Process for the preparation of adiponitrile by cyclohexene ammoxidation

Abstract

The application belongs to the technical field of catalytic selective ammoxidation, and discloses a method for preparing adiponitrile through cyclohexene ammoxidation. A designed and synthesized inexpensive Mn-Fe oxide is used as a catalyst, and under the conditions of adding an additive in an oxygen and ammonia atmosphere, the efficient catalysis of cyclohexene oxygen ammoxidation for preparing adiponitrile is realized, and the yield can be as high as 86.2%. The innovation of the process lies in the adoption of a brand-new heterogeneous catalytic ammoxidation technical route, and the process has the outstanding advantages of simple operation, low catalyst cost, high adiponitrile yield, environmental friendliness and the like, and is suitable for industrialized production application.

Description

Technical Field

[0001] This invention belongs to the field of selective ammonia oxidation catalyst preparation and application technology, specifically relating to a method for designing ammonia oxidation of cyclohexene to prepare adiponitrile. Background Technology

[0002] Adiponitrile is a key chemical raw material with broad application prospects in multiple fields. It is not only an important precursor for the production of nylon 66 salt, but also used as a stabilizer in the manufacture of nylon fabrics, engineering plastics, and the textile and paper industries. From everyday clothing fabrics to high-end manufacturing sectors such as new energy vehicles, adiponitrile plays an irreplaceable role, demonstrating its diversified application value.

[0003] CN119707741A discloses a method for synthesizing adiponitrile by selective ammoxidation of cyclohexane oxide. The industrial production of cyclohexane oxide primarily relies on the cyclohexene oxidation method, which involves epoxidizing cyclohexene with an oxidant. Directly using cyclohexene as a raw material and employing a one-step ammoxidation method to synthesize adiponitrile simplifies the process, avoids the synthesis and separation of intermediates, and thus offers advantages in atom economy, production efficiency, and cost.

[0004] Against this backdrop, this technology uses cyclohexene as a raw material and employs a Mn-Fe oxide catalyst to synthesize adiponitrile in an ammonia and oxygen atmosphere, achieving a yield of 86.2%. Compared with existing processes, this method has significant advantages: it uses inexpensive and recyclable catalysts, operates under mild reaction conditions, avoids the use of highly toxic raw materials, and eliminates problems such as iodine pollution. Summary of the Invention

[0005] This invention provides a method for preparing adiponitrile by ammoxidation of cyclohexene.

[0006] The technical solution adopted in this invention is:

[0007] The method for preparing adiponitrile by ammoxidation of cyclohexene involves adding cyclohexene, Mn-Fe oxide catalyst, additives and reaction solvent into a high-pressure reactor, filling it with ammonia and oxygen source gas, and then heating it to a certain temperature (such as placing it in an oil bath) and reacting it for a certain time to obtain the adiponitrile product.

[0008] The preparation method of the Mn-Fe oxide used in the above scheme is as follows: First, a solid mixture of MnSO4, FeSO4, and a grinding aid (at least two or more of vitamin C, glucose, xylose, malic acid, citric acid, lauric acid, palmitic acid, and benzoic acid, preferably citric acid) is ground for 5-30 min (preferably 15-30 min, most preferably 25-30 min) until uniformly mixed. Then, it is calcined in a muffle furnace under an air atmosphere at 200-500 ℃ (preferably 200-300 ℃, most preferably 200-250 ℃) for 2-4 h (preferably 2-3 h, most preferably 2-2.5 h) to obtain the catalyst Mn. a Fe b O x -zG (G represents grinding aid), the catalyst Mn a Fe b O x -zG is used for the one-step ammoxidation of cyclohexene to prepare adiponitrile. Where a / b represents the molar ratio of Mn / Fe in the catalyst, which is 0.6-1.55 (preferably 1-1.5, most preferably 1.2-1.5); z represents the molar ratio of the grinding aid added during grinding to the total metal content, i.e., z / (Mn+Fe), which is 0.1-0.4 (preferably 0.25-0.35, most preferably 0.3-0.32).

[0009] In the above scheme, the additive used is at least one or more of N-hydroxysuccinimide (NHS), 4-nitrophenol, 3-mercaptopropionic acid (MPA), and N-iodosuccinimide (NIS), preferably NHS.

[0010] In the above scheme, the reaction solvent used is at least one or more of 1,4-dioxane, acetonitrile, tert-amyl alcohol, DMSO, DMF, n-heptane, and tetrahydrofuran; preferably acetonitrile.

[0011] In the above scheme, the oxygen source gas used is pure oxygen or air, preferably pure oxygen.

[0012] In the above scheme, the molar ratio of the amount of additive added to the amount of cyclohexene fed is 0.15-0.2, preferably 0.18-0.2, and most preferably 0.19-0.2.

[0013] In the above scheme, for every 2 mmol of cyclohexene, the amount of catalyst used is 40-80 mg, preferably 50-60 mg, and most preferably 55-60 mg.

[0014] In the above scheme, for every 2 mmol of cyclohexene, the solvent volume is 4-6 mL, preferably 4-5 mL, and most preferably 4-4.5 mL.

[0015] In the above scheme, the gas pressures of the ammonia and oxygen source gases are each 0.5-0.9 MPa, preferably 0.5-0.7 MPa, and most preferably 0.5-0.6 MPa.

[0016] In the above scheme, the reaction temperature is 75-130 ℃, preferably 80-120 ℃, and most preferably 100-110 ℃.

[0017] In the above scheme, the reaction time is 3-12 h, preferably 5-8 h, and most preferably 5-6 h.

[0018] In the above scheme, the catalyst can be recycled after simple separation and washing after the reaction, and can be recycled at least 20 times without significant reduction in activity.

[0019] The above-mentioned method can be scaled up to kilogram-scale production. Under standard reaction conditions, the selectivity of adiponitrile can reach 86.2%. This method demonstrates excellent feasibility for large-scale production, indicating that the catalytic system has good prospects for industrial application.

[0020] This invention relates to a method for preparing adiponitrile from cyclohexene. Using a designed and synthesized heterogeneous, inexpensive Mn-Fe oxide as a catalyst, and under conditions of oxygen and ammonia atmosphere with the addition of auxiliary agents, highly efficient catalytic oxidative ammonialation of cyclohexene to adiponitrile is achieved, with a yield as high as 86.2%. The innovation of this process lies in the adoption of a novel heterogeneous catalytic ammonia oxidation technology route, which has outstanding advantages such as simple operation, low catalyst cost, high adiponitrile yield, and environmental friendliness, making it suitable for industrial production applications.

[0021] This invention exhibits significant technical advantages and practical value compared to existing technologies, mainly in the following two aspects:

[0022] Firstly, regarding the catalyst, the Mn-Fe oxide catalyst used in this technology has widely available and low-cost raw materials, and its preparation process is simple and controllable, facilitating large-scale production. Particularly noteworthy is the catalyst's excellent recyclability; it can be reused after simple filtration, and its catalytic activity and selectivity remain stable, providing a strong guarantee for reducing production costs.

[0023] Secondly, this technology innovatively develops a completely new process route. Compared with other existing production processes (as shown in Table 1): the adipic acid catalytic ammoniation method has been largely phased out due to the high cost of adipic acid; the acrylonitrile electrolysis process has a wide range of raw material sources and features low energy consumption, high yield, and high product quality, but it has been gradually phased out due to the high market price of acrylonitrile and small production scale; the butadiene method is complex, causes severe equipment corrosion, requires large investments, and consumes large amounts of hydrogen cyanide, and is also largely phased out. This method uses cyclohexene as a starting material to directly prepare adiponitrile through an ammoniation reaction. This innovative route has multiple advantages: simplified reaction steps, the use of a recyclable and inexpensive heterogeneous catalyst system, and complete avoidance of the use of highly toxic hydrogen cyanide. In practical applications, this route can achieve an adiponitrile yield of up to 86.2%, while also possessing the characteristics of simple process and environmental friendliness, demonstrating good prospects for industrial application. These advantages make this technology a promising next-generation green process for adiponitrile production.

[0024] Table 1 Comparison of Adiponitrile Production Processes

[0025] Attached Figure Description

[0026] Figure 1 The Mn3Fe2O prepared as follows x Scanning electron microscope image of the -0.3G-200 catalyst.

[0027] Figure 2 The Mn3Fe2O prepared as follows x Transmission electron microscope image of the -0.3G-200 catalyst. Detailed Implementation

[0028] The following examples will help to understand the present invention, but the scope of the present invention is not limited thereto.

[0029] The following examples illustrate the preparation method of Mn-Fe oxide catalysts: Mn3Fe2O x -0.3G-200: First, a mixture of 5 mmol MnSO4, 3.3 mmol FeSO4, and 2.5 mmol citric acid solids was ground for 30 min to achieve uniform mixing. Then, it was calcined in a muffle furnace at 200 °C for 2 h under air atmosphere to obtain the catalyst Mn3Fe2O. x -0.3G-200 (the following number represents the calcination temperature, which is 200 in this case, and the same applies below). The result is as follows: Figure 1 and 2 As shown in the figure, Mn3Fe2O XThe -0.3G-200 catalyst possesses a well-designed and ideal hierarchical nanostructure. This explains why the catalyst exhibits excellent catalytic activity and stability in the ammoxidation of cyclohexene to adiponitrile.

[0030] Mn3Fe2O x -0.2G-200, Mn3Fe2O x -0.1G-200, Mn3Fe2O x The preparation method of -0.05G-200 is similar to that of the above catalyst Mn3Fe2O x The synthesis process of -0.3G-200 is basically the same, the only difference being that 1.65 mmol, 0.825 mmol, and 0.4125 mmol of citric acid are used instead of 2.5 mmol of citric acid, respectively. The other processes and conditions are the same as those of the catalyst Mn3Fe2O mentioned above. x The synthesis process of -0.3G-200.

[0031] Mn3Fe2O x -0.3G-300, Mn3Fe2O x -0.3G-400, Mn3Fe2O x The preparation method of -0.3G-500 is similar to that of the above catalyst Mn3Fe2O x The synthesis process of -0.3G-200 is basically the same, the only difference being that calcination is carried out in a muffle furnace under air atmosphere at 300 ℃, 400 ℃, and 500 ℃ instead of calcination at 200 ℃. Other processes and conditions are the same as those for the catalyst Mn3Fe2O mentioned above. x The synthesis process of -0.3G-200.

[0032] Mn3Fe2O x -0.3G1-200, Mn3Fe2O x -0.3G2-200, Mn3Fe2O x -0.3G3-200 and Mn3Fe2O x The preparation method of -0.3G4-200 is similar to that of the above catalyst Mn3Fe2O x The synthesis process of -0.3G-200 is basically the same, the only difference being that equal molar amounts of vitamin C, glucose, fructose, and malic acid are used as grinding aids instead of citric acid. Other processes and conditions are the same as the catalyst Mn3Fe2O mentioned above. x The synthesis process of -0.3G-200.

[0033] Mn3Fe2O x The preparation method of -0.3G1-200-MnCl2 is similar to that of the above catalyst Mn3Fe2O xThe synthesis process of -0.3G-200 is basically the same, the only difference being that MnCl2 is used as the manganese source instead of MnSO4 in the same molar amount. Other processes and conditions are the same as those of the catalyst Mn3Fe2O mentioned above. x Synthesis process of -0.3G-200-MnCl2.

[0034] Mn3Fe2O x The preparation method of -0.3G1-200-FeCl2 is similar to that of the above catalyst Mn3Fe2O x The synthesis process of -0.3G-200 is basically the same, the only difference being that FeCl2 is used as the iron source instead of FeSO4 in the same molar amount. Other processes and conditions are the same as those of the catalyst Mn3Fe2O mentioned above. x Synthesis process of -0.3G-200-FeCl2.

[0035] According to CN119707741A, a catalyst of 4wt% VOx / TiO2 was prepared.

[0036] Example 1

[0037] Cyclohexene (2 mmol) and Mn3Fe2O x -0.3G-200 (60 mg), NHS (20 mol%, relative to 20 mol% of cyclohexene), and acetonitrile (4 mL) were sequentially added to a 25 mL high-pressure reactor, which was then sealed. The reactor was then charged with 0.5 MPa NH3 and 0.5 MPa O2 and placed at 100 °C. o The reaction was carried out in an oil bath for 5 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The pressure was slowly released and the reactor was opened. 20 mg of naphthalene was added as an internal standard, followed by 2 mL of acetonitrile for dilution. The mixture was stirred, centrifuged, and the supernatant was taken for GC and GC-MS analysis.

[0038] Example 2-13

[0039] Except for changing the type of catalyst, all other processes and conditions are the same as those in Example 1, as detailed in Table 2:

[0040] Reaction conditions: cyclohexene (2 mmol), Mn a Fe b O x -zG (60 mg), NHS (20 mol%), acetonitrile (4 mL), NH3 (0.5 MPa), O2 (0.5 MPa), 100 o C, 5 h.

[0041]

[0042] Table 2. Catalytic performance of different catalysts in the ammoxidation of cyclohexene to adiponitrile

[0043]

[0044] Examples 14-16

[0045] Besides changing Mn3Fe2O x Except for the dosage of -0.3G-200, all other processes and conditions are the same as those in Example 1, as detailed in Table 3:

[0046] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x -0.3G-200, NHS (20mol%), acetonitrile (4mL), NH3 (0.5MPa), O2 (0.5MPa), 100 o C, 5 h.

[0047]

[0048] Table 3. Different Mn3Fe2O x Effect of the amount of -0.3G-200 on the catalytic reaction of cyclohexene to adiponitrile

[0049]

[0050] Examples 17-20

[0051] Except for replacing the additive NHS with 4-nitrophenol, MPA, ascorbic acid, and NIS, the other processes and conditions are the same as those in Example 1, as shown in Table 4.

[0052] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x -0.3G-200 (60mg), Additives (20mol%), Acetonitrile (4mL), NH3 (0.5 MPa), O2 (0.5 MPa), 100 o C, 5 h.

[0053]

[0054] Table 4. Effects of different additives on Mn3Fe2O x The effect of -0.3G-200 catalyzing the preparation of adiponitrile from cyclohexene

[0055]

[0056] Examples 21-23

[0057] Except for changing the amount of NHS (mol%) relative to the amount of cyclohexene, all other processes and conditions are the same as those in Example 1, as shown in Table 5:

[0058] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x -0.3G-200 (60mg), NHS, acetonitrile (4mL), NH3 (0.5MPa), O2 (0.5MPa), 100 o C, 5 h.

[0059]

[0060] Table 5. Effects of different amounts of NHS on Mn3Fe2O x The effect of -0.3G-200 catalyzing the preparation of adiponitrile from cyclohexene

[0061]

[0062] Examples 24-30

[0063] Except for replacing the solvent acetonitrile with 1,4-dioxane, tert-amyl alcohol, 1,2-dichloroethane, DMSO, DMF, n-heptane, and tetrahydrofuran, the other processes and conditions are the same as those in Example 1, as shown in Table 6.

[0064] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x -0.3G-200 (60mg), NHS (20mol%), solvent (4mL), NH3 (0.5MPa), O2 (0.5MPa), 100 o C, 5 h.

[0065]

[0066] Table 6. Effects of different solvents on Mn3Fe2O x The effect of -0.3G-200 catalyzing the preparation of adiponitrile from cyclohexene

[0067]

[0068] Examples 31-35

[0069] Except for changing the reaction temperature, all other processes and conditions are the same as those in Example 1, as detailed in Table 7:

[0070] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x-0.3G-200 (60mg), NHS (20mol%), acetonitrile (4mL), NH3 (0.5MPa), O2 (0.5MPa), 5 h.

[0071]

[0072] Table 7. Effect of different reaction temperatures on Mn3Fe2O x The effect of -0.3G-200 catalyzing the preparation of adiponitrile from cyclohexene

[0073]

[0074] Examples 36-40

[0075] Except for the change in reaction time, all other processes and conditions are the same as those in Example 1, as detailed in Table 8:

[0076] Reaction conditions: cyclohexene (2 mmol), Mn3Fe2O x -0.3G-200 (60mg), NHS (20mol%), acetonitrile (4mL), NH3 (0.5MPa), O2 (0.5MPa), 100 o C.

[0077]

[0078] Table 8. Effects of different reaction times on Mn3Fe2O x The effect of -0.3G-200 catalyzing the preparation of adiponitrile from cyclohexene

[0079]

[0080] Table 2-8 shows that the molar ratio of grinding aid to total metal content (Examples 1-4), calcination temperature (Examples 1 and 5-7), and type of grinding aid (Examples 1 and 8-11) added during catalyst preparation have a certain impact on catalytic activity. Among them, the catalyst prepared with a molar ratio of grinding aid to total metal content of 0.3, a calcination temperature of 200 °C, and citric acid as a grinding aid has the highest activity (Example 1). In addition, the reaction conditions for the ammoxidation of cyclohexene to adiponitrile were optimized, and it was found that the amount of catalyst added (Examples 1 and 14-16), the type and amount of additives added (Examples 1 and 17-23), the type of solvent (Examples 1 and 24-30), the reaction temperature (Examples 1 and 31-35), and the reaction time (Examples 1 and 36-40) all affect the yield of adiponitrile.

[0081] Example 41

[0082] Cyclohexene (20 mmol) and Mn3Fe2O x -0.3 G-200 (600 mg), NHS (20 mol%, relative to 20 mol% of cyclohexene), and acetonitrile (40 mL) were sequentially added to a 180 mL high-pressure reactor, which was then sealed. The reactor was then charged with 0.5 MPa NH3 and 0.5 MPa O2 and placed at 100 °C. o The reaction was carried out in an oil bath for 5 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The pressure was slowly released and the reactor was opened. 200 mg of naphthalene was added as an internal standard, followed by 20 mL of acetonitrile for dilution. The mixture was stirred, centrifuged, and the supernatant was taken for GC and GC-MS analysis.

[0083] Examples 42-61

[0084] After the reaction in Example 41 was completed, the solid catalyst was collected by centrifugation, washed with acetonitrile, and then recycled for the next reaction. The operation method and steps of the recycling reaction were the same as in Example 31. The specific results are shown in Table 9. Mn3Fe2O x -0.3G-200 can be recycled at least 20 times with its activity remaining essentially unchanged, indicating that the catalyst has good cycle stability.

[0085] Reaction conditions: cyclohexene (20 mmol), Mn3Fe2O x -0.3G-200 (600mg), NHS (20mol%), acetonitrile (40mL), NH3 (0.5MPa), O2 (0.5MPa), 100 o C, 5 h.

[0086]

[0087] Table 9. Cyclic experiments of selective ammoxidation of cyclohexene to adiponitrile

[0088]

[0089] In summary, the Mn-Fe oxide-catalyzed ammoxidation method for preparing adiponitrile proposed in this invention has multiple advantages, including a novel and reliable process route, low production cost, minimal environmental pollution, and recyclable catalyst, making it a promising direction for adiponitrile production process research and development in my country.

Claims

1. A method for preparing adiponitrile by ammoxidation of cyclohexene, characterized in that, Cyclohexene, Mn-Fe oxide catalyst, additives and reaction solvent are added to a high-pressure reactor, ammonia and oxygen source gas are introduced, and then the reaction is heated to obtain adiponitrile product. The preparation method of Mn-Fe oxide catalyst is as follows: First, MnSO4, FeSO4 and a grinding aid solid mixture are ground for 5-30 min to mix evenly. Then, the mixture is calcined in a muffle furnace at 200-500℃ for 2-4 h in an air atmosphere to obtain the Mn-Fe oxide catalyst. a Fe b O x -zG, the catalyst Mn a Fe b O x -zG is used for the one-step ammoxidation of cyclohexene to prepare adiponitrile, where G represents a grinding aid; a / b represents the molar ratio of Mn / Fe in the catalyst, which is 0.6-1.55; z represents the molar ratio of the grinding aid added during the grinding process to the total metal content, which is 0.1-0.

4. The grinding aid is at least one of vitamin C, glucose, xylose, malic acid, citric acid, lauric acid, palmitic acid and benzoic acid; The additive used is at least one of N-hydroxysuccinimide, 4-nitrophenol, 3-mercaptopropionic acid, and N-iodosuccinimide; The reaction solvent is at least one of 1,4-dioxane, acetonitrile, tert-amyl alcohol, dimethyl sulfoxide, N,N-dimethylformamide, n-heptane, and tetrahydrofuran; the reaction temperature is 75-130 °C; and the reaction time is 3-12 h.

2. The method for preparing adiponitrile by ammoxidation of cyclohexene according to claim 1, characterized in that, The oxygen source gas is pure oxygen or air.

3. The method for preparing adiponitrile by ammoxidation of cyclohexene according to claim 1, characterized in that, The molar ratio of the additive to the cyclohexene feed is 0.15-0.

2.

4. The method for preparing adiponitrile by ammoxidation of cyclohexene according to claim 1, characterized in that, For every 2 mmol of cyclohexene, the amount of Mn-Fe oxide catalyst used is 40-80 mg.

5. The method for preparing adiponitrile by ammoxidation of cyclohexene according to claim 1, characterized in that, For every 2 mmol of cyclohexene, the amount of reaction solvent used is 4-6 mL.

6. The method for preparing adiponitrile by ammoxidation of cyclohexene according to claim 1, characterized in that, The gas pressures of ammonia and oxygen source gases are 0.5-0.9 MPa, respectively.

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