A preparation method and application of a catalyst for preparing adiponitrile from adipic acid

Abstract

This invention belongs to the field of petrochemical catalysis technology, and relates to a method for preparing and applying a catalyst for the production of adiponitrile from adipic acid. The HY zeolite-supported monolayer dispersed ZnO catalyst provided by this invention can replace phosphoric acid or phosphate ester liquid catalysts and solid phosphoric acid catalysts, fundamentally avoiding the corrosion and scaling problems of the reactor during use.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical catalysis technology, and relates to a method for preparing and applying a catalyst for the production of adiponitrile from adipic acid. Background Technology

[0002] Adiponitrile is primarily used for hydrogenation to produce hexamethylenediamine. Hexamethylenediamine is an important basic organic chemical product. It can undergo condensation polymerization with adipic acid to produce polyamide-66 (nylon-66), and can also undergo condensation polymerization with sebacic acid, dodecanoic acid, and terephthalic acid to produce polyamide-610 (nylon-610), polyamide-612 (nylon-612), and polyamide-6T (nylon-6T), respectively. Polyamide plastic products are widely used in the automotive, machinery, electronics, and precision instrument industries. In addition, hexamethylenediamine is also used in a photochemical reaction with carbon dioxide to produce hexamethylene diisocyanate monomers, which are then used to prepare hexamethylene diisocyanate trimers or hexamethylene diisocyanate diurea as key raw materials for the production of polyurethanes with outstanding weather resistance and stability, used in coatings, leather, and plastics production. In the future, the application fields of adiponitrile are expected to be further expanded to the following areas: as a plasticizer in acetate, propionate, butyrate and mixed esters; to produce adiponitrile guanidine for the synthesis of melamine-urea amino resin as an auxiliary material in the textile industry to improve the antioxidant properties and stability of polymers such as polypropylene, polyacrylonitrile, polyoxymethylene, and polymethacrylate; as a solvent for textiles using acrylonitrile, methacrylonitrile, and methacrylate terpolymers; as a solvent for wet and dry spinning of polyvinyl chloride (PVC) fibers using a mixture of adiponitrile and tetrahydrofuran; and in electrolytic nickel plating, the addition of adiponitrile to improve the uniformity, brightness and gloss of the coating.

[0003] Adiponitrile can be produced by acrylonitrile electrolytic dimerization, butadiene hydrocyanation, adipic acid ammoniation dehydration, and caprolactam hydrolysis. Among these, the adipic acid ammoniation dehydration method has advantages such as simple process and low equipment investment, making it an important pathway for the future development of the adiponitrile industry. There are two processes for producing adiponitrile using the adipic acid ammoniation dehydration method: a liquid-phase process and a gas-phase process.

[0004] The following invention patents relate to the process of producing adiponitrile by liquid-phase ammoniation and dehydration of adipic acid: Chinese invention patent CN106146345B (filed in 2015, same batch of patents CN1061 40234B) discloses a method for producing adiponitrile by liquid-phase ammoniation dehydration of adipic acid. Its technical features include: using solid phosphoric acid as a catalyst, employing a batch reactor, diluting the raw material adipic acid with a diluent, and heating the adipic acid solution to a certain temperature under stirring before introducing ammonia gas for reaction.

[0005] The diluent is one or more of adiponitrile, glutaronitrile, and heptanilide. The mass ratio of adipic acid to the diluent is 1:2. The liquid-phase reaction is carried out at a reaction temperature of 260℃-280℃ for 0.5-2 h. The preparation method of the solid phosphoric acid catalyst is as follows: First, a certain amount of diatomaceous earth is dried in an oven at 100-140℃ for 1-2 h. Then, the dried diatomaceous earth is impregnated in an impregnation solution prepared by excess phosphoric acid solution (concentration 55-95%) and 15-25 wt% aluminum sulfate solution, stirred and impregnated for 6-12 h, and then allowed to stand for 6-12 h. Finally, the mixture is centrifuged, and the filter cake is dried (100-140℃, 6-12 h) and calcined (300℃-700℃, N2 protection, 1-2 h) to obtain the solid phosphoric acid catalyst.

[0006] The specific description of the method in Example 1 is as follows: 10 g of diatomaceous earth was dried in an oven at 120°C for 2 h, then impregnated in 120 g of 75 wt.% phosphoric acid solution, and 6 g of 20 wt.% aluminum sulfate solution was added. The mixture was stirred and impregnated for 12 h, then allowed to stand for another 12 h. Finally, the mixture was centrifuged, and the filter cake was dried in an oven at 120°C for 12 h, then calcined in a tubular calcination furnace for 2 h (400°C, N2 protection) to obtain a solid phosphoric acid catalyst. 73 g of adipic acid, 146 g of adiponitrile, and 1.4% solid phosphoric acid catalyst were added to the reactor. The reactants were heated to 270°C, and ammonia gas (flow rate of 150 L / h) was introduced while stirring. After 60 min of reaction, the total dehydration rate of adipic acid to adiponitrile via ammoniation was 73.6%. In Example 4, by changing the composition and calcination conditions of the catalyst, and by appropriately increasing the amount of catalyst and optimizing the reaction conditions, the total dehydration rate of adiponitrile produced by adipic acid ammoniation dehydration after 60 min of reaction reached 94.7%.

[0007] Chinese invention patent CN108821997B (application date 2018) discloses a method for preparing adiponitrile and its product. Its technical features include: a production system comprising an adipic acid storage tank (containing molten adipic acid), an adipic acid transfer pump, a mixer (for mixing with phosphoric acid or ammonium phosphate catalyst), an adipic acid ammoniation reactor, a nitrification reactor (heated by VP-1 heat transfer oil steam with good thermal stability and low viscosity), a separation tower, an ammonia cooler, an ammonia decarbonization tower, a circulating ammonia dehydrator, and a liquid ring compressor, etc., to prepare adiponitrile. In the ammoniation reactor, adipic acid reacts with ammonia to form diammonium adipic acid salt. The ammoniation reaction temperature range is 155-200℃ (160℃, 170℃, and 180℃ are used in the examples), and the molar ratio of ammonia to adipic acid is 2-16 (8:1, 10:1, and 16:1 are used in the examples). In the nitrification reactor, diammonium adipic acid salt undergoes liquid-phase dehydration under the catalysis of phosphoric acid (ammonium phosphate) to form adiponitrile, and the reaction temperature is 260-290℃. The amount of phosphoric acid (ammonium phosphate) used, based on the diammonium adipic acid feed rate, is 3000-30000 ppm (2000 ppm is used in the examples).

[0008] The process principle of the production system is as follows: An adipic acid storage tank is connected to a mixer via a pipeline, which is connected to a branch line for transporting liquid phosphoric acid catalyst. The mixer is connected to the inlet of the adipic acid ammoniation reactor. The adipic acid ammoniation reactor is also equipped with an ammonia inlet and an outlet that can send the ammoniation product to the downstream nitrification reactor via a pipeline. The nitrification reactor is connected to a downstream separation tower. The lower part of the separation tower (containing wire mesh packing) can return the semi-nitrile circulating liquid to the bottom of the nitrification reactor via a pipeline. The upper middle part of the separation tower has an adiponitrile liquid outlet, and the upper part is connected to an ammonia decarbonization tower via an ammonia reflux cooler. The ammonia decarbonization tower is connected in sequence to a downstream circulating ammonia dehydrator and a liquid ring compressor via pipelines. The ammonia outlet of the liquid ring compressor (using adiponitrile as the working medium) is connected to the ammonia inlet of the adipic acid ammoniation reactor.

[0009] It is worth mentioning that the bottom of the separation tower in the production system (which is equipped with wire mesh packing, and a chimney plate is installed above the wire mesh packing) can further convert unreacted adipic acid into diammonium adipic acid salt under temperature conditions of 155~200℃ (bottom temperature 280℃, pressure 15 KPa), and further dehydrate and convert various intermediates into adiponitrile under the catalysis of phosphoric acid or ammonium phosphate. The molar selectivity of adiponitrile product given in Example 1 of this invention patent is 93% (adipic acid feed 2400 kg / h, adiponitrile output 1650 kg / h).

[0010] Chinese invention patent CN110790678B (application date 2019) discloses a method for synthesizing adiponitrile through liquid-phase amination and high-temperature dehydration of adipic acid. Its technical features include the following steps: First, diammonium adipic acid salt is prepared in a neutralization reactor using an aqueous solution of adipic acid and ammonia. Then, the solid diammonium adipic acid salt is separated by a solid-liquid separator, heated and melted into a liquid, and fed into a falling film reactor along with phosphoric acid and / or a phosphate catalyst for dehydration reaction, separating the organic phase to obtain crude adiponitrile. Finally, the crude adiponitrile is mixed with an azeotropic agent of water, and the water in the adiponitrile is removed by azeotropic distillation, yielding purified adiponitrile product from the bottom of the distillation column.

[0011] In the method described above, the preparation conditions for diammonium adipic acid salt are: adipic acid:water = (0.1-1):1, reaction temperature 20-100℃, pressure 0.1-3 MPa, and sufficient or excess ammonia. The obtained diammonium adipic acid salt is in aqueous solution state. Before feeding the diammonium adipic acid salt into the falling film reactor for dehydration reaction, the solid diammonium adipic acid salt needs to be melted at a temperature range of 220-250℃. The falling film reactor contains two reaction zones: a low-temperature reaction zone (temperature 240-260℃) and a high-temperature reaction zone (temperature 260-320℃). The catalyst for the dehydration reaction is phosphoric acid and / or phosphate, and its amount is 2%-6% of adipic acid (or its diammonium salt). The diammonium salt is dehydrated in the low-temperature zone to generate adipamide, which is then dehydrated in the high-temperature zone to generate crude adiponitrile. In the azeotropic distillation column, the feed ratio of crude adiponitrile to dehydrating agent is (0.5-5):1. The dehydrating agent is benzene, toluene, or xylene.

[0012] Chinese utility model patent CN212758581U (application date 2020) discloses a pre-reaction apparatus for the preparation of adiponitrile from adipic acid. The pre-reaction apparatus is used to react adipic acid and ammonia in an ethanol solvent (reaction temperature 60℃, 0.5h) to prepare ammonium adipate. Ammonium adipate with a purity of 99% can be obtained from the lower outlet of the apparatus.

[0013] Chinese utility model patent CN213506680U (application date 2019) discloses a reaction system for preparing adiponitrile by amination of adipic acid. Its technical feature is that the system consists of an amination reactor, a gas-liquid separator, and a distillation column connected in sequence. The amination reactor includes two micro-interface generation systems.

[0014] Chinese invention patent CN113185427B (application date 2021) discloses a system and method for preparing adiponitrile from adipic acid. The system includes a pre-reactor, an ammoniation reactor, a nitrile separation tower, a rinsing system, a purification reactor, a purification unit, an ammonia recovery unit, and a heat exchange system. Its technical feature is that the heat exchange system is a dual-loop heating system using two different heat transfer media. The first heat transfer media circulates in a first loop between the heater and the first heat exchanger. The second heat transfer media circulates in a second loop between the first exchanger and the user. The boiling point of the first heat transfer media is higher than that of the second heat transfer media, and the first heat transfer media transfers heat to the second heat transfer media by sensible heat, while the second heat transfer media transfers heat to the user by latent heat. Its technical feature further lies in that molten adipic acid reacts with ammonia in the presence of a phosphoric acid catalyst to produce adiponitrile. The heat required for the ammoniation / dehydration reaction is provided by the first heat transfer media through the second heat transfer media. First, molten adipic acid, ammonia, phosphoric acid catalyst, and the recycled stream (a mixture of nitrile and semi-nitrile intermediates) from the nitrile separator are fed into a pre-reactor (typically operating in the range of 250-270°C). The pre-reactor's role is to mix the reactants, providing a homogeneous mixture for the ammoniation reactor. The ammoniation reactor is a vertical shell-and-tube isothermal reactor in which the reaction of adipic acid to form adiponitrile and intermediates takes place within the tubes. The shell side is filled with a flowing second heat transfer medium. This heat transfer medium is selected to maintain the temperature of the reaction zone in the range of 275°C to 300°C (e.g., 280°C to 296°C). The effluent from the ammoniation reactor enters a nitrile separator, where crude adiponitrile is collected at the top and sent to a flushing system. The liquid flowing downwards in the stripping section of the nitrile separator mainly contains intermediates such as nitrile and semi-nitrile. These intermediates continue to undergo dehydration reactions to form adiponitrile as they descend in the stripping section. The lower part of the stripping section of the nitrile separator is equipped with a bottom-chimney tray, which collects the circulating stream and returns it to the ammoniation reactor. The tail liquid of the nitrile separator (containing adiponitrile and adipamide, cyanopenic acid and cyanopentamide, and other intermediate reaction products, as well as the remaining acid catalyst) is sent to a refining reactor for further processing to increase the adiponitrile yield. The refining reactor typically operates in a temperature range of 275°C to 350°C.

[0015] Chinese invention patent CN115814713A (application date 2021) discloses a system and method for preparing adiponitrile from adipic acid. The system includes a raw material preparation tank, a nitrification reactor, a gas-to-gas heat exchanger, and a preheater. The outlet at the bottom of the raw material preparation tank is connected to the inlet at the top of the nitrification reactor via a first pipe, and the first pipe is equipped with a preheater. The nitrification reactor also has an inlet, which is connected to an ammonia source via a second pipe. The second pipe is equipped with a heat exchanger for gas-to-gas heat exchange. Furthermore, the nitrification reactor has a gas phase outlet. The gas phase outlet is connected to the inlet of an ammonia separation unit via a third pipe and the gas-to-gas heat exchanger. The outlet (ammonia source) of the ammonia separation unit is connected to the second pipe. The nitrification reactor has a tubular structure, and a liquid distributor is located at the top of the tubular structure. Additionally, to facilitate the reaction, the nitrification reactor provided by this invention operates in a countercurrent contact manner between ammonia and the reaction liquid.

[0016] Chinese invention patent CN116655494A (application date 2023) discloses a method for preparing adiponitrile, the technical feature of which includes the following steps: firstly, dimethyl adipate is reacted with liquid ammonia and / or ammonia water at room temperature to obtain an aminated material; then, the aminated material is dehydrated under the action of a dehydration catalyst to obtain adiponitrile. Example 1 illustrates the method as follows: (1) Dimethyl adipate is reacted with liquid ammonia or ammonia water at room temperature, with a feed molar ratio of 1:3.5. In order to overcome the problem of raw material stratification (liquid-liquid two-phase), mechanical stirring is required to effectively mix the two liquid phases, and the reaction is carried out at a constant temperature of 30°C for at least 6 hours to make the oil phase disappear, thereby obtaining the aminated material; (2) The aminated material that has been properly pretreated is mixed with 0.8wt% phosphoric acid or ammonium phosphate and fed into a dehydration reactor for high-temperature dehydration reaction. In addition to adiponitrile, the reaction also produces byproducts such as cyclopentanone, methyl 5-cyanopentanoate, and monomethyl adipic acid ester. The products also include a certain amount of unreacted dimethyl adipic acid ester.

[0017] Chinese invention patent CN120189887A (application date 2023) discloses a continuous process for preparing adiponitrile from adipic acid under supergravity conditions. Its key technical feature is that the device is a continuous supergravity preparation apparatus employing a specially designed gas-liquid mixing feed mode, which can reduce side reactions by precisely controlling the reaction temperature in the falling film assembly. Another key feature is that the gas-liquid contact method on the falling film assembly is not countercurrent, but rather a gas-liquid co-flow contact method. This co-flow avoids liquid stagnation in the pipeline. Furthermore, it utilizes a phosphoric acid catalyst and employs a supergravity assembly to enhance the mixing and mass and heat transfer of adipic acid and ammonia molecules during the reaction, thereby effectively mitigating adipic acid decomposition and coking in the bubbling section of a traditional reactor.

[0018] Chinese invention patent CN120132771A (filed in 2023) discloses an adiponitrile preparation apparatus and method based on a falling film reactor. Its technical feature is that the adiponitrile preparation apparatus includes a falling film reactor and a stirring assembly. The falling film reactor includes several falling film tubes, which are sleeve structures. A heat exchange liquid is circulated inside the sleeves of the falling film tubes to control the reaction temperature of adipic acid and ammonia. Its further feature is that the stirring assembly includes a stirring tank, a stirring paddle, and a motor.

[0019] In summary, the liquid-phase ammoniation dehydration process for producing adiponitrile from adipic acid involves two main reactions: the first step is a non-catalytic ammoniation reaction between adipic acid and ammonia, producing diammonium adipic acid salt; the second step is a catalytic dehydration reaction of the diammonium adipic acid salt, with adiponitrile as the main product. The first ammoniation reaction is relatively easy, can be carried out at room temperature, and easily achieves 100% selectivity. However, the second dehydration reaction is more difficult and generally requires higher temperatures (typically around 280℃). The dehydration reaction of the diammonium adipic acid salt proceeds stepwise, producing multiple intermediate products such as adipamide, cyanovaleric acid, and cyanovaleramide. In addition, adipic acid is prone to decarboxylation and other side reactions at high temperatures, generating byproducts such as cyclopentanone, which can cause coking in the reactor; cyanopentanoic acid and cyanopentamide cyclize at high temperatures to form adipamide and hexamethylene ester; adiponitrile isomerizes to form conjugated compounds 1-imino-2-cyanocyclopentane or 1-amino-2-cyanocyclopentene; adiponitrile forms dimers when heated for a long time; and adiponitrile and adipamide resinify at high temperatures, etc.

[0020] Catalysts are key factors affecting the activity and selectivity of the dehydration reaction of diammonium adipic acid. To date, the liquid-phase ammoniation dehydration process of adipic acid to adiponitrile mainly uses phosphoric acid (phosphate) or phosphate ester liquid catalysts in industrial applications. The main problems with these liquid catalysts include: (1) Phosphoric acid (phosphate) and phosphate ester liquid catalysts have a relatively serious corrosive effect on the metal materials of the reactor; (2) Both phosphoric acid (phosphate) and phosphate ester liquids will generate polyphosphoric acid, which will be deposited on the walls of the shell-and-tube isothermal reactor, affecting the heat transfer efficiency and temperature distribution; (3) Immobilizing liquid phosphoric acid and using it in the form of solid phosphoric acid cannot fundamentally avoid the above problems.

[0021] In view of the above, many researchers in this field are dedicated to finding alternative catalysts for the process of liquid-phase ammoniation dehydration of adipic acid to adiponitrile.

[0022] Chinese invention patent CN111250113A (filed in 2018) discloses a method for using a superacid catalyst in the direct synthesis of adiponitrile from adipic acid. The superacid catalyst is composed of SO42-. 2-It consists of an oxide support. The oxide support is at least one selected from SiO2, CeO2, TiO2, ZrO2, and Al2O3. In the direct synthesis of adiponitrile from adipic acid, adipic acid is diluted with a diluent and then reacts with ammonia. The diluent is one or more selected from adiponitrile, glutaronitrile, and heptanilide. Adiponitrile is preferred. The mass ratio of adipic acid to diluent is (0.1-5):1.

[0023] Chinese invention patent CN111054436 B (application date 2019) discloses the application of a plasma-modified phosphotungsten heteropolyacid catalyst in the synthesis of adiponitrile from adipic acid. The adipic acid-to-adiponitrile reaction is carried out in the presence of a diluent. The diluent is one or more of adiponitrile, glutaronitrile, and heptanilide.

[0024] Chinese invention patent CN111056972B (application date 2019) discloses the application of an alkyl quaternary phosphonium salt ionic liquid catalyst in the synthesis of adiponitrile from adipic acid. The alkyl quaternary phosphonium salt ionic liquid is prepared in a one-step process from the corresponding imidazole and phosphate ester. The method for catalyzing the reaction of adipic acid to adiponitrile using the ionic liquid is as follows: at a certain temperature, the ionic liquid catalyst, adipic acid, and adiponitrile are added to a reaction vessel, excess ammonia gas is introduced, and the reaction is carried out for a certain time to obtain the product adiponitrile.

[0025] Chinese invention patent CN114160120B (filed in 2021) discloses a method for preparing a catalyst for the production of adiponitrile from adipate ester. The technical feature of this method is that a pyridine-based ionic liquid is first impregnated onto a catalyst support, and then the active component of the catalyst is impregnated onto the support loaded with the ionic liquid using an impregnation method, resulting in an impregnated material. The impregnated material is then dried and calcined to obtain the catalyst for the production of adiponitrile from adipate ester. The pyridine ionic liquid is any one or a combination of at least two of [C4PyM]Cl, [C4PyM]Br, [C4PyM]BF4, [C6PyM]Cl, [C2Py]Cl, [C4Py]Cl, and [C4Py]Br; the active component is a niobium salt, or a niobium salt and a molybdenum salt, or a niobium salt, a molybdenum salt, and a bismuth salt; the support is any one of molecular sieves, Al2O3, SiO2, and a composite of alumina and silica; wherein the molecular sieve is any one of SBA-15, ZMS-5, SAPO-34, β-molecular sieve, HY-type molecular sieve, and mordenite. The calcination treatment is calcination under an air or nitrogen atmosphere or ordinary calcination, with a calcination temperature of 200-800℃, preferably 350-550℃. Example 2 describes the preparation method and application of the catalyst as follows: (1) Catalyst preparation: On one hand, 8 g of [C4PyM]Br was added to 400 mL of water and stirred evenly at 25 °C. Then, 80 g of SiO2 was added for stirring and impregnation at 30 °C. On the other hand, 25 g of niobium oxalate, 6 g of ammonium heptamolybdate, and 6 g of bismuth nitrate were dissolved in 200 mL of water to obtain an active component solution. Then, the active component solution was added to an ionic liquid impregnation container under stirring for impregnation of the active component. Finally, the solution was vacuum dried and calcined in a muffle furnace at 350 °C for 3 h to obtain the catalyst. (2) Preparation of adiponitrile: The reaction of adipate to adiponitrile was carried out in a 70 mL moving bed reactor. The reaction temperature was 335 °C, the molar ratio of amine to ester was 12, and the feed space velocity was 8.0 / h. After 3 h, the sample was analyzed and the conversion rate of adipate was 96.7%, and the selectivity of adiponitrile was 89.6%.

[0026] Chinese invention patent CN1180476A (filed in 2024) discloses a method and apparatus for synthesizing dinitrile products from nylon acid and / or nylon esters, characterized by the use of a continuous reactor. The continuous reactor includes any one of a continuous stirred tank reactor, a plug flow reactor, a fixed bed reactor, and a fluidized bed reactor, preferably a fluidized bed reactor; it further features the use of a solid acid catalyst. The solid acid catalyst is selected from one or more of solid phosphoric acid, ion exchange resin, γ-Al₂O₃, silica gel, ZrO₂, CeO₂, WO₃, Nb₂O₄, and zeolite molecular sieves; wherein the zeolite molecular sieve is selected from one or more of ZSM-5, HY, and Hβ-phosphorus.

[0027] Clearly, the practical value of the aforementioned alternative catalysts still needs to be tested in practice.

[0028] During the literature review, the following invention patents were found to involve the process of producing adiponitrile by vapor-phase ammoniation and dehydration of adipic acid: Chinese invention patent CN111848447A (application date 2019) discloses a method for preparing adiponitrile by gas-phase ammoniation dehydration of adipic acid. Its technical feature is that adipic acid is heated and vaporized with an ammonifying agent, then mixed with a preheated carrier gas, and introduced into a fixed-bed or fluidized-bed reactor to undergo an ammoniation dehydration catalytic reaction. The ammonifying agent is any one or any combination of ammonia, ammonia water, urea, ammonium bicarbonate, ammonium carbonate, or ammonium chloride. The carrier gas is ammonia, hydrogen, helium, nitrogen, argon, water vapor, or a combination thereof. The catalyst used in the fixed-bed or fluidized-bed reactor includes a main catalyst and a co-catalyst. The main catalyst is any one or any combination of kaolin, diatomaceous earth, alumina, oxidized state, zirconium oxide, phosphate-diatomaceous earth, phosphate-silica, or zeolite molecular sieves that have undergone pore-expanding treatment and are rich in 2-20 nm mesopores, while also possessing a certain degree of acidity. The co-catalyst is any one of the elements Ti, La, Ce, Zn, Mn, Cu, Fe, Co, Ni, K, Na, Cs, Ca, Mg, Mo, W, Sn, Ge, Bi, and P, or any combination thereof.

[0029] Chinese invention patent CN115990498B (application date 2021) discloses a vanadium-based catalyst and a method for catalytic synthesis of adiponitrile. Its technical feature is that, in addition to vanadium, the catalyst also contains chromium, phosphorus and molybdenum. The catalyst is used for the gas-phase catalytic synthesis of adiponitrile from adipic acid. Example 1 describes the method as follows: (1) Catalyst preparation: First, 58 g of vanadium pentoxide and 48 g of chromium trioxide are dissolved in 1000 g of an aqueous solution containing 180 g of oxalic acid, and 105.2 g of a phosphoric acid solution with a concentration of 85.54 wt% is added to the solution and stirred for 2 hours; then, 21.3 g of ammonium molybdate (NH4)2MoO4 and 1.86 g of sodium chloride are slowly added to the solution and stirred for 2 hours; finally, 1.65 g of nickel chloride and 2.3 g of cesium sulfate are added to the solution and stirred for 3 hours. The molar ratio of each metal element in the obtained solution is V:Cr:P:Mo:Na:Ni:Cs = 1:0.75:1.44:0.17:0.05:0.02:0.02. 660 g of silica gel with a particle size of 80 mesh was added to the above solution, stirred evenly, impregnated at 20-30℃ for 48 hours, filtered to obtain filter cake, and then the filter cake was made into spray-dried powder. The catalyst powder was subjected to programmed temperature calcination treatment in a muffle furnace (calcined at 400℃ for 6 h, calcined at 600℃ for 12 h) to obtain vanadium-chromium-phosphorus catalyst supported on silica. (2) Catalyst application: 110 g of vanadium-chromium-phosphorus catalyst supported on silica was loaded into In a 38 mm high, 600 mm high fluidized bed reactor, a mixture of adipic acid, ammonia, and nitrogen was continuously introduced at a reaction system pressure of 0.04 MPa to carry out a gas-phase fluidized bed reaction for the production of adiponitrile from adipic acid. The molar ratio of ammonia to adipic acid was 8:1, and the molar ratio of nitrogen to adipic acid was 20:1. The catalyst's catalytic processing capacity was 5.8 g of adipic acid per hour for every 100 g of catalyst.

[0030] The gas-phase ammoniation and dehydration process for producing adiponitrile from adipic acid has advantages such as a more complete reaction and fewer intermediate products. Furthermore, since gas-phase processes generally use solid phosphoric acid catalysts or other solid acid catalysts, they can effectively overcome problems such as catalyst corrosion of equipment. However, due to the high reaction temperature (≥330℃) and high energy consumption of gas-phase processes, coupled with the severe decarboxylation decomposition of adipic acid at high temperatures and the large amount of byproducts such as cyclopentanone and cyclohexylimine, gas-phase processes have consistently struggled to compete with liquid-phase processes in industrial applications.

[0031] Furthermore, our literature review revealed the following invention patents and published documents concerning the preparation of 6-hydroxyhexanonitrile via caprolactone ammoniation dehydration. The preparation of 6-hydroxyhexanonitrile via caprolactone ammoniation dehydration essentially involves two reaction steps: (1) caprolactone reacts with an ammonia source to generate ammonium 6-hydroxyhexanoate; (2) the ammonium 6-hydroxyhexanoate is dehydrated to generate 6-hydroxyhexanonitrile. Therefore, the preparation of 6-hydroxyhexanonitrile via caprolactone ammoniation dehydration is fundamentally similar to the adipic acid ammoniation dehydration method.

[0032] US Patent US3600423 (filed in 1969) discloses a gas-phase method for preparing 6-hydroxyhexanonitrile. Its key technical feature is the use of zinc oxide as a catalyst, contacting caprolactone with ammonia at a temperature range of 270-325°C, and carrying out ammoniation and dehydration reactions under normal pressure to obtain the 6-hydroxyhexanonitrile product. The reactor is a fixed bed, with a reaction tube inner diameter of 2.5 cm and a height of 25 cm. The zinc oxide catalyst has a particle size of 3 mm. The molar ratio of caprolactone, hydrogen, and ammonia is 1:7:18, the caprolactone feed rate is approximately 5-10 g per hour, and the residence time is 2-5 s. The results provided in Examples 1-4 indicate that when the reaction temperature is in the range of 270-300°C, the selectivity of 6-hydroxyhexanonitrile is 100%, and the conversion rate of caprolactone is between 26-73%. The results provided in Examples 5 and 6 indicate that when the reaction temperature is increased to 320°C and 325°C, the selectivity of 6-hydroxyhexanonitrile decreases significantly, to 73% and 72%, respectively. At this point, the conversion rate of caprolactone increases, reaching 87% and 86%, respectively. When the reaction temperature is further increased to 340°C and 350°C, the selectivity of 6-hydroxyhexanonitrile decreases further, to 32% and 16%, respectively. At this point, the conversion rate of caprolactone increases to 91-96%. When the reaction temperature is increased to 380°C, the conversion rate of caprolactone reaches 100%, while the selectivity of 6-hydroxyhexanonitrile decreases to 4%.

[0033] Chinese invention patent CN11476347B (application date 2022) discloses a method for preparing adiponitrile. Its technical feature is the use of a fixed-bed reaction process, using ε-caprolactone as the initial raw material, to obtain adiponitrile through a two-step atmospheric pressure gas-phase catalytic reaction. The first step involves vaporizing and mixing caprolactone and ammonia, then subjecting the mixture to ammoniation and dehydration reactions in an atmospheric pressure fixed-bed reactor containing catalyst I to obtain 6-hydroxyhexanonitrile. The reaction temperature is between 200℃ and 350℃, the molar ratio of caprolactone to ammonia is between 1:3 and 10, and the volume hourly space velocity (VHSV) of the mixed gas of caprolactone and ammonia passing through the catalyst I bed is 200 h⁻¹. -1 ~1000 h -1The active component of catalyst I is an oxide of metal M. Metal M is one of Al, Zn, Zr, Ti, and Fe. Catalyst I is prepared by co-precipitation or kneading extrusion, with a calcination temperature of 400-600℃. The second step involves vaporizing 6-hydroxyhexanonitrile and mixing it with ammonia and hydrogen, then further ammoniation and dehydration reactions in a fixed-bed reactor loaded with catalyst II at atmospheric pressure to obtain adiponitrile. The reaction temperature is between 250℃ and 350℃, the molar ratio of 6-hydroxyhexanonitrile to ammonia and hydrogen is between 1:(2-8):(1-6), and the volume hourly space velocity (VHSV) of the reaction mixture gas through the catalyst II bed is 400 h⁻¹. -1 ~1000 h -1 The catalyst II comprises a support and a substrate. The substrate is a catalytically active component or a mixture of a catalytically active component and a co-catalyst component. The catalytically active component and the co-catalyst component are oxides of metal M, including Ni, Cu, Fe, Zn, Co, Mn, Cr, and rare earth metals La, Ce, or Pr. The support is one or more of Al₂O₃, SiO₂, TiO₂, and MgO. The catalyst II can be prepared by impregnation, co-precipitation, or kneading extrusion, and its reduction temperature is 500–800 °C.

[0034] Example 4 illustrates the method as follows: First, ZnO was prepared as catalyst I using a co-precipitation method: 120.0 g of Zn(NO3)2·6H2O was dissolved in 500 mL of deionized water to obtain solution A. 54.0 g of oxalic acid was dissolved in 600 mL of deionized water to obtain solution B. Solution A was added dropwise to solution B at room temperature and with stirring to obtain a precipitate. After the addition was complete, stirring was continued for 2 h. Then, the precipitate was filtered, and the filter cake was washed twice with 200 mL of deionized water and dried at 100 °C for 12 h. Finally, the dried precipitate was calcined in a muffle furnace at 400 °C for 3 h (heating rate 5 °C / min) to obtain the powdered precursor of the zinc oxide catalyst. To prepare the zinc oxide catalyst prototyping for a fixed-bed reactor, 25.0 g of zinc oxide catalyst powder precursor was weighed, 0.7 g of guar gum powder was added, and the mixture was ground evenly. A suitable amount of water was added to form a paste suitable for extrusion molding. The paste was then extruded into strips approximately 2 mm in diameter. The precursor was air-dried at room temperature for 12 h, and then dried in a blower at 80℃ for 4-5 h. The dried catalyst precursor was then calcined in a muffle furnace at a heating rate of 2℃ / min to 500℃ for 3 h, finally yielding extruded ZnO as catalyst I.

[0035] Example 16 describes the method for preparing 6-hydroxyhexanonitrile on catalyst I as follows: 20 mL of the catalyst prepared in Example 4 was added to a fixed-bed reactor (12 mm in diameter and 600 mm in length). The temperature was raised to 350 °C under nitrogen protection. Then, ammonia and caprolactone (a mixed gas after heating and vaporization, with a volume hourly space velocity of 1000 h⁻¹ through the catalyst bed) were introduced into the fixed-bed reactor, wherein the molar ratio of ammonia to caprolactone was 6:1. The reaction system was at atmospheric pressure. The reaction solution was obtained by catalytic ammonia nitrification. The gas chromatography internal standard method was used for analysis, and the conversion rate of caprolactone was 75.2%, and the selectivity of 6-hydroxyhexanonitrile was 58.6%.

[0036] The published paper "Wang Ke, Research on Two-Step Synthesis of Adiponitrile from ε-Caprolactone [M]. Hebei University of Technology, 2022" reports the performance of metal oxide catalysts such as TiO2, ZnO, Al2O3, and SiO2 prepared by the kneading and extrusion method in the catalytic synthesis of 6-hydroxyhexanonitrile from caprolactone in an atmospheric pressure fixed-bed reactor. The authors selected TiO2 as the optimal catalyst. The optimal reaction conditions for the synthesis of 6-hydroxyhexanonitrile from caprolactone, obtained through single-factor experiments, were: reaction temperature 270 ℃, atmospheric pressure, a molar ratio of ε-caprolactone to ammonia feed of 1:6, and a residence time of 6 s. Under these conditions, the conversion rate of ε-caprolactone reached 94.89%, and the selectivity of 6-hydroxyhexanonitrile reached 94.08%. After 60 h of continuous reaction, the conversion rate of ε-caprolactone and the yield of 6-hydroxyhexanonitrile began to decrease. The catalyst's catalytic performance could be restored by regenerating it using a high-temperature oxidation method. In addition, the authors investigated the catalytic performance of a series of supported bimetallic catalysts for the amination synthesis of adiponitrile from 6-hydroxyhexanonitrile (6-HHN) in a fixed-bed reactor. The results showed that the nickel-iron bimetallic catalyst (code-named Ni) supported on a magnesium-aluminum composite oxide support was effective. 30 Fe 10 The catalyst with the ratio of Al₂O₃-MgO (0.8:1.2)-700-2 exhibits the best performance. Under optimal conditions (atmospheric pressure, reaction temperature 300 °C, 6-HHN:ammonia:hydrogen molar ratio of 1:5:2, and residence time of 5 s), this catalyst can achieve a conversion of 6-hydroxyhexanonitrile of 63.06% and a selectivity of adiponitrile of 51.49%.

[0037] The published paper *Ind. Eng. Chem. Res. 2023, 62, 1338-1349* also reports a catalytic system and reaction method for the production of adiponitrile from caprolactone via 6-hydroxyhexanonitrile. However, in this paper, the authors used a ZnO catalyst to catalyze the amination of caprolactone to 6-hydroxyhexanonitrile, and then used a nickel-iron bimetallic catalyst (Ni2O2O2O2) supported on an Al2O2-MgO composite oxide support. 30 Fe 10Under the same optimal conditions (reaction temperature 300℃, atmospheric pressure, 6-HHN:NH3:H2 = 1:5:2, residence time of reactants in a fixed-bed reactor of 5 s), the catalytic amination of 6-hydroxyhexanonitrile to adiponitrile was also obtained, with a conversion rate of 63.1% for 6-HHN and a selectivity of 51.5% for adiponitrile. Summary of the Invention

[0038] The purpose of this invention is to provide a method for preparing a catalyst for the production of adiponitrile from adipic acid and its application.

[0039] Specifically, the catalyst provided by this invention is a supported zinc oxide (ZnO) catalyst that is monolayer dispersed on a HY zeolite support. The catalyst is prepared by solid-state ion exchange treatment of the HY zeolite support with an easily fusible zinc salt, and is applied in the dehydration and nitrification reaction of diammonium adipic acid in the liquid-phase reaction process for the production of adiponitrile from adipic acid.

[0040] As mentioned earlier, the liquid-phase ammoniation dehydration process of adipic acid to adiponitrile involves two main reactions: the first step is the ammoniation reaction of adipic acid with ammonia to produce diammonium adipate. This reaction is relatively easy, requires no catalyst, can be carried out at room temperature, and has almost no side reactions. The second step is the dehydration and nitrification reaction of the diammonium adipate to produce the target product, adiponitrile. Compared to the ammoniation reaction, the dehydration and nitrification reaction is more difficult, involving multiple elementary reaction steps. It not only requires the participation of a catalyst but also demands a higher temperature (typically around 280°C) to proceed.

[0041] To date, in industrial production, the liquid-phase dehydration and nitrification reaction of diammonium adipic acid salt still uses phosphoric acid (phosphate) or phosphate ester liquid catalysts. The main problems with these liquid catalysts include: (1) they all have a relatively severe corrosive effect on the metal materials of the reactor; (2) they all generate polyphosphoric acid. Polyphosphoric acid can deposit on the tube walls of the reactor, reducing the heat transfer efficiency of the tube walls and thus disrupting the uniformity of temperature distribution in the reaction tubes; (3) immobilizing liquid phosphoric acid and using it in the form of solid phosphoric acid cannot fundamentally avoid the above problems.

[0042] The reason this invention proposes using a monolayer dispersed zinc oxide (ZnO) catalyst supported on HY zeolite in the liquid-phase dehydration and nitrification reaction of diammonium adipic acid is precisely to overcome the aforementioned problems existing in the industrial application of existing catalysts. Those skilled in the art know that HY zeolite is a non-corrosive, non-polluting, and regenerable zeolite molecular sieve catalyst, and is the most widely used zeolite solid acid catalyst in the petroleum refining industry (catalytic cracking to gasoline production process). ZnO is a solid acid-base catalyst (Zn... 2+ The ion is the Lewis acid center, O 2-ZnO (with Lewis base centers) also possesses the advantages of being non-corrosive and non-polluting. Bulk ZnO catalysts are widely used in dry desulfurization processes in the oil and gas industry. This invention utilizes a solid-state zinc ion exchange catalyst preparation process to organically combine ZnO in a monolayer dispersed supported form with the inner and outer surfaces of a HY zeolite support, becoming a catalyst for the dehydration and nitrification reaction of diammonium adipate. Undoubtedly, in the catalyst provided by this invention, both the HY zeolite as a support and the ZnO as a supported form retain their advantages of being non-corrosive and non-polluting when used independently. Furthermore, our research has found that in the reaction environment of liquid-phase dehydration and nitrification of diammonium adipate, neither the HY zeolite support nor the monolayer dispersed ZnO active phase undergoes structural or compositional changes such as dissolution or loss, nor does it experience scaling or deposits on the reactor walls.

[0043] More importantly, research has also revealed that the catalyst preparation method provided by this invention has the following characteristics: (1) Due to the low silicon-to-aluminum ratio of HY zeolite (SiO2 / Al2O3=5-6), the density of exchangeable hydrogen protons generated by framework aluminum on its inner and outer surfaces is high (interspersed with 2-3 SiO4 tetrahedra). Therefore, when HY zeolite is subjected to solid zinc ion exchange treatment with easily fusible zinc salt, a large number of zinc cations that are uniformly distributed at ion exchange sites and have strong electrostatic interaction with framework aluminum anions can be generated on the inner and outer surfaces of the zeolite through the exchange reaction between zinc ions and hydrogen protons (in every 100g of HY zeolite, [Zn(OH)]). + Zn in form 2+ (14-16g of cations). These high-density zinc cations located at ion exchange sites form a monolayer dispersed ZnO active phase on the inner and outer surfaces of the HY zeolite support with high loading of ZnO, which has a structure-inducing and linking anchoring effect; (2) HY zeolite not only has a large ion exchange capacity, but also has an open supercage structure and a three-dimensional twelve-membered ring pore network. The specific surface area of ​​HY zeolite can reach about 800m². 2 / g, with a micropore volume close to 0.3ml / g. Therefore, choosing HY zeolite as a carrier is beneficial to achieving a high loading of ZnO and forming a monolayer dispersed ZnO active phase on the inner and outer surfaces of HY zeolite, while maintaining the unobstructedness of its supercage structure and three-dimensional twelve-membered ring pore network; (3) Choosing to load ZnO on the HY zeolite carrier using easily fusible zinc salt through a solid zinc ion exchange process (dry loading process) can minimize the adverse effects of water on the loading of ZnO and monolayer dispersion.

[0044] The mechanism by which water affects ZnO loaded on HY zeolite support is as follows: From the perspective of zinc ions, the conventional solution ion exchange process for loading ZnO on HY zeolite support (wet loading process) has the following problems: On the one hand, after zinc salt dissolves in water, it forms zinc ions in hexahydrate ([Zn(H2O)6)). 2+ The zinc ion exists in the form of a hydrated zinc ion. Its disadvantages are that the hexahydrated zinc ion is not only much larger in volume than the bare zinc ion, but also has six water molecule ligands surrounding it in an octahedral spatial configuration. The former greatly reduces the number of zinc ions that can be accommodated in the zeolite channels, thus limiting the ZnO loading. The latter, due to the charge shielding effect of water molecules on zinc ions, hinders ion exchange between zinc ions and hydrogen protons on the inner and outer surfaces of the HY zeolite, making it unfavorable for monolayer dispersion of ZnO on the HY zeolite surface. From the perspective of the HY zeolite carrier, HY zeolite is a hydrophilic zeolite (a basic property of low silica-alumina ratio zeolites). When using conventional solution ion exchange processes, the HY zeolite carrier will also become a "hydrated" zeolite—not only will a relatively stable adsorbed water layer form on the inner and outer surfaces of the zeolite, but the exchangeable hydrogen protons on the inner and outer surfaces will also become hydrated protons. The former will greatly reduce the effective pore volume of the HY zeolite, thus further limiting the ZnO loading. The latter reduces the exchangeability of surface hydrogen protons, further hindering the ion exchange between zinc ions and hydrogen protons on the inner and outer surfaces of HY zeolite, which is detrimental to the monolayer dispersion of ZnO on the HY zeolite surface. Furthermore, when using conventional solution ion exchange processes, there is the problem of zinc salts readily hydrolyzing to form zinc hydroxide (Zn(OH)2) precipitates. In summary, if a large amount of ZnO is loaded onto the HY zeolite support using conventional solution ion exchange processes, it is difficult to obtain a monolayer supported zinc oxide (ZnO) catalyst on the HY zeolite support due to issues such as the formation of hydrated zinc ions, zinc salt hydrolysis to form precipitates, and the hydrophilicity of HY zeolite. Since a large number of zinc ions cannot easily enter the pores of HY zeolite and cannot disperse on the inner and outer surfaces, the inevitable consequence is that a large amount of ZnO will form particulate aggregates on the outer surface of the HY zeolite in the prepared supported catalyst. The small specific surface area of ​​ZnO granular packings results in low catalytic activity for the dehydration and nitrification reaction of diammonium adipate, which easily leads to the presence of a large number of intermediate and by-products in the reaction products, thereby reducing the yield of the target product, adiponitrile.

[0045] This invention selects easily fusible zinc salts to load ZnO on a HY zeolite support via a solid-state zinc ion exchange process (dry loading process). The main reasons for minimizing the adverse effects of water on the ZnO loading and monolayer dispersion are as follows: First, in the dry loading process, HY zeolite can be pre-dried and calcined to remove adsorbed water; second, during the dry loading of ZnO, the easily fusible zinc salts first melt into a liquid at an operating temperature above their melting point, and then the molten salt diffuses across the outer surface and pores of the zeolite support, completing the ion exchange reaction and achieving a large loading of zinc ions. Therefore, in this invention, when loading ZnO on a HY zeolite support using easily fusible zinc salts via a solid-state zinc ion exchange process (dry loading process), no additional water is added except for a small amount of crystal water introduced by the easily fusible zinc salts themselves. The zinc ions (ZnO) in the zinc salt... 2+ The ZnO atoms can diffuse on the exposed inner and outer surfaces of HY zeolite in a state closest to that of "naked" ions, and undergo ion exchange reactions with exchangeable hydrogen protons generated by the framework aluminum on the inner and outer surfaces. This is crucial for loading large amounts of ZnO onto the HY zeolite support and obtaining a monolayer dispersed ZnO active phase.

[0046] This invention will illustrate through specific embodiments that a monolayer dispersed supported zinc oxide (ZnO) catalyst on a HY zeolite support is a highly active and selective catalyst for the dehydration nitrification reaction of diammonium adipate to adiponitrile. To date, ZnO catalysts have not received sufficient attention in the application of diammonium adipate to adiponitrile. This may be because existing patents and published reports concerning the production of 6-hydroxyhexanoic acid from caprolactone involve non-supported bulk zinc oxide catalysts, as well as zinc oxide catalysts extruded using alumina as a binder, which have very small specific surface areas, making it difficult to fully utilize their intrinsic catalytic activity.

[0047] The technical solution of the present invention is as follows: A method for preparing a catalyst for the production of adiponitrile from adipic acid involves solid-state ion exchange treatment of a HY zeolite support with an easily fusible zinc salt to prepare a monolayer dispersed supported zinc oxide (ZnO) catalyst on the HY zeolite support. The specific steps are as follows: The first step involves preparing HY zeolite support using NaY zeolite as the parent material via a conventional ammonium exchange process. The prepared HY zeolite support must have a sodium content of ≤0.5 wt.% (based on Na2O) and a crystallinity retention of ≥90% based on NaY.

[0048] The NaY zeolite matrix refers to commercially available, conventionally hydrothermal synthesized ordinary NaY zeolite, with a typical SiO2 to Al2O3 molar ratio of 5-6. This invention does not limit the grain size of the NaY zeolite matrix; micron-sized NaY zeolite (grain size ≥ 1 micrometer), nano-sized NaY zeolite (grain size ≤ 100 nanometers), and small-grained NaY zeolite with grain sizes between these two can all be used to prepare the HY zeolite support of this invention. The NaY zeolite matrix used in this invention can be commercially available or synthesized hydrothermally. If you wish to synthesize NaY zeolite matrix hydrothermally, the following invention patents provide methods for reference: US3639099 (1972), CN85102733 (1989), CN1081425A (1994), CN1160676A (1997), CN1176848A (1998), CN1354134A (2002), CN1286723C (2003), CN1621349A (2003), CN1785807A (2004), CN1785808A (2004), CN1789125A (2004), CN 101254929A (2008). CN101767799A (2008), CN101177281 (2008), CN102050468A (2009), CN102050469A (2009), CN 101549874A (2009), CN101468802A (2009), CN102198950A (2010), CN101870478A (2010), CN103896303A (2012), CN104743572 (2013).

[0049] The preparation of HY zeolite from NaY zeolite matrix by ammonium exchange is common knowledge for those familiar with the field. Engineers skilled in the art can prepare HY zeolite carriers from NaY zeolite matrix based on their experience or conventional ammonium exchange methods described in the literature. The following conventional ammonium exchange methods are available for reference: CN111085251A (2018), CN109772432A (2019), CN114130424A (2020), CN114130420A (2020).

[0050] However, it should be noted that all sodium ions (Na+) in NaY zeolite... + Nearly 30% are located in the center of hexagonal prism cages, which are difficult to exchange (S I Only about 70% of sodium ions are located at the center of the six-membered ring within the easily exchangeable sodalite cage (S). II (position) and super cage (S) IIITherefore, when preparing HY zeolite from NaY zeolite through ammonium exchange, alternating ammonium exchange and calcination treatments are generally required to obtain HY zeolite with low sodium content. Those familiar with the field know that in practice, processes such as "two-times ammonium exchange and one-time calcination," "two-times ammonium exchange and two-times calcination," "three-times ammonium exchange and two-times calcination," "four-times ammonium exchange and two-times calcination," and "four-times ammonium exchange and three-times calcination" are commonly used to prepare HY zeolite with different sodium contents. In the aforementioned ion exchange processes for preparing HY zeolite, the intermediate calcination treatment aims to migrate the difficult-to-exchange sodium ions to the easily exchangeable cation sites.

[0051] Because HY zeolite is highly hydrophilic and has poor skeletal hydrothermal stability, the high-temperature conditions used during intermediate calcination and the resulting hydrothermal environment from the release of water vapor during the ammonium exchange process can easily lead to dealumination of the HY zeolite framework and damage to its crystal structure. Therefore, it is important to note that past experience in preparing fluidized bed catalytic cracking (FCC) catalysts for petroleum refining, which utilizes high-temperature hydrothermal environments to dealuminize HY zeolite, thereby passivating its acidity and obtaining structurally ultra-stable HY zeolite (USY), is not suitable for this invention. This is because in passivated HY zeolite, the number of exchangeable hydrogen protons on its inner and outer surfaces decreases with increasing passivation and dealumination, and the integrity of its pore structure also deteriorates with increasing passivation and dealumination, which is detrimental to the preparation of catalysts with high ZnO content and monolayer dispersion of ZnO support using solid-state ion exchange. Therefore, when preparing the HY zeolite support required by this invention using the ammonium exchange method, it is important to avoid exposing the HY zeolite to a high-temperature hydrothermal environment during the intermediate calcination stage of the ammonium exchange process, which could lead to crystal structure damage and framework dealuminization. Thoroughly drying the HY zeolite before calcination, and employing thin-layer calcination, low-temperature calcination, and timely removal of released water vapor during the calcination process are all simple and effective methods to avoid this.

[0052] Although HY zeolite can be obtained commercially, it is difficult for commercially available HY zeolite to meet the specific requirements of this invention regarding the integrity of the pore structure and the density of exchangeable hydrogen protons on the inner and outer surfaces of the HY zeolite support. Therefore, this invention recommends that engineers in the art obtain NaY zeolite matrix commercially and then prepare the HY zeolite support themselves using conventional ammonium exchange processes for NaY zeolite.

[0053] In preparing a low-sodium-content HY zeolite support in the laboratory using the ammonium exchange method, the present invention employs the following heat treatment steps: first, a thorough drying pretreatment, followed by calcination in flowing dry air. The suitable conditions for drying pretreatment are a temperature of 80-250℃ and a time of 1-96 hours. The preferred conditions for drying pretreatment are a temperature of 90-200℃ and a time of 3-72h; The preferred conditions for drying pretreatment are a temperature of 110-170℃ and a time of 6-24h; The suitable heat treatment temperature for calcination in flowing dry air is 350-600℃, the time is 0.5-24h, and the air flow rate (the volume of air passing over a unit volume of zeolite per unit time, in the form of ideal gas) is 1-2000h. -1 .

[0054] The preferred processing temperature is 400-550℃, the processing time is 1-20h, and the air flow rate (the volume of air passing over a unit volume of zeolite per unit time, in terms of ideal gas) is 5-1500h. -1 .

[0055] More preferably, the processing temperature is 450-500℃, the time is 1.5-15h, and the air flow rate (the volume of air passing over a unit volume of zeolite per unit time, in the form of an ideal gas) is in the range of 10-1000h. -1 .

[0056] After roasting, the HY zeolite carrier should be sealed and stored for later use to prevent moisture absorption. Avoid repeated roasting if moisture absorption occurs.

[0057] The second step involves solid-state zinc ion exchange treatment of the HY zeolite support with easily fusible zinc salt to prepare a monolayer dispersed ZnO catalyst supported on HY zeolite. The easily fusible zinc salt is one or a mixture of two or more of zinc acetate dihydrate, zinc nitrate hexahydrate, and zinc chloride. Zinc acetate dihydrate and zinc chloride are preferred. Zinc acetate dihydrate is more preferred.

[0058] The main steps are as follows: First, a measured amount of easily fusible zinc salt is mixed and ground with an appropriate amount of activated carbon powder until the zinc salt is finely ground and thoroughly mixed with the activated carbon powder. Then, the mixture of zinc salt and activated carbon powder is added to a calcined HY zeolite support, and grinding continues until the mixture of HY zeolite support and easily fusible zinc salt (referred to as the catalyst precursor) has a uniform color. Finally, the catalyst precursor is subjected to a programmed temperature calcination treatment in air to obtain the finished catalyst.

[0059] The specific procedures for the solid zinc ion exchange modification step in this invention are as follows: The amount of zinc salt used is expressed as the molar ratio of T to Zn. Here, T is the sum of the molar numbers of Si and Al in the HY zeolite carrier. The suitable range for the molar ratio of T to Zn is 0.5-6, the preferred range is 1-5, and the more preferred range is 2-4. When calcining the catalyst precursor in an air atmosphere using a programmed temperature rise process, the calcination process includes three isothermal sections: The suitable temperature range and treatment time range for the first constant temperature stage are 80-150℃ and 3-72h, respectively; the suitable temperature range and treatment time range for the second constant temperature stage are 200-300℃ and 3-48h, respectively; and the suitable temperature range and treatment time range for the third constant temperature stage are 400-650℃ and 3-1h, respectively. The preferred temperature range and processing time range for the first constant temperature stage are 90-140℃ and 3-48h, respectively; the preferred temperature range and processing time range for the second constant temperature stage are 220-280℃ and 3-24h, respectively; and the preferred temperature range and processing time range for the third constant temperature stage are 450-600℃ and 3-12h, respectively. The preferred temperature range and processing time range for the first constant temperature section are 100-130℃ and 3-24h, respectively; the preferred temperature range and processing time range for the second constant temperature section are 240-260℃ and 3-12h, respectively; and the preferred temperature range and processing time range for the third constant temperature section are 500-550℃ and 3-8h, respectively. The present invention does not limit the heating rate of the equipment to each constant temperature range, and engineers skilled in the art can choose according to the characteristics of the roasting furnace used.

[0060] The catalyst prepared by the above method is used to catalyze the liquid-phase dehydration and nitrification reaction of diammonium adipate to produce adiponitrile.

[0061] Engineers skilled in the art can perform the liquid-phase dehydration nitrification reaction of diammonium adipic acid salt using the catalyst provided by this invention, according to known methods. For example, the liquid-phase dehydration nitrification reaction can be performed using the catalyst provided by this invention, referring to the methods disclosed in CN106146345B (application date 2015), CN108821997B (application date 2018), and CN110790678B (application date 2019). In this invention, a hard glass reactor equipped with reflux and water separation devices is used in the laboratory to carry out the liquid-phase dehydration nitrification reaction according to the following steps: (1) Add diammonium adipate salt solid reactant to the reactor, and then add adiponitrile diluent (boiling point 295℃) to the reactor at a mass ratio of diammonium salt to adiponitrile of 1:2; (2) Heat the reactant to a temperature range of 220-250℃ under stirring at a heating rate not exceeding 2℃ / min to melt the diammonium salt; (3) Add the catalyst prepared by the method of this invention to the molten reactant under stirring, at a dosage of 5-30 wt.% (based on the amount of diammonium salt raw material); (4) Carry out the dehydration nitrification reaction within the liquid-phase dehydration nitrification reaction temperature range of 250-300℃. When the reaction temperature reaches the specified reaction temperature, the reaction timer is started (suitable reaction time 30-60 min). The temperature remains constant during the reaction; (5) After the reaction is completed, heating and stirring are stopped. After the reactor cools to room temperature, the raw material conversion rate is measured and the product composition is analyzed.

[0062] The adipic acid diammonium salt is prepared according to known methods. For example, an engineer skilled in the art can refer to the methods disclosed in Chinese invention patents CN108821997B (application date 2018) and CN110790678B (application date 2019) to prepare the required adipic acid diammonium salt. The present invention uses the method disclosed in CN110790678B to prepare adipic acid diammonium salt in the laboratory, specifically as follows: (1) At room temperature, a certain amount of adipic acid is weighed and added to an atmospheric pressure reactor, and then an equal amount of deionized water is added to it; (2) Under stirring, ammonia gas is introduced into the reactor to carry out a neutralization reaction. As the reaction proceeds, it can be observed that the adipic acid solid continuously dissolves in the water. When the adipic acid is completely dissolved, the pH value of the solution is detected with a pH meter. When the pH value stabilizes between 8.8 and 9.1, the neutralization reaction reaches its endpoint, and a large amount of white solid can be observed to precipitate in the solution. (3) Stop the ammonia gas supply and the neutralization reaction is complete; (4) Transfer the reactor to the refrigerator and cool it at 4°C for 12 h to crystallize. Then remove the reactor, filter and recover the diammonium adipic acid salt crystals, and wash the crystals with cold ethanol at 4°C. Recover the filtrate and washings for later use; (5) After drying the diammonium adipic acid salt crystals at room temperature, dry them in a vacuum drying oven for 3-4 h (50°C, vacuum degree -0.09 MPa), and seal them for later use.

[0063] The beneficial effects of this invention are: First, the HY zeolite-supported monolayer dispersed ZnO catalyst provided by this invention can replace liquid catalysts such as phosphoric acid (phosphate) or phosphate esters, as well as solid phosphoric acid catalysts, for catalyzing the liquid-phase ammoniation and dehydration reaction of adipic acid to produce adiponitrile, an important monomer used in the manufacture of Nylon-66 and certain specialty nylons. Replacing the liquid and solid phosphoric acid catalysts with the catalyst of this invention fundamentally avoids the problems of catalyst corrosion and scaling in the reactor during use. Second, the catalyst preparation method provided by this invention not only utilizes the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO supports, but also utilizes the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO supports. Simultaneously, it utilizes the solid zinc ion exchange process based on easily fusible zinc salts, which is beneficial for increasing the loading of ZnO on the HY zeolite support and for the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. This invention achieves its objective of loading a large amount of ZnO onto a HY zeolite support and obtaining a monolayer dispersed ZnO active phase by utilizing the above three advantageous factors. Attached Figure Description

[0064] Figure 1 This is the XRD diffraction pattern of the HY zeolite support; Figure 2 This is the XRD diffraction pattern of the HY zeolite-supported monolayer dispersed ZnO catalyst prepared in Example 1. Detailed Implementation

[0065] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0066] The effectiveness of this invention can be evaluated not only by the liquid-phase dehydration and nitrification reaction of the diammonium adipic acid salt, but also by characterizing the physicochemical properties of the prepared HY zeolite-supported monolayer dispersed ZnO catalyst.

[0067] The physicochemical properties include the ZnO loading, remaining surface exchangeable hydrogen protons, and the retention values ​​of specific surface area and micropore volume of the HY zeolite-supported monolayer dispersed ZnO catalyst. Additionally, during catalyst preparation, the residual sodium ion content and crystallinity retention of the HY zeolite support are also characterized.

[0068] The ZnO loading of the catalyst and the residual sodium ion content of the HY zeolite support can be determined by XRF; the number of exchangeable hydrogen protons on the surface of the support and catalyst can be characterized by pyridine adsorption infrared spectroscopy (Py-FT-IR); the specific surface area and micropore volume retention values ​​of the catalyst can be determined by nitrogen physical adsorption (based on the HY zeolite support); the crystallinity retention of the HY zeolite support is estimated by specific surface area data (based on the NaY zeolite matrix).

[0069] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0070] Example 1: This example illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO supports; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO supports; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention.

[0071] The first step involved preparing HY zeolite support using NaY zeolite as the parent material via a conventional ammonium exchange method. The NaY zeolite matrix used in this embodiment is a commercially available product with a sodium content (calculated as Na2O wt.%) of 12.36 wt.% and a SiO2 / Al2O3 molar ratio of 5.4.

[0072] The preparation of HY zeolite from NaY zeolite precursor via ammonium exchange employs a "four-exchange, three-calcination" process. This process involves adding a certain amount of NaY zeolite precursor to a 1.0 mol / L NH4Cl solution at a liquid-to-solid ratio of 10:1. Ammonium exchange is then performed at 90°C with continuous stirring for 1 hour. The exchange solution is then discarded, and the zeolite is washed with deionized water at a liquid-to-solid ratio of 10:1 at room temperature (25°C) for 1 hour. This process is repeated five times, designated as "one exchange." The zeolite solid after the first exchange is subjected to the same ion exchange and washing operation once more, designated as "two exchanges." The zeolite filter cake after the "two exchanges" is then dried overnight in an oven at 110°C, and subsequently calcined in a muffle furnace at 460°C for 6 hours in flowing dry air (air volumetric flow rate 800 h⁻¹). -1Thus, a "two-exchange-one-calcination" HY zeolite was obtained. This "two-exchange-one-calcination" HY zeolite underwent two more ion exchange treatments, followed by washing, drying, and calcination as described above after each ion exchange treatment, ultimately yielding a "four-exchange-three-calcination" HY zeolite support. The calcined HY zeolite support, determined by XRF, had a sodium content of 0.3 wt.%, and its crystallinity retention was 92% as determined by nitrogen physical adsorption. XRD characterization revealed characteristic diffraction peaks of its crystal structure, as shown below. Figure 1 As shown. The prepared HY zeolite-supported composite catalyst requires sealed storage for later use.

[0073] The second step involves solid-state zinc ion exchange treatment of the HY zeolite support with zinc acetate dihydrate to prepare a monolayer dispersed ZnO catalyst supported on the HY zeolite support. The main steps are as follows: First, according to the feeding amount of 100g HY zeolite carrier (SiO2 / Al2O3=5.4) and the T / Zn molar ratio of 3 (T=Si+Al), weigh out 127.10g of zinc acetate dihydrate (Zn(Ac)2). . 2H₂O (melting point 100℃) was mixed and ground with 50g of commercially available food-grade activated carbon powder (particle size: 200-325 mesh) to ensure the zinc salt was finely ground and thoroughly mixed with the activated carbon powder (the activated carbon powder was evenly distributed and fine). Then, the mixture of zinc salt and activated carbon powder was added to 100g of calcined HY zeolite carrier, and grinding continued until the mixture was uniform in color, yielding the catalyst precursor. Finally, the catalyst precursor was subjected to programmed temperature calcination in air to obtain the finished catalyst, named HY-ZnO-3-E1 (3 represents the T / Zn molar ratio, and E1 represents Example 1).

[0074] The programmed temperature calcination of the catalyst precursor in air atmosphere was carried out in a laboratory muffle furnace. The calcination process included three isothermal sections, as detailed below: The processing temperature and time in the first isothermal section were 110℃ and 12h, respectively; the processing temperature and time in the second isothermal section were 250℃ and 6h, respectively; and the processing temperature and time in the third isothermal section were 550℃ and 6h, respectively. The heating rate to each isothermal section was 3℃ / min.

[0075] The ZnO content of the HY-ZnO-3-E1 catalyst was determined to be approximately 32 wt.% using XRF (approximately 47 g ZnO per 100 g HY zeolite). The protonic acid content of the catalyst (corresponding to 1540 cm⁻¹) was determined using pyridine adsorption infrared spectroscopy. -1The absorption peak area indicates that all exchangeable hydrogen protons have been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that the specific surface area and micropore volume retention values ​​of the catalyst were both around 85% compared to HY zeolite. This indicates that the prepared HY zeolite-supported ZnO catalyst maintains good pore unobstructedness even with a support content as high as 32 wt.%, and its ZnO active phase conforms to monolayer dispersion characteristics. The XRD characterization of this sample yielded characteristic diffraction peaks of the HY crystal structure and the ZnO crystal phase, as shown in the figure. Figure 2 As shown.

[0076] Comparative Example 1: This example illustrates that if solution ion exchange is used instead of solid-state zinc ion exchange for zinc ion exchange treatment of the HY zeolite support, although HY zeolite has the characteristics of large ion exchange capacity and is beneficial for stabilizing zinc ions and ZnO loading, the ion exchange capacity between the HY zeolite support and zinc ions is weakened due to the combination of water and zinc ions (forming hydrated zinc ions), the combination of water and the inner and outer surfaces of HY zeolite (forming adsorbed water layer), and the combination of water and exchangeable hydrogen protons on the inner and outer surfaces of HY zeolite (forming hydrated hydrogen protons). This weakens the ability of HY zeolite to load and disperse ZnO on its inner and outer surfaces, making it difficult to load a large amount of ZnO on the HY zeolite support and obtain a monolayer dispersed ZnO active phase.

[0077] Example 1 was repeated, but in the second step, zinc acetate solution was used to perform solution ion exchange treatment on the HY zeolite support. The main procedure is as follows: First, according to the feed amount of 100g HY zeolite support (SiO2 / Al2O3=5.4) and the T / Zn molar ratio of 3 (T=Si+Al), 127.10g of zinc acetate dihydrate was weighed and dissolved in deionized water to prepare 1000ml of zinc acetate solution (Zn 2+ The ion concentration was 0.579 mol / L. 100 g of HY zeolite support was subjected to solution ion exchange treatment with the zinc acetate solution (liquid-to-solid ratio 10:1) at 90 °C with continuous stirring for 1 h. After the exchange, the zeolite was washed with deionized water at a liquid-to-solid ratio of 10:1 at room temperature (25 °C) for 1 h, repeated 5 times. The resulting zeolite filter cake was then dried overnight in an oven at 110 °C, and then calcined in air according to the same heating procedure. The resulting catalyst was named HY-ZnO-3-COM1 (COM1 represents Comparative Example 1).

[0078] The ZnO content of the HY-ZnO-3-COM1 catalyst was determined to be 8.5 wt.% using XRF. The proton acid content of the catalyst was determined by pyridine adsorption infrared spectroscopy, indicating that a large number of exchangeable hydrogen protons remained in the catalyst. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that the specific surface area and micropore volume retention values ​​of the catalyst were both around 83% compared to HY zeolite. This indicates that when solution ion exchange is used instead of solid-state zinc ion exchange for zinc ion exchange treatment of the HY zeolite support, the exchangeable hydrogen protons on the inner and outer surfaces of the HY zeolite are difficult to fully utilize. With the same zinc salt dosage, the prepared catalyst has a low ZnO content and poor monolayer dispersion, resulting in relatively low specific surface area and micropore volume retention values.

[0079] Comparative Example 2: This example illustrates that when preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention, the residual sodium ion content in HY zeolite is an important factor affecting the solid-state zinc ion exchange reaction. A higher residual sodium ion content is less conducive to loading a large amount of ZnO onto the HY zeolite support and obtaining a monolayer dispersed ZnO active phase.

[0080] Example 1 was repeated, but in the first step, during the preparation of the HY zeolite support using NaY zeolite as the parent material via conventional ammonium exchange, only the NaY zeolite underwent a "three-exchange, two-baking" ammonium exchange treatment. All other procedures were the same. The sodium content (calculated as Na2O) of the prepared HY zeolite support was determined to be 1.57 wt.% by XRF. The crystallinity retention of the HY zeolite was determined to be 94% by nitrogen physical adsorption. The finished catalyst obtained using this support was named HY-ZnO-3-COM2 (COM2 represents Comparative Example 2).

[0081] The ZnO content of the HY-ZnO-3-COM2 catalyst was determined to be approximately 32 wt.% using XRF. The protic acid content of the catalyst (corresponding to 1540 cm⁻¹) was determined using pyridine adsorption infrared spectroscopy. -1 The absorption peak area was measured, indicating that there were no exchangeable hydrogen protons in the catalyst. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that, compared to HY zeolite, the catalyst retained approximately 80% of both specific surface area and micropore volume.

[0082] A comparison with Example 1 clearly shows that the residual sodium ions in the HY zeolite support do not affect the ZnO loading capacity of the HY zeolite. However, due to the occupancy effect of sodium ions, the number of zinc ions occupying ion exchange sites in the loaded ZnO decreases. This leads to a decrease in the ability of the HY zeolite to disperse ZnO, and causes some of the loaded ZnO to easily aggregate into particles, rather than existing in a monolayer dispersion. When the prepared HY zeolite-supported ZnO catalyst contains too much particulate ZnO, it is detrimental to maintaining good pore flow under high ZnO loading.

[0083] Comparative Example 3: This example further illustrates that when preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention, the residual sodium ion content in HY zeolite is an important factor affecting the solid-state zinc ion exchange reaction. A higher residual sodium ion content is less conducive to loading a large amount of ZnO onto the HY zeolite support and obtaining a monolayer dispersed ZnO active phase.

[0084] Example 1 was repeated, but in the first step, during the preparation of the HY zeolite support using NaY zeolite as the parent material via conventional ammonium exchange, only the NaY zeolite underwent a "two-exchange-one-baking" ammonium exchange treatment. The sodium content (calculated as Na2O) of the prepared HY zeolite support was determined to be 3.60 wt.% by XRF. The crystallinity retention of the HY zeolite was determined to be 95% by nitrogen physical adsorption. The finished catalyst obtained using this support was named HY-ZnO-3-COM3 (COM3 represents Comparative Example 3).

[0085] The ZnO content of the HY-ZnO-3-COM3 catalyst was approximately 32 wt.% as determined by XRF. The proton acid content of the catalyst was determined by pyridine adsorption infrared spectroscopy, indicating the absence of exchangeable hydrogen protons. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that the specific surface area and micropore volume retention values ​​were both around 75% compared to HY zeolite. Further comparison with Example 1 and Comparative Example 2 reveals that the residual sodium ions in the HY zeolite support do not affect the ZnO loading capacity of HY zeolite; however, due to the occupancy effect of sodium ions, the number of zinc ions occupying ion exchange sites in the loaded ZnO decreases. This leads to a decrease in the ability of HY zeolite to disperse ZnO, and makes some of the loaded ZnO easily aggregate into particles, rather than existing in a monolayer dispersion. Excessive particulate ZnO in the prepared HY zeolite-supported ZnO catalyst is detrimental to maintaining good pore flow under high ZnO loading.

[0086] Example 2: This example illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and the ZnO support; and secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and the ZnO support. Furthermore, a solid-state zinc ion exchange process based on easily fusible zinc salts is used to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Notably, when using the solid-state zinc ion exchange process to load ZnO on the HY zeolite support, different easily fusible zinc salts can be used to provide zinc ions without affecting the benefits of this invention.

[0087] Example 1 was repeated, but in the second step of preparing the monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, zinc chloride was replaced with an easily fusible zinc salt (ZnCl2, melting point 293℃), and its dosage was 78.92 g. All other procedures remained unchanged. The resulting catalyst was named HY-ZnO-3-E2 (E2 represents Example 2).

[0088] Example 3: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and the ZnO support; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and the ZnO support; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Notably, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, different easily fusible zinc salts can be used to provide zinc ions without affecting the effectiveness of this invention.

[0089] Example 1 was repeated, but in the second step of preparing the monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, zinc nitrate hexahydrate was used as the easily fusible zinc salt (Zn(NO3)2·6H2O, melting point 36℃), and its dosage was 172.25g. All other procedures remained unchanged. The resulting catalyst was named HY-ZnO-3-E3 (E3 represents Example 3).

[0090] Example 4: This example illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO supports; and secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO supports. Furthermore, a solid-state zinc ion exchange process based on easily fusible zinc salts is used to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. In particular, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the temperature program of the calcined catalyst precursor can be changed within a certain range without affecting the benefits of this invention.

[0091] Repeat Example 1, but in the second step of preparing the monolayer dispersed ZnO catalyst supported on the HY zeolite support by solid-state zinc ion exchange treatment, the temperature rise procedure for calcining the catalyst precursor in air atmosphere is changed as follows: The processing temperature and time in the first isothermal stage were 100℃ and 24h, respectively; the processing temperature and time in the second isothermal stage were 260℃ and 3h, respectively; and the processing temperature and time in the third isothermal stage were 500℃ and 8h, respectively. The heating rate to each isothermal stage was 2℃ / min.

[0092] The processing temperature and time in the first isothermal section were 130℃ and 3h, respectively; the processing temperature and time in the second isothermal section were 240℃ and 12h, respectively; and the processing temperature and time in the third isothermal section were 550℃ and 3h, respectively. The heating rate to each isothermal section was 4℃ / min.

[0093] The finished catalysts obtained by the above two calcination processes are named HY-ZnO-3-E4-100-260-500 and HY-ZnO-3-E4-130-240-550, respectively.

[0094] Example 5: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO supports; and secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO supports. Furthermore, a solid-state zinc ion exchange process based on easily fusible zinc salts is used to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. In particular, when using the solid-state zinc ion exchange process to load ZnO on the HY zeolite support, the temperature program of the calcined catalyst precursor can be changed within a certain range without affecting the benefits of this invention.

[0095] Repeat Example 1, but in the second step of preparing the monolayer dispersed ZnO catalyst supported on the HY zeolite support by solid-state zinc ion exchange treatment, the temperature rise procedure for calcining the catalyst precursor in air atmosphere is changed as follows: The processing temperature and time in the first isothermal stage were 90℃ and 48h, respectively; the processing temperature and time in the second isothermal stage were 280℃ and 3h, respectively; and the processing temperature and time in the third isothermal stage were 450℃ and 12h, respectively. The heating rate to each isothermal stage was 3℃ / min.

[0096] The processing temperature and time in the first isothermal stage were 140℃ and 3h, respectively; the processing temperature and time in the second isothermal stage were 220℃ and 24h, respectively; and the processing temperature and time in the third isothermal stage were 600℃ and 3h, respectively. The heating rate to each isothermal stage was 2℃ / min.

[0097] The finished catalysts obtained by the above two calcination processes are named HY-ZnO-3-E5-90-280-450 and HY-ZnO-3-E5-140-220-600, respectively.

[0098] Example 6: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO supports; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO supports; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the temperature program of the calcined catalyst precursor can be changed within a certain range without affecting the benefits of this invention.

[0099] Repeat Example 1, but in the second step of preparing the monolayer dispersed ZnO catalyst supported on the HY zeolite support by solid-state zinc ion exchange treatment, the temperature rise procedure for calcining the catalyst precursor in air atmosphere is changed as follows: The processing temperature and time in the first isothermal stage were 80℃ and 72h, respectively; the processing temperature and time in the second isothermal stage were 300℃ and 3h, respectively; and the processing temperature and time in the third isothermal stage were 400℃ and 18h, respectively. The heating rate to each isothermal stage was 3℃ / min.

[0100] The processing temperature and time in the first isothermal section were 150℃ and 3h, respectively; the processing temperature and time in the second isothermal section were 200℃ and 48h, respectively; and the processing temperature and time in the third isothermal section were 650℃ and 3h, respectively. The heating rate to each isothermal section was 3℃ / min.

[0101] The finished catalysts obtained by the above two calcination processes are named HY-ZnO-3-E6-80-300-400 and HY-ZnO-3-E6-150-200-650, respectively.

[0102] Example 7: This example illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and the ZnO support; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and the ZnO support; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the ZnO loading on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO onto the HY zeolite support using the solid-state zinc ion exchange process, the ZnO loading can be varied within a certain range without affecting the benefits of this invention.

[0103] Example 1 was repeated, but in the second step of preparing a monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, the T / Zn molar ratio was changed to 2 (T = Si + Al). Specifically, 190.65 g of zinc acetate dihydrate was weighed as an easily fusible zinc salt to perform solid-state zinc ion exchange treatment on the HY zeolite support. Other operations remained unchanged. The resulting catalyst was named HY-ZnO-2-E7 (2 represents the T / Zn molar ratio). The ZnO content of the HY-ZnO-2-E7 catalyst was measured to be approximately 40 wt.% using XRF (approximately 71 g ZnO is contained in 100 g of HY zeolite). The proton acid content of the catalyst was detected by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that compared to HY zeolite, the specific surface area and micropore volume retention values ​​of the catalyst were both around 65%. This indicates that the prepared HY zeolite-supported ZnO catalyst still maintains good pore openness even with a loading of up to about 40 wt.%, and its ZnO active phase conforms to the characteristics of monolayer dispersion.

[0104] Example 8: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO loadings; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO loadings; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the loading of ZnO can be varied within a certain range without affecting the benefits of this invention.

[0105] Example 1 was repeated, but in the second step of preparing a monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, the T / Zn molar ratio was changed to 1 (T = Si + Al). Specifically, 381.3 g of zinc acetate dihydrate was weighed as an easily fusible zinc salt to perform solid-state zinc ion exchange treatment on the HY zeolite support. Other operations remained unchanged. The resulting catalyst was named HY-ZnO-1-E8 (1 represents the T / Zn molar ratio). The ZnO content of the HY-ZnO-1-E8 catalyst was measured to be approximately 48 wt.% using XRF (approximately 96 g ZnO is contained in 100 g of HY zeolite). The proton acid content of the catalyst was detected by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that the specific surface area and micropore volume retention values ​​of the catalyst were both around 50% compared to HY zeolite. This indicates that the prepared HY zeolite-supported ZnO catalyst still maintains unobstructed pores even with a loading of up to about 48 wt.%, and its ZnO active phase still exhibits monolayer dispersion characteristics.

[0106] Example 9: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO loadings; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO loadings; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the loading of ZnO can be varied within a certain range without affecting the benefits of this invention.

[0107] Example 1 was repeated, but in the second step of preparing a monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, the T / Zn molar ratio was changed to 0.5 (T = Si + Al). Specifically, 762.6 g of zinc acetate dihydrate was weighed as an easily fusible zinc salt to perform solid-state zinc ion exchange treatment on the HY zeolite support. Other operations remained unchanged. The resulting catalyst was named HY-ZnO-0.5-E9 (0.5 represents the T / Zn molar ratio). The ZnO content of the HY-ZnO-0.5-E9 catalyst was measured to be approximately 73 wt.% by XRF (approximately 280 g ZnO is contained in 100 g of HY zeolite). The proton acid content of the catalyst was detected by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that compared to HY zeolite, the specific surface area and micropore volume retention values ​​of the catalyst were both around 40%. This indicates that the prepared HY zeolite-supported ZnO catalyst still maintains a certain degree of pore openness even with a loading of up to about 73 wt.%, and its ZnO active phase still has some monolayer dispersion characteristics.

[0108] Example 10: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO loadings; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO loadings; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the loading of ZnO can be varied within a certain range without affecting the benefits of this invention.

[0109] Example 1 was repeated, but in the second step of preparing a monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, the T / Zn molar ratio was changed to 4 (T = Si + Al). Specifically, 95.3 g of zinc acetate dihydrate was weighed as an easily fusible zinc salt to perform solid-state zinc ion exchange treatment on the HY zeolite support. Other operations remained unchanged. The resulting catalyst was named HY-ZnO-4-E10 (4 representing the T / Zn molar ratio). The ZnO content of the HY-ZnO-4-E10 catalyst was measured to be approximately 26 wt.% using XRF. The proton acid content of the catalyst was detected by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that compared to HY zeolite, the specific surface area and micropore volume retention values ​​of the catalyst were both around 88%. This indicates that the prepared HY zeolite-supported ZnO catalyst still maintains good pore unobstructedness even with a loading of up to about 26 wt.%, and its ZnO active phase exhibits significant monolayer dispersion characteristics.

[0110] Example 11: This example further illustrates that the key to preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention lies in two aspects: firstly, utilizing the large ion exchange capacity of HY zeolite, which is beneficial for stabilizing zinc ions and ZnO loadings; secondly, utilizing the high porosity and large specific surface area of ​​the open-channel system of HY zeolite, which is beneficial for dispersing zinc ions and ZnO loadings; and thirdly, employing a solid-state zinc ion exchange process based on easily fusible zinc salts to increase the loading of ZnO on the HY zeolite support and promote the ion exchange reaction between zinc ions and exchangeable hydrogen protons located on the inner and outer surfaces of HY zeolite. The simultaneous utilization of these three advantageous factors is the main technical feature of the catalyst preparation method of this invention. Specifically, when loading ZnO on the HY zeolite support using the solid-state zinc ion exchange process, the loading of ZnO can be varied within a certain range without affecting the benefits of this invention.

[0111] Example 1 was repeated, but in the second step of preparing a monolayer dispersed ZnO catalyst supported on the HY zeolite support through solid-state zinc ion exchange treatment, the T / Zn molar ratio was changed to 6 (T = Si + Al). Specifically, 63.6 g of zinc acetate dihydrate was weighed as an easily fusible zinc salt to perform solid-state zinc ion exchange treatment on the HY zeolite support. Other operations remained unchanged. The resulting catalyst was named HY-ZnO-6-E11 (6 representing the T / Zn molar ratio). The ZnO content of the HY-ZnO-6-E11 catalyst was measured to be approximately 19 wt.% using XRF. The proton acid content of the catalyst was detected by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physical adsorption, showing that compared to HY zeolite, the specific surface area and micropore volume retention values ​​of the catalyst were both above 90%. This indicates that the prepared HY zeolite-supported ZnO catalyst still maintains good pore unobstructedness even with a loading of up to about 19 wt.%, and its ZnO active phase exhibits significant monolayer dispersion characteristics.

[0112] Comparative Example 4: This example illustrates that when preparing a monolayer dispersed ZnO catalyst supported on HY zeolite according to the catalyst preparation method provided by this invention, the degree of crystallinity retention in HY zeolite is also an important factor affecting the solid zinc ion exchange reaction, because amorphous silica-alumina does not have ion exchange capacity. In the calcination process of preparing HY zeolite from NaY zeolite using conventional ammonium exchange treatment, if the wet filter cake of NH4Y zeolite is not sufficiently dried before high-temperature calcination, and if flowing dry air is not used to promptly remove the NH3 and water vapor generated during the deammoniation process, or even if the undried NH4Y zeolite filter cake is calcined at high temperatures in a closed environment, the HY zeolite is highly susceptible to dealuminization and hyperstabilization under the action of high-temperature water vapor, leading to a decrease in crystallinity retention. The lower the crystallinity retention of HY zeolite, the less conducive it is to loading a large amount of ZnO on the HY zeolite support and obtaining a monolayer dispersed ZnO active phase.

[0113] Example 1 was repeated, but in the first step, when preparing the HY zeolite support using NaY zeolite as the parent material through a conventional ammonium exchange process of "four-times exchange and three-times roasting," the overnight drying process of the zeolite filter cake in a 110 °C oven was omitted after the fourth ammonium exchange. Instead, the wet filter cake was placed in a covered crucible and subjected to deep roasting in a muffle furnace at 550 °C for 6 hours. The muffle furnace was kept in a static air atmosphere during roasting. Other operations remained unchanged. The HY zeolite support was obtained after roasting. XRF analysis showed that the sodium content of the HY zeolite support was 0.3 wt.%, but the crystallinity retention of the HY zeolite, measured by nitrogen physical adsorption, decreased to 58%, indicating that the crystal structure of the HY zeolite had undergone hyperstableization under high temperature and in an atmosphere containing ammonia and water vapor. The HY zeolite support was subjected to solid-state zinc ion exchange treatment with zinc acetate dihydrate to prepare a ZnO catalyst supported on the HY zeolite support, named HY-ZnO-3-COM4 (COM4 represents Comparative Example 4).

[0114] The ZnO content of the HY-ZnO-3-COM4 catalyst was determined to be approximately 32 wt.% using XRF. The proton acid content of the catalyst was determined by pyridine adsorption infrared spectroscopy, indicating that all exchangeable hydrogen protons had been completely replaced by zinc ions. The texture properties of the catalyst were characterized by nitrogen physisorption, showing that compared to HY zeolite, the specific surface area and micropore volume retention values ​​of the catalyst were both around 35%. Compared with the results of Example 1, the prepared HY zeolite-supported ZnO catalyst exhibited poor pore unobstructedness and poor monolayer dispersion of the ZnO active phase.

[0115] Example 12: This example illustrates the catalytic performance of the catalysts prepared in the above examples and comparative examples for the liquid-phase dehydration and nitrification reaction of diammonium adipic acid salt.

[0116] The experimental procedure for the liquid-phase dehydration and nitrification reaction of diammonium adipate is as follows: (1) Add 10g of solid diammonium adipate to a 100ml hard glass reactor equipped with a reflux and water separator, and then add 20g of adiponitrile diluent (boiling point 295℃) to the reactor according to the mass ratio of diammonium adipate to adiponitrile 1:2; (2) Heat the reactants to 250℃ with stirring at a heating rate not exceeding 2℃ / min. Stir at this temperature until the diammonium adipate is completely melted and forms a homogeneous solution with adiponitrile; (3) Add the catalyst prepared in the specified example and comparative example to the reactant solution with stirring, the amount of which is 3g (30wt.% of diammonium adipate); (4) Then heat the reactant solution to 280℃ with a heating rate not exceeding 2℃ / min, and keep the temperature constant until the water flow in the water separator stops, and the reaction ends; (5) After the reaction ends, stop heating and stirring. After the reactor cooled to room temperature, it was sealed and allowed to stand for 4 hours to allow unconverted ammonium salts to precipitate. The mass of the precipitated stationary phase was measured to calculate the feed conversion rate. The liquid sample was analyzed by gas chromatography to determine the composition and calculate the adiponitrile product selectivity. The gas chromatograph used was a Shimadzu GC-2014C with an FID detector and an HP-5 column (Agilent 30m × 0.32mm × 0.25mm). The carrier gas flow rate was 1.0 ml / min, the detection temperature was 300 ℃, and the injection volume was 1 μL.

[0117] The main evaluation results are shown in Tables 1 to 6.

[0118] Table 1

[0119] Table 2

[0120] Table 3

[0121] Table 4

[0122] Table 5

[0123] Table 6

Claims

1. A method for preparing a catalyst for the production of adiponitrile from adipic acid, characterized in that, The preparation method involves solid-state ion exchange treatment of the HY zeolite support with easily fusible zinc salt to prepare a monolayer dispersed supported zinc oxide (ZnO) catalyst on the HY zeolite support. The specific steps are as follows: The first step involves preparing HY zeolite support using NaY zeolite as the parent material via an ammonium exchange process. The prepared HY zeolite support must have a sodium content of ≤0.5 wt.% (based on Na2O) and a crystallinity retention of ≥90% based on NaY. The second step involves solid-state zinc ion exchange treatment of the HY zeolite support with easily fusible zinc salt to prepare a monolayer dispersed ZnO catalyst supported on HY zeolite. First, the easily fusible zinc salt is mixed and ground with activated carbon powder to ensure that the zinc salt is finely ground and fully and evenly mixed with the activated carbon powder. Then, the mixture of zinc salt and activated carbon powder is added to the calcined HY zeolite carrier and ground again until the mixture of HY zeolite carrier and easily fusible zinc salt has a uniform color. This mixture of HY zeolite carrier and easily fusible zinc salt is called the catalyst precursor. Finally, the catalyst precursor is subjected to programmed temperature calcination in an air atmosphere to obtain the finished catalyst.

2. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 1, characterized in that, In the first step, the following heat treatment steps were used to prepare the HY zeolite support: first, a thorough drying pretreatment, followed by calcination in flowing dry air; the drying pretreatment conditions were a temperature of 80-250℃ and a time of 1-96h; the calcination heat treatment in flowing dry air was carried out at a temperature of 350-600℃ for 0.5-24h, with an air flow rate of 1-2000h. -1 .

3. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 2, characterized in that, The drying pretreatment conditions are: temperature 90-200℃, time 3-72h; the heat treatment of calcination in flowing dry air is: temperature 400-550℃, time 1-20h, air flow rate 5-1500 h⁻¹. -1 .

4. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 3, characterized in that, The drying pretreatment conditions are a temperature of 110-170℃ and a time of 6-24 hours; the heat treatment of calcination in flowing dry air is carried out at a temperature of 450-500℃ for a time range of 1.5-15 hours, with an air flow rate of 10-1000 h⁻¹. -1 .

5. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 1, characterized in that, In the second step, the easily fusible zinc salt is one or a mixture of two or more of zinc acetate dihydrate, zinc nitrate hexahydrate, and zinc chloride.

6. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 1, characterized in that, In the second step, The amount of zinc salt used is expressed as the molar ratio of T to Zn, where T is the sum of the molar numbers of Si and Al in the HY zeolite carrier, and the molar ratio of T to Zn is 0.5-6. When calcining the catalyst precursor in an air atmosphere using a programmed temperature rise process, the calcination process includes three isothermal sections: The temperature range and processing time range of the first constant temperature section are 80-150℃ and 3-72h, respectively; the temperature range and processing time range of the second constant temperature section are 200-300℃ and 3-48h, respectively; and the temperature range and processing time range of the third constant temperature section are 400-650℃ and 3-18h, respectively.

7. The method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 6, characterized in that, In the second step, The molar ratio of T to Zn is 1-5; The temperature range and processing time range of the first constant temperature section are 90-140℃ and 3-48h, respectively; the temperature range and processing time range of the second constant temperature section are 220-280℃ and 3-24h, respectively; and the temperature range and processing time range of the third constant temperature section are 450-600℃ and 3-12h, respectively.

8. A method for preparing a catalyst for the production of adiponitrile from adipic acid according to claim 7, characterized in that, In the second step, The molar ratio of T to Zn is 2-4; The temperature range and processing time range of the first constant temperature section are 100-130℃ and 3-24h, respectively; the temperature range and processing time range of the second constant temperature section are 240-260℃ and 3-12h, respectively; and the temperature range and processing time range of the third constant temperature section are 500-550℃ and 3-8h, respectively.

9. The catalyst prepared by the method according to any one of claims 1-8 is used to catalyze the liquid-phase dehydration and nitrification reaction of diammonium adipic acid salt to produce adiponitrile.

10. The application according to claim 9, characterized in that, The specific steps are as follows: (1) Add diammonium adipate salt solid reactant to the reactor, and then add adiponitrile diluent to the reactor according to the mass ratio of diammonium adipate to adiponitrile 1:2; (2) Under stirring, heat the reactant to a temperature range of 220-250℃ at a heating rate not exceeding 2℃ / min to melt the diammonium adipate; (3) Under stirring, add the catalyst to the molten reactant, the amount of which is 5-30wt.% based on the amount of diammonium adipate raw material; (4) Carry out the dehydration nitrification reaction in the liquid phase dehydration nitrification reaction temperature range of 250-300℃; when the reaction temperature reaches the specified reaction temperature, react for 30-60min; the temperature remains unchanged during the reaction; (5) after the reaction is completed, stop heating and stirring.

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