A method for preparing hexamethylenediamine from caprolactam

Abstract

The present disclosure relates to a method for preparing hexamethylenediamine from caprolactam, comprising the following steps: contacting caprolactam and ammonia with a first catalyst under catalytic amination reaction conditions to carry out an amination-dehydration reaction to obtain a first product containing 6-aminocapronitrile; and contacting the first product with hydrogen and a second catalyst under catalytic hydrogenation reaction conditions to carry out a hydrogenation reaction to obtain a second product containing hexamethylenediamine; the first catalyst comprising, on a dry basis and based on the total weight of the first catalyst, 5-95 weight percent of a titanium-containing support, 2-30 weight percent of a vanadium oxide, 0.5-10 weight percent of phosphorus pentoxide, 1-20 weight percent of a metal M oxide, and / or 0-5 weight percent of an inorganic oxide; the titanium-containing support comprises TiO2 and a titanium-containing molecular sieve, and the inorganic oxide comprises one or both of Al2O3 and SiO2.

Description

Technical Field

[0001] The present disclosure relates to the technical field of hexamethylenediamine preparation, and in particular, to a method for preparing hexamethylenediamine from caprolactam. Background Art

[0002] Hexamethylenediamine is an important chemical raw material commonly used to synthesize important industrial products such as nylon 66, nylon 610, and HDI. my country lacks production facilities for adiponitrile, the raw material for the synthesis of hexamethylenediamine, and relies entirely on imports. Therefore, developing new synthesis methods is crucial.

[0003] There are relatively few reports on the synthesis of hexamethylenediamine from caprolactam, the earliest being reported in US Patents 2,234,566 and 2,181,140. US Patent 2,234,566 reported the synthesis of 6-aminocapronitrile from caprolactam at a reaction temperature of 360°C and an ammonia / caprolactam molar ratio of 6 using silica gel-supported copper as a dehydration catalyst. Unreacted caprolactam was separated by distillation, and the aminocapronitrile was subsequently catalytically hydrogenated over a nickel or cobalt catalyst to hexamethylenediamine. The caprolactam conversion was 21.7%, and the 6-aminocapronitrile yield was 25%. The patent also did not address the hexamethylenediamine yield. US Patent 3,855,267 reported the use of a mixture of ammonia and caprolactam over an aluminum phosphate catalyst, achieving a 6-aminocapronitrile selectivity of 87% at an ammonia / caprolactam molar ratio of 75 to 100. Both of these methods for preparing 6-aminocapronitrile suffer from low catalyst activity and high energy consumption.

[0004] Chinese invention patent CN107739318A reports a method and apparatus for preparing 6-aminocapronitrile from caprolactam using a liquid-phase process. This method uses phosphoric acid or a phosphate as a catalyst, and while the reaction temperature is around 280°C, the yield is low, with an analysis of the yield in examples showing only about 50%. This method suffers from drawbacks such as complex separation of the catalyst and solvent, high energy consumption, and low caprolactam conversion. The method for synthesizing 6-aminocapronitrile from caprolactam reported in Chinese invention patent CN107602416A is similar to the method reported in US Pat. However, the reported method for preparing 6-aminocapronitrile from caprolactam using a vapor-phase process has a reaction temperature of around 350°C, and the contact time between caprolactam and ammonia is less than 1 second, making the process difficult to control.

[0005] In the reaction process for preparing 6-aminocapronitrile from caprolactam, caprolactam and ammonia first undergo ammonia ring-opening reaction, followed by dehydration to produce 6-aminocapronitrile. Currently reported gas-phase systems operate at high temperatures and high ammonia / caprolactam molar ratios. Ring-opening and dehydration reactions occur simultaneously on the catalyst surface, producing not only 6-aminocapronitrile but also cracking and deamination products and polyamide oligomers. This results in low caprolactam conversion and 6-aminocapronitrile selectivity.

[0006] Therefore, although the technology of preparing 6-aminocapronitrile by amination of caprolactam was studied early, the catalysts used all had problems such as low activity and low product yield. Summary of the Invention

[0007] The purpose of the present disclosure is to provide a method for preparing hexamethylenediamine from caprolactam, which can improve the caprolactam conversion rate and 6-aminocapronitrile selectivity and increase the hexamethylenediamine yield.

[0008] In order to achieve the above object, the present disclosure provides a method for preparing hexamethylenediamine from caprolactam, the method comprising the following steps:

[0009] S1. Under catalytic amination reaction conditions, caprolactam, ammonia and a first catalyst are contacted to perform an amination-dehydration reaction to obtain a first product containing 6-aminocapronitrile;

[0010] S2. Contacting the first product, hydrogen, and a second catalyst under catalytic hydrogenation reaction conditions to perform a hydrogenation reaction to obtain a second product containing hexamethylenediamine;

[0011] Wherein, on a dry basis and based on the total weight of the first catalyst, the first catalyst comprises 5-95 wt% of a titanium-containing carrier, 2-30 wt% of vanadium oxide, 0.5-10 wt% of phosphorus pentoxide, 1-20 wt% of a metal M oxide and / or 0-5 wt% of an inorganic oxide; wherein, the titanium-containing carrier comprises TiO2 and a titanium-containing molecular sieve, the metal M is selected from one or more of VB elements, VIB elements, VIII group elements and lanthanum elements, and the inorganic oxide comprises one or both of Al2O3 and SiO2.

[0012] Optionally, in step S1, the catalytic amination reaction conditions include: reaction temperature of 120-700°C, a molar ratio of ammonia to caprolactam of (0.1-100):1, ammonia partial pressure of 0.1-5.0 MPa, and a caprolactam weight hourly space velocity of 0.1-100 h -1 Preferably, the catalytic amination reaction conditions include: reaction temperature of 200-450 ° C, a molar ratio of ammonia to caprolactam of (1-10): 1, ammonia partial pressure of 0.2-3.0 MPa, and a caprolactam weight hourly space velocity of 0.5-20h -1 ; Optionally, the amination-dehydration reaction is carried out in a fixed bed reactor.

[0013] Optionally, in step S1, on a dry basis and based on the total weight of the first catalyst, the first catalyst comprises 30-90 wt % of a titanium-containing support, 4-15 wt % of a vanadium oxide, 1-5 wt % of phosphorus pentoxide, 2-10 wt % of a metal M oxide and / or 0.1-2 wt % of an inorganic oxide.

[0014] Optionally, on a dry basis, the weight ratio of TiO2 and the titanium-containing molecular sieve in the titanium-containing carrier is 1:(0.01-10), preferably 1:(0.1-5); the titanium-containing molecular sieve includes a titanium silicon molecular sieve; the titanium silicon molecular sieve is selected from one or more of HTS molecular sieve, TS-1 molecular sieve, TS-2 molecular sieve and TS-48 molecular sieve; optionally, the metal M is selected from one or more of tungsten, molybdenum, chromium, zinc, manganese, lanthanum, zirconium and iron; preferably, it is selected from one or more of tungsten, molybdenum and chromium, and further preferably, it is selected from one or two of molybdenum and tungsten.

[0015] Optionally, the BET specific surface area of the first catalyst is 50-300m 2 / g, the total pore volume is 0.1-0.4mL / g, and the micropore volume is 0.05-0.2mL / g; optionally, the shape of the first catalyst is selected from one or more of sphere, strip, cylinder, ring, clover, four-leaf, honeycomb and butterfly.

[0016] Optionally, the first catalyst is prepared by a preparation method comprising the following steps: a. contacting a vanadium source, water and an acid to perform an oxidation-reduction reaction; adding a metal M source, a phosphorus source and a titanium-containing carrier to the reaction product to obtain a mixture; performing a first drying treatment on the mixture to obtain an intermediate solid product; b. sequentially performing a molding treatment, a second drying treatment and a calcination treatment on the intermediate solid product.

[0017] Optionally, in step a, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is (0.5-2.0): (0.05-0.2): (0.05-0.5): (0.02-0.5): (0.01-1): 1; preferably (0.8-1.6): (0.05-0.1): (0.1-0.3): (0.04-0.3): (0.02-0.6): 1.

[0018] Optionally, the vanadium source is selected from one or more of ammonium metavanadate, sodium metavanadate and vanadium pentoxide; the acid is selected from one or more of oxalic acid, citric acid and nitric acid; the metal M in the metal M source is selected from one or more of tungsten, molybdenum, chromium, zinc, manganese, lanthanum and iron; the metal M source is selected from one or more of nitrates, phosphates and chlorides of metal M; preferably, it is selected from one or more of ammonium molybdate tetrahydrate, sodium tungstate, chromium nitrate and lanthanum nitrate; the phosphorus source is selected from one or more of ammonium dihydrogen phosphate, sodium hypophosphite, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

[0019] Optionally, step a includes: dissolving the vanadium source in water, then adding the acid to the vanadium source solution to carry out the oxidation reaction to obtain an oxidation reaction product; adding the metal M source and the phosphorus source to the oxidation reaction product, performing a first mixing to obtain a first mixture, optionally, the temperature of the first mixing is 50-100°C, and the time is 60-300min; adding the titanium-containing carrier to the first mixture, performing a second mixing to obtain a second mixture, optionally, the temperature of the second mixing is 30-80°C, and the time is 30-300min; subjecting the second mixture to the first drying treatment, and grinding the resulting product to obtain the intermediate solid product; optionally, the temperature of the first drying treatment is 80-150°C.

[0020] Optionally, the molding process in step b is extrusion molding; step b also includes: extruding and mixing the intermediate solid product with a pore-expanding agent and an auxiliary agent, and then sequentially performing the molding process, a second drying process, and a calcination process; or the molding process in step b is ball molding, and step b also includes: mixing the intermediate solid product with an inorganic oxide source, and then sequentially performing the molding process, a second drying process, and a calcination process.

[0021] Optionally, the amount of the pore expander added is 0.5-10 wt%, preferably 1-5 wt%, calculated on a dry basis and based on the added weight of the titanium-containing carrier; the amount of the extrusion aid added is 0.5-4 wt%, preferably 0.5-2 wt%; the amount of the inorganic oxide source added is 0.1-5 wt%, preferably 0.1-2.0 wt%, calculated on a dry basis and based on the added weight of the titanium-containing carrier.

[0022] Optionally, in step b, the pore expanding agent is selected from one or more of sesbania powder, paraffin, stearic acid, glycerol, starch, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, polyacrylamine, cellulose methyl ether, cellulose, polymer alcohol and graphite; the extrusion aid is selected from one or more of organic acids, inorganic acids and inorganic bases, preferably, the extrusion aid is selected from one or more of oxalic acid, tartaric acid, citric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia water, sodium hydroxide and potassium hydroxide; the inorganic oxide source is added in the form of an inorganic oxide or an inorganic oxide precursor; the inorganic oxide includes one or both of Al2O3 and SiO2; the inorganic oxide precursor is selected from one or more of aluminum sol, silica sol and water glass.

[0023] Optionally, in step b, the conditions for the second drying treatment include: temperature of 80-200°C, preferably 100-150°C; time of 1-10h, preferably 2-4h; the conditions for the calcination include: calcination temperature of 200-900°C, preferably 500-800°C; calcination time of 0.5-10h, preferably 2-4h.

[0024] Optionally, in step S2, the catalytic hydrogenation reaction conditions include: reaction temperature of 100-400°C, reaction pressure of 0.5-20 MPa, molar ratio of hydrogen to 6-aminocapronitrile of 0.1-1000:1, weight hourly space velocity of liquid feed of 0.1-10h -1 Preferably, the catalytic hydrogenation reaction conditions include: reaction temperature of 150-350 ° C, reaction pressure of 1.0-5.0 MPa, molar ratio of hydrogen to 6-aminocapronitrile of 1-50:1, weight hourly space velocity of liquid feed of 0.5-5h -1 .

[0025] Optionally, in step S2, the catalytic hydrogenation reaction is carried out in a slurry bed reactor, and the second catalyst includes a Raney nickel hydrogenation catalyst; or the catalytic hydrogenation reaction is carried out in a fixed bed reactor, and the second catalyst is selected from a supported hydrogenation catalyst; the supported hydrogenation catalyst is selected from one or more of nickel-based, cobalt-based and palladium-based catalysts; optionally, the nickel-based catalyst includes 5-60 weight% of nickel, 0-40 weight% of cobalt and 40-90 weight% of a first carrier; the cobalt-based catalyst includes 5-60 weight% of cobalt and 40-95 weight% of a second carrier; the palladium-based catalyst includes 0.5-10 weight% of palladium and 90-99.5 weight% of a third carrier; wherein the first carrier and the second carrier are each independently selected from one or both of silicon oxide and aluminum oxide; the third carrier is selected from one or both of activated carbon and aluminum oxide.

[0026] Optionally, the method further includes: before step S2, performing a first separation and purification treatment on the first product to obtain a 6-aminocapronitrile-rich product; then subjecting the 6-aminocapronitrile-rich product to the catalytic hydrogenation reaction; and after step S2, performing a second separation and purification treatment on the second product.

[0027] Through the above technical solution, the present disclosure provides a method for preparing hexamethylenediamine from caprolactam. The method uses caprolactam as a raw material to prepare hexamethylenediamine through an amination-dehydration reaction and a hydrogenation reaction. In the amination-dehydration reaction, the caprolactam conversion rate and the 6-aminocapronitrile selectivity are high, and the catalyst has high catalytic stability under long-term amination reaction events. During the hydrogenation reaction, the hexamethylenediamine product yield is high. In addition, the reaction process of this method does not use the HCN raw material used in traditional processes, and the reaction process is environmentally friendly.

[0028] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0029] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0030] The present disclosure provides a method for preparing hexamethylenediamine from caprolactam, the method comprising the following steps:

[0031] S1. Under catalytic amination reaction conditions, caprolactam, ammonia and a first catalyst are contacted to perform an amination-dehydration reaction to obtain a first product containing 6-aminocapronitrile;

[0032] S2. Contacting the first product, hydrogen, and a second catalyst under catalytic hydrogenation reaction conditions to perform a hydrogenation reaction to obtain a second product containing hexamethylenediamine;

[0033] Wherein, on a dry basis and based on the total weight of the first catalyst, the first catalyst comprises 5-95 wt% of a titanium-containing carrier, 2-30 wt% of vanadium oxide, 0.5-10 wt% of phosphorus pentoxide, 1-20 wt% of a metal M oxide and / or 0-5 wt% of an inorganic oxide; wherein, the titanium-containing carrier comprises TiO2 and a titanium-containing molecular sieve, the metal M is selected from one or more of VB elements, VIB elements, VIII group elements and lanthanum elements, and the inorganic oxide comprises one or both of Al2O3 and SiO2.

[0034] The method provided by the present disclosure uses caprolactam as a raw material to prepare hexamethylenediamine through an amination-dehydration reaction and a hydrogenation reaction. In the amination-dehydration reaction, the caprolactam conversion rate and the selectivity of 6-aminocapronitrile are high, and the catalyst has high catalytic stability under long-term amination reaction events. During the hydrogenation reaction, the yield of the hexamethylenediamine product is high. In addition, the reaction process of this method does not use the HCN raw material used in traditional processes, and the reaction process is environmentally friendly.

[0035] In addition, the addition of an inorganic oxide to the first catalyst used in the present invention can increase the catalyst strength, thereby increasing the catalyst service life; the addition of a metal M oxide to the first catalyst can further increase the conversion rate of the first catalyst in the reaction of preparing 6-aminocapronitrile by amination of caprolactam and the selectivity of the target product 6-aminocapronitrile, thereby reducing the generation of by-products.

[0036] In a preferred embodiment, in step S1, the first catalyst comprises, on a dry basis and based on the total weight of the first catalyst, 30-90 wt.% of a titanium-containing support, 4-15 wt.% of a vanadium oxide, 1-5 wt.% of phosphorus pentoxide, 2-10 wt.% of a metal M oxide, and / or 0.1-2 wt.% of an inorganic oxide. When the contents of the components of the first catalyst meet the requirements of this embodiment, the conversion rate and target product selectivity of the first catalyst in the amination of caprolactam to produce 6-aminocapronitrile can be further improved.

[0037] In the present disclosure, the content of each component in the first catalyst is determined by X-ray fluorescence spectrometry. The content of the titanium-containing carrier in the catalyst of the present disclosure is calculated based on the total Ti element oxides obtained by XRF testing.

[0038] In one embodiment, the weight ratio of TiO2 to the titanium-containing molecular sieve in the titanium-containing carrier is 1:(0.01-10), preferably 1:(0.1-5), calculated on a dry basis. The weight ratio of titanium dioxide to the titanium-containing molecular sieve in the present disclosure is calculated based on the mass ratio of the two raw materials added during the preparation process.

[0039] According to the present disclosure, TiO2 is well known to those skilled in the art, and when used as a carrier of a catalytic material, rutile and anatase titanium dioxide can be used, preferably rutile.

[0040] According to the present disclosure, titanium-containing molecular sieves are well known to those skilled in the art, including titanium silicate molecular sieves; the titanium silicate molecular sieve is selected from one or more of HTS molecular sieves, TS-1, TS-2 and TS-48 molecular sieves.

[0041] In one embodiment, the metal M is selected from one or more of tungsten, molybdenum, chromium, zinc, manganese, lanthanum and iron; preferably, it is selected from one or more of tungsten, molybdenum and chromium, and more preferably, it is selected from one or both of molybdenum and tungsten.

[0042] In one embodiment, the BET specific surface area of the first catalyst is 50-300m 2 / g, preferably 50 to 100 m 2 / g; the total pore volume is 0.1-0.4mL / g, preferably 0.1-0.3mL / g; the micropore volume is 0.05-0.2mL / g, preferably 0.05-0.1mL / g.

[0043] In one embodiment, the first catalyst is a granular shaped catalyst, and the shape of the catalyst is selected from one or more of sphere, strip, cylinder, ring, clover, four-leaf, honeycomb and butterfly, preferably strip or small ball with a diameter of 0.5-5.0 mm.

[0044] The first catalyst in the present disclosure can be used in various reactors, such as a fixed bed reactor, a moving bed reactor, or a fluidized bed reactor.

[0045] In one embodiment, the first catalyst is prepared by a preparation method comprising the following steps:

[0046] a. contacting a vanadium source, water, and an acid to perform an oxidation-reduction reaction; adding a metal M source, a phosphorus source, and a titanium-containing support to the reaction product to obtain a mixture; and performing a first drying treatment on the mixture to obtain an intermediate solid product;

[0047] b. subjecting the intermediate solid product to a molding process, a second drying process, and a calcination process in sequence.

[0048] The present invention first performs an oxidation reaction on a vanadium source and an acid to obtain an oxidation product (for example, the vanadium source and oxalic acid are oxidized to obtain vanadium oxalate), and then the oxidation product is mixed with a metal M source, a phosphorus source and a titanium-containing carrier. After drying to remove moisture, the vanadium oxalate, the metal M source and the phosphorus source can be loaded on the titanium-containing carrier to obtain an intermediate solid product.

[0049] In one embodiment, in step a, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is (0.5-2.0): (0.05-0.2): (0.05-0.5): (0.02-0.5): (0.01-1): 1; preferably (0.8-1.6): (0.05-0.1): (0.1-0.3): (0.04-0.3): (0.02-0.6): 1.

[0050] In one embodiment, the vanadium source is selected from one or more of ammonium metavanadate, sodium metavanadate and vanadium pentoxide;

[0051] The acid is selected from one or more of oxalic acid, citric acid and nitric acid;

[0052] The metal M in the metal M source is selected from one or more of tungsten, molybdenum, chromium, zinc, manganese, lanthanum and iron; the metal M source is selected from one or more of nitrates, phosphates and chlorides of metal M; preferably one or more of ammonium molybdate tetrahydrate, sodium tungstate, chromium nitrate and lanthanum nitrate;

[0053] The phosphorus source is selected from one or more of ammonium dihydrogen phosphate, sodium hypophosphite, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

[0054] In a specific implementation, step a includes:

[0055] dissolving the vanadium source in water, then adding the acid to the vanadium source solution to carry out the oxidation reaction to obtain an oxidation reaction product;

[0056] Adding the metal M source and the phosphorus source to the oxidation reaction product, performing a first mixing to obtain a first mixture, optionally, the first mixing temperature is 50-100° C., and the time is 60-300 min;

[0057] Adding the titanium-containing support to the first mixture and performing a second mixing to obtain a second mixture, wherein the temperature of the second mixing is 30-80° C. and the time is 30-300 min;

[0058] The second mixture is subjected to the first drying treatment, and the resulting product is ground to obtain the intermediate solid product; optionally, the temperature of the first drying treatment is 80-150° C. Optionally, the product can be ground to a particle size of 30 μm or less, where the ground particle size is the maximum particle size among the ground particles.

[0059] In one embodiment, the molding process in step b is extrusion molding; step b further comprises: extruding and mixing the intermediate solid product with a pore-enlarging agent and an auxiliary agent, and then sequentially performing the molding process, the second drying process, and the calcination process.

[0060] In a preferred embodiment, the amount of the pore expander added is 0.5-10 wt%, preferably 1-5 wt%, based on the dry basis and the added weight of the titanium-containing carrier; the amount of the extrusion aid added is 0.5-4 wt%, preferably 0.5-2 wt%.

[0061] In a specific embodiment, the pore-enlarging agent is selected from one or more of sesbania powder, paraffin, stearic acid, glycerol, starch, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, polyacrylamine, cellulose methyl ether, cellulose, polyol and graphite;

[0062] The extrusion aid is selected from one or more of oxalic acid, tartaric acid, citric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, aqueous ammonia, sodium hydroxide, and potassium hydroxide. The present disclosure adds a pore-enlarging agent and an extrusion aid in step b to facilitate the molding process of the first catalyst and increase the pores of the first catalyst.

[0063] In another embodiment, the forming process in step b is ball forming, and step b further comprises: mixing the intermediate solid product with an inorganic oxide source, and then sequentially performing the forming process, the second drying process, and the calcination process.

[0064] According to the present disclosure, the inorganic oxide serves as a binder to bond the titanium-containing support and the vanadium oxide and metal M oxide powder particles together during extrusion, thereby improving the strength and life of the first catalyst.

[0065] In a preferred embodiment, the amount of the inorganic oxide source added is 0.1-5% by weight, preferably 0.1-2.0% by weight, calculated on a dry basis and based on the added weight of the titanium-containing carrier. The present disclosure adds an appropriate amount of inorganic oxide source to avoid the phenomenon that the first catalyst is difficult to shape due to insufficient addition of the inorganic oxide source, and even if it is barely shaped, it will break when leaving the molding machine; and avoid the disadvantage that the spherical product becomes soft and sticky due to excessive addition of the inorganic oxide source.

[0066] According to the present disclosure, the inorganic oxide in the first catalyst can be added in the form of an inorganic oxide or in the form of its precursor, wherein the inorganic oxide includes one or both of Al2O3 and SiO2; the inorganic oxide precursor is selected from one or more of aluminum sol, silica sol and water glass.

[0067] In the present disclosure, the inorganic oxide as an inert substance can withstand the corrosion of strong acid and strong base, so that the formed particles will not be crushed during the alkali solution extraction process.

[0068] In further embodiments, if silica sol is used as the binder, it can be either acidic or alkaline, commercially available, or prepared using any conventional technique. Other inorganic oxide precursors with binding properties known to those skilled in the art can also be added during the preparation of the first catalyst.

[0069] In one embodiment, in step b, the conditions of the second drying treatment include: a temperature of 80-200° C., preferably 100-150° C.; a time of 1-10 hours, preferably 2-4 hours;

[0070] The calcination conditions include: a calcination temperature of 200-900°C, preferably 500-800°C; and a calcination time of 0.5-10 hours, preferably 2-4 hours. According to the present disclosure, drying and calcining after extrusion molding can improve the strength of the first catalyst.

[0071] In one embodiment, in step S1, the catalytic amination reaction conditions include: reaction temperature of 120-700°C, a weight ratio of ammonia to caprolactam of (0.1-100):1, ammonia partial pressure of 0.1-5.0 MPa, and a caprolactam weight hourly space velocity of 1-100 h -1 .

[0072] In a preferred embodiment, in step S1, the catalytic amination reaction conditions include: reaction temperature of 200-450°C, a molar ratio of ammonia to caprolactam of (1-10):1, ammonia partial pressure of 0.2-3.0 MPa, and a caprolactam weight hourly space velocity of 0.5-20 h -1The preferred catalytic amination reaction conditions provided by the present disclosure can further improve the caprolactam conversion rate and 6-aminocapronitrile selectivity of the catalytic amination.

[0073] In one embodiment, in step S1, the amination-dehydration reaction is carried out in a fixed-bed reactor. In the present disclosure, a fixed-bed reactor can be used to carry out a continuous reaction.

[0074] In another specific embodiment, in step S1, the amination-dehydration reaction is carried out in a reactor. In the present disclosure, a reactor is used as a reactor to carry out a batch reaction.

[0075] According to the present disclosure, in the amination-dehydration reaction, a liquid phase or gas phase embodiment known in the art can be adopted.

[0076] In the present disclosure, after step S1 is completed and before step S2, the first product is subjected to a first separation and purification treatment to obtain a product rich in 6-aminocapronitrile; and then the product rich in 6-aminocapronitrile is subjected to the catalytic hydrogenation reaction.

[0077] In the present disclosure, the purity of 6-aminocapronitrile in the 6-aminocapronitrile-rich product obtained through the first separation and purification is greater than 90% by weight.

[0078] In one specific embodiment, the first separation and purification method is to perform flash separation and / or distillation separation on the first product; preferably, the obtained first product is subjected to vacuum distillation to purify pure 6-aminocapronitrile, wherein the operating conditions and process of the vacuum distillation are: the vacuum distillation tower bottom temperature is 150-160°C, the vacuum degree is 2-4 torr, when the tower top temperature is 20-40°C, ammonia and water are evaporated, and when the vacuum distillation tower top temperature is 130-140°C, 6-aminocapronitrile is evaporated.

[0079] In one embodiment, in step S2, the catalytic hydrogenation reaction conditions include: a reaction temperature of 100-400°C, a reaction pressure of 0.5-20 MPa, a molar ratio of hydrogen to 6-aminocapronitrile of 0.1-1000:1, a weight hourly space velocity of the liquid feed of 0.1-10h -1 .

[0080] In a preferred embodiment, the catalytic hydrogenation reaction conditions include: reaction temperature of 150-350 ° C, reaction pressure of 1.0-5.0 MPa, molar ratio of hydrogen to 6-aminocapronitrile of 1-50:1, weight hourly space velocity of liquid feed of 0.5-5h -1 .

[0081] In one embodiment, in step S2, the catalytic hydrogenation reaction can be carried out in a slurry bed reactor, and the second catalyst is selected from Raney nickel hydrogenation catalyst.

[0082] In another embodiment, the catalytic hydrogenation reaction can be carried out in a fixed bed reactor, and the second catalyst is selected from a supported hydrogenation catalyst; the supported hydrogenation catalyst is selected from one or more of nickel-based, cobalt-based and palladium-based catalysts.

[0083] In a specific embodiment, the nickel-based catalyst comprises 5-60 weight % of nickel, 0-40 weight % of cobalt and 40-90 weight % of a first carrier; the cobalt-based catalyst comprises 5-60 weight % of cobalt and 40-95 weight % of a second carrier; the palladium-based catalyst comprises 0.5-10 weight % of palladium and 90-99.5 weight % of a third carrier; wherein the first carrier and the second carrier are each independently selected from one or both of silicon oxide and aluminum oxide; and the third carrier is selected from one or both of activated carbon and aluminum oxide.

[0084] The second catalyst used in the hydrogenation reaction of the present disclosure may be a catalyst conventionally used in the art; or a catalyst prepared by a known method.

[0085] According to the present disclosure, the hydrogenation reaction in step S2 can also be performed in a batch reaction mode. The batch reaction generally uses a reactor as a reactor, 6-aminocapronitrile and the second catalyst are added to the reactor, hydrogen is introduced, and the reaction is carried out at a certain temperature and pressure. After the reaction is completed, the reaction product is discharged from the reactor, the product is separated, and the next batch of materials is added to the reactor for reaction.

[0086] According to the present disclosure, the hydrogenation reaction in step S2 can also be carried out in a continuous reaction mode. The continuous hydrogenation reaction can be carried out in a shell-and-tube reactor, where the second catalyst is fixed in the tubes and cooling water is passed through the shell side to remove the heat released by the reaction.

[0087] In one specific embodiment, the method further comprises: after step S2, performing a second separation and purification treatment on the second product; preferably, the purity of hexamethylenediamine in the second product after the second separation and purification treatment is 99% by weight or greater. The 6-aminocapronitrile hydrogenation reaction product mainly contains hexamethylenediamine, and may also contain a certain amount of unreacted 6-aminocapronitrile and a small amount of high-boiling substances. This mixture can be separated by distillation, preferably by distillation. The distillation separation can be performed intermittently or continuously. The second separation and purification in the present disclosure can adopt conventional process parameters in the art.

[0088] The following describes the specific embodiments of the present disclosure in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0089] In the following examples, unless otherwise specified, all reagents used are commercially available reagents.

[0090] In the following examples and comparative examples, unless otherwise specified, pressures are gauge pressures.

[0091] In the following examples and comparative examples, the BET specific surface area, total pore volume, and micropore volume of the catalysts were measured using a Micromeritics ASAP-2020 automatic adsorption apparatus. The specific surface area was calculated using the two-parameter BET equation, the pore distribution was calculated using the BJH method, and the micropore specific surface area and pore volume were calculated using the t method.

[0092] The contents of each component in the catalyst were determined by X-ray fluorescence spectrometer (XRF).

[0093] Preparation Example 1

[0094] Preparation of vanadyl oxalate: 40 g of ammonium metavanadate was dissolved in 500 g of water, then heated in a water bath at 80°C. 80 g of oxalic acid crystals were slowly added under stirring. The reaction was carried out at 80°C for 120 min until the color of the slurry changed from yellow to a clear purple solution.

[0095] Then, 80 g of ammonium molybdate tetrahydrate and 18 g of ammonium dihydrogen phosphate were added, and the mixture was heated on a water bath for 30 min to obtain a mixed solution containing vanadyl oxalate, ammonium molybdate and phosphoric acid.

[0096] The solution was stirred in a 70°C water bath. 500g of TiO2 (DuPont R900) and 50g of titanium silicalite (Hunan Jianchang, HTS3 molecular sieve) were added to the solution under continuous stirring. Stirring and aging were continued for 4 hours. The resulting product was dried in an oven at 110°C for 4 hours. The dried material was added to a grinder and ground for 30 minutes to obtain an intermediate solid product with a maximum particle size of less than 30 microns.

[0097] In the above steps, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is 0.909:0.073:0.145:0.145:0.027:1.

[0098] To the intermediate solid product, 15 g of sesbania powder (purchased from Lankao Plant Gum Factory) and 20 g of a 20 wt% aqueous nitric acid solution (4 g of nitric acid) were added and mixed thoroughly. On a dry basis and based on the added weight of the titanium-containing carrier, the amount of sesbania powder added was 2.7 wt%, and the amount of nitric acid added was 0.73 wt%. The catalyst strips with a diameter of 2.5 mm were then extruded through an extruder, dried at 120°C for 4 h, and then calcined at 750°C for 4 h to obtain a catalyst strip, designated as CAT-1.

[0099] After drying, the catalyst CAT-1 had a strength of 40 N / cm as measured by a strength tester.

[0100] The composition of catalyst CAT-1 is 83.3 wt.% TiO2, 4.7 wt.% V2O5, 9.9 wt.% MoO3, 1.7 wt.% P2O5 and 0.4 wt.% SiO2.

[0101] Preparation Comparative Example 1

[0102] The same method as in Preparation Example 1 was used, except that:

[0103] 10 g of ammonium metavanadate, 20 g of oxalic acid crystals, 10 g of ammonium molybdate tetrahydrate, and 2 g of ammonium dihydrogen phosphate were used; the remaining process was the same as in the preparation example. The obtained product was recorded as DCAT-1.

[0104] After the catalyst DCAT-1 was dried, its strength was measured using a strength tester and was found to be 30 N / cm.

[0105] The composition of catalyst DCAT-1 is 96.5 wt% TiO2, 1.4 wt% V2O5, 1.4 wt% MoO3, 0.2 wt% P2O5, and 0.4 wt% SiO2.

[0106] Preparation Comparative Example 2

[0107] The same method as in Preparation Example 1 was used, except that ammonium molybdate tetrahydrate was not added. The remaining steps were the same as in Preparation Example 1. The obtained product was designated as DCAT-2.

[0108] After the catalyst DCAT-2 was dried, its strength was measured using a strength tester and was found to be 25 N / cm.

[0109] The composition of catalyst DCAT-2 is 92.5 wt% TiO2, 5.3 wt% V2O5, 1.9 wt% P2O5, and 0.4 wt% SiO2.

[0110] Preparation Example 2

[0111] Preparation of vanadyl oxalate: 40 g of ammonium metavanadate was dissolved in 500 g of water, then heated in a water bath at 80°C. 110 g of oxalic acid crystals were slowly added with stirring. The reaction was carried out at 80°C for 120 min until the color of the slurry changed from yellow to a clear purple solution.

[0112] Then, 80 g of ammonium molybdate tetrahydrate and 18 g of ammonium dihydrogen phosphate were added, and heating was continued on a water bath for 30 min to obtain a mixed aqueous solution containing vanadyl oxalate, ammonium molybdate and phosphoric acid.

[0113] The solution was stirred at 70°C. 500g of TiO2 (DuPont R900) and 50g of titanium silicalite (HTS-3, manufactured by Hunan Jianchang) were added to the solution under continuous stirring. Stirring and aging were continued for 4 hours. The resulting product was dried in an oven at 110°C for 4 hours. The dried material was then added to a grinder and ground for 30 minutes to obtain an intermediate solid product (maximum particle size less than 30 microns).

[0114] In the above steps, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is 0.909:0.073:0.2:0.145:0.033:1.

[0115] Then, 20 g of aluminum sol (a product of Hunan Jianchang) was added and mixed thoroughly. The amount of aluminum sol added was 3.6 wt.% on a dry basis based on the added weight of the titanium-containing carrier. The catalyst was then rolled into pellets in a ball rolling machine. The pellets with a diameter of 2.0-3.0 mm were sieved out from the obtained pellets, dried at 120°C for 4 h, and then calcined at 550°C for 4 h to obtain a pellet catalyst, which was designated as CAT-2.

[0116] After drying, the catalyst CAT-2 had a strength of 60 N / cm as measured by a strength tester.

[0117] The composition of catalyst CAT-2 is 82.8 wt% TiO2, 4.7 wt% V2O5, 9.9 wt% MoO3, 1.7 wt% P2O5, 0.4 wt% SiO2 and 0.5 wt% Al2O3.

[0118] Preparation Example 3

[0119] The same method as in Preparation Example 1 was used, except that:

[0120] 10 g of ammonium metavanadate, 30 g of oxalic acid crystals, 60 g of ammonium molybdate tetrahydrate, and 18 g of ammonium dihydrogen phosphate were used; the remaining process was the same as in the preparation example. The obtained product was designated as CAT-3.

[0121] In this embodiment, the weight ratio of vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is 0.018:0.055:0.109:0.033:1.

[0122] After drying, the catalyst CAT-3 had a strength of 40 N / cm as measured by a strength tester.

[0123] Catalyst CAT-3 consists of 77.9 wt% TiO2, 2.4 wt% V2O5, 15.4 wt% MoO3, 3.5 wt% P2O5, and 0.8 wt% SiO2.

[0124] Preparation Example 4

[0125] Preparation of vanadyl oxalate: 40 g of ammonium metavanadate was dissolved in 500 g of water, then heated in a water bath at 80°C. 110 g of oxalic acid crystals were slowly added with stirring. The reaction was carried out at 80°C for 120 min until the color of the slurry changed from yellow to a clear purple solution.

[0126] Then, 25 g of lanthanum nitrate and 30 g of sodium hypophosphite were added, and heating was continued on a water bath for 30 min to obtain a mixed aqueous solution containing vanadyl oxalate, lanthanum nitrate and sodium hypophosphite.

[0127] The solution was stirred at 70°C. 500g of TiO2 (DuPont R900) and 50g of titanium silicalite (HTS-3, manufactured by Hunan Jianchang) were added to the solution under continuous stirring. Stirring and aging were continued for 4 hours. The resulting product was dried in an oven at 110°C for 4 hours. The dried material was then added to a grinder and ground for 30 minutes to obtain an intermediate solid product (maximum particle size less than 30 microns).

[0128] In the above steps, the weight ratio of vanadium source: acid: metal M source: phosphorus source: titanium-containing support is 0.073:0.2:0.045:0.055:1. Then, 20 g of aluminum sol (Hunan Jianchang product) is added and mixed thoroughly, with the amount of aluminum sol added being 3.6% by weight, based on the dry weight of the titanium-containing support. The catalyst is then rolled in a ball mill to form pellets. Pellets with a diameter of 2.0-3.0 mm are screened out, dried at 120°C for 4 hours, and then calcined at 550°C for 4 hours to obtain a pellet catalyst designated CAT-4.

[0129] After drying, the catalyst CAT-4 was tested using a strength tester to find that its strength was greater than 40N / particle.

[0130] Catalyst CAT-4 consists of 88.2 wt% TiO2, 5.0 wt% V2O5, 2.0 wt% La2O3, 3.9 wt% P2O5, 0.4 wt% SiO2 and 0.5 wt% Al2O3.

[0131] Preparation Example 5

[0132] The same method as Example 4 was used, except that 40 g of ammonium metavanadate was dissolved in 500 g of water; 110 g of oxalic acid crystals were added; and 30 g of lanthanum nitrate was added. The remaining preparation parameters were the same as in Example 4. The weight ratio of vanadium source: acid: metal M source: phosphorus source: titanium-containing support was 0.073:0.2:0.055:0.055:1. The resulting product was designated CAT-5.

[0133] After drying, the catalyst CAT-5 was tested using a strength tester to obtain a strength of 50 N / particle.

[0134] Catalyst CAT-5 consists of 87.8 wt% TiO2, 5.0 wt% V2O5, 2.4 wt% La2O3, 3.9 wt% P2O5, 0.4 wt% SiO2 and 0.5 wt% Al2O3.

[0135] The structural test data of the catalyst products obtained in the above examples and comparative examples are listed in Table 1 below.

[0136] Table 1

[0137] <![CDATA[BET specific surface area / m 2 / g]]> Total pore volume / mL / g Micropore volume / mL / g CAT-1 86 0.18 0.08 DCAT-1 59 0.16 0.06 DCAT-2 65 0.17 0.06 CAT-2 85 0.25 0.07 CAT-3 71 0.12 0.08 CAT-4 82 0.23 0.06 CAT-5 91 0.24 0.07

[0138] The following reaction examples are used to illustrate the performance of the catalyst prepared above in the ammonia dehydration of caprolactam to prepare 6-aminocapronitrile.

[0139] Reaction Example 1

[0140] 10 g of catalyst CAT-1 was loaded into Inert quartz sand was placed in the middle of a jacketed stainless steel reactor, with both ends filled. 10 g / h (0.088 mol / h) of caprolactam (CPL) and 7.5 g / h (0.44 mol / h) of hot ammonia (the molar ratio of CPL to ammonia was 1:5) were mixed thoroughly at 100°C. The caprolactam-ammonia mixture was contacted with the catalyst at a reaction temperature of 250°C and a CPL space velocity of 1.0 h. -1 , the ammonia partial pressure is 1 MPa. In this example, the caprolactam conversion rate and the 6-aminocapronitrile selectivity were measured and calculated at reaction times of 20 h and 200 h, respectively. Specific data are listed in Table 2. The amination reaction product was subjected to deamination and dehydration, and after vacuum distillation, 6-aminocapronitrile with a purity of 99.0% by weight was obtained.

[0141] Comparative Reaction Examples 1-2

[0142] The same amination-dehydration reaction as in Reaction Example 1 was used, except that the catalyst CAT-1 was replaced by DCAT-1 to DCAT-2, respectively.

[0143] Reaction Examples 2 to 9

[0144] The same amination dehydration reaction as in Reaction Example 1 was used. The specific reaction conditions and reaction results are listed in Table 2 below.

[0145]

[0146]

[0147] Table 2

[0148]

[0149]

[0150] According to Table 2 above, we can see that:

[0151] Compared with reaction comparative examples 1 to 2 using DCAT-1 and DCAT-2, reaction examples 1, 6 to 8 of the present disclosure use the first catalyst provided by the present disclosure to carry out the amination catalytic reaction. Under the same reaction conditions, reaction examples 1, 6 to 8 can obtain higher caprolactam conversion rates and 6-aminocapronitrile selectivity in the caprolactam amination reaction; and the caprolactam conversion rates and 6-aminocapronitrile selectivity after 200 hours of reaction are smaller than those after 20 hours of reaction, and the stability is higher.

[0152] Furthermore, by comparing Reaction Example 1 with Reaction Example 3, it can be seen that the catalyst CAT-1 used in Reaction Example 1 satisfies the following conditions during the preparation process: "In step a, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is (0.8-1.6): (0.05-0.1): (0.1-0.3): (0.04-0.3): (0.02-0.6): 1", and the composition of CAT-1 satisfies "30-90 wt% of titanium-containing carrier, 4-15 wt% of vanadium oxide, 1-5 wt% of phosphorus pentoxide, 2-10 wt% of metal M oxide and / or 0.1-2 wt% of inorganic oxide". Reaction Example 1 can obtain a higher caprolactam conversion rate and 6-aminocapronitrile selectivity in the caprolactam amination reaction.

[0153] Furthermore, by comparing Reaction Example 1 with Reaction Example 9, it can be seen that, under the same catalyst conditions, the amination catalytic conditions of Reaction Example 1 meet the "reaction temperature of 200-450° C., and the molar ratio of ammonia to caprolactam of (1-10):1", and Reaction Example 1 can obtain a higher caprolactam conversion rate and 6-aminocapronitrile selectivity in the caprolactam amination reaction.

[0154] Reaction Examples 10 to 15

[0155] This paper describes a method for synthesizing hexamethylenediamine by hydrogenation of 6-aminocapronitrile.

[0156] 20g of Ni-Co / Al2O3 hydrogenation catalyst was placed in the center of a 24×4×800mm stainless steel reactor, with inert quartz sand filling the ends. Hydrogen was introduced and reduced at 300°C and 1.0 MPa for 24 hours to reduce the temperature and pressure to the hydrogenation reaction temperature. 6-Aminocapronitrile, produced by the amination of caprolactam, was pumped into the reactor via a metering pump for reaction. After 20 hours of reaction, a product sample was collected, condensed, and analyzed by offline chromatography. The product composition was used to calculate the 6-aminocapronitrile conversion and hexamethylenediamine selectivity. Specific data are shown in Table 3.

[0157]

[0158]

[0159] Hexamethylenediamine yield = 6-aminocapronitrile conversion × hexamethylenediamine selectivity

[0160] The specific synthesis steps of the hydrogenation catalyst Ni-Co / Al2O3 (second catalyst) used include:

[0161] (1) Preparation of nickel nitrate (Ni(NO3)2), cobalt nitrate, and aluminum nitrate solutions: Add 285 mL of deionized water to a 1 L beaker, start stirring, heat to 50-60°C, add 97 g of nickel nitrate crystals, 136 g of cobalt nitrate, and 295 g of aluminum nitrate to a mixed solution with a concentration of approximately 30% by weight.

[0162] (2) Preparation of Sodium Carbonate (Na2CO3) Solution: To ensure complete precipitation of metal ions, add 1.05 times the amount of sodium carbonate as the precipitant. Add 1200 mL of deionized water to a 2 L beaker, stir, and heat to 50-60°C. Add 208 g of anhydrous sodium carbonate solid to prepare a sodium carbonate solution with a concentration of approximately 15% by weight.

[0163] The above-mentioned sodium carbonate aqueous solution and metal salt solution slurry were added to a 5L reactor for contact at a temperature of 80°C. After contact for 4 hours, a solid was obtained by filtration. The obtained solid was dried and then calcined in a muffle furnace at 500°C for 6 hours to obtain a calcined solid; the calcined solid was subjected to programmed temperature reduction, and then the reduced solid was first cooled to 60°C under an argon atmosphere at normal pressure, and then continued to be cooled to 40°C under an atmosphere of a mixture of argon and oxygen with an oxygen concentration of 5% by volume at normal pressure to obtain a Ni-Co / Al2O3 catalyst as a hydrogenation catalyst.

[0164] XRF analysis revealed that the composition of the hydrogenation catalyst was 35.0 wt% Co3O4, 25 wt% NiO, and 40 wt% Al2O3.

[0165] Reaction Example 16

[0166] Hexamethylenediamine was prepared using the reaction conditions of Reaction Example 15. The difference from Reaction Example 15 was that the hydrogenation catalyst was replaced with a palladium-based catalyst; the palladium-based catalyst was a Pd / Al2O3 catalyst. The preparation method was as follows:

[0167] (1) Support modification: Weigh 100 g of γ-Al2O3 particles (φ3 mm × 8 mm, Hunan Jianchang Petrochemical Co., Ltd., with a surface area of 150 m2) 2 / g, pore volume 0.4mL / g), and a saturated water absorption capacity of 70mL. Based on a P2O5 / Al2O3 mass ratio of 0.02, 3.25g of ammonium dihydrogen phosphate was weighed and added to the required 70mL of deionized water to prepare the corresponding ammonium phosphate solution. The solution was then mixed with the activated alumina and stirred thoroughly. The solution was then transferred to an oven and dried at 120°C for 4h. The dried sample was then calcined at 550°C for 8h to produce the desired support.

[0168] (2) Catalyst preparation: 100 mL of an aqueous solution with a palladium chloride concentration of 15 g / L was measured, and 75 g of the support obtained in step (1) was added to the palladium chloride solution. The support was immersed at room temperature for 12 h under stirring, and 12.5 mL of a 5% (weight) NaOH solution was added dropwise and kept at a constant temperature for 2-10 h to obtain a suspension. Hydrogen gas was introduced into the suspension at a flow rate of 30 ml / min at 30°C, and reduction activation was performed under stirring for 4 h. After filtration, it was washed with deionized water until the Cl - Concentration less than 10 -6 M, and then at 70 ° C and vacuum degree of 1.013×10 -3 ~1.013×10 -4 Pa for 4 h and stored under nitrogen protection to obtain the catalyst.

[0169] XRF analysis revealed that the composition of the palladium-based catalyst was 2.0 wt% Pd and 98.0 wt% Al2O3. The reaction results are listed in Table 3.

[0170] Table 3

[0171]

[0172] In the above hydrogenation reaction examples, the hydrogenation reaction conditions of Reaction Examples 11 to 13 and 15 and 16 meet the following conditions: "reaction temperature 150-350° C., reaction pressure 1.0-5.0 MPa, and a molar ratio of hydrogen to 6-aminocapronitrile of 1-50:1". Compared with Reaction Examples 10 and 14, the 6-aminocapronitrile conversion rate, hexamethylenediamine selectivity and hexamethylenediamine yield of the hydrogenation reactions of Reaction Examples 11 to 13 and 15 and 16 are higher.

[0173] The preferred embodiments of the present disclosure are described in detail above. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0174] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0175] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing hexamethylenediamine from caprolactam, characterized in that: The method comprises the following steps: S1. Under catalytic amination reaction conditions, caprolactam, ammonia and a first catalyst are contacted to perform an amination-dehydration reaction to obtain a first product containing 6-aminocapronitrile; S2. Under catalytic hydrogenation reaction conditions, contacting the first product, hydrogen and a second catalyst to perform a hydrogenation reaction to obtain a second product containing hexamethylenediamine; Wherein, on a dry basis and based on the total weight of the first catalyst, the first catalyst is selected from 30-90 wt% of a titanium-containing support, 4-15 wt% of a vanadium oxide, 1-5 wt% of phosphorus pentoxide, 2-10 wt% of a metal M oxide and / or 0.1-2 wt% of an inorganic oxide; wherein the titanium-containing support comprises TiO2 and a titanium-containing molecular sieve, the metal M is selected from one or more of VB elements, VIB elements, VIII group elements and lanthanum elements, and the inorganic oxide comprises one or both of Al2O3 and SiO2; The catalytic amination reaction conditions include: a reaction temperature of 200-450° C., a molar ratio of ammonia to caprolactam of (1-10):1, an ammonia partial pressure of 0.2-3.0 MPa, and a caprolactam weight hourly space velocity of 0.5-20 h -1 ; The catalytic hydrogenation reaction conditions include: a reaction temperature of 150-350° C., a reaction pressure of 1.0-5.0 MPa, a molar ratio of hydrogen to 6-aminocapronitrile of 1-50:1, and a weight hourly space velocity of the liquid feed of 0.5-5 h -1 .

2. The method according to claim 1, characterized in that The amination and dehydration reaction is carried out in a fixed bed reactor.

3. The method according to claim 1, characterized in that On a dry basis, the weight ratio of TiO2 to the titanium-containing molecular sieve in the titanium-containing carrier is 1:(0.01-10); The titanium-containing molecular sieve includes titanium silicon molecular sieve; the titanium silicon molecular sieve is selected from one or more of HTS molecular sieve, TS-1 molecular sieve, TS-2 molecular sieve and TS-48 molecular sieve; The metal M is one or more selected from tungsten, molybdenum, chromium, zinc, manganese, lanthanum, zirconium and iron.

4. The method according to claim 3, characterized in that On a dry basis, the weight ratio of TiO2 to the titanium-containing molecular sieve in the titanium-containing carrier is 1:(0.1-5); The metal M is selected from one or more of tungsten, molybdenum and chromium.

5. The method according to claim 4, characterized in that The metal M is selected from one or both of molybdenum and tungsten.

6. The method according to claim 1, characterized in that The BET specific surface area of the first catalyst is 50-300 m 2 / g, the total pore volume is 0.1-0.4mL / g, and the micropore volume is 0.05-0.2mL / g.

7. The method according to claim 6, characterized in that The shape of the first catalyst is selected from one or more of spherical, bar, cylindrical, ring, clover, four-leaf, honeycomb and butterfly shapes.

8. The method according to claim 1, characterized in that The first catalyst is prepared by a preparation method comprising the following steps: a. contacting a vanadium source, water, and an acid to perform an oxidation-reduction reaction; adding a metal M source, a phosphorus source, and a titanium-containing support to the reaction product to obtain a mixture; and performing a first drying treatment on the mixture to obtain an intermediate solid product; b. subjecting the intermediate solid product to a molding process, a second drying process, and a calcination process in sequence.

9. The method according to claim 8, characterized in that In step a, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is (0.5-2.0): (0.05-0.2): (0.05-0.5): (0.02-0.5): (0.01-1):

1.

10. The method according to claim 9, characterized in that In step a, the weight ratio of water: vanadium source: acid: metal M source: phosphorus source: titanium-containing carrier is (0.8-1.6): (0.05-0.1): (0.1-0.3): (0.04-0.3): (0.02-0.6):

1.

11. The method according to claim 8, characterized in that The vanadium source is selected from one or more of ammonium metavanadate, sodium metavanadate and vanadium pentoxide; The acid is selected from one or more of oxalic acid, citric acid and nitric acid; The metal M in the metal M source is selected from one or more of tungsten, molybdenum, chromium, zinc, manganese, lanthanum and iron; the metal M source is selected from one or more of nitrates, phosphates and chlorides of metal M; The phosphorus source is selected from one or more of ammonium dihydrogen phosphate, sodium hypophosphite, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

12. The method according to claim 11, characterized in that The metal M source is selected from one or more of ammonium molybdate tetrahydrate, sodium tungstate, chromium nitrate and lanthanum nitrate.

13. The method according to claim 8, characterized in that Step a includes: dissolving the vanadium source in water, then adding the acid to the vanadium source solution to carry out the oxidation reaction to obtain an oxidation reaction product; adding the metal M source and the phosphorus source to the oxidation reaction product for first mixing to obtain a first mixture; adding the titanium-containing support to the first mixture and performing a second mixing to obtain a second mixture; The second mixture is subjected to the first drying treatment, and the obtained product is ground to obtain the intermediate solid product.

14. The method according to claim 13, characterized in that The temperature of the first mixing is 50-100° C. and the time is 60-300 min; The second mixing temperature is 30-80°C and the time is 30-300min; The temperature of the first drying treatment is 80-150°C.

15. The method according to claim 8, characterized in that The molding process in step b is extrusion molding; step b further comprises: extruding and mixing the intermediate solid product with a pore-enlarging agent and an auxiliary agent, and then sequentially performing the molding process, the second drying process, and the calcination process; or The forming process in step b is ball forming, and step b further comprises: mixing the intermediate solid product with an inorganic oxide source, and then sequentially performing the forming process, the second drying process and the calcination process.

16. The method according to claim 15, characterized in that On a dry basis and based on the added weight of the titanium-containing carrier, the amount of the pore-enlarging agent added is 0.5-10 wt %; the amount of the extrusion aid added is 0.5-4 wt %; The inorganic oxide source is added in an amount of 0.1-5 wt % based on dry basis and based on the added weight of the titanium-containing support.

17. The method according to claim 16, characterized in that On a dry basis and based on the added weight of the titanium-containing carrier, the amount of the pore-enlarging agent added is 1-5 wt %; the amount of the extrusion aid added is 0.5-2 wt %; The inorganic oxide source is added in an amount of 0.1-2.0 wt % based on dry basis and based on the added weight of the titanium-containing support.

18. The method according to claim 16, characterized in that In step b, the pore-enlarging agent is selected from one or more of sesbania powder, paraffin, stearic acid, glycerol, starch, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, polyacrylamine, cellulose methyl ether, cellulose, polyol and graphite; The extrusion aid is selected from one or more of organic acids, inorganic acids and inorganic bases; The inorganic oxide source is added in the form of inorganic oxide or inorganic oxide precursor; the inorganic oxide is selected from one or both of Al2O3 and SiO2; the inorganic oxide precursor is selected from one or more of aluminum sol, silica sol and water glass.

19. The method according to claim 18, characterized in that The extrusion aid is selected from one or more of oxalic acid, tartaric acid, citric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, ammonia water, sodium hydroxide and potassium hydroxide.

20. The method according to claim 8, characterized in that In step b, the conditions of the second drying treatment include: temperature of 80-200° C.; time of 1-10 hours; The calcination conditions include: a calcination temperature of 200-900° C.; and a calcination time of 0.5-10 h.

21. The method according to claim 20, characterized in that In step b, the conditions of the second drying treatment include: temperature of 100-150° C.; time of 2-4 hours; The calcination conditions include: a calcination temperature of 500-800° C.; and a calcination time of 2-4 hours.

22. The method according to claim 1, wherein In step S2, the catalytic hydrogenation reaction is carried out in a slurry bed reactor, and the second catalyst is selected from Raney nickel hydrogenation catalyst; or The catalytic hydrogenation reaction is carried out in a fixed bed reactor, and the second catalyst is selected from a supported hydrogenation catalyst; the supported hydrogenation catalyst is selected from one or more of nickel-based, cobalt-based and palladium-based catalysts.

23. The method according to claim 1, wherein The nickel-based catalyst is selected from 5-60 weight % of nickel, 0-40 weight % of cobalt and 40-90 weight % of a first carrier; the cobalt-based catalyst is selected from 5-60 weight % of cobalt and 40-95 weight % of a second carrier; the palladium-based catalyst is selected from 0.5-10 weight % of palladium and 90-99.5 weight % of a third carrier; wherein the first carrier and the second carrier are each independently selected from one or both of silicon oxide and aluminum oxide; and the third carrier is selected from one or both of activated carbon and aluminum oxide.

24. The method according to claim 1, wherein The method further includes: Before step S2, the first product is subjected to a first separation and purification treatment to obtain a product rich in 6-aminocapronitrile; and then the 6-aminocapronitrile-rich product is subjected to the catalytic hydrogenation reaction; and After step S2, the second product is subjected to a second separation and purification treatment.

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