Method for preparing hexamethylenediamine

Abstract

The present invention discloses a method for preparing hexamethylenediamine, the method comprising the following steps: (1) subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, optionally in the presence of a first solvent, to obtain an ammonia reaction product; (2) separating the ammonia reaction product from step (1) to obtain a hexamethylenediamine product and a heavy component; and (3) performing ammonia decomposition on the heavy component under ammonia decomposition reaction conditions to obtain an ammonia decomposition reaction product, and returning the ammonia decomposition reaction product to step (2). The present invention can not only improve the yield of hexamethylenediamine but also extend the service life of the catalyst.

Description

Detailed description of the invention

[0001] [Technical Field] The present invention relates to the technical field for the production of hexamethylenediamine, and more particularly to a method for preparing hexamethylenediamine using hexanediol as a raw material.

[0002] 〔background〕 Hexamethylenediamine is an important chemical raw material. It is an essential raw material monomer for the production of polyamide nylon 66. Hexamethylenediamine is also used in the production of other types of polyamides, such as nylon 610 and nylon 612. Hexamethylenediamine is a key intermediate raw material in the engineering plastics industry. As the market size for nylon 66 continues to expand, the demand for its raw material, hexamethylenediamine, is also continuously growing.

[0003] Industrial methods for producing hexamethylenediamine mainly include the adiponitrile process, the caprolactam process, the adipic acid process, and the hexanediol ammonia process.

[0004] The adiponitrile process is the most commonly used manufacturing method in industrial production. This method can be divided into two approaches: the high-pressure method and the low-pressure method. The high-pressure method uses iron-based catalysts and cobalt-copper-based catalysts as the main catalysts, and conversion rates can reach over 95%, but the high pressure and extremely high equipment requirements are significant. The low-pressure method uses Raney nickel as the main catalyst, but there are issues regarding the safety and stability of the Raney nickel catalyst, as well as the supply of adiponitrile raw materials.

[0005] In the caprolactam process, caprolactam is ammoniacalized with ammonia under the catalytic action of a phosphate to produce 6-aminocapronitrile, which is then hydrogenated to produce hexamethylenediamine. The key step in this method is the ammoniacalization of caprolactam. This method is only applicable to small-scale production and has been gradually abandoned due to its high production costs.

[0006] The adipic acid process involves ammoniating adipic acid with ammonia, then dehydrating it to produce adiponitrile, and finally hydrogenating the adiponitrile to obtain hexamethylenediamine. This method has high manufacturing costs and a long process, which limits the scope of process technology development.

[0007] The hexanediol process is a method for preparing hexamethylenediamine by subjecting hexanediol and ammonia to an ammoniaization reaction. Hexanediol is a colorless, transparent liquid with low toxicity and minimal harm to the environment and human health. The preparation of hexamethylenediamine using hexanediol as a starting material is a green and environmentally friendly route. However, in the prior art, common problems in processes for producing hexamethylenediamine by ammoniaization of hexanediol are the low conversion rate of hexanediol, the selectivity of hexamethylenediamine, and the low yield of hexamethylenediamine. As calculated according to the disclosed data, the yield of hexamethylenediamine is typically less than 50%, leaving room for improvement in economic efficiency.

[0008] CN114433122A discloses a catalyst for preparing 1,6-hexamethylenediamine by ammonia-converting 1,6-hexanediol in the presence of hydrogen. In a fixed-bed reactor, the molar ratio of hydrogen:ammonia:1,6-hexanediol is 3:8:1, and the volume space velocity of 1,6-hexanediol is 0.6h. -1 The reaction temperature was 205°C, the reaction pressure was 13 MPa, the conversion rate of hexanediol was approximately 80% to 92%, and the selectivity of hexamethylenediamine was approximately 42% to 52%. According to the disclosed data, the yield of hexamethylenediamine is calculated to be approximately 34% to 48%.

[0009] JP2022112396A discloses a method for producing hexamethylenediamine from 1,6-hexanediol, comprising the amination reaction of 1,6-hexanediol under mild conditions in the presence of a solid catalyst, wherein the catalyst comprises an active component containing a metal element selected from elements of Group 8, Group 9, the first Group 0, and the first Group 1 of the periodic table, and a support containing rare earth elements and one or more metal elements selected from elements of Group 4 and Group 5. According to the examples, the yield of hexamethylenediamine is less than 40%.

[0010] Furthermore, the prior art process of preparing hexamethylenediamine by ammoniation of hexanediol is prone to polymerization, producing organic amines with a high carbon content, mainly dihexamethylenetriamine and other organic amines with more than 12 carbon atoms (collectively referred to as C12 and C12+ amines in this invention). If this portion of the product is not recycled, it may simply be discharged as waste liquid, resulting in a low overall yield of the target product, hexamethylenediamine. Therefore, there is still a need for a method of preparing hexamethylenediamine that can produce hexamethylenediamine from hexanediol in high yield, thereby improving process economics.

[0011] 〔overview〕 The object of the present invention is to provide a method for preparing hexamethylenediamine in high yield so as to overcome the problems present in the prior art.

[0012] To achieve the above objective, the present invention provides a method for preparing hexamethylenediamine, which involves the following steps: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, optionally in the presence of a first solvent, to obtain an ammonia reaction product; (2) A step of separating the ammonia reaction product from step (1) to obtain the hexamethylenediamine product and heavy components; and (3) Under the conditions of the ammonia decomposition reaction, subject the heavy components to ammonia decomposition to obtain ammonia decomposition reaction products, and return the ammonia decomposition reaction products to step (2).

[0013] The ammonia decomposition described in the present invention refers to the decomposition of high-carbon amines into low-carbon amines. Specifically, under the action of a catalyst, heavy components, that is, C12 and C12+ amines defined above in the present invention, through a chemical reaction, produce low-carbon amines such as hexamethylenediamine. It is emphasized that this is what is meant.

[0014] The method of the present invention has the following beneficial effects: (1) By decomposing the heavy components from the ammoniation reaction by ammonia decomposition, the present invention not only improves the yield of hexamethylenediamine, but also reduces the discharge amount of waste liquid from the ammoniation reaction, thereby greatly reducing the production cost of hexamethylenediamine.

[0015] (2) The technical process of the present invention is essentially safe, does not contain highly toxic nitrile chemical substances, and the technical route is safe and environmentally friendly. The hexamethylenediamine product obtained by the present invention has stable production volume, high purity, high yield, and few impurities.

[0016] (3) For enterprises having hexanediol or upstream raw material resources, the present invention provides a method for preparing hexamethylenediamine by ammoniation of alcohol. This method has a simple process flow, saves equipment investment, and has a high economic added value of the product.

[0017] 〔Detailed Disclosure〕 The endpoint values and any values within the ranges disclosed in this specification are not limited to the exact ranges or values, and it should be understood that these ranges or values include values approximating these ranges or values. For numerical ranges, one or more new numerical ranges can be obtained by combining the endpoint values of each range with each other, by combining the endpoint values of each range with individual point values, and by combining individual point values with each other, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The present invention provides a method for preparing hexamethylenediamine, and this method comprises the following steps: (1) Subjecting hexanediol and ammonia to an ammoniation reaction under ammoniation reaction conditions, optionally in the presence of a first solvent, to obtain an ammoniation reaction product; (2) Separating the ammoniation reaction product from step (1) to obtain a hexamethylenediamine product and a heavy component; and (3) Subjecting the heavy component to an ammonia decomposition reaction under ammonia decomposition reaction conditions to obtain an ammonia decomposition reaction product, and returning the ammonia decomposition reaction product to step (2).

[0019] According to the present invention, the solvent (i.e., the first solvent) is not essential and is optionally used in the ammoniation reaction between hexanediol and ammonia; therefore, the ammoniation reaction may be carried out in the presence or absence of the solvent. In the prior art, the ammoniation reaction is usually carried out at atmospheric or low pressure, and ammonia is in the gas phase; therefore, in order to carry out the ammoniation reaction efficiently, it is necessary to add a solvent to dissolve the ammonia gas in the reaction flow. In the present invention, the pressure of the ammoniation reaction is relatively high, and ammonia is liquefied and in the liquid phase; therefore, the ammoniation reaction between hexanediol and liquid ammonia can be carried out in the absence of a solvent. The solvent added in the present invention is for dissolving the ammoniation reaction raw materials, as well as reaction products such as hexanediol, hexamethylenediamine, aminohexanol, hexamethyleneimine, and N-(6-aminohexyl)hexamethyleneimine.

[0020] According to the present invention, in the ammoniation reaction of hexanediol and ammonia, the molar ratio of ammonia to hexanediol is 10 to 90:1, preferably 10 to 80:1, for example 15 to 70:1, 15 to 60:1, and 20 to 45:1. The ammoniation reaction is carried out in the presence of hydrogen, and the molar ratio of hydrogen to hexanediol is 0.05 to 25:1, preferably 0.05 to 20:1, for example 0.1 to 10:1, 0.2 to 5:1, and 0.3 to 3:1. The molar ratios of ammonia, hydrogen, and hexanediol refer to the molar ratios in the mixture at the inlet of the ammoniation reactor.

[0021] According to the present invention, in the ammoniation reaction between hexanediol and ammonia, the temperature of the ammoniation reaction is 100°C to 300°C, preferably 100°C to 250°C, for example 120°C to 250°C, 130°C to 210°C, and 140°C to 200°C. The pressure of the ammoniation reaction is 4 MPaG to 25 MPaG, preferably 6 MPaG to 20 MPaG, for example 6 MPaG to 18 MPaG, 8 MPaG to 16 MPaG, and 10 MPaG to 14 MPaG. The liquid volume space velocity of fresh hexanediol is 0.01 h -1~15 h -1 、 preferably 0.01 h -1 ~10 h -1 、 for example, 0.03 h -1 ~8 h -1 、 0.05 h -1 ~4 h -1 、 and 0.1 h -1 ~2 h -1 It is.

[0022] The ammoniation reaction catalyst used during the ammoniation reaction of the present invention may be any type of catalyst in the art that can ammoniate hexanediol to produce hexamethylenediamine. For example, it is the ammoniation reaction catalyst in CN114433086A, CN114433087A, CN114433113A, etc. Preferably, the catalyst includes a carrier, an active component supported on the carrier, and optionally an auxiliary agent. The carrier includes a doping element, alumina, and optionally other carriers. The other carriers are selected from at least one of silicon oxide, molecular sieve, and diatomaceous earth. The pore volume of the carrier with a pore diameter of less than 7.5 nm is less than 20% of the pore volume of the carrier. The pore volume of the carrier with a pore diameter of less than 9 nm is less than 40% of the pore volume of the carrier. The pore volume of the carrier with a pore diameter exceeding 27 nm is less than 5% of the pore volume of the carrier. The ammonia adsorption capacity of the carrier is 0.3 mmol / g to 0.6 mmol / g. The L acid of the carrier accounts for more than 90% of the total of L acid and B acid. The active component is cobalt and / or nickel.

[0023] According to the ammoniation reaction catalyst of the present invention, preferably, the carrier is selected from alumina incorporating at least one of silicon oxide, molecular sieve, and diatomaceous earth, and alumina not incorporating. The content of the alumina carrier in the carrier is 65 wt% or more, preferably 75 wt% or more, based on the total amount of the alumina carrier and other carriers.

[0024] According to the ammonia reaction catalyst of the present invention, the carrier may preferably further contain doping elements, the doping element content accounting for 0.05 wt% to 3 wt%, more preferably 0.08 wt% to 2 wt%, and even more preferably 0.1 wt% to 1.5 wt%, of the total weight of components other than doping elements in the carrier. Components other than doping elements mainly refer to alumina and any other carrier in the carrier.

[0025] According to the ammonia reaction catalyst of the present invention, preferably, the doping elements doped into the support are derived from acid radical ions other than chloride ions. Since the doped elements are introduced during the preparation of the support, the doped elements are mainly present in the bulk phase of the support.

[0026] According to the ammonia reaction catalyst of the present invention, preferably, the acid radical ion may be at least one selected from nonmetallic acid radical ions, and more preferably, at least one selected from borate ions, fluoride ions, phosphate ions, sulfate ions, and selenite ions. The doping element is preferably selected from at least one of boron, fluorine, phosphorus, sulfur, and selenium.

[0027] According to the ammonia reaction catalyst of the present invention, preferably, the pore volume of a support with a pore diameter of less than 7.5 nm accounts for 5% to 17%, more preferably 5% to 10%, of the support's pore volume; the pore volume of a support with a pore diameter of 7.5 nm or more and less than 9 nm accounts for 5% to 17%, the pore volume of a support with a pore diameter of 9 nm or more and 27 nm accounts for 61% to 89.5%, and the pore volume of a support with a pore diameter greater than 27 nm accounts for 0.5% to 5%, more preferably 0.5% to 3%. The inventors of the present invention have found that catalysts having a pore structure that satisfies this preferred embodiment have superior catalytic performance.

[0028] According to the ammonia reaction catalyst of the present invention, preferably, the ammonia adsorption capacity of the support is preferably 0.3 mmol / g to 0.5 mmol / g.

[0029] According to the ammonia reaction catalyst of the present invention, preferably, the L acid of the support accounts for 92% to 100%, preferably 96% to 100%, of the total of L acid and B acid. The proportion of L acid is measured by pyridine probe adsorption spectroscopy.

[0030] According to the ammonia reaction catalyst of the present invention, preferably the specific surface area of ​​the support is 105 m². 2 / g~220m 2 The concentration is per gram, and the pore volume of the carrier is 0.4 ml / g to 1.1 ml / g.

[0031] According to the ammonia reaction catalyst of the present invention, the content of the active ingredient may preferably be 5g to 42g, more preferably 10g to 35g, per 100g of a carrier consisting of components other than the doping element. According to the present invention, the catalyst may further contain an auxiliary agent in order to better exhibit the performance of the catalyst of the present invention, optimize the ratio of reaction products, and reduce undesirable side reactions. The auxiliary agent may be at least one selected from the elements of Group VIB, Group VIIB, Group IB, Group IIB and lanthanides, and preferably at least one of Cr, Mo, W, Mn, Re, Cu, Ag, Au, Zn, La and Ce.

[0032] According to the ammonia reaction catalyst of the present invention, the content of the auxiliary agent may preferably be 0g to 10g, more preferably 0.5g to 6g, per 100g of carrier consisting of components other than doping elements.

[0033] The reactor used in the ammoniaization reaction is not particularly limited in this invention and may be any reactor capable of carrying out a gas-liquid-solid reaction. Considering the need to thoroughly react the reaction materials, improve reaction efficiency, and enhance the reaction effect, the reactor used in the ammoniaization reaction is preferably a fixed-bed reactor, an autoclave, a trickle bed reactor, or a fluidized bed reactor, or any other reactor capable of ensuring stable operation of the reaction.

[0034] According to the present invention, in a method for preparing hexamethylenediamine, step (2) further comprises: separating the ammonia reaction product to obtain a stream containing hexamethyleneimine and water. Optionally, the stream containing hexamethyleneimine and water is separated to obtain a stream containing hexamethyleneimine, and at least a portion of the stream containing hexamethyleneimine is returned to step (1).

[0035] To further improve the yield of hexamethylenediamine, the stream containing hexamethyleneimine and water may be separated to obtain a stream containing hexamethyleneimine, and at least a portion of the hexamethyleneimine-containing stream is returned to step (1). According to the present invention, taking into account the energy consumption of the system, the yield of hexamethylenediamine and the service life of the catalyst, preferably the weight ratio of the hexamethyleneimine-containing stream returned to step (1) to fresh hexanediol is 0.1 to 26:1, more preferably 0.3 to 24:1, for example 0.5 to 20:1, 1 to 15:1, 2 to 10:1, and 3 to 8:1.

[0036] According to the present invention, in a method for preparing hexamethylenediamine, step (2) further comprises: separating the ammonia reaction product to obtain a stream containing aminohexanol. Optionally, at least a portion of the aminohexanol-containing stream is returned to step (1).

[0037] To further improve the yield of hexamethylenediamine, at least a portion of the aminohexanol-containing flow can be returned to step (1). According to the present invention, taking into account the energy consumption of the system, the yield of hexamethylenediamine, and the service life of the catalyst, the weight ratio of the aminohexanol-containing flow returned to step (1) to fresh hexanediol is preferably 0.1 to 26:1, more preferably 0.3 to 24:1, for example 0.5 to 20:1, 1 to 15:1, 2 to 10:1, and 3 to 8:1. The aminohexanol-containing flow may also contain 0 wt% to 30 wt% hexanediol, 0 wt% to 2 wt% hexamethylenediamine, and small amounts of other components (e.g., heavy components).

[0038] Note that in the initial stages of the reaction, the amount of hexamethyleneimine produced by the ammoniaization reaction is small and cannot satisfy the weight ratio of the hexamethyleneimine-containing stream to fresh hexanediol specified above. Therefore, in the initial stages of the reaction, all of the hexamethyleneimine-containing stream is returned to the ammoniaization reaction. During the stable operation stage of the reaction, the amount of hexamethyleneimine produced cumulatively by the ammoniaization reaction is sufficiently large, and at this point, it is sufficient to ensure that the returned hexamethyleneimine-containing stream satisfies the weight ratio specified above. The same applies to the aminohexanol produced by the ammoniaization reaction. Note that the weight ratio of the stream returned to step (1) to fresh hexanediol shown in the examples herein is the mass ratio during the stable operation stage of the reaction.

[0039] According to the present invention, in a method for preparing hexamethylenediamine, step (2) further includes: separating the ammonia reaction product to obtain a stream containing hexamethyleneimine and water, separating the stream containing hexamethyleneimine and water to obtain a stream containing hexamethyleneimine, and returning at least a portion of the stream containing hexamethyleneimine to step (1); and separating the ammonia reaction product to obtain a stream containing aminohexanol, and returning at least a portion of the stream containing aminohexanol to step (1). This makes it possible to further increase the yield of hexamethylenediamine.

[0040] According to the present invention, taking into account the energy consumption of the system, the yield of hexamethylenediamine, and the service life of the catalyst, preferably the weight ratio of the flow containing hexamethyleneimine to the flow containing aminohexanol, which is returned to step (1), is 0.1 to 5:1, for example 0.2 to 4.5:1, 0.3 to 4:1, 0.4 to 3.5:1, 0.5 to 3:1, 0.6 to 2.5:1, 0.7 to 2:1, and 0.8 to 1.5:1. Preferably, the ratio of the total weight of the hexamethyleneimine-containing stream and the aminohexanol-containing stream returned to step (1) to the weight of fresh hexanediol is 0.1 to 30:1, preferably 0.3 to 25:1, for example 0.4 to 20:1, 0.5 to 15:1, 0.8 to 10:1, 1 to 8:1, 1.5 to 6:1, and 2 to 5:1.

[0041] Note that in the initial stages of the reaction, the amounts of hexamethyleneimine and aminohexanol produced by the ammoniation reaction are small, and the combined weight of the hexamethyleneimine-containing stream and the aminohexanol-containing stream cannot satisfy the weight ratio of fresh hexanediol specified above. Therefore, in the initial stages of the reaction, all of the hexamethyleneimine-containing stream and the aminohexanol-containing stream are returned to the ammoniation reaction. During the stable operation phase of the reaction, the accumulation of hexamethyleneimine and aminohexanol produced cumulatively by the ammoniation reaction is relatively large, and at this point, it is sufficient to ensure that the weight ratio of the hexamethyleneimine-containing stream and the aminohexanol-containing stream returned satisfies the weight ratio specified above. The weight ratio of the stream returned to step (1) shown in the examples herein, relative to fresh hexanediol, is the mass ratio during the stable operation phase of the reaction.

[0042] According to the present invention, preferably, the conditions for separating the ammonia reaction product are such that the hexamethyleneimine content in the stream containing hexamethyleneimine and water is 35 wt% to 95 wt%, more preferably 40 wt% to 85 wt%, and most preferably 50 wt% to 80 wt%; and the water content is 5 wt% to 65 wt%, more preferably 20 wt% to 50 wt%, and most preferably 30 wt% to 40 wt%.

[0043] Preferably, the approach for separating the ammonia reaction product is as follows: subjecting the ammonia reaction product to a first separation to obtain a stream containing hexamethyleneimine and water, and then subjecting it to a second separation to obtain a stream containing hexamethylenediamine product and aminohexanol; more preferably, the first and second separations each independently include at least one of distillation, membrane separation and pressure swing adsorption.

[0044] Preferably, the approach for separating the ammonia reaction product is as follows: subjecting the ammonia reaction product to a first separation to obtain a stream containing hexamethyleneimine and water; then subjecting it to a second separation to obtain a stream containing hexamethylenediamine product, as well as aminohexanol and heavy components; then subjecting it to a third separation to obtain a stream containing aminohexanol and heavy components; more preferably, the first, second, and third separations each independently include at least one of distillation, membrane separation, and pressure swing adsorption.

[0045] In the present invention, for example, when distillation is used, the conditions for the first separation are: a theoretical number of plates of 10 to 80 (for example, a range consisting of 10, 20, 30, 40, 50, 60, 70, 80, and any of the above point values), and an absolute pressure of 1 kPa to 600 kPa (for example, 1 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa, 600 kPa, and The conditions for the second separation may include: an operating pressure (within the range of any of the above point values), a column bottom temperature of 90°C to 300°C, and a reflux ratio of 0.1 to 15; the conditions for the second separation may include: a theoretical plate number of 10 to 80 (e.g., a range of 10, 20, 30, 40, 50, 60, 70, 80, and any of the above point values), and an absolute pressure of 1 kPa to 600 kPa (e.g., 1 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 100 kPa). a) Operating pressure (a range consisting of 200kPa, 300kPa, 400kPa, 500kPa, 600kPa and any of the above point values), bottom column temperature of 130°C to 380°C, and reflux ratio of 0.1 to 40; and third separation conditions include: theoretical plate number of 10 to 100 (e.g., range consisting of 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 and any of the above point values), 1kPa to 110 The operating pressure may include 0 kPa (absolute pressure, e.g., a range consisting of 1 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa, 600 kPa, 700 kPa, 800 kPa, 900 kPa, 1000 kPa, 1100 kPa, and any of the above point values), a column bottom temperature of 150°C to 400°C, and a reflux ratio of 0.1 to 70. The separation conditions of the present invention can achieve a purity of over 99.7 wt% of the hexamethylenediamine product.

[0046] More preferably, the approach for separating the ammonia reaction products is as follows: the ammonia reaction products enter a first distillation column for separation, obtaining a stream containing hexamethyleneimine and water at the top of the first distillation column; the bottom stream of the first distillation column is sent to a second distillation column for separation, obtaining the hexamethylenediamine product at the top of the column and a stream containing hexanediol, aminohexanol and heavy components at the bottom of the column; the bottom stream of the second distillation column is sent to a third distillation column for separation, obtaining a stream containing hexanediol and aminohexanol at the top of the third distillation column and heavy components at the bottom of the column.

[0047] According to the present invention, preferably, the operating conditions of the first distillation column include: a column bottom temperature of 90°C to 300°C, a column top temperature of 30°C to 65°C, a reflux ratio of 0.1 to 10, a column top operating pressure of -0.1 MPaG to 0.5 MPaG, and a theoretical number of 10 to 30.

[0048] According to the present invention, preferably, the operating conditions of the second distillation column include: a column bottom temperature of 120°C to 320°C, a column top temperature of 40°C to 85°C, a reflux ratio of 0.5 to 30, a column top operating pressure of -0.1 MPaG to 0.5 MPaG, and a theoretical number of 10 to 45.

[0049] According to the present invention, preferably, the operating conditions of the third distillation column include: a column bottom temperature of 150°C to 360°C, a column top temperature of 40°C to 85°C, a reflux ratio of 1 to 65, a column top operating pressure of -0.1 MPaG to 0 MPaG, and a theoretical plate number of 15 to 85.

[0050] According to the present invention, the approach for separating a stream containing hexamethyleneimine and water may be dehydration, which is commonly used in the art. However, to further reduce the water content in the hexamethyleneimine-containing stream, the dehydration preferably includes at least one of atmospheric distillation, vacuum distillation, pressure swing distillation, azeotropic distillation, membrane separation, extractive distillation, adsorption dehydration, biological dehydration, and centrifugation. As the azeotropic agent used in azeotropic distillation, at least one of cyclohexane, n-hexane, trimethylpentane, 1-methyl-4-isopropylbenzene, 1,4-dioxane, phenol, cresol, dibutyl ether, diamyl ether, and diisoamyl ether can be used. The operating conditions for azeotropic distillation are specifically selected according to the different azeotropic points formed by the particular azeotropic agent, water, and hexamethyleneimine.

[0051] Preferably, the water content of the hexamethyleneimine-containing flow returned to step (1) is less than 3 wt%, preferably less than 1.5 wt%, and more preferably less than 1 wt%.

[0052] According to a preferred embodiment of the present invention, dehydration of a flow containing hexamethyleneimine and water may be performed by membrane separation dehydration, the operating conditions of which include: a membrane inlet pressure of 0 MPaG to 5 MPaG, for example 1 MPaG to 4 MPaG, and a temperature of 10°C to 350°C, for example 10°C to 200°C, for example 15°C to 190°C.

[0053] According to a preferred embodiment of the present invention, dehydration of the flow containing hexamethyleneimine and water may be performed by azeotropic distillation, which is carried out in a distillation column. The operating conditions of the distillation column include: a weight ratio of the azeotrope to the flow containing hexamethyleneimine of 10 to 100:1, a bottom temperature of 120°C to 200°C, a top temperature of 80°C to 150°C, a reflux ratio of 0.1 to 20, a top operating pressure of 0 MPaG to 3 MPaG, and 10 to 80 stages.

[0054] According to a preferred embodiment of the present invention, dehydration of a flow containing hexamethyleneimine and water can be carried out by simultaneously using distillation and membrane separation or pressure swing distillation. For example, a flow containing hexamethyleneimine and water is distilled in a distillation column to obtain a flow containing hexamethyleneimine at the bottom of the column, and the flow at the top of the column is subjected to membrane separation or pressure swing distillation to obtain wastewater. Preferably, the conditions for distilling the flow containing hexamethyleneimine and water include a bottom column temperature of 60°C to 250°C and a top column operating pressure of -0.09 MPaG to 1 MPaG. Preferably, the membrane separation conditions include a membrane inlet temperature of 80°C to 350°C and a membrane inlet pressure of 0 MPaG to 5 MPaG. The pressure swing operating range for pressure swing distillation may be 0 MPaG to 8 MPaG, preferably 0 MPaG to 5 MPaG; more preferably, pressure swing distillation is performed in a high-pressure column and a low-pressure column, where the top pressure of the high-pressure column is 1 MPaG to 8 MPaG and the bottom temperature is 150°C to 240°C, and the top pressure of the low-pressure column is less than 1 MPaG and the bottom temperature is 50°C to 130°C.

[0055] According to the present invention, preferably, before separating the stream containing hexamethyleneimine and water, the hexamethylenediamine product, the aminohexanol product, and the heavy components from the ammonia reaction product, the ammonia reaction product is first pre-separated to recover hydrogen and ammonia from the ammonia reaction product; the recovered hydrogen and ammonia are first condensed to obtain circulating ammonia (liquid phase), then compressed to obtain circulating hydrogen (gas phase), and the circulating hydrogen and circulating ammonia are returned to the ammonia reaction. Preferably, the pre-separation includes at least one of flash evaporation, distillation, and stripping. The pre-separation method may also employ other methods that can recover circulating hydrogen and ammonia from the ammonia reaction product. More preferably, the hydrogen content in the circulating hydrogen is 5 wt% to 40 wt%, and the ammonia content is 60 wt% to 95 wt%; the ammonia content in the circulating ammonia is 40 wt% to 100 wt%, the water content is 0 wt% to 1 wt%, the hexamethylenediamine content is 0 wt% to 1 wt%, and the hexamethyleneimine content is 0 wt% to 1 wt%. Since some ammonia and hydrogen are consumed during the ammoniaization reaction, and small amounts of hydrogen and ammonia are lost during the hydrogen and ammonia recovery process, it is necessary to replenish fresh ammonia and hydrogen during the ammoniaization reaction to maintain the molar ratio of hexanediol (including freshly replenished hexanediol and hexanediol in the circulating flow), ammonia, and hydrogen in the ammoniaization reaction system.

[0056] To ensure the efficient use of hydrogen and ammonia and reduce the overall energy consumption of the process, the preliminary separation conditions are preferably such that the hydrogen recovery rate exceeds 99% and the ammonia recovery rate exceeds 98%. In the present invention, the preliminary separation may employ multi-stage reduced-pressure flash evaporation, which may include at least two stages of flash evaporation, where the flash evaporation pressure decreases in a gradient from 1 MPa to 8 MPa, and the pressure of the final stage of flash evaporation is 0.5 MPaG to 1 MPaG. For example, if four-stage flash evaporation is employed, the flash evaporation pressures from the first to the fourth stage are 7 MPaG to 15 MPaG, 4 MPaG to 7 MPaG, 1 MPaG to 4 MPaG, and 0.1 MPaG to 1 MPaG, respectively. For example, if three-stage flash evaporation is employed, the flash evaporation pressures from the first to the third stage are 7 MPaG to 15 MPaG, 1 MPaG to 7 MPaG, and 0.5 MPaG to 3 MPaG, respectively.

[0057] According to the present invention, in a method for preparing hexamethylenediamine, step (4) further comprises: dissolving a heavy component in a second solvent before the ammonia decomposition reaction, followed by ammonia decomposition. The second solvent is a solvent in which the solubility of ammonia reaction raw materials and reaction products such as hexanediol, hexamethylenediamine, aminohexanol, hexamethyleneimine, and dihexamethylenetriamine is greater than 0.05 g / g, and is, for example, at least one of tetrahydrofuran, 1,4-dioxane, n-hexane, cyclohexane, tert-butanol, etc. The weight ratio of the second solvent to the heavy component is 1 to 20:1, preferably 2 to 18:1, more preferably 3 to 15:1.

[0058] The second solvent for dissolving the heavy components may be the same type as the first solvent used in the ammoniation reaction (if a solvent exists). The solvent for dissolving the heavy components may be a newly introduced solvent or a stream of solvent separated from the ammoniation reaction products (if a solvent exists in the ammoniation reaction). Typically, in the initial stages of the reaction, the amount of solvent in the system is small, and at this point, fresh solvent may be used to dissolve the heavy components. After the reaction has been running for a certain period, the amount of solvent in the system is relatively large, and the stream of solvent separated from the ammoniation reaction products can meet the amount of solvent required for the ammoniation and ammonia decomposition reactions. At this point, no new solvent is introduced into the system; instead, a portion of the stream of solvent separated from the ammoniation reaction products is returned to the ammoniation reaction, and the other portion is used to dissolve the heavy components. Since the solvent circulating in the system is inevitably lost during the reaction, fresh solvent should be periodically replenished into the system.

[0059] According to the present invention, in step (3), ammonia decomposition is carried out in the presence of hydrogen and ammonia, and the molar ratio of hydrogen:ammonia:heavy component is calculated as 0.1~20:10~150:1, preferably 0.2~15:15~120:1, more preferably 0.2~10:20~100:1, and most preferably 0.3~8:30~90:1, with the heavy component being dihexamethylenetriamine.

[0060] According to the present invention, preferably, the conditions for the ammonia decomposition reaction are: a reaction temperature of 120°C to 300°C, preferably 150°C to 270°C; a reaction pressure of 9 MPaG to 25 MPaG, preferably 10 MPaG to 22 MPaG; and a liquid volume space velocity of heavy components of 0.01 h. -1 ~8h -1 Preferably 0.05h -1 ~5h -1 This includes being.

[0061] In the present invention, the ammonia decomposition catalyst used in the ammonia decomposition reaction can be prepared according to the following method: (1) Preparation of the carrier: A mixture of pseudoboehmite, silica sol, and calcium nitrate is brought into contact with an aqueous solution containing nitric acid and phosphoric acid, and then kneaded, dried, and calcined in sequence; (2) The support is impregnated with an aqueous solution containing nickel sulfate, lanthanum acetate, and indium nitrate, dried at 100°C to 140°C for 2 to 6 hours, and then calcined at 350°C to 450°C for 2 to 6 hours.

[0062] According to the method for preparing the ammonia decomposition catalyst of the present invention, preferably in step (1), the amount of silica sol is 0.6 g to 0.8 g per 1 g of pseudoboehmite, the amount of calcium nitrate is 0.1 g to 0.4 g, and the amount of aqueous solution containing nitric acid and phosphoric acid is 0.2 g to 0.5 g.

[0063] According to the method for preparing the ammonia decomposition catalyst of the present invention, preferably in step (1), the aqueous solution containing nitric acid and phosphoric acid has a nitric acid content of 10 wt% to 25 wt% and a phosphoric acid content of 5 wt% to 15 wt%.

[0064] According to the method for preparing the ammonia decomposition catalyst of the present invention, preferably in step (1), the drying temperature is 100°C to 140°C and the drying time is 1 hour to 6 hours.

[0065] According to the method for preparing the ammonia decomposition catalyst of the present invention, preferably in step (2), the amount of nickel sulfate per gram of support is 0.6 g to 0.85 g, the amount of lanthanum acetate is 0.06 g to 0.08 g, and the amount of indium nitrate is 0.055 g to 0.065 g.

[0066] According to the method for preparing the ammonia decomposition catalyst of the present invention, preferably in step (2), in an aqueous solution containing nickel sulfate, lanthanum acetate, and indium nitrate, the concentration of nickel sulfate is 20 wt% to 25 wt%, the concentration of lanthanum acetate is 1.5 wt% to 2.5 wt%, and the concentration of indium nitrate is 1.5 wt% to 2.5 wt%. The impregnation method is preferably an equivolute impregnation method, and the impregnation may be carried out in multiple stages.

[0067] The present invention also found that by returning a stream containing aminohexanol and a stream containing hexamethyleneimine to the ammoniaization reaction in a certain proportion, and subjecting the heavy components from the ammoniaization reaction to ammonia decomposition, the yield of hexamethylenediamine is not only significantly improved, but the amount of waste liquid discharged from the ammoniaization reaction is reduced, thereby significantly lowering the production cost of hexamethylenediamine.

[0068] The presence of the first solvent in the ammoniation reaction In the method for preparing hexamethylenediamine of the present invention, Step (1) includes: subjecting hexanediol and ammonia to an ammonia reaction in a first solvent under ammonia reaction conditions to obtain an ammonia reaction product; and Step (2) includes separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine, a first solvent and water, a hexamethylenediamine product, a stream containing aminohexanol, and a heavy component.

[0069] In one embodiment of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction in a first solvent under ammonia reaction conditions to obtain an ammonia reaction product; (2) Separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine, a first solvent and water, a hexamethylenediamine product, a stream containing aminohexanol, and heavy components; and (3) The process includes the step of subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2).

[0070] In embodiments of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction in a first solvent under ammonia reaction conditions to obtain an ammonia reaction product; (2) Separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine, the first solvent and water, a stream containing the hexamethylenediamine product and aminohexanol, and a heavy component; then separating the stream containing hexamethyleneimine, the first solvent and water to obtain a stream containing hexamethyleneimine and a stream containing the first solvent, and returning at least a portion of the stream containing hexamethyleneimine and at least a portion of the stream containing the first solvent to step (1); and (3) The process includes the step of subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2).

[0071] In one embodiment of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction in a first solvent under ammonia reaction conditions to obtain an ammonia reaction product; (2) Separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine, the first solvent and water, a stream containing the hexamethylenediamine product and aminohexanol, and a heavy component, returning at least a portion of the aminohexanol-containing stream to step (1), then separating the stream containing hexamethyleneimine, the first solvent and water to obtain a stream containing hexamethyleneimine and a stream containing the first solvent, returning at least a portion of the hexamethyleneimine-containing stream and at least a portion of the first solvent stream to step (1); and (3) The process includes subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2), with or without separation.

[0072] Introducing a solvent into the ammoniaization reaction helps maintain a uniform temperature distribution in the system, reducing reaction hotspots, improving reaction stability, preventing solid phase crystallization and separation throughout the system, lowering the operating temperature of each component in the apparatus, and avoiding the enormous investment required for equipment insulation. Furthermore, introducing a solvent effectively dissolves hexanediol and by-products such as hexamethyleneimine and aminohexanol generated by the ammoniaization reaction, helping to resolve pipeline clogging problems throughout the entire operating cycle, especially in the separation process.

[0073] In the present invention, the first solvent is introduced in a single step (together with hexanediol in the initial stage of the reaction). In the initial stage of the reaction (before the circulating flow is returned to the ammoniaization reaction), the molar ratio of the first solvent to hexanediol is 0.1 to 10:1, preferably 0.15 to 10:1, and more preferably 0.25 to 9:1. However, it is understood that the first solvent will be lost during the circulation and purification processes. To ensure the amount of circulating solvent in the system, a small amount of fresh solvent can be replenished during the process of the first solvent circulation to maintain a constant amount of solvent in the system. According to the present invention, the first solvent is a solvent having a solubility of more than 0.1 g / g of ammoniaization reaction raw materials and reaction products, such as hexanediol, hexamethylenediamine, aminohexanol, and hexamethyleneimine, and examples include at least one of tetrahydrofuran, 1,4-dioxane, n-hexane, cyclohexane, tert-butanol, tetramethylenesulfone, and glycerol.

[0074] Preferably, in step (1), the molar ratio of ammonia to hexanediol during the ammoniation reaction is 10 to 80:1, preferably 20 to 45:1; the ammoniation reaction is carried out in the presence of hydrogen, and the molar ratio of hydrogen to hexanediol is 0.05 to 20:1, preferably 0.2 to 5:1. The molar ratios of ammonia, hydrogen, and hexanediol refer to the molar ratios in the mixture at the inlet of the ammoniation reactor.

[0075] Preferably, in step (1), the temperature of the ammonia reaction is 100°C to 250°C, preferably 130°C to 210°C; the pressure of the ammonia reaction is 6 MPaG to 18 MPaG, preferably 8 MPaG to 16 MPaG; and the liquid volume space velocity of fresh hexanediol is 0.01 h -1 ~10h -1 Preferably 0.05h -1 ~4h -1 That is the case.

[0076] Preferably, the weight ratio of the stream containing hexamethyleneimine and the stream containing aminohexanol returned to step (1) is 0.1 to 5:1, for example 0.2 to 4.5:1, 0.3 to 4:1, 0.4 to 3.5:1, 0.5 to 3:1, 0.6 to 2.5:1, 0.7 to 2:1, and 0.8 to 1.5:1, which can further improve the yield of hexamethylenediamine. Since the solvent only serves to dissolve the reaction raw materials and reaction products, there is no limit to the amount of solvent returned; the entire amount may be returned, or only a portion may be returned. When returning a portion of the solvent to step (1), for example, the weight ratio of the flow containing hexamethyleneimine, the flow of the first solvent, and the flow containing aminohexanol can be 0.1-5:0.3-40:1, preferably 0.1-2.5:0.3-10:1, and more preferably 0.5-2:1-10:1.

[0077] Preferably, the ratio of the total weight of the hexamethyleneimine-containing stream and the aminohexanol-containing stream returned to step (1) to the weight of fresh hexanediol is 0.1 to 30:1, preferably 0.3 to 25:1, for example 0.4 to 20:1, 0.5 to 15:1, 0.8 to 10:1, 1 to 8:1, 1.5 to 6:1, and 2 to 5:1, in order to further improve the yield of hexamethylenediamine.

[0078] Preferably, step (2) further comprises: recovering hydrogen and ammonia from the ammonia reaction product before separating the ammonia reaction product into a stream containing hexamethyleneimine, a first solvent and water, a stream containing hexamethylenediamine product and aminohexanol, and heavy components; the recovered hydrogen and ammonia are first condensed to obtain circulating ammonia (liquid phase), then compressed to obtain circulating hydrogen (gas phase), and the circulating hydrogen and circulating ammonia are returned to the ammonia reaction. More preferably, in the circulating hydrogen, the hydrogen content is 5 wt% to 40 wt%, and the ammonia content is 60 wt% to 95 wt%; in the circulating ammonia, the ammonia content is 40 wt% to 100 wt%, the solvent content is 0 wt% to 60 wt%, the water content is 0 wt% to 1 wt%, the hexamethylenediamine content is 0 wt% to 1 wt%, and the hexamethyleneimine content is 0 wt% to 1 wt%. Since some ammonia and hydrogen are consumed during the ammoniaization reaction, and small amounts of hydrogen and ammonia are lost during the hydrogen and ammonia recovery process, it is necessary to replenish fresh ammonia and hydrogen during the ammoniaization reaction to maintain the molar ratio of hexanediol (including newly replenished hexanediol and hexanediol in the circulating flow), ammonia, and hydrogen in the ammoniaization reaction system.

[0079] Preferably, step (2) includes: feeding the ammonia reaction product, from which ammonia and hydrogen have been optionally removed, into a first distillation column for separation to obtain a stream containing hexamethyleneimine, water and a first solvent at the top of the first distillation column; feeding the bottom stream of the first distillation column into a second distillation column for separation to obtain a hexamethylenediamine product at the top of the column and a stream containing hexanediol, aminohexanol and a heavy component at the bottom of the column; and feeding the bottom stream of the second distillation column into a third distillation column for separation to obtain a stream containing hexanediol and aminohexanol at the top of the third distillation column and a heavy component at the bottom of the column.

[0080] Preferably, the operating conditions for the first distillation column include: a bottom temperature of 90°C to 300°C, a top temperature of 30°C to 65°C, a reflux ratio of 0.1 to 10, a top operating pressure of -0.1 MPaG to 0.5 MPaG, and 10 to 30 stages.

[0081] Preferably, the operating conditions for the second distillation column include: a bottom temperature of 120°C to 320°C, a top temperature of 40°C to 85°C, a reflux ratio of 0.5 to 30, a top operating pressure of -0.1 MPaG to 0.5 MPaG, and 10 to 45 stages.

[0082] Preferably, the operating conditions for the third distillation column include: a bottom temperature of 150°C to 360°C, a top temperature of 40°C to 85°C, a reflux ratio of 1 to 65, a top operating pressure of -0.1 MPaG to 0 MPaG, and 15 to 85 stages.

[0083] Preferably, step (2) includes: distilling a stream containing hexamethyleneimine, a first solvent, and water in a distillation column to obtain a stream containing hexamethyleneimine at the bottom of the column, and subjecting the stream at the top of the column to membrane separation or pressure swing distillation to obtain a stream of solvent and wastewater. Preferably, the conditions for distilling the stream containing hexamethyleneimine, a first solvent, and water include a bottom column temperature of 60°C to 250°C and a top column operating pressure of -0.09 MPaG to 1 MPaG. Preferably, the membrane separation conditions include a membrane inlet temperature of 80°C to 350°C and a membrane inlet pressure of 0 MPaG to 5 MPaG. The pressure swing operating range for pressure swing distillation may be 0 MPaG to 8 MPaG, preferably 0 MPaG to 5 MPaG; more preferably, pressure swing distillation is performed in a high-pressure column and a low-pressure column, where the top pressure of the high-pressure column is 1 MPaG to 8 MPaG and the bottom temperature is 150°C to 240°C; and the top pressure of the low-pressure column is less than 1 MPaG and the bottom temperature is 50°C to 130°C.

[0084] Preferably, the ammonia decomposition reaction products are roughly separated by distillation, and the conditions for the rough separation column for rough separation include: a column bottom temperature of 380°C to 520°C, a column top operating pressure of -0.05 MPag to 1 MPag, and a reflux ratio of 2 to 50.

[0085] Absence of the first solvent in the ammoniation reaction In the method for preparing hexamethylenediamine of the present invention, Step (1) includes the step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, in the absence of a first solvent, to obtain an ammonia reaction product.

[0086] In one embodiment of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, in the absence of a first solvent, to obtain an ammonia reaction product; (2) A step of separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine and water, a hexamethylenediamine product, a stream containing aminohexanol, and heavy components; and (3) The process includes the step of subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2).

[0087] In one embodiment of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, in the absence of a first solvent, to obtain an ammonia reaction product; (2) Separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine and water, a stream containing hexamethylenediamine product, an aminohexanol, and heavy components, then separating the stream containing hexamethyleneimine and water to obtain a stream containing hexamethyleneimine, and returning at least a portion of the stream containing hexamethyleneimine to step (1); and (3) The process includes the step of subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2).

[0088] In one embodiment of the present invention, a method for preparing hexamethylenediamine is as follows: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, in the absence of a first solvent, to obtain an ammonia reaction product; (2) Separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine and water, a hexamethylenediamine product, a stream containing aminohexanol, and heavy components, returning at least a portion of the aminohexanol-containing stream to step (1), separating the stream containing hexamethyleneimine and water to obtain a stream containing hexamethyleneimine, and returning at least a portion of the hexamethyleneimine-containing stream to step (1); and (3) The process includes subjecting heavy components to ammonia decomposition under ammonia decomposition reaction conditions to obtain ammonia decomposition reaction products, and returning the ammonia decomposition reaction products to step (2), with or without separation.

[0089] Preferably, in step (1), the molar ratio of ammonia to hexanediol is 18 to 50:1, preferably 22 to 38:1, and the molar ratio of hydrogen to hexanediol is 0.08 to 6:1, preferably 0.4 to 3:1. The molar ratios of ammonia, hydrogen, and hexanediol refer to the molar ratios in the mixture at the inlet of the ammoniation reactor.

[0090] Preferably, in step (1), the temperature of the ammonia reaction is 120°C to 210°C, preferably 130°C to 200°C. The pressure of the ammonia reaction is 7 MPaG to 17 MPaG, preferably 9 MPaG to 16 MPaG. The liquid volume space velocity of fresh hexanediol is 0.05 h -1 ~7h -1 Preferably 0.09h -1 ~3.9h -1 That is the case.

[0091] Preferably, the weight ratio of the hexamethyleneimine-containing stream returned to step (1) to fresh hexanediol is 0.1 to 13:1, preferably 0.3 to 10:1.

[0092] [Examples] The present invention will be described in detail below through examples. In the following examples, The composition of the product was analyzed by gas chromatography.

[0093] Yield of hexamethylenediamine = Molar amount of hexamethylenediamine ÷ Molar amount of freshly supplied hexanediol × 100%.

[0094] Preparation Example 1 Ammonia decomposition catalysts are prepared by a multi-step impregnation method: (1) Pseudoboehmite (manufactured by the aluminum sulfate process, specific surface area 310 m²) 2 94.2 g of (1.19 ml / g, pore volume 1.19 ml / g), 72.5 g of silica sol (JN-40), and 25.26 g of calcium nitrate tetrahydrate were weighed. This pseudo-boehmite was placed in a kneader, and the weighed silica sol and calcium nitrate tetrahydrate were added to 24.77 g of water to prepare a solution, which was then added to the kneader and thoroughly mixed with the pseudo-boehmite. Next, an aqueous solution prepared from 16.51 g of water, 4.71 g of nitric acid, and 2.83 g of phosphoric acid was added and thoroughly mixed. The mixture was then kneaded and extruded in a clover shape, dried at 120°C for 4 hours, and then calcined in a muffle oven at 900°C for 6 hours. After cooling, a support was obtained.

[0095] (2) 100.77 g of nickel sulfate hexahydrate (industrial grade, 98% purity), 5.69 g of lanthanum acetate monohydrate, and 5.96 g of indium nitrate pentahydrate were added to 134.78 mL of water to prepare an aqueous solution. This aqueous solution was loaded onto 73.25 g of the carrier obtained in (1) in two separate applications by equivolute impregnation, and after each impregnation, the carrier was dried at 120°C for 4 hours. After the two impregnations, the carrier was calcined at 390°C for 4 hours.

[0096] Example 1 (1) The raw materials, namely the solvent (cyclohexane), hexanediol, ammonia, and hydrogen, were supplied to a fixed-bed ammonia reactor supported with the catalyst of Example 14 of CN114433086A. The molar ratio of ammonia to hexanediol was 35:1, the molar ratio of hydrogen to hexanediol was 0.5:1, the molar ratio of solvent to hexanediol was 3.8:1, the ammonia reaction temperature was 166°C, the ammonia reaction pressure was 12 MPaG, and the liquid volume space velocity of fresh hexanediol was 0.1 h. -1 The product of the initial ammoniaization reaction (before returning the circulating flow to the fixed-bed ammonia reactor) contained: 5.76 wt% hexamethylenediamine, 1.13 wt% hexanediol, 4.91 wt% aminohexanol, 4.76 wt% hexamethyleneimine, 48.1 wt% ammonia, 31.59 wt% cyclohexane, 2.56 wt% water, and the remainder being heavy components. The molar yield of hexamethylenediamine in the initial ammoniaization reaction was 31.1%.

[0097] (2) The ammonia reaction product was subjected to gas-liquid separation to remove hydrogen and ammonia. The hydrogen was returned to the fixed-bed ammonia reactor in gas phase form via a compressor, and the liquid ammonia was pumped back into the ammonia reactor. The gas-liquid separation method involved: subjecting the reaction product to gas-liquid separation through four flash tanks at 12 MPaG, 5 MPaG, 2 MPaG, and 0.5 MPaG, condensing the gas phase at the top of the second and third flash tanks respectively, refluxing at a reflux ratio of 0.1, and heating the liquid phase before it entered the fourth flash tank, which was packed with 1 m of packing material. The gas phase obtained by flash evaporation was condensed with condensate water at 30°C to 45°C to obtain circulating ammonia (liquid phase) and gas phase (hydrogen), and the gas phase was compressed to obtain circulating hydrogen. The recycled hydrogen consisted mainly of 9.72 wt% hydrogen and the remainder ammonia; the recycled ammonia consisted mainly of 94.96 wt% ammonia, 4.12 wt% cyclohexane, 0.73 wt% water, 0.01 wt% hexamethylenediamine, and 0.15 wt% hexamethyleneimine.

[0098] The ammonia reaction product, from which ammonia and hydrogen had been removed, entered a first distillation column for vacuum distillation, yielding a stream containing hexamethyleneimine, water, and solvent (this stream contained: 80.11 wt% cyclohexane, 13.01 wt% hexamethyleneimine, and 5.79 wt% water) at the top of the first distillation column; the operating conditions of the first distillation column included: a bottom temperature of 179.9°C, a top temperature of 40.5°C, a reflux ratio of 1.5, a top operating pressure of -0.08 MPa, and 25 stages. The bottom flow from the first distillation column was sent to the second distillation column for separation, yielding a hexamethylenediamine product at the top (the hexamethylenediamine content in the product was 99.8 wt%) and a flow containing hexanediol, aminohexanol, and heavy components at the bottom (this flow contained 79.73 wt% aminohexanol, 18.35 wt% hexanediol, 0.2 wt% hexamethylenediamine, and the remainder being the heavy component C12 amine); the operating conditions of the second distillation column included a bottom temperature of 189.1°C, a top temperature of 83°C, a reflux ratio of 2.7, a top operating pressure of -0.09 MPa, and 24 stages. The bottom flow from the second distillation column was sent to a third distillation column for separation, obtaining a flow containing hexanediol and aminohexanol at the top of the third distillation column and heavy components at the bottom; the operating conditions of the third distillation column included a bottom temperature of 267.5°C, a top temperature of 83.7°C, a reflux ratio of 5.3, a top operating pressure of -0.09 MPa, and 38 stages.

[0099] (3) The stream containing hexamethyleneimine, water, and solvent obtained in step (2) was distilled to obtain a stream containing hexamethyleneimine (this stream contained 99.91 wt% hexamethyleneimine and 0.09 wt% hexamethylenediamine) and a stream containing solvent and water, with distillation conditions including a column bottom temperature of 94.3°C and a column top operating pressure of -0.08 MPa. The stream containing solvent and water was dehydrated using membrane separation to obtain a solvent stream (this stream contained 99.67 wt% cyclohexane and 0.32 wt% hexamethyleneimine) and wastewater (cyclohexane content was less than 100 ppmw), with membrane separation conditions including a membrane inlet temperature of 100°C and a membrane inlet pressure of 0.05 MPaG.

[0100] (4) The heavy components obtained at the bottom of the third distillation column in step (2) are uniformly mixed with the solvent (cyclohexane) and then sent to an ammonia decomposition reactor packed with an ammonia decomposition catalyst. Ammonia and hydrogen are simultaneously introduced into the ammonia decomposition reactor. The molar ratio of the heavy components, calculated as hydrogen:ammonia:dihexamethylenethriamine, is 1:40:1, the weight ratio of the solvent to the heavy components is 5:1, the ammonia decomposition reaction temperature is 186°C, the ammonia decomposition reaction pressure is 16 MPaG, and the liquid volume space velocity of the heavy components is 0.5 h. -1 The composition of the resulting ammonia decomposition reaction product was: 0.07 wt% hydrogen, 55.66 wt% ammonia, 7.84 wt% hexamethylenediamine, 6.01 wt% hexamethyleneimine, 21.92 wt% cyclohexane, and the remainder being heavy components. All of the ammonia decomposition reaction product was returned to step (2).

[0101] The ratio of the total weight of the hexamethyleneimine-containing stream and the aminohexanol-containing stream returned to process (1) to the weight of fresh hexanediol was 2.88. The weight ratio of the hexamethyleneimine-containing stream to the aminohexanol-containing stream returned to process (1) was 0.72:1.

[0102] The system was operated continuously until it reached a stable state, and the molar yield of hexamethylenediamine was 93.7%. There were no blockages in the system, and it was able to operate continuously and smoothly for a long period of time.

[0103] Furthermore, the temperature distribution inside the reactor containing the solvent was uniform with no hot spots, and the temperature deviation between multiple temperature measurement points distributed at the same floor height was less than 1.2°C.

[0104] Example 2 (1) The raw materials, namely the solvent (1,4-dioxane), hexanediol, ammonia, and hydrogen, were supplied to a fixed-bed ammonia reactor loaded with the catalyst of Example 6 of CN114433086A. The molar ratio of ammonia to hexanediol was 25:1, the molar ratio of hydrogen to hexanediol was 1:1, the molar ratio of solvent to hexanediol was 1.2:1, the ammonia reaction temperature was 190°C, the ammonia reaction pressure was 10 MPaG, and the liquid volume space velocity of fresh hexanediol was 0.6 h -1 The product of the initial ammoniaization reaction (before returning the circulating flow to the fixed-bed ammonia reactor) contained: 8.39 wt% hexamethylenediamine, 0.93 wt% hexanediol, 5.97 wt% aminohexanol, 6.67 wt% hexamethyleneimine, 34.83 wt% ammonia, 39.02 wt% 1,4-dioxane, 3.12 wt% water, and the remainder being heavy components. The molar yield of hexamethylenediamine in the initial ammoniaization reaction was 36.4%.

[0105] (2) The ammonia reaction product was subjected to gas-liquid separation to remove hydrogen and ammonia. The hydrogen was returned to the fixed-bed ammonia reactor in gas phase form via a compressor, and the liquid ammonia was returned to the ammonia reactor by a pump. The gas-liquid separation method included: subjecting the reaction product to three stages of gas-liquid separation at 10 MPaG, 2 MPaG, and 0.8 MPaG; providing a packing material section at the top of the second-stage flash tank, condensing and refluxing the gas phase at the top of the tank at a reflux ratio of 0.3; and providing 1 m of packing material and a heater at the bottom of the tank in the third-stage flash tank. The gas phase obtained by flash evaporation was condensed with condensed water at 30°C to 45°C to obtain circulating ammonia (liquid phase) and gas phase (hydrogen), and the gas phase was compressed to obtain circulating hydrogen. The recycled hydrogen consisted mainly of 10.19 wt% hydrogen and the remainder ammonia; the recycled ammonia consisted mainly of 93 wt% ammonia, 5.79 wt% 1,4-dioxane, 0.91 wt% water, 0.01 wt% hexamethylenediamine, and 0.21 wt% hexamethyleneimine.

[0106] The ammonia reaction product, from which ammonia and hydrogen had been removed, entered a first distillation column for vacuum distillation, yielding a stream containing hexamethyleneimine, water, and solvent (this stream contained: 79.93 wt% 1,4-dioxane, 14.40 wt% hexamethyleneimine, and 5.86 wt% water) at the top of the first distillation column; the operating conditions of the first distillation column included: a bottom temperature of 176.9°C, a top temperature of 44.2°C, a reflux ratio of 2.6, a top operating pressure of -0.08 MPa, and 19 stages. The bottom flow from the first distillation column was sent to the second distillation column for separation, yielding a hexamethylenediamine product at the top (with a hexamethylenediamine content of 99.9 wt%) and a flow containing hexanediol, aminohexanol, and heavy components at the bottom (this flow contained 85.36 wt% aminohexanol, 13.33 wt% hexanediol, 0.25 wt% hexamethylenediamine, and the remainder heavy component C12 amine); the operating conditions for the second distillation column included a bottom temperature of 188.3°C, a top temperature of 84.3°C, a reflux ratio of 1.9, a top operating pressure of -0.09 MPa, and 33 stages. The bottom flow from the second distillation column was sent to a third distillation column for separation, obtaining a flow containing hexanediol and aminohexanol at the top of the third distillation column and heavy components at the bottom; the operating conditions of the third distillation column included a bottom temperature of 270.5°C, a top temperature of 83.6°C, a reflux ratio of 5, a top operating pressure of -0.09 MPa, and 39 stages.

[0107] (3) The stream containing hexamethyleneimine, water, and solvent obtained in step (2) was distilled to obtain a stream containing hexamethyleneimine (this stream contained 99.94 wt% hexamethyleneimine and 0.06 wt% hexamethylenediamine) and a stream containing solvent and water, the distillation conditions being a column bottom temperature of 207.3°C and a column top operating pressure of 0.5 MPa. Pressure swing distillation was used to dehydrate the streams containing the solvent and water, yielding a solvent stream (which contained 99.64 wt% 1,4-dioxane and 0.36 wt% hexamethyleneimine) and wastewater (99.95 wt% water and 0.05 wt% 1,4-dioxane). The pressure swing distillation conditions included a top pressure of 1 MPaG and a bottom temperature of 197.2°C in the high-pressure column, and a top pressure of 0 MPaG and a bottom temperature of 96.3°C in the low-pressure column.

[0108] (4) The heavy component obtained at the bottom of the third distillation column in step (2) is uniformly mixed with the solvent (1,4-dioxane) and then sent to an ammonia decomposition reactor packed with an ammonia decomposition catalyst. Ammonia and hydrogen are simultaneously introduced into the ammonia decomposition reactor. The molar ratio of the heavy component, calculated as hydrogen:ammonia:dihexamethylenethriamine, is 3:50:1, the weight ratio of the solvent to the heavy component is 11:1, the ammonia decomposition reaction temperature is 203°C, the ammonia decomposition reaction pressure is 15 MPaG, and the liquid volume space velocity of the heavy component is 0.8 h. -1The composition of the ammonia decomposition reaction product obtained was: hydrogen 4.75 wt%, ammonia 71.74 wt%, hexamethylenediamine 2.60 wt%, hexamethyleneimine 3.52 wt%, 1,4-dioxane 15.26 wt%, and the remainder being heavy components. The ammonia decomposition reaction product was reduced to 10 MPag and subjected to gas-liquid separation by flash evaporation at this pressure to obtain a stream containing hydrogen and ammonia, as well as a residual liquid phase. Subsequently, the residual liquid phase was subjected to distillation in a crude distillation column to obtain a mixture containing hexamethylenediamine and hexamethyleneimine along with the heavy components. In the crude distillation column, the top pressure was -0.07 MPag, the top temperature was 180°C, the bottom temperature was 480°C, and the reflux ratio was 20. The mixture containing hexamethylenediamine and hexamethyleneimine at the top of the crude separation column was returned to process (2), and the bottom flow was discharged as waste liquid.

[0109] The ratio of the total weight of the hexamethyleneimine-containing stream and the aminohexanol-containing stream returned to process (1) to the weight of fresh hexanediol was 2.95. The weight ratio of the hexamethyleneimine-containing stream to the aminohexanol-containing stream returned to process (1) was 0.97:1.

[0110] The system was operated continuously until it reached a stable state, and the molar yield of hexamethylenediamine was 94.8%. There were no blockages in the system, and it was able to operate continuously and smoothly for a long period of time.

[0111] Furthermore, the temperature distribution inside the reactor containing the solvent was uniform with no hot spots, and the temperature deviation between multiple temperature measurement points distributed at the same floor height was less than 1.5°C.

[0112] Example 3 (1) Ammonia, hydrogen, and hexanediol are supplied to a fixed-bed ammonia reactor packed with the catalyst of Example 2 of CN114433113A, with a molar ratio of ammonia to hexanediol of 35:1, a molar ratio of hydrogen to hexanediol of 2:1, an ammonia reaction temperature of 150°C, a reaction pressure of 12 MPa, and a liquid-phase volume space velocity of hexanediol of 1 h -1 That was the case.

[0113] (2) The ammonia reaction product was separated into gas and liquid to remove hydrogen and ammonia. The hydrogen was returned to the fixed-bed ammonia reactor in gas phase form via a compressor, and the liquid ammonia was pumped back into the ammonia reactor. The gas-liquid separation method involved passing the ammonia reaction product sequentially through three flash tanks for three-stage vacuum flash evaporation to recover hydrogen, setting the pressures from the first to the third flash tanks to 7 MPa, 5 MPa, and 2 MPa respectively, cooling the gas phase at the top of each of the three flash tanks to 45°C, then subjecting them to further gas-liquid separation, returning the resulting liquid phase to each vacuum flash tank, pressurizing the gas phase to the ammonia reaction pressure, and then returning it to the ammonia reactor. The liquid phase at the bottom of the third vacuum flash tank entered a deaminolysis column from the top, which had 11 stages, and the operating pressure at the top of the column was 2 MPa. To conserve energy and reduce consumption, no condenser was installed at the top of the deamination distillation column; the top flow of the deamination distillation column was pressurized to the ammonia reaction pressure and then sent back to the inlet of the ammonia reactor, while the bottom flow was used for subsequent purification.

[0114] The ammonia reaction product, from which ammonia and hydrogen had been removed, was cleaved and separated according to different boiling points, with hexamethylenediamine as the key component, and sequentially subjected to a first separation to obtain a stream containing hexamethyleneimine and a residual stream. Subsequently, the residual stream was subjected to a second separation to obtain a stream containing the hexamethylenediamine product and aminohexanol, C12 amine, and heavy components. Then, the stream containing aminohexanol, C12 amine, and heavy components was subjected to a third separation to obtain a stream containing aminohexanol, a stream containing C12 amine, and heavy components. The stream containing aminohexanol and the stream containing hexamethyleneimine were mixed in a weight ratio of 1:1.25 and returned to step (1) as a circulating stream, and the heavy components were removed by distillation. Here, the first separation was carried out in the first distillation column, with operating conditions including a bottom temperature of 187°C, a top temperature of 50°C, a reflux ratio of 2.1, 18 theoretical stages, and a top operating pressure of -0.07 MPa; the second separation was carried out in the second distillation column, with operating conditions including a bottom temperature of 195°C, a top temperature of 131°C, a reflux ratio of 5, 19 theoretical stages, and a top operating pressure of -0.08 MPa; and the third separation was carried out in the third distillation column, with operating conditions including a bottom temperature of 338°C, a top temperature of 87°C, a reflux ratio of 5, 55 theoretical stages, and a top operating pressure of -0.09 MPa.

[0115] (3) The heavy components obtained from the bottom of the third distillation column in step (2) are sent to an ammonia decomposition reactor packed with an ammonia decomposition catalyst, and ammonia and hydrogen are simultaneously introduced into the ammonia decomposition reactor. The molar ratio of the heavy components calculated as hydrogen:ammonia:dihexamethylenetriamine is 5:100:1, the ammonia decomposition reaction temperature is 170°C, the ammonia decomposition reaction pressure is 12 MPag, and the liquid space velocity of the flow containing C12 amine is 0.5 h. -1 The ammonia decomposition product was returned to step (2).

[0116] Table 1 shows the weight composition of each flow when the reaction was proceeding stably. The molar yield of hexamethylenediamine was 90.69%.

[0117] [Table 1]

[0118] Note: 11: Composition of the flow at the ammonia reactor inlet; 12: Ammonia reaction products; 13: Circulating hydrogen and ammonia; 14: Circulating flow; 15: Hexamethylenediamine products; 16: Heavy components; 17: Flow containing C12 amines; 19: Light components; " / " in the table means that the content was less than 500 ppm or 0.

[0119] Comparative Example 1 The procedure followed the method of Example 1, except that the obtained heavy components were not subjected to ammonia decomposition. When the reaction proceeded stably, the molar yield of hexamethylenediamine was 86.5%.

[0120] Comparative Example 2 The procedure followed that of Example 2, except that the obtained heavy components were not subjected to ammonia decomposition. When the reaction proceeded stably, the molar yield of hexamethylenediamine was 87.7%.

[0121] Comparative Example 3 The procedure followed the method of Example 3, except that the obtained heavy components were not subjected to ammonia decomposition. When the reaction proceeded stably, the molar yield of hexamethylenediamine was 83.91%.

[0122] Preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including various combinations of technical features in any other preferred embodiment. These simple modifications and combinations should also be considered as being disclosed by the present invention and are within the scope of protection of the present invention.

Claims

1. A method for preparing hexamethylenediamine, comprising the following steps: (1) A step of subjecting hexanediol and ammonia to an ammonia reaction under ammonia reaction conditions, optionally in the presence of a first solvent, to obtain an ammonia reaction product; (2) A step of separating the ammonia reaction product from step (1) to obtain the hexamethylenediamine product and heavy components; and (3) A method comprising the steps of (3) subjecting the heavy component to ammonia decomposition under ammonia decomposition reaction conditions to obtain an ammonia decomposition reaction product, and returning the ammonia decomposition reaction product to step (2).

2. The method according to claim 1, wherein, in the ammoniation reaction, the molar ratio of ammonia to hexanediol is 10 to 90:1, preferably 15 to 70:1; and the ammoniation reaction is carried out in the presence of hydrogen, and the molar ratio of hydrogen to hexanediol is 0.05 to 25:1, preferably 0.1 to 10:

1.

3. The temperature of the ammonia reaction is 100°C to 300°C, preferably 120°C to 250°C; the pressure of the ammonia reaction is 4 MPaG to 25 MPaG, preferably 6 MPaG to 20 MPaG; and the liquid volume space velocity of fresh hexanediol is 0.01 h. －１ ~15h －１ Preferably 0.03h －１ ~8h －１ The method according to claim 1 or 2.

4. Step (2) is further divided into the following steps: The ammonia reaction product is separated to obtain a stream containing hexamethyleneimine and water, optionally the stream containing hexamethyleneimine and water is separated to obtain a stream containing hexamethyleneimine, and at least a portion of the stream containing hexamethyleneimine is returned to step (1); preferably the weight ratio of the stream containing hexamethyleneimine returned to step (1) to fresh hexanediol is 0.1 to 26:1, more preferably 0.3 to 24:1; and / or The method according to any one of claims 1 to 3, comprising the steps of: separating the ammonia reaction product to obtain a stream containing aminohexanol; optionally, returning at least a portion of the stream containing aminohexanol to step (1); preferably, the weight ratio of the stream containing aminohexanol returned to step (1) to fresh hexanediol is 0.1 to 26:1, more preferably 0.3 to 24:

1.

5. Step (2) is further divided into the following steps: The steps include: separating the ammonia reaction product to obtain a stream containing hexamethyleneimine and water; separating the stream containing hexamethyleneimine and water to obtain a stream containing hexamethyleneimine; and returning at least a portion of the stream containing hexamethyleneimine to step (1); and The process includes separating the ammonia reaction product to obtain a stream containing aminohexanol, and returning at least a portion of the aminohexanol-containing stream to step (1); Preferably, the weight ratio of the stream containing hexamethyleneimine to the stream containing aminohexanol returned to step (1) is 0.1 to 5:1; Preferably, the method according to any one of claims 1 to 3, wherein the ratio of the total weight of the stream containing hexamethyleneimine and the stream containing aminohexanol returned to step (1) to the weight of fresh hexanediol is 0.1 to 30:1, preferably 0.3 to 25:

1.

6. An approach for separating the stream containing hexamethyleneimine and water includes at least one of atmospheric distillation, vacuum distillation, pressure swing distillation, azeotropic distillation, membrane separation, and centrifugation; Preferably, the azeotropic agent used in the azeotropic distillation is at least one of cyclohexane, n-hexane, trimethylpentane, 1-methyl-4-isopropylbenzene, 1,4-dioxane, phenol, cresol, dibutyl ether, diamyl ether, and diisoamyl ether, according to claim 4 or 5.

7. An approach to separate the ammonia reaction product is to subject the ammonia reaction product to a first separation to obtain a stream containing hexamethyleneimine and water, then to a second separation to obtain a stream containing the hexamethylenediamine product, as well as aminohexanol and heavy components, and then to a third separation to obtain a stream containing aminohexanol and the heavy components; Preferably, the method according to any one of claims 1 to 6, wherein the first separation, the second separation, and the third separation each independently include at least one of distillation, membrane separation, and pressure swing adsorption.

8. Before the ammonia reaction product is separated, it is first pre-separated to obtain circulating hydrogen and ammonia, and the circulating hydrogen and ammonia are returned to the ammonia reaction; Preferably, the method according to any one of claims 1 to 7, wherein the pretreatment comprises at least one of flash evaporation, distillation, and stripping.

9. The method according to any one of claims 1 to 8, wherein step (3) further comprises dissolving the heavy component in a second solvent before the ammonia decomposition reaction, and then carrying out the ammonia decomposition; the second solvent is at least one of tetrahydrofuran, 1,4-dioxane, n-hexane, cyclohexane, and tert-butanol; and the weight ratio of the second solvent to the heavy component is 1 to 20:

1.

10. The method according to any one of claims 1 to 9, wherein in step (3), the ammonia decomposition is carried out in the presence of hydrogen and ammonia, the molar ratio of hydrogen:ammonia:heavy component is 0.1 to 20:10 to 150:1, and the heavy component is calculated as dihexamethylenetriamine.

11. The conditions for the ammonia decomposition reaction are: a reaction temperature of 120°C to 300°C, preferably 150°C to 270°C; a reaction pressure of 9 MPaG to 25 MPaG, preferably 10 MPaG to 22 MPaG; and 0.01 h. －１ ~8h －１ Preferably 0.05h －１ ~5h －１ The method according to any one of claims 1 to 10, comprising the liquid volume space velocity of the heavy component.

12. Step (1) includes: subjecting hexanediol and ammonia to an ammonia reaction in a first solvent under the ammonia reaction conditions to obtain the ammonia reaction product; The method according to any one of claims 1 to 11, wherein step (2) includes: separating the ammonia reaction product from step (1) to obtain a stream containing hexamethyleneimine, the first solvent and water, a stream containing the hexamethylenediamine product and aminohexanol, and the heavy component, returning at least a portion of the stream containing aminohexanol to step (1), separating the stream containing hexamethyleneimine, the first solvent and water to obtain a stream containing hexamethyleneimine and a stream of the first solvent, and returning at least a portion of the stream containing hexamethyleneimine and at least a portion of the stream of the first solvent to step (1).

13. The method according to claim 12, wherein, in the ammoniation reaction, the molar ratio of ammonia to hexanediol is 10 to 80:1, preferably 20 to 45:1; and the ammoniation reaction is carried out in the presence of hydrogen, wherein the molar ratio of hydrogen to hexanediol is 0.05 to 20:1, preferably 0.2 to 5:

1.

14. The temperature of the ammoniation reaction is 100°C to 250°C, preferably 130°C to 210°C; the pressure of the ammoniation reaction is 6 MPaG to 18 MPaG, preferably 8 MPaG to 16 MPaG; the liquid hourly space velocity of fresh hexanediol is 0.01 h －１ to 10 h －１ preferably 0.05 h －１ to 4 h －１ The method according to claim 12 or 13, wherein the method is as described above.

15. The first solvent is at least one of tetrahydrofuran, 1,4-dioxane, n-hexane, cyclohexane, and tert-butanol; and / or The method according to any one of claims 12 to 14, wherein the molar ratio of the first solvent to hexanediol is 0.1 to 10:

1.

16. The method according to any one of claims 12 to 15, wherein step (2) is: distilling the stream containing hexamethyleneimine, a first solvent, and water in a distillation column to obtain a stream containing hexamethyleneimine at the bottom of the column, and subjecting the stream at the top of the column to membrane separation or pressure swing distillation to obtain a stream of solvent and wastewater.

17. Step (1) includes: subjecting hexanediol and ammonia to the ammonia reaction under the ammonia reaction conditions, in the absence of the first solvent, to obtain the ammonia reaction product; Preferably, the method according to any one of claims 1 to 11, wherein the weight ratio of the flow containing hexamethyleneimine returned to step (1) to fresh hexanediol is 0.1 to 13:1, preferably 0.3 to 10:

1.

18. The method according to claim 17, wherein in step (1), the molar ratio of ammonia to hexanediol is 18 to 50:1, preferably 22 to 38:1, and the molar ratio of hydrogen to hexanediol is 0.08 to 6:1, preferably 0.4 to 3:

1.

19. The temperature of the ammonia reaction is 120°C to 210°C, preferably 130°C to 200°C; the pressure of the ammonia reaction is 7 MPaG to 17 MPaG, preferably 8 MPaG to 15 MPaG; and the liquid volume space velocity of fresh hexanediol is 0.05 h. －１ ~7h －１ Preferably 0.09h －１ ~3.9h －１ The method according to claim 17 or 18.

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