Preparation method of bifunctional catalyst for pyridine base production

Abstract

The invention discloses a preparation method of a bifunctional catalyst for pyridine base production, which comprises the following steps: dissolving a double-template agent in deionized water according to a fixed mass ratio, dropwise adding a silicon source solution and a NaOH solution into a double-template agent solution, adding a mixed solution of a zinc source and an aluminum source, stirring at room temperature to form gel, and drying at room temperature to obtain the bifunctional catalyst for pyridine base production. Transferring the prepared gel into a high-pressure reaction kettle, pressurizing, heating to a supercritical state, treating, taking out a sample, drying in a drying box, calcining the dried sample in a muffle furnace, removing the double template agent to obtain the Zn / Al-MCM-41 catalyst with double functions, and catalyzing formaldehyde, acetaldehyde and ammonia to synthesize pyridine base by using the Zn / Al-MCM-41 catalyst. Formaldehyde, acetaldehyde and ammonia are added into a reactor according to a molar ratio, a Zn / Al-MCM-41 catalyst is added at the same time for a catalytic reaction, and the catalytic activity and selectivity are improved by using a bifunctional catalyst for the catalytic reaction.

Description

Technical Field

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

[0002] Pyridine bases are a class of alkaline organic compounds based on pyridine, with a six-membered heterocyclic structure in which one of the carbon atoms is replaced by a nitrogen atom. According to the different substituents, pyridine bases are mainly divided into several categories, including basic pyridine, methylpyridine (one methyl substituent), dimethylpyridine (two methyl substituents) and trimethylpyridine (three methyl substituents). Due to their unique physical and chemical properties, pyridine bases have been widely used in many fields. They are the basic raw materials for the synthesis of many important chemicals and drugs, and play an important role in the fields of pesticides, organic synthesis, materials science, etc.

[0003] The synthesis of pyridine base is usually carried out under high temperature and high pressure or in the presence of a catalyst, and the catalyst used is basically a single-function catalyst or a noble metal catalyst.

[0004] Publication No. CN101148436B discloses a catalytic synthesis method of pyridine base, which uses a catalyst containing rare earth metal to catalyze the synthesis of pyridine base from aldehyde ammonia. The catalyst used in this method is too expensive, which is not conducive to large-scale production of pyridine base.

[0005] Announcement No. CN101161343B discloses a catalyst for synthesizing pyridine base and a method for preparing and using the catalyst. Pyridine base is synthesized using a single acidic site catalyst. Only a single site exists in this method, which will lead to the production of by-products and poisoning of other reaction intermediates, and increase costs and risks in the subsequent waste treatment process.

[0006] Announcement No. CN111468177B discloses a molecular sieve catalyst for preparing pyridine base, and its preparation method and application. Titanium silicon molecular sieve and nano-bismuth trioxide attached to the surface of the molecular sieve are used as catalysts to catalyze the synthesis of pyridine base. In this method, the catalyst only contains acidic active sites. The catalyst is affected by by-products in the multi-step reaction, resulting in loss of activity or poisoning.

[0007] Publication No. CN118561733A discloses a method for synthesizing pyrrole compounds or pyridine compounds by promoting the intramolecular Heck reaction of N-substituted enaminones by DBDMH, and synthesizing pyridine bases using a palladium catalyst. In this method, the palladium catalyst requires a ligand to react and palladium is a precious metal, which increases the production cost.

[0008] Therefore, in the prior art, single-function catalysts usually exhibit good catalytic performance under specific reaction conditions, but have problems such as requiring more stringent reaction conditions and poor control over side reactions, and precious metal catalysts usually have too high production costs. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing a bifunctional catalyst for pyridine base production, which can improve production efficiency, reduce costs, reduce environmental pollution, provide multiple reaction active sites, and improve the efficiency and selectivity of multi-step reactions to solve the problems raised in the above-mentioned background technology.

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

[0011] The preparation method of a bifunctional catalyst for pyridine base production comprises the following steps:

[0012] Dissolve the dual template in deionized water at a fixed mass ratio and stir at room temperature until completely dissolved. Slowly drop the silicon source solution and NaOH solution into the dual template solution, stir to keep it uniform, then add the mixed solution of zinc source and aluminum source, continue to drop NaOH solution, keep the pH of the solution at 10-11, and finally stir at room temperature to form a gel;

[0013] The prepared gel was transferred to a high-pressure reactor, and CO2 was gradually introduced after the valve was closed, the pressure was increased, and the mixture was heated to a supercritical state. After the supercritical treatment, the pressure was slowly released, and the sample was taken out and dried in a drying oven at 100-200°C. The dried sample was then calcined in a muffle furnace to remove the dual template, and finally a Zn / Al-MCM-41 catalyst with dual functionality (acidic and metallic) was obtained;

[0014] The Zn / Al-MCM-41 catalyst is used to catalyze formaldehyde, acetaldehyde and ammonia to synthesize pyridine base. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (25-30% ammonia water or anhydrous ammonia) are added to a reactor at a molar ratio of 1.0-1.2:1:2, and 2-10wt% of the Zn / Al-MCM-41 catalyst is added to carry out a catalytic reaction.

[0015] Furthermore, the dual template agent is dodecyltrimethylammonium bromide (CTAB) and P123.

[0016] Furthermore, the mass ratio of the dual templates is 1:0.1-0.6.

[0017] Furthermore, the volume ratio of the silicon source solution to the alkaline solution is 1-2:1, the molar ratio of the zinc source to the aluminum source is 0.5-2:1, and the total metal content is 0.5-2.5wt%.

[0018] Furthermore, the zinc source is one of Zn(OAc)2, Zn(NO3)2, and Zn(Cl)2, and the aluminum source is one of Al(NO3)3, Al(OC3H7)3, Al Cl3, and NaAlO2.

[0019] Furthermore, the silicon source is tetraethyl orthosilicate (TEOS).

[0020] Furthermore, the supercritical state treatment state is 8-15 MPa pressure, 33-50° C. temperature, and 12-48 hours.

[0021] Furthermore, the drying time in the drying oven is 24-48 hours, the calcination temperature in the muffle furnace is 500-600° C., and the calcination time is 6-8 hours.

[0022] Furthermore, the molar ratio of formaldehyde, acetaldehyde and ammonia is 1.0-1.2:1:2, the reaction in the reactor is carried out at normal pressure or a pressure of 1-5 bar, at a temperature range of 150-250° C., and the reaction time is 4-8 hours.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The catalyst of the present invention is synthesized by using a dual template agent and supercritical CO2 technology. The catalyst is used to catalyze the synthesis of pyridine base from formaldehyde, acetaldehyde and ammonia, thereby enhancing the specific surface area, pore size distribution and pore volume of the catalyst, and improving the catalytic activity and selectivity. At the same time, the catalyst provides acidic active sites and metallic active sites, which can simultaneously promote the reaction and improve the overall reaction efficiency. In the reaction of catalyzing the synthesis of pyridine base from formaldehyde, acetaldehyde and ammonia using the catalyst, the yield of pyridine is 55%, and the yield of 3,5-dimethylpyridine is 25%.

[0025] 2. The catalyst of the present invention uses a non-toxic silicon source and a dual template agent, which reduces energy consumption and waste generation. The catalyst can be regenerated by simple water washing, alcohol washing, roasting and other methods, which prolongs the reaction life of the catalyst and reduces production costs. DETAILED DESCRIPTION

[0026] 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.

[0027] Example 1: 1.0 g of dodecyl trimethyl ammonium bromide (CTAB) was dissolved in 100 mL of deionized water, and then 0.4 g of P123 was added and stirred at 40 ° C until it was completely dissolved to form a dual template solution. 7 mL of tetraethyl orthosilicate (TEOS) solution and 5 mL of NaOH solution (2M) were slowly added dropwise into the dual template solution and stirred to keep the solution uniform. A mixed solution of Zn (OAc) 2 and Al (NO3) 3 (Zn / Al molar ratio of 1:1, total metal content of 1.5 wt%) was added and 1 M NaOH solution was continued to be added dropwise to maintain the pH of the dual template solution at 10-11. Stirring for 6 hours at room temperature formed a gel-like substance. The prepared gel was transferred to a high-pressure reactor. The reactor valve was closed, CO2 was gradually introduced to increase the pressure to 8 MPa and heated to 35 ° C for 24 hours. After the supercritical treatment, the pressure in the reactor was slowly released, and the sample was taken out and placed in a 100 ° C drying oven for 24 hours. The dried sample was placed in a muffle furnace at 500° C. for 6 hours to remove the dual templates to obtain a Zn / Al-MCM-41 catalyst with dual functionality (acidic and metallic).

[0028] The Zn / Al-MCM-41 catalyst was used to catalyze the synthesis of pyridine base from formaldehyde, acetaldehyde and ammonia. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% ammonia water) were added to the reactor in a molar ratio of 1:1:2, and 1.5wt% of the Zn / Al-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C for 6 hours. The yield of pyridine was 31% and the yield of 3,5-dimethylpyridine was 7%.

[0029] The spent Zn / Al-MCM-41 catalyst was collected from the reactor. The catalyst was washed with distilled water and ethanol in turn to remove impurities and soluble residues attached to the surface. After filtration, the catalyst was dried in a vacuum drying oven at 60°C for 6 hours to remove residual moisture or solvent. The dried catalyst sample was placed in a porcelain boat and calcined in a muffle furnace at 550°C for 5 hours to regenerate the Zn / Al-MCM-41 catalyst. The regenerated Zn / Al-MCM-41 catalyst was used to catalyze formaldehyde, acetaldehyde and ammonia to synthesize pyridine base. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% ammonia water) were added to the reactor in a molar ratio of 1:1:2, and 1.5wt% of Zn / Al-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C. The reaction time was 6 hours, and the yield of pyridine was 32% and the yield of 3,5-dimethylpyridine was 6.5%.

[0030] Example 2: 1.0 g of dodecyl trimethyl ammonium bromide (CTAB) was dissolved in 100 mL of deionized water, and then 0.4 g of P123 was added and stirred at 40 ° C until it was completely dissolved to form a dual template solution. 7 mL of tetraethyl orthosilicate (TEOS) and 5 mL of NaOH solution (2M) were slowly added dropwise into the dual template solution and stirred to keep the solution uniform. A mixed solution of Zn (NO3) 2 and Al (NO3) 3 (Zn / Al molar ratio of 1:1, total metal content of 1.5 wt%) was added and 1 M NaOH solution was continued to be added dropwise to maintain the pH of the dual template solution at 10-11. Stirring for 6 hours at room temperature formed a gel-like substance. The prepared gel was transferred to a high-pressure reactor. The reactor valve was closed, CO2 was gradually introduced to increase the pressure to 8 MPa and heated to 35 ° C for 24 hours. After the supercritical treatment, the pressure in the reactor was slowly released, and the sample was taken out and placed in a 100 ° C drying oven for 24 hours. The dried sample was placed in a muffle furnace at 500°C for 6 hours to remove the dual templates to obtain a Zn / Al-MCM-41 catalyst with dual functionality (acidic and metallic).

[0031] The Zn / Al-MCM-41 catalyst was used to catalyze the synthesis of pyridine base from formaldehyde, acetaldehyde and ammonia. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% aqueous ammonia) were added to the reactor at a molar ratio of 1:1:2, and 1.5wt% of the Zn / Al-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C for 6 hours. The yield of pyridine was 55%, and the yield of 3,5-dimethylpyridine was 25%.

[0032] The spent Zn / Al-MCM-41 catalyst was collected from the reactor. The catalyst was washed with distilled water and ethanol in turn to remove impurities and soluble residues attached to the surface. After filtration, the catalyst was dried in a vacuum drying oven at 60°C for 6 hours to remove residual moisture or solvent. The dried catalyst sample was placed in a porcelain boat and calcined in a muffle furnace at 550°C for 5 hours to regenerate the Zn / Al-MCM-41 catalyst. The regenerated Zn / Al-MCM-41 catalyst was used to catalyze formaldehyde, acetaldehyde and ammonia to synthesize pyridine base. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% ammonia water) were added to the reactor in a molar ratio of 1:1:2, and 1.5wt% of Zn / Al-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C. The reaction time was 6 hours, and the yield of pyridine was 57% and the yield of 3,5-dimethylpyridine was 24%.

[0033] Example 3: 1.0 g of dodecyl trimethyl ammonium bromide (CTAB) was dissolved in 100 mL of deionized water, and then 0.4 g of P123 was added and stirred at 40 ° C until it was completely dissolved to form a dual template solution. 7 mL of tetraethyl orthosilicate (TEOS) and 5 mL of NaOH solution (2M) were slowly added dropwise into the dual template solution and stirred to keep the solution uniform. A mixed solution of Zn (C l) 2 and Al (NO3) 3 (Zn / Al molar ratio of 1:1, total metal content of 1.5 wt%) was added and 1 M NaOH solution was continued to be added dropwise to maintain the pH of the dual template solution at 10-11. Stirring for 6 hours at room temperature formed a gel-like substance. The prepared gel was transferred to a high-pressure reactor. The reactor valve was closed, CO2 was gradually introduced to increase the pressure to 8 MPa and heated to 35 ° C for 24 hours. After the supercritical treatment, the pressure in the reactor was slowly released, and the sample was taken out and placed in a 100 ° C drying oven for 24 hours. The dried sample was placed in a muffle furnace at 500° C. for 6 hours to remove the dual templates to obtain a Zn / Al-MCM-41 catalyst with dual functionality (acidic and metallic).

[0034] The Zn / Al-MCM-41 catalyst was used to catalyze the synthesis of pyridine base from formaldehyde, acetaldehyde and ammonia. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% aqueous ammonia) were added to the reactor in a molar ratio of 1:1:2, and 1.5wt% of the Zn / Al-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C for 6 hours. The yield of pyridine was 50% and the yield of 3,5-dimethylpyridine was 25%.

[0035] The spent Zn / A l-MCM-41 catalyst was collected from the reactor. The catalyst was washed with distilled water and ethanol in turn to remove impurities and soluble residues attached to the surface. After filtration, the catalyst was dried in a vacuum drying oven at 60°C for 6 hours to remove residual moisture or solvent. The dried catalyst sample was placed in a porcelain boat and calcined in a muffle furnace at 550°C for 5 hours to regenerate the Zn / A l-MCM-41 catalyst. The regenerated Zn / A l-MCM-41 catalyst was used to catalyze formaldehyde, acetaldehyde and ammonia to synthesize pyridine base. Formaldehyde (40% aqueous solution), acetaldehyde and ammonia (30% ammonia water) were added to the reactor in a molar ratio of 1:1:2, and 1.5wt% of Zn / A l-MCM-41 catalyst was added at the same time. The reaction was carried out at a pressure of 2 bar and a temperature range of 200°C. The reaction time was 6 hours, and the yield of pyridine was 51% and the yield of 3,5-dimethylpyridine was 25%.

[0036] When the molar ratio of zinc source to aluminum source is 1:1 and the total metal content is 1.5 wt%, the types of zinc source and aluminum source are changed as shown in Table 1.

[0037] Table 1: Yields of pyridine and 3,5-lutidine when the types of zinc and aluminum sources are different

[0038]

[0039] When the zinc source is Zn(NO3)2, the aluminum source is Al(NO3)3 and the molar ratio is 1:1, the total metal content is changed as shown in Table 2.

[0040] Table 2: Yield of pyridine and 3,5-lutidine at different total metal contents

[0041]

[0042]

[0043] When the zinc source is Zn(NO3)2, the aluminum source is Al(NO3)3, and the total metal content is 1.5wt%, the metal molar ratio is changed as shown in Table 3.

[0044] Table 3: Yield of pyridine and 3,5-dimethylpyridine at different metal molar ratios

[0045]

[0046] As shown in the above-mentioned Examples 1-3 and Tables 1, 2 and 3, different zinc sources and aluminum sources, total metal content and metal molar ratio will affect the acidity of Zn / Al-MCM-41 catalyst and the characteristics of metal sites, distribution and its interaction with the carrier, the pore structure and specific surface area of ​​the catalyst and the reactivity and impurity content of the precursor. These factors jointly determine the performance of the catalyst, resulting in different yields of catalytic synthesis of pyridine bases. When Zn(NO3)2 is the zinc source, Al(NO3)3 is the aluminum source, the total metal content is 1.5wt%, and the metal molar ratio is 1:1, the prepared Zn / Al-MCM-41 catalyst has the best catalytic effect, with a pyridine yield of 55% and a 3,5-lutidine yield of 25%. After the Zn / Al-MCM-41 catalyst is recovered, the reaction is continued to be catalyzed, with a pyridine yield of 57% and a 3,5-lutidine yield of 24%.

[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 bifunctional catalyst for pyridine base production, characterized in that: The following steps are involved: The dual template agent is dissolved in deionized water at a fixed mass ratio, a silicon source solution and a NaOH solution are added dropwise to the dual template agent solution, a mixed solution of a zinc source and an aluminum source is added, and the mixture is stirred at room temperature to form a gel; The prepared gel was transferred to a high-pressure reactor, pressurized and heated to a supercritical state, and then the sample was taken out and dried in a drying oven. The dried sample was calcined in a muffle furnace to remove the dual template agent, thereby obtaining a Zn / Al-MCM-41 catalyst with dual functionality. The Zn / Al-MCM-41 catalyst is used to catalyze formaldehyde, acetaldehyde and ammonia to synthesize pyridine base. Formaldehyde, acetaldehyde and ammonia are added into a reactor according to a molar ratio, and 2-10wt% of the Zn / Al-MCM-41 catalyst is added to carry out a catalytic reaction.

2. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The dual template agent is dodecyltrimethylammonium bromide and P123.

3. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The mass ratio of the dual templates is 1:0.1-0.

6. After the mixed solution of the zinc source and the aluminum source is added, the NaOH solution is continuously added dropwise to maintain the pH of the solution at 10-11.

4. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The volume ratio of the silicon source solution to the alkaline solution is 1-2:1, the molar ratio of the zinc source to the aluminum source is 0.5-2:1, and the total metal content is 0.5-2.5wt%.

5. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The zinc source is one of Zn(OAc)2, Zn(NO3)2, and Zn(Cl)2, and the aluminum source is one of Al(NO3)3, Al(OC3H7)3, AlCl3, and NaAlO2.

6. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The silicon source is tetraethyl orthosilicate.

7. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: After the gel is transferred to the high-pressure reactor, CO2 is introduced after closing the valve to pressurize and heat to a supercritical state.

8. The method for preparing a bifunctional catalyst for pyridine base production according to claim 7, characterized in that: The supercritical state treatment state is 8-15MPa pressure, 33-50°C temperature, and 12-48 hours.

9. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The drying temperature of the drying oven is 100-200°C, the drying time is 24-48 hours, the calcination temperature of the muffle furnace is 500-600°C, and the calcination time is 6-8 hours.

10. The method for preparing a bifunctional catalyst for pyridine base production according to claim 1, characterized in that: The molar ratio of formaldehyde, acetaldehyde and ammonia is 1.0-1.2:1:

2. The reaction in the reactor is carried out at normal pressure or a pressure of 1-5 bar, at a temperature range of 150-250° C., and the reaction time is 4-8 hours.

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