A method for the catalytic synthesis of 3-methylpyridine from pyridine using a catalyst.

Abstract

This invention discloses a method for the catalytic synthesis of 3-methylpyridine from pyridine. A nitrate mixture is dropwise added to an excess sodium hydroxide solution under magnetic stirring. A ferrite catalyst is prepared by co-precipitation. The ferrite catalyst is activated at high temperature. The molar ratio of methanol and pyridine is adjusted to form a mixed solution. The reaction temperature, reaction pressure, and feed flow rate are adjusted. The mixed solution is introduced and vaporized. The vaporized pyridine-methanol mixture undergoes a catalytic reaction with the catalyst bed in the reactor. The product is discharged through the outlet and collected by condensation, yielding highly selective 3-methylpyridine. This invention uses pyridine and methanol as raw materials and, under the action of a ferrite catalyst, achieves highly selective synthesis of 3-methylpyridine with a yield exceeding 86%, reducing production costs and improving economic efficiency.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis and preparation technology, specifically to a method for synthesizing 3-methylpyridine by catalyst catalysis of pyridine. Background Technology

[0002] 3-Methylpyridine is an important chemical raw material and organic intermediate, mainly used in pesticides, pharmaceuticals, feed additives, and fragrances. 3-Methylpyridine can be used to produce nicotinic acid, nicotinamide, and 3-cyanopyridine, which are used in the pharmaceutical field. It is also an intermediate in the synthesis of various derivatives, such as 2-chloro-5-chloromethylpyridine, 2-chloro-3-methylpyridine, 2-chloro-5-trifluoromethylpyridine, and 2,3-dichloro-5-trifluoromethylpyridine, which in turn can be used to produce a range of pesticide products.

[0003] Currently, there are many methods for synthesizing 3-methylpyridine, including formaldehyde, acetaldehyde and ammonia; formaldehyde, ethanol and ammonia; acrolein, propionaldehyde and ammonia; and pyridine alkylation. Among these, pyridine alkylation for the synthesis of 3-methylpyridine achieves high efficiency and selectivity and is a future research trend.

[0004] Chinese patent application CN111760584A discloses a method for preparing a novel methylpyridine catalyst. The method involves mixing and stirring water, concentrated hydrochloric acid, and P123, then adding TEOS dropwise, followed by the addition of a silicate and composite silicate solution containing metal ions to ultimately obtain a novel catalyst based on SBA-15 mesoporous molecular sieve loaded with metal ions. This catalyst exhibits high selectivity and conversion rate in the catalytic synthesis of methylpyridine, high thermal stability, and a long catalytic activity cycle.

[0005] Chinese Patent CN115368298B discloses a method for synthesizing 3-methylpyridine from pyridine and methanol. It uses a supported heteropolyacid catalyst prepared from activated carbon or MCN-41 molecular sieve supported on solid acids such as phosphotungstic acid, phosphosilicate, and phosphomolybdic acid. The raw materials are synthesized into 3-methylpyridine via a fluidized bed reactor. Both methods result in low conversion and yield of 3-methylpyridine, and the products are difficult to separate. Summary of the Invention

[0006] The purpose of this invention is to provide a method for synthesizing 3-methylpyridine by catalysis of pyridine. This invention uses pyridine and methanol as raw materials and, under the action of a ferrite catalyst, can achieve highly selective synthesis of 3-methylpyridine, thereby reducing production costs and improving economic efficiency. This solves the problems of low yield, numerous by-products, and difficulty in separating the products in the existing 3-methylpyridine synthesis processes mentioned in the background art.

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

[0008] A method for synthesizing 3-methylpyridine from pyridine using a catalyst includes the following steps:

[0009] Step 1: Mix nitrate solutions according to stoichiometric ratio to obtain a nitrate mixture. Add the nitrate mixture dropwise to an excess sodium hydroxide solution under magnetic stirring. After reacting for 10 hours, filter the solution, wash with deionized water, dry in a 100℃ oven for 14 hours, calcine at 400℃ for 16 hours, and then compress into tablets to obtain a ferrite catalyst Cu. 1-x Co x Fe2O4;

[0010] Step 2: High-temperature activation of Cu ferrite catalyst before reaction 1-x Co x Fe2O4 was used to preheat the reactor and introduce nitrogen gas. The molar ratio of raw materials methanol and pyridine was adjusted to prepare a mixed solution. The reaction temperature, reaction pressure, and feed flow rate were also adjusted.

[0011] Step 3: The mixed solution from Step 2 is introduced and vaporized. The vaporized pyridine-methanol mixture undergoes a catalytic reaction with the catalyst layer in the reactor. The generated product is discharged through the outlet and then condensed and collected to obtain highly selective synthetic 3-methylpyridine.

[0012] Furthermore, the ferrite catalyst Cu 1-x Co x The value of x in Fe2O4 ranges from 0 to 1.

[0013] Furthermore, the nitrate solution comprises at least two nitrates selected from copper nitrate, cobalt nitrate, and ferric nitrate.

[0014] Furthermore, the concentration of the nitrate solution is controlled at 0.5-1.0 mol / L.

[0015] Furthermore, the precipitation process in step 1 is carried out at room temperature, and the reaction solution is maintained at pH 10.

[0016] Furthermore, the roasting process in step 1 is carried out in an air atmosphere.

[0017] Furthermore, the molar ratio of methanol to pyridine in step 2 is 1.5.

[0018] Furthermore, the reaction temperature in step 2 is 300-500℃, the pressure is 0.02-0.1MPa, and the material feed rate is 0.05-0.1g / min.

[0019] Furthermore, the ferrite catalyst Cu in step 2 1-x Co x Fe2O4 was activated at 500℃ for two hours.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention prepares a ferrite catalyst by co-precipitation of a mixture of multiple transition metal nitrates in a certain molar ratio using pyridine and methanol as raw materials. Using a fixed-bed reactor under controlled temperature and space velocity conditions, the yield of 3-methylpyridine can reach over 86%, representing a significant improvement over existing technologies. The ferrite catalyst of this invention, by adjusting the ratio of the two transition metal elements, simplifies the preparation process, exhibits high thermal stability and a long catalytic activity cycle, and demonstrates high catalytic activity and selectivity for pyridine alkylation reactions. It can be applied to the 3-methylpyridine synthesis process to improve the yield of 3-methylpyridine. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below; however, the embodiments of the present invention are not limited thereto. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] A method for synthesizing 3-methylpyridine from pyridine using a catalyst includes the following steps:

[0024] Step 1: Preparation of Cu ferrite catalyst by co-precipitation method 1-x Co x Fe2O4

[0025] A nitrate mixture was obtained by mixing nitrate solutions according to stoichiometric ratios. The nitrate solution included at least two nitrates selected from copper nitrate, cobalt nitrate, and ferric nitrate. The concentration of the nitrate solution was controlled at 0.5-1.0 mol / L to avoid powder agglomeration at high concentrations and low yields at low concentrations. The nitrate mixture was added dropwise to an excess sodium hydroxide solution under magnetic stirring. After reacting for 10 hours, the mixture was filtered and washed with deionized water. The precipitation process was carried out at room temperature, and the pH of the reaction solution was maintained at 10. After filtration, the mixture was dried in an oven at 100°C for 14 hours and calcined at 400°C for 16 hours in an air atmosphere. The resulting product was then pressed into tablets to obtain a ferrite catalyst, Cu. 1-x Co x Fe2O4, where x ranges from 0 to 1;

[0026] Step 2: Using pyridine and methanol as raw materials, the obtained ferrite catalyst Cu... 1-x Co x Fe2O4 Synthesis of 3-methylpyridine

[0027] Before the reaction, the ferrite catalyst Cu 1-x Co xFe2O4 was activated at 500℃ for two hours, the reactor was preheated and nitrogen gas was introduced, and a mixed solution was prepared by adjusting the molar ratio of methanol and pyridine to 1.5. The reaction temperature was adjusted to 300-500℃, the reaction pressure to 0.02-0.1MPa, and the feed flow rate to 0.05-0.1g / min. The mixed solution from step 2 was introduced and vaporized. The vaporized pyridine-methanol mixture underwent a catalytic reaction with the catalyst layer in the reactor. The product was discharged through the outlet and collected by condensation, yielding highly selective synthetic 3-methylpyridine.

[0028] The following examples illustrate the preparation of ferrite catalysts from mixed solutions of metal nitrates with different stoichiometric ratios.

[0029] Example 1: Cobalt nitrate and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 1). The mixture was added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite CoFe2O4 catalyst 1.

[0030] 10g of copper-cobalt ferrite CoFe2O4 catalyst 1 was loaded into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was carried out at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and the pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalyze the reaction between the catalyst layer and the reactor tube. The resulting product was discharged through the outlet and collected by condensation.

[0031] Example 2: Copper nitrate, cobalt nitrate, and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0.8). The mixture was then added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite (Cu). 0.2 Co 0.8 Fe2O4 catalyst 2.

[0032] 10g of copper-cobalt ferrite Cu 0.2 Co 0.8Fe₂O₄ catalyst 2 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was performed at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and a pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalytically react with the catalyst layer in the tubular reactor. The resulting product was discharged through the outlet and collected by condensation.

[0033] Example 3: Copper nitrate, cobalt nitrate, and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0.6). The mixture was then added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite (Cu). 0.4 Co 0.6 Fe2O4 catalyst 3.

[0034] 10g of copper-cobalt ferrite Cu 0.4 Co 0.6 Fe2O4 catalyst 3 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and then nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was carried out at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and the pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalytically react with the catalyst layer in the tubular reactor. The resulting product was discharged through the outlet and collected by condensation.

[0035] Example 4: Copper nitrate, cobalt nitrate, and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0.5). The mixture was then added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite (Cu). 0.5 Co 0.5 Fe2O4 catalyst 4.

[0036] 10g of copper-cobalt ferrite Cu 0.5 Co 0.5Fe₂O₄ catalyst 4 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and then nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was carried out at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and the pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalytically react with the catalyst layer in the tubular reactor. The resulting product was discharged through the outlet and collected by condensation.

[0037] Example 5: Copper nitrate, cobalt nitrate, and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0.4). The mixture was then added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite (Cu). 0.6 Co 0.4 Fe2O4 catalyst 5.

[0038] 10g of copper-cobalt ferrite Cu 0.6 Co 0.4 Fe₂O₄ catalyst 5 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and then nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was performed at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and the pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalytically react with the catalyst layer in the tubular reactor. The resulting product was discharged through the outlet and collected by condensation.

[0039] Example 6: Copper nitrate, cobalt nitrate, and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0.2). The mixture was then added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite (Cu). 0.8 Co 0.2 Fe2O4 catalyst 6.

[0040] 10g of copper-cobalt ferrite Cu 0.8 Co 0.2Fe2O4 catalyst 6 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and then nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was carried out at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and the pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalytically react with the catalyst layer in the tubular reactor. The resulting product was discharged through the outlet and collected by condensation.

[0041] Example 7: Copper nitrate and ferric nitrate solutions were uniformly mixed at a stoichiometric ratio (x = 0). The mixture was added dropwise to an excess sodium hydroxide solution, maintaining pH = 10. The mixture was stirred, allowed to stand for 10 hours, dried, and calcined at 400°C for 16 hours to obtain copper-cobalt ferrite CuFe2O4 catalyst 7.

[0042] 10g of copper-cobalt ferrite CuFe2O4 catalyst 7 was packed into a fixed-bed reactor tube. The raw materials, methanol and pyridine, were mixed in a molar ratio of 1.5. The reaction temperature was 400℃, the reaction pressure was 0.05MPa, the reaction time was 3h, and the feed flow rate was 0.1g / min. Before the reaction, the heating jacket of the tubular reactor was opened, and nitrogen gas was introduced by opening the ball valve in the nitrogen pipe. Activation was performed at 500℃ for 2 hours. After activation, the temperature was lowered to the reaction temperature, and a pyridine-methanol mixed gas was introduced by opening the ball valve in the pyridine and methanol inlet pipes. Then, nitrogen gas was introduced by opening the ball valve in the feed port. This allowed the nitrogen gas and the pyridine-methanol mixed gas to catalyze the reaction between the catalyst layer and the reactor tube. The resulting product was discharged through the outlet and collected by condensation.

[0043] After synthesizing 3-methylpyridine using the catalysts of Examples 1-7, the data shown in Table 1 below were obtained.

[0044] Table 1. Effects of various catalysts on the conversion, yield, and selectivity of 3-methylpyridine

[0045] Example 1 76.21 51.13 67.09 Example 2 78.79 55.21 70.07 Example 3 83.69 57.17 68.31 Example 4 80.33 57.45 71.52 Example 5 83.79 63.84 76.19 Example 6 85.39 69.25 80.86 Example 7 85.31 60.06 70.40

[0046] As shown in Table 1, the catalytic yield of alkylpyridine synthesis can be controlled by adjusting the copper-cobalt transition metal content, and higher catalytic activity can be achieved through this control. The copper-to-cobalt ratio was 4:1 (Cu in Example 6 copper-cobalt ferrite). 0.8 Co 0.2 When using Fe2O4 catalyst 6), the yield of 3-methylpyridine reached 69%, and the selectivity for 3-methylpyridine was 80%. This indicates that among the seven catalysts in Examples 1-7, the copper-cobalt ferrite Cu catalyst in Example 6 was the most effective. 0.8 Co0.2 Fe2O4 catalyst 6 showed the best conversion of pyridine, yield of 3-methylpyridine, and selectivity.

[0047] The following examples illustrate copper-cobalt ferrite Cu 0.8 Co 0.2 Investigation of process conditions for the synthesis of 3-methylpyridine using Fe2O4 catalyst 6:

[0048] 10g of copper-cobalt ferrite Cu 0.8 Co 0.2 Fe2O4 catalyst 6 was packed into a fixed-bed reactor tube, and the molar ratio of methanol and pyridine was adjusted to form a mixed solution. The reaction temperature, reaction pressure, reaction time, and feed flow rate were adjusted. The pyridine-methanol mixture reacted catalyzed with the catalyst bed in the tubular reactor. The product was discharged through the outlet and then condensed and collected. The process steps of Examples 8-19 were the same, except that the molar ratio of methanol and pyridine, feed flow rate, reaction temperature, and reaction pressure were different. The data are shown in Table 2 below.

[0049] Table 2. Effects of process conditions on copper-cobalt ferrite (Cu) 0.8 Co 0.2 Effects of Fe2O4 catalyst 6 on conversion, yield and selectivity

[0050]

[0051] The results are shown in Table 2, using copper-cobalt ferrite Cu. 0.8 Co 0.2 Fe2O4 catalyst 6, with a methanol to pyridine molar ratio of 2.5 and a feed flow rate of 0.08 g·min⁻¹. -1 Under conditions of reaction temperature 400℃ and reaction pressure 0.07 MPa, the conversion rate of pyridine reached 95%, the yield of 3-methylpyridine reached 86%, and the selectivity reached 90%. At this time, the catalyst obtained high catalytic activity, which is higher than the 82.5% yield of the 3-methylpyridine synthesis reaction disclosed in the prior art announcement CN115368298B. It also showed better catalytic activity and selectivity for 3-methylpyridine.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing 3-methylpyridine from pyridine using a catalyst, characterized in that, Includes the following steps: Step 1: Mix nitrate solutions according to stoichiometric ratio to obtain a nitrate mixture. Add the nitrate mixture dropwise to an excess sodium hydroxide solution under magnetic stirring. After reacting for 10 hours, filter the solution, wash with deionized water, dry in a 100℃ oven for 14 hours, calcine at 400℃ for 16 hours, and then compress into tablets to obtain a ferrite catalyst. ; Step 2: Activation of ferrite catalysts before reaction The reactor is preheated and nitrogen is introduced. The molar ratio of methanol and pyridine is adjusted to prepare a mixed solution. The reaction temperature, reaction pressure, and feed flow rate are adjusted. Step 3: The mixed solution from Step 2 is introduced and vaporized. The vaporized pyridine-methanol mixture undergoes a catalytic reaction with the catalyst layer in the reactor. The generated product is discharged through the outlet and then condensed and collected to obtain highly selective synthetic 3-methylpyridine. The for or ; The nitrate solution is a copper nitrate solution, a cobalt nitrate solution, or a ferric nitrate solution.

2. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, The concentration of the nitrate solution is controlled at 0.5-1.0 mol / L.

3. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, The reaction process in step 1 is carried out at room temperature, and the reaction solution is maintained at pH 10.

4. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, The roasting process in step 1 is carried out in an air atmosphere.

5. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, The molar ratio of methanol to pyridine in step 2 is 1.5-3.

6. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, The reaction temperature in step 2 is 300-500℃, the reaction pressure is 0.02-0.1MPa, and the material feed rate is 0.05-0.1g / min.

7. The method for synthesizing 3-methylpyridine from pyridine using the catalyst according to claim 1, characterized in that, Ferrite catalyst in step 2 Activate at 500℃ for two hours.

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