Process for the aminolysis of caprolactam to aminocapronitrile

Abstract

The application relates to the technical field of organic compounds, in particular to a method for preparing aminocapronitrile by caprolactam aminolysis; the method comprises the following steps: in the presence of a MOFs catalyst, performing aminolysis reaction on caprolactam to obtain the aminocapronitrile; wherein the MOFs catalyst is a metal-organic framework material with a porous structure formed by self-assembly of metal ions and phosphonic acid ligands through coordination bonds; the metal ions are selected from at least one of Zn 2+ , Co 2+ , Ni 2+ , Al 3+ and Zr 4+ ; and the phosphonic acid ligands are selected from at least one of monophosphonic acid ligands and multidentate aromatic phosphonic acid ligands. The MOFs catalyst can safely and effectively catalyze the preparation of aminocapronitrile by caprolactam aminolysis, has high catalytic efficiency, good stability and relatively mild reaction conditions for the preparation of aminocapronitrile by caprolactam aminolysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic compounds, in particular to a method for preparing aminocapronitrile by caprolactam ammonolysis. BACKGROUND

[0002] Aminocapronitrile is a key intermediate for the synthesis of hexamethylenediamine, which is an important chemical raw material and is widely used in the production of nylon 66, polyurethane and other polymer materials, and has an irreplaceable role in the fields of textiles, automobiles, electronics and the like. At present, the mainstream process for preparing aminocapronitrile in the industry is caprolactam ammonolysis, which uses caprolactam and ammonia as raw materials to generate aminocapronitrile through the action of a catalyst under high temperature and high pressure conditions.

[0003] In the existing process for preparing aminocapronitrile by caprolactam ammonolysis, the catalysts used are mainly metal oxides (such as aluminum oxide and zirconium oxide), supported metal catalysts (such as nickel and cobalt catalysts supported on carbon molecular sieves) or alkali metal salt catalysts (such as sodium carbonate and cobalt chloride). However, these traditional catalysts have the following significant defects: ① low catalytic activity: the conversion rate of caprolactam is usually less than 85% and the selectivity of aminocapronitrile is less than 90% using traditional catalysts, resulting in low utilization of raw materials, increased production of oligomers, and increased difficulty and cost of subsequent separation and purification; ② poor stability: under the ammonolysis reaction conditions of high temperature (usually 300℃~350℃) and high pressure (5MPa~10MPa), traditional catalysts are prone to sintering, carbon deposition or loss of active components, resulting in a short service life, and generally requiring replacement after 100h~150h of continuous use, which seriously affects the continuity of production; ③ harsh reaction conditions: in order to achieve ideal reaction results, traditional catalysts require higher reaction temperature and pressure, which not only increases equipment investment and energy consumption, but also poses certain safety hazards. SUMMARY

[0004] Therefore, it is necessary to provide a method for preparing aminocapronitrile by caprolactam ammonolysis, which uses a catalyst that can safely and effectively catalyze the preparation of aminocapronitrile from caprolactam, has high catalytic efficiency, good stability and relatively mild reaction conditions for the preparation of aminocapronitrile from caprolactam.

[0005] Firstly, the present application provides a method for preparing aminocapronitrile by caprolactam ammonolysis, which comprises the following steps:

[0006] ammonolysis reaction of caprolactam in the presence of a MOFs catalyst to obtain the aminocapronitrile;

[0007] The MOFs catalyst is a metal-organic framework material with a porous structure formed by self-assembly of metal ions and phosphonic acid ligands through coordination bonds; the metal ions are selected from Zn 2+ , Co 2+Ni 2+ Al 3+ and Zr 4+ At least one of the following; the phosphonic acid ligand is selected from at least one of monophosphonic acid ligands and polydentate aromatic phosphonic acid ligands.

[0008] In some embodiments, the method satisfies at least one of the following conditions:

[0009] (1) The monophosphonic acid ligand is selected from at least one of methylphosphonic acid, phenylphosphonic acid, n-butylphosphonic acid, p-toluidine acid and aminotris(methylenephosphonic acid);

[0010] (2) The multidentate aromatic phosphonic acid ligand is selected from at least one of 1,4-benzenediphosphonic acid, 1,3,5-benzenediphosphonic acid and 2,2'-bipyridine-5,5'-bisphosphonic acid.

[0011] In some embodiments, the metal ions are selected from Zn. 2+ Co 2+ and Ni 2+ At least one of them.

[0012] In some embodiments, the MOF catalyst satisfies at least one of the following conditions:

[0013] (1) The specific surface area of ​​the MOF catalyst is 1000 m². 2 / g~2500m 2 / g;

[0014] (2) The pore size of the MOF catalyst is 0.5 nm to 2.0 nm;

[0015] (3) The thermal decomposition temperature of the MOF catalyst is ≥400℃.

[0016] In some embodiments, the preparation method of the MOF catalyst includes the following steps:

[0017] S1. Prepare a first organic solution containing the metal ions and a second organic solution containing the phosphonic acid ligand, respectively;

[0018] S2. The first organic solution is added dropwise to the second organic solution under stirring. After the addition is complete, stirring is continued for 30 min to 60 min to obtain a mixed reaction solution.

[0019] S3. Place the mixed reaction solution in a reaction vessel with a polytetrafluoroethylene liner, and then react at 120℃~180℃ for 24h~72h.

[0020] S4. After the reaction is complete, the catalyst is cooled, separated, washed and dried in sequence to obtain the MOF catalyst.

[0021] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0022] (1) the concentration of the metal ion in the first organic solution is 0.1 mol / L to 0.5 mol / L;

[0023] (2) the concentration of the phosphonic acid ligand in the second organic solution is 0.1 mol / L to 0.5 mol / L;

[0024] (3) the molar ratio of the metal ion to the phosphonic acid ligand is 1: (1-3).

[0025] In some embodiments, in step S3, the temperature of the reaction is 140°C to 160°C, and the reaction time is 48h to 60h.

[0026] In some embodiments, the step of performing an aminolysis reaction on caprolactam in the presence of a MOFs catalyst comprises:

[0027] adding the caprolactam and the MOFs catalyst into a high-pressure reaction kettle, introducing ammonia gas into the reaction kettle, and controlling the pressure in the kettle to reach 2MPa to 6MPa; heating to 240°C to 300°C, and performing an aminolysis reaction under stirring at 300r / min to 500r / min for 4h to 8h.

[0028] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0029] In some embodiments, the amount of the MOFs catalyst used is 1% to 5% of the mass of the caprolactam; and the molar ratio of the amount of the ammonia gas introduced to the caprolactam is (3-5): 1.

[0030] In some embodiments, after the aminolysis reaction is completed, the following steps are further included:

[0031] cooling and filtering separation are sequentially performed to obtain a crude aminocapronitrile and a reacted MOFs catalyst;

[0032] the crude aminocapronitrile is refined and purified by vacuum distillation to obtain a fine aminocapronitrile;

[0033] the reacted MOFs catalyst is recycled and utilized by the following method:

[0034] the reacted catalyst is washed with ethanol for 2 to 3 times, dried in a vacuum drying oven at 80°C to 100°C for 8h to 12h, and then calcined at 200°C to 250°C for 1h to 2h under a nitrogen atmosphere.

[0035] The application catalyzes caprolactam to prepare aminocapronitrile by ammonolysis through a MOFs catalyst with a specific composition, which has the following advantages:

[0036] Among them, in the MOFs catalyst used, ① the MOF material formed by the phosphonic acid ligand has high stability. Compared with carboxylic acid ligand, the phosphorus oxygen bond (P=O and P-O) in the phosphonic acid ligand has higher bond energy. When the phosphonic acid group is deprotonated and coordinated with metal ions (M), the M-O-P bond formed is very strong, and the average bond energy is usually higher than that of the M-O-C bond in the carboxylic acid MOF. In addition, compared with carboxylate (-COO - ), the negative charge on the phosphonate (-PO3 2- ) is more dispersed, and the electronegativity of the oxygen atom is stronger. This makes the coordination of phosphonate with metal ions (especially high-valence metal ions such as Zr 4+ , Al 3+ ) stronger, with stronger ionic bond characteristics, and ionic bonds are usually more difficult to break than coordination bonds. Therefore, when the MOF material formed by the phosphonic acid ligand of the application is used as a catalyst, the thermal decomposition temperature is higher than 300℃, and the structure is stable under the ammonolysis reaction conditions of 240℃~300℃, and is not easy to sinter, carbon deposit or lose active components. At the same time, the catalyst can recover activity by simple regeneration method, and can be reused for more than 5 times, with long service life, which reduces the replacement cost of the catalyst.

[0037] ② The MOF material formed by the phosphonic acid ligand has strong acidity, which can provide abundant active sites and improve the activity of the catalytic caprolactam ammonolysis reaction to prepare aminocapronitrile. On the one hand, the -PO3H group in the phosphonic acid MOF which is not completely deprotonated can provide strong B acid sites, which is the core of activating the carbonyl group and driving the ammonolysis reaction. On the other hand, the coordination unsaturated sites of the metal nodes (such as Zr 4+ ) can be used as L acid sites, which can also polarize the carbonyl group, and produce a synergistic catalytic effect with the B acid sites to improve the reaction activity and selectivity.

[0038] ③ The MOF material formed by the phosphonic acid ligand has ultra-high specific surface area and porosity, which can significantly improve the accessibility of the catalytic active sites, and further improve the conversion rate of caprolactam and the selectivity of aminocapronitrile. Unlike traditional catalysts, MOFs have regular pore structures, which not only can preferentially adsorb reactants to promote the reaction, but also can inhibit side reactions, such as preventing the formation of larger by-products or polymer precursors by steric hindrance, thereby improving the selectivity of the target product aminocapronitrile. Therefore, the MOFs catalyst of the application has ultra-high specific surface area and abundant active sites, which can significantly improve the conversion rate of caprolactam and the selectivity of aminocapronitrile.

[0039] ④The catalyst of the present application is used for catalyzing caprolactam aminolysis reaction, the reaction condition is mild, and the reaction process is green and environmentally friendly. Compared with the traditional catalyst, the catalyst of the present application can realize efficient aminolysis reaction at a lower reaction temperature (240℃~300℃) and pressure (2MPa~6MPa), which not only reduces the equipment investment and energy consumption, but also improves the safety of the production process; in the reaction process, the unreacted ammonia gas can be recycled and used, and the catalyst can be recycled and reused after regeneration, which reduces the waste of raw materials and waste emissions, and meets the development concept of green chemical industry.

[0040] ⑤The MOF material formed by the phosphonic acid ligand has a simple preparation method. The MOF catalyst is prepared by a solvothermal method, which is simple in process, easy to operate, and easy to control the reaction conditions, and is suitable for industrial large-scale production. DETAILED DESCRIPTION

[0041] The embodiments described in the specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0042] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit with any other upper limit to form a range not explicitly recited. Furthermore, although not explicitly recited, every point or individual number between the range end points is included in the range. Thus, every point or individual number can serve as its own lower limit or upper limit to combine with any other point or individual number or to combine with other lower limits or upper limits, to form a range not explicitly recited.

[0043] Metal-organic frameworks (MOFs) material is a kind of porous crystalline material with periodic network structure formed by self-assembly of metal ions or metal clusters and organic ligands through coordination bond. Due to its super-high specific surface area, rich pore structure, controllable active site and good thermal stability, it shows great application potential in the field of catalysis. Among them, the MOF material containing phosphonic acid ligand can form stable coordination structure with metal ions (M) due to the phosphorus-oxygen bond of the ligand, and the M-O-P bond formed after coordination is very strong, which significantly improves the stability of the MOF material. The MOF material containing phosphonic acid ligand contains both B acid sites and L acid sites, which can be used as acidic active center, and shows excellent performance in aminolysis, hydrolysis and other catalytic reactions.

[0044] In an embodiment of the present application, a method for preparing aminocapronitrile by aminolysis of caprolactam is provided, which comprises the following steps:

[0045] In the presence of the MOF catalyst, caprolactam is subjected to aminolysis reaction to obtain aminocapronitrile;

[0046] The MOFs catalyst is a metal-organic framework material with a porous structure formed by self-assembly of metal ions and phosphonic acid ligands through coordination bonds. The metal ions are selected from at least one of Zn 2+ , Co 2+ , Ni 2+ , Al 3+ , and Zr 4+ . The phosphonic acid ligands are selected from at least one of a monodentate phosphonic acid ligand and a multidentate aromatic phosphonic acid ligand.

[0047] In some embodiments, the monodentate phosphonic acid ligand is selected from at least one of methylphosphonic acid, phenylphosphonic acid, n-butylphosphonic acid, p-tolylphosphonic acid, and amino-tris (methylene phosphonic acid).

[0048] In some embodiments, the multidentate aromatic phosphonic acid ligand is selected from at least one of 1,4-benzenedi phosphonic acid, 1,3,5-benzene triphosphonic acid, and 2,2'-dipyridyl-5,5'-diphosphonic acid.

[0049] In some embodiments, the metal ions are selected from at least one of Zn 2+ , Co 2+ , and Ni 2+ .

[0050] In some embodiments, the specific surface area of the MOFs catalyst is 1000 m 2 / g~2500 m 2 / g.

[0051] In some embodiments, the pore size of the MOFs catalyst is 0.5 nm~2.0 nm.

[0052] In some embodiments, the thermal decomposition temperature of the MOFs catalyst is ≥400℃. Further, the thermal decomposition temperature of the MOFs catalyst is 400℃~500℃.

[0053] In some embodiments, the preparation method of the MOFs catalyst comprises the following steps:

[0054] S1, respectively preparing a first organic solution containing metal ions and a second organic solution containing phosphonic acid ligands;

[0055] S2, adding the first organic solution to the second organic solution under stirring, and continuing to stir for 30 min~60 min after the addition is completed to obtain a mixed reaction solution;

[0056] S3, placing the mixed reaction solution in a reaction kettle with a polytetrafluoroethylene liner, and then reacting at 120℃~180℃ for 24 h~72 h;

[0057] S4, after the reaction is completed, sequentially performing cooling, separation, washing, and drying to obtain the MOFs catalyst.

[0058] As an example, the reaction temperature in step S3 can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, or 180℃, or any value within the range defined by any two of the above values as the end values.

[0059] As an example, the reaction time in step S3 can be 24h, 25h, 26h, 28h, 30h, 32h, 35h, 38h, 40h, 42h, 45h, 48h, 50h, 52h, 55h, 48h, 60h, 62h, 65h, 68h, 70h, or 72h, or any value within the range defined by any two of the above values as the end values.

[0060] In some embodiments, the reaction temperature in step S3 is 140℃-160℃, and the reaction time is 48h-60h. The phosphonic acid MOFs catalyst prepared under this condition has a more regular pore structure and a higher specific surface area.

[0061] In some embodiments, the concentration of metal ions in the first organic solution is 0.1mol / L-0.5mol / L. As an example, the concentration of metal ions can be 0.1mol / L, 0.15mol / L, 0.2mol / L, 0.25mol / L, 0.3mol / L, 0.35mol / L, 0.4mol / L, 0.45mol / L, or 0.5mol / L, or any value within the range defined by any two of the above values as the end values.

[0062] In some embodiments, the concentration of phosphonic acid ligands in the second organic solution is 0.1mol / L-0.5mol / L. As an example, the concentration of phosphonic acid ligands can be 0.1mol / L, 0.15mol / L, 0.2mol / L, 0.25mol / L, 0.3mol / L, 0.35mol / L, 0.4mol / L, 0.45mol / L, or 0.5mol / L, or any value within the range defined by any two of the above values as the end values.

[0063] In some embodiments, the step of preparing the first organic solution containing metal ions comprises: dissolving a metal salt containing metal ions in a first organic solvent to obtain the first organic solution containing metal ions.

[0064] In some embodiments, the metal salt is selected from at least one of zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, cobalt nitrate, cobalt acetate, cobalt chloride, cobalt sulfate, nickel nitrate, nickel acetate, nickel chloride, nickel sulfate, aluminum chloride, aluminum sulfate, and zirconium chloride.

[0065] In some embodiments, the first organic solvent is a mixed solvent of N,N-dimethylformamide (DMF), ethanol and deionized water in a volume ratio of (1-3):1:1.

[0066] In some embodiments, the step of preparing the second organic solution containing the phosphonic acid ligand comprises dissolving the phosphonic acid ligand in the second organic solvent.

[0067] In some embodiments, the second organic solvent is the same as the component of the first organic solvent.

[0068] In some embodiments, the molar ratio of the metal ion to the phosphonic acid ligand is 1:(1-3). For example, the molar ratio of the metal ion to the phosphonic acid ligand can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, or any ratio within the above range. Preferably, the molar ratio of the metal ion to the phosphonic acid ligand is 1:(1.5-2). A slight excess of the phosphonic acid ligand over the metal ion can ensure sufficient coordination between the two, improve the yield and stability of the product, and thus improve the conversion rate and selectivity of the catalytic reaction.

[0069] In some embodiments, the step of subjecting caprolactam to an amination reaction in the presence of the MOFs catalyst comprises:

[0070] The caprolactam and the MOFs catalyst are added to a high-pressure reaction kettle, ammonia gas is introduced into the kettle to make the pressure in the kettle reach 2-6 MPa, the temperature is raised to 240-300°C, and the amination reaction is carried out under stirring at 300-500 r / min for 4-8 h.

[0071] In some embodiments, the amount of the MOFs catalyst used is 1-5% of the mass of the caprolactam. For example, the amount of the MOFs catalyst used can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5% of the mass of the caprolactam, or any value within the range defined by any two of the above values as end values.

[0072] In some embodiments, the molar ratio of the amount of the ammonia gas introduced to the caprolactam is (3-5):1. For example, the molar ratio of the amount of the ammonia gas introduced to the caprolactam can be 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, or any ratio within the above range. The excess ammonia gas not only participates in the reaction as a reactant, but also inhibits the occurrence of side reactions, thereby improving the selectivity of aminocapronitrile.

[0073] In some embodiments, after the amination reaction is completed, the following steps are further included:

[0074] The cooling and filtration separation are sequentially carried out to obtain aminocapronitrile crude product and the MOFs catalyst after the reaction.

[0075] The crude aminocapronitrile is refined and purified by reduced pressure distillation to obtain aminocapronitrile fine product.

[0076] In some embodiments, the conditions of the reduced pressure distillation include a vacuum degree of 0.09 MPa to 0.095 MPa and a distillation temperature of 150°C to 170°C.

[0077] In some embodiments, the purity of the aminocapronitrile fine product is ≥99.5%.

[0078] In some embodiments, the MOFs catalyst after reaction is recycled by the following method:

[0079] The catalyst after reaction is washed with ethanol for 2 to 3 times, dried in a vacuum drying oven at 80°C to 100°C for 8 to 12 hours, and then calcined at 200°C to 250°C for 1 to 2 hours under a nitrogen atmosphere.

[0080] The present application is further described below in conjunction with examples. It should be understood that these examples are only for illustrative purposes, and various modifications and changes within the scope of the disclosure of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further treatment, and the instruments used in the examples are commercially available.

[0081] Example 1

[0082] 1. The MOFs catalyst is prepared according to the following steps:

[0083] (1) Dissolution of raw materials: 0.1 mol of zinc nitrate hexahydrate is dissolved in a mixed solvent composed of 300 mL of DMF, 100 mL of ethanol and 100 mL of water to obtain a zinc nitrate solution; 0.2 mol of phenyl phosphonic acid is dissolved in the same mixed solvent to obtain a phenyl phosphonic acid solution; wherein the molar ratio of zinc ions to phenyl phosphonic acid is 1:2.

[0084] (2) Preparation of mixed reaction solution: the zinc nitrate solution is slowly added to the phenyl phosphonic acid solution while stirring, and after the addition is completed, the stirring is continued for 45 minutes to obtain a uniform mixed reaction solution;

[0085] (3) Solvothermal reaction: the mixed reaction solution is transferred to a 1000 mL reaction kettle with a polytetrafluoroethylene liner, sealed and placed in an oven for reaction at 150°C for 50 hours;

[0086] (4) Separation and purification: after the reaction is completed, the reaction product is cooled to room temperature, washed with DMF 4 times, and then washed with ethanol 4 times;

[0087] (5) Drying activation: the washed product was placed in a vacuum drying oven, dried at 100°C for 18 hours to obtain the MOFs catalyst.

[0088] The specific surface area of the catalyst was 2200 m² / g, the pore size was 1.2 nm, and the thermal decomposition temperature was 420°C.

[0089] Specific surface area and pore size test: an ASAP 2460 specific surface and porosity analyzer of Micromeritics Corporation was used. The sample treatment steps for testing: 100 mg of sample was pre-degassed at 423 K for 12 h under vacuum, and then tested at 77 K. The micropore and mesopore analysis were simulated using HK and BJH calculation methods, respectively.

[0090] Thermal decomposition temperature test: a thermal gravimetric analyzer (TG) of TA Corporation of France, model TGA550, was used to analyze the thermal stability of the MOF catalyst. The sample treatment steps for testing: about 5 mg of sample was weighed, and the temperature was raised from room temperature to 900°C at a rate of 10°C / min under nitrogen atmosphere, and then lowered to room temperature.

[0091] 2. The MOF catalyst was used for the aminolysis of caprolactam to prepare aminocapronitrile, and the specific steps were as follows:

[0092] (1) Reaction system setup: 100 g of caprolactam and 3 g of MOFs catalyst were added to a 1 L high-pressure reaction kettle, and ammonia gas was introduced into the reaction kettle to make the pressure in the reaction kettle reach 4 MPa (the molar ratio of ammonia gas to caprolactam was 4:1);

[0093] (2) Aminolysis reaction: the reaction kettle was heated to 270°C, and the stirring speed was 400 r / min, and the reaction was carried out for 6 hours;

[0094] (3) Product separation: after the reaction was completed, it was cooled to room temperature, and the unreacted ammonia gas was released (for recycling), and the MOFs catalyst was separated by filtration;

[0095] (4) Purification: the filtrate was subjected to vacuum distillation (vacuum degree 0.092 MPa, distillation temperature 160°C) to obtain aminocapronitrile product.

[0096] After detection, the conversion rate of caprolactam was 96.2%, the selectivity of aminocapronitrile was 98.5%, and the product purity was 99.7%.

[0097] As can be seen from the table, after the regenerated catalyst was reused for 5 times, the conversion rate of caprolactam remained above 94%, and the selectivity of aminocapronitrile remained above 97%, indicating that the catalyst had excellent regeneration performance and stability.

[0098] 3. Recovery and regeneration of the catalyst:

[0099] The MOFs catalyst separated from Example 1 was washed with ethanol for 3 times and dried in a vacuum drying oven at 90°C for 10 hours to obtain the regenerated catalyst. The regenerated catalyst was reused for 5 times according to the method of "2, MOFs catalyst for the aminolysis of caprolactam to prepare aminocapronitrile" in Example 1. The caprolactam conversion rate and the selectivity of aminocapronitrile of each reaction were shown in Table 2.

[0100] Example 2

[0101] The same as Example 1, except that the amount of phenylphosphonic acid added in step (1) was 0.1 mol, i.e. the molar ratio of zinc ion to phenylphosphonic acid was 1:1.

[0102] The catalyst obtained from Example 2 was used for the reaction, and the caprolactam conversion rate was 94.3% and the selectivity of aminocapronitrile was 96.6%.

[0103] Example 3

[0104] The same as Example 1, except that the phosphonic acid ligand in step (1) was n-butylphosphonic acid (0.2 mol).

[0105] The catalyst obtained from Example 3 was used for the reaction, and the caprolactam conversion rate was 96.4% and the selectivity of aminocapronitrile was 98.2%.

[0106] Example 4

[0107] The same as Example 1, except that the phosphonic acid ligand in step (1) was 1,4-phenyldiphosphonic acid (0.2 mol).

[0108] The catalyst obtained from Example 4 was used for the reaction, and the caprolactam conversion rate was 94.2% and the selectivity of aminocapronitrile was 95.8%.

[0109] Example 5

[0110] The same as Example 1, except that the metal salt in step (1) was cobalt nitrate hexahydrate (0.2 mol).

[0111] The catalyst obtained from Example 5 was used for the reaction, and the caprolactam conversion rate was 95.8% and the selectivity of aminocapronitrile was 98.4%.

[0112] Example 6

[0113] The same as Example 1, except that the metal salt in step (1) was zirconium chloride (0.2 mol).

[0114] The catalyst obtained from Example 6 was used for the reaction, and the caprolactam conversion rate was 93.6% and the selectivity of aminocapronitrile was 95.3%.

[0115] Comparative Example 1

[0116] In the same way as the examples, the MOF catalyst was replaced by an equivalent amount of conventional γ-alumina catalyst (5% of the mass of caprolactam), and the other reaction conditions were unchanged, to carry out the caprolactam aminolysis reaction.

[0117] It was detected that the conversion rate of caprolactam was 82.3%, and the selectivity of aminocapronitrile was 88.5%, which was much lower than the performance of the MOF catalyst of the present application. At the same time, after the alumina catalyst was reused twice, the conversion rate of caprolactam decreased to 75.1%, and the selectivity decreased to 85.2%, and the stability was obviously poor.

[0118] Table 1: Performance parameter statistics table of each example and comparative example

[0119]

[0120] Table 2: Catalyst effect statistics table of MOF catalyst after recycling

[0121]

[0122] From the data in Table 1 and Table 2, it can be seen that when the caprolactam aminolysis method of the present application is used to prepare aminocapronitrile by using the MOF catalyst, the caprolactam has a high conversion rate of more than 93%; at the same time, the aminocapronitrile has a high selectivity of more than 95%. In addition, the MOF catalyst prepared in Example 1 still has high catalyst properties after being recycled for 5 times, and has good stability of catalytic activity.

[0123] When the conventional γ-alumina catalyst is used in Comparative Example 1, the conversion rate of caprolactam is only 82.2%, and the selectivity of aminocapronitrile is only 88.5%; at the same time, after the alumina catalyst is reused twice, the conversion rate of caprolactam decreases to 75.1%, and the selectivity decreases to 85.2%, and the stability is obviously poor.

[0124] In summary, the MOF catalyst of the present application has significant performance advantages in the caprolactam aminolysis reaction to prepare aminocapronitrile, and can completely replace the traditional catalyst, and has a broad industrial application prospect.

[0125] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing aminohexanonitrile by ammonolysis of caprolactam, characterized in that, Includes the following steps: Caprolactam and MOF catalyst were added to a high-pressure reactor, and ammonia gas was introduced into the reactor to control the pressure inside the reactor to reach 2 MPa to 6 MPa. The temperature was raised to 240℃ to 300℃, and the ammonolysis reaction was carried out under stirring conditions of 300 r / min to 500 r / min for 4 h to 8 h to obtain the aminohexanonitrile. The MOFs catalyst is a metal organic framework material with a porous structure formed by self-assembly of metal ions and phosphonic acid ligands through coordination bonds; the metal ions are selected from at least one of Zn 2+ , Co 2+ and Zr 4+ ; and the phosphonic acid ligands are selected from at least one of phenylphosphonic acid, n-butylphosphonic acid and 1,4-benzenediphosphonic acid.

2. The method according to claim 1, characterized in that, The MOF catalyst satisfies at least one of the following conditions: (1) the MOFs catalyst has a specific surface area of 1000 m 2 / g~2500 m 2 / g; (2) The pore size of the MOF catalyst is 0.5 nm to 2.0 nm; (3) The thermal decomposition temperature of the MOF catalyst is ≥400℃.

3. The method according to claim 1, characterized in that, The preparation method of the MOF catalyst includes the following steps: S1. Prepare a first organic solution containing the metal ions and a second organic solution containing the phosphonic acid ligand, respectively; S2. The first organic solution is added dropwise to the second organic solution under stirring. After the addition is complete, stirring is continued for 30 min to 60 min to obtain a mixed reaction solution. S3. Place the mixed reaction solution in a reaction vessel with a polytetrafluoroethylene liner, and then react at 120℃~180℃ for 24h~72h. S4. After the reaction is complete, the catalyst is cooled, separated, washed and dried in sequence to obtain the MOF catalyst.

4. The method according to claim 3, characterized in that, The preparation method satisfies at least one of the following conditions: (1) In the first organic solution, the concentration of the metal ions is 0.1 mol / L to 0.5 mol / L; (2) In the second organic solution, the concentration of the phosphonic acid ligand is 0.1 mol / L to 0.5 mol / L; (3) The molar ratio of the metal ion to the phosphonic acid ligand is 1:(1~3).

5. The method according to claim 3, characterized in that, In step S3, the reaction temperature is 140℃~160℃ and the reaction time is 48h~60h.

6. The method according to claim 1, characterized in that, The amount of MOF catalyst used is 1% to 5% of the mass of caprolactam; the molar ratio of the amount of ammonia introduced to the amount of caprolactam is (3 to 5):

1.

7. The method according to claim 1, characterized in that, After the ammonolysis reaction is completed, the following steps are also included: The mixture was cooled and filtered sequentially to obtain crude aminohexanonitrile and the MOF catalyst after the reaction. The crude aminohexanonitrile was purified by vacuum distillation to obtain a refined aminohexanonitrile. The MOF catalyst after the reaction is recycled in the following manner: The catalyst after the reaction was washed with ethanol 2-3 times and dried in a vacuum drying oven at 80℃-100℃ for 8h-12h; then calcined at 200℃-250℃ for 1h-2h under a nitrogen atmosphere.

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