Preparation of supported ruthenium-based catalyst and application of supported ruthenium-based catalyst in preparation of 3-methylpyridine by catalyzing dehydrogenation of 3-methylpiperidine

Abstract

The invention provides preparation of a supported ruthenium-based catalyst and application of the supported ruthenium-based catalyst to preparation of 3-methylpyridine by catalyzing dehydrogenation of 3-methylpiperidine. The catalyst is prepared by an impregnation method, ruthenium metal is uniformly loaded on a carrier with a high specific surface area and a stable structure, and the dispersity and the utilization rate of active metal are remarkably improved. In an inert atmosphere, 3-methylpiperidine is subjected to an efficient dehydrogenation reaction under the condition of 230-320 DEG C through the catalyst to generate 3-methylpyridine. Through optimized reaction conditions, the reaction can be efficiently carried out under mild conditions, the service life of the catalyst is remarkably prolonged, and no obvious inactivation phenomenon exists after long-term operation. Compared with a traditional palladium-based catalyst, the ruthenium-based catalyst has the remarkable cost advantage, the cost of ruthenium metal is far lower than that of palladium metal, and the overall cost of catalyst production and reaction is reduced; meanwhile, the ruthenium-based catalyst has higher stability under a high-temperature condition, and the problem of catalyst deactivation caused by oxidation or sintering is avoided.

Description

Technical Field

[0001] The invention relates to the field of catalysts, in particular to a supported ruthenium-based catalyst and application thereof in preparing 3-methylpyridine by dehydrogenation of 3-methylpiperidine. Background Art

[0002] 3-Methylpyridine (also known as β-picolin) is an important organic compound widely used in the fields of medicine, agriculture and fine chemicals. Its most common use is in the synthesis of nicotinic acid and nicotinamide, which are important precursors of vitamin B3 ( Chem-Asian J, 2024, 19 (18), e202400467.). In addition, 3-methylpyridine is also widely used in the synthesis of herbicides, pesticides, dye intermediates, fragrances and other fine chemicals. With the increasing demand for fine chemicals, the synthesis of 3-methylpyridine has become an important research direction in the field of chemical synthesis.

[0003] At present, the industrial synthesis of 3-methylpyridine mainly adopts the aldehyde-ammonia method, with formaldehyde, acetaldehyde and ammonia as raw materials. Although the reaction process of this method is relatively simple and the raw material cost is low, it has many problems, including poor reaction selectivity, harsh reaction conditions (such as high temperature and high pressure) and many side reactions. Specifically, the reaction products include not only 3-methylpyridine, but also pyridine, 2-methylpyridine and 4-methylpyridine, among which 3-methylpyridine is usually a by-product, resulting in its low yield. For example, patent CN1566093 reports a metal oxide catalyst loaded with lead or cobalt-lead mixture on ZSM-5 zeolite. The total yield of pyridine and 3-methylpyridine in this method is 81%, but the yield of 3-methylpyridine is only 25%. In addition, the aldehyde-ammonia method also faces the influence of catalyst acidity on reaction selectivity. Studies have shown that the acidity of the catalyst has different effects on different reaction steps. Excessive acidity may cause catalyst sintering and reduce reaction selectivity. Therefore, although this process has been widely used in pyridine production, it still faces many challenges in improving the yield of 3-methylpyridine and needs further optimization.

[0004] In response to these problems, the synthesis of 3-methylpyridine through the dehydrogenation reaction of 3-methylpiperidine has become a potential alternative route. This method has milder reaction conditions and a simple operation process, so it has attracted the attention of more and more researchers. The traditional 3-methylpiperidine dehydrogenation reaction usually uses the precious metal palladium (Pd) as a catalyst (US 4401819). Although palladium catalysts have high catalytic activity in this reaction, they are expensive, resulting in high overall reaction costs. In addition, palladium catalysts are easily deactivated under high temperature conditions, and palladium particles are prone to aggregation or oxidation, which in turn affects the catalytic performance and reaction efficiency. Therefore, the development of a more economical, stable and efficient catalyst has become a research hotspot for the dehydrogenation reaction of 3-methylpiperidine. Summary of the invention

[0005] To solve the above problems, the present invention provides a new type of supported ruthenium-based catalyst for the dehydrogenation reaction of 3-methylpiperidine to prepare 3-methylpyridine. The catalyst significantly improves the dispersibility and stability of the catalyst by loading ruthenium metal onto a mesoporous molecular sieve with a high surface area, thereby improving the catalytic efficiency and selectivity of the reaction. Compared with traditional palladium catalysts and existing ruthenium catalysts, the supported ruthenium-based catalyst of the present invention can achieve efficient dehydrogenation reaction at a lower temperature (230-320°C), and has a longer service life and good catalytic stability, which can effectively reduce production costs and provide a more economical and sustainable synthesis route.

[0006] The present invention adopts the following technical solution: The present invention provides a method for preparing 3-methylpyridine by dehydrogenation of 3-methylpiperidine using a supported ruthenium-based catalyst. Under the action of the supported ruthenium catalyst, 3-methylpiperidine is introduced into a fixed bed reactor at a temperature of 230-320° C. under an inert atmosphere for 0.5-3 h⁻¹, and a dehydrogenation reaction is carried out to obtain 3-methylpyridine.

[0007] The active component Ru of the supported Ru catalyst has a loading amount of 0.5-5 wt.%, preferably 2 wt.%; the metal precursor of Ru is ruthenium trichloride, ruthenium acetylacetonate or triruthenium dodecacarbonyl, preferably triruthenium dodecacarbonyl.

[0008] The carrier of the supported Ru catalyst is one or more of silicon dioxide, titanium dioxide, carbon, aluminum oxide or mesoporous molecular sieve, preferably mesoporous molecular sieve.

[0009] The preparation method of the supported Ru-based catalyst comprises the following steps: adding a carrier of the supported Ru catalyst to a ruthenium metal precursor solution; evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, and then completely drying the mixture in an oven at 55-65° C. to obtain a precursor of the supported Ru catalyst; grinding the precursor and annealing it in a tubular furnace in an inert atmosphere for 1-3 hours; taking out the calcined solid powder, grinding it, and reducing it in a 5% H2 / Ar atmosphere for 1-3 hours to finally obtain the supported Ru-based catalyst.

[0010] The annealing temperature in a tube furnace under an inert atmosphere is 150-250°C, and the heating rate is 5°C / min, preferably 200°C.

[0011] The reduction temperature is 500-550°C in a 5% H2 / Ar atmosphere, and the heating rate is 2°C / min, preferably 550°C.

[0012] The ruthenium-based catalyst of the present invention not only has excellent catalytic performance, but also has significant economic benefits: 1) High selectivity and high yield: The catalyst can significantly improve the yield and selectivity of 3-methylpyridine. Compared with the traditional aldehyde-ammonia method or palladium catalysis method, a higher yield of the target product can be obtained at a lower temperature with less by-product generation; 2) Low cost: Ruthenium metal has a lower cost than precious metals such as palladium and platinum. By optimizing the loading amount of ruthenium metal, the catalyst of the present invention can significantly reduce the cost of the catalyst while ensuring the catalytic effect. In addition, due to the oxidation resistance and high temperature stability of ruthenium metal, the service life of the catalyst is long, avoiding the high cost of frequent catalyst replacement; 3) Mild reaction conditions: The catalyst can catalyze reactions at lower temperatures. Compared with traditional palladium catalysts, which require higher energy consumption to maintain high-temperature reaction conditions, the present invention can significantly reduce energy consumption and equipment requirements during the reaction.

[0013] In summary, the present invention has the following advantages over the prior art: 1) Lower cost: The cost of ruthenium metal is much lower than that of palladium metal, so the production cost of the catalyst can be greatly reduced and it has higher economic efficiency in large-scale industrial applications; 2) Longer catalytic stability: Ruthenium metal has better stability than palladium metal under high temperature reaction conditions, avoiding the deactivation of the catalyst due to oxidation or sintering, and can operate stably for a long time; 3) Excellent reaction efficiency: The ruthenium-based catalyst of the present invention can carry out dehydrogenation reaction at a relatively low reaction temperature and has a relatively high catalytic efficiency and selectivity, thereby increasing the overall yield of the reaction and reducing the generation of by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a transmission electron microscope image of the Ru / SBA-15 catalyst obtained in Example 1 of the present invention.

[0015] Figure 2 This is a transmission electron microscope image of the Ru / SiO2 catalyst obtained in Example 2 of the present invention.

[0016] Figure 3 This is a transmission electron microscope image of the Ru / TiO2 catalyst obtained in Example 3 of the present invention.

[0017] Figure 4 This is a transmission electron microscope image of the Ru / C catalyst obtained in Example 4 of the present invention.

[0018] Figure 5 This is a transmission electron microscope image of the Ru / Al2O3 catalyst obtained in Example 5 of the present invention.

[0019] Figure 6 XRD diffraction patterns of the catalysts obtained in Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0020] In view of the deficiencies in the prior art, the inventors have successfully proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the present invention, not all. Based on the embodiments of the present invention, all other embodiments that can be obtained by ordinary technicians in this field without making creative work are included in the protection scope of the present invention.

[0021] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0022] The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent stores. The loading amounts are all in mass fraction (wt%) Example 1 Preparation of Ru / SBA-15 catalyst: Weigh 500 mg SBA-15 solid powder and add it into the prepared ruthenium metal solution (weigh 0.020 g triruthenium dodecacarbonyl (Ru3(CO) 12) solid powder, dissolved in acetone to prepare); after evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, the mixture was completely dried in an oven at 55-65°C to obtain a precursor of a supported ruthenium catalyst; the precursor was ground and annealed at 200°C in a tube furnace in an inert atmosphere for 2 hours; the annealed solid powder was taken out, ground, and then reduced at 550°C for 2 hours in a 5% H2 / Ar (H2 and Ar gas mixture, the volume fraction of H2 is 5%) atmosphere to finally obtain a Ru / SBA-15 catalyst (catalyst 1).

[0023] Example 2 Preparation of Ru / SiO2 catalyst: Weigh 500 mg SiO2 solid powder and add it into the prepared ruthenium metal solution (weigh 0.020 g triruthenium dodecacarbonyl (Ru3(CO) 12 ) solid powder, dissolved in acetone to prepare); after evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, the mixture was completely dried in an oven at 55~65°C to obtain a precursor of a supported ruthenium catalyst; the precursor was ground and annealed at 200°C in a tube furnace in an inert atmosphere for 2 hours; the annealed solid powder was taken out, ground, and then reduced at 550°C for 2 hours in a 5% H2 / Ar (H2 and Ar gas mixture, the volume fraction of H2 is 5%) atmosphere to finally obtain a Ru / SiO2 catalyst (catalyst 2).

[0024] Example 3 Preparation of Ru / TiO2 catalyst: Weigh 500 mg TiO2 solid powder and add it into the prepared ruthenium metal solution (weigh 0.020 g triruthenium dodecacarbonyl (Ru3(CO) 12 ) solid powder, dissolved in acetone to prepare); after evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, the mixture was completely dried in an oven at 55~65°C to obtain a precursor of a supported ruthenium catalyst; the precursor was ground and annealed at 200°C in a tube furnace in an inert atmosphere for 2 hours; the annealed solid powder was taken out, ground, and then reduced at 550°C for 2 hours in a 5% H2 / Ar (H2 and Ar gas mixture, the volume fraction of H2 is 5%) atmosphere to finally obtain a Ru / TiO2 catalyst (catalyst 3).

[0025] Example 4 Preparation of Ru / C catalyst: Weigh 500 mg of carbon black powder and add it into the prepared ruthenium metal solution (weigh 0.020 g of triruthenium dodecacarbonyl (Ru3(CO) 12) solid powder, dissolved in acetone to prepare); after evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, the mixture was completely dried in an oven at 55~65°C to obtain a precursor of a supported ruthenium catalyst; the precursor was ground and placed in a tube furnace in an inert atmosphere for annealing at 200°C for 2 hours; the annealed solid powder was taken out, ground, and then reduced at 550°C for 2 hours in a 5% H2 / Ar (H2 and Ar gas mixture, the volume fraction of H2 is 5%) atmosphere to finally obtain a Ru / C catalyst (catalyst 4).

[0026] Example 5 Preparation of Ru / Al2O3 catalyst: Weigh 500 mg of carbon black powder and add it into the prepared ruthenium metal solution (weigh 0.020 g of triruthenium dodecacarbonyl (Ru3(CO) 12 ) solid powder, dissolved in acetone to prepare); after evaporating a large amount of solvent from the obtained liquid mixture under negative pressure, the mixture was completely dried in an oven at 55~65°C to obtain a precursor of a supported ruthenium catalyst; the precursor was ground and placed in a tube furnace in an inert atmosphere for annealing at 200°C for 2 hours; the annealed solid powder was taken out, ground, and then reduced at 550°C for 2 hours in a 5% H2 / Ar (H2 and Ar gas mixture, the volume fraction of H2 is 5%) atmosphere to finally obtain a Ru / Al2O3 catalyst (catalyst 5).

[0027] Embodiment 6-10 200 mg of catalyst 1-5 was loaded into a fixed bed reactor. The internal device of the fixed bed reactor was made of stainless steel and had a volume of 50 mL. In the reactor, the catalysts were fixed with quartz sand on the upper and lower layers. At the beginning of the reaction operation, nitrogen (N2) was first introduced into the reactor at a regular flow rate to remove oxygen from the system and adjust the atmosphere inside the reactor to an inert environment. Subsequently, 3-methylpiperidine (C6H 13 N) was pumped into the reactor to ensure that the feed flow rate matched the gas flow rate of the reactor to avoid excessive feed rate leading to too fast reaction. The reaction temperature was set to 270°C, and the reactor temperature was accurately controlled by a heating device to keep the reaction stable. The reaction was carried out at normal pressure without additional pressurization. Nitrogen was passed into the reactor as a carrier gas and carried the reactants through the catalyst layer. During the reaction, samples were collected regularly by gas chromatography (GC) to analyze the conversion rate of the reactants and the yield and selectivity of 3-methylpyridine (C6H7N). At the end of the reaction, nitrogen was continued to be passed into the reactor to purge the reactor, stop feeding and empty the residual reactants in the system. The conversion rate of 3-methylpiperidine was determined by gas chromatography analysis, and the results are shown in Table 1.

[0028] Embodiment 11 200 mg of catalyst 1 was loaded into a fixed bed reactor. The internal device of the fixed bed reactor was made of stainless steel and had a volume of 50 mL. In the reactor, the catalyst was fixed with quartz sand on the upper and lower layers. At the beginning of the reaction operation, nitrogen (N2) was first passed into the reactor at a regular flow rate to remove oxygen from the system and adjust the atmosphere inside the reactor to an inert environment. Subsequently, 3-methylpiperidine (C6H 13 N) was pumped into the reactor to ensure that the feed flow rate matched the gas flow rate of the reactor to avoid excessive feed rate causing the reaction to proceed too quickly. The reaction temperature was set to 230°C, and the reactor temperature was accurately controlled by a heating device to keep the reaction stable. The reaction was carried out at normal pressure without additional pressurization. Nitrogen was passed into the reactor as a carrier gas and carried the reactants through the catalyst layer. During the reaction, samples were collected regularly by gas chromatography (GC) to analyze the conversion rate of the reactants and the yield and selectivity of 3-methylpyridine (C6H7N). At the end of the reaction, nitrogen was continued to be passed into the reactor to purge the reactor, stop feeding and empty the residual reactants in the system. The conversion rate of 3-methylpiperidine was determined by gas chromatography analysis, and the results are shown in Table 1.

[0029] Example 12 200 mg of catalyst 1 was loaded into a fixed bed reactor. The internal device of the fixed bed reactor was made of stainless steel and had a volume of 50 mL. In the reactor, the catalyst was fixed with quartz sand on the upper and lower layers. At the beginning of the reaction operation, nitrogen (N2) was first passed into the reactor at a regular flow rate to remove oxygen from the system and adjust the atmosphere inside the reactor to an inert environment. Subsequently, 3-methylpiperidine (C6H 13 N) was pumped into the reactor to ensure that the feed flow rate matched the gas flow rate of the reactor to avoid excessive feed rate leading to too fast reaction. The reaction temperature was set to 250°C, and the reactor temperature was accurately controlled by a heating device to keep the reaction stable. The reaction was carried out at normal pressure without additional pressurization. Nitrogen was passed into the reactor as a carrier gas and carried the reactants through the catalyst layer. During the reaction, samples were collected regularly by gas chromatography (GC) to analyze the conversion rate of the reactants and the yield and selectivity of 3-methylpyridine (C6H7N). At the end of the reaction, nitrogen was continued to be passed into the reactor to purge the reactor, stop feeding and empty the residual reactants in the system. The conversion rate of 3-methylpiperidine was determined by gas chromatography analysis, and the results are shown in Table 1.

[0030] Embodiment 13 200 mg of catalyst 1 was loaded into a fixed bed reactor. The internal device of the fixed bed reactor was made of stainless steel and had a volume of 50 mL. In the reactor, the catalyst was fixed with quartz sand on the upper and lower layers. At the beginning of the reaction operation, nitrogen (N2) was first passed into the reactor at a regular flow rate to remove oxygen from the system and adjust the atmosphere inside the reactor to an inert environment. Subsequently, 3-methylpiperidine (C6H 13 N) was pumped into the reactor to ensure that the feed flow rate matched the gas flow rate of the reactor to avoid excessively high feed rates leading to too fast reaction. The reaction temperature was set to 320°C, and the reactor temperature was precisely controlled by a heating device to keep the reaction stable. The reaction was carried out at normal pressure without additional pressurization. Nitrogen was passed into the reactor as a carrier gas and carried the reactants through the catalyst layer. During the reaction, samples were collected regularly by gas chromatography (GC) to analyze the conversion rate of the reactants and the yield and selectivity of 3-methylpyridine (C6H7N). At the end of the reaction, nitrogen was continued to be passed into the reactor to purge the reactor, stop feeding and empty the residual reactants in the system. The conversion rate of 3-methylpiperidine was determined by gas chromatography, and the results are shown in Table 1.

[0031] Table 1 Reaction results of Examples 6-13 As shown in Table 1, the catalyst of the present invention shows high catalytic activity and good stability in long-term reaction, and the by-product generation amount is low, ensuring the production of 3-methylpyridine with high selectivity. The catalyst is not only suitable for 3-methylpiperidine dehydrogenation reaction, but also has a wide range of application prospects, and can provide an economical and sustainable solution for the efficient synthesis of 3-methylpyridine. In addition, the operating conditions required for the catalyst of the present invention in the catalytic reaction process are relatively mild, further improving the feasibility of industrial application.

[0032] In summary, the present invention provides a new type of ruthenium-based catalyst, which is successfully used in the dehydrogenation reaction of 3-methylpiperidine to prepare 3-methylpyridine. The catalyst uses a mesoporous molecular sieve as a carrier, and loads ruthenium metal by an impregnation method, which significantly improves the dispersibility and stability of the catalyst. Under mild reaction conditions (230-320°C), the ruthenium-based catalyst of the present invention can efficiently catalyze the dehydrogenation reaction of 3-methylpiperidine to obtain a higher yield and selectivity of 3-methylpyridine. Compared with traditional palladium-based catalysts, the catalyst of the present invention has lower cost, higher stability and longer service life, overcoming the problems of expensive catalysts and easy deactivation in the prior art.

[0033] The above description is only an embodiment of the present invention. Any modification, equivalent substitution, improvement, etc. of the present invention should be included in the protection scope of the present invention.

Claims

1. A supported ruthenium-based catalyst, characterized in that: The invention comprises a carrier and an active metal Ru, wherein the active metal Ru is dispersed on the surface of the carrier in the form of metal nanoparticles, and the loading amount is 0.5-5wt.%.

2. A supported ruthenium-based catalyst as claimed in claim 1, characterized in that: The carrier is one or more of silicon dioxide, titanium dioxide, carbon, aluminum oxide or a mesoporous molecular sieve.

3. A method for preparing a supported ruthenium-based catalyst as claimed in claim 1, characterized in that: The carrier is added to the ruthenium metal precursor solution, mixed evenly, and the solvent is evaporated under negative pressure, and the mixture is placed in a 55-65°C oven to be completely dried to obtain a precursor of a supported ruthenium catalyst; the precursor is ground and placed in a tubular furnace in an inert atmosphere for annealing for 1-3 hours, taken out, ground, and reduced in a 5% H2 / Ar atmosphere for 1-3 hours to finally obtain a supported ruthenium-based catalyst.

4. The method for preparing a supported ruthenium-based catalyst according to claim 3, characterized in that: The ruthenium metal precursor is one or more of ruthenium trichloride, ruthenium acetylacetonate or triruthenium dodecacarbonyl.

5. The method for preparing a supported ruthenium-based catalyst as claimed in claim 3, characterized in that: The annealing temperature in the tube furnace under inert atmosphere is 150-250°C, and the heating rate is 5°C / min.

6. The method for preparing a supported ruthenium-based catalyst as claimed in claim 3, characterized in that: The reduction temperature was 500-550 °C in 5% H2 / Ar atmosphere, and the heating rate was 2 °C / min.

7. Use of the supported ruthenium-based catalyst as claimed in claim 1 in the dehydrogenation of 3-methylpiperidine to prepare 3-methylpyridine.

8. Use of the supported ruthenium-based catalyst as claimed in claim 7 in the dehydrogenation of 3-methylpiperidine to prepare 3-methylpyridine, characterized in that: Under the action of a supported ruthenium catalyst, 3-methylpiperidine is introduced into a fixed bed reactor at a rate of 0.5 to 3 h⁻¹ under an inert atmosphere, and a dehydrogenation reaction is carried out at 230-320°C to obtain 3-methylpyridine.

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