Method and device for synthesizing pyridine by using composite catalyst

Abstract

Disclosed in the present invention are a method and device for synthesizing pyridine by using a composite catalyst. Synthesis steps are as follows: ultrasonically dissolving a zinc salt in methanol to form a solution A, dissolving an organic ligand in another part of methanol to form a solution B, adding ZSM-5 molecular sieve spheres to the solution A, and then slowly adding the solution B to the solution A; after the reaction is finished, separating a product, washing same, and drying same at room temperature to obtain a catalyst named ZIM-71 / ZSM-5; loading a reactor with the ZIM-71 / ZSM-5 catalyst, feeding nitrogen gas, activating same, raising the temperature to a reaction temperature, and separately feeding an aldehyde mixture and ammonia into the reactor; and cooling a reaction gas discharged from the reactor, and performing extraction, distillation and rectification to obtain a pyridine base product. The ZIF-71 / ZSM-5 composite spheres synthesized in situ serve as a catalyst and exhibit greatly improved activity and prolonged service life, can achieve a pyridine base yield of 90% or more, and further solve the problem of existing catalysts being liable to block reactors.

Description

A method and apparatus for synthesizing pyridine using a composite catalyst Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method and apparatus for synthesizing pyridine using a composite catalyst. Background Technology

[0002] Pyridine and its derivatives are very important chemical intermediates, widely used in the pharmaceutical, pesticide, feed, synthetic rubber, and dye industries. They are also used in the production of surfactants and food additives. Industrially, pyridine is mainly used in the production of sulfonamides, penicillin, vitamin A, cortisone, anthelmintics, and local anesthetics. It is also used as a stabilizer, softener, paint solvent, condensing agent in synthetic resins, and in the synthesis of herbicides, preservatives, and hydroxypyridines.

[0003] Currently, the aldehyde-amine process for synthesizing pyridine bases mainly uses metal-loaded ZSM-5 molecular sieves, which have short lifespans and relatively low yields of pyridine bases. Chinese Patent CN101161343B discloses a novel catalyst for the synthesis of pyridine bases, along with its preparation and application methods. Using a high-silica molecular sieve as a matrix, and after dealumination and desilication treatment, it is used to catalyze the preparation of pyridine bases, achieving a yield of over 65%.

[0004] However, the yield of pyridine bases synthesized by such catalysts is relatively low, the ratio of pyridine to 3-methylpyridine cannot be adjusted, and the reaction gas contains solid catalyst particles, which causes severe wear on the equipment and requires deacidification and desiliconization treatment, making the process cumbersome. Technical issues

[0005] The purpose of this invention is to provide a method and apparatus for synthesizing pyridine using a composite catalyst. For the first time, in-situ synthesized ZIF-71 / ZSM-5 composite spheres are used as the catalyst, which significantly improves the catalyst activity and extends the catalyst life. The pyridine base yield is over 90%, and the problem of reactor clogging by existing catalysts is solved, thereby addressing the problems mentioned in the background art. Technical solutions

[0006] The purpose of this invention is to provide a method and apparatus for synthesizing pyridine using a composite catalyst. For the first time, in-situ synthesized ZIF-71 / ZSM-5 composite spheres are used as the catalyst, which significantly improves the catalyst activity and extends the catalyst life. The pyridine base yield is over 90%, and the problem of reactor clogging by existing catalysts is solved, thereby addressing the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for synthesizing pyridine using a composite catalyst includes the following steps:

[0009] Zinc salt was ultrasonically dissolved in methanol to form solution A, and organic ligand was dissolved in another methanol to form solution B;

[0010] ZSM-5 molecular sieve spheres were added to solution A, and then solution B was slowly added to solution A. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain a catalyst named ZIM-71 / ZSM-5.

[0011] The ZIM-71 / ZSM-5 catalyst was loaded into the reactor and activated by purging with nitrogen.

[0012] After activation, the temperature is raised to the reaction temperature. The mixed aldehydes are vaporized and enter the reactor through the feed pipe at the bottom of the reactor. Ammonia enters the reactor through the gas inlet at the bottom of the reactor.

[0013] The reaction gas from the reactor enters the Venturi condenser and the twin-cell condenser in sequence for cooling before entering the extraction tower for extraction. The liquid from the top enters the distillation tower to remove the solvent, and the bottom liquid enters the crude distillation tower.

[0014] The top liquid from the crude distillation column is fed into the pyridine distillation column for distillation to obtain pyridine product, while the bottom liquid is fed into the 3-methylpyridine distillation column for distillation to obtain 3-methylpyridine product.

[0015] Furthermore, the zinc salt is zinc nitrate hexahydrate or zinc acetate dihydrate.

[0016] Further, the organic ligand is 4,5-dichloro-1-hydroimidazole, the molar ratio of zinc salt to organic ligand is 1:2.5-5, and the mass ratio of zinc salt to ZSM-5 is 1.2-1.7:1.

[0017] Furthermore, the ZIM-71 / ZSM-5 catalyst is added to the reactor in multiple, continuous additions.

[0018] Furthermore, the mixed aldehyde is a mixture of formaldehyde and acetaldehyde.

[0019] Further, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. The activation temperature was 300-350℃ and the activation time was 4-5 hours.

[0020] Furthermore, the reactor has a reaction temperature of 300-330℃ and a reaction pressure of 0.03-0.07MPa.

[0021] An apparatus for synthesizing pyridine using a composite catalyst, characterized in that it comprises a reactor, a Venturi heat exchanger, a twin-cell condenser, an extraction column, a distillation column, a crude distillation column, a pyridine rectification column, and a 3-methylpyridine rectification column. The top outlet of the reactor is connected to the inlet of the Venturi heat exchanger. The twin-cell condenser, the extraction column, and the distillation column are sequentially connected between the Venturi heat exchanger and the crude distillation column. The top outlet of the crude distillation column is connected to the pyridine rectification column, and the bottom outlet of the crude distillation column is connected to the 3-methylpyridine rectification column.

[0022] Furthermore, the reactor includes a reaction section with upper and lower reaction beds inside, and the reaction vapor is discharged through a side outlet.

[0023] Furthermore, it also includes an auxiliary section connected to the top of the reaction section, the interior of which has an air distributor and a gas-solid separator distributed vertically. Beneficial effects

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. For the first time, in-situ synthesized ZIF-71 / ZSM-5 composite spheres were used as catalysts. Compared with ZSM-5 molecular sieves, they have better activity and stability, and the pyridine base yield can reach more than 90%. The lifespan of the ZIF-71 / ZSM-5 composite sphere catalyst is extended, the production cycle is extended, and the production efficiency is improved.

[0026] 2. The reactor of the present invention can be continuously replenished with fresh catalyst through the auxiliary section, which solves the problem of easy clogging of the reactor. Attached Figure Description

[0027] Figure 1 is a schematic diagram of the apparatus for synthesizing pyridine using the composite catalyst of the present invention.

[0028] In the diagram: 1. Reactor; 2. Venturi heat exchanger; 3. Twin-cell condenser; 4. Extraction column; 5. Distillation column; 6. Crude distillation column; 7. Pyridine distillation column; 8. 3-Methylpyridine distillation column; 101. Reaction section; 102. Auxiliary section; 1011. Reaction bed; 1021. Air distributor; 1022. Gas-solid separator. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Referring to Figure 1, an apparatus for synthesizing pyridine using a composite catalyst includes a reactor 1, a Venturi heat exchanger 2, a twin-cell condenser 3, an extraction column 4, a distillation column 5, a crude distillation column 6, a pyridine rectification column 7, and a 3-methylpyridine rectification column 8. The top outlet of the reactor 1 is connected to the inlet of the Venturi heat exchanger 2. The twin-cell condenser 3, the extraction column 4, and the distillation column 5 are connected sequentially between the Venturi heat exchanger 2 and the crude distillation column 6. The top outlet of the crude distillation column 6 is connected to the pyridine rectification column 7. Pyridine is obtained after rectification in the pyridine rectification column 7 (shown in Figure 1 f). The bottom outlet of the crude distillation column 6 is connected to the 3-methylpyridine rectification column 8. 3-methylpyridine is obtained after rectification in the 3-methylpyridine rectification column 8 (shown in Figure 1 g).

[0031] The reactor 1 includes a reaction section 101. The bottom of the reaction section 101 is the feed inlet of the raw material gas (shown in Figure 1a). The raw material gas is a mixed aldehyde. The reaction section 101 has two reaction bed layers 1011 inside. The reaction vapor (shown in Figure 1b and c) is discharged through the side outlet.

[0032] The reactor 1 also includes an auxiliary section 102 connected to the top of the reaction section 101. The lower part of the auxiliary section 102 is an air inlet (shown as d in Figure 1), which is used to introduce nitrogen and air. The upper part of the auxiliary section 102 is a fresh catalyst inlet (shown as e in Figure 1). By continuously replenishing the fresh catalyst, the reaction in the reactor 1 is maintained, and reactor blockage can be prevented. The bottom of the auxiliary section 102 is an ammonia inlet (shown as h in Figure 1). The interior of the auxiliary section 102 has an air distributor 1021 and a gas-solid separator 1022 distributed vertically. The device uses the air distributor 1021 to evenly distribute the incoming air and ammonia, achieving uniform upward air supply. The device also includes a gas-solid separator 1022 to transport the separated reaction gas to the Venturi heat exchanger 2. Example 1

[0033] Catalyst preparation

[0034] Mixture ratio: Zinc nitrate hexahydrate : 4,5-dichloro-1-hydroimidazole = 1 : 2.5 (molar ratio)

[0035] Zinc nitrate hexahydrate: ZSM-5 = 1.2:1 (mass ratio)

[0036] Zinc nitrate hexahydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol solution (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-1.

[0037] Reaction: The catalyst was loaded into the reactor and then activated at 310°C for 5 hours by purging with nitrogen (entering through the air inlet); then the reactor temperature was raised to 300°C, and the mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered into the reactor through the feed pipe at the bottom of the reactor, while ammonia entered the reactor through the air inlet at the bottom of the reactor; the reaction gas exiting the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 90.3%. Example 2

[0038] Catalyst preparation

[0039] Mixture ratio: Zinc nitrate hexahydrate : 4,5-dichloro-1-hydroimidazole = 1 : 3 (molar ratio)

[0040] Zinc nitrate hexahydrate: ZSM-5 = 1.4:1 (mass ratio)

[0041] Zinc nitrate hexahydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol solution (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-2.

[0042] Reaction: The catalyst was loaded into the reactor and activated at 320°C for 5 hours by purging with nitrogen. Then the reactor temperature was raised to 330°C. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia was introduced into the reactor through the gas inlet at the bottom of the reactor. The reaction gas from the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 91.2%. Example 3

[0043] Catalyst preparation

[0044] Mixture ratio: Zinc nitrate hexahydrate : 4,5-dichloro-1-hydroimidazole = 1 : 4 (molar ratio)

[0045] Zinc nitrate hexahydrate: ZSM-5 = 1.7:1 (mass ratio)

[0046] Zinc nitrate hexahydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol solution (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-3.

[0047] Reaction: The catalyst was loaded into the reactor and activated at 300℃ for 5 hours by purging with nitrogen. Then the reactor temperature was raised to 320℃. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia entered the reactor through the gas inlet at the bottom of the reactor. The reaction gas coming out of the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 91.6%. Example 4

[0048] Catalyst preparation

[0049] Mixture ratio: Zinc acetate dihydrate : 4,5-dichloro-1-hydroimidazole = 1 : 5 (molar ratio)

[0050] Zinc acetate dihydrate: ZSM-5 = 1.3:1 (mass ratio)

[0051] Zinc acetate dihydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol solution (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-4.

[0052] Reaction: The catalyst was loaded into the reactor and activated at 330°C for 4 hours by purging with nitrogen. Then the reactor temperature was raised to 330°C. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia entered the reactor through the gas inlet at the bottom of the reactor. The reaction gas coming out of the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 92.1%. Example 5

[0053] Catalyst preparation

[0054] Mixing ratio: Zinc acetate dihydrate : 4,5-dichloro-1-hydroimidazole = 1 : 2.7 (molar ratio)

[0055] Zinc acetate dihydrate: ZSM-5 = 1.6:1 (mass ratio)

[0056] Zinc acetate dihydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-5.

[0057] Reaction: The catalyst was loaded into the reactor and activated at 350°C for 4 hours by purging with nitrogen. Then the reactor temperature was raised to 330°C. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia entered the reactor through the gas inlet at the bottom of the reactor. The reaction gas coming out of the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 90.4%. Example 6

[0058] Catalyst preparation

[0059] Mixing ratio: Zinc acetate dihydrate : 4,5-dichloro-1-hydroimidazole = 1 : 4.5 (molar ratio)

[0060] Zinc acetate dihydrate: ZSM-5 = 1.4:1 (mass ratio)

[0061] Zinc acetate dihydrate was ultrasonically dissolved in methanol (solution A), and 4,5-dichloro-1-hydroimidazole was dissolved in another methanol (solution B). ZSM-5 molecular sieve beads were added to solution A and soaked for 2 hours. Then, solution B was slowly added to solution A, and the mixture was stirred continuously at room temperature for 24 hours. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain the catalyst, named ZIM-71 / ZSM-5-6.

[0062] Reaction: The catalyst was loaded into the reactor and activated at 350°C for 4 hours by purging with nitrogen. Then the reactor temperature was raised to 330°C. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia entered the reactor through the gas inlet at the bottom of the reactor. The reaction gas coming out of the reactor was cooled and then extracted, distilled, and purified to obtain the pyridine base product with a yield of 90.7%.

[0063] Comparative example (refer to a method for preparing pyridine using MgAPO-41 molecular sieve as a catalyst disclosed in announcement number CN106831547B)

[0064] MgAPO-41 molecular sieves were loaded into the reactor and activated with nitrogen at 350°C for 4 hours. The reactor temperature was then raised to 330°C. The mixed aldehydes (formaldehyde and acetaldehyde) were vaporized and entered the reactor through the feed pipe at the bottom of the reactor. Ammonia entered the reactor through the gas inlet at the bottom of the reactor. The reaction gas exiting the reactor was cooled and then extracted, distilled, and purified to obtain pyridine base products. The yield of pyridine base was about 85.0%.

[0065] As shown in the table above, Examples 1-6 all used ZIM-71 / ZSM-5-1 catalysts, and the yield of pyridine bases was above 90%. Compared with the MgAPO-41 molecular sieve used in the comparative example, the yield of pyridine bases was significantly improved. This is because ZIM-71 is composed of metal ions Zn2+ and organic ligand 4,5-dichloro-1-hydro-imidazolium (dclIm), possessing a zeolite RHO topology. The 8-membered ring pore window size of 0.51 nm matches the size of 2,3-butanediol. The pore window contains abundant hydrophobic chlorine groups, which form strong vdW interactions with the longer carbon chain 2,3-butanediol under low concentration conditions in water. Furthermore, the cage diameter is large, allowing multiple 2,3-butanediol molecules to be accommodated simultaneously. Compared with ZSM-5 molecular sieves, it exhibits better activity and stability.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing pyridine using a composite catalyst, characterized in that, Includes the following steps: Zinc salt was ultrasonically dissolved in methanol to form solution A, and organic ligand was dissolved in another methanol to form solution B; ZSM-5 molecular sieve spheres were added to solution A, and then solution B was slowly added to solution A. After the reaction was completed, the product was separated, washed three times with methanol, and dried at room temperature to obtain a catalyst named ZIM-71 / ZSM-5. The ZIM-71 / ZSM-5 catalyst was loaded into the reactor and activated by purging with nitrogen. After activation, the temperature is raised to the reaction temperature. The mixed aldehydes are vaporized and enter the reactor through the feed pipe at the bottom of the reactor. Ammonia enters the reactor through the gas inlet at the bottom of the reactor. The reaction gas from the reactor enters the Venturi condenser (2) and the twin-cell condenser (3) in sequence to cool down and then enters the extraction tower (4) for extraction. The liquid from the top enters the distillation tower (5) to remove the solvent, and the bottom liquid enters the crude distillation tower (6). The top liquid from the crude distillation column (6) enters the pyridine distillation column (7) for distillation to obtain pyridine product, and the bottom liquid enters the 3-methylpyridine distillation column (8) for distillation to obtain 3-methylpyridine product.

2. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, The zinc salt is zinc nitrate hexahydrate or zinc acetate dihydrate.

3. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, The organic ligand is 4,5-dichloro-1-hydroimidazole, the molar ratio of zinc salt to organic ligand is 1:2.5-5, and the mass ratio of zinc salt to ZSM-5 is 1.2-1.7:

1.

4. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, The ZIM-71 / ZSM-5 catalyst was added to the reactor in multiple, continuous additions.

5. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, The mixed aldehyde is a mixture of formaldehyde and acetaldehyde.

6. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, Slowly add solution B to solution A and stir continuously at room temperature for 24 hours. The activation temperature is 300-350℃ and the activation time is 4-5 hours.

7. The method for synthesizing pyridine using a composite catalyst as described in claim 1, characterized in that, The reactor has a reaction temperature of 300-330℃ and a reaction pressure of 0.03-0.07MPa.

8. An apparatus for synthesizing pyridine using a composite catalyst, for synthesizing pyridine using the composite catalyst according to any one of claims 1-7, characterized in that, The system includes a reactor (1), a Venturi heat exchanger (2), a twin-cell condenser (3), an extraction column (4), a distillation column (5), a crude distillation column (6), a pyridine distillation column (7), and a 3-methylpyridine distillation column (8). The top outlet of the reactor (1) is connected to the inlet of the Venturi heat exchanger (2). The twin-cell condenser (3), the extraction column (4), and the distillation column (5) are connected sequentially between the Venturi heat exchanger (2) and the crude distillation column (6). The top outlet of the crude distillation column (6) is connected to the pyridine distillation column (7), and the bottom outlet of the crude distillation column (6) is connected to the 3-methylpyridine distillation column (8).

9. The apparatus for synthesizing pyridine using the composite catalyst as described in claim 8, characterized in that, The reactor (1) includes a reaction section (101), which has two reaction bed layers (1011) inside, and the reaction vapor is discharged through the side outlet.

10. The apparatus for synthesizing pyridine using the composite catalyst as described in claim 8, characterized in that, It also includes an auxiliary part (102) connected to the top of the reaction part (101), the auxiliary part (102) having an air distributor (1021) and a gas-solid separator (1022) distributed vertically inside.

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