Preparation method of catalyst for synthesizing pyridine base

Abstract

The invention discloses a preparation method of a catalyst for synthesizing pyridine base, which comprises the following steps: mixing bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate to prepare a deionized water solution, regulating the pH value to 5 with nitric acid, dipping an H-ZSM-5 zeolite molecular sieve in a salt solution, continuously stirring, preserving heat, naturally cooling, washing, drying, and calcining at high temperature to obtain the catalyst for synthesizing pyridine base. And uniformly mixing the modified molecular sieve with the binder of the remaining components, carrying out spray drying, continuing high-temperature calcination, filling the formed catalyst into a fluidized bed reactor, and carrying out activity evaluation by adopting an aldehyde ammonia condensation process. According to the method, the novel catalyst is prepared by loading bismuth, cobalt, cadmium or other metal oxides on the ZSM-5 type zeolite molecular sieve, the reaction is carried out under the aldehyde ammonia synthesis process condition, the yield of pyridine in the pyridine base is increased, the yield ratio of pyridine to 3-methylpyridine can be increased to 20: 1, and the total yield of the pyridine base is kept to be 91.7% or above.

Description

Technical Field

[0001] The invention relates to the technical field of pyridine base synthesis, and in particular to a method for preparing a catalyst for synthesizing pyridine base. Background Art

[0002] Pyridine base is a general term for pyridine and alkylpyridine. It is an organic intermediate with a very wide range of applications and a very large application volume, especially in the fields of pesticides, medicines and additives.

[0003] In the production process of pyridine base, the reaction will generate pure pyridine as a byproduct 3-methylpyridine and a very small amount of other alkylpyridines. In the currently known industrial production, the output ratio of pyridine and 3-methylpyridine is basically stable, and these two raw materials have derived two completely different industrial chains. The consumption of pyridine mainly depends on paraquat and diquat, while the downstream of 3-methylpyridine is mainly nicotinamide. When the nicotinamide industry chain is weak, it will cause 3-methylpyridine to accumulate inventory due to insufficient consumption, and supply will exceed demand, leading to a drop in market prices. On the other hand, with the extension of the downstream industry chain of pyridine, the demand for pyridine continues to expand. Increasing the output of pyridine in pyridine base is very beneficial for production companies to cope with market changes.

[0004] Publication No. CN118598800A discloses a method for increasing the proportion of pyridine in a pyridine-base reaction, wherein formaldehyde and crotonaldehyde are mixed, vaporized and preheated and then enter a reactor, ammonia is introduced into the bottom of the reactor for reaction, and formaldehyde, crotonaldehyde and ammonia react under the action of a catalyst, and after the reaction, the high-temperature gas enters a quenching tower from the top of the reactor, and then enters a subsequent distillation tower to obtain a pyridine-base product, wherein the mass ratio of pyridine to 3-methylpyridine in the pyridine-base product is 5:1; without changing the reaction equipment and the catalyst, only the feed raw materials and the feed ratio are simply changed, and by adjusting the reaction temperature, the proportion of 3-methylpyridine in the reaction product is reduced while ensuring the yield of the pyridine-base reaction, but the overall yield is only 45%, which is relatively low.

[0005] Announcement No. CN1263741C discloses a method for preparing pyridine and 3-methylpyridine, which mainly uses metal oxides of cobalt, lead or a mixture thereof loaded on ZSM-5 zeolite as a catalyst and an aldehyde-ammonia condensation process in the gas phase to produce pyridine and 3-methylpyridine. The maximum output ratio of pyridine / 3-methylpyridine is 20:1, but the total yield is only 78%, and the proportion of 2-methylpyridine and 4-methylpyridine is too high.

[0006] Publication No. CN1172915C discloses a method for preparing pyridine bases, wherein aliphatic aldehydes, aliphatic ketones or mixtures thereof are reacted with ammonia in the presence of a zeolite catalyst in a gas phase, wherein the zeolite catalyst contains titanium and / or cobalt and silicon as zeolite constituent elements, wherein the atomic ratio of silicon to titanium and / or cobalt is from about 5 to about 1000, and the total yield of pyridine bases is 72.8%, which is still not ideal.

[0007] U.S. Patent No. 4861894 (1989) discloses a catalyst for pyridine alkali synthesis using a high silicon ZSM-5 zeolite with a SiO2 / Al2O3 molar ratio of 225 as raw powder and a molecular sieve made of SiO2 as a binder. Under the reaction conditions that the acetaldehyde / formaldehyde molar ratio is 1.4, the ammonia / aldehyde molar ratio is 1.5, and the reaction pressure is normal pressure, the pyridine yield of the catalyst is 47%, the yield of picoline (including 2-picoline, 3-picoline and 4-picoline) is 14%, and the total yield of pyridine and picoline is 61%. However, the total yield of pyridine alkali of the catalyst is still not ideal.

[0008] In the existing industrial production, the output ratio of pyridine to 3-methylpyridine is basically fixed. Therefore, it is urgent to find a method to increase the output ratio of pyridine. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing a catalyst for synthesizing pyridine base, which can increase the output ratio of pyridine / 3-methylpyridine to 20:1 and maintain the total yield of pyridine base above 91.7%, so as to solve the problems raised in the above background technology.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A method for preparing a catalyst for synthesizing pyridine base comprises the following steps:

[0012] Step 1: preparing a deionized water solution by mixing bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate;

[0013] Step 2: After adjusting the pH to 5 with nitric acid, immerse the H-ZSM-5 zeolite molecular sieve in a salt solution, continue stirring and keep warm, cool naturally, wash, dry in a drying oven at 70-95° C. for 6 hours, and then calcine the dried modified molecular sieve at 400-600° C. in a muffle furnace for 4-10 hours;

[0014] Step 3: Mix 10% to 85% w / w of the modified molecular sieve with the binder of the remaining components, spray dry, and continue high-temperature calcination. The formed catalyst is loaded into a fluidized bed reactor and the activity is evaluated using an aldehyde-ammonia condensation process.

[0015] Furthermore, the preparation of the H-ZSM-5 zeolite molecular sieve comprises the following steps:

[0016] ZSM-5 raw powder was prepared by hydrothermal synthesis method with water glass and aluminum sulfate as silicon source and aluminum source respectively and hexamethylenediamine as template. The raw ZSM-5 powder was crystallized in a stainless steel reactor. The obtained raw ZSM-5 powder was deamined and wet mixed with a binder and extruded into strips. Ion exchange was carried out with ammonium nitrate solution to obtain H-ZSM-5 molecular sieve.

[0017] Furthermore, the atomic molar ratio of bismuth, cobalt and cadmium atoms in the bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate is in the range of 1-4:1:0.3-1, and the mass ratio of the mixed metal elements to the modified molecular sieve is 0.15% w / w-1.1% w / w.

[0018] Furthermore, the process of activity evaluation using the aldehyde-ammonia condensation process is as follows:

[0019] The ratio of raw materials formaldehyde: acetaldehyde: liquid ammonia is 0.5-1.7:1:1.0-2.5, the reaction temperature is 300-550°C, the reaction pressure is 0.02-0.15Mpa, the formed catalyst is collected by condensation, and then detected by gas chromatography, and the content of pyridine and 3-methylpyridine is quantitatively analyzed by internal standard method.

[0020] Furthermore, the high temperature calcination temperature of step 2 and step 3 is 400-600°C.

[0021] Furthermore, the crystallization temperature of the ZSM-5 raw powder is 115-195° C., the crystallization time is 0-25 hours, and the crystallinity reaches 95.7%.

[0022] Furthermore, the inner diameter of the fluidized bed reactor is 80 mm and the length is 900 mm. A catalyst filter is provided on the top and a distribution plate for receiving the catalyst is provided on the bottom. Formaldehyde, acetaldehyde and ammonia feed ports are provided below the distribution plate. A condenser is provided above the distribution plate. The fluidized bed reactor is placed in a three-stage heating furnace.

[0023] Furthermore, in step 2, the molecular sieve is immersed in a salt solution at 45-85° C. for 12 hours.

[0024] Furthermore, the binder in step 3 is at least one of silica sol and alumina sol, the silica sol is SiO2, and the alumina sol is alumina, and the usage amount is 0-25%.

[0025] Furthermore, the particle size of the modified molecular sieve after spray drying is 0.18 to 0.22 mm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The invention changes the acidic sites in the molecular sieve by modifying the molecular sieve and loading the metal, and increases the output ratio of pure pyridine / 3-methylpyridine in the product to 20:1 by adjusting the B acid and L acid centers. Moreover, the total yield of pyridine base is maintained at more than 91.7% without changing the raw materials and process conditions, and the overall preparation cost is low, which is very suitable for industrial production. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1: Using water glass and aluminum sulfate as silicon source and aluminum source respectively and hexamethylenediamine as template, a hydrothermal synthesis method is adopted to first synthesize ZSM-5 raw powder, and then crystallization is carried out at a crystallization temperature of 175°C and a crystallization time of 20 h. The obtained ZSM-5 raw powder is deamined and wet mixed with a binder and extruded into strips. Ion exchange is then carried out with an ammonium nitrate solution to obtain an H-ZSM-5 molecular sieve. This molecular sieve is used as catalyst A and is evaluated according to the above-mentioned catalyst activity evaluation method.

[0030] Example 2: A certain amount of bismuth nitrate pentahydrate was dissolved in 500 ml of deionized water, a small amount of nitric acid was added to adjust the pH to 5, and 20 g of molecular sieve A was immersed in a cobalt nitrate aqueous solution, fully stirred and kept at 85 ° C for 12 hours, naturally cooled, filtered, washed and placed in a drying oven at 85 ° C for 4 hours, and the dried modified molecular sieve was placed in a muffle furnace and calcined at 550 ° C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, and the particles were sprayed into a suitable size by a spray dryer, and calcined at 550 ° C for 4 hours to obtain a molded catalyst B, which was evaluated according to the above catalyst activity evaluation method. The bismuth loaded in B is 0.2% w / w.

[0031] Example 3: A certain amount of cobalt nitrate hexahydrate was dissolved in 500 ml of deionized water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in a zinc nitrate aqueous solution, fully stirred and kept at 85°C for 12 hours, naturally cooled, filtered, washed and placed in a drying oven for 4 hours at 85°C, and the dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer to a suitable particle size, calcined at 550°C for 4 hours, and a molded catalyst C was obtained, and evaluated according to the above catalyst activity evaluation method. The cobalt loaded in C is 0.2% w / w.

[0032] Example 4: A certain amount of cadmium nitrate tetrahydrate was dissolved in 500 ml of deionized water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in an aqueous solution of ferric nitrate, fully stirred and kept at 85°C for 12 hours, naturally cooled, filtered, washed and placed in a drying oven for 4 hours at 85°C, the dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours, and finally the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer to a suitable particle size, calcined at 550°C for 4 hours, and a molded catalyst D was obtained, and evaluated according to the above catalyst activity evaluation method. The cadmium loaded in D is 0.2% w / w.

[0033] Example 5: Bismuth nitrate pentahydrate and cobalt nitrate hexahydrate in an atomic molar ratio of 2:1 were mixed and dissolved in 500 ml deionized water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer to form a particle size of appropriate size, and calcined at 550°C for 4 hours to obtain a formed catalyst E, which was evaluated according to the above-mentioned catalyst activity evaluation method.

[0034] Example 6: Bismuth nitrate pentahydrate and cadmium nitrate tetrahydrate in an atomic molar ratio of 2:1 were mixed and dissolved in 500 ml deionized water, the pH was adjusted to 5 using a small amount of nitric acid, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer to form a particle size of appropriate size, and calcined at 550°C for 4 hours to obtain a formed catalyst F, which was evaluated according to the above-mentioned catalyst activity evaluation method.

[0035] Example 7: Cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate in an atomic molar ratio of 2:1 were mixed and dissolved in 500 ml deionized water, the pH was adjusted to 5 using a small amount of nitric acid, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer to form a particle size of appropriate size, and calcined at 550°C for 4 hours to obtain a formed catalyst G, which was evaluated according to the above-mentioned catalyst activity evaluation method.

[0036] Example 8: Bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate were mixed and dissolved in 500 ml deionized water in an atomic molar ratio of 2:1:0.5, respectively. The pH was adjusted to 5 using a small amount of nitric acid, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution. The mixture was fully stirred and kept warm at 85°C for 12 hours. After natural cooling, the mixture was filtered, washed and dried in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, and the particles were passed through a spray dryer to form a suitable particle size. The particles were calcined at 550°C for 4 hours to obtain a formed catalyst H, which was evaluated according to the above-mentioned catalyst activity evaluation method.

[0037] Table 1: Catalyst activity test results

[0038]

[0039] From the evaluation results in Table 1, it can be seen that bismuth, cobalt and cadmium all have the effect of increasing the output of pure pyridine. From the perspective of the combination effect, the synergistic effect of the bimetallic combination of bismuth and cobalt is more obvious. After adding the cadmium element combination, the overall output ratio has a significant decrease. Therefore, it can be judged that the combination of metal bismuth and cobalt has the best effect.

[0040] Comparative Example 1: Bismuth nitrate pentahydrate and cobalt nitrate hexahydrate in an atomic molar ratio of 1:1 were mixed and dissolved in 500 ml of water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer into a particle size of suitable size, calcined at 550°C for 4 hours, and the molded catalyst E1 was obtained, and evaluated according to the above-mentioned catalyst activity evaluation method.

[0041] Comparative Example 2: Bismuth nitrate pentahydrate and cobalt nitrate hexahydrate in an atomic molar ratio of 3:1 were mixed and dissolved in 500 ml of water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer into a particle size of suitable size, calcined at 550°C for 4 hours, and the molded catalyst E2 was obtained, and evaluated according to the above-mentioned catalyst activity evaluation method.

[0042] Comparative Example 3: Bismuth nitrate pentahydrate and cobalt nitrate hexahydrate in an atomic molar ratio of 1:2 were mixed and dissolved in 500 ml of water, the pH was adjusted to 5 using a small amount of nitric acid, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer into a particle size of appropriate size, calcined at 550°C for 4 hours, and the molded catalyst E3 was obtained, and evaluated according to the above-mentioned catalyst activity evaluation method.

[0043] Comparative Example 4: Bismuth nitrate pentahydrate and cobalt nitrate hexahydrate in an atomic molar ratio of 4:1 were mixed and dissolved in 500 ml of water, a small amount of nitric acid was used to adjust the pH to 5, and 20 g of molecular sieve A was weighed and immersed in the mixed salt solution, fully stirred and kept warm at 85°C for 12 hours. After natural cooling, it was filtered, washed and placed in a drying oven at 85°C for 4 hours. The dried modified molecular sieve was placed in a muffle furnace and calcined at 550°C for 6 hours. Finally, the modified molecular sieve and the binder of the remaining components were mixed, passed through a spray dryer into a particle size of suitable size, calcined at 550°C for 4 hours, and the molded catalyst E4 was obtained, and evaluated according to the above-mentioned catalyst activity evaluation method.

[0044] Table 2: Comparative activity test results

[0045]

[0046] As can be seen from Table 2, from the test results of the activity of the modified molecular sieve catalyst loaded with bismuth and cobalt in different molar ratios, when the molar ratio of bismuth to cobalt atoms is 3:1, the catalyst activity is stronger and the selectivity is better. This is because the ammonia aldehyde condensation reaction is an acid-catalyzed reaction, which is completed by the synergistic action of B acid and L acid. The number, proportion and position arrangement of the acid sites on the catalyst surface determine the selectivity of the reaction. The ratio of B acid center and L acid center is adjusted by loading metal elements, which directly affects the activity and selectivity of the catalyst. Therefore, we choose to load different metal elements on the basis of zeolite molecular sieves to achieve the purpose of improving the selectivity and activity of the catalyst.

[0047] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for synthesizing pyridine base, characterized in that: The steps include: Step 1: preparing a deionized water solution by mixing bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate; Step 2: adjust the pH to 5 with nitric acid, immerse the H-ZSM-5 zeolite molecular sieve in the salt solution, continue stirring and keep warm, naturally cool, wash, dry, and then calcine at high temperature; Step 3: The modified molecular sieve is mixed with the binder of the remaining components, spray-dried, and then calcined at high temperature. The formed catalyst is loaded into a fluidized bed reactor and the activity is evaluated using an aldehyde-ammonia condensation process.

2. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The preparation of the H-ZSM-5 zeolite molecular sieve comprises the following steps: ZSM-5 raw powder was prepared by hydrothermal synthesis method with water glass and aluminum sulfate as silicon source and aluminum source respectively and hexamethylenediamine as template. The raw ZSM-5 powder was crystallized in a stainless steel reactor. The obtained raw ZSM-5 powder was deamined and wet mixed with a binder and extruded into strips. Ion exchange was carried out with ammonium nitrate solution to obtain H-ZSM-5 molecular sieve.

3. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The atomic molar ratio of bismuth, cobalt and cadmium atoms in the bismuth nitrate pentahydrate, cobalt nitrate hexahydrate and cadmium nitrate tetrahydrate is in the range of 1-4:1:0.3-1, and the mass ratio of the mixed metal elements to the modified molecular sieve is 0.15% w / w-1.1% w / w.

4. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The process of activity evaluation using the aldehyde-ammonia condensation process is as follows: The ratio of raw materials formaldehyde: acetaldehyde: liquid ammonia is 0.5-1.7:1:1.0-2.5, the reaction temperature is 300-550°C, the reaction pressure is 0.02-0.15Mpa, the formed catalyst is collected by condensation, and then detected by gas chromatography, and the content of pyridine and 3-methylpyridine is quantitatively analyzed by internal standard method.

5. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The high temperature calcination temperature of step 2 and step 3 is 400-600°C.

6. The method for preparing a catalyst for synthesizing pyridine base according to claim 2, characterized in that: The crystallization temperature of the ZSM-5 raw powder is 115-195° C., and the crystallization time is 0-25 hours.

7. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The fluidized bed reactor has an inner diameter of 80 mm and a length of 900 mm. A catalyst filter is provided on the top and a distribution plate for receiving the catalyst is provided on the bottom. Formaldehyde, acetaldehyde and ammonia feed ports are provided below the distribution plate. A condenser is provided above the distribution plate. The fluidized bed reactor is placed in a three-stage heating furnace.

8. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: In step 2, the molecular sieve is immersed in a salt solution at 45-85° C. for 12 hours.

9. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The binder in step 3 is at least one of silica sol and alumina sol.

10. The method for preparing a catalyst for synthesizing pyridine base according to claim 1, characterized in that: The particle size of the modified molecular sieve after spray drying is 0.18-0.22 mm.

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