Process for the preparation of dicyclohexylamine

Abstract

The application discloses a preparation method of dicyclohexylamine. The dicyclohexylamine is prepared by hydrogenation reaction of raw material aniline and hydrogen, wherein the raw material aniline and / or the hydrogen contains ammonia and cyclohexane derivatives. The method can reduce the content of by-products such as biphenyl, bicyclohexane and phenylcyclohexane in the reaction process, thereby reducing the separation difficulty and obtaining a high-purity DCHA product.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing dicyclohexylamine. Background Technology

[0002] Dicyclohexylamine (DCHA) is an important organic chemical intermediate widely used in dye intermediates, rubber accelerators, nitrocellulose lacquer, pesticides, preservatives, and vapor phase corrosion inhibitors. The main synthetic routes for DCHA include diphenylamine hydrogenation, cyclohexanone-cyclohexylamine condensation hydrogenation, cyclohexylamine bicondensation, and aniline hydrogenation. Among these, the diphenylamine hydrogenation and cyclohexylamine bicondensation methods are not economically viable due to high raw material costs. While the cyclohexanone-cyclohexylamine condensation hydrogenation method can produce DCHA in relatively high yields, the intermediate Schiff base is difficult to separate and prone to decomposition during separation, resulting in lower product quality. Therefore, the current mainstream production method for DCHA is the aniline hydrogenation method, but this mainly produces a byproduct of cyclohexylamine production from aniline hydrogenation, resulting in a lower product quality.

[0003] The main impurities in DCHA products are low-boiling-point substances, Schiff bases, and high-boiling-point substances. Among these, biphenyl, dicyclohexane, and phenylcyclohexane, which are low-boiling-point substances, are difficult to separate due to their boiling points being very close to those of DCHA, posing a pressing problem for the industry. Developing a new method for preparing dicyclohexylamine that can reduce the total content of biphenyl, dicyclohexane, and phenylcyclohexane in DCHA production and improve the quality of dicyclohexylamine products is of great significance. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for preparing dicyclohexylamine, which can reduce the content of by-products such as biphenyl, bicyclohexane, and phenylcyclohexane during the reaction process, thereby reducing the separation difficulty and obtaining high-purity DCHA products.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for synthesizing dicyclohexylamine (DCHA) involves reacting aniline and hydrogen with hydrogen to prepare dicyclohexylamine, wherein the aniline and / or hydrogen contain ammonia and / or cyclohexane derivatives.

[0007] Preferably, the raw material hydrogen contains ammonia.

[0008] Preferably, aniline contains a cyclohexane derivative.

[0009] Preferably, the ammonia can be one or more of ammonia gas, ammonia water, and liquid ammonia; the cyclohexane derivative includes one or more of cyclohexanol, cyclohexylamine, phenylcyclohexylamine, N-cyclohexylenecyclohexylamine, and N-cyclohexyleneaniline.

[0010] The hydrogenation reaction of aniline produces byproducts such as benzene, cyclohexane, and cyclohexene. Under high-temperature conditions, these byproducts can further condense to form biphenyl, dicyclohexane, and phenylcyclohexane. The higher the reaction temperature or local hotspot temperature, the more likely these side reactions will occur. By adding ammonia, especially ammonia gas, to the feedstock, the formation of deamination byproducts such as cyclohexane, cyclohexene, and benzene can be reduced, thus avoiding the formation of condensation products such as biphenyl, phenylcyclohexane, and dicyclohexane. Furthermore, ammonia gas, under the action of a catalyst, will undergo an amination reaction with cyclohexene, further converting it into the main product CHA.

[0011] The main and secondary reaction routes are illustrated below:

[0012]

[0013] On the other hand, introducing cyclohexanol, cyclohexylamine, phenylcyclohexylamine, N-cyclohexylenecyclohexylamine, etc. into the raw materials can cause amination reactions with the raw materials or intermediate products (as shown below). The heat of reaction is low, which will reduce the exothermic power to a certain extent, thereby reducing local hot spots and avoiding the formation of high-temperature byproducts such as biphenyl. In addition, the products of the reaction between these additives and the raw materials are mainly cyclohexylamine and dicyclohexylamine, which will not introduce new byproducts and has certain economic advantages.

[0014] The reaction route is shown below:

[0015]

[0016] In this invention, the hydrogenation reaction of aniline and hydrogen is a gas-phase hydrogenation reaction.

[0017] Preferably, the molar ratio of hydrogen to aniline is (5-20):1, and more preferably (8-15):1;

[0018] Preferably, the reaction temperature is 140–220°C, more preferably 150–170°C; the reaction pressure is 50–1000 kPaG, more preferably 100–500 kPaG; and the aniline feed mass hourly space velocity is 0.1–0.5 h⁻¹. -1 The preferred airspeed is 0.2–0.3 h / h. -1 .

[0019] Preferably, the ammonia content is 0.01 to 10 mol% of the molar weight of hydrogen, more preferably 0.1 to 5 mol%; the cyclohexane derivative content is 0.1 to 50 wt% of the mass of aniline, more preferably 1 to 10 wt%.

[0020] Preferably, the hydrogenation reaction of aniline with hydrogen is carried out in the presence of a hydrogenation catalyst.

[0021] Preferably, the hydrogenation catalyst is selected from supported nickel catalysts or Raney nickel catalysts, with supported nickel catalysts being preferred; the support is selected from one or more of alumina, silica, and diatomaceous earth;

[0022] Preferably, the nickel loading is 10–70 wt% based on the total mass of the catalyst.

[0023] Preferably, the mother liquor obtained from the aniline hydrogenation reaction can be purified by a dehydrogenation tower to remove light components and a refining tower to obtain DCHA products.

[0024] Preferably, the top extraction temperature of the light-light removal tower is 66–85°C and the pressure is 1–5 kPaA, more preferably 77–78°C and 1–2 kPaA; the top extraction temperature of the refining tower is 100–124°C and the pressure is 0.7–2 kPaA, more preferably 107–108°C and 1–1.1 kPaA.

[0025] The method of this invention can reduce the content of by-products and increase the content and purity of the main product, dicyclohexylamine, without introducing new processes. It is simple to operate, highly practical, and the total content of dicyclohexylamine biphenyl, phenylcyclohexane, and bicyclohexane in the prepared product is significantly reduced, resulting in a significant improvement in product quality. Detailed Implementation

[0026] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0027] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0028] Raw material source:

[0029]

[0030]

[0031] The gas chromatographic analysis conditions for the reaction solution components in the following examples were as follows: Agilent DB-5 column, injection port temperature 280°C, FID detector temperature 300°C, column flow rate 1.5 ml / min, hydrogen flow rate 30 ml / min, air flow rate 400 ml / min, and the temperature program was 50°C held for 2 min, then increased to 80°C at 5°C / min, and then increased to 280°C at 15°C / min and held for 10 min.

[0032] Hydrogenation reactor parameters: tube length 1000mm, inner diameter 38mm, wall thickness 5mm, heated by electric heating jacket.

[0033] Distillation unit parameters: column height 700mm, inner diameter 30mm, θ-ring packing, theoretical number of trays 30, bottom feed and intermittent distillation.

[0034] Example 1

[0035] Gas-phase hydrogenation reaction: 50g of 4500T Xunkai catalyst was packed into a reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 150℃, and hydrogen and aniline were introduced into the reactor at a molar ratio of 15:1. Ammonia was simultaneously introduced into the hydrogen to maintain an ammonia concentration of 2mol%. Additionally, 2%, 1%, 1%, and 0.5% (by weight of aniline) of cyclohexanol, cyclohexylamine, N-phenylcyclohexylamine, and N-cyclohexylenecyclohexylamine were added to the aniline, respectively. The reaction temperature was maintained at 150℃, the pressure at 200kPaG, and the aniline mass hourly space velocity (WHSV) at 0.25h. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 94.5% DCHA and approximately 0.09% total biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0036] Post-processing: The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 1 kPaA, and the column top temperature was ≤77℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1.1 kPaA. The fraction with a column top temperature of 108℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.91% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 95 ppm.

[0037] Example 2

[0038] Gas-phase hydrogenation reaction. 50g of Konner K5572 catalyst was packed into a reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 160℃, and hydrogen and aniline were introduced into the reactor at a molar ratio of 12:1. Simultaneously, ammonia was introduced into the hydrogen to maintain an ammonia concentration of 5mol%. Additionally, 0.5%, 0.5%, 0.2%, and 0.3% (by weight of aniline) of cyclohexanol, cyclohexylamine, N-phenylcyclohexylamine, and N-cyclohexylenecyclohexylamine were added to the aniline, respectively. The reaction temperature was maintained at 160℃, the pressure at 180kPaG, and the aniline mass hourly space velocity (WHSV) at 0.30h. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 94.3% DCHA and approximately 0.11% total biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0039] Post-processing. The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 1.5 kPaA, and the column top temperature was ≤77.7℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1 kPaA. The fraction with a column top temperature of 107℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.90% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 143 ppm.

[0040] Example 3

[0041] Gas-phase hydrogenation reaction. 50g of Konner K5241 catalyst was packed into a reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 170℃, and hydrogen and aniline were introduced into the reactor at a molar ratio of 8:1. Simultaneously, ammonia was introduced into the hydrogen to maintain an ammonia concentration of 0.1 mol%. Additionally, 5%, 3%, 1%, and 1% (by weight of aniline) of cyclohexanol, cyclohexylamine, N-phenylcyclohexylamine, and N-cyclohexylenecyclohexylamine were added to the aniline, respectively. The reaction temperature was maintained at 170℃, the pressure at 160 kPaG, and the aniline mass hourly space velocity (WHSV) at 0.20 h⁻¹. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 94.1% DCHA and approximately 0.12% total biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0042] Post-processing. The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 2 kPaA, and the column top temperature was ≤78℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1.05 kPaA. The fraction with a column top temperature of 108℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.93% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 198 ppm.

[0043] Example 4

[0044] Gas-phase hydrogenation reaction. 50g of Ruiyi Ni9005 catalyst was packed into a reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 165℃, and hydrogen and aniline were introduced into the reactor at a molar ratio of 10:1. Simultaneously, ammonia was introduced into the hydrogen to maintain an ammonia concentration of 4 mol%. Additionally, 3% and 2% (by weight of aniline) of cyclohexanol and cyclohexylamine (by mass of aniline) were added to the aniline, respectively. The reaction temperature was maintained at 165℃, the pressure at 170 kPaG, and the aniline mass hourly space velocity (WHSV) at 0.28h. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 94.1% DCHA and approximately 0.13% total biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0045] Post-processing. The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 1.5 kPaA, and the column top temperature was ≤77℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1 kPaA. The fraction with a column top temperature of 107℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.90% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 201 ppm.

[0046] Example 5

[0047] Gas-phase hydrogenation reaction. 50g of Konner K5241 catalyst was packed into a reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 155℃, and hydrogen and aniline were introduced into the reactor at a molar ratio of 13:1. Simultaneously, ammonia was introduced into the hydrogen to maintain an ammonia concentration of 5 mol%. Additionally, 5% cyclohexanol (based on the mass of aniline) was added to the aniline. The reaction temperature was maintained at 155℃, the pressure at 190 kPaG, and the aniline mass hourly space velocity (WHSV) at 0.25h. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 93.9% DCHA and approximately 0.14% total biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0048] Post-processing. The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 1.5 kPaA, and the column top temperature was ≤77℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1 kPaA. The fraction with a column top temperature of 107℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.90% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 162 ppm.

[0049] Example 6

[0050] Gas-phase hydrogenation reaction: 50g of 4500T Xunkai catalyst was packed into the reaction tube and activated at 390℃ under pure hydrogen conditions for 24h. After activation, the reactor was cooled to 150℃. Circulating hydrogen and recovered aniline were introduced into the reactor at a molar ratio of 15:1. The circulating hydrogen was the recycle gas after gas-liquid separation from the hydrogenation reaction, containing approximately 4.6 mol% ammonia. The recovered aniline was a mixture of the top component from the light-light product removal tower and fresh aniline, consisting of 97% aniline, 2% cyclohexanol, and 1% cyclohexylamine. The reaction temperature was maintained at 150℃, the pressure at 200 kPaG, and the aniline mass hourly space velocity (WHSV) at 0.25h. -1 After 24 hours of reaction, samples were taken for GC analysis. The mother liquor contained 94.4% DCHA and approximately 0.11% total content of biphenyl, bicyclohexane, and phenylcyclohexane. The mother liquor requires further post-processing.

[0051] Post-processing: The mother liquor was subjected to light component removal and purification. The light component removal operation pressure was controlled at 1 kPaA, and the column top temperature was ≤77℃, separating light components such as benzene, cyclohexane, and cyclohexylamine. The bottom fraction obtained from the light component removal was purified, with the purification operation pressure controlled at 1.1 kPaA. The fraction with a column top temperature of 108℃ was collected, yielding the DCHA product. GC analysis showed that the product contained 99.91% DCHA, and the total content of biphenyl, bicyclohexane, and phenylcyclohexane was 105 ppm.

[0052] Comparative Example 1

[0053] Compared with Example 2, the present invention differs in that the hydrogen in Comparative Example 1 does not contain ammonia and the aniline does not contain cyclohexane derivatives.

[0054] GC analysis showed that the mother liquor contained 92.7% DCHA and approximately 0.55% total biphenyl, bicyclohexane, and phenylcyclohexane. After further light removal and purification, the product contained 99.68% DCHA and 2146 ppm total biphenyl and other compounds.

[0055] Comparative Example 2

[0056] The difference between this invention and Example 2 is that the aniline in Comparative Example 2 does not contain cyclohexane derivatives.

[0057] GC analysis showed that the mother liquor contained 93.1% DCHA and approximately 0.42% total biphenyl, bicyclohexane, and phenylcyclohexane. After further processing to remove light components and refining, the product contained 99.75% DCHA and 1143 ppm total biphenyl and other components.

[0058] Comparative Example 3

[0059] The difference between this invention and Example 2 is that the hydrogen in Comparative Example 3 does not contain ammonia.

[0060] GC analysis showed that the mother liquor contained 93.5% DCHA and approximately 0.45% total biphenyl, bicyclohexane, and phenylcyclohexane. After further processing to remove light components and refining, the product contained 99.71% DCHA and 1532 ppm total biphenyl and other components.

[0061] The main reaction conditions and results of the examples and comparative examples are shown in the table below:

[0062]

[0063] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for synthesizing dicyclohexylamine, characterized in that, Dicyclohexylamine is prepared by hydrogenation reaction of aniline and hydrogen, wherein the aniline and / or hydrogen contain ammonia and cyclohexane derivatives. The cyclohexane derivatives include cyclohexanol, cyclohexylamine, phenylcyclohexylamine, and N-cyclohexenecyclohexylamine; The ammonia content is 0.01~10 mol% of the molar weight of hydrogen, and the cyclohexane derivative content is 0.1~50 wt% of the mass of aniline. The hydrogenation reaction of aniline with hydrogen is carried out in the presence of a hydrogenation catalyst, which is selected from a supported nickel catalyst or a Raney nickel catalyst.

2. The synthesis method according to claim 1, characterized in that, The raw material hydrogen contains ammonia.

3. The synthesis method according to claim 1, characterized in that, Aniline contains cyclohexane derivatives.

4. The synthesis method according to claim 1, characterized in that, The ammonia is one or more of ammonia gas, ammonia water, and liquid ammonia.

5. The synthesis method according to claim 1, characterized in that, The hydrogenation reaction of aniline and hydrogen is a gas-phase hydrogenation reaction.

6. The synthesis method according to claim 1, characterized in that, The molar ratio of hydrogen to aniline is (5~20):

1.

7. The synthesis method according to claim 6, characterized in that, The molar ratio of hydrogen to aniline is (8~15):

1.

8. The synthesis method according to claim 1, characterized in that... The reaction temperature is 140~220℃, the reaction pressure is 50~1000kPaG, and the aniline feed mass hourly space velocity is 0.1~0.5h-1.

9. The synthesis method according to claim 8, characterized in that... The reaction temperature is 150~170℃; the reaction pressure is 100~500kPaG; and the aniline feed mass hourly space velocity is 0.2~0.3h-1.

10. The synthesis method according to claim 1, characterized in that, The ammonia content is 0.1 to 5 mol of hydrogen molar weight; the cyclohexane derivative content is 1 to 10 wt% of aniline mass.

11. The synthesis method according to claim 1, characterized in that, The hydrogenation catalyst is a supported nickel catalyst; the support is selected from one or more of alumina, silica, and diatomaceous earth.

12. The synthesis method according to claim 1 or 11, characterized in that, Based on the total mass of the catalyst, the nickel loading is 10~70wt%.

13. The synthesis method according to claim 1, characterized in that, The mother liquor obtained from the hydrogenation reaction of aniline is then purified by a dehydrogenation tower to remove light components and a refining tower to obtain DCHA product.

14. The synthesis method according to claim 13, characterized in that, The top temperature of the light-light removal tower is 66~85℃ and the pressure is 1~5kPaA; the top temperature of the refining tower is 100~124℃ and the pressure is 0.7~2kPaA.

15. The synthesis method according to claim 14, characterized in that, The top temperature of the light-light removal tower is 77~78℃ and the pressure is 1~2kPaA; the top temperature of the refining tower is 107~108℃ and the pressure is 1~1.1kPaA.

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