained.

[0032] By using the preparation method of the present application, the content of IPDA methylation product in the hydrogenation reaction liquid can be ≤10 ppm, and the IPDA methylation product includes N-methylation product (see structural formula I for a representative structure) and methylation product (see structural formula II for a representative structure):

[0033]

[0034] Compared with the prior art, the beneficial effects of the preparation method of the present application mainly include:

[0035] 1) The present application innovatively introduces methanol as a hydrogenation solvent into the system between the imination reactor and the hydrogenation reactor, which not only utilizes the solvent effect of methanol to reduce the reaction pressure, but also avoids the generation of N-methylation product and methylation product in the imination stage, thereby reducing the difficulty of product separation.

[0036] 2) The mixing and dissolution heat of methanol and liquid ammonia is fully utilized, which reduces energy waste and conforms to the current low-carbon development trend.

[0037] 3) The present application can efficiently convert IPN to IPDA at a lower pressure, and the reaction conversion rate can reach 99.9%, the selectivity is not less than 98.0% (calculated based on IPN), and the content of IPDA methylation product is not more than 10 ppm. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a process flow chart for preparing IPDA according to the present application. DETAILED DESCRIPTION

[0039] The present application will be further described below in conjunction with examples, and it should be noted that the examples do not constitute a limitation on the scope of protection required by the present application.

[0040] The main raw materials involved in the present application are obtained by commercial purchase.

[0041] The test instrument used in this example is: GC using Agilent7820 test, and the sample is diluted 3 times with chromatographic methanol.

[0042] Example 1

[0043] As shown in the accompanying Figure 1 , the imination reactor and the hydrogenation reactor use a fixed bed with a diameter of 25 mm and a length of 1000 mm, wherein the imination reactor is filled with 100 g of active alumina beads (purchased from Dalian Haixin), and the hydrogenation reactor is filled with 200 g of cobalt catalyst supported on Al2O3 (purchased from Zhongchuang Catalyst, support Al2O3, loading amount 40%).

[0044] The raw material IPN and liquid ammonia were mixed and continuously fed into the imidization reactor at a feed rate of 20 g / h, the mass ratio of liquid ammonia to IPN was 3:1, the imidization reaction temperature was controlled at 30°C, and the reaction pressure was 12 MPa. The imidization reaction liquid obtained at the outlet of the imidization reactor was mixed with methanol and then fed into the hydrogenation reactor, the mass ratio of methanol to imidization reaction liquid was 1:1, the hydrogenation reaction temperature was controlled at 130°C, and the reaction pressure was 12 MPa. GC analysis was performed during the feeding, and the reaction reached equilibrium after 20 h. The conversion rate of IPN ammoniation hydrogenation to generate IPDA was 99.99%, the selectivity of IPDA was 98.04%, and no IPDA methylation product was detected.

[0045] Example 2

[0046] The reactor and the catalyst were the same as in Example 1.

[0047] The raw material IPN and liquid ammonia were mixed and continuously fed into the imidization reactor at a feed rate of 70 g / h, the mass ratio of liquid ammonia to IPN was 5:1, the imidization reaction temperature was controlled at 40°C, and the reaction pressure was 15 MPa. The imidization reaction liquid obtained at the outlet of the imidization reactor was mixed with methanol and then fed into the hydrogenation reactor, the mass ratio of methanol to imidization reaction liquid was 2:1, the hydrogenation reaction temperature was controlled at 130°C, and the reaction pressure was 15 MPa. GC analysis was performed during the feeding, and the reaction reached equilibrium after 20 h. The conversion rate of IPN ammoniation hydrogenation to generate IPDA was 99.99%, the selectivity of IPDA was 98.12%, and no IPDA methylation product was detected.

[0048] Example 3

[0049] The reactor and the catalyst were the same as in Example 1.

[0050] The raw material IPN and liquid ammonia were mixed and continuously fed into the imidization reactor at a feed rate of 40 g / h, the mass ratio of liquid ammonia to IPN was 10:1, the imidization reaction temperature was controlled at 30°C, and the reaction pressure was 13 MPa. The imidization reaction liquid obtained at the outlet of the imidization reactor was mixed with methanol and then fed into the hydrogenation reactor, the mass ratio of methanol to imidization reaction liquid was 3:1, the hydrogenation reaction temperature was controlled at 120°C, and the reaction pressure was 13 MPa. GC analysis was performed during the feeding, and the reaction reached equilibrium after 20 h. The conversion rate of IPN ammoniation hydrogenation to generate IPDA was 99.99%, the selectivity of IPDA was 98.37%, and no IPDA methylation product was detected.

[0051] Example 4

[0052] The reactor and the imidization catalyst were the same as in Example 1, except that the hydrogenation catalyst was replaced with Raney cobalt catalyst (purchased from Grace).

[0053] The raw material IPN and liquid ammonia were mixed and continuously fed into the imidization reactor at a feed rate of 100 g / h, the mass ratio of liquid ammonia to IPN was 4:1, the imidization reaction temperature was controlled at 50°C, and the reaction pressure was 14 MPa. The imidization reaction liquid obtained from the outlet of the imidization reactor was mixed with methanol and then fed into the hydrogenation reactor, the mass ratio of methanol to imidization reaction liquid was 2:1, the hydrogenation reaction temperature was controlled at 130°C, and the reaction pressure was 14 MPa. GC analysis was performed during the feeding process, and the reaction reached equilibrium after 20 h. The conversion rate of IPN ammoniation hydrogenation to generate IPDA was 99.99%, the selectivity of IPDA was 98.21%, and no IPDA methylation product was detected.

[0054] Comparative Example 1

[0055] The reactor and catalyst were the same as in Example 1, except that the methanol was mixed with the IPN and liquid ammonia in advance, and the temperature was increased by about 25°C after mixing. The temperature was reduced to 30°C by a heat exchanger.

[0056] The raw material IPN, liquid ammonia and methanol were mixed and continuously fed into the imidization reactor at a feed rate of 40 g / h, the mass ratio of liquid ammonia, IPN and methanol was 3:1:4, the imidization reaction temperature was controlled at 30°C, and the reaction pressure was 12 MPa. The imidization reaction liquid obtained from the outlet of the imidization reactor was fed into the hydrogenation reactor, the hydrogenation reaction temperature was controlled at 130°C, and the reaction pressure was 12 MPa. GC analysis was performed during the feeding process, and the reaction reached equilibrium after 9 h. The conversion rate of IPN ammoniation hydrogenation to generate IPDA was 99.99%, the selectivity of IPDA was 97.23%, and the content of IPDA methylation product was 0.785%.

Claims

1. A method for preparing 3-aminomethyl-3,5,5-trimethylcyclohexylamine, comprising: Isophorone nitrile and liquid ammonia undergo an imidization reaction in the presence of an imidization catalyst. The resulting imidized reaction solution is mixed with methanol and then fed into a hydrogenation reactor, where a hydrogenation reaction occurs in the presence of a hydrogenation catalyst to yield 3-aminomethyl-3,5,5-trimethylcyclohexylamine.

2. The method according to claim 1, characterized in that, The iminolation reaction was carried out under solvent-free conditions.

3. The method according to claim 1 or 2, characterized in that, The imidization catalyst is an acidic metal oxide.

4. The method according to claim 3, characterized in that, The iminoization catalyst is active alumina and / or titanium oxide.

5. The method according to claim 3, characterized in that, The imidization reaction is carried out with a catalyst loading of 0.01–0.5 g isophorone nitrile / (g catalyst·hour).

6. The method according to claim 1, characterized in that, The mass ratio of liquid ammonia to isophorone nitrile is 2 to 50:

1.

7. The method according to claim 1, characterized in that, The mass ratio of liquid ammonia to isophorone nitrile is 3 to 10:

1.

8. The method according to any one of claims 1-2, characterized in that, The conditions for the imidization reaction are: 20–100℃ and 5–20 MPa.

9. The method according to claim 1 or 6, characterized in that, The mass ratio of methanol to imidization reaction solution is 0.5 to 10:

1.

10. The method according to claim 9, characterized in that, The mass ratio of methanol to imidization reaction solution is 1 to 3:

1.

11. The method according to claim 1, characterized in that, Hydrogenation catalysts include nickel-based and / or cobalt-based catalysts, selected from supported catalysts and Raney catalysts.

12. The method according to claim 11, characterized in that, The support for the catalyst is one or more of Al2O3, diatomaceous earth, SiO2, and MgO, and the active metal loading is 30-50%.

13. The method according to any one of claims 1, 11-12, characterized in that, The mass of the hydrogenation catalyst is 1 to 3 times the mass of the imidization catalyst.

14. The method according to claim 1, characterized in that, The conditions for the hydrogenation reaction are: 90–160 °C and 5–20 MPa.

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