Method for joint production of cyclohexylamine and dicyclohexylamine

Abstract

The invention discloses a method for joint production of cyclohexylamine and dicyclohexylamine, which comprises the following steps: 1) feeding aniline tail gas of a nitrobenzene catalytic hydrogenation production device into a gas-liquid separator for gas-liquid separation to obtain aniline tail hydrogen and aniline condensate; 2) mixing aniline tail hydrogen and new hydrogen as a raw material A, and mixing defective aniline and fresh aniline in proportion as a raw material B; (3) feeding the vaporized raw material B and the vaporized raw material A into a fixed bed reactor according to a certain hydrogen-oil ratio, and carrying out hydrogenation reaction; a hydrogenation reaction product is subjected to heat exchange condensation and then enters a gas-liquid separator for gas-liquid separation, a gas phase serves as recycle hydrogen to be mixed with the raw material A, and a liquid phase is fed into a distillation device; and 4) carrying out primary distillation and rectification purification in sequence to obtain cyclohexylamine and dicyclohexylamine. According to the method, aniline tail gas resources and defective aniline are fully utilized, the three-waste treatment cost is reduced, product benefits can be improved, pollution to the environment can be reduced, and economic benefits and social benefits are remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of cyclohexylamine preparation, and particularly relates to a method for co-producing cyclohexylamine and dicyclohexylamine. Background Art

[0002] The industrial production of aniline began in 1857. Initially, the nitrobenzene iron powder reduction method was adopted. Due to its disadvantages such as large equipment, serious corrosion, large consumption of iron powder, and serious "three wastes" pollution, it was gradually replaced by the advanced nitrobenzene catalytic hydrogenation method after the 1950s. In 1962, the phenol amination method was successfully developed and industrialized in 1970. At present, the production of aniline in the world is mainly based on the nitrobenzene catalytic hydrogenation method, and its production capacity accounts for about 85% of the total aniline production capacity. The tail gas of the nitrobenzene catalytic hydrogenation production device contains a large amount of hydrogen and a small amount of organic substances such as aniline vapor. Common organic waste gas treatment methods include activated carbon adsorption method, condensation method, combustion method, etc. The activated carbon adsorption method has high operating costs; the condensation method is suitable for high-concentration organic waste gas, and the treatment efficiency of low-concentration organic waste gas is relatively low; the combustion method for treating nitrogen-containing organic waste gas produces nitrogen oxides, causing secondary pollution. In addition, the aniline with excessive light components in the aniline production device and the aniline in the top product of the light component removal tower have low aniline content and also contain components such as cyclohexanol, cyclohexane, phenol, and cyclohexylamine, which need to be further separated and purified or sold at a low price, resulting in low economic benefits.

[0003] As important organic chemical raw materials and intermediates of fine chemical products, cyclohexylamine and dicyclohexylamine are widely used in industries such as rubber auxiliaries, food additives, anti-corrosion, papermaking, plastic processing, and textile industry. At present, the industrial methods for preparing cyclohexylamine are aniline catalytic hydrogenation method and cyclohexanol catalytic ammonolysis method. Due to the low raw material cost and simple process route of the aniline catalytic hydrogenation method, it can realize the co-production of cyclohexylamine and dicyclohexylamine, and can freely switch the output ratio of the two products by adjusting the catalyst formula and synthesis process conditions, which has received extensive attention from domestic and foreign research institutions and manufacturers.

[0004] US 5728883A discloses a non-supported cobalt catalyst and a method for synthesizing cyclohexylamine. This catalyst contains Co, Mn, alkaline earth metals, and other transition metal elements. The reaction is carried out under a high pressure of 30 MPa, and the aniline conversion rate can reach more than 95%. The disadvantage is that this catalyst is more sensitive to the reaction temperature and needs to react under very high pressure, and the reaction conditions are harsh.

[0005] CN 102633649B discloses a γ-Al 2 O 3Supported cobalt-ruthenium or nickel-ruthenium catalysts. When using this catalyst for the hydrogenation reaction of aniline, in order to inhibit the production of by-product dicyclohexylamine, ammonia gas needs to be added to the recycled hydrogen. The disadvantages of this method are that the yield of cyclohexylamine is not high. In addition, the introduction of ammonia gas will cause equipment corrosion, posing safety hazards, and an ammonia recovery and desorption process needs to be added during the post-treatment process.

[0006] Monsanto Company in the United States prepared an aniline hydrogenation catalyst by loading the active component ruthenium onto carbon, alumina, diatomaceous earth or some other inert carriers. To inhibit the coupling reaction, ammonia gas was also introduced during the reaction to improve the selectivity of cyclohexylamine. This reaction was carried out in a high-pressure reactor, and the highest yield of cyclohexylamine could reach 95.6%, but this process also had problems such as equipment corrosion and harsh reaction conditions.

[0007] Patent CN 109651167A discloses a hydrogenation catalyst for the production of cyclohexylamine, including a carrier and an active component. The carrier is phosphorus-modified Al 2 O 3 , and the active component includes Co element and a promoter. The yields and selectivities of cyclohexylamine are about 82% and 90% respectively.

[0008] Patent CN 113289662 B provides a catalyst, preparation method and application for the hydrogenation of aniline to prepare cyclohexylamine. The active component of this catalyst is Co and at least one of the promoters Mg, Ca, Zn, and the carrier is modified CeO 2 , which has good reaction performance under high space velocity and high temperature conditions, but its preparation process is relatively complex, the hydrogenation reaction temperature is relatively high, and the production cost lacks competitiveness.

[0009] In summary, the current research directions for the catalytic hydrogenation of aniline to synthesize cyclohexylamine mainly focus on the development and modification of catalysts, but the results are not obvious, and it is difficult to break through problems such as low yield or selectivity of cyclohexylamine and harsh reaction conditions. Summary of the Invention

[0010] In order to solve the technical problems of high tail gas treatment cost and easy secondary environmental pollution generated by the existing nitrobenzene catalytic hydrogenation production of aniline device, and the low economic benefits of the produced defective aniline (including aniline with excessive light components in the aniline production device, the top product of the light component removal tower, and aniline tail gas condensate), the present invention provides a method for the combined production of cyclohexylamine and dicyclohexylamine.

[0011] The technical solution adopted by the present invention is as follows:

[0012] 1. A method for the combined production of cyclohexylamine and dicyclohexylamine, comprising the following steps:

[0013] 1) After removing organic substances and catalyst particles from the aniline tail gas of the nitrobenzene catalytic hydrogenation production unit through a membrane processor, it is sent to a gas-liquid separator A for gas-liquid separation to obtain aniline tail hydrogen and aniline condensate;

[0014] 2) Mix the aniline tail hydrogen and fresh hydrogen as raw material A, mix the aniline condensate with the aniline with excessive light components in the aniline production unit and the overhead discharge of the light removal tower as defective aniline, and mix the defective aniline and fresh aniline in a certain proportion as raw material B;

[0015] 3) Feed the vaporized raw material B and raw material A into a fixed-bed reactor according to a certain hydrogen-oil ratio, and carry out a hydrogenation reaction at a certain reaction temperature and reaction pressure; the hydrogenation reaction product is cooled by heat exchange and then enters a gas-liquid separator B for gas-liquid separation. The separated gas phase is used as recycle hydrogen and mixed with raw material A, and the separated liquid phase is sent to a distillation unit;

[0016] 4) After being purified by preliminary distillation and rectification in sequence, cyclohexylamine and dicyclohexylamine are obtained.

[0017] Preferably, in step 2), the aniline content in the defective aniline is 80-96%.

[0018] Preferably, in step 1), the method for removing impurities in the aniline tail gas is to separate the liquid organic substances and trace catalyst particles in the aniline tail gas by using a membrane processor. The separation membrane used in the membrane processor is a new type of silicon carbide ceramic composite membrane, and the membrane pore size is 10-100 nm.

[0019] Preferably, the molar ratio of the defective aniline to the fresh aniline is 1:(20-5). More preferably, the molar ratio of the defective aniline to the fresh aniline is 1:(15-8).

[0020] Preferably, in step 3), the hydrogen-oil ratio is (5-22):1, the hydrogenation reaction temperature is 120-200 °C, the pressure is 0-0.6 MPa, and the feed space velocity of raw material B is 0.05-1 h -1 .

[0021] Preferably, in step 3), the fixed-bed reactor is filled with a new type of cobalt-based catalyst. The new type of cobalt-based catalyst uses modified silica gel as a carrier, loads active components Co and promoters. The promoters are composed of two metal elements A and B. The metal element A is La, and the metal element B is at least one of Zn, Cu, Mg, and Ni. The loading amount of Co is 1-40 wt%, the loading amount of the promoter is 0.6-5 wt%, and the mass percentage content of La in the promoter is 4-50%.

[0022] Preferably, the preparation method of the carrier includes the following steps:

[0023] (8.1) Prepare a 1.5 - 5% solution by mixing tetrapropylammonium hydroxide and ammonium dihydrogen phosphate in a ratio of 1:(2 - 4).

[0024] (8.3) Add silica gel to the above - mentioned solution and perform heat treatment at 120 - 160 °C and 0.11 - 0.14 MPa for 4 - 8 h; the mass ratio of silica gel to the solution is (0.5 - 1):1.

[0025] (8.3) Vacuum - dry the heat - treated solution to obtain the carrier.

[0026] Preferably, in step 4), the refining device includes a prefractionating column and a rectifying column. The number of theoretical plates of the rectifying column is 10 - 25, and the reflux ratio of rectification is 2 - 12:1.

[0027] Advantages of the present invention:

[0028] (1) Co - produce cyclohexylamine and dicyclohexylamine through the co - production optimization of aniline and cyclohexylamine plants, make full use of aniline tail gas resources and unqualified aniline products, reduce the cost of "three wastes" treatment, not only improve product efficiency but also reduce environmental pollution. Based on the comprehensive calculation of the efficient utilization of aniline plant resources and the cost of "three wastes" treatment, etc., after 3 months of operation through the combined optimization of aniline and cyclohexylamine production, the comprehensive cost of the plant is reduced by 15%, and the economic benefit of the product is increased by about 18%, showing significant economic and social benefits.

[0029] (2) In the aniline catalytic hydrogenation reaction, using modified silica gel as the carrier, loading the active component Co, and adding elements such as Zn, Cu, Mg, Ni, and La as catalytic aids, the surface of the carrier has abundant basic sites, which can improve the selectivity and service life of the catalyst. The aniline conversion rate reaches 100%, and the product selectivity is greater than 98%.

[0030] (3) The process conditions are mild, impurities such as low - boilers in the raw materials do not participate in the reaction, the post - treatment process is simple, and the industrial application effect is good. Brief Description of the Drawings

[0031] Figure 1 It is the process flow chart of a method for co - producing cyclohexylamine and dicyclohexylamine of the present invention. Detailed Embodiments

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the attached Figure 1 drawings and Examples 1 - 10.

[0033] Example 1

[0034] Prepare catalyst carrier A:

[0035] (1) Prepare a 1.5% solution by mixing tetrapropylammonium hydroxide and ammonium dihydrogen phosphate in a ratio of 1:2;

[0036] (2) Add silica gel to the above solution in a mass ratio of 0.5:1 and perform heat treatment at 120 °C and 0.11 MPa for 8 h

[0037] (3) Vacuum dry the heat-treated solution at 80 °C for 4 h to obtain modified silica gel.

[0038] Example 2

[0039] Prepare catalyst support B:

[0040] (1) Prepare a 5% solution by mixing tetrapropylammonium hydroxide and ammonium dihydrogen phosphate in a ratio of 1:4;

[0041] (2) Add silica gel to the above solution in a mass ratio of 1:1 and perform heat treatment at 160 °C and 0.14 MPa for 4 h;

[0042] (3) Vacuum dry the heat-treated solution at 85 °C for 3.5 h to obtain modified silica gel.

[0043] Example 3

[0044] Prepare catalyst support C:

[0045] (1) Prepare a 2.5% solution by mixing tetrapropylammonium hydroxide and ammonium dihydrogen phosphate in a ratio of 1:2.5;

[0046] (2) Add silica gel to the above solution in a mass ratio of 0.8:1 and perform heat treatment at 150 °C and 0.10 MPa for 6 h;

[0047] (3) Vacuum dry the heat-treated solution at 70 °C for 5 h to obtain modified silica gel.

[0048] Examples 4 - 10

[0049] Refer to Figure 1 , and produce cyclohexylamine and dicyclohexylamine jointly according to the following steps:

[0050] 1) After removing organic substances and catalyst particles from the aniline production tail gas of the nitrobenzene catalytic hydrogenation production device through a membrane processor, send it to a gas-liquid separator for gas-liquid separation to obtain aniline tail hydrogen and aniline condensate;

[0051] 2) Mix aniline tail hydrogen with fresh hydrogen and store it in a hydrogen buffer tank as raw material A. Mix aniline condensate with aniline with excessive light components in the aniline production device and the outlet material from the dehydrogenation tower top as defective aniline. Mix defective aniline with fresh aniline in proportion and store it in an aniline buffer tank as raw material B;

[0052] 3) After being preheated by a hydrogen preheater, raw material A is mixed with raw material B vaporized by an aniline preheater at a certain hydrogen-oil ratio and then enters a fixed-bed reactor, where a hydrogenation reaction is carried out under certain reaction temperature and reaction pressure; the hydrogenation reaction product enters a condenser, is heat-exchanged and condensed, and then enters a gas-liquid separator B. The gas phase separated in the gas-liquid separator B is returned to the hydrogen preheater as recycle hydrogen, and the separated liquid phase is stored in a crude product tank;

[0053] 4) The hydrogenation reaction product in the crude product tank enters a preliminary distillation column to separate components such as cyclohexanol, cyclohexane, phenol, and cyclohexylamine. The hydrogenation reaction product from which the light components are separated enters a rectification column for refining to obtain cyclohexylamine and dicyclohexylamine.

[0054] The fixed-bed reactor is filled with a novel cobalt-based catalyst. The novel cobalt-based catalyst uses the modified silica gel prepared in Examples 1-3 as a carrier, and loads active component Co and promoters. The promoters are composed of two metal elements A and B. The metal element A is La, and the metal element B is at least one of Zn, Cu, Mg, and Ni.

[0055] Example 4

[0056] The membrane pore size of the membrane processor is 10 nm; the novel cobalt-based catalyst uses the modified silica gel prepared in Example 1 as a carrier, and the loading amounts of the active component and the promoter are: 1 wt% Co, 4.5 wt% Zn, and 0.2 wt% La.

[0057] The aniline content in the defective aniline is 95.5%, and the molar ratio of the defective aniline to the fresh aniline is 1:15; the process of the fixed-bed hydrogenation reaction: the reaction temperature is 120 °C, the pressure is 0.1 MPa, and the aniline feed space velocity is 0.05 h -1 , and the hydrogen-oil ratio is 5:1.

[0058] Preliminary distillation process: Atmospheric distillation is carried out at a temperature of 80 °C. Rectification process: The vacuum degree is 16 mmHg, the number of theoretical plates of the rectification column is 10, and the reflux ratio is 2:1.

[0059] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.8%, and the purity of dicyclohexylamine is 99.6%; it can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 98.7%, and the total yield of cyclohexylamine and dicyclohexylamine is about 96% (calculated based on aniline).

[0060] Example 5

[0061] The membrane pore size of the membrane processor is 30 nm; the novel cobalt-based catalyst uses the pore-expanded silica gel prepared in Example 2 as a carrier, and the loading amounts of the active component and the promoter are: 40 wt% Co, 0.5 wt% Zn, and 0.5 wt% La.

[0062] The aniline content in the defective aniline is 92.3%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:20; Process of the fixed-bed hydrogenation reaction: The reaction temperature is 165 °C, the pressure is 0.2 MPa, and the aniline feed space velocity is 0.2 h -1 , and the hydrogen-oil ratio is 10:1.

[0063] Initial distillation process: Atmospheric distillation is carried out at a temperature of 100 °C. Rectification process: The vacuum degree is 16 mmHg, the number of theoretical plates of the rectification column is 15, and the reflux ratio is 8:1.

[0064] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.8%, and the purity of dicyclohexylamine is 99.7%; It can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 98.5%, and the total yield of cyclohexylamine and dicyclohexylamine is about 97% (calculated based on aniline).

[0065] Example 6

[0066] The membrane pore size of the membrane processor is 10 nm; The novel cobalt-based catalyst uses the enlarged-pore silica gel prepared in Example 3 as the carrier, and the loading amounts of the active component and the promoter are: 15 wt% Co, 0.6 wt% Cu, 0.6 wt% Mg, and 0.2 wt% La.

[0067] The aniline content in the defective aniline is 94.1%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:5; Process of the fixed-bed hydrogenation reaction: The reaction temperature is 200 °C, the pressure is 0.6 MPa, and the aniline feed space velocity is 1 h -1 , and the hydrogen-oil ratio is 22:1.

[0068] Initial distillation process: Atmospheric distillation is carried out at a temperature of 100 °C. Rectification process: The vacuum degree is 16 mmHg, the number of theoretical plates of the rectification column is 25, and the reflux ratio is 12:1.

[0069] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.9%, and the purity of dicyclohexylamine is 99.8%; It can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 98.1%, and the total yield of cyclohexylamine and dicyclohexylamine is about 97.5% (calculated based on aniline).

[0070] Example 7

[0071] The membrane pore size of the membrane processor is 100 nm; The novel cobalt-based catalyst uses the enlarged-pore silica gel prepared in Example 3 as the carrier, and the loading amounts of the active component and the promoter are: 30 wt% Co, 1 wt% Cu, 2 wt% Ni, and 0.2 wt% La.

[0072] The aniline content in the defective aniline is 94.1%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:8; the process of the fixed-bed hydrogenation reaction: the reaction temperature is 170 °C, the pressure is 0.3 MPa, and the aniline feed space velocity is 0.5 h -1 , and the hydrogen-oil ratio is 18:1.

[0073] The preliminary distillation process: atmospheric distillation is carried out at a temperature of 120 °C. The rectification process: the vacuum degree is 16 mmHg, the number of theoretical plates of the rectification column is 10, and the reflux ratio is 8:1.

[0074] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.8%, and the purity of dicyclohexylamine is 99.7%; it can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 98.8%, and the total yield of cyclohexylamine and dicyclohexylamine is about 96.5% (calculated based on aniline).

[0075] Example 8

[0076] The membrane pore size of the membrane processor is 10 nm; the novel cobalt-based catalyst uses the enlarged-pore silica gel prepared in Example 3 as the carrier, and the loading amounts of the active component and the promoter are: 15 wt% Co, 1 wt% Cu, 1 wt% Zn, 1.5 wt% Ni, and 0.5 wt% La.

[0077] The aniline content in the defective aniline is 91.2%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:10; the process of the fixed-bed hydrogenation reaction: the reaction temperature is 180 °C, the pressure is 0.3 MPa, and the aniline feed space velocity is 0.2 h -1 , and the hydrogen-oil ratio is 16:1.

[0078] The preliminary distillation process: atmospheric distillation is carried out at a temperature of 95 °C. The rectification process: the vacuum degree is 16 mmHg, the number of theoretical plates of the rectification column is 12, and the reflux ratio is 7:1.

[0079] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.9%, and the purity of dicyclohexylamine is 99.8%; it can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 99.3%, and the total yield of cyclohexylamine and dicyclohexylamine is about 96.8% (calculated based on aniline).

[0080] Example 9

[0081] The membrane pore size of the membrane processor is 50 nm; the novel cobalt-based catalyst uses the enlarged-pore silica gel prepared in Example 1 as the carrier, and the loading amounts of the active component and the promoter are: 21 wt% Co, 2 wt% Cu, 2 wt% Zn, 0.5 wt% Ni, and 0.5 wt% La.

[0082] The aniline content in the defective aniline is 93.7%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:10; the process of the fixed-bed hydrogenation reaction: the reaction temperature is 180 °C, the pressure is 0.3 MPa, and the aniline feed space velocity is 0.2 h -1 , and the hydrogen-oil ratio is 16:1.

[0083] The preliminary distillation process: atmospheric distillation at a temperature of 96 °C. The rectification process: the vacuum degree is 16 mmHg, the number of theoretical plates in the rectification column is 12, and the reflux ratio is 8:1.

[0084] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.9%, and the purity of dicyclohexylamine is 99.8%; it can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 99.6%, and the total yield of cyclohexylamine and dicyclohexylamine is about 98% (calculated based on aniline).

[0085] Example 10

[0086] The membrane pore size of the membrane processor is 40 nm; the novel cobalt-based catalyst uses the expanded-pore silica gel prepared in Example 2 as the carrier, and the loading amounts of the active component and the promoter are: 18 wt% Co, 1 wt% Cu, 1.5 wt% Ni, and 0.2 wt% La.

[0087] The aniline content in the defective aniline is 82.1%, and the molar ratio of the defective aniline to the fresh aniline in the mixture is 1:8; the process of the fixed-bed hydrogenation reaction: the reaction temperature is 170 °C, the pressure is 0.5 MPa, and the aniline feed space velocity is 0.4 h -1 , and the hydrogen-oil ratio is 12:1.

[0088] The preliminary distillation process: atmospheric distillation at a temperature of 96 °C. The rectification process: the vacuum degree is 16 mmHg, the number of theoretical plates in the rectification column is 10, and the reflux ratio is 5:1.

[0089] The cyclohexylamine and dicyclohexylamine fractions are collected separately and subjected to gas chromatography analysis (GC). The purity of cyclohexylamine is 99.8%, and the purity of dicyclohexylamine is 99.8%; it can be calculated that the total selectivity of cyclohexylamine and dicyclohexylamine is 99.4%, and the total yield of cyclohexylamine and dicyclohexylamine is about 97.7% (calculated based on aniline).

[0090] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for co-producing cyclohexylamine and dicyclohexylamine, characterized in that, it comprises the following steps: 1) After removing organic substances and catalyst particles from the aniline tail gas of the nitrobenzene catalytic hydrogenation production device through a membrane processor, it is sent to a gas-liquid separator A for gas-liquid separation to obtain aniline tail hydrogen and aniline condensate; 2) Mix aniline tail hydrogen and fresh hydrogen as raw material A, mix aniline condensate with aniline with excessive light components in the aniline production device and the top discharge of the de-lighting tower as defective aniline, and mix defective aniline and fresh aniline in a certain proportion as raw material B; 3) Feed the vaporized raw material B and raw material A into a fixed-bed reactor according to a certain hydrogen-oil ratio, and carry out a hydrogenation reaction under a certain reaction temperature and reaction pressure; the hydrogenation reaction product is cooled by heat exchange and then enters a gas-liquid separator B for gas-liquid separation. The separated gas phase is used as recycle hydrogen and mixed with raw material A, and the separated liquid phase is sent to a distillation device; 4) After primary distillation and rectification purification in sequence, cyclohexylamine and dicyclohexylamine are obtained.

2. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, in step 2), the aniline content in the defective aniline is 80-96%.

3. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, in step 1), the method for removing impurities in the aniline tail gas is to use a membrane processor to separate the liquid organic substances and trace catalyst particles in the aniline tail gas. The separation membrane used in the membrane processor is a new type of silicon carbide ceramic composite membrane, and the membrane pore size is 10-100 nm.

4. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, the molar ratio of the mixture of defective aniline and fresh aniline is 1:(20-5).

5. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 4, characterized in that, the molar ratio of the mixture of defective aniline and fresh aniline is 1:(15-8).

6. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, In step 3), the hydrogen-oil ratio is (5 - 22):1, the hydrogenation reaction temperature is 120 - 200 °C, the pressure is 0 - 0.6 MPa, and the feed space velocity of raw material B is 0.05 - 1 h -1 .

7. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, in step 3), a new type of cobalt-based catalyst is filled in the fixed-bed reactor. The new type of cobalt-based catalyst uses modified silica gel as a carrier, loads active components Co and promoters. The promoter is composed of two metal elements A and B. The metal element A is La, and the metal element B is at least one of Zn, Cu, Mg and Ni. The loading amount of Co is 1-40 wt%, the loading amount of the promoter is 0.6-5 wt%, and the mass percentage content of La in the promoter is 4-50%.

8. The method for co-producing cyclohexylamine and dicyclohexylamine according to claim 7, characterized in that, the preparation method of the carrier comprises the following steps: (8.1) Prepare a 1.5-5% solution by mixing tetrapropylammonium hydroxide and ammonium dihydrogen phosphate at a ratio of 1:(2-4); (8.2) Add silica gel to the above solution and carry out heat treatment at 120-160 °C and 0.11-0.14 MPa for 4-8 h; the mass ratio of silica gel to the solution is (0.5-1):1; (8.3) Vacuum dry the heat-treated solution to obtain the carrier.

9. A method for co-producing cyclohexylamine and dicyclohexylamine according to claim 1, characterized in that, in step 4), the refining device includes a preliminary distillation column and a rectification column, the number of theoretical plates of the rectification column is 10 to 25, and the reflux ratio of rectification is (2 to 12):1.

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