A catalyst for synthesizing chloropyridine and its derivatives and a preparation method thereof

Abstract

The invention belongs to the field of preparation of catalysts, and specifically relates to a catalyst for synthesizing chloropyridine and its derivatives and a preparation method thereof. The preparation steps of the catalyst are as follows: (1) dissolving glucosamine and boric acid in deionized water, adding nano-alumina under stirring conditions, evaporating the water after dispersion, mixing the obtained solid with sodium carbonate and grinding it, calcining it under a nitrogen atmosphere, cooling it to room temperature, washing it to neutrality, and drying it to obtain a nitrogen-boron-doped carbon carrier; (2) dispersing the nitrogen-boron-doped carbon carrier in a hydrochloric acid aqueous solution, adding a metal salt thereto, stirring it to dryness at 75-100° C. after ultrasonication, cooling it to room temperature, and obtaining a black solid; (3) heating the black solid to 300-350° C. under a hydrogen atmosphere, keeping it warm, and cooling it to room temperature under a hydrogen atmosphere to obtain a catalyst for synthesizing chloropyridine and its derivatives. The catalyst has high activity and stability, and has a good catalytic effect on the generation of chloropyridine and its derivatives.

Description

Technical Field

[0001] The invention belongs to the field of catalyst preparation, and specifically relates to a catalyst for synthesizing chloropyridine and its derivatives and a preparation method thereof. Background Art

[0002] The pyridine ring is a type of heterocyclic structure with significant biological activity. Compounds formed by the pyridine ring have been widely used in the fields of agriculture and medicine, such as pesticides, antibacterial agents, fungicides, plant growth regulators, anticancer drugs, etc. Pyridine derivatives are also an important class of fine chemical intermediates. Through chlorination or fluorination, a variety of pesticides and insecticides can be produced, such as 2-chloro-5-methylpyridine, 2-chloro-3-methylpyridine, 2-chloro-3-trichloromethylpyridine, 2-chloro-5-trichloromethylpyridine, etc. At present, the methods for synthesizing chloropyridine and its derivatives in China include: catalytic chlorination, oxidative chlorination and benzylamine cyclization, but these methods still have certain defects. The catalyst cost of the catalytic chlorination method is high and difficult to recover; the oxidative chlorination method is difficult to separate the pure product and has safety hazards; and the benzylamine cyclization method has a long process flow, high raw material production cost, and difficulty in separating benzyl chloride.

[0003] In recent years, some scholars have also studied the synthesis method of chloropyridine and its derivatives. Patent CN106632006A discloses a synthesis method of a heterocyclic compound 3-methoxypyridine, comprising the following steps: putting raw materials 3-halopyridine, hydrogen peroxide and acetic acid into a three-necked flask, reacting at 40-80°C for 4-8h under stirring conditions, recovering acetic acid, adding a saturated sodium carbonate solution and stirring to make the system alkaline, evaporating water, adding chloroform for washing, and vacuum distilling to obtain N-oxide-3-halopyridine; adding 3-halopyridine-N-oxide, metal salt of alkyl alcohol, catalyst and alcohol into a three-necked flask respectively, reflux reaction for 5-8h under stirring conditions, cooling, neutralizing to neutrality, and distilling to obtain N-oxide-3-alkoxypyridine; adding N-oxide-3-alkoxypyridine, ferric chloride, hydrazine hydrate, activated carbon and ethanol into a three-necked flask respectively, reacting at 70°C for 3h, cooling to room temperature, and vacuum distilling to obtain 3-methoxypyridine. Although the invention has a high intermediate conversion rate, mild reaction conditions, safe operation, and cheap and readily available raw materials, the production operation of 3-methoxypyridine in the invention is relatively complicated and is not conducive to expanding production.

[0004] Therefore, developing a catalyst for the synthesis of chloropyridine and its derivatives that is low in cost, simple to operate, has high stability and catalytic activity, and can reduce waste in the production process is of great significance for further expanding the application range of pyridine and its derivatives. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a catalyst for the synthesis of chloropyridine and its derivatives and a preparation method thereof. The present invention uses a nitrogen-doped carbon material developed as a carrier, and uses iron salt, copper salt and palladium salt as active ingredients. The nitrogen atoms in the carrier are used to change the electrical properties, acidity and alkalinity of the material and the interaction between the carrier and metal, thereby improving the activity and stability of the catalyst, so that the catalyst has a better catalytic conversion rate for chloropyridine and its derivatives.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0008] (1) dissolving glucosamine and boric acid in deionized water, adding nano-alumina under stirring conditions, evaporating the water after dispersion, mixing the obtained solid with sodium carbonate and grinding it, calcining it under a nitrogen atmosphere, cooling it to room temperature after calcination, washing it to neutrality, and drying it to obtain a nitrogen-boron doped carbon carrier;

[0009] (2) dispersing the nitrogen-boron-doped carbon support obtained in step (1) in an aqueous hydrochloric acid solution under ultrasonic conditions, adding a metal salt thereto, continuing ultrasonication for 10-20 minutes, stirring at 75-100° C. until dry, and cooling to room temperature to obtain a black solid;

[0010] (3) The black solid obtained in step (2) is heated to 300-350° C. in a hydrogen atmosphere. After the heat preservation is completed, the solid is cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0011] In some embodiments, the nano-alumina is γ-Al2O3, and its average particle size is 10-50 nm.

[0012] Preferably, the nano-alumina is γ-Al2O3, and its average particle size is 20-30 nm.

[0013] In some embodiments, the mass ratio of glucosamine, boric acid and nano-alumina in step (1) is (2-3):(1-2):1.

[0014] In some embodiments, the mass ratio of solid to sodium carbonate in step (1) is 1:(1-5).

[0015] Preferably, in step (1), the mass ratio of solid to sodium carbonate is 1:3.5.

[0016] In some embodiments, the heating rate of calcination in step (1) is 5-10°C / min, the calcination temperature is 650-950°C, and the calcination time is 1-3h.

[0017] Preferably, the heating rate of calcination in step (1) is 7.5°C / min, the calcination temperature is 800°C, and the calcination time is 2h.

[0018] In some embodiments, the metal salt in step (2) includes iron salt, copper salt and palladium salt in a molar ratio of iron, copper and palladium of (5-10):(4-8):1.

[0019] Preferably, the metal salt in step (2) comprises iron salt, copper salt and palladium salt in a molar ratio of 8:6:1 among iron, copper and palladium.

[0020] Further preferably, the iron salt is selected from ferric iron and / or ferrous iron salts; and the copper salt is selected from divalent copper and / or cuprous copper salts.

[0021] In some embodiments, the metal salt is used in an amount of 1-5 wt % of the nitrogen-boron doped carbon support.

[0022] Preferably, the amount of the metal salt used is 2.8 wt % of the nitrogen-boron doped carbon support.

[0023] In some embodiments, the heating rate in step (3) is 4-7°C / min, and the heating is maintained for 1-2h.

[0024] Preferably, the heating rate in step (3) is 5°C / min and the temperature is kept for 1.5h.

[0025] The second aspect of the present invention provides a catalyst for synthesizing chloropyridine and its derivatives prepared by the above preparation method.

[0026] In some embodiments, the catalyst described above is used to catalyze the synthesis of chloropyridine and its derivatives, and the product conversion rate can reach more than 85%.

[0027] The present invention adopts biomass derivative amino glucose as carbon source and nitrogen source, boric acid as boron source, nano alumina as hard template, and after being fully mixed with sodium carbonate, calcined at high temperature, a nitrogen-boron doped carbon carrier with a certain nitrogen content and high porosity is obtained, the carrier has the excellent performance of activated carbon material and the alkaline characteristics and catalytic performance of alumina, and the activated carbon material obtained by calcining amino glucose can also be a protective layer of the alumina aqueous phase system, thereby improving the stability of the carrier. Subsequently, an active metal salt is loaded on the carrier to obtain a catalyst with high catalytic performance and for the synthesis of chloropyridine and its derivatives, which can efficiently activate chlorine and promote the transfer of chlorine atoms, thereby realizing the chlorination reaction on the pyridine molecule. The active metal salt used in the present invention is loaded on the carrier to form active centers, which can interact with chlorine and pyridine molecules, reduce the activation energy of the reaction, and improve the reaction rate and selectivity.

[0028] In the present invention, nitrogen atoms and boron atoms are introduced into the catalyst carrier, and BC bonds, CN bonds and BN bonds can be formed under the condition of high temperature calcination, which can regulate the electronic structure of the carbon material itself, so that the active metals (iron, copper and palladium) interacting with it can be promoted to play a role, greatly improving the activation and catalytic effect of the catalyst in actual use. Due to the electronegativity of nitrogen atoms and boron atoms themselves, a unique coupling can be generated between N and B atoms in the nitrogen and boron-doped carbon carrier to establish a new electronic structure, and then the carrier electron cloud density can be enhanced, the adsorption energy of the substrate at the catalytic site is reduced, and the reaction selectivity is improved. In addition, the coordination ability of nitrogen atoms with iron, copper and palladium can disperse metal ions well, reduce metal loss, and improve the activity and stability of the catalyst.

[0029] In addition, γ-Al2O3 is selected as a hard template in the preparation process of nitrogen-boron-doped carbon carriers. On the one hand, γ-Al2O3 itself has a certain porosity and catalytic ability. It is used in the catalyst together with nitrogen-boron-doped carbon carriers and active metals, and by regulating the usage of the three, they can synergistically exert excellent catalytic effects. On the other hand, it can provide more attachment sites for iron, copper and palladium. After hydrothermal treatment and calcination, iron, copper and palladium can be more stably attached to the nitrogen-boron-doped carbon carrier, making the catalyst have good stability.

[0030] Finally, the present invention selects sodium carbonate as an activator, and calcining it together with amino glucose can obtain a nitrogen-boron-doped carbon carrier with abundant pores, which is beneficial to improving the catalytic performance of the catalyst. This is because the nitrogen-containing molecules generated by the decomposition of amino glucose during the calcination process will also react with the carbon to achieve the purpose of nitrogen doping; sodium carbonate and amino glucose can release gas during the heating process, so that many macropores are formed in the carrier; sodium carbonate can also etch the carbon material obtained by high-temperature carbonization of amino glucose during the calcination process, generating a certain number of micropores and mesopores.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention uses biomass derivative amino glucose as a carbon source and a nitrogen source, boric acid as a boron source, and nano-alumina as a hard template, and after being fully mixed with sodium carbonate, calcined at a high temperature to obtain a nitrogen-boron doped carbon carrier with high porosity, and then an active metal salt is loaded on the carrier to obtain a catalyst with high catalytic performance for the synthesis of chloropyridine and its derivatives.

[0033] 2. In the present invention, γ-Al2O3 is selected as a hard template in the preparation process of nitrogen-boron-doped carbon carrier. The prepared nitrogen-boron-doped carbon carrier can provide more attachment sites for iron, copper and palladium. After hydrothermal and calcination, iron, copper and palladium can be better attached to the nitrogen-boron-doped carbon carrier, so that the catalyst has good stability.

[0034] 3. The present invention selects sodium carbonate as an activator, and calcining it together with amino glucose can obtain a nitrogen-boron-doped carbon carrier with abundant pores, which is beneficial to improving the catalytic performance of the catalyst. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] In order to better illustrate the specific implementation mode of the present invention, further examples are given below.

[0037] The nano-alumina used in the present invention is γ-Al2O3 with an average particle size of 20 nm, and the nano-magnesium oxide used has an average particle size of 20 nm.

[0038] Example 1

[0039] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0040] (1) 2 g of glucosamine and 1 g of boric acid were dissolved in 30 mL of deionized water, 1 g of nano-alumina was added under stirring at 150 r / min, and the water was evaporated to dryness at 120° C. after being fully dispersed, and then 2 g of the obtained solid was mixed with 2 g of sodium carbonate and ground to pass through an 80-mesh sieve, and then heated to 650° C. in a nitrogen atmosphere at a heating rate of 5° C. / min, calcined for 3 h, cooled to room temperature, washed with deionized water until neutral, and dried at 100° C. to constant weight to obtain a nitrogen-boron-doped carbon carrier;

[0041] (2) dispersing 1 g of the nitrogen-boron-doped carbon support obtained in step (1) in 20 mL of 1.5 wt% hydrochloric acid aqueous solution under 30 KHz ultrasonic conditions, adding 0.01 g of metal salt thereto, continuing ultrasonication for 10 min, stirring at 75° C. until dry, and cooling to room temperature to obtain a black solid;

[0042] (3) The black solid obtained in step (2) was heated to 300° C. at 4° C. / min in a hydrogen atmosphere, kept at this temperature for 2 h, and cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0043] The metal salts used include ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 5:4:1 among iron, copper and palladium.

[0044] Example 2

[0045] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0046] (1) 3 g of glucosamine and 2 g of boric acid were dissolved in 30 mL of deionized water, 1 g of nano-alumina was added under stirring at 150 r / min, and the water was evaporated to dryness at 120° C. after being fully dispersed, and then 2 g of the obtained solid was mixed with 10 g of sodium carbonate and ground to pass through an 80-mesh sieve, and then heated to 950° C. in a nitrogen atmosphere at a heating rate of 10° C. / min, calcined for 1 h, cooled to room temperature, washed with deionized water until neutral, and dried at 100° C. to constant weight to obtain a nitrogen-boron-doped carbon carrier;

[0047] (2) dispersing 1 g of the nitrogen-boron-doped carbon support obtained in step (1) in 20 mL of 1.5 wt% hydrochloric acid aqueous solution under 30 KHz ultrasonic conditions, adding 0.05 g of metal salt thereto, continuing ultrasonication for 15 min, stirring at 100° C. until dry, and cooling to room temperature to obtain a black solid;

[0048] (3) The black solid obtained in step (2) was heated to 350° C. at 7° C. / min in a hydrogen atmosphere, kept at this temperature for 1 h, and cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0049] The metal salts used include ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 10:8:1 among iron, copper and palladium.

[0050] Example 3

[0051] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0052] (1) 2.5 g of glucosamine and 1.5 g of boric acid were dissolved in 30 mL of deionized water, 1 g of nano-alumina was added under stirring at 150 r / min, and the water was evaporated to dryness at 120° C. after being fully dispersed, and then 2 g of the obtained solid was mixed with 7 g of sodium carbonate and ground to pass through an 80-mesh sieve, and then heated to 800° C. in a nitrogen atmosphere at a heating rate of 7.5° C. / min, calcined for 2 h, cooled to room temperature, washed with deionized water until neutral, and dried at 100° C. to constant weight to obtain a nitrogen-boron-doped carbon carrier;

[0053] (2) dispersing 1 g of the nitrogen-boron-doped carbon support obtained in step (1) in 20 mL of 1.5 wt% hydrochloric acid aqueous solution under 30 KHz ultrasonic conditions, adding 0.028 g of metal salt thereto, continuing ultrasonication for 15 min, stirring at 90° C. until dry, and cooling to room temperature to obtain a black solid;

[0054] (3) The black solid obtained in step (2) was heated to 325° C. at 5° C. / min in a hydrogen atmosphere, kept at this temperature for 1.5 h, and cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0055] The metal salts used include ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 8:6:1 among iron, copper and palladium.

[0056] Example 4

[0057] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that the metal salt used includes ferric chloride and cuprous chloride in a molar ratio of iron to copper of 4:3.

[0058] Example 5

[0059] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that the metal salt used includes ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 2:2:1 among iron, copper and palladium.

[0060] Example 6

[0061] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that the amount of metal salt used is 0.06g.

[0062] Example 7

[0063] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that 1.5 g of glucosamine is used.

[0064] Comparative Example 1

[0065] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0066] (1) 2.5 g of glucosamine and 1.5 g of boric acid were dissolved in 30 mL of deionized water, 1 g of nano-alumina was added under stirring at 150 r / min, the water was evaporated to dryness at 120° C. after being fully dispersed, and the obtained solid was ground to pass through an 80-mesh sieve, and then heated to 800° C. in a nitrogen atmosphere at a heating rate of 7.5° C. / min, calcined for 2 h, cooled to room temperature, washed with deionized water until neutral, and dried at 100° C. to constant weight to obtain a nitrogen-boron doped carbon carrier;

[0067] (2) dispersing 1 g of the nitrogen-boron-doped carbon support obtained in step (1) in a 1.5 wt% hydrochloric acid aqueous solution under 30 KHz ultrasonic conditions, adding 0.028 g of a metal salt thereto, continuing ultrasonication for 15 min, stirring at 90° C. until dry, and cooling to room temperature to obtain a black solid;

[0068] (3) The black solid obtained in step (2) was heated to 325° C. at 5° C. / min in a hydrogen atmosphere, kept at this temperature for 1.5 h, and cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0069] The metal salts used include ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 8:6:1 among iron, copper and palladium.

[0070] Comparative Example 2

[0071] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, comprising the following preparation steps:

[0072] (1) heating nano-alumina to 800° C. at a heating rate of 7.5° C. / min under a nitrogen atmosphere, calcining for 2 h, cooling to room temperature, washing with deionized water to neutrality, and drying at 100° C. to constant weight to obtain an alumina carrier;

[0073] (2) dispersing 1 g of the alumina support obtained in step (1) in 20 mL of 1.5 wt % hydrochloric acid aqueous solution under 30 kHz ultrasonic conditions, adding 0.028 g of a metal salt thereto, continuing ultrasonication for 15 min, stirring at 90° C. until dry, and cooling to room temperature to obtain a solid;

[0074] (3) The solid of step (2) was heated to 325° C. at 5° C. / min in a hydrogen atmosphere, kept warm for 1.5 h, and cooled to room temperature in a hydrogen atmosphere to obtain a catalyst for the synthesis of chloropyridine and its derivatives.

[0075] The metal salts used include ferric chloride, cuprous chloride and palladium chloride in a molar ratio of 8:6:1 among iron, copper and palladium.

[0076] Comparative Example 3

[0077] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that an equal mass of nano-magnesium oxide is used instead of nano-aluminum oxide.

[0078] Comparative Example 4

[0079] A method for preparing a catalyst for synthesizing chloropyridine and its derivatives, the specific implementation method is the same as that of Example 3, except that boric acid is not added in step (1).

[0080] Catalyst performance testing

[0081] 1. Catalytic performance: The catalytic performance of the catalysts prepared in the examples and comparative examples was tested: 10 g of 3-methylpyridine, 0.1 g of catalyst, and 100 mL of 2,4,6-trichlorotrifluorotoluene were added to a flask, nitrogen was introduced for 10 min under stirring at 150 r / min, and then heated to 110° C., chlorine was introduced, and heating was stopped after the reaction for 5 h. After the reaction solution was gradually cooled, 15 wt % sodium hydroxide aqueous solution was added dropwise to adjust the pH to 8, and the mixture was allowed to stand for 1 h. After stratification, the organic phase was taken and the product and conversion rate were analyzed on HPLC. The specific test results are shown in Table 1;

[0082] The parameters of HPLC (Waters 1525) are as follows: chromatographic column ( Columns: 150 mm length × 4.6 mm id, 5 μm particle size), the mobile phase was a mixture of acetonitrile: methanol: 0.5 v / v% acetic acid aqueous solution = 2:3:5, the injection volume was 20 μL, the injection temperature was 30 °C, and the flow rate was 1 mL min -1 The standard curve was determined by isocratic elution and external standard method for quantitative calculation of reactants and products.

[0083] Stability: The catalysts obtained in Examples 2 and 3 were selected for life test. The experimental operation was the same as that in Performance Test 1. When the conversion rate of 3-methylpyridine was less than 50%, the experiment was stopped. The specific test results are shown in Table 2.

[0084] Table 1

[0085]

[0086] Table 2

[0087] serial number Lifespan (h) Example 2 1725 Example 3 1730

[0088] As can be seen from Table 1, the catalysts prepared in Examples 1-3 have a good catalytic effect on the conversion of 3-methylpyridine to chloropyridine, especially the catalyst obtained in Example 3, which enables the 3-methylpyridine conversion rate to reach 89.9% and inhibits the occurrence of side reactions to a certain extent.

[0089] In Examples 4-6, the preparation conditions of the catalyst (composition and dosage of the metal salt) were changed, the interaction between the active ingredient of the catalyst and the carrier metal was changed, the catalytic performance was affected, and the conversion rate of 3-methylpyridine was reduced; in Example 7, the dosage of glucosamine was changed, the nitrogen content in the catalyst carrier was changed, the acidity and alkalinity of the catalyst and the interaction between the carrier metal were changed, the activity and stability of the catalyst were reduced, and the conversion rate of 3-methylpyridine was also reduced.

[0090] In Comparative Example 1, sodium carbonate was not used in the preparation process of the nitrogen-boron-doped carbon support used, so a large number of micropores and mesopores could not be formed during the calcination process, and the adhesion of the metal salt would be affected, thereby weakening the catalytic performance of the catalyst; in Comparative Example 2, glucosamine was not used in the preparation process of the nitrogen-boron-doped carbon support used, and the catalyst lacked carbon and nitrogen elements, which significantly reduced the catalyst's promoting effect on the conversion rate of 3-methylpyridine; in Comparative Example 3, nano-magnesium oxide was used instead of nano-aluminum oxide, and the pores in the prepared nitrogen-boron-doped carbon support changed, the attachment sites of the metal salt were reduced, and the catalytic performance of the catalyst was weakened; in Comparative Example 4, boric acid was added in the preparation of the carbon support, and the lack of boron element made it impossible to form BC bonds, thereby affecting the catalytic effect of the catalyst.

[0091] It can be seen from Table 2 that the catalysts prepared in Examples 2 and 3 have a longer service life, indicating that their stability is also good.

[0092] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for preparing a catalyst for the synthesis of chloropyridine and its derivatives, characterized in that: The method comprises the following preparation steps: (1) dissolving glucosamine and boric acid in deionized water, adding nano-alumina under stirring conditions, evaporating the water after dispersion, mixing the obtained solid with sodium carbonate and grinding it, calcining it under a nitrogen atmosphere, cooling it to room temperature after calcination, washing it to neutrality, and drying it to obtain a nitrogen-boron doped carbon carrier; (2) dispersing the nitrogen-boron-doped carbon support obtained in step (1) in an aqueous hydrochloric acid solution under ultrasonic conditions, adding a metal salt thereto, continuing ultrasonication for 10-20 minutes, stirring at 75-100° C. until dry, and cooling to room temperature to obtain a black solid; (3) heating the black solid obtained in step (2) to 300-350° C. in a hydrogen atmosphere, and cooling to room temperature in a hydrogen atmosphere after the heat preservation is completed to obtain a catalyst for the synthesis of chloropyridine and its derivatives; The metal salt in step (2) comprises an iron salt, a copper salt and a palladium salt in a molar ratio of (5-10):(4-8):1 among iron, copper and palladium; The usage amount of the metal salt is 1-5 wt % of the nitrogen-boron doped carbon support.

2. The method for preparing the catalyst according to claim 1, characterized in that: The nano-alumina is γ-Al2O3, and its average particle size is 10-50nm.

3. The method for preparing the catalyst according to claim 2, characterized in that: In the step (1), the mass ratio of glucosamine, boric acid and nano-alumina is (2-3):(1-2):

1.

4. The method for preparing the catalyst according to claim 1, characterized in that: The mass ratio of solid to sodium carbonate in the step (1) is 1:(1-5).

5. The method for preparing the catalyst according to claim 1, characterized in that: In the step (1), the heating rate of calcination is 5-10°C / min, the calcination temperature is 650-950°C, and the calcination time is 1-3h.

6. The method for preparing the catalyst according to claim 1, characterized in that: The heating rate in step (3) is 4-7°C / min, and the temperature is kept for 1-2h.

7. A catalyst for synthesizing chloropyridine and its derivatives prepared by the preparation method according to any one of claims 1 to 6.

8. The catalyst according to claim 7, characterized in that The catalyst is used to catalyze the synthesis of chloropyridine and its derivatives, and the product conversion rate reaches more than 85%.

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