Nitrogen-doped carbon supported iron catalyst and its application in catalytic synthesis of aromatic nitrile

Abstract

The application discloses a nitrogen-doped carbon supported iron catalyst and application thereof in catalytic synthesis of aromatic nitrile, and relates to the use of the nitrogen-doped carbon supported iron catalyst as a catalyst to obtain aromatic nitrile through an ammoxidation reaction under a solvent-free condition, with aromatic alcohol and ammonia water as raw materials and under an oxygen or air atmosphere. Compared with a traditional method, the nitrogen-doped carbon supported iron catalyst provided by the application is used to perform ammoxidation under a solvent-free condition, so that the use of organic solvents is avoided, pollution caused by volatilization of the organic solvents to the environment is avoided, and reaction energy consumption and separation energy consumption caused by the solvents are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts and their applications, and particularly relates to a nitrogen-doped carbon supported iron catalyst and its application in catalytic synthesis of aromatic nitrile. BACKGROUND

[0002] Aromatic nitriles are an important class of fine chemicals, which are widely used in the fields of pharmaceuticals, agricultural chemicals, fuels, fragrances, synthetic fibers, synthetic rubbers and plastics, etc. For example, benzonitrile derivatives can be used for the production of drugs (such as anti-gout arthritis drug Febuxostat, AIDS treatment drug Etravirine, heart failure treatment drug Milrinone), herbicides (dichlobenil, bromophos), fungicides (Chlorothalonil, Azoxystrobin), etc.

[0003] Traditional synthesis of aromatic nitriles is mostly based on the reaction of hydrocyanic acid or metal cyanide as the cyano source, such as Sandmeier reaction, Rosenmund-von Braun reaction and halogenated aromatic hydrocarbon cyanation, etc. The environmental disasters in Bhopal in 1984 and Baia Mare in Romania in 2000 are both related to the synthesis of nitriles based on cyanide. Therefore, in the past few decades until today, the academic and industrial circles are trying to explore various new methods for the synthesis of functional nitriles without cyano group. Such as toluene ammoxidation, amide dehydration, amine oxidation, ammonia oxidation of CO2 / NH3 and oxidative cyanation of alcohol, etc.

[0004] The catalysts currently used for the ammoxidation of aromatic alcohols to synthesize aromatic nitriles mainly include manganese dioxide supported ruthenium monatomic catalyst, manganese dioxide supported cobalt oxide catalyst, etc. However, the above-mentioned catalytic systems all use organic reagents as solvents for the reaction, which not only causes a certain degree of cost increase and separation difficulty problem, but also leads to the production of by-products due to the change of reaction liquid ratio. Therefore, for the purpose of industrial application, there is a strong demand for the development of simple high activity, high selectivity, and synthesis of aromatic nitriles from aromatic alcohols under solvent-free conditions. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a nitrogen-doped carbon supported iron catalyst and its preparation method, and its application for the ammoxidation of aromatic alcohols to synthesize aromatic nitriles without solvent.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] The present application provides a nitrogen-doped carbon supported iron catalyst and its preparation method, and its application for the ammoxidation of aromatic alcohols to synthesize aromatic nitriles without solvent.

[0008] The present application provides a nitrogen-doped carbon supported iron catalyst, which comprises a nitrogen-doped carbon carrier and iron supported on the nitrogen-doped carbon carrier.

[0009] Preferably, the mass of the iron is 0.01-20%, preferably 0.01-10%, more preferably 0.1-10% of the mass of the nitrogen-doped carbon-supported iron catalyst.

[0010] Preferably, the mass of the nitrogen is 1-20%, preferably 1-15% of the nitrogen-doped carbon-supported iron catalyst.

[0011] Preferably, the mass of the carbon is 70-99%, preferably 70-90% of the nitrogen-doped carbon-supported iron catalyst.

[0012] Preferably, the specific surface area of the nitrogen-doped carbon-supported iron catalyst is 300-1200 m 2 / g, preferably 300-1000 m 2 / g, more preferably 300-800 m 2 / g.

[0013] The present application also provides a preparation method of the nitrogen-doped carbon-supported iron catalyst described in the above technical solution, comprising the following steps:

[0014] Mixing a soluble iron salt, a nitrogen-containing organic ligand and a template agent, drying to obtain a catalyst precursor;

[0015] The metal salt is one or more of ferric nitrate, ferric chloride, ferric sulfate, ferrous nitrate, ferrous chloride, ferrous sulfate, ferrous acetate, etc.

[0016] The nitrogen-containing organic ligand is one or more of urea, cyanamide, dicyanamide, melamine, 2-methylimidazole, guanidine hydrochloride, o-phenanthroline;

[0017] The template agent is one or more of nano-magnesium oxide, nano-calcium oxide, nano-magnesium hydroxide, nano-calcium hydroxide;

[0018] Thermally cracking the catalyst precursor in an inert atmosphere, and then washing with an acid solution of a certain concentration to remove iron metal, iron oxide and the template agent to obtain the nitrogen-doped carbon-supported iron catalyst;

[0019] The inert atmosphere is nitrogen or argon or a mixture of the two;

[0020] The thermal cracking temperature is 500-1100°C, preferably 600-1000°C, more preferably 600-900°C;

[0021] The temperature rising rate to the thermal cracking temperature is 0.5-30°C / min, preferably 0.5-20°C / min, more preferably 1-10°C / min;

[0022] The thermal cracking time is 0.5-12h, preferably 2-10h, more preferably 3-6h.

[0023] The application also provides a method for synthesizing aromatic nitrile by catalyzing aromatic alcohol ammoxidation, and the specific steps are as follows:

[0024] In the presence of oxygen or air, the nitrogen-doped carbon supported iron catalyst or the supported catalyst prepared by the above method, benzyl alcohol and ammonia water are subjected to ammoxidation reaction.

[0025] The mass percentage of the nitrogen-doped carbon supported iron catalyst, aromatic alcohol and 25-28wt% ammonia water is (0.05-0.5) : 1 : (1.25-10), preferably (0.05-0.2) : 1 : (1.25-5), more preferably (0.05-0.2) : 1 : (1.25-3).

[0026] The pressure of the oxygen or air is 0.1-6MPa, preferably 0.1-4MPa, more preferably 0.1-2MPa.

[0027] The reaction temperature is 25-150℃, preferably 25-120℃.

[0028] The reaction time is 0.5-24h, preferably 0.5-12h.

[0029] The aromatic alcohol includes benzyl alcohol or one of the following formulas -1 to -8:

[0030] .

[0031] The nitrogen-doped carbon supported iron catalyst provided by the application includes a nitrogen-doped carbon carrier and iron supported on the nitrogen-doped carbon carrier. In the application, the nitrogen-doped carbon supported iron catalyst is used for synthesizing aromatic nitrile by catalyzing aromatic alcohol ammoxidation without solvent, thereby avoiding pollution caused by volatilization of organic solvent to the environment and reducing reaction energy consumption caused by solvent use. The implementation results show that when the nitrogen-doped carbon supported iron catalyst provided by the application is used for catalyzing aromatic alcohol ammoxidation without solvent to prepare aromatic nitrile, the conversion rate of aromatic alcohol is 100%, the selectivity of aromatic nitrile is as high as 99%, and the catalyst has no obvious deactivation phenomenon after being repeatedly used for 10 times. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced as follows:

[0033] Figure 1 The XRD spectrum of the catalyst provided in the embodiment 1 of the application.

[0034] Figure 2 The image shows the XANES K-space spectrum of the catalyst provided in this invention.

[0035] Figure 3 The image shows the GC yield spectrum of the catalyst used in Example 7 for the solventless ammoxidation of benzyl alcohol to benzonitrile. Detailed Implementation

[0036] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0037] Example 1:

[0038] Ferrous chloride (0.126 g) and o-phenanthroline (C) were mixed in a molar ratio of 1:2. 12 H8N2 was added to 50 mL of ethanol and stirred for 1 hour. Then, 2.5 g of nano-magnesium oxide (average particle size: 20 nm) was added as a template agent and stirred for another 3 hours. After drying, the catalyst was pyrolyzed at 700 °C for 3 hours under a nitrogen atmosphere at a heating rate of 5 °C / min. Then, it was etched with 50 mL of 4 mol / L nitric acid aqueous solution for 120 min. After washing and drying, the nitrogen-doped carbon-supported iron catalyst was obtained and named FeNC-700.

[0039] Examples 2-6:

[0040] Following the same preparation method as in Example 1, except that the metal salt was replaced with one of MnCl2, CoCl2, NiCl2, CuCl2, and ZnCl2, respectively, as Examples 2-6, the metal salt and o-phenanthroline (C 12 The molar ratio of H8N2 was 1:2, and the rest of the preparation method was the same as in Example 1. The nitrogen-doped carbon-supported metal catalysts obtained in Examples 2-6 were named MnNC-700, CoNC-700, NiNC-700, CuNC-700, and ZnNC-700, respectively.

[0041] Examples 7-12:

[0042] The nitrogen-doped carbon-supported metal catalysts prepared in Examples 1-6 were used for the ammoxidation of benzyl alcohol to synthesize benzonitrile.

[0043] Reaction conditions: Weigh 10 mg of catalyst, add the catalyst, benzyl alcohol and ammonia water in a mass ratio of 0.1:1:2 into the reaction vessel, seal it and purge with 0.5 MPa oxygen, heat to 120 °C, keep warm and stir for 12 h to obtain benzonitrile.

[0044] Table 1. Study on the ammonia oxidation performance of benzyl alcohol by different nitrogen-doped carbon-supported metal catalysts (Examples 7-12)

[0045]

[0046] As shown in Table 1, this invention exhibits significantly higher conversion rates of benzyl alcohol and yields of benzonitrile under FeNC-700 catalysis.

[0047] Examples 13-20:

[0048] Reaction conditions: Weigh 10 mg of FeNC-700 catalyst, and add FeNC-700 catalyst, benzyl alcohol, and ammonia water to a reaction vessel in a mass ratio of 0.1:1:2. After sealing, purge with 5 atm of oxygen, heat to 120℃, and stir for 12 h to obtain benzonitrile. After the reaction is complete, allow the reactor to cool naturally to room temperature. During the reaction, 2 mL of solvent can be added, which can be one of ultrapure water, n-heptane, toluene, 1,4-epoxyhexadecane, acetonitrile, tert-amyl alcohol, or tert-butanol, or no solvent.

[0049] Table 2. FeNC-700-catalyzed ammonia oxidation of benzyl alcohol in different solvents

[0050]

[0051] As shown in Table 2, under the FeNC-700 catalytic reaction in this invention, the highest conversion rate of benzyl alcohol and the highest yield of benzonitrile were achieved using solvent-free conditions.

[0052] Examples 21-26:

[0053] Reaction conditions: Catalyst FeNC-700, benzyl alcohol, and ammonia were added sequentially to a reaction vessel in a mass ratio of 0.1:1:2. After sealing, oxygen was introduced at 5 atm. The temperature was raised to 30-160℃, and the reaction was stirred and maintained at this temperature for 12 hours to obtain benzonitrile. After the reaction was completed, the reactor was allowed to cool naturally to room temperature.

[0054] Table 3. FeNC-700-catalyzed ammonia oxidation of benzyl alcohol at different reaction temperatures

[0055]

[0056] As shown in Table 3, the Fe-based catalyst (FeNC-700) in this invention exhibits the highest conversion rate of benzyl alcohol and yield of benzonitrile at a reaction temperature of 120℃.

[0057] Examples 27-36:

[0058] Reaction conditions: Catalyst FeNC-700, benzyl alcohol, and ammonia were added sequentially to a reaction vessel in a mass ratio of 0.1:1:2. After sealing, oxygen was introduced at 5 atm, and the temperature was raised to 120℃. The mixture was stirred and maintained at this temperature for 12 hours to obtain benzonitrile. After the reaction, the reactor was allowed to cool naturally to room temperature. The separated catalyst was repeatedly washed with ethanol and ethyl acetate and dried for reuse in the next catalytic cycle.

[0059] Table 4. Study on the recycling of FeNC-700 in the ammoxidation of benzyl alcohol to benzonitrile

[0060]

[0061] As shown in Table 4, the Fe-based catalyst (FeNC-700) provided by this invention still showed no significant deactivation after 10 cycles, and the conversion rate of benzyl alcohol and the yield of benzonitrile in the 10th reaction both reached 94%.

[0062] Examples 37-56:

[0063] Reaction conditions: Catalyst FeNC-700, aromatic alcohol, and ammonia were added sequentially to the reaction vessel in a mass ratio of 0.1:1:2. After sealing, 5 atm of oxygen was introduced, and the temperature was raised to 120℃. The mixture was stirred and maintained at this temperature for 12 hours to obtain the corresponding substituted aromatic nitrile. After the reaction was completed, the reactor was allowed to cool naturally to room temperature.

[0064] Table 5. Universality Study of FeNC-700 Catalyst

[0065]

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0067] Examples 57-58:

[0068] Following the same preparation method as in Example 1, except that the o-phenanthroline ligand was replaced with either melamine or 2-methylimidazole, these were designated as Examples 57-58. The molar ratio of ferrous chloride to the nitrogen-containing organic ligand was 1:2, and the remaining preparation methods were the same as in Example 1. The nitrogen-doped carbon-supported iron catalysts obtained in Examples 57-58 were named FeNC-700-MA and FeNC-700-2Mm, respectively.

[0069] Examples 59-61:

[0070] The nitrogen-doped carbon-supported iron catalysts prepared in Examples 1 and 57-58 were used for the ammoxidation of benzyl alcohol to synthesize benzonitrile.

[0071] Reaction conditions: 10 mg of catalyst, benzyl alcohol and ammonia water were added to the reaction vessel in a mass ratio of 0.1:1:2. After sealing, oxygen was introduced at 5 atm, the temperature was raised to 120℃, and the reaction was stirred for 12 h to obtain benzonitrile.

[0072] Table 6. Examples 59-61: Study on the ammonia oxidation performance of benzyl alcohol using different nitrogen-doped carbon-supported iron catalysts.

[0073]

[0074] Examples 62-67:

[0075] Following the same preparation method as in Example 1, except that the metallic iron salt FeCl2 was replaced with one of Fe(NO3)3, FeCl3, Fe2(SO4)3, Fe(NO3)2, FeSO4, and Fe(OAc)2, respectively, as Examples 62-67, the metallic iron salt and o-phenanthroline (C 12 The molar ratio of H8N2 was 1:2, and the remaining preparation methods were the same as in Example 1. The nitrogen-doped carbon-supported iron catalysts obtained in Examples 62-67 were named Fe, respectively. 3+ NC-700-NO3 2- Fe 3+ NC-700-Cl - Fe 3+ NC-700-SO4 2- Fe 2+ NC-700-NO3 2- Fe 2+ NC-700-SO4 2- Fe 2+ NC-700-OAc - .

[0076] Examples 68-74:

[0077] The nitrogen-doped carbon-supported iron catalysts prepared in Examples 1 and 62-67 were used for the ammoxidation of benzyl alcohol to synthesize benzonitrile.

[0078] Reaction conditions: 10 mg of catalyst, benzyl alcohol and ammonia water were added to the reaction vessel in a mass ratio of 0.1:1:2. After sealing, oxygen was introduced at 5 atm, the temperature was raised to 120℃, and the reaction was stirred for 12 h to obtain benzonitrile.

[0079] Table 7 Examples 68-74 Study on the ammonia oxidation performance of benzyl alcohol with different nitrogen-doped carbon-supported catalysts

[0080]

Claims

1. The application of a nitrogen-doped carbon-supported iron catalyst in the catalytic ammoxidation of aromatic alcohols to aromatic nitrile, characterized in that: 0.126 g of ferrous chloride and o-phenanthroline were added to 50 mL of ethanol, with a molar ratio of ferrous chloride to o-phenanthroline of 1:

2. After stirring for 1 hour, 2.5 g of nano-magnesium oxide with an average particle size of 20 nm was added as a template agent, and stirring was continued for 3 hours. After drying, the catalyst was pyrolyzed at 700 °C for 3 hours under a nitrogen atmosphere at a heating rate of 5 °C / min. Then, it was etched with 50 mL of 4 mol / L nitric acid aqueous solution for 120 min, washed, and dried to obtain nitrogen-doped carbon-supported iron catalyst. The nitrogen-doped carbon-supported iron catalyst, aromatic alcohol, and ammonia water are added to a reaction vessel, and oxygen or air is introduced to carry out an ammonia oxidation reaction to obtain aromatic nitrile. The mass ratio of nitrogen-doped carbon-supported iron catalyst, aromatic alcohol, and ammonia is (0.05~0.5):1:(1.25~10); the temperature of the ammonia oxidation reaction is 25~150℃, and the reaction time is 0.5~24h.

2. The application according to claim 1, characterized in that: The pressure of oxygen or air is 0.1~6MPa.

3. The application according to claim 1 or 2, characterized in that: The aromatic alcohol includes benzyl alcohol or one of formulas 1 to 8: 。

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