Catalyst for hydrodechlorination synthesis of 2, 3-dichloropyridine and preparation method thereof, and synthesis method of 2, 3-dichloropyridine

Abstract

The invention relates to the technical field of catalysts, in particular to a catalyst for hydrodechlorination synthesis of 2, 3-dichloropyridine, a preparation method of the catalyst and a synthesis method of the 2, 3-dichloropyridine. The catalyst comprises a carrier, an active component loaded on the carrier and a coating layer located outside the carrier, the active component is Pd; and the coating layer is made of a nitrogen-doped carbon material. According to the present invention, the nitrogen-doped carbon material (CN) is adopted to coat the Al2O3-loaded Pd catalyst (PdM / Al2O3, and M is adopted as the auxiliary agent), the acid-base property of the catalyst surface is adjusted, and the electronic structure of Pd can be changed through the interaction of CN and Pd so as to improve the catalytic performance of the catalyst; meanwhile, CN can inhibit poisoning, loss and aggregation of the Pd active component, so that the stability and recycling performance of the catalyst are improved. In addition, due to the addition of the auxiliary agent, the dispersity of Pd is improved, and the activity of the catalyst is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of catalysts, and in particular to a catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination and a preparation method thereof, and a method for synthesizing 2,3-dichloropyridine. Background Art

[0002] 2,3-Dichloropyridine is an important chemical raw material, widely used in the fields of pesticides, dyes and rubber. For example, 2,3-Dichloropyridine can be used to synthesize the pesticides chlorantraniliprole, cyproconazole, cyantraniliprole, etc. Among them, chlorantraniliprole has a unique effect on lepidopteran pests, is less toxic to mammals, and has the advantages of less pollution to the environment, so it is widely used in pest control.

[0003] At present, there are mainly the following methods for synthesizing 2,3-dichloropyridine: (1) 2-chloropyridine synthesis method. The product separation of this method is difficult and the yield is low; (2) 3-chloropyridine synthesis method. The raw material 3-chloropyridine used in this method is expensive and difficult to industrialize; (3) 2-chloro-3-nitropyridine synthesis method. The raw materials used in this method are expensive; (4) 3-aminopyridine synthesis method. This method requires multiple steps of chlorination, diazotization, chlorination, etc., and a large amount of waste liquid will be generated during the production process, causing serious environmental pollution; (5) 2,3,6-trichloropyridine synthesis method. This method is simple to industrialize, has a high product yield, and has little environmental pollution. It has become the most promising method for synthesizing 2,3-dichloropyridine.

[0004] The related art discloses the use of Pd-Mg / C catalyst for the hydrodechlorination of 2,3,6-trichloropyridine to synthesize 2,3-dichloropyridine. The catalyst has high precious metal dispersion, and the auxiliary agent Mg adjusts the surface acidity and alkalinity of the catalyst, thereby improving the selectivity of 2,3-dichloropyridine and enhancing the interaction between the precious metal and the carrier, thereby improving the stability. However, the catalyst has a high precious metal content and serious loss. In addition, the related art also discloses the use of Pd / C catalyst for the synthesis of 2,3-dichloropyridine. However, the process is prone to over-dechlorination, and the reaction selectivity and product yield are not high.

[0005] As can be seen from the above, the current process of 2,3,6-trichloropyridine hydrodechlorination to synthesize 2,3-dichloropyridine has low catalytic performance, easy deactivation, poor reusability, poor product selectivity and low yield. Summary of the invention

[0006] The present application provides a catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination and a preparation method thereof, and a method for synthesizing 2,3-dichloropyridine.

[0007] Aiming at the problems of low catalytic performance, easy deactivation, poor reusability, poor product selectivity and low yield in the process of hydrodechlorination of 2,3,6-trichloropyridine to 2,3-dichloropyridine, this application proposes to use nitrogen-doped carbon material (CN) coated Al 2 O 3 Supported Pd catalyst (PdM / Al 2 O 3 , M is an auxiliary agent), the acidity and alkalinity of the catalyst surface can be adjusted, and the electronic structure of Pd can be changed through the interaction between CN and Pd, thereby improving the catalytic performance of the catalyst. At the same time, CN can inhibit the poisoning, loss and aggregation of the Pd active component, thereby improving the stability and recycling performance of the catalyst. In addition, the addition of auxiliary agents improves the dispersibility of Pd, thereby improving the activity of the catalyst. The catalyst provided by the present application can effectively improve product selectivity and yield.

[0008] In the first aspect, the present application provides a catalyst for hydrodechlorination synthesis of 2,3-dichloropyridine, using the following technical solution:

[0009] A catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination, the catalyst comprising a carrier, an active component loaded on the carrier, and a coating layer located outside the carrier;

[0010] The active component is Pd; and the coating layer is a nitrogen-doped carbon material.

[0011] Optionally, the carrier is Al 2 O 3 .

[0012] Optionally, the loading amount of the active component is 0.005-1 wt.% of the carrier.

[0013] Optionally, the loading amount of the active component is 0.01-0.1 wt.% of the carrier.

[0014] In a specific embodiment, the loading amount of the active component is 0.005wt.%, 0.01wt.%, 0.05wt.%, 0.1wt.%, or 1wt.% of the carrier.

[0015] In some specific embodiments, the loading amount of the active ingredient is 0.005-0.01wt.%, 0.005-0.05wt.%, 0.005-0.1wt.%, 0.01-0.05wt.%, 0.01-0.1wt.%, 0.01-1wt.%, 0.05-0.1wt.%, 0.05-1wt.%, 0.1-1wt.% of the carrier.

[0016] Optionally, the weight of the coating layer is 0.05-2 wt.% of the weight of the carrier.

[0017] In a specific embodiment, the weight of the coating layer is 0.05wt.%, 0.5wt.%, 1wt.%, or 2wt.% of the weight of the carrier.

[0018] In some specific embodiments, the weight of the coating layer is 0.05-0.5wt.%, 0.05-1wt.%, 0.5-1wt.%, 0.5-2wt.%, 1-2wt.% of the weight of the carrier.

[0019] Optionally, the catalyst further comprises an auxiliary agent supported on the carrier; optionally, the auxiliary agent is one or more of Ni, Co, Sn and Zn;

[0020] Optionally, the catalyst further comprises an auxiliary agent supported on the carrier; optionally, the loading amount of the auxiliary agent is 0-0.5wt.% of the carrier.

[0021] Optionally, the catalyst further comprises an auxiliary agent supported on the carrier; optionally, the loading amount of the auxiliary agent is 0-0.05wt.% of the carrier.

[0022] In a specific embodiment, the catalyst further comprises an auxiliary agent supported on the carrier; optionally, the loading amount of the auxiliary agent is 0, 0.01wt.%, 0.05wt.%, or 0.5wt.% of the carrier.

[0023] In some specific embodiments, the catalyst further includes an auxiliary agent loaded on the carrier; optionally, the loading amount of the auxiliary agent is 0-0.01wt.%, 0.01-0.05wt.%, 0.01-0.5wt.%, 0.05-0.5wt.% of the carrier.

[0024] In a second aspect, the present application provides a method for preparing the above-mentioned catalyst, using the following technical solution:

[0025] A method for preparing a catalyst, the method specifically comprising the following steps: preparing a coating layer on the surface of a carrier loaded with an active component or a carrier loaded with an active component and an auxiliary agent, to obtain the catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination;

[0026] The preparation method of the coating layer is as follows: adding the prepared carrier loaded with active components or the carrier loaded with active components and auxiliary agents into m-xylene, adding ethylenediamine and carbon tetrachloride according to the amount of each component, stirring at 50-90°C for 3-5h; then stirring at 120-160°C for 3-5h; drying the generated solid compound at 100-150°C for 10-15h, grinding and screening the solid compound of 50-100 μm, and sequentially placing it in a nitrogen atmosphere at 400-650°C for calcination for 2-6h, and reducing it in a hydrogen atmosphere at 200-450°C for 2-6h, so as to obtain the catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination.

[0027] Optionally, the preparation method of the carrier loaded with active components or the carrier loaded with active components and auxiliary agents is as follows: prepare the carrier loaded with active components or the carrier loaded with active components and auxiliary agents: dissolve Pd salt or Pd salt and auxiliary agent salt in water at a temperature of 30-80°C according to the amount of each component to obtain a solution, then immerse the carrier in the solution, adsorb for 2-24 hours, and then filter the solvent, and successively place the solid at 100-150°C for drying for 6-16 hours and calcine in an air environment at 350-550°C for 2-6 hours to obtain the carrier loaded with active components or the carrier loaded with active components and auxiliary agents.

[0028] In a third aspect, the present application provides a method for synthesizing 2,3-dichloropyridine, which uses the above-mentioned catalyst.

[0029] Optionally, the synthesis method specifically includes the following steps: mixing 2,3,6-trichloropyridine, a polar organic solvent, an acidifying agent and the catalyst in proportion, and performing a hydrogenation reaction in a hydrogen atmosphere to obtain the 2,3-dichloropyridine.

[0030] Optionally, the acid dressing agent includes any one or more of ammonia methanol, triethylamine, sodium hydroxide, and sodium carbonate.

[0031] In summary, the present application includes at least one of the following beneficial technical effects:

[0032] This application proposes to use nitrogen-doped carbon material (CN) to coat Al 2 O 3 Supported Pd catalyst (PdM / Al 2 O 3 , M is an auxiliary agent), which can adjust the acidity and alkalinity of the catalyst surface. Through the interaction between CN and Pd, the electronic structure of Pd can be changed, thereby improving the catalytic performance of the catalyst.

[0033] At the same time, CN can inhibit the poisoning, loss and aggregation of Pd active components, thereby improving the stability and recycling performance of the catalyst.

[0034] In addition, the addition of additives improves the dispersion of Pd and thus improves the activity of the catalyst.

[0035] The use of the catalyst provided in this application can effectively improve product selectivity and yield. DETAILED DESCRIPTION

[0036] Before describing the embodiments of the present application in detail, it should be understood that the terms used herein are only used for the purpose of describing specific embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by ordinary technicians in the field to which the terms belong.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0038] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0040] The present application provides a catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination. The catalyst comprises a carrier, an active component loaded on the carrier, and a coating layer located outside the carrier. The active component is Pd, the coating layer is a nitrogen-doped carbon material, and the carrier is Al 2 O 3 .

[0041] The active component loading is 0.005-1wt.% of the carrier. The coating weight is 0.05-2wt.% of the carrier. The catalyst also includes an auxiliary agent loaded on the carrier; optionally, the auxiliary agent is one or more of Ni, Co, Sn and Zn. The auxiliary agent loading is 0-0.5wt.% of the carrier.

[0042] The present application provides a method for preparing the above catalyst, which specifically comprises the following steps: preparing a coating layer on the surface of a carrier carrying an active component or a carrier carrying an active component and an auxiliary agent to obtain the catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination.

[0043] In a specific embodiment, a method for preparing a catalyst for hydrodechlorination synthesis of 2,3-dichloropyridine specifically comprises the following steps:

[0044] (1) Preparation of active component-loaded carrier (Pd / Al 2 O 3 ) or a carrier for loading active components and additives (PdM / Al 2 O 3 )

[0045] In a water bath at 30-80°C, Pd salt or Pd salt and auxiliary salt are dissolved in water according to the amount of each component to obtain a solution, and then the carrier is immersed in the solution. After adsorption for 2-24 hours, the solvent is filtered, and the solid is first placed in an oven at 100-150°C for 6-16 hours, and then the solid is placed in an air environment at 350-550°C for calcination for 2-6 hours to obtain a carrier loaded with active components or a carrier loaded with active components and auxiliary agents.

[0046] (2) Preparation of coating layer

[0047] The prepared carrier loaded with active components or the carrier loaded with active components and auxiliary agents is added to meta-xylene, and ethylenediamine and carbon tetrachloride are added according to the amount of each component, and stirred at 50-90° C. for 3-5 hours; then stirred at 120-160° C. for 3-5 hours; the generated solid compound is dried at 100-150° C. for 10-15 hours, and the solid compound of 50-100 μm is ground and screened, and is successively placed in a nitrogen atmosphere at 400-650° C. for calcination for 2-6 hours, and reduced in a hydrogen atmosphere at 200-450° C. for 2-6 hours, to obtain the catalyst for hydrodechlorination synthesis of 2,3-dichloropyridine.

[0048] In addition, the present application also provides a method for synthesizing 2,3-dichloropyridine, wherein the above-mentioned catalyst is used in the method.

[0049] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The embodiments described below are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0050] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0051] The present application is further described in detail below in conjunction with the embodiments and test results.

[0052] Example

[0053] Example 1

[0054] This embodiment provides a catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination.

[0055] The preparation method of the above catalyst specifically comprises the following steps:

[0056] (1) Preparation of PdM / Al 2 O 3

[0057] In a water bath at 30°C, 0.022 g of palladium nitrate and 0.05 g of nickel nitrate hexahydrate were dissolved in 50 g of MgSO4 to obtain a solution, and 100 g of Al 2 O 3 Immerse in the solution, filter the solvent after 1 hour. First, place the solid in an oven at 120°C for 6 hours, and then calcine the solid in an air environment at 350°C for 2 hours to obtain 0.01wt.%Pd-0.01wt.%Ni / Al 2 O 3 .

[0058] (2) Preparation of coating layer

[0059] 5g of the above solid was added to 80g of m-xylene, and then 2g of ethylenediamine and 4g of carbon tetrachloride were added, heated to 90°C and stirred for 4h; then heated to 140°C and stirred for 4h. The resulting solid compound was dried at 120°C for 12h, ground and screened for 50-100μm solid compounds, and then placed in a nitrogen atmosphere at 500°C for calcination for 2h and reduced in a hydrogen atmosphere at 300°C for 2h to obtain CN-coated PdNi / Al 2 O 3 catalyst.

[0060] Example 2-11

[0061] Examples 2-11 each provide a catalyst for the synthesis of 2,3-dichloropyridine by hydrodechlorination.

[0062] The difference between the preparation method of the above catalyst and Example 1 is that the type, amount or some preparation parameters of the raw materials used are shown in Table 1. The rest are consistent with the operation steps of Example 1.

[0063] The differences between the above embodiments 1-11 are as follows:

[0064] The difference between Example 1-2 is: the amount of palladium nitrate used and the water bath temperature.

[0065] The difference between Example 2-3 is the amount of nickel nitrate hexahydrate used.

[0066] The difference between Examples 3-5 is: the hydrogen reduction temperature.

[0067] The difference between Example 6 and Example 3 is: the consumption of palladium nitrate.

[0068] The difference between Example 7 and Example 3 is the type of auxiliary agent.

[0069] The difference between Example 8-9 and Example 6 is the amount of meta-xylene, ethylenediamine and carbon tetrachloride used.

[0070] The difference between Example 10 and Example 8 lies in the amounts of ethylenediamine and carbon tetrachloride and the temperature of nitrogen calcination.

[0071] The difference between Example 11 and Example 6 is that the auxiliary agent nickel nitrate hexahydrate is not added.

[0072] Comparative Example

[0073] This comparative example provides a catalyst.

[0074] The difference between the above catalyst and Example 1 is that: PdM / Al is prepared only by step (1) 2 O 3 That is, the catalyst was obtained without performing step (2) of preparing the coating layer, as shown in Table 1. The rest of the steps were consistent with those in Example 1.

[0075] Table 1 Type and amount of each component in the catalyst of each embodiment and comparative example and some preparation parameters

[0076]

[0077]

[0078] Performance testing

[0079] (I) Catalyst performance testing

[0080] The coating layers in the catalysts prepared in the above-mentioned embodiments and comparative examples were respectively detected by a thermogravimetric analyzer. The characteristics of the coating layers were reflected by the relationship between the weight of the coating layers and the weight of the carrier. The detection results are shown in Table 2.

[0081] 2,3-Dichloropyridine was prepared using the catalysts provided in the above examples and comparative examples, respectively, to evaluate the above catalysts.

[0082] The evaluation method is as follows: 50 g of 2,3,6-trichloropyridine, 150 g of methanol, 6 g of 15% ammonia methanol, 20 g of deionized water and 0.02 g of a catalyst are mixed and placed in a high-pressure reactor, the air in the reactor is replaced by nitrogen, and hydrogen is introduced. The reaction is carried out at 37° C. and 1.0 MPa for 2.5 hours to obtain a crude product; the catalyst in the crude product is filtered, and the filtrate is separated by distillation to obtain 2,3-dichloropyridine.

[0083] The calculated results of conversion rate and mass yield are shown in Table 2.

[0084] Table 2 Conversion rate of the catalytic reaction and mass yield of the product provided by the catalysts in the examples and comparisons

[0085]

[0086] As shown in Table 2, the conversion rate of the catalysts prepared in the present application is above 99.0%, and the yield is above 85.0%. The conversion rate of the catalyst in the comparative example is 98.4%, and the yield is only 80.1%. At the same time, as shown in Table 2, the weight of the coating layer in the catalyst prepared in the present application accounts for 0.05-2wt.% of the weight of the carrier.

[0087] At the same time, by comparing the results of Examples 6 and 8-9, it can be seen that too little or too much CN will affect the performance of the catalyst, and the amount of CN obtained in Example 8 can completely cover without affecting the diffusion of the reactants.

[0088] In addition, by comparing the results of Examples 8 and 10, it can be seen that the carbonization temperature significantly affects the catalytic performance of the catalyst, and too high a carbonization temperature reduces the catalyst performance.

[0089] (II) Catalyst reusability test

[0090] The catalysts provided in Example 8 and the comparative example were respectively added back into new raw materials after use to continue the catalytic reaction in order to examine the reusability.

[0091] The conversion rate and mass yield of the reused catalyst are shown in Table 3.

[0092] Table 3 Conversion rate of catalytic reaction and mass yield of product by reusing the catalyst provided in Example 8 and comparison

[0093] Serial number Conversion rate (%) Mass yield (%) Example 8 99.8 94.2 Example 8 - Second use 99.6 94.3 Example 8 - Third Use 99.7 93.8 Example 8 - Fourth use 99.8 93.1 Example 8 - Fifth use 99.5 93.0 Comparative Example 98.4 80.1 Comparative Example - Second Use 90.1 75.3

[0094] As can be seen from Table 3, the catalyst prepared in Example 8 was reused 5 times, and the catalytic performance of the catalyst was slightly reduced, while the catalytic performance of the comparative example was greatly reduced after being used twice, indicating that the CN-coated catalyst provided in the present application can effectively improve the activity and stability of the catalyst.

[0095] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A catalyst for hydrodechlorination synthesis of 2,3-dichloropyridine, characterized in that: The catalyst comprises a carrier, an active component supported on the carrier, and a coating layer located outside the carrier; The active component is Pd; and the coating layer is a nitrogen-doped carbon material.

2. The catalyst according to claim 1, characterized in that The carrier is Al2O3.

3. The catalyst according to claim 1, characterized in that The loading amount of the active component is 0.005-1 wt.% of the carrier.

4. The catalyst according to claim 1, characterized in that The weight of the coating layer is 0.05-2 wt.% of the weight of the carrier.

5. The catalyst according to claim 1, characterized in that The catalyst further includes an auxiliary agent supported on the carrier; optionally, the auxiliary agent is one or more of Ni, Co, Sn and Zn.

6. The catalyst according to claim 1, characterized in that The catalyst further comprises an auxiliary agent loaded on the carrier; optionally, the loading amount of the auxiliary agent is 0-0.5wt.% of the carrier.

7. A method for preparing the catalyst according to any one of claims 1 to 6, characterized in that: The preparation method specifically comprises the following steps: preparing a coating layer on the surface of a carrier loaded with active components or a carrier loaded with active components and an auxiliary agent to obtain the catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination; The preparation method of the coating layer is as follows: adding the prepared carrier loaded with active components or the carrier loaded with active components and auxiliary agents into m-xylene, adding ethylenediamine and carbon tetrachloride according to the amount of each component, stirring at 50-90°C for 3-5h; then stirring at 120-160°C for 3-5h; drying the generated solid compound at 100-150°C for 10-15h, grinding and screening the solid compound of 50-100 μm, and sequentially placing it in a nitrogen atmosphere at 400-650°C for calcination for 2-6h, and reducing it in a hydrogen atmosphere at 200-450°C for 2-6h, so as to obtain the catalyst for synthesizing 2,3-dichloropyridine by hydrodechlorination.

8. The preparation method according to claim 7, characterized in that: The preparation method of the carrier loaded with active components or the carrier loaded with active components and auxiliary agents is as follows: preparing the carrier loaded with active components or the carrier loaded with active components and auxiliary agents: dissolving Pd salt or Pd salt and auxiliary agent salt in water at a temperature of 30-80°C according to the amount of each component to obtain a solution, then immersing the carrier in the solution, adsorbing for 2-24 hours, filtering the solvent, and successively placing the solid at 100-150°C for drying for 6-16 hours and calcining in an air environment of 350-550°C for 2-6 hours to obtain the carrier loaded with active components or the carrier loaded with active components and auxiliary agents.

9. A method for synthesizing 2,3-dichloropyridine, characterized in that: The synthesis method uses the catalyst described in any one of claims 1 to 6.

10. The synthesis method according to claim 9, characterized in that The synthesis method specifically comprises the following steps: 2,3,6-trichloropyridine, a polar organic solvent, an acidifying agent and the catalyst are mixed in proportion, and a hydrogenation reaction is carried out in a hydrogen atmosphere to obtain the 2,3-dichloropyridine.

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