A process for the preparation of adiponitrile from epoxycyclohexane

Abstract

This invention uses cyclohexane oxide as a raw material and prepares high-quality adiponitrile through one-step liquid-phase catalytic ammonia oxidation in an oxygen-containing atmosphere and with ammonia, using a heterogeneous catalyst and auxiliary agents. By optimizing process parameters, this invention suppresses the formation of byproducts, improves the yield and efficiency of the method, and features a simple, clean, and environmentally friendly process. The raw materials are inexpensive and readily available, the reaction conditions are mild, post-processing is easy, and the product yield is high, demonstrating promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and relates to a process technology for preparing adiponitrile from cyclohexane oxide. Background Technology

[0002] Adiponitrile, also known as 1,4-dicyanobutane, abbreviated as ADN, is a colorless, oily liquid with a slightly sweet taste. It is toxic and corrosive, with a density of 962 g / cm³, a melting point of 1°C, and a boiling point of 295°C (1 atm). Adiponitrile reacts with hydrogen to form hexamethylenediamine, which then reacts with adipic acid under strict material ratios to form nylon 66 salt. Adiponitrile is a crucial intermediate in the production of the novel material nylon 66 and represents its most important and valuable industrial application. Furthermore, it has broad applications in electronics, light industry, and other organic synthesis fields.

[0003] There are several methods for synthesizing adiponitrile, the main ones being the adipic acid amination and dehydration method, the acrylonitrile electrolytic dimerization method, and the butadiene method. These production methods are all monopolized by foreign companies.

[0004] In 1930, DuPont in the United States achieved the industrial production of adiponitrile using the adipic acid process. Subsequently, DuPont developed technologies for synthesizing adiponitrile using the chlorination-cyanation process (a two-step process) of butadiene and the direct hydrocyanation process of butadiene. Monsanto in the United States also developed a technology for synthesizing adiponitrile through the hydrogenation dimerization of acrylonitrile.

[0005] The adipic acid process is technically mature and widely used. The general process involves reacting adipic acid with excess ammonia in the presence of phosphoric acid or its salts or esters as a catalyst at 270-290°C to dehydrate and produce adiponitrile. The main problems are: 1) The dehydration reaction is a stepwise process, resulting in numerous intermediate products; 2) At high temperatures, adipic acid undergoes decarboxylation, decomposition, and coking, generating byproducts that affect consumption per unit area; the coking also impacts the operating cycle.

[0006] The acrylonitrile hydrogenation dimerization process utilizes inexpensive and readily available propylene as its feedstock, exhibits high reaction selectivity, and minimizes pollution. However, it faces significant challenges: substantial process costs and high plant investment. Reducing investment is the only way to enhance the economic competitiveness of this method.

[0007] The direct hydrocyanation method for butadiene avoids the pollution problems associated with the electrolysis and removal of sodium chloride in the chlorination-cyanation method, making it the lowest-cost production method. However, this method is a batch reactor, with a complex process flow, high cost, and multiple uses of hydrocyanic acid, resulting in a high reaction risk. The synthesis of adiponitrile from butadiene mainly involves three steps: primary hydrocyanation, isomerization, and secondary hydrocyanation. The reaction equations are as follows:

[0008]

[0009] Therefore, developing clean and efficient adiponitrile preparation technology can not only improve the adiponitrile preparation technology to make it more environmentally friendly, but also has important significance for breaking the foreign technology monopoly.

[0010] This invention aims to provide a process flow for the catalytic ammoxidative cracking of cyclohexane oxide to prepare adiponitrile, producing high-quality adiponitrile under mild conditions. The process flow is simple, clean, and environmentally friendly; the raw materials are inexpensive and readily available; the reaction conditions are mild; post-processing is easy; and the product yield is high, demonstrating promising application prospects.

[0011] In summary, based on existing technical processes, this technical process is improved in the following aspects:

[0012] ---Using inexpensive, readily available, and non-toxic cyclohexane oxide as a raw material, the reaction conditions are mild, safe, and environmentally friendly.

[0013] ---The process of obtaining adiponitrile from cyclohexane oxide in one step is simple.

[0014] ---Implementation under heterogeneous catalysts, post-processing is easy

[0015] ---Adiponitrile has high conversion rate and selectivity, and high product yield.

[0016] ---This process differs from the batch reaction in the above technical routes, and can be continuously produced.

[0017] ---Purify the treatment flow and exhaust as much as possible

[0018] Purpose of the invention

[0019] In view of the prior art, the purpose of this invention is to provide a process flow for the catalytic ammonia oxidative cracking of cyclohexane oxide to prepare adiponitrile, and the method does not have the disadvantages of conventional methods.

[0020] The purpose of this invention is, in particular, to prepare adiponitrile using inexpensive, readily available, and non-toxic cyclohexane oxide as a raw material.

[0021] The purpose of this invention is to prepare adiponitrile under mild reaction conditions with a heterogeneous catalyst.

[0022] The purpose of this invention is to prepare adiponitrile under heterogeneous catalysts in batch reactors or continuous equipment, and in particular to provide a continuous process technology for the preparation of adiponitrile.

[0023] The purpose of this invention is also to reduce pollution problems in the production process of adiponitrile and prevent the reaction equipment from being corroded.

[0024] The present invention also aims to operate with the lowest possible disposal costs and the least possible waste gas emissions.

[0025] The implementation method of the present invention is as follows:

[0026] A method for preparing adiponitrile from cyclohexane oxide, using cyclohexane oxide and ammonia as raw materials and oxygen as an oxidant, to synthesize adiponitrile in the liquid phase at 70-150℃ under the conditions of a heterogeneous catalyst, auxiliaries and reaction solvent;

[0027] The heterogeneous catalyst is one or more of manganese oxide and / or supported manganese oxide;

[0028] The auxiliary agent is one or more of the following: ammonium fluoride, ammonium chloride, ammonium iodide, potassium fluoride, potassium chloride, potassium iodide, sodium fluoride, sodium chloride, and sodium iodide.

[0029] The specific steps of the above-mentioned method for preparing adiponitrile from cyclohexane oxide are as follows:

[0030] A) Mix cyclohexane oxide and a reaction solvent to obtain a reaction stream containing cyclohexane oxide / reaction solvent with a mass fraction of 1wt%-40wt%, preferably containing 3wt%-30wt% cyclohexane oxide.

[0031] B) The reaction stream obtained in step A) is added to the reactor along with oxygen-containing gas, ammonia, heterogeneous catalyst and auxiliary agent, and adiponitrile is prepared by direct ammoniation oxidation in the reactor.

[0032] In the above method for preparing adiponitrile from cyclohexane oxide, the reaction solvent is any one or more of toluene, acetonitrile, 1,2-dichloroethane, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), n-heptane, and tetrahydrofuran, with acetonitrile being the most preferred.

[0033] In the above method for preparing adiponitrile from cyclohexane oxide: the reactor used is preferably a slurry bed at 70-150℃ and 0.1-5.0MPa; the ammonia can be gaseous ammonia or liquid ammonia.

[0034] In the above-mentioned method for preparing adiponitrile from cyclohexane oxide: the molar ratio of cyclohexane oxide: oxygen: ammonia is 1:1.5-10:1.5-16, preferably 1:2-10:2-10; the mass ratio of heterogeneous catalyst to cyclohexane oxide in the system is 0.1-3.0:1, preferably 0.1-2.2:1; and the mass ratio of auxiliary agent to cyclohexane oxide in the system is 0.005-0.50:1, preferably 0.01-0.1:1.

[0035] The above-mentioned method for preparing adiponitrile from cyclohexane oxide is characterized in that: the heterogeneous catalyst for ammonia oxidation is manganese oxide and / or supported manganese oxide;

[0036] The molar ratio of manganese oxide to support Y in the supported manganese oxide is MnOx:Y = 10:(2-20), where x ranges from 1 to 3.5, preferably from 1.2 to 3.0; the support Y is one or more of Al2O3, SiO2, MgO, and CaCO3.

[0037] In the above method for preparing adiponitrile from cyclohexane oxide:

[0038] The adiponitrile production unit includes an ammonia liquefaction storage tank, an ammoniation oxidation reactor, a cooling tower, a membrane separation tower, an ammonia decarbonization tower, a circulating ammonia dehydration tower, an ammonia recovery liquefaction unit, a first distillation tower, a second distillation tower, a rectification tower, and an ammonia cooler.

[0039] External ammonia gas is supplied via an ammonia pipeline and a valve connected to the ammonia inlet of the ammonia liquefaction storage tank. A liquid ammonia delivery pipeline is located at the bottom of the ammonia liquefaction storage tank, and its outlet is connected to the ammonia oxidation reactor. The ammonia oxidation reactor also has an epoxy cyclohexane / reaction solvent inlet connected to the eighteenth pipeline, a catalyst and auxiliary agent inlet connected to the nineteenth pipeline, and an oxygen-containing atmosphere inlet connected to the twentieth pipeline on its side wall. The ammonia oxidation reactor has an ammonia-containing atmosphere outlet at the top and a reaction liquid outlet at the bottom. The ammonia-containing atmosphere outlet after ammonia oxidation is connected to a cooling tower via a first pipeline, and the ammonia oxidation reaction liquid outlet is connected to a first distillation tower via a second pipeline. The upper part of the cooling tower is connected to an ammonia decarbonation tower via a third pipeline, an ammonia cooler, and a fourth pipeline. The ammonia cooler is reconnected to the ammonia carbonate water inlet on the cooling tower via a reflux pipeline. The ammonia decarbonation tower is connected to a circulating ammonia dehydration tower via a fifth pipeline. The dehydration tower is connected to an ammonia recovery liquefaction tower via a sixth pipeline. The liquefied ammonia from the ammonia recovery liquefaction tower is reconnected to the ammonia inlet of the ammonia liquefaction storage tank.

[0040] A packing material is installed inside the cooling tower bottom. The lower part of the packing material is connected to the material outlet at the top of the distillation tower through the seventh pipe. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe. The upper part of the packing material is provided with a circulating liquid inlet connected to the ammonia cooler.

[0041] The solvent-water mixture obtained in the cooling tower is connected to the membrane separation tower through the eighth pipe at its lower part; the solvent-water mixture enters the membrane separation tower for separation, and the separated reaction solvent is back connected to the epoxy cyclohexane / solvent pipeline inlet through the ninth pipe at the upper part of the membrane separation tower for reuse; the separated water is discharged through the tenth pipe at the lower part of the membrane separation tower.

[0042] The refrigerant used in the circulating ammonia dehydration tower is the low temperature obtained by the evaporation of liquid ammonia to remove moisture. Since the evaporation of liquid ammonia can achieve a low temperature of 2-10℃, the partial pressure of water is further reduced, causing water to separate out. In order to further remove the water and oxygen generated in the reaction, ammonia is transported to the low temperature ammonia recovery liquefaction tower through the eighteenth pipeline (maintaining the temperature of -50℃ to -70℃), and nitrogen is replaced through the nineteenth pipeline to further remove water and oxygen from the liquid ammonia.

[0043] After the reaction in the ammoniation oxidation reactor, the outlet of the ammoniation reaction liquid is connected to the distillation column through the second pipe. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe connected to the top of the distillation column. The bottom of the distillation column is transported to the distillation column through the eleventh pipe 30. Low-boiling-point by-products are collected from the top of the distillation column through the twelfth pipe, high-boiling-point by-products are collected from the bottom through the thirteenth pipe, and crude adiponitrile collected from the middle is transported to the rectification column through the fourteenth pipe. Glutaronitrile, a co-product by-product, is collected from the top of the rectification column through the fifteenth pipe, high-boiling-point waste is collected from the bottom through the sixteenth pipe, and adiponitrile is collected from the middle through the seventeenth pipe.

[0044] In the above-mentioned process flow for preparing adiponitrile from cyclohexane oxide: the ammoniation oxidation reactor is a slurry bed reactor;

[0045] The separation and purification process of the reaction products includes the separation and purification of adiponitrile, the separation of by-products, the purification and reuse of solvent acetonitrile, and the decarbonization and dehydration recovery of ammonia.

[0046] In the above-mentioned process flow for preparing adiponitrile from cyclohexane oxide, both the ammonia oxidation reactor and the ammonia decarbonization tower are equipped with annular gas distributors.

[0047] In the above-mentioned process flow for preparing adiponitrile from cyclohexane oxide: the temperature of the ammonia recovery liquefaction tower is -50℃ to -70℃.

[0048] This invention suppresses the formation of byproducts by optimizing process parameters, thereby improving the yield and efficiency of the method. The process is simple, clean, and environmentally friendly. The raw materials are inexpensive and readily available, the reaction conditions are mild, the post-processing is easy, and the product yield is high, showing promising application prospects. Attached Figure Description

[0049] Figure 1 A schematic diagram of a process for preparing adiponitrile from cyclohexane oxide. Detailed Implementation

[0050] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions.

[0051] Figure 1This is a schematic diagram of a process for preparing adiponitrile from cyclohexane oxide according to the present invention, as shown below. Figure 1 The production process flow of adiponitrile shown includes an ammonia liquefaction storage tank 1, an ammoniation oxidation reactor 2, a cooling tower 3, a membrane separation tower 4, an ammonia decarbonization tower 5, a circulating ammonia dehydration tower 6, an ammonia recovery liquefaction unit 7, a first distillation tower 8, a second distillation tower 9, a rectification tower 10, and an ammonia cooler 40.

[0052] External ammonia gas is supplied via ammonia pipeline 11 and a valve connected to the ammonia inlet of ammonia liquefaction storage tank 1. A liquid ammonia delivery pipeline 12 is located at the bottom of ammonia liquefaction storage tank 1, and its outlet is connected to the ammonia oxidation reactor 2. The side wall of the ammonia oxidation reactor 2 also has an epoxy cyclohexane / reaction solvent inlet connected to the eighteenth pipeline 13, a catalyst and auxiliary agent inlet connected to the nineteenth pipeline 14, and an oxygen-containing atmosphere inlet connected to the twentieth pipeline 15. The ammonia oxidation reactor 2 has an ammonia-containing atmosphere outlet at the top and a reaction liquid outlet at the bottom. The ammonia-containing gas after ammonia oxidation... The atmosphere outlet is connected to the cooling tower 3 via the first pipe 16, and the outlet of the ammonia oxidation reaction liquid is connected to the first distillation tower 8 via the second pipe 28. The upper part of the cooling tower 3 is connected to the ammonia decarbonation tower 5 via the third pipe 17, the ammonia cooler 40, and the fourth pipe 19. The ammonia cooler 40 is connected back to the ammonia carbonate inlet on the cooling tower 3 via a return pipe 18. The ammonia decarbonation tower 5 is connected to the circulating ammonia dehydration tower 6 via the fifth pipe 23. The dehydration tower 6 is connected to the ammonia recovery liquefaction tower 7 via the sixth pipe 25. The liquefied ammonia in the ammonia recovery liquefaction tower 7 is connected back to the ammonia inlet of the ammonia liquefaction storage tank 1.

[0053] A packing section is installed inside the bottom of cooling tower 3. The lower part of this packing is connected to the material outlet at the top of distillation tower 8 via a seventh pipe 29. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe 29. The upper part of this packing is equipped with a circulating liquid inlet connected to an ammonia cooler 40. This packing section can effectively improve the cooling efficiency of the solvent / water solution and increase the solvent recycling rate.

[0054] The solvent-water mixture obtained in cooling tower 3 is connected to membrane separation tower 4 through its lower eighth pipe 20. The solvent-water mixture enters membrane separation tower 4 for separation, and the separated reaction solvent is reconnected to the epoxy cyclohexane / solvent inlet 13 via the ninth pipe 21 located at the top of membrane separation tower 4 for reuse; the separated water is discharged through the tenth pipe 22 located at the bottom of membrane separation tower 4.

[0055] In order to improve the utilization rate of gas and make the gas distribution more uniform, both the ammoniation oxidation reactor 2 and the ammonia decarbonization tower 5 are equipped with gas distributors (ammonia and oxygen distributors are respectively provided in the ammoniation oxidation reactor 2, and ammonia distributor is provided in the ammonia decarbonization tower 5). The ammoniation oxidation reactor is a slurry bed reactor.

[0056] The cooling medium used in the circulating ammonia dehydration tower 6 is the low temperature obtained from the evaporation of liquid ammonia to remove moisture. Since liquid ammonia evaporation can achieve a low temperature of 2–10°C, it further reduces the partial pressure of water, causing water to separate. To further remove the water and oxygen generated in the reaction, ammonia gas is transported via the eighteenth pipe 25 to the low-temperature ammonia recovery liquefaction tower 7 (maintaining a temperature of -50°C to -70°C), where it undergoes nitrogen replacement via the nineteenth pipe 37 to further remove water and oxygen from the liquid ammonia.

[0057] After the reaction in the ammonia oxidation reactor 2, the outlet of the ammonia oxidation reaction liquid through the second pipe 28 is connected to the distillation column 8. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe 29 connected to the upper part of the distillation column 8. The bottom of the distillation column 8 (containing a small amount of adipamide, polymer, low-boiling by-product, and adiponitrile mixture) is transported to the distillation column 9 through the eleventh pipe 30. In the upper part of the distillation column 9, the low-boiling by-product is collected through the twelfth pipe 31, and the high-boiling small amount of adipamide, polymer, etc. is collected through the thirteenth pipe 33. The crude adiponitrile product collected in the middle (containing adiponitrile and a small amount of glutaronitrile, high-boiling waste) is transported to the rectification column 10 through the fourteenth pipe 32. In the rectification column 10, the co-product glutaronitrile is collected through the fifteenth pipe 34 in the upper part, the high-boiling waste is collected through the sixteenth pipe 36 in the lower part, and the product adiponitrile is collected through the seventeenth pipe 35 in the middle.

[0058] Example 1

[0059] A 20% w% reaction stream of cyclohexane oxide / acetonitrile with a flow rate of 1000 kg / h is transported to the ammoniation reactor 2 via the eighteenth pipe 13. 20 kg of α-MnO2 catalyst and 7 kg of ammonium iodide additive are added via the nineteenth pipe 14. After thorough mixing, liquid ammonia is introduced at a rate of 300 kg / h (molar ratio of liquid ammonia to cyclohexane oxide is 8.7:1) through the liquid ammonia delivery pipe 12 connected to the reactor's ammonia inlet. Simultaneously, air is introduced at a rate of 2238 kg / h (molar ratio of oxygen in air to cyclohexane oxide is 8:1) through the twentieth pipe 15 connected to the reactor's oxygen atmosphere inlet. The oxygen and ammonia are uniformly dispersed in the system through a built-in gas distributor in the slurry bed ammoniation reactor 2, and the ammoniation reaction is carried out at 110℃ and 3.5 MPa. The outlet containing ammonia gas after ammonia oxidation is connected to cooling tower 3 via first pipe 16 to cool and recover acetonitrile solvent; the outlet of the ammonia oxidation reaction liquid is connected to distillation tower 8 via second pipe 28. The acetonitrile / water solution obtained after distillation in distillation tower 8 enters cooling tower 3 via seventh pipe 29 connected to the upper part of distillation tower 8. The bottom of distillation tower 8 (containing a small amount of adiponitrile, polymer, low-boiling byproduct, and glutaronitrile) is transported to distillation tower 9 via eleventh pipe 30. Low-boiling-point byproducts are collected from the upper part of distillation column 9 via pipe 12 (31), while high-boiling-point byproducts such as adipamide and polymers are collected from the lower part via pipe 13 (33). The crude adiponitrile product collected in the middle (containing adiponitrile and a small amount of glutaronitrile, high-boiling-point waste) is transported to distillation column 10 via pipe 14 (32). In distillation column 10, the co-product glutaronitrile is collected from the upper part via pipe 15 (34), high-boiling-point waste is collected from the lower part via pipe 16 (36), and the product adiponitrile is collected from the middle via pipe 17 (35). The flow rate is approximately 194 kg / h, and the GC purity is 99.5%. The yield of adiponitrile relative to cyclohexane oxide is 88%, and the CO2 yield is 8%.

[0060] The ammonia-containing oxidizing atmosphere, supplied to cooling tower 3 via the first pipe 16, and the acetonitrile / water solution obtained after distillation, supplied to cooling tower 3 via the seventh pipe 29 from distillation tower 8, are combined. The mixed atmosphere (ammonia, oxygen, carbon dioxide, water) and the acetonitrile / water mixture are separated in cooling tower 3. The bottom temperature of cooling tower 3 is controlled between -20℃ and -10℃. Cooling tower 3 has a packing section at its bottom; the lower part of this packing connects to the outlet of distillation tower 8 via the seventh pipe 29, and the upper part of this packing has a circulating liquid inlet connected to the ammonia cooler 40. This packing section effectively improves the cooling efficiency of the acetonitrile / water solution. The mixed atmosphere (ammonia, oxygen, carbon dioxide, water) is connected to the ammonia decarbonation tower 5 via the fourth pipe 19 from the ammonia cooler 40. The condensate at the bottom of the ammonia cooler 40 is mainly low-concentration ammonia water, which is further returned to the ammonia carbonate inlet on cooling tower 3 via a return pipe 18, with a return circulation flow rate of 40 kg / h. After cooling by cooler 40, the upper part mainly consists of a mixed atmosphere containing a small amount of ammonium carbonate water. The ammonium carbonate water enters the ammonia decarbonation tower 5, generating a mixed atmosphere of ammonia and oxygen, which is then transported via pipe 23 to the ammonia dehydration tower 6. The low temperature (2–10°C) obtained from liquid ammonia evaporation is used to reduce the partial pressure of water, causing water to precipitate and remove moisture. Simultaneously, the ammonia obtained from liquid ammonia evaporation and the dehydrated ammonia, along with oxygen, are transported via pipe 25 to the ammonia recovery liquefaction tower 7 (maintaining a temperature of -50°C to -70°C). Nitrogen replacement is then performed via pipe 37 to further remove water and oxygen from the liquid ammonia. During the replacement and deoxygenation process, the ammonia removal rate is less than 1 kg / h. The purified ammonia is then reconnected to the ammonia inlet of the ammonia liquefaction storage tank 1.

[0061] The acetonitrile-water mixture obtained in cooling tower 3 is connected to membrane separation tower 4 via its lower eighth pipe 20. The solvent-water mixture enters membrane separation tower 4 for separation. The separated acetonitrile is reconnected to the epoxy cyclohexane / acetonitrile pipeline inlet 13 via the ninth pipe 21 located at the top of membrane separation tower 4 for reuse. The separated water is discharged via the tenth pipe 22 located at the bottom of membrane separation tower 4. The acetonitrile recycling recovery rate is 96.5%, and the water separated from pipe 22 accounts for 98.2% of the total water in the system.

[0062] Example 2

[0063] A 20% w% reaction stream of cyclohexane oxide / acetonitrile with a flow rate of 1000 kg / h is transported to the ammoniation oxidation reactor 2 via the eighteenth pipe 13. 100 kg of β-MnO2 catalyst and 15 kg of potassium iodide additive are added via the nineteenth pipe 14. After stirring evenly, liquid ammonia is introduced at a rate of 100 kg / h through the liquid ammonia delivery pipe 12 connected to the ammonia inlet of the reactor (the molar ratio of liquid ammonia to cyclohexane oxide is 2.9:1). Simultaneously, air is introduced at a rate of 1120 kg / h through the twentieth pipe 15 connected to the oxygen atmosphere inlet of the reactor (the molar ratio of oxygen in the air to cyclohexane oxide is 4:1). The oxygen and ammonia are uniformly dispersed in the system through the gas distributor built into the slurry bed ammoniation oxidation reactor 2. The ammoniation oxidation reaction is carried out under the conditions of 90℃ and 5.0 MPa. The outlet containing ammonia gas after ammonia oxidation is connected to cooling tower 3 via first pipe 16 to cool and recover acetonitrile solvent; the outlet of the ammonia oxidation reaction liquid is connected to distillation tower 8 via second pipe 28. The acetonitrile / water solution obtained after distillation in distillation tower 8 enters cooling tower 3 via seventh pipe 29 connected to the upper part of distillation tower 8. The bottom of distillation tower 8 (containing a small amount of adiponitrile, polymer, low-boiling byproduct, and glutaronitrile) is transported to distillation tower 9 via eleventh pipe 30. Low-boiling-point byproducts are collected from the upper part of distillation column 9 via pipe 12 (31), while high-boiling-point byproducts such as adipamide and polymers are collected from the lower part via pipe 13 (33). The crude adiponitrile product collected in the middle (containing adiponitrile and a small amount of glutaronitrile, high-boiling-point waste) is transported to distillation column 10 via pipe 14 (32). In distillation column 10, the co-product glutaronitrile is collected from the upper part via pipe 15 (34), high-boiling-point waste is collected from the lower part via pipe 16 (36), and the product adiponitrile is collected from the middle via pipe 17 (35). The flow rate is approximately 181 kg / h, and the GC purity is 99.0%. The yield of adiponitrile relative to cyclohexane oxide is 82%, and the CO2 yield is 9%.

[0064] The ammonia-containing oxidizing atmosphere, supplied to cooling tower 3 via the first pipe 16, and the acetonitrile / water solution obtained after distillation, supplied to cooling tower 3 via the seventh pipe 29 from distillation tower 8, are combined. The mixed atmosphere (ammonia, oxygen, carbon dioxide, and water) and the acetonitrile / water mixture are separated in cooling tower 3. The bottom temperature of cooling tower 3 is controlled between -30℃ and -20℃. Cooling tower 3 has a packing section at its bottom; the lower part of this packing connects to the outlet of distillation tower 8 via the seventh pipe 29, and the upper part of the packing has a circulating liquid inlet connected to the ammonia cooler 40. This packing section effectively improves the cooling efficiency of the acetonitrile / water solution. The mixed atmosphere (ammonia, oxygen, carbon dioxide, and water) is connected to the ammonia decarbonation tower 5 via the fourth pipe 19 from the ammonia cooler 40. The condensate at the bottom of the ammonia cooler 40 is mainly low-concentration ammonia water, which is further returned to the ammonia carbonate inlet on cooling tower 3 via a return pipe 18, with a return circulation flow rate of 15 kg / h. After cooling by cooler 40, the upper part mainly contains a mixed atmosphere of ammonium carbonate water with a small amount of ammonium carbonate. The ammonium carbonate water enters the ammonia decarbonation tower 5, generating a mixed atmosphere of ammonia and oxygen, which is then transported to the ammonia dehydration tower 6 via the fifth pipe 23. The low temperature (2-10℃) obtained by evaporating liquid ammonia is used to reduce the partial pressure of water, causing water to precipitate and remove moisture. At the same time, the ammonia obtained by evaporating liquid ammonia and the dehydrated ammonia, along with oxygen, are transported together with the oxygen via the eighteenth pipe 25 to the ammonia recovery liquefaction tower 7 (maintaining a temperature of -50℃ to -70℃). Nitrogen replacement is then carried out via the nineteenth pipe 37 to further remove water and oxygen from the liquid ammonia. During the replacement and deoxygenation process, the ammonia removal rate is less than 0.6 kg / h. The purified ammonia is then reconnected to the ammonia inlet of the ammonia liquefaction storage tank 1.

[0065] The acetonitrile-water mixture obtained in cooling tower 3 is connected to membrane separation tower 4 via its lower eighth pipe 20. The solvent-water mixture enters membrane separation tower 4 for separation. The separated acetonitrile is reconnected to the epoxy cyclohexane / acetonitrile pipeline inlet 13 via the ninth pipe 21 located at the top of membrane separation tower 4 for reuse. The separated water is discharged via the tenth pipe 22 located at the bottom of membrane separation tower 4. The acetonitrile recycling recovery rate is 97.5%, and the water separated from pipe 22 accounts for 98.5% of the total water in the system.

[0066] Example 3

[0067] A 20% w% reaction stream of cyclohexane oxide / acetonitrile with a flow rate of 1000 kg / h is transported to the ammoniation reactor 2 via the eighteenth pipe 13. 400 kg of MnO2 / Al2O3 (molar ratio 1:2) catalyst and 5 kg of sodium fluoride additive are added via the nineteenth pipe 14. After thorough mixing, liquid ammonia is introduced at a rate of 69 kg / h (molar ratio of liquid ammonia to cyclohexane oxide is 2:1) via the liquid ammonia delivery pipe 12 connected to the reactor's ammonia inlet. Simultaneously, air is introduced at a rate of 1119 kg / h (molar ratio of oxygen in the air to cyclohexane oxide is 4:1) via the twentieth pipe 15 connected to the reactor's oxygen atmosphere inlet. The oxygen and ammonia are uniformly dispersed in the system through a built-in gas distributor in the slurry bed ammoniation reactor 2. The ammoniation reaction is carried out at 150℃ and 4.0 MPa. The outlet containing ammonia gas after ammonia oxidation is connected to cooling tower 3 via first pipe 16 to cool and recover acetonitrile solvent; the outlet of the ammonia oxidation reaction liquid is connected to distillation tower 8 via pipe 28. The acetonitrile / water solution obtained after distillation in distillation tower 8 enters cooling tower 3 via seventh pipe 29 connected to the upper part of distillation tower 8. The bottom of distillation tower 8 (containing a small amount of adiponitrile, polymer, low-boiling byproduct, and adiponitrile mixture) is transported to distillation tower 9 via eleventh pipe 30. Low-boiling-point byproducts are collected from the upper part of distillation column 9 via pipe 12 (31), while high-boiling-point byproducts such as adipamide and polymers are collected from the lower part via pipe 13 (33). The crude adiponitrile product collected in the middle (containing adiponitrile and a small amount of glutaronitrile, high-boiling-point waste) is transported to distillation column 10 via pipe 14 (32). In distillation column 10, the co-product glutaronitrile is collected from the upper part via pipe 15 (34), high-boiling-point waste is collected from the lower part via pipe 16 (36), and the product adiponitrile is collected from the middle via pipe 17 (35). The flow rate is approximately 207 kg / h, and the GC purity is 99.3%. The yield of adiponitrile relative to cyclohexane oxide is 94%, and the CO2 yield is 3%.

[0068] The ammonia-containing oxidizing atmosphere, supplied to cooling tower 3 via the first pipe 16, and the acetonitrile / water solution obtained after distillation, supplied to cooling tower 3 via the seventh pipe 29 from distillation tower 8, are combined. The mixed atmosphere (ammonia, oxygen, carbon dioxide, water) and the acetonitrile / water mixture are separated in cooling tower 3. The bottom temperature of cooling tower 3 is controlled between -30℃ and -25℃. Cooling tower 3 has a packing section at its bottom; the lower part of this packing connects to the outlet of distillation tower 8 via the seventh pipe 29, and the upper part of this packing has a circulating liquid inlet connected to the ammonia cooler 40. This packing section effectively improves the cooling efficiency of the acetonitrile / water solution. The mixed atmosphere (ammonia, oxygen, carbon dioxide, water) is connected to the ammonia decarbonation tower 5 via the fourth pipe 19 from the ammonia cooler 40. The condensate at the bottom of the ammonia cooler 40 is mainly low-concentration ammonia water, which is further returned to the ammonia carbonate inlet on cooling tower 3 via a return pipe 18, with a return circulation flow rate of 10 kg / h. After cooling by cooler 40, the upper part mainly consists of a mixed atmosphere containing a small amount of ammonium carbonate water. The ammonium carbonate water enters the ammonia decarbonation tower 5, generating a mixed atmosphere of ammonia and oxygen, which is then transported via pipe 23 to the ammonia dehydration tower 6. The low temperature (2–10°C) obtained from liquid ammonia evaporation is used to reduce the partial pressure of water, causing water to precipitate and remove moisture. Simultaneously, the ammonia obtained from liquid ammonia evaporation and the dehydrated ammonia, along with oxygen, are transported via pipe 25 to the ammonia recovery liquefaction tower 7 (maintaining a temperature of -50°C to -70°C). Nitrogen replacement is then performed via pipe 37 to further remove water and oxygen from the liquid ammonia. During the replacement and deoxygenation process, the ammonia removal rate is less than 0.5 kg / h. The purified ammonia is then reconnected to the ammonia inlet of the ammonia liquefaction storage tank 1.

[0069] The acetonitrile-water mixture obtained in cooling tower 3 is connected to membrane separation tower 4 via its lower eighth pipe 20. The solvent-water mixture enters membrane separation tower 4 for separation. The separated acetonitrile is reconnected to the epoxy cyclohexane / acetonitrile pipeline inlet 13 via the ninth pipe 21 located at the top of membrane separation tower 4 for reuse. The separated water is discharged via the tenth pipe 22 located at the bottom of membrane separation tower 4. The acetonitrile recycling recovery rate is 97.5%, and the water separated by pipe 22 accounts for 97.2% of the total water in the system.

[0070] Example 4

[0071] A 30% w% reaction stream of cyclohexane oxide / acetonitrile with a flow rate of 1000 kg / h is transported to the ammoniation reactor 2 via the eighteenth pipe 13. 300 kg of MnO2 / SiO2 (molar ratio 1:1) catalyst and 5 kg of ammonium chloride additive are added via the nineteenth pipe 14. After thorough mixing, liquid ammonia is introduced at a rate of 520 kg / h (molar ratio of liquid ammonia to cyclohexane oxide is 10:1) through the liquid ammonia delivery pipe 12 connected to the reactor's ammonia inlet. Simultaneously, air is introduced at a rate of 2072 kg / h (molar ratio of oxygen in the air to cyclohexane oxide is 5:1) through the twentieth pipe 15 connected to the reactor's oxygen atmosphere inlet. The oxygen and ammonia are uniformly dispersed in the system through a built-in gas distributor in the slurry bed ammoniation reactor 2. The ammoniation reaction is carried out at 120℃ and 3.5 MPa. The outlet containing ammonia gas after ammonia oxidation is connected to cooling tower 3 via first pipe 16 to cool and recover acetonitrile solvent; the outlet of the ammonia oxidation reaction liquid is connected to distillation tower 8 via second pipe 28. The acetonitrile / water solution obtained after distillation in distillation tower 8 enters cooling tower 3 via seventh pipe 29 connected to the upper part of distillation tower 8. The bottom of distillation tower 8 (containing a small amount of adiponitrile, polymer, low-boiling byproduct, and glutaronitrile) is transported to distillation tower 9 via eleventh pipe 30. Low-boiling-point byproducts are collected from the upper part of distillation column 9 via pipe 12 (31), while high-boiling-point byproducts such as adipamide and polymers are collected from the lower part via pipe 13 (33). The crude adiponitrile product collected in the middle (containing adiponitrile and a small amount of glutaronitrile, high-boiling-point waste) is transported to distillation column 10 via pipe 14 (32). In distillation column 10, the co-product glutaronitrile is collected from the upper part via pipe 15 (34), high-boiling-point waste is collected from the lower part via pipe 16 (36), and the product adiponitrile is collected from the middle via pipe 17 (35). The flow rate is approximately 298 kg / h, and the GC purity is 99.4%. The yield of adiponitrile relative to cyclohexane oxide is 90%, and the CO2 yield is 3%.

[0072] The ammonia-containing oxidizing atmosphere, supplied to cooling tower 3 via the first pipe 16, and the acetonitrile / water solution obtained after distillation, supplied to cooling tower 3 via the seventh pipe 29 from distillation tower 8, are combined. The mixed atmosphere (ammonia, oxygen, carbon dioxide, and water) and the acetonitrile / water mixture are separated in cooling tower 3. The bottom temperature of cooling tower 3 is controlled between -30℃ and -25℃. Cooling tower 3 has a packing section at its bottom; the lower part of this packing connects to the outlet of distillation tower 8 via the seventh pipe 29, and the upper part of this packing has a circulating liquid inlet connected to the ammonia cooler 40. This packing section effectively improves the cooling efficiency of the acetonitrile / water solution. The mixed atmosphere (ammonia, oxygen, carbon dioxide, and water) is connected to the ammonia decarbonation tower 5 via the fourth pipe 19 from the ammonia cooler 40. The condensate at the bottom of the ammonia cooler 40 is mainly low-concentration ammonia water, which is further returned to the ammonia carbonate inlet on cooling tower 3 via a return pipe 18, with a return circulation flow rate of 80 kg / h. After cooling by cooler 40, the upper part mainly consists of a mixed atmosphere containing a small amount of ammonium carbonate water. The ammonium carbonate water enters the ammonia decarbonation tower 5, generating a mixed atmosphere of ammonia and oxygen, which is then transported via pipe 23 to the ammonia dehydration tower 6. The low temperature (2–10°C) obtained from liquid ammonia evaporation is used to reduce the partial pressure of water, causing water to precipitate and remove moisture. Simultaneously, the ammonia obtained from liquid ammonia evaporation and the dehydrated ammonia, along with oxygen, are transported via pipe 25 to the ammonia recovery liquefaction tower 7 (maintaining a temperature of -50°C to -70°C). Nitrogen replacement is then performed via pipe 37 to further remove water and oxygen from the liquid ammonia. During the replacement and deoxygenation process, the ammonia removal rate is less than 4 kg / h. The purified ammonia is then reconnected to the ammonia inlet of the ammonia liquefaction storage tank 1.

[0073] The acetonitrile-water mixture obtained in cooling tower 3 is connected to membrane separation tower 4 via its lower eighth pipe 20. The solvent-water mixture enters membrane separation tower 4 for separation. The separated acetonitrile is reconnected to the epoxy cyclohexane / acetonitrile pipeline inlet 13 via the ninth pipe 21 located at the top of membrane separation tower 4 for reuse. The separated water is discharged via the tenth pipe 22 located at the bottom of membrane separation tower 4. The acetonitrile recycling recovery rate is 94.5%, and the water separated by pipe 22 accounts for 96.2% of the total water in the system.

[0074] In summary, the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art can make various changes in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing adiponitrile from cyclohexane oxide, characterized in that, Adiponitrile was synthesized in the liquid phase at 70-150 °C using cyclohexane oxide and ammonia as raw materials and oxygen as oxidant, under the conditions of heterogeneous catalyst, auxiliaries and reaction solvent. The heterogeneous catalyst is one or more of manganese oxide and / or supported manganese oxide; The auxiliary agent is one or more of the following: ammonium fluoride, ammonium chloride, ammonium iodide, potassium fluoride, potassium chloride, potassium iodide, sodium fluoride, sodium chloride, and sodium iodide.

2. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that, The specific steps are as follows: A) Mix cyclohexane oxide and a reaction solvent to obtain a reaction stream with a cyclohexane oxide mass fraction of 1 wt% to 40 wt% / reaction solvent. B) The reaction stream obtained in step A) is added to the reactor along with oxygen-containing gas, ammonia, heterogeneous catalyst and auxiliary agent, and adiponitrile is prepared by direct ammoniation oxidation in the reactor.

3. The method for preparing adiponitrile from cyclohexane oxide according to claim 2, characterized in that, A reaction stream containing cyclohexane oxide at a mass fraction of 3 w%-30 w% wt% was obtained in the reaction solvent.

4. The method for preparing adiponitrile from cyclohexane oxide according to claim 1 or 2, characterized in that, The reaction solvent is any one or more of toluene, acetonitrile, 1,2-dichloroethane, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), n-heptane, and tetrahydrofuran.

5. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that: The reactor used is a slurry bed at 70-150 ℃ and 0.1-5.0 MPa; the ammonia can be gaseous ammonia or liquid ammonia.

6. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that: The molar ratio of cyclohexane oxide:oxygen:ammonia is 1:1.5-10:1.5-16; The mass ratio of heterogeneous catalyst to cyclohexane oxide in the system is 0.1-3.0:1; The mass ratio of the additive to cyclohexane oxide in the system is 0.005-0.50:

1.

7. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that: The molar ratio of cyclohexane oxide: oxygen: ammonia is 1:2-10:2-10; The mass ratio of heterogeneous catalyst to cyclohexane oxide in the system is 0.1-2.2:1; The mass ratio of the additive to cyclohexane oxide in the system is 0.01-0.1:

1.

8. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that: The heterogeneous catalysts for ammonia oxidation are manganese oxides and / or supported manganese oxides; The molar ratio of manganese oxide to support Y in the supported manganese oxide is MnOx:Y=10:(2-20), where x ranges from 1 to 3.5; the support Y is one or more of Al2O3, SiO2, MgO, and CaCO3.

9. The method for preparing adiponitrile from cyclohexane oxide according to claim 1, characterized in that: The adiponitrile production unit includes an ammonia liquefaction storage tank, an ammoniation oxidation reactor, a cooling tower, a membrane separation tower, an ammonia decarbonization tower, a circulating ammonia dehydration tower, an ammonia recovery liquefaction unit, a first distillation tower, a second distillation tower, a rectification tower, and an ammonia cooler. External ammonia gas is supplied via an ammonia pipeline and a valve connected to the ammonia inlet of the ammonia liquefaction storage tank. A liquid ammonia delivery pipeline is located at the bottom of the ammonia liquefaction storage tank, and its outlet is connected to the ammonia oxidation reactor. The ammonia oxidation reactor also has an epoxy cyclohexane / reaction solvent inlet connected to the eighteenth pipeline, a catalyst and auxiliary agent inlet connected to the nineteenth pipeline, and an oxygen-containing atmosphere inlet connected to the twentieth pipeline on its side wall. The ammonia oxidation reactor has an ammonia-containing atmosphere outlet at the top and a reaction liquid outlet at the bottom. The ammonia-containing atmosphere outlet after ammonia oxidation is connected to a cooling tower via a first pipeline, and the ammonia oxidation reaction liquid outlet is connected to a first distillation tower via a second pipeline. The upper part of the cooling tower is connected to an ammonia decarbonation tower via a third pipeline, an ammonia cooler, and a fourth pipeline. The ammonia cooler is reconnected to the ammonia carbonate water inlet on the cooling tower via a reflux pipeline. The ammonia decarbonation tower is connected to a circulating ammonia dehydration tower via a fifth pipeline. The dehydration tower is connected to an ammonia recovery liquefaction tower via a sixth pipeline. The liquefied ammonia from the ammonia recovery liquefaction tower is reconnected to the ammonia inlet of the ammonia liquefaction storage tank. A packing material is installed inside the cooling tower bottom. The lower part of the packing material is connected to the material outlet at the top of the distillation tower through the seventh pipe. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe. The upper part of the packing material is provided with a circulating liquid inlet connected to the ammonia cooler. The solvent-water mixture obtained in the cooling tower is connected to the membrane separation tower through the eighth pipe at its lower part; the solvent-water mixture enters the membrane separation tower for separation, and the separated reaction solvent is back connected to the epoxy cyclohexane / solvent pipeline inlet through the ninth pipe at the upper part of the membrane separation tower for reuse; the separated water is discharged through the tenth pipe at the lower part of the membrane separation tower. The refrigerant used in the circulating ammonia dehydration tower is the low temperature obtained by the evaporation of liquid ammonia to remove moisture. Since the liquid ammonia evaporation achieves a low temperature of 2-10 ℃, it further reduces the partial pressure of water, causing water to separate out. In order to further remove the water and oxygen generated in the reaction, ammonia is transported to the low temperature ammonia recovery liquefaction tower through the eighteenth pipeline, where the temperature is maintained at -50 ℃ to -70 ℃. Nitrogen is then replaced through the nineteenth pipeline to further remove water and oxygen from the liquid ammonia. After the reaction in the ammoniation oxidation reactor, the outlet of the ammoniation reaction liquid is connected to the distillation column through the second pipe. The solvent / water solution obtained after distillation enters the cooling tower through the seventh pipe connected to the top of the distillation column. The bottom of the distillation column is transported to the distillation column through the eleventh pipe 30. Low-boiling-point by-products are collected from the top of the distillation column through the twelfth pipe, high-boiling-point by-products are collected from the bottom through the thirteenth pipe, and crude adiponitrile collected from the middle is transported to the rectification column through the fourteenth pipe. Glutaronitrile, a co-product by-product, is collected from the top of the rectification column through the fifteenth pipe, high-boiling-point waste is collected from the bottom through the sixteenth pipe, and adiponitrile is collected from the middle through the seventeenth pipe.

10. The method for preparing adiponitrile from cyclohexane oxide according to claim 9, characterized in that: The ammoniation oxidation reactor is a slurry bed reactor; The separation and purification process of the reaction products includes the separation and purification of adiponitrile, the separation of by-products, the purification and reuse of solvent acetonitrile, and the decarbonization and dehydration recovery of ammonia.

11. The method for preparing adiponitrile from cyclohexane oxide according to claim 9, characterized in that: Both the ammoniation oxidation reactor and the ammonia decarbonization tower are equipped with annular gas distributors.

12. The method for preparing adiponitrile from cyclohexane oxide according to claim 9, characterized in that: The temperature of the ammonia recovery liquefaction tower is -50 ℃ to -70 ℃.

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