Catalyst for preparing pyridylaldehyde as well as preparation method and application of catalyst

Abstract

The invention relates to a catalyst for preparing pyridylaldehyde as well as a preparation method and application of the catalyst, and belongs to the technical field of pyridylaldehyde preparation. The catalyst lithium chloride is loaded on the magnetic ball-milled silicon carbide carrier under proper conditions, the catalytic advantage of the lithium chloride is successfully combined with the rapid separation advantage of the magnetic ball-milled silicon carbide carrier, so that the catalyst lithium chloride can be recycled and reused, and the loaded lithium chloride still keeps very high catalytic activity; the environmental pollution is greatly reduced, the subsequent separation and purification of the product are simpler, and high-purity 2-pyridylaldehyde can be obtained through catalysis.

Description

Technical Field

[0001] The invention relates to a catalyst for preparing pyridinecarboxaldehyde, a preparation method and application thereof, and belongs to the technical field of pyridinecarboxaldehyde preparation. Background Art

[0002] At present, pyridine carboxaldehyde can be used as an important intermediate in the synthesis of pyridine functional group derivatives, and has a wide range of uses in the fields of medicine and chemical industry. For example, 2-pyridine carboxaldehyde derivatives can be used to synthesize some Schiff base ligands with specific uses. The synthesis methods of pyridine carboxaldehyde are mainly oxidation methods using methanol pyridine as raw materials, oxidation methods using methyl pyridine as raw materials, oxidation methods using vinyl pyridine as raw materials, and reduction methods using picolinate as raw materials. These methods have their own characteristics and are applied to actual production and scientific research. However, they still have some shortcomings, such as drastic reaction conditions such as high temperature and pressure, the need to use precious metal catalysts, and low yields of some reactions.

[0003] In view of the above-mentioned defects, the designers actively carried out research and innovation in order to create a catalyst for preparing pyridine carboxaldehyde and its preparation method and application, so as to make it more valuable for industrial use. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a catalyst for preparing pyridine carboxaldehyde and a preparation method and application thereof.

[0005] A catalyst for preparing pyridine carboxaldehyde of the present invention comprises a catalyst carrier and a catalyst effective component;

[0006] The catalyst carrier is a magnetic ball-milled silicon carbide carrier;

[0007] The active ingredient of the catalyst is lithium chloride;

[0008] The magnetic ball-milled silicon carbide carrier is prepared by mixing and granulating silicon carbide powder, kaolin, boron carbide, polyethylene glycol 6000 and phenolic resin, sintering at high temperature, ball-milling, heating and reacting with deionized water, ferrous sulfate, ferric chloride and polyacrylamide, and finally precipitating with sodium hydroxide solution.

[0009] A method for preparing a catalyst for preparing pyridinecarboxaldehyde, the specific preparation steps are:

[0010] A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 4000-5000 and a magnetic ball-milled silicon carbide carrier are fully stirred and mixed at a mass ratio of 100:1:500, and then dried at 100-120°C for 2-4h and ground to obtain a catalyst for preparing pyridine carboxaldehyde.

[0011] Furthermore, the preparation steps of the magnetic ball-milled silicon carbide carrier are:

[0012] (1) mixing the ball-milled silicon carbide carrier and deionized water, ferrous sulfate, ferric chloride and polyacrylamide in a mass ratio of 5:200:1:2:2, pouring into a reaction kettle and heating to 60-70° C., stirring for 40-60 min, then introducing nitrogen into the reaction kettle, heating in a water bath to 60-80° C., stirring for 10-15 min, and obtaining a mixed solution;

[0013] (2) Add a 30% sodium hydroxide solution to the mixed solution, adjust the pH to 8-11, continue stirring at 80-90°C for 2-3 hours, cool to room temperature and age for 2-3 hours, filter to obtain a precipitate, rinse the precipitate with deionized water and anhydrous ethanol for 2-3 times, move it into a constant temperature drying oven and dry it at 70-80°C for 12-18 hours to obtain a magnetic ball-milled silicon carbide carrier.

[0014] Furthermore, the preparation steps of the ball-milled silicon carbide carrier are:

[0015] (1) Weigh 90-100 parts by weight of silicon carbide powder with a particle size of 1-2 μm, 10-15 parts of kaolin, 1-2 parts of boron carbide, 5-10 parts of polyethylene glycol 6000, 5-10 parts of phenolic resin, and 1-2 parts of cellulose acetate, stir and mix for 20-30 minutes, and then extrude and granulate to obtain a carrier particle body with a particle size of 1-2 mm;

[0016] (2) The carrier particle green body is placed in a vacuum hot pressing sintering furnace for sintering. First, the temperature is slowly raised from room temperature to 700°C and kept at this temperature for 40 minutes; then the temperature is raised to 1800°C, and argon is introduced at about 1400°C, and the atmosphere pressure is maintained at 0.06MPa; finally, the temperature is quickly raised to 2000°C, and after keeping at this temperature for 45 minutes, the furnace is closed and cooled naturally. After the material is discharged, it is placed in a rolling ball mill and ball-milled at a speed of 15r / min for 12 to 15 hours to obtain a ball-milled silicon carbide carrier.

[0017] The application of the catalyst for preparing pyridine carboxaldehyde is used to prepare 2-pyridine carboxaldehyde, and the specific preparation steps are:

[0018] (1) by weight, under the protection of argon, add 40-50 parts of 2-bromopyridine and 60-70 parts of tetrahydrofuran to a reaction kettle, lower the temperature of the reaction system to 15-20° C. in an ice-water bath, dropwise add 44-50 parts of a tetrahydrofuran solution of isopropylmagnesium chloride, and then add 2-3 parts of a magnetic lithium chloride solid acid catalyst, and react completely to obtain a yellow opaque system;

[0019] (2) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 40 to 50 parts by mass of a 10% hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 8 to 9. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.

[0020] By means of the above scheme, the present invention has at least the following advantages:

[0021] (1) The present invention obtains a porous silicon carbide carrier with a huge specific surface area by sintering and forming pores in silicon carbide, and assisted by rolling ball milling, so that the curvature between the surface and the curved surface of the silicon carbide carrier is reduced, thereby increasing the catalyst loading at the chamfer and improving the catalytic effect;

[0022] (2) The catalyst lithium chloride used in the present invention can most effectively accelerate the exchange reaction rate of halogen ions and magnesium ions. At the same reaction temperature and time, the reaction conversion rate can be increased from 18% to 84%. Under appropriate conditions, the catalyst lithium chloride is loaded on the magnetic ball-milled silicon carbide carrier, successfully combining the catalytic advantage of lithium chloride with the rapid separation advantage of the magnetic ball-milled silicon carbide carrier, so that the catalyst lithium chloride can be recovered and reused. The loaded lithium chloride still maintains a high catalytic activity, greatly reducing environmental pollution and making the subsequent separation of the product Purification is simpler, and high-purity 2-pyridinecarboxaldehyde can be obtained by catalysis. The invention uses 2-bromopyridine or 3-bromopyridine as a raw material, uses a Grignard reagent exchange method to prepare a 2-pyridine Grignard reagent and a 3-pyridine Grignard reagent, reacts with DMF to prepare 2-pyridinecarboxaldehyde and 3-pyridinecarboxaldehyde, uses supported active lithium chloride as a catalyst, and reacts under suitable conditions to obtain 2-pyridinecarboxaldehyde. The reaction yield is high, the catalyst can be recycled by a magnetic sedimentation method, the lithium chloride can be recycled and reused, the obtained product has high purity, no catalyst residue is in the reaction product, the reaction cost is low, and the benefit is high.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. DETAILED DESCRIPTION

[0024] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] (1) Weighing 90-100 parts by weight of silicon carbide powder with a particle size of 1-2 μm, 10-15 parts of kaolin, 1-2 parts of boron carbide, 5-10 parts of polyethylene glycol 6000, 5-10 parts of phenolic resin, and 1-2 parts of ammonium bicarbonate, stirring and mixing for 20-30 minutes, and then extruding and granulating to obtain a carrier particle body with a particle size of 1-2 mm;

[0026] (2) placing the carrier particle green body into a vacuum hot pressing sintering furnace for sintering, first slowly heating from room temperature to 700°C and keeping the temperature for 40 minutes; then heating to 1800°C, and introducing argon at about 1400°C, with the atmosphere pressure maintained at 0.06MPa; finally, rapidly heating to 2000°C, keeping the temperature for 45 minutes, closing the furnace and cooling naturally, and placing the material into a rolling ball mill for ball milling at a speed of 15r / min for 12 to 15h to obtain a ball-milled silicon carbide carrier;

[0027] The present invention obtains a porous silicon carbide carrier with a huge specific surface area by sintering silicon carbide to form pores, and assisted by rolling ball milling, so that the curvature between the surface and the curved surface of the silicon carbide carrier is reduced, thereby increasing the catalyst loading at the chamfer and improving the catalytic effect;

[0028] (3) The ball-milled silicon carbide carrier prepared above and deionized water, ferrous sulfate, ferric chloride and polyacrylamide were mixed uniformly in a mass ratio of 5:200:1:2:2, poured into a reactor and heated to 60-70° C., stirred for 40-60 min, and then nitrogen was introduced into the reactor, heated in a water bath to 60-80° C., stirred for 10-15 min, and a mixed solution was obtained;

[0029] (4) adding a 30% sodium hydroxide solution to the mixed solution, adjusting the pH to 8-11, continuing stirring at 80-90° C. for 2-3 hours, cooling to room temperature and aging for 2-3 hours, filtering to obtain a precipitate, washing the precipitate with deionized water and anhydrous ethanol for 2-3 times, respectively, and transferring to a constant temperature drying oven and drying at 70-80° C. for 12-18 hours to obtain a magnetic ball-milled silicon carbide carrier;

[0030] (5) A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 4000 to 5000, and a magnetic ball-milled silicon carbide carrier are fully stirred and mixed in a mass ratio of 100:1:500, and then dried at 100 to 120° C. for 2 to 4 hours and ground to obtain a magnetic lithium chloride solid acid catalyst;

[0031] (6) under the protection of argon, 40-50 parts by weight of 2-bromopyridine and 60-70 parts of tetrahydrofuran were added to the reaction kettle, the temperature of the reaction system was lowered to 15-20° C. in an ice-water bath, 44-50 parts of a tetrahydrofuran solution of isopropyl magnesium chloride was added dropwise, and then 2-3 parts of a magnetic lithium chloride solid acid catalyst were added, and the reaction was completed to obtain a yellow opaque system;

[0032] (7) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 40 to 50 parts by mass of a 10% hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 8 to 9. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.

[0033] The catalyst lithium chloride used in the present invention can most effectively accelerate the exchange reaction speed of halogen ions and magnesium ions. Under the same reaction temperature and time, the reaction conversion rate can be increased from 18% to 84%. Under suitable conditions, the catalyst lithium chloride is loaded on a magnetic ball-milled silicon carbide carrier, and the catalytic advantage of lithium chloride is successfully combined with the rapid separation advantage of the magnetic ball-milled silicon carbide carrier, so that the catalyst lithium chloride can be recovered and reused. The loaded lithium chloride still maintains a high catalytic activity, greatly reducing environmental pollution and making the subsequent separation and purification of the product The method is simpler and can catalyze to obtain high-purity 2-pyridinecarboxaldehyde. The method uses 2-bromopyridine or 3-bromopyridine as a raw material, uses a Grignard reagent exchange method to prepare a 2-pyridine Grignard reagent and a 3-pyridine Grignard reagent, reacts with DMF to prepare 2-pyridinecarboxaldehyde and 3-pyridinecarboxaldehyde, uses supported active lithium chloride as a catalyst, and reacts under suitable conditions to obtain 2-pyridinecarboxaldehyde. The reaction yield is high, the catalyst can be recycled by a magnetic sedimentation method, the lithium chloride can be recycled and reused, the obtained product has high purity, no catalyst residue is in the reaction product, the reaction cost is low, and the benefit is high.

[0034] Example 1

[0035] (1) Weighing 90 parts by weight of silicon carbide powder with a particle size of 1 μm, 10 parts of kaolin, 1 part of boron carbide, 5 parts of polyethylene glycol 6000, 5 parts of phenolic resin, and 1 part of ammonium bicarbonate, stirring and mixing for 20 minutes, and then extruding and granulating to obtain a carrier particle body with a particle size of 1 mm;

[0036] (2) placing the carrier particle green body into a vacuum hot pressing sintering furnace for sintering, first slowly heating from room temperature to 700°C and keeping the temperature for 40 minutes; then heating to 1800°C, and introducing argon at about 1400°C, with the atmosphere pressure maintained at 0.06MPa; finally, rapidly heating to 2000°C, keeping the temperature for 45 minutes, closing the furnace and cooling naturally, and after discharging the material, placing it into a rolling ball mill and ball milling it at a speed of 15r / min for 12 hours to obtain a ball-milled silicon carbide carrier;

[0037] (3) The ball-milled silicon carbide carrier prepared above was mixed evenly with deionized water, ferrous sulfate, ferric chloride and polyacrylamide in a mass ratio of 5:200:1:2:2, poured into a reactor and heated to 60° C., stirred for 40 min, and then nitrogen was introduced into the reactor, heated in a water bath to 60° C., stirred for 10 min, and a mixed solution was obtained;

[0038] (4) adding a 30% sodium hydroxide solution to the mixed solution, adjusting the pH to 8, continuing to stir at 80° C. for 2 h, cooling to room temperature and aging for 2 h, filtering to obtain a precipitate, washing the precipitate with deionized water and anhydrous ethanol twice, respectively, and transferring to a constant temperature drying oven and drying at 70° C. for 12 h to obtain a magnetic ball-milled silicon carbide carrier;

[0039] (5) A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 4000 and a magnetic ball-milled silicon carbide carrier were fully stirred and mixed at a mass ratio of 100:1:500, and then dried at 100° C. for 2 h and ground to obtain a magnetic lithium chloride solid acid catalyst;

[0040] (6) Under argon protection, 40 parts by weight of 2-bromopyridine and 60 parts of tetrahydrofuran were added to the reaction kettle, the temperature of the reaction system was lowered to 15° C. in an ice-water bath, 44 parts of a tetrahydrofuran solution of isopropyl magnesium chloride was added dropwise, and then 2 parts of a magnetic lithium chloride solid acid catalyst were added, and the reaction was completed to obtain a yellow opaque system;

[0041] (7) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 40 parts of a 10% by mass hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 8. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.

[0042] The yield of 2-pyridinecarboxaldehyde prepared in this embodiment is 93.8%, and its purity is 99.65% after gas chromatography analysis. The magnetic lithium chloride solid acid catalyst obtained after magnetic separation has stable catalytic performance and can be further used to prepare 2-pyridinecarboxaldehyde.

[0043] Example 2

[0044] (1) Weighing 95 parts of silicon carbide powder with a particle size of 2 μm, 13 parts of kaolin, 1 part of boron carbide, 8 parts of polyethylene glycol 6000, 8 parts of phenolic resin, and 2 parts of ammonium bicarbonate by weight, stirring and mixing for 25 minutes, and then extruding and granulating to obtain a carrier particle body with a particle size of 2 mm;

[0045] (2) placing the carrier particle green body into a vacuum hot pressing sintering furnace for sintering, first slowly heating from room temperature to 700°C and keeping the temperature for 40 minutes; then heating to 1800°C, and introducing argon at about 1400°C, with the atmosphere pressure maintained at 0.06MPa; finally, rapidly heating to 2000°C, keeping the temperature for 45 minutes, closing the furnace and cooling naturally, and after discharging, placing the material into a rolling ball mill and ball milling at a speed of 15r / min for 14 hours to obtain a ball-milled silicon carbide carrier;

[0046] (3) The ball-milled silicon carbide carrier prepared above was mixed evenly with deionized water, ferrous sulfate, ferric chloride and polyacrylamide in a mass ratio of 5:200:1:2:2, poured into a reactor and heated to 65° C., stirred for 50 min, and then nitrogen was introduced into the reactor, heated to 70° C. in a water bath, and stirred for 13 min to obtain a mixed solution;

[0047] (4) adding a 30% sodium hydroxide solution to the mixed solution, adjusting the pH to 8-11, continuing stirring at 85° C. for 3 h, cooling to room temperature and aging for 3 h, filtering to obtain a precipitate, washing the precipitate with deionized water and anhydrous ethanol for 3 times, respectively, and transferring to a constant temperature drying oven and drying at 75° C. for 15 h to obtain a magnetic ball-milled silicon carbide carrier;

[0048] (5) A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 4500 and a magnetic ball-milled silicon carbide carrier were fully stirred and mixed in a mass ratio of 100:1:500, and then dried at 110° C. for 3 h and ground to obtain a magnetic lithium chloride solid acid catalyst;

[0049] (6) Under argon protection, 45 parts by weight of 2-bromopyridine and 65 parts of tetrahydrofuran were added to the reaction kettle, the temperature of the reaction system was lowered to 18° C. in an ice-water bath, 48 parts of a tetrahydrofuran solution of isopropyl magnesium chloride was added dropwise, and then 3 parts of a magnetic lithium chloride solid acid catalyst was added. The reaction was completed to obtain a yellow opaque system;

[0050] (7) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 45 parts of a 10% by mass hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 8. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.

[0051] The yield of 2-pyridinecarboxaldehyde prepared in this embodiment is 95.3%, and its purity is 99.70% after gas chromatography analysis. The magnetic lithium chloride solid acid catalyst obtained after magnetic separation has stable catalytic performance and can be further used to prepare 2-pyridinecarboxaldehyde.

[0052] Example 3

[0053] (1) 100 parts of silicon carbide powder with a particle size of 2 μm, 15 parts of kaolin, 2 parts of boron carbide, 10 parts of polyethylene glycol 6000, 10 parts of phenolic resin, and 2 parts of ammonium bicarbonate were weighed by weight, stirred and mixed for 30 minutes, and then extruded and granulated to obtain a carrier particle body with a particle size of 2 mm;

[0054] (2) placing the carrier particle green body into a vacuum hot pressing sintering furnace for sintering, first slowly heating from room temperature to 700°C and keeping the temperature for 40 minutes; then heating to 1800°C, and introducing argon at about 1400°C, with the atmosphere pressure maintained at 0.06MPa; finally, rapidly heating to 2000°C, keeping the temperature for 45 minutes, closing the furnace and cooling naturally, and after discharging, placing the material into a rolling ball mill and ball milling at a speed of 15r / min for 15 hours to obtain a ball-milled silicon carbide carrier;

[0055] (3) The ball-milled silicon carbide carrier prepared above was mixed evenly with deionized water, ferrous sulfate, ferric chloride and polyacrylamide in a mass ratio of 5:200:1:2:2, poured into a reactor and heated to 70° C., stirred for 60 min, and then nitrogen was introduced into the reactor, heated to 80° C. in a water bath, and stirred for 15 min to obtain a mixed solution;

[0056] (4) adding a 30% sodium hydroxide solution to the mixed solution, adjusting the pH to 11, continuing stirring at 90° C. for 3 h, cooling to room temperature and aging for 3 h, filtering to obtain a precipitate, washing the precipitate with deionized water and anhydrous ethanol for 3 times, respectively, and transferring to a constant temperature drying oven and drying at 80° C. for 18 h to obtain a magnetic ball-milled silicon carbide carrier;

[0057] (5) A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 5000 and a magnetic ball-milled silicon carbide carrier were fully stirred and mixed at a mass ratio of 100:1:500, and then dried at 120° C. for 4 h and ground to obtain a magnetic lithium chloride solid acid catalyst;

[0058] (6) Under argon protection, 50 parts by weight of 2-bromopyridine and 70 parts of tetrahydrofuran were added to the reaction kettle, the temperature of the reaction system was lowered to 20° C. in an ice-water bath, 50 parts of a tetrahydrofuran solution of isopropylmagnesium chloride was added dropwise, and then 3 parts of a magnetic lithium chloride solid acid catalyst was added. The reaction was completed to obtain a yellow opaque system;

[0059] (7) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 50 parts by mass of a 10% hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 9. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.

[0060] The yield of 2-pyridinecarboxaldehyde prepared in this embodiment is 94.5%, and its purity is 99.85% after gas chromatography analysis. The magnetic lithium chloride solid acid catalyst obtained after magnetic separation has stable catalytic performance and can be further used to prepare 2-pyridinecarboxaldehyde.

[0061] Comparison Example

[0062] Comparative Example 1: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the magnetic lithium chloride solid acid catalyst of the present invention is not added, and the other preparation schemes and steps remain unchanged. 2-pyridinecarboxaldehyde is also prepared, but the yield of 2-pyridinecarboxaldehyde prepared in this comparative example is only 68%, and its purity is 96.5% by gas chromatography analysis;

[0063] Since the magnetic lithium chloride solid acid catalyst of the present invention is not added in this comparative example, the final product yield and purity are significantly reduced. It can be confirmed that the catalyst lithium chloride used in the present invention can most effectively accelerate the exchange reaction speed of halogen ions and magnesium ions. Under the same reaction temperature and time, the reaction conversion rate can be increased from 18% to 84%. Under appropriate conditions, the catalyst lithium chloride is loaded on the magnetic ball-milled silicon carbide carrier, which successfully combines the catalytic advantage of lithium chloride with the rapid separation advantage of the magnetic ball-milled silicon carbide carrier, so that the catalyst lithium chloride can be recovered and reused, and the loaded lithium chloride still maintains a high catalytic efficiency. The invention has high catalytic activity, greatly reduces environmental pollution, and makes the subsequent separation and purification of the product simpler, and can catalyze to obtain high-purity 2-pyridinecarboxaldehyde; the invention uses 2-bromopyridine or 3-bromopyridine as a raw material, uses a Grignard reagent exchange method to prepare a 2-pyridine Grignard reagent and a 3-pyridine Grignard reagent, reacts with DMF to prepare 2-pyridinecarboxaldehyde and 3-pyridinecarboxaldehyde, uses supported active lithium chloride as a catalyst, and reacts under suitable conditions to obtain 2-pyridinecarboxaldehyde, has a high reaction yield, the catalyst can be recycled by a magnetic sedimentation method, the lithium chloride can be recycled and reused, the obtained product has high purity, no catalyst residue is in the reaction product, the reaction cost is low, and the benefit is high;

[0064] Comparative Example 2: The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that a common zeolite molecular sieve is used to replace the magnetic ball-milled silicon carbide carrier of the present invention to prepare the catalyst, and other preparation schemes and steps remain unchanged, and 2-pyridinecarboxaldehyde is also prepared;

[0065] The yield of the final product is only 52%, the purity is only 95.0%, and there is residual catalyst in the product. The used catalyst is also difficult to recycle and reuse. This proves that the present invention obtains a porous silicon carbide carrier with a huge specific surface area by sintering and pore-forming silicon carbide, and supplemented by rolling ball milling, so that the curvature between the surface and the curved surface of the silicon carbide carrier is reduced, thereby increasing the catalyst loading at the chamfer and improving the catalytic effect.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A catalyst for preparing pyridinecarboxaldehyde, characterized in that: It includes a catalyst carrier and a catalyst active component; The catalyst carrier is a magnetic ball-milled silicon carbide carrier; The active ingredient of the catalyst is lithium chloride; The magnetic ball-milled silicon carbide carrier is prepared by mixing and granulating silicon carbide powder, kaolin, boron carbide, polyethylene glycol 6000 and phenolic resin, sintering at high temperature, ball-milling, heating and reacting with deionized water, ferrous sulfate, ferric chloride and polyacrylamide, and finally precipitating with sodium hydroxide solution.

2. A method for preparing a catalyst for preparing pyridinecarboxaldehyde as claimed in claim 1, characterized in that The specific preparation steps are: A 30% lithium chloride methanol solution, a polycarboxylic acid with a viscosity average molecular weight of 4000-5000 and a magnetic ball-milled silicon carbide carrier are fully stirred and mixed at a mass ratio of 100:1:500, and then dried at 100-120°C for 2-4h and ground to obtain a catalyst for preparing pyridine carboxaldehyde.

3. A method for preparing a catalyst for preparing pyridinecarboxaldehyde according to claim 1, characterized in that: The preparation steps of the magnetic ball-milled silicon carbide carrier are: (1) mixing the ball-milled silicon carbide carrier and deionized water, ferrous sulfate, ferric chloride and polyacrylamide in a mass ratio of 5:200:1:2:2, pouring into a reaction kettle and heating to 60-70° C., stirring for 40-60 min, then introducing nitrogen into the reaction kettle, heating in a water bath to 60-80° C., stirring for 10-15 min, and obtaining a mixed solution; (2) Add a 30% sodium hydroxide solution to the mixed solution, adjust the pH to 8-11, continue stirring at 80-90°C for 2-3 hours, cool to room temperature and age for 2-3 hours, filter to obtain a precipitate, rinse the precipitate with deionized water and anhydrous ethanol for 2-3 times, move it into a constant temperature drying oven and dry it at 70-80°C for 12-18 hours to obtain a magnetic ball-milled silicon carbide carrier.

4. A method for preparing a catalyst for preparing pyridinecarboxaldehyde according to claim 3, characterized in that: The preparation steps of the ball-milled silicon carbide carrier are: (1) Weigh 90-100 parts by weight of silicon carbide powder with a particle size of 1-2 μm, 10-15 parts of kaolin, 1-2 parts of boron carbide, 5-10 parts of polyethylene glycol 6000, 5-10 parts of phenolic resin, and 1-2 parts of cellulose acetate, stir and mix for 20-30 minutes, and then extrude and granulate to obtain a carrier particle body with a particle size of 1-2 mm; (2) The carrier particle green body is placed in a vacuum hot pressing sintering furnace for sintering. First, the temperature is slowly raised from room temperature to 700°C and kept at this temperature for 40 minutes; then the temperature is raised to 1800°C, and argon is introduced at about 1400°C, and the atmosphere pressure is maintained at 0.06MPa; finally, the temperature is quickly raised to 2000°C, and after keeping at this temperature for 45 minutes, the furnace is closed and cooled naturally. After the material is discharged, it is placed in a rolling ball mill and ball-milled at a speed of 15r / min for 12 to 15 hours to obtain a ball-milled silicon carbide carrier.

5. The use of a catalyst for preparing pyridine carboxaldehyde as claimed in any one of claims 1 to 4, characterized in that: For preparing 2-pyridinecarboxaldehyde, the specific preparation steps are: (1) by weight, under the protection of argon, add 40-50 parts of 2-bromopyridine and 60-70 parts of tetrahydrofuran to a reaction kettle, lower the temperature of the reaction system to 15-20° C. in an ice-water bath, dropwise add 44-50 parts of a tetrahydrofuran solution of isopropylmagnesium chloride, and then add 2-3 parts of a magnetic lithium chloride solid acid catalyst, and react completely to obtain a yellow opaque system; (2) Then, at 0°C, a mixture of N,N-dimethylformamide and tetrahydrofuran in a volume ratio of 1:7 was slowly added dropwise, and the reaction was followed by TLC until the reaction was completed. The reaction solution was poured into 40 to 50 parts by mass of a 10% hydrochloric acid solution to quench the reaction, and then a saturated sodium carbonate solution was added dropwise to raise the pH value of the reaction solution to 8 to 9. Most of the tetrahydrofuran was removed by reduced pressure distillation using a rotary evaporator, and the remaining mixture was extracted three times with diethyl ether. The organic phases were combined, dried over anhydrous sodium sulfate, and the solvent was removed to obtain a crude product, which was purified by column chromatography to obtain a light yellow oily liquid 2-pyridinecarboxaldehyde.