Composite catalyst, preparation method thereof and application of composite catalyst in synthesis of 2-methylpyridine

Abstract

The invention discloses a composite catalyst as well as a preparation method and application thereof in synthesis of 2-methylpyridine, and belongs to the technical field of chemical synthesis. The composite catalyst is prepared by adopting an ultrasonic-coprecipitation method: dissolving nickel salt into a 0.01-1mol / L solution, slowly adding a precipitant solution for precipitation, and then performing aging, ultrasonic treatment, filtration, washing and drying, calcination and hydrogen reduction. When the catalyst is applied to synthesis of 2-methylpyridine, pyridine is taken as a main raw material, methanol is taken as an auxiliary raw material, a reaction is carried out in a fixed bed under the conditions that the temperature is 170-300 DEG C, the pressure is 0.7-1.8 MPa and the air speed is 0.5-3h <-1 >, and a high-purity product is obtained after a crude product is rectified. The catalyst is uniform in active component distribution, recyclable and mild in reaction condition, the yield of the 2-methylpyridine product reaches 51%, the purity exceeds 99%, the cost is reduced, and industrial chain extension is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and in particular to a composite catalyst, a preparation method thereof and application thereof in the synthesis of 2-methylpyridine. Background Art

[0002] 2-Methylpyridine is an important chemical intermediate and fine chemical raw material, widely used in the production of pharmaceutical products such as long-acting sulfonamides and the anti-allergic drug chlorpheniramine. It is also a key raw material for pesticide intermediates, feed and feed intermediates. It can also be used to synthesize the herbicides paraquat and chlorquat, as well as the intermediates of special resins polyvinylpyridine and 2-vinylpyridine.

[0003] Industry data indicates that domestic demand for 2-methylpyridine is growing at an annual rate of approximately 25%, suggesting significant market potential. However, existing technologies for synthesizing 2-methylpyridine face challenges, including complex catalyst preparation, uneven distribution of active components, low catalytic efficiency, and difficulty in recycling. These challenges also include demanding reaction conditions (such as high temperature and high pressure), lengthy process flows, low product selectivity, and high production costs, limiting their industrial application and expansion into the industrial chain. Summary of the Invention

[0004] The present invention aims to provide a composite catalyst, a preparation method thereof and application in the synthesis of 2-picoline, so as to solve the problems of poor catalyst performance, harsh reaction conditions, high cost and long process flow in the existing 2-picoline synthesis technology, reduce costs and improve the product yield and purity of 2-picoline.

[0005] To achieve the above object, the present invention provides a method for preparing a composite catalyst, which is prepared by ultrasound-coprecipitation method and specifically comprises the following steps:

[0006] (1) dissolving nickel salt in water to prepare a nickel salt solution of a certain concentration;

[0007] (2) adding a precipitant solution under a certain temperature and stirring ultrasonic conditions to precipitate nickel ions;

[0008] (3) The composite catalyst is prepared by aging, ultrasonication, filtration, washing and drying, calcination and hydrogen reduction.

[0009] Preferably, the nickel salt is one of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate; the concentration of the nickel salt solution is 0.01-1 mol / L; and the precipitant is one of carbonate, sodium hydroxide, sodium sulfide, sodium phosphate, and ammonia water.

[0010] Preferably, the molar concentrations of the nickel salt solution and the precipitant solution are the same.

[0011] Preferably, the temperature is 30-90° C., the stirring rate is 200-600 r / min, and the ultrasonic conditions are 50-200 w, 30-50 khz.

[0012] The present invention also provides a composite catalyst prepared by the above preparation method.

[0013] The present invention also provides application of the composite catalyst in the synthesis of 2-methylpyridine.

[0014] Preferably, the synthesis steps of 2-methylpyridine are: under certain mild and pressure conditions, pyridine is used as the main raw material, methanol is added, the reaction is carried out at a certain space velocity in a fixed bed to obtain a crude product, and high-purity 2-methylpyridine is prepared by distillation.

[0015] Preferably, the reaction temperature is 170-300°C, the reaction pressure is 0.7-1.8 MPa, and the air velocity is 0.5-3 h -1 .

[0016] Preferably, the mass ratio of methanol to pyridine is 1-20:99-80.

[0017] The present invention uses an ultrasound-coprecipitation method to prepare the catalyst. Its core is to first fully react nickel ions with a precipitant through coprecipitation to produce a uniform nickel-based precipitate. Ultrasonic treatment, using the vibration of ultrasound, further promotes the uniformity of the precipitate's dispersion, reduces agglomeration, and ensures a more uniform distribution of the active component (nickel) within the catalyst. Subsequent aging, filtration, washing, drying, and calcination steps remove impurities, stabilize the catalyst structure, and form nickel oxides. A final reduction step converts the oxides into a highly catalytically active metallic nickel element, which serves as the active center, resulting in a highly efficient composite catalyst.

[0018] Using pyridine as the main raw material and methanol as the auxiliary raw material (methyl donor), a methylation reaction occurs in a fixed bed under the action of the above-mentioned composite catalyst (with nickel as the active center): methanol provides the methyl group, which is catalyzed by the active sites on the catalyst surface and is selectively introduced into the 2-position (ortho-position) of the pyridine ring, generating 2-methylpyridine. The synthesis mechanism reaction formula is as follows:

[0019]

[0020] By optimizing reaction conditions and regulating the ratio of methanol to pyridine, the directional methylation reaction is promoted, improving product selectivity. Finally, through distillation separation and purification, high-purity (over 99%) 2-methylpyridine is obtained. Specifically, the present invention optimizes the catalyst preparation process (ultrasound-coprecipitation+reduction) to ensure efficient dispersion of the active components, and then utilizes this catalyst to promote the directional methylation reaction of pyridine and methanol, achieving efficient synthesis of 2-methylpyridine.

[0021] Therefore, the present invention provides a composite catalyst and a preparation method thereof and application in the synthesis of 2-picoline, which have the following beneficial effects:

[0022] (1) The present invention adopts the ultrasound-coprecipitation method to prepare the composite catalyst, which can accurately control the catalyst composition, make the active components evenly distributed, and significantly improve the catalytic efficiency; at the same time, the catalyst can be recycled and reused, reducing the cost of catalyst replacement; nickel salt and precipitant are both common chemical raw materials with a wide range of sources, further reducing the cost of catalyst preparation.

[0023] (2) The reaction temperature for synthesizing 2-methylpyridine in the present invention is 170-300°C and the pressure is 0.7-1.8 MPa, which belongs to medium temperature and medium pressure conditions. The reaction conditions are mild and easier to achieve than the harsh reaction conditions that may exist in the prior art. At the same time, the fixed bed reaction process is simple and the process flow is short, which is convenient for capacity expansion and transformation of existing equipment and has high industrial feasibility.

[0024] (3) The present invention optimizes the reaction temperature, pressure, space velocity and the ratio of methanol to pyridine, so that the product selectivity is high. After distillation, the purity of 2-methylpyridine can reach more than 99%, and the yield can reach up to 51%, thereby improving product quality and raw material utilization.

[0025] (4) The present invention uses pyridine as the main raw material and methanol as the auxiliary raw material, which is consistent with the raw material advantages of pyridine production enterprises, can directly extend the existing industrial chain, and reduce the cost of raw material transportation and processing.

[0026] The technical solution of the present invention is further described in detail below through examples. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a composite catalyst, which adopts an ultrasound-coprecipitation method and specifically comprises the following steps:

[0028] (1) dissolving nickel salt in water to prepare a nickel salt solution of a certain concentration;

[0029] (2) slowly adding a precipitant solution under stirring and ultrasonic conditions at a certain temperature to precipitate nickel ions;

[0030] (3) The composite catalyst is prepared by aging, ultrasonication, filtration, washing and drying, calcination and reduction.

[0031] In the present invention, the nickel salt is preferably one of nickel chloride, nickel sulfate, nickel nitrate, and nickel acetate, more preferably one of nickel chloride, nickel sulfate, and nickel nitrate; the concentration of the nickel salt solution is preferably 0.01-1 mol / L, more preferably 0.05-0.8 mol / L, and even more preferably 0.1-0.5 mol / L. The precipitant is one of carbonate, sodium hydroxide, sodium sulfide, sodium phosphate, and ammonia water, more preferably one of sodium hydroxide and sodium sulfide. In the present invention, the molar concentration of the nickel salt solution and the precipitant solution are the same, and the precipitant solution is slowly added dropwise to the nickel salt solution to avoid local supersaturation.

[0032] In the present invention, the temperature is 30-90° C., the stirring rate is 200-600 r / min, and the ultrasonic conditions are 50-200 w, 30-50 khz.

[0033] The present invention also provides a composite catalyst prepared by the above preparation method.

[0034] The present invention also provides application of the composite catalyst in the synthesis of 2-methylpyridine.

[0035] In the present invention, the synthesis steps of 2-methylpyridine are as follows: under certain mild and pressure conditions, pyridine is used as the main raw material, methanol is added, a reaction is carried out at a certain space velocity in a fixed bed to obtain a crude product, and high-purity 2-methylpyridine is prepared by distillation.

[0036] In the present invention, the reaction temperature is preferably 170-300°C, more preferably 200-280°C, and further preferably 210-260°C; the reaction pressure is preferably 0.7-1.8 MPa, more preferably 0.8-1.6 MPa, and further preferably 0.9-1.3 MPa; the space velocity is preferably 0.5-3 h -1 , more preferably 0.7-2.5h -1 , and further preferably 1.0-2.0h -1 .

[0037] In the present invention, the mass ratio of methanol to pyridine is preferably 1-20:99-80, more preferably 10:90 or 15:85.

[0038] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, simplifications made without violating the spirit and principles of the present invention should all be equivalent replacement modes and are included within the scope of protection of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims appended to this application and all belong to the scope of protection of the present invention.

[0039] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0040] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0041] Unless otherwise specified in the present invention, the reagents, instruments, and equipment used are those commonly used by those skilled in the art.

[0042] Example 1

[0043] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0044] (1) Nickel chloride was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0045] (2) Add sodium hydroxide of the same molar concentration at 30°C and 200 r / min with ultrasound at 50w / 30khz to precipitate nickel ions.

[0046] (3) Composite catalysts 1-1#, 1-2#, 1-3#, 1-4#, and 1-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination, and hydrogen reduction.

[0047] Example 2

[0048] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0049] (1) Nickel chloride was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0050] (2) Add sodium sulfide of the same molar concentration at 90°C and 600 r / min with ultrasound at 200w / 50khz to precipitate nickel ions.

[0051] (3) Composite catalysts 2-1#, 2-2#, 2-3#, 2-4# and 2-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination and reduction.

[0052] Example 3

[0053] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0054] (1) Nickel sulfate was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0055] (2) Add sodium hydroxide of the same molar concentration at 50°C and 400 r / min with ultrasound at 100w / 40khz to precipitate nickel ions.

[0056] (3) Composite catalysts 3-1#, 3-2#, 3-3#, 3-4# and 3-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination and hydrogen reduction.

[0057] Example 4

[0058] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0059] (1) Nickel sulfate was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0060] (2) Add sodium sulfide of the same molar concentration at 70°C and 500 r / min with ultrasound at 80w / 40khz to precipitate nickel ions.

[0061] (3) Composite catalysts 4-1#, 4-2#, 4-3#, 4-4# and 4-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination and reduction.

[0062] Example 5

[0063] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0064] (1) Nickel nitrate was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0065] (2) Add sodium hydroxide of the same molar concentration at 60°C and 400 r / min with ultrasound at 80w / 40khz to precipitate nickel ions.

[0066] (3) Composite catalysts 5-1#, 5-2#, 5-3#, 5-4# and 5-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination and reduction.

[0067] Example 6

[0068] This embodiment provides a method for preparing a composite catalyst, comprising the following steps:

[0069] (1) Nickel nitrate was dissolved in water to prepare nickel salt solutions with concentrations of 0.01 mol / L, 1 mol / L, 0.7 mol / L, and 0.4 mol / L.

[0070] (2) Add sodium sulfide of the same molar concentration at 60°C and 400 r / min with ultrasound at 80w / 40khz to precipitate nickel ions.

[0071] (3) Composite catalysts 6-1#, 6-2#, 6-3#, 6-4# and 6-5# were prepared respectively through aging, ultrasonication, filtration, washing and drying, calcination and reduction.

[0072] The composite catalyst prepared in the above example was applied to the synthesis of 2-methylpyridine.

[0073] Example 7

[0074] This embodiment provides a synthesis of 2-methylpyridine. The synthesis steps are as follows: 30 g of the composite catalyst 4-2# prepared in Example 4 is added to a fixed bed, and the reaction temperature is 170° C. and the space velocity is 0.5 h -1 Under a reaction pressure of 0.7 MPa, methanol and pyridine were added in a mass ratio of 1:99 to react. After the reaction was completed, 2-methylpyridine was obtained by distillation. The yield was measured to be 18% and the purity reached 99.1%.

[0075] Example 8

[0076] This embodiment provides a synthesis of 2-methylpyridine. The synthesis steps are as follows: 30 g of the composite catalyst 4-2# prepared in Example 4 is added to a fixed bed, and the reaction temperature is 380° C. and the space velocity is 3 h -1 Under a reaction pressure of 1.8 MPa, methanol and pyridine were added in a mass ratio of 20:80 to react. After the reaction was completed, 2-methylpyridine was obtained by distillation. The yield was measured to be 31% and the purity reached 99.2%.

[0077] Example 9

[0078] This embodiment provides a synthesis of 2-methylpyridine. The synthesis steps are as follows: 30 g of the composite catalyst 4-2# prepared in Example 4 is added to a fixed bed, and the reaction temperature is 270° C. and the space velocity is 2.3 h -1Under a reaction pressure of 1.4 MPa, methanol and pyridine were added in a mass ratio of 10:90 to react. After the reaction was completed, 2-methylpyridine was obtained by distillation. The yield was measured to be 42% and the purity reached 99.4%.

[0079] Example 10

[0080] This embodiment provides a synthesis of 2-methylpyridine. The synthesis steps are as follows: 30 g of the composite catalyst 4-2# prepared in Example 4 is added to a fixed bed, and the reaction temperature is 240° C. and the space velocity is 1.5 h -1 Under a reaction pressure of 1.2 MPa, methanol and pyridine were added in a mass ratio of 15:85 to react. After the reaction was completed, 2-methylpyridine was obtained by distillation. The yield was measured to be 51% and the purity reached 99.5%.

[0081] In summary, the present invention adopts an ultrasound-coprecipitation method to prepare a composite catalyst and applies it to the synthesis of 2-methylpyridine. The active components of the catalyst prepared by this technical solution are evenly distributed and recyclable, and the reaction conditions are mild. The product yield of 2-methylpyridine is as high as 51% and the purity exceeds 99%, which reduces costs and is conducive to the extension of the industrial chain of pyridine production enterprises.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite catalyst, characterized in that: The preparation is carried out by ultrasound-coprecipitation method, which specifically includes the following steps: (1) dissolving nickel salt in water to prepare a nickel salt solution of a certain concentration; (2) adding a precipitant solution under a certain temperature and stirring ultrasonic conditions to precipitate nickel ions; (3) The composite catalyst is prepared by aging, ultrasonication, filtration, washing and drying, calcination and hydrogen reduction.

2. The method for preparing a composite catalyst according to claim 1, wherein: The nickel salt is one of nickel chloride, nickel sulfate, nickel nitrate and nickel acetate, and the concentration of the nickel salt solution is 0.01-1 mol / L; the precipitant is one of carbonate, sodium hydroxide, sodium sulfide, sodium phosphate and ammonia water.

3. The method for preparing a composite catalyst according to claim 1, wherein: The molar concentrations of the nickel salt solution and the precipitant solution are the same.

4. The method for preparing a composite catalyst according to claim 1, wherein: The temperature is 30-90°C, the stirring rate is 200-600r / min, and the ultrasonic conditions are 50-200w, 30-50khz.

5. A composite catalyst, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1 to 4.

6. The use of a composite catalyst as claimed in claim 5, characterized in that: The composite catalyst is applied to the synthesis of 2-methylpyridine.

7. The use of a composite catalyst according to claim 6, characterized in that: The synthesis steps of 2-methylpyridine are as follows: under certain mild and pressure conditions, pyridine is used as the main raw material, methanol is added, and a reaction is carried out at a certain space velocity in a fixed bed to obtain a crude product, and high-purity 2-methylpyridine is prepared by distillation.

8. The use of a composite catalyst according to claim 7, characterized in that: The reaction temperature is 170-300℃, the reaction pressure is 0.7-1.8Mpa, and the space velocity is 0.5-3h -1 .

9. The use of a composite catalyst according to claim 7, characterized in that: The mass ratio of methanol to pyridine is 1-20:99-80.

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