A nitrogen-silicon co-doped carbon-based iron catalyst and its preparation method and application

Abstract

The invention discloses a nitrogen-silicon co-doped carbon-based iron catalyst and a preparation method and application thereof. The nitrogen-silicon co-doped carbon-based iron catalyst uses a nitrogen-silicon co-doped carbon material as a carrier, and the carrier is loaded with an iron element, and the iron element exists in the form of iron single atoms, iron silicate and zero-valent iron at the same time. The preparation method can be that 2-methylimidazole, aniline, a water-soluble iron salt and zinc nitrate are formed into a mixed solution in water, tetraethyl silicate is added, mixed, centrifuged to obtain a solid, washed with water, dried, and then calcined under a protective atmosphere. Experiments show that the nitrogen-silicon co-doped carbon-based iron catalyst shows excellent catalytic performance for the synthesis of pyrrole and its derivatives, and is conducive to obtaining pyrrole and its derivatives with high efficiency and selectivity.

Description

Technical Field

[0001] The invention relates to a nitrogen-silicon co-doped carbon-based iron catalyst and a preparation method and application thereof. Background Art

[0002] Pyrrole is an important class of heterocyclic compounds and the core skeleton of various natural products and drug molecules. The common total synthesis method of drug molecules containing pyrrole rings requires hydrogenation of nitroaromatics to generate aniline, which is relatively cumbersome and does not conform to the green chemistry strategy; there is also a way to synthesize pyrrole compounds by reacting nitroaromatics and 1,4-diketone compounds through the Paal-Knorr synthesis method, but there are still defects such as low yield and low selectivity. Summary of the invention

[0003] The purpose of the present invention is to overcome one or more deficiencies of the prior art and to provide a novel nitrogen-silicon co-doped carbon-based iron catalyst for use in the synthesis of pyrrole and its derivatives. The catalyst exhibits excellent catalytic performance for the synthesis of pyrrole and its derivatives and is conducive to obtaining pyrrole and its derivatives with high efficiency and selectivity.

[0004] The present invention also provides the novel nitrogen-silicon co-doped carbon-based iron catalyst.

[0005] The present invention also provides a method for preparing the novel nitrogen-silicon co-doped carbon-based iron catalyst.

[0006] To achieve the above-mentioned purpose, a technical solution adopted by the present invention is: the use of a nitrogen-silicon co-doped carbon-based iron catalyst in the catalytic synthesis of pyrrole and its derivatives, the nitrogen-silicon co-doped carbon-based iron catalyst uses a nitrogen- and silicon-co-doped carbon material as a carrier, the carrier is loaded with iron elements, and the iron elements exist simultaneously in the form of single iron atoms, iron silicate and zero-valent iron.

[0007] According to some preferred aspects of the present invention, the application comprises: allowing nitroaromatic hydrocarbons, 2,5-hexanedione, an organic base, and formic acid to undergo a catalytic reaction in the presence of the nitrogen-silicon co-doped carbon-based iron catalyst to generate pyrrole and its derivatives.

[0008] Furthermore, the nitroaromatic hydrocarbon has a structure shown in formula (I): In formula (I), R 1 H, F, Cl, Br, I, C 1-6 Alkyl, halogenated C 1-6 Alkyl, cyano, nitro, C 1-6 Alkoxy, R 2 , R 3 are independently phenyl, C 1-6 Alkyl, halogenated C 1-6Alkyl, n is 0, 1, 2, 3 or 4;

[0009] or R 1 The benzene ring connected thereto forms a condensed ring sharing two carbon atoms.

[0010] The pyrrole and its derivatives have a structure shown in the following formula (II): In formula (II), R 1 and n are as defined in formula (I).

[0011] In some embodiments of the present invention, C 1-6 The alkyl group may be methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, etc. 1-6 The alkyl group may be methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, etc. substituted with one or more substituents selected from F, Cl, Br, and I. 1-6 The alkoxy group may be methoxy, ethoxy, propoxy or the like.

[0012] In some preferred and specific embodiments of the present invention, the nitroaromatic hydrocarbon is a combination of one or more selected from the following compounds:

[0013]

[0014] According to some preferred aspects of the present invention, the molar ratio of the nitroaromatic hydrocarbon, the 2,5-hexanedione, the organic base and the formic acid is 1:10-20:1-3:3-7.

[0015] According to some preferred aspects of the present invention, based on the molar amount of the nitroaromatic hydrocarbon, 60-100 mg of the nitrogen-silicon co-doped carbon-based iron catalyst is added for every 1 mmol of the nitroaromatic hydrocarbon.

[0016] According to some preferred aspects of the present invention, the organic base is a combination of one or more selected from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethylamine, pyridine, and morpholine.

[0017] According to some preferred aspects of the present invention, the catalytic reaction is carried out under heating conditions. In some preferred and specific embodiments of the present invention, the catalytic reaction is carried out at 90-110°C.

[0018] According to some preferred aspects of the present invention, the reaction time of the catalytic reaction is 20-30 hours.

[0019] According to some preferred aspects of the present invention, the preparation method of the nitrogen-silicon co-doped carbon-based iron catalyst includes: forming a mixed solution of 2-methylimidazole, aniline, a water-soluble iron salt and zinc nitrate in water, adding tetraethyl silicate, mixing, centrifuging to obtain a solid, washing with water, drying, and then calcining under a protective atmosphere, wherein the calcination is carried out at a calcination temperature of 850-1000°C.

[0020] Furthermore, the method for preparing the nitrogen-silicon co-doped carbon-based iron catalyst includes:

[0021] (1) 2-methylimidazole and aniline are mixed in water to form a solution A;

[0022] (2) mixing a water-soluble iron salt and zinc nitrate in water to form a solution B;

[0023] (3) adding the solution B obtained in step (2) to the solution A obtained in step (1), adding tetraethyl silicate, stirring, centrifuging to obtain a solid, washing with water, and drying;

[0024] (4) The solid obtained in step (3) is heated and pyrolyzed under a protective atmosphere to prepare the nitrogen-silicon co-doped carbon-based iron catalyst. This embodiment is more conducive to forming an ordered metal-organic framework material structure by controlling the order of adding materials to adjust the self-assembly process.

[0025] According to some preferred aspects of the present invention, the molar ratio of the 2-methylimidazole, the aniline, the water-soluble iron salt, the zinc nitrate and the tetraethyl silicate is 15-17:15-17:0.1-0.3:3-5:3-6.

[0026] According to some preferred aspects of the present invention, the water-soluble iron salt is a combination of one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, ferrous nitrate and ferric acetylacetonate.

[0027] According to the present invention, some of the above raw materials such as ferrous sulfate, zinc nitrate, etc. can be added in a state without crystal water or directly added in the form of raw materials containing crystal water. According to a specific aspect of the present invention, ferrous sulfate usually contains seven crystal waters, namely, FeSO 4 7H 2 O form, zinc nitrate usually contains six crystal water, as Zn(NO3) 2 6H 2 O form added.

[0028] According to some preferred aspects of the present invention, during the calcination process, the heating rate from room temperature to the calcination temperature is controlled to be 4-6°C / min.

[0029] According to some preferred aspects of the present invention, the calcination time is controlled to be 1-3 hours.

[0030] In some embodiments of the present invention, during the preparation of the nitrogen-silicon co-doped carbon-based iron catalyst, the protective gas selected for the protective atmosphere is nitrogen, argon, etc.

[0031] In some embodiments of the present invention, in step (3), stirring is performed at room temperature for 3-5 hours, and the drying temperature and time are 50-70° C. and 10-14 hours, respectively.

[0032] In some embodiments of the present invention, in step (4), the calcination is carried out in a tubular furnace.

[0033] According to the present invention, the nitrogen-silicon co-doped carbon-based iron catalyst is used in the catalytic synthesis of pyrrole and its derivatives, and can be recovered and reused after the reaction is completed, and can be reused multiple times without obvious attenuation of catalytic activity.

[0034] In the present invention, pyrrole and its derivatives are synthesized in a one-pot method using the catalyst of the present invention, which is more green and efficient, has good reusability, and is conducive to large-scale production.

[0035] Another technical solution provided by the present invention is a nitrogen-silicon co-doped carbon-based iron catalyst, wherein the nitrogen-silicon co-doped carbon-based iron catalyst uses a nitrogen-silicon co-doped carbon material as a carrier, and the carrier is loaded with iron elements, and the iron elements exist in the form of iron single atoms, iron silicate and zero-valent iron. In the present invention, the nitrogen-silicon co-doped carbon-based iron catalyst can be referred to as Fe@NSiC (wherein Fe represents the existence form of iron single atoms, iron silicate and zero-valent iron, and NSiC represents nitrogen-silicon co-doped carbon material).

[0036] According to some preferred aspects of the present invention, the iron silicate and the zero-valent iron are respectively present in the form of nanoparticles.

[0037] In the present invention, the nitrogen-silicon co-doped carbon-based iron catalyst is in the form of a nitrogen-silicon co-doped porous carbon-based iron catalyst.

[0038] In the present invention, the incorporation of Si is beneficial to improving the graphitization degree of the carbon material, the number of acid sites and the electron cloud density of the iron site, thereby promoting the reaction.

[0039] Another technical solution provided by the present invention is a method for preparing the nitrogen-silicon co-doped carbon-based iron catalyst described above, the method for preparing the nitrogen-silicon co-doped carbon-based iron catalyst comprising:

[0040] (1) 2-methylimidazole and aniline are mixed in water to form a solution A;

[0041] (2) mixing a water-soluble iron salt and zinc nitrate in water to form a solution B;

[0042] (3) adding the solution B obtained in step (2) to the solution A obtained in step (1), adding tetraethyl silicate and stirring to obtain a solid;

[0043] (4) heating and pyrolyzing the solid obtained in step (3) under a protective atmosphere to prepare the nitrogen-silicon co-doped carbon-based iron catalyst;

[0044] The calcination is carried out at a calcination temperature of 850-1000° C., and the molar ratio of the 2-methylimidazole, the aniline, the water-soluble iron salt, the zinc nitrate and the tetraethyl silicate is 15-17:15-17:0.1-0.3:3-5:3-6.

[0045] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0046] The present invention is based on the deficiencies in the prior art in the catalytic synthesis of pyrrole and its derivatives. After a large number of experimental studies, it is found that a nitrogen-silicon co-doped carbon-based iron catalyst is used, and a nitrogen-silicon doped carbon material is used as a carrier. The carrier is loaded with iron elements, and the iron elements exist simultaneously in the form of iron single atoms, iron silicate and zero-valent iron. When applied to the process of catalytic synthesis of pyrrole and its derivatives, pyrrole and its derivatives can be obtained efficiently and selectively, and the catalyst has good stability, good reusability, simple process, low requirements for raw materials, expanded the range of raw material options, and good substrate tolerance.

[0047] In addition, there are fewer wastes, the catalyst is cheap, low-toxic and easy to recycle, and it is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a SEM image of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention;

[0049] Figure 2 TEM image of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention;

[0050] Figure 3 This is the XRD pattern of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention;

[0051] Figure 4 This is the XPS graph (Fe 2P) of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention;

[0052] Figure 5 This is the XPS graph of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention (N 1S);

[0053] Figure 6 This is the XPS graph (Si 2P) of the nitrogen-silicon co-doped carbon-based iron catalyst prepared in Example 1 of the present invention;

[0054] Figure 7 is the H NMR spectrum of the product obtained in Example 4;

[0055] Figure 8 is the H NMR spectrum of the product obtained in Example 5;

[0056] Fig. 9 is the H NMR spectrum of the product obtained in Example 6;

[0057] Fig.10 is the H NMR spectrum of the product obtained in Example 7;

[0058] Fig.11 is the H NMR spectrum of the product obtained in Example 8;

[0059] Fig.12 is the H NMR spectrum of the product obtained in Example 9;

[0060] Fig.13 is the H NMR spectrum of the product obtained in Example 10;

[0061] Fig.14 is the H NMR spectrum of the product obtained in Example 11;

[0062] Fig.15 is the H NMR spectrum of the product obtained in Example 12;

[0063] Fig.16 is the H NMR spectrum of the product obtained in Example 13;

[0064] Fig.17 is the H NMR spectrum of the product obtained in Example 14;

[0065] Fig.18 is the H NMR spectrum of the product obtained in Example 15;

[0066] Fig.19 is the H NMR spectrum of the product obtained in Example 16;

[0067] Fig. 20 is the H NMR spectrum of the product obtained in Example 17;

[0068] Fig.21a is the H NMR spectrum of the product obtained in Example 18;

[0069] Figure 21b is the NMR carbon spectrum of the product obtained in Example 18;

[0070] Fig. 22 is the H NMR spectrum of the product obtained in Example 19;

[0071] Fig.23a is the H NMR spectrum of the product obtained in Example 20;

[0072] Figure 23b is the NMR carbon spectrum of the product obtained in Example 20;

[0073] Fig.24a is the H NMR spectrum of the product obtained in Example 21;

[0074] Figure 24b is the NMR carbon spectrum of the product obtained in Example 21;

[0075] Fig.25 is the H NMR spectrum of the product obtained in Example 22;

[0076] Fig.26 is the H NMR spectrum of the product obtained in Example 23;

[0077] Fig. 27 is the H NMR spectrum of the product obtained in Example 24;

[0078] Fig.28 is the H NMR spectrum of the product obtained in Example 25;

[0079] Fig.29 is the H NMR spectrum of the product obtained in Example 26;

[0080] Fig.30 is the H NMR spectrum of the product obtained in Example 27;

[0081] Fig.31a is the H NMR spectrum of the product obtained in Example 28;

[0082] Fig.31b This is the NMR carbon spectrum of the product obtained in Example 28. DETAILED DESCRIPTION

[0083] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0084] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0085] Ferrous sulfate heptahydrate (FeSO 4 7H 2 O, AR) and zinc nitrate hexahydrate (Zn(NO 3 ) 2 6H 2O, AR) were purchased from Sinopharm Chemical Reagent (Shanghai) Co., Ltd., with specifications of 500 g. Tetraethyl silicate (TEOS, AR) were purchased from Shanghai McLean Co., Ltd., China, with specifications of 100 mL. 2-Methylimidazole and aniline were purchased from Shanghai Aladdin Co., Ltd., China, with specifications of 100 g and 500 mL, respectively.

[0086] Example 1 Preparation of Fe@NSiC Catalyst

[0087] This example provides a method for preparing a nitrogen-silicon co-doped carbon-based iron catalyst, and the method for preparing a nitrogen-silicon co-doped carbon-based iron catalyst comprises the following steps:

[0088] (1) A certain ratio (1:1) of 2-methylimidazole (16 mmol) and aniline (16 mmol) were stirred in 40 mL of water to form solution A; a certain ratio (1:20) of FeSO 4 7H 2 O (0.2 mmol) and Zn (NO 3 ) 2 6H 2 O (4 mmol) was stirred in 40 mL of water to form solution B. Solution B was then added to solution A at room temperature, and tetraethyl silicate (4.5 mmol) was immediately added. Subsequently, the mixture was vigorously stirred at room temperature for 4 h, centrifuged, washed with water, and dried at 60 ° C for 12 h to obtain a solid powder.

[0089] (2) The solid powder obtained in step (1) was calcined in a tubular furnace at 900° C. for 2 h (heating rate of 5° C. / min) under a nitrogen atmosphere to obtain a final nitrogen-silicon co-doped carbon-based iron granular carbon material catalyst, i.e., a nitrogen-silicon co-doped carbon-based iron catalyst, denoted as Fe@NSiC (wherein Fe represents the form of iron single atoms, iron silicate and zero-valent iron, and NSiC represents nitrogen-silicon co-doped carbon material).

[0090] The obtained nitrogen-silicon co-doped carbon-based iron catalyst was tested as follows, and its SEM, TEM, XRD and XPS images are shown as follows: Figure 1 , Figure 2 , Figure 3 and Figure 4-6 shown.

[0091] The SEM image shows that Fe@NSiC is in amorphous form, generated by high-temperature carbonization of the ZIF structure, accompanied by the agglomeration of ZIF particles after carbonization, and a large number of carbon nanotube structures are formed;

[0092] The TEM image shows that there are some iron-based nanoparticles in the carbon material;

[0093] XRD patterns further confirmed the presence of zero-valent iron and iron silicate particles in Fe@NSiC;

[0094] The XPS images illustrate the possible valence states and coordination environments of iron, nitrogen and silicon elements.

[0095] Example 2 Preparation of Fe@NSiC Catalyst

[0096] The method is basically the same as Example 1, except that the ratio of 2-methylimidazole to aniline is adjusted to 1.2:1. The final catalyst is denoted as Fe@NSiC-MM.

[0097] Example 3 Preparation of Fe@NSiC Catalyst

[0098] The process is basically the same as Example 1, except that the calcination temperature in step (2) is adjusted to 950° C. The catalyst finally obtained is denoted as Fe@NSiC-HT.

[0099] Comparative Example 1

[0100] The method is basically the same as Example 1, except that tetraethyl silicate is not added. The specific steps are as follows:

[0101] (1) A certain ratio (1:1) of 2-methylimidazole (16 mmol) and aniline (16 mmol) were stirred in 40 mL of water to form solution A; a certain ratio (1:20) of FeSO 4 7H 2 O (0.2 mmol) and Zn (NO 3 ) 2 6H 2 O (4 mmol) was stirred in 40 mL of water to form solution B. Solution B was then added to solution A at room temperature, stirred vigorously for 4 h at room temperature, centrifuged, washed with water, and dried at 60 °C for 12 h to obtain a solid powder.

[0102] (2) The solid powder obtained in step (1) was calcined at 900° C. for 2 h in a tubular furnace under a nitrogen atmosphere (heating rate of 5° C. / min) to obtain the final catalyst, denoted as Fe@NC (wherein Fe represents the single atomic form of iron, and NC represents nitrogen-doped carbon material).

[0103] Comparative Example 2

[0104] The same as Example 1, except that the preparation method of CN is the same as that of Fe@NSiC, except that FeSO is not added during the preparation process. 4 7H 2 O, and the final catalyst is obtained, which is denoted as CN (representing nitrogen-doped carbon material).

[0105] Example 4-28 Preparation of pyrrole and its derivatives

[0106] A mixture of 0.5 mmol of nitroaromatic hydrocarbons, 0.9 mL of 2,5-hexanedione, 1.5 mmol of DBU and 5.0 mmol of formic acid, and 40 mg of Fe@NSiC prepared according to the method of Example 1 were added into a reaction vessel, sealed and heated to 100°C for 24 hours, and after the reaction was completed and cooled, the catalyst and the reaction liquid were centrifuged and the organic phase was removed by rotary evaporation to obtain a crude product. Finally, a pure product was obtained by simple silica gel column chromatography. The specific results are shown in Table 1.

[0107] Application Comparative Example 1

[0108] The method is basically the same as Example 4, except that the Fe@NSiC prepared in Example 1 is replaced by the catalyst Fe@NC prepared in Comparative Example 1. The specific results are shown in Table 1.

[0109] Application Comparative Example 2

[0110] The method is basically the same as Example 4, except that the "Fe@NSiC prepared in Example 1" is replaced by the catalyst CN prepared in Comparative Example 2. The specific results are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114]

[0115]

[0116] Figure 7 The product obtained in Example 4 H NMR spectrum of Figure 8 The product obtained in Example 5 H NMR spectrum of Fig. 9 The product obtained in Example 6 H NMR spectrum of Fig.10 The nucleus obtained in Example 7 H NMR spectrum of Fig.11 The product obtained in Example 8 H NMR spectrum of Fig.12 The product obtained in Example 9 H NMR spectrum of Fig.13 The product obtained in Example 10 H NMR spectrum of Fig.14 The product obtained in Example 11 H NMR spectrum of Fig.15 The product obtained in Example 12 H NMR spectrum of Fig.16 The product obtained in Example 13 H NMR spectrum of Fig.17 The product obtained in Example 14 H NMR spectrum of Fig.18 The product obtained in Example 15 H NMR spectrum of Fig.19 The product obtained in Example 16 H NMR spectrum of Fig. 20 The product obtained in Example 17 H NMR spectrum of Fig.21a The product obtained in Example 18 H NMR spectrum of Figure 21b The product obtained in Example 18 's NMR carbon spectrum; Fig. 22 The product obtained in Example 19 H NMR spectrum of Fig.23a The product obtained in Example 20 H NMR spectrum of Figure 23b The product obtained in Example 20 's NMR carbon spectrum; Fig.24a The product obtained in Example 21 H NMR spectrum of Figure 24b The product obtained in Example 21 's NMR carbon spectrum; Fig.25 The product obtained in Example 22 H NMR spectrum of Fig.26 The product obtained in Example 23 H NMR spectrum of Fig. 27 The product obtained in Example 24 H NMR spectrum of Fig.28 The product obtained in Example 25 H NMR spectrum of Fig.29 The product obtained in Example 26 H NMR spectrum of Fig.30 The product obtained in Example 27 H NMR spectrum of Fig.31a The product obtained in Example 28 H NMR spectrum of Fig.31b The product obtained in Example 28 's carbon NMR spectrum.

[0117] Embodiment 29

[0118] Nitroaromatic 0.5mmol, a mixture of 0.9mL 2,5-hexanedione, 1.5mmol DBU and 5.0mmol formic acid, and 40mg Fe@NSiC prepared according to the method of Example 2 were added into a reaction vessel, sealed and heated to 100°C for 24h. After the reaction was completed and cooled, the catalyst and the reaction liquid were separated by centrifugation, and the organic phase was removed by rotary evaporation to obtain a crude product. Finally, the pure product was obtained by simple silica gel column chromatography. The yield was 71% and the purity was 95.2%.

[0119] Embodiment 30

[0120] Nitroaromatic 0.5mmol, a mixture of 0.9mL 2,5-hexanedione, 1.5mmol DBU and 5.0mmol formic acid, and 40mg Fe@NSiC prepared according to the method of Example 3 were added into a reaction vessel, sealed and heated to 100°C for 24h. After the reaction was completed and cooled, the catalyst and the reaction liquid were separated by centrifugation, and the organic phase was removed by rotary evaporation to obtain a crude product. Finally, the pure product was obtained by simple silica gel column chromatography. The yield was 70% and the purity was 95.4%.

[0121] Example 31: Catalyst Reuse Activity Test

[0122] Nitrobenzene 0.5mmol, 0.9mL 2,5-hexanedione, 1.5mmol DBU, 5.0mmol formic acid, 40mg Fe@NSiC prepared in Example 1, 1mL water were added to the reaction vessel, sealed and heated to 100℃ for 12h (the reaction time of the recovery experiment was short, so the yield was low. The recovery effect under the condition of low yield can better illustrate the recyclability of the catalyst). After the reaction was completed and cooled, the catalyst and the reaction liquid were centrifuged and the reaction yield and selectivity were determined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The centrifuged Fe@NSiC was used as the catalyst for the next batch of the same reaction. The yields in the new and 1-5 times reactions were as follows: 51%, 51%, 44%, 35%, 36%, 38%, respectively, and the catalyst activity did not significantly decay.

[0123] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0124] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. Application of a nitrogen-silicon co-doped carbon-based iron catalyst in the catalytic synthesis of pyrrole derivatives, It is characterized in that The nitrogen-silicon co-doped carbon-based iron catalyst uses a nitrogen-silicon co-doped carbon material as a carrier, and the carrier is loaded with iron elements, and the iron elements exist in the form of iron single atoms, iron silicate and zero-valent iron at the same time; The preparation method of the nitrogen-silicon co-doped carbon-based iron catalyst comprises: forming a mixed solution of 2-methylimidazole, aniline, a water-soluble iron salt and zinc nitrate in water, adding tetraethyl silicate, mixing, centrifuging to obtain a solid, washing with water, drying, and then calcining under a protective atmosphere, wherein the calcination is carried out at a calcination temperature of 850-1000° C.; The water-soluble iron salt is a combination of one or more selected from ferrous sulfate, ferrous chloride, and ferrous nitrate; The application comprises: allowing nitroaromatic hydrocarbons, 2,5-hexanedione, an organic base, and formic acid to undergo a catalytic reaction in the presence of the nitrogen-silicon co-doped carbon-based iron catalyst to generate a pyrrole derivative; The nitroaromatic hydrocarbon has a structure shown in formula (I): In formula (I), R 1 H, F, Cl, Br, I, C 1-6 Alkyl, halogenated C 1-6 Alkyl, cyano, nitro, C 1-6 Alkoxy, R 2 , R 3 are independently phenyl, C 1-6 Alkyl, halogenated C 1-6 Alkyl, n is 0, 1, 2, 3 or 4; or, R 1 The benzene ring connected thereto forms a condensed ring sharing two carbon atoms. The pyrrole derivative has a structure shown in the following formula (II): In formula (II), R 1 and n is as defined in formula (I); The organic base is a combination of one or more selected from 1,8-diazabicyclo[5.4.0]undec-7-ene, triethylamine, pyridine and morpholine.

2. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 in catalytic synthesis of pyrrole derivatives, It is characterized in that The nitroaromatic hydrocarbon is a combination of one or more selected from the following compounds:

3. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 in catalytic synthesis of pyrrole derivatives, It is characterized in that The molar ratio of the nitroaromatic hydrocarbon, the 2,5-hexanedione, the organic base and the formic acid is 1:10-20:1-3:3-7; based on the molar amount of the nitroaromatic hydrocarbon, 60-100 mg of the nitrogen-silicon co-doped carbon-based iron catalyst is added for every 1 mmol of the nitroaromatic hydrocarbon.

4. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 in catalytic synthesis of pyrrole derivatives, It is characterized in that The catalytic reaction is carried out at 90-110° C.; and / or, the reaction time of the catalytic reaction is 20-30 hours.

5. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 in catalytic synthesis of pyrrole derivatives, It is characterized in that The embodiment of preparing the nitrogen-silicon co-doped carbon-based iron catalyst includes: (1) 2-methylimidazole and aniline are mixed in water to form a solution A; (2) mixing a water-soluble iron salt and zinc nitrate in water to form a solution B; (3) adding the solution B obtained in step (2) to the solution A obtained in step (1), adding tetraethyl silicate, stirring, centrifuging to obtain a solid, washing with water, and drying; (4) calcining the solid obtained in step (3) at a high temperature under a protective atmosphere to prepare the nitrogen-silicon co-doped carbon-based iron catalyst.

6. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 or 5 in catalytic synthesis of pyrrole derivatives, It is characterized in that The molar ratio of the 2-methylimidazole, the aniline, the water-soluble iron salt, the zinc nitrate and the tetraethyl silicate is 15-17:15-17:0.1-0.3:3-5:3-6.

7. Use of the nitrogen-silicon co-doped carbon-based iron catalyst according to claim 1 or 5 in catalytic synthesis of pyrrole derivatives, It is characterized in that During the calcination process, the heating rate from room temperature to the calcination temperature is controlled to be 4-6°C / min; and / or the calcination time is controlled to be 1-3h.

8. A nitrogen-silicon co-doped carbon-based iron catalyst, It is characterized in that The nitrogen-silicon co-doped carbon-based iron catalyst uses a nitrogen-silicon co-doped carbon material as a carrier, and the carrier is loaded with iron elements, and the iron elements exist in the form of iron single atoms, iron silicate and zero-valent iron at the same time; The preparation method of the nitrogen-silicon co-doped carbon-based iron catalyst comprises: (1) 2-methylimidazole and aniline are mixed in water to form a solution A; (2) mixing a water-soluble iron salt and zinc nitrate in water to form a solution B; (3) adding the solution B obtained in step (2) to the solution A obtained in step (1), adding tetraethyl silicate and stirring to obtain a solid; (4) calcining the solid obtained in step (3) at a high temperature under a protective atmosphere to prepare the nitrogen-silicon co-doped carbon-based iron catalyst; The calcination is carried out at a calcination temperature of 850-1000° C., the molar ratio of the 2-methylimidazole, the aniline, the water-soluble iron salt, the zinc nitrate and the tetraethyl silicate is 15-17:15-17:0.1-0.3:3-5:3-6, and the water-soluble iron salt is a combination of one or more selected from ferrous sulfate, ferrous chloride and ferrous nitrate.

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