Method for obtaining cyclohexylamine and dicyclohexylamine by distillation and purification of crude amine obtained by cyclohexanol amination process

Abstract

This invention belongs to the field of distillation purification, specifically disclosing a method for distilling and purifying crude amine obtained by hexanol amination to obtain cyclohexylamine and dicyclohexylamine. The method includes the following steps: the crude amine is condensed and then fed into an ammonia tower for processing; the residue from the ammonia tower bottom is fed into a No. 1 cyclohexylamine dehydration tower for distillation; the azeotrope I of cyclohexylamine and water is collected from the top of the No. 1 cyclohexylamine dehydration tower and fed into a pressurized recovery tower for pressurized distillation; the residue from the bottom of the No. 1 cyclohexylamine dehydration tower is fed into a cyclohexylamine tower for distillation purification of the cyclohexylamine product; cyclohexylamine, the product, is collected from the top of the cyclohexylamine tower; the residue from the bottom of the cyclohexylamine tower is fed into a dealcoholization tower for dealcoholization; the residue from the bottom of the dealcoholization tower is fed into a dicyclohexylamine tower for distillation recovery purification of the dicyclohexylamine product. This invention eliminates the need for a dehydrating agent, successfully separating water based on the difference in water content in the azeotropic composition during pressurized distillation, and obtaining high-content cyclohexylamine and dicyclohexylamine.

Description

Technical Field

[0001] This invention belongs to the field of distillation and purification, specifically relating to the distillation and purification process for preparing cyclohexylamine and dicyclohexylamine by the amination of cyclohexanol. Background Technology

[0002] Cyclohexylamine, also known as hexahydroaniline, is an important chemical organic intermediate. It is an organic compound, a colorless liquid with a strong ammonia odor, and exhibits strong organic base properties.

[0003] Cyclohexyl alcohol amination process produces cyclohexylamine and dicyclohexylamine, yielding crude products (crude amines). These crude products (crude amines) contain cyclohexylamine, dicyclohexylamine, water, impurities, and unreacted cyclohexyl alcohol and liquid ammonia. Cyclohexylamine and dicyclohexylamine are the target products, while water is the main reaction byproduct.

[0004] The crude amine was deaminated and then dehydrated, followed by vacuum distillation to collect the purified cyclohexylamine and dicyclohexylamine. According to literature, the azeotropic temperature of cyclohexylamine and water at atmospheric pressure is 96.4℃, and cyclohexylamine and water are miscible. Although some qualified cyclohexylamine product can be obtained by ordinary distillation to collect the azeotrope, the yield is low, and cyclohexylamine and water cannot be completely separated.

[0005] The article in *Chemical Production and Technology*, 2010, 17(3), 57-61, used cyclohexane as an azeotropic dehydrating agent. The azeotropic temperature of cyclohexane and water was 69℃, and the water content in the azeotropic composition was 8.4%. High-purity cyclohexylamine was obtained through a three-step distillation process involving dehydration, dealkylation, and amine distillation. Although this process yielded a qualified product through distillation purification with added cyclohexane, the addition of cyclohexane increased the cost and introduced impurities inherent in cyclohexane itself.

[0006] In summary, existing distillation processes are limited, and the addition of cyclohexane azeotropic distillation increases costs and introduces cyclohexane impurities; therefore, improvements to the aforementioned existing technologies are necessary. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for obtaining cyclohexylamine and dicyclohexylamine by distillation and purification of crude amine obtained by cyclohexanol amination.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for purifying crude amine obtained by cyclohexanol amination by distillation to obtain cyclohexylamine and dicyclohexylamine. The cyclohexanol amination method is carried out in a reaction vessel to obtain crude amine containing cyclohexylamine and dicyclohexylamine, and includes the following steps:

[0009] S1. Crude amine is condensed and then enters the ammonia tower. The pressure of the ammonia tower is set to 1.28-1.32 MPa, the top temperature is 40-42℃, and the bottom temperature is 170-175℃.

[0010] Ammonia in the crude amine is discharged from the top of the ammonia tower as a gas and then recovered as a reaction feedstock; the product obtained from the bottom of the ammonia tower enters the No. 1 cyclohexylamine dehydration tower for distillation.

[0011] Note: In this step, excess ammonia from the reaction is removed by an ammonia tower and can be returned to the synthesis system;

[0012] S2. Set the pressure of the No. 1 cyclohexylamine dehydration tower to -0.06 to -0.095 MPa (preferably -0.088 to -0.090 MPa), the tower top temperature to 40 to 75°C, and the tower bottom temperature to 90 to 110°C.

[0013] An azeotrope of cyclohexylamine and water (water content approximately 67%–69%) is collected from the top of the No. 1 cyclohexylamine dehydration tower. The azeotrope of cyclohexylamine and water is then fed into a pressurized recovery tower for pressurized distillation. The product obtained from the bottom of the No. 1 cyclohexylamine dehydration tower is fed into the cyclohexylamine tower for distillation and purification of the cyclohexylamine product.

[0014] S3. Set the pressure of the pressurized recovery tower to 0.2-0.8 MPa, the top temperature to 115-175℃, and the bottom temperature to 120-180℃.

[0015] The azeotrope of cyclohexylamine and water II (water content of about 55% to 60%) is collected from the top of the pressurized recovery tower. The azeotrope of cyclohexylamine and water II is returned to the No. 1 cyclohexylamine dehydration tower for further distillation. The wastewater generated in the bottom of the pressurized recovery tower is discharged into the wastewater pool.

[0016] S4. Set the pressure of the cyclohexylamine tower to -0.085 to -0.095 MPa (preferably -0.088 to -0.090 MPa), the top temperature of the tower to 70 to 75°C, and the bottom temperature of the tower to 120 to 135°C.

[0017] Cyclohexylamine (i.e., finished cyclohexylamine product) is collected from the top of the cyclohexylamine tower, and the product obtained from the bottom of the cyclohexylamine tower enters the dealcoholization tower for dealcoholization treatment.

[0018] S5. Set the pressure of the dealcoholization tower to -0.085 to -0.095 MPa (preferably -0.088 to -0.092 MPa), the top temperature of the tower to 100 to 105℃, and the bottom temperature of the tower to 145 to 150℃.

[0019] The cyclohexanol collected from the top of the dealcoholization tower is used as a raw material for recovery, and the product obtained from the bottom of the dealcoholization tower is fed into the dicyclohexylamine tower for distillation recovery and purification of dicyclohexylamine product.

[0020] S6. Set the top pressure of the dicyclohexylamine column to -0.085 to -0.095 MPa (preferably -0.088 to -0.092 MPa), the top temperature to 150 to 152°C, and the bottom temperature to 155 to 162°C.

[0021] The dicyclohexylamine product (i.e., finished dicyclohexylamine) is collected from the top of the dicyclohexylamine tower (T-106). The product obtained from the bottom of the dicyclohexylamine tower is a high-boiling material, which is disposed of as waste.

[0022] As an improvement to the method of the present invention:

[0023] In S1: The recovered ammonia is returned to the synthesis system within the reaction vessel;

[0024] In S5: The recovered cyclohexanol is returned to the synthesis system within the reaction vessel.

[0025] As a further improvement to the method of the present invention:

[0026] Wastewater generated in the pressurized recovery tower is discharged into a wastewater pool;

[0027] The product obtained from the dicyclohexylamine tower bottom is a high-boiling-point material, which is disposed of as waste.

[0028] As a further improvement to the method of the present invention, and as a preferred embodiment:

[0029] In S1, the ammonia tower is set with the following parameters: pressure 1.28~1.32Mpa, tower top temperature 40~41℃, tower bottom temperature 172~174℃;

[0030] In S2, the parameters set for the No. 1 cyclohexylamine dehydration tower are as follows: pressure -0.088 to -0.090 MPa, tower top temperature 44 to 46℃, and tower bottom temperature 95 to 97℃.

[0031] In S3, the process parameters set for the pressurized recovery tower are: pressure 0.48~0.52MPa, tower top temperature controlled at 144~146℃, and tower bottom temperature at 148~152℃.

[0032] In S4, the pressure of the cyclohexylamine tower is controlled at -0.088 to -0.090 MPa, the top temperature is 71 to 72℃, and the bottom temperature is 120 to 122℃.

[0033] In S5, the pressure of the dealcoholization tower is controlled at -0.088 to -0.092 MPa, the top temperature is 100 to 101℃, and the bottom temperature is 148 to 150℃.

[0034] In S6, the top pressure of the dicyclohexylamine column is -0.088 to -0.092 MPa, the top temperature is 150 to 151℃, and the bottom temperature is 157 to 159℃.

[0035] In step S2 of this invention, the pressure of the No. 1 cyclohexylamine dehydration tower (T-102) is -0.06 to -0.095 MPa (preferably -0.088 to -0.090 MPa), and the pressure of the pressurized recovery tower (T-103) is 0.2 to 0.8 MPa (preferably 0.48 to 0.52 MPa), creating a pressure difference between the two towers. This invention eliminates the need for a water-carrying agent, successfully separating water through the difference in water content in the azeotropic composition of pressurized distillation, and obtaining cyclohexylamine with a content ≥99.9% and dicyclohexylamine with a content ≥99.85%.

[0036] This invention uses differential pressure distillation purification process to separate and purify cyclohexylamine and water to obtain qualified cyclohexylamine and dicyclohexylamine products. The separated water can meet the wastewater discharge requirements without further treatment. That is, the wastewater generated in the bottom of the pressurized recovery tower (T-103) can be directly discharged into the wastewater pool.

[0037] In summary, this invention provides an effective treatment method for the crude amines obtained from the amination of cyclohexanol to produce cyclohexylamine and dicyclohexylamine. It employs a method that does not rely on the addition of an azeotropic agent, using distillation to purify cyclohexylamine and dicyclohexylamine. This invention successfully obtains high-yield, high-purity cyclohexylamine products using a simple method. Attached Figure Description

[0038] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0039] Figure 1 This is a schematic diagram of the device of the present invention;

[0040] Figure 2 This is a schematic diagram of the apparatus used in Comparative Example 2. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0042] Example 1: A distillation and purification apparatus, such as... Figure 1 The following is stated:

[0043] This includes ammonia tower T-101, cyclohexylamine dehydration tower T-102, pressurized recovery tower T-103, cyclohexylamine tower T-104, dealcoholization tower T-105, and dicyclohexylamine tower T-106;

[0044] The bottom outlet of ammonia tower T-101 is connected to the feed inlet of cyclohexylamine dehydration tower T-102.

[0045] The top outlet of the No. 1 cyclohexylamine dehydration tower T-102 is connected to the feed inlet of the pressurized recovery tower T-103, and the bottom outlet of the No. 1 cyclohexylamine dehydration tower T-102 is connected to the feed inlet of the cyclohexylamine tower T-104.

[0046] The top outlet of the pressurized recovery tower T-103 is connected to the feed inlet of the No. 1 cyclohexylamine dehydration tower T-102; the bottom outlet of the pressurized recovery tower T-103 is connected to the wastewater pool.

[0047] The bottom outlet of the cyclohexylamine tower T-104 is connected to the feed inlet of the dealcoholization tower T-105, and the bottom outlet of the dealcoholization tower T-105 is connected to the feed inlet of the dicyclohexylamine tower T-106.

[0048] The crude amines obtained by the cyclohexanol amination method used in the following cases are prepared by the cyclohexanol amination method for producing cyclohexylamine and dicyclohexylamine: In a reaction vessel, cyclohexanol and liquid ammonia react under hydrogen conditions, and the crude amines obtained (crude product, at approximately the reaction temperature of 170–175°C) contain the following components (in mass %), as shown in Table 1 below. Cyclohexylamine and dicyclohexylamine are the target products, water (H₂O) is the main reaction byproduct, and cyclohexanol and liquid ammonia are the raw materials that have not yet participated in the reaction.

[0049] Table 1

[0050] name <![CDATA[NH3]]> <![CDATA[H2O]]> Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities crude amine 5.56％ 21.60％ 56.45％ 3.15％ 12.98％ margin

[0051] Example 1: A method for purifying crude amine obtained by the cyclohexanol amination method to obtain cyclohexylamine and dicyclohexylamine by distillation, comprising the following steps:

[0052] S1. Crude amine, after being condensed to ≤60℃ (meeting gas-liquid separation conditions), enters ammonia tower T101. The parameters of ammonia tower T101 are as follows: pressure 1.30 MPa, top temperature 41.2℃, bottom temperature 172.5℃. Therefore, the ammonia in the crude amine is recovered as a gas from the top of ammonia tower T101 and subsequently returned to the synthesis system within the reaction vessel. The product from the bottom of ammonia tower T101 enters the No. 1 cyclohexylamine dehydration tower T-102 for distillation.

[0053] In this step, excess ammonia from the reaction is removed by an ammonia tower and returned to the synthesis system.

[0054] The parameters for S2 and 1# cyclohexylamine dehydration tower T-102 are set as follows: pressure -0.090MPa, tower top temperature 45.5℃, tower bottom temperature 95.5℃.

[0055] The azeotrope I (water content 68.9%) of cyclohexylamine and water, collected from the top of cyclohexylamine dehydration tower T-102, enters pressurized recovery tower T-103. The bottom product of cyclohexylamine dehydration tower T-102 enters cyclohexylamine tower T-104. The composition of the bottom product of cyclohexylamine dehydration tower T-102 is as follows:

[0056] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 76.86％ 4.29％ 17.67％ 1.18％

[0057] The process parameters set for S3 and the pressurized recovery tower T-103 are: pressure 0.50MPa, tower top temperature controlled at 145.2℃, and tower bottom temperature 150.8℃. The cyclohexylamine and water azeotrope II (water content 55.7%) collected from the top of the pressurized recovery tower T-103 are returned to the No. 1 cyclohexylamine dehydration tower T-102. The wastewater obtained from the bottom of the pressurized recovery tower T-103 is discharged into the wastewater pool.

[0058] The wastewater sample is as follows:

[0059]

[0060] Note: Q / JYB G1401.9-2022 sets the wastewater discharge standards as follows:

[0061]

[0062] Therefore, the wastewater generated in this step meets the discharge standards.

[0063] S4. Set the pressure of the cyclohexylamine tower T-104 to -0.090MPa, the top temperature to 71.8℃, and the bottom temperature to 120.9℃.

[0064] Cyclohexylamine product is collected from the top of the T-104 cyclohexylamine tower. The purity of the cyclohexylamine product is ≥99.95%. The residue from the bottom of the T-104 cyclohexylamine tower enters the T-105 dealcoholization tower. The composition of the residue from the bottom of the T-104 cyclohexylamine tower is as follows:

[0065] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 0.17％ 19.23％ 79.25％ 1.35％

[0066] S5. Set the pressure of the dealcoholization tower T-105 to -0.090MPa, the top temperature to 100.6℃, and the bottom temperature to 148.7℃.

[0067] Cyclohexanol collected from the top of dealcoholization column T-105 is recovered as a feedstock, and the recovered cyclohexanol is subsequently returned to the reaction vessel. The product from the bottom of dealcoholization column T-105 enters dicyclohexylamine column T-106;

[0068] Components of the product obtained from the bottom of the T-105 dealcoholization column:

[0069] Cyclohexanol Dicyclohexylamine impurities 0.01％ 98.33％ 1.66％

[0070] S6. Set the top pressure of the dicyclohexylamine column T-106 to -0.090MPa, the top temperature to 150.5℃, and the bottom temperature to 158.4℃.

[0071] The dicyclohexylamine product is collected from the top of the T-106 dicyclohexylamine tower. The purity of the dicyclohexylamine product is ≥99.85%. The high-boiling material from the bottom of the T-106 dicyclohexylamine tower mainly consists of dicyclohexylamine and unknown impurities (dicyclohexylamine accounts for about 30%).

[0072] In this Example 1, the yield of cyclohexylamine was 99.54%, and the yield of dicyclohexylamine was 99.14%.

[0073] Cyclohexylamine yield = mass of cyclohexylamine product per unit time / mass of cyclohexylamine in crude amine per unit time; Dicyclohexylamine yield = mass of dicyclohexylamine product per unit time / mass of dicyclohexylamine in crude amine per unit time.

[0074] Example 2: The following changes are made compared to Example 1:

[0075] S1, the same as step S1 in Example 1;

[0076] The parameters for S2 and 1# cyclohexylamine dehydration tower T-102 are changed as follows: pressure -0.070MPa, tower top temperature 63.4℃, tower bottom temperature 98.6℃.

[0077] The water content of the azeotrope of cyclohexylamine and water collected from the top of the T-102 dehydration tower (No. 1) was 66.8%.

[0078] Components in the bottom of the T-102 cyclohexylamine dehydration tower (No. 1):

[0079] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 76.69％ 4.25％ 17.91％ 1.15％

[0080] The process parameters set for S3 and the pressurized recovery tower T-103 are changed to the following: pressure 0.30MPa, tower top temperature 126.8℃; tower bottom temperature 131.9℃;

[0081] The water content of the cyclohexylamine and water azeotrope collected from the top of the pressurized recovery tower T-103 was 57.9%.

[0082] Wastewater sample from the bottom of pressurized recovery tower T-103:

[0083] COD concentration (mg / L) Total nitrogen concentration (mg / L) pH value 1654 132 9.47

[0084] The parameters for S4 and T-104 cyclohexylamine tower are changed as follows: pressure controlled at around -0.90MPa, tower top temperature 71.7℃, and tower bottom temperature 121.1℃.

[0085] Cyclohexylamine product is collected from the top of the T-104 cyclohexylamine tower, with a purity ≥99.95%. The bottom material composition of the T-104 cyclohexylamine tower is as follows:

[0086] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 0.14％ 19.29％ 79.13％ 1.44％

[0087] The parameters for S5 and the T-105 dealcoholization tower are changed as follows: pressure controlled at -0.090MPa, tower top temperature 100.4℃, and tower bottom temperature 149.8℃.

[0088] Components of the bottom of the T-105 dealcoholization tower:

[0089] Cyclohexanol Dicyclohexylamine impurities 0.01％ 98.27％ 1.72％

[0090] The parameters for S6 and dicyclohexylamine tower T-106 are changed as follows: -0.090MPa, tower top temperature 150.3℃, tower bottom temperature 157.5℃.

[0091] The dicyclohexylamine product is collected from the top of the T-106 dicyclohexylamine tower. The purity of the dicyclohexylamine product is ≥99.85%. The bottom of the T-106 dicyclohexylamine tower is a high-boiling material, which mainly consists of dicyclohexylamine and unknown impurities (dicyclohexylamine accounts for about 30%).

[0092] In this Example 2, the yield of cyclohexylamine was 99.46%, and the yield of dicyclohexylamine was 99.19%.

[0093] Example 3: The following changes are made compared to Example 1:

[0094] S1 to S2 are the same as steps S1 to S2 in Example 1;

[0095] The process parameters set for S3 and the pressurized recovery tower T-103 are changed to the following: pressure 0.20MPa, tower top temperature 115.5℃; tower bottom temperature 120.9℃;

[0096] The water content of the cyclohexylamine and water azeotrope collected from the top of the T-103 pressurized recovery tower was 58.4%.

[0097] Wastewater sample from the bottom of pressurized recovery tower T-103:

[0098] COD concentration (mg / L) Total nitrogen concentration (mg / L) pH value 1743 182 9.63

[0099] S4 to S6 are equivalent to steps S4 to S6 in Example 1.

[0100] In this Example 3, the yield of cyclohexylamine was 99.18%, and the yield of dicyclohexylamine was 99.43%.

[0101] Example 4: The following changes are made compared to Example 2:

[0102] S1 to S2 are the same as steps S1 to S2 in Example 2;

[0103] The process parameters set for S3 and the pressurized recovery tower T-103 are changed to the following: pressure 0.80MPa, tower top temperature 165.5℃; tower bottom temperature 170.7℃.

[0104] The water content of the cyclohexylamine and water azeotrope collected from the top of the pressurized recovery tower T-103 was 55.1%.

[0105] Wastewater sample from the bottom of pressurized recovery tower T-103:

[0106] COD concentration (mg / L) Total nitrogen concentration (mg / L) pH value 1638 166 9.29

[0107] S4 to S6 are equivalent to steps S4 to S6 in Example 2.

[0108] In this Example 4, the yield of cyclohexylamine was 99.37%, and the yield of dicyclohexylamine was 99.36%.

[0109] Comparative Example 1, according to Chemical Production and Technology, 2010, 17(3), 57-61, is as follows:

[0110] S1, same as step S1 in Example 1. The product obtained from the ammonia tower bottom enters the cyclohexylamine dehydration tower for distillation.

[0111] S2. Add cyclohexane as an azeotropic dehydrating agent, with the amount of cyclohexane being 15% of the mass of crude amine;

[0112] The cyclohexylamine dehydration tower operates at atmospheric pressure, with a top temperature of 76.9℃ and a bottom temperature of 138.9℃.

[0113] The azeotrope of cyclohexane and water (8.4% water content) is collected from the top of the cyclohexylamine dehydration tower. After separation, an aqueous phase and an organic phase are formed. The organic phase is returned to the cyclohexylamine dehydration tower, and the bottom product of the cyclohexylamine dehydration tower enters the dealkylation tower. The bottom composition of the cyclohexylamine dehydration tower is as follows:

[0114] Cyclohexane Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 10.75％ 68.47％ 3.77％ 16.03％ 0.98％

[0115] S3, the dealkylation tower operates at atmospheric pressure, with a top temperature of 86.5℃ and a bottom temperature of 140.2℃. Cyclohexane from the top of the dealkylation tower is returned to the cyclohexylamine dehydration tower, while the bottom product of the dealkylation tower enters the cyclohexylamine tower. Dealkylation tower bottom components:

[0116] Cyclohexane Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 0.00％ 76.72％ 4.22％ 17.96％ 1.1％

[0117] S4. The pressure in the cyclohexylamine tower is controlled at approximately -0.088 MPa, the top temperature is 71.5℃, and the bottom temperature is 121.2℃. Cyclohexylamine product is collected from the top of the tower, with a purity ≥99.95%. The bottom product enters the dealcoholization tower. The composition of the bottom material in the cyclohexylamine tower is as follows:

[0118] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 0.14％ 19.29％ 79.13％ 1.44％

[0119] S5. The pressure of the dealcoholization tower is controlled at -0.089MPa, the top temperature is 100.3℃, and the bottom temperature is 149.6℃.

[0120] Cyclohexanol, collected from the top of the dealcoholization column, is returned to the recycling tank and then to the synthesis system. The bottom product enters the dicyclohexylamine column. Components from the bottom of the dealcoholization column:

[0121] Cyclohexanol Dicyclohexylamine impurities 0.01％ 98.21％ 1.78％

[0122] The dehydration efficiency of cyclohexane in Example 1 of this invention is 68.9% - 55.7% = 13.2%, while the dehydration efficiency of cyclohexane in Comparative Example 1 is 8.4%. Furthermore, the addition of cyclohexane azeotropic distillation in Comparative Example 1 not only increased the cost but also introduced cyclohexane impurities.

[0123] Comparative Example 2: The "differential pressure distillation" of the present invention is omitted, and the apparatus used is as follows: Figure 2 As shown:

[0124] 1) Same as step S1 in Example 1. The product obtained from the bottom of ammonia tower T-101 enters the No. 1 cyclohexylamine dehydration tower T-102 for distillation;

[0125] 2) The pressure of the No. 1 cyclohexylamine dehydration tower T-102 is -0.090MPa, the temperature at the top of the tower is 45.4℃, and the temperature at the bottom of the tower is 96.4℃.

[0126] The top of cyclohexylamine dehydration tower T-102 yields an azeotrope of cyclohexylamine and water (water content 68-69%). The bottom product of cyclohexylamine dehydration tower T-102 enters cyclohexylamine tower T-104. The bottom composition of cyclohexylamine dehydration tower T-102 is as follows:

[0127] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 76.75％ 4.26％ 17.96％ 1.03％

[0128] 3) The pressure of the cyclohexylamine tower T-104 is controlled at around -0.090MPa, the top temperature is 71.5℃, and the bottom temperature is 120.8℃.

[0129] Cyclohexylamine product is collected from the top of the T-104 cyclohexylamine tower. The purity of the cyclohexylamine product is ≥99.95%. The bottom product enters the T-105 dealcoholization tower. The composition of the bottom product of the T-104 cyclohexylamine tower is as follows:

[0130] Cyclohexylamine Cyclohexanol Dicyclohexylamine impurities 0.12％ 19.31％ 79.15％ 1.42％

[0131] 4) The pressure of the T-105 dealcoholization tower is controlled at -0.090MPa, the top temperature is 100.5℃, and the bottom temperature is 149.9℃.

[0132] Cyclohexanol collected from the top of dealcoholization column T-105 is returned to the recycling tank for recovery and then back to the synthesis system. The bottom product enters dicyclohexylamine column T-106. Components from the bottom of dealcoholization column T-105:

[0133] Cyclohexanol Dicyclohexylamine impurities 0.01％ 98.24％ 1.75％

[0134] 5) The top pressure of the dicyclohexylamine tower T-106 is -0.090MPa, the top temperature is 150.3℃, and the bottom temperature is 157.5℃.

[0135] The dicyclohexylamine product is collected from the top of the T-106 dicyclohexylamine tower. The purity of the dicyclohexylamine product is ≥99.7%. The bottom of the T-10 dicyclohexylamine tower is a high-boiling material, which mainly consists of dicyclohexylamine and unknown impurities (dicyclohexylamine accounts for about 30%).

[0136] In this Comparative Example 2, the yield of cyclohexylamine was only 82%, which is far lower than the yield obtained in Example 1 of this invention.

[0137] Unrecovered cyclohexylamine products exist as a mixture of cyclohexylamine and water (water content approximately 68–69%).

[0138] Comparative Example 3, compared to Comparative Example 2, is modified as follows:

[0139] The settings for the No. 1 cyclohexylamine dehydration tower (T-102) were changed from "pressure -0.090MPa, top temperature 45.4℃, bottom temperature 96.4℃" to "pressure 0.5MPa, top temperature controlled at 145.2℃, bottom temperature at 150.8℃".

[0140] The result showed that the yield of cyclohexylamine was only 69%, which was far lower than the yield obtained in Example 1 of this invention.

[0141] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for purifying crude amine obtained by cyclohexanol amination by distillation to obtain cyclohexylamine and dicyclohexylamine, wherein the cyclohexanol amination is carried out in a reaction vessel to obtain crude amine containing cyclohexylamine and dicyclohexylamine, characterized in that... Includes the following steps: S1. Crude amine is condensed and then enters the ammonia tower (T101). The pressure of the ammonia tower (T101) is set to 1.28-1.32 MPa, the top temperature of the tower is 40-42℃, and the bottom temperature of the tower is 170-175℃. Ammonia in the crude amine is discharged from the top of the ammonia tower (T101) as a gas and then recovered as a reaction feedstock; the product obtained from the bottom of the ammonia tower (T101) enters the No. 1 cyclohexylamine dehydration tower (T-102) for distillation. The recovered ammonia is returned to the synthesis system within the reaction vessel; S2. Set the pressure of the No. 1 cyclohexylamine dehydration tower (T-102) to -0.060~-0.095Mpa, the top temperature of the tower to 40~75℃, and the bottom temperature of the tower to 90~110℃; The azeotrope of cyclohexylamine and water, I, is collected from the top of the No. 1 cyclohexylamine dehydration tower (T-102). The azeotrope of cyclohexylamine and water, I, enters the pressurized recovery tower (T-103) for pressurized distillation. The product obtained from the bottom of the No. 1 cyclohexylamine dehydration tower enters the cyclohexylamine tower (T-104) for distillation and purification of the cyclohexylamine product. S3. Set the pressure of the pressurized recovery tower (T-103) to 0.2-0.8 MPa, the top temperature to 115-175℃, and the bottom temperature to 120-180℃. The azeotrope of cyclohexylamine and water II is collected from the top of the pressurized recovery tower (T-103) and returned to the No. 1 cyclohexylamine dehydration tower (T-102) for further distillation. S4. Set the pressure of the cyclohexylamine tower (T-104) to -0.085 to -0.095 MPa, the top temperature to 70 to 75°C, and the bottom temperature to 120 to 135°C. Cyclohexylamine is collected as a product from the top of the cyclohexylamine tower (T-104), and the product obtained from the bottom of the cyclohexylamine tower (T-104) enters the dealcoholization tower (T-105) for dealcoholization treatment. S5. Set the pressure of the dealcoholization tower (T-105) to -0.085 to -0.095 MPa, the top temperature to 100 to 105℃, and the bottom temperature to 145 to 150℃. The cyclohexanol collected from the top of the dealcoholization tower (T-105) is used as a raw material for recovery, and the product obtained from the bottom of the dealcoholization tower (T-105) enters the dicyclohexylamine tower (T-106) for distillation recovery and purification of dicyclohexylamine products. The recovered cyclohexanol was returned to the synthesis system within the reaction vessel. S6. Set the top pressure of the dicyclohexylamine tower (T-106) to -0.085 to -0.095 MPa, the top temperature to 150 to 152°C, and the bottom temperature to 155 to 162°C. Dicyclohexylamine is collected from the top of the dicyclohexylamine tower (T-106) as the product.

2. The method for obtaining cyclohexylamine and dicyclohexylamine by distillation purification of crude amine obtained by the cyclohexanol amination method according to claim 1, characterized in that: Wastewater generated in the bottom of the pressurized recovery tower (T-103) is discharged into a wastewater pond; The product obtained from the bottom of the dicyclohexylamine tower (T-106) is a high-boiling-point material, which is disposed of as waste.

3. The method for obtaining cyclohexylamine and dicyclohexylamine by distillation purification of crude amine obtained by the cyclohexanol amination method according to claim 1 or 2, characterized in that... As a preferred option: In S1, the ammonia tower (T101) is set with the following parameters: pressure 1.28~1.32Mpa, tower top temperature 40~41℃, tower bottom temperature 172~174℃; In S2, the parameters of the No. 1 cyclohexylamine dehydration tower (T-102) are set as follows: pressure -0.088~-0.090MPa, tower top temperature 44~46℃, tower bottom temperature 95~97℃; In S3, the process parameters set for the pressurized recovery tower (T-103) are: pressure 0.48~0.52MPa, tower top temperature controlled at 144~146℃, and tower bottom temperature at 148~152℃. In S4, the pressure of the cyclohexylamine tower (T-104) is controlled at -0.088 to -0.090 MPa, the top temperature is 71 to 72℃, and the bottom temperature is 120 to 122℃. In S5, the pressure of the dealcoholization tower (T-105) is controlled at -0.088 to -0.092 MPa, the top temperature is 100 to 101℃, and the bottom temperature is 148 to 150℃. In S6, the top pressure of the dicyclohexylamine tower (T-106) is -0.088 to -0.092 MPa, the top temperature is 150 to 151°C, and the bottom temperature is 157 to 159°C.

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