Palladium-carbon catalyst for polychloropyridine hydrodechlorination reaction and preparation method thereof

Abstract

The invention relates to the technical field of noble metal catalyst preparation, and discloses a palladium-carbon catalyst for polychloropyridine hydrodechlorination reaction and a preparation method thereof.The palladium-carbon catalyst is prepared from, by weight, 100 parts of a carrier, 300 parts of nitric acid, 4-60 parts of amine, 14 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5 wt%, and the weight percentage of the amine is 5 wt%. According to the palladium-carbon catalyst for the polychloropyridine hydrodechlorination reaction, the defects that in the hydrodechlorination reaction, 2, 3, 6-trichloropyridine is prepared by taking 2, 3, 6-trichloropyridine as a raw material, the selectivity is not high, the catalytic activity is not strong, and the catalyst is inactive and difficult to apply mechanically are overcome, and the palladium-carbon catalyst for the polychloropyridine hydrodechlorination reaction can be used for preparing the 2, 3-dichloropyridine by taking the 2, 3, 6-trichloropyridine as a raw material. Through the preparation of the palladium-carbon catalyst for the polychloropyridine hydrodechlorination reaction, reaction byproducts are greatly reduced, the emission of pollutants in a solution is reduced, and the economic benefit is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal catalyst preparation, and in particular to a palladium-carbon catalyst for polychlorinated pyridine hydrodechlorination reaction and a preparation method thereof. Background Art

[0002] Polychloropyridine is an important pharmaceutical and pesticide intermediate. It is widely used in the fields of pesticides, anti-tumor and daily chemical products. For example, 2,3,5-trichloropyridine is a key intermediate in the production of herbicides and synthetic pesticides, 3,5-dichloropyridine can be used to produce anti-inflammatory analgesics and antibiotics, and 2,3-dichloropyridine is also a key intermediate in the synthesis of pesticides. There are many methods for the synthesis of polychloropyridines. Among them, the catalytic hydrogenation method has the advantages of cheap raw material price, simple process and clean production. It is a synthetic route with great application prospects. This method was first reported in patent JP1193246. Pd / C was used as a catalyst and 2,3,6-trichloropyridine was used as a raw material to prepare 2,3-dichloropyridine. The product selectivity was 88% and the raw material conversion rate was 33%. As the country advocates the development of green chemistry, many workers have continuously explored the process and catalyst development in the hydrodechlorination reaction of polychlorinated pyridines and achieved good results. For example, in patent CN108380208A, nanometals were highly dispersed on the carrier activated carbon through process adjustment, and the acid-base state of the catalyst surface was adjusted by the auxiliary agent Mg to prepare Pd-Mg / C catalyst. In the reaction of catalyzing the hydrogenation of 2,3,6-trichloropyridine to prepare 2,3-dichloropyridine, the selectivity of the product was improved to a certain extent. Patent CN110961110A prepared composite metals by impregnation method and loaded on carriers such as activated carbon or MgO. Good results were achieved in the reaction of preparing 2,3-dichloropyridine by hydrodechlorination of polychlorinated pyridines.

[0003] However, during the hydrogenation of polychlorinated pyridines, palladium is easily coordinated with pyridine containing nitrogen ligands, making the catalyst deactivated and difficult to apply. During the catalytic process, 2,3-dichloropyridine is easily further dechlorinated, resulting in an increase in side reaction products.

[0004] To this end, we propose a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines and a preparation method thereof. Summary of the invention

[0005] The present invention mainly solves the technical problems existing in the above-mentioned prior art and provides a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a palladium carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, comprising the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 4-60 parts of an amine, 14 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, wherein the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, and the weight percentage of the ethanol aqueous solution is 90wt%.

[0007] Preferably, the material of the carrier is activated carbon.

[0008] Preferably, the activated carbon is made of coconut shell charcoal.

[0009] Preferably, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g.

[0010] Preferably, the particle size of the coconut shell charcoal is 200-300 meshes.

[0011] Preferably, the material of the amine is triethylenediamine, tert-butylamine or trimethylamine.

[0012] Preferably, the palladium content in the sodium chloropalladate is 36%.

[0013] A method for preparing a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, comprising the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps:

[0014] Step 1: Preparation of nitric acid-modified activated carbon: reflux the activated carbon with nitric acid at 80-90°C for 1 hour, wash the activated carbon to neutrality, and obtain nitric acid-modified activated carbon;

[0015] Step 2: Slurry preparation and ultrasonic treatment: nitric acid-modified activated carbon was added to amine and sodium chloropalladate and mixed to prepare slurry, and ultrasonicated at room temperature for 1 h;

[0016] Step 3: Drying: The slurry after ultrasonic treatment was heated to 85°C for slow drying, stirred for 1 hour and kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst;

[0017] Step 4: Soaking, stirring, filtering and washing: Mix hydrochloric acid and ethanol aqueous solution together to obtain a mixed solution, soak the dried catalyst in the mixed solution and stir for 1 hour, filter and wash to obtain the palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0018] Beneficial Effects

[0019] The present invention provides a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction and a preparation method thereof. It has the following beneficial effects:

[0020] 1. A palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines and a preparation method thereof. The present invention provides a palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines, which solves the shortcomings of low selectivity, weak catalytic activity and difficulty in applying the catalyst deactivation in the preparation of 2,3,6-trichloropyridine as a raw material for preparing 2,3-dichloropyridine in the hydrodechlorination reaction. Through the preparation of the palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines, the reaction by-products are greatly reduced, the emission of pollutants in the solution is reduced, and the economic benefits are further improved.

[0021] 2. A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines and a preparation method thereof are characterized in that amine and palladium are coordinated and loaded on activated carbon. After heating, the amine and palladium are partially reduced. The presence of the amine causes a certain steric hindrance on the surface, thereby improving the selectivity of the hydrodechlorination. The heating aging process improves the interaction strength between the palladium and the carrier. The addition of amine content is beneficial to controlling the ratio of Pd0 / Pd2+ in the catalyst and the amount of steric hindrance on the surface of the carrier, thereby changing the activity of the catalyst by adjusting the ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0023] Example 1: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 5 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, and the particle size of the coconut shell charcoal is 200 -300 mesh, the material of the amine is triethylenediamine, the palladium content in sodium chloropalladate is 36%, a method for preparing a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction, including the above-mentioned palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction, specifically comprising the following steps: the first step: preparing nitric acid-modified activated carbon: heating the activated carbon with nitric acid under reflux at a temperature of 80-90°C for 1h, washing the activated carbon into neutral, and obtaining nitric acid-modified activated carbon; the second step: making a slurry and ultrasonically treating The invention discloses a palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines. The invention discloses a palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines. The palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines is provided ...

[0024] Example 2: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 15 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, and the particle size of the coconut shell charcoal is 200-300 mesh, the material of the amine is triethylenediamine, the palladium content in sodium chloropalladate is 36%, a preparation method for a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction, including the above-mentioned palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction, specifically comprising the following steps: the first step: preparing nitric acid-modified activated carbon: heating the activated carbon with nitric acid under reflux at a temperature of 80-90°C for 1h, washing the activated carbon to neutrality, and obtaining nitric acid-modified activated carbon; the second step: making a slurry Liquid and ultrasonic treatment: add nitric acid modified activated carbon to amine and sodium chloropalladate and mix them to form a slurry, and ultrasonicate at room temperature for 1 hour; the third step: drying treatment: the slurry after ultrasonic treatment is heated to 85°C for slow drying, stirred for 1 hour and then kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step: soaking, stirring, filtering and washing treatment: hydrochloric acid and ethanol aqueous solution are mixed together to obtain a mixed solution, the dried catalyst is soaked in the mixed solution and stirred for 1 hour, filtered and washed to obtain a palladium carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, which is loaded on activated carbon through amine and palladium coordination, and after heating, amine and palladium are partially reduced. The presence of amine makes the surface produce a certain steric hindrance, which improves the selectivity of hydrodechlorination, and the heating aging process increases the strength of the interaction between palladium and the carrier, and the addition of amine content is beneficial to control the ratio of Pd0 / Pd2+ in the catalyst and the amount of steric hindrance on the surface of the carrier, and the activity of the catalyst is changed by adjusting the ratio.

[0025] Example 3: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 25 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically triethylenediamine, and the palladium content in the sodium chloropalladate is 36%. A preparation method for a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps :The first step: preparing nitric acid modified activated carbon: heating the activated carbon with nitric acid under reflux for 1 hour at a temperature of 80-90°C, washing the activated carbon to neutrality, and obtaining nitric acid modified activated carbon; the second step: making slurry and ultrasonic treatment: adding amine and sodium chloropalladate to the nitric acid modified activated carbon and mixing them to make slurry, and ultrasonicating for 1 hour at room temperature; the third step: drying treatment: heating the ultrasonically treated slurry to 85°C for slow drying, stirring for 1 hour and then keeping warm for 4 hours, and finally transferring to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step: soaking, stirring, filtering and washing treatment: mixing hydrochloric acid and ethanol aqueous solution together to obtain a mixed solution, soaking the dried catalyst in the mixed solution and stirring for 1 hour, filtering and washing to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0026] Example 4: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 40 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically triethylenediamine, and the palladium content in the sodium chloropalladate is 36%. A preparation method for a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps :The first step: preparing nitric acid modified activated carbon: heating the activated carbon with nitric acid under reflux for 1 hour at a temperature of 80-90°C, washing the activated carbon to neutrality, and obtaining nitric acid modified activated carbon; the second step: making slurry and ultrasonic treatment: adding amine and sodium chloropalladate to the nitric acid modified activated carbon and mixing them to make slurry, and ultrasonicating for 1 hour at room temperature; the third step: drying treatment: heating the ultrasonically treated slurry to 85°C for slow drying, stirring for 1 hour and then keeping warm for 4 hours, and finally transferring to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step: soaking, stirring, filtering and washing treatment: mixing hydrochloric acid and ethanol aqueous solution together to obtain a mixed solution, soaking the dried catalyst in the mixed solution and stirring for 1 hour, filtering and washing to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0027] Example 5: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 50 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically triethylenediamine, and the palladium content in the sodium chloropalladate is 36%. A preparation method for a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps :The first step: preparing nitric acid modified activated carbon: heating the activated carbon with nitric acid under reflux for 1 hour at a temperature of 80-90°C, washing the activated carbon to neutrality, and obtaining nitric acid modified activated carbon; the second step: making slurry and ultrasonic treatment: adding amine and sodium chloropalladate to the nitric acid modified activated carbon and mixing them to make slurry, and ultrasonicating for 1 hour at room temperature; the third step: drying treatment: heating the ultrasonically treated slurry to 85°C for slow drying, stirring for 1 hour and then keeping warm for 4 hours, and finally transferring to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step: soaking, stirring, filtering and washing treatment: mixing hydrochloric acid and ethanol aqueous solution together to obtain a mixed solution, soaking the dried catalyst in the mixed solution and stirring for 1 hour, filtering and washing to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0028] Example 6: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 40 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically tert-butylamine, and the palladium content in the sodium chloropalladate is 36%. A preparation method for a palladium-carbon catalyst for hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps: The first step is to prepare nitric acid-modified activated carbon: the activated carbon is heated and refluxed with nitric acid at a temperature of 80-90°C for 1 hour, and the activated carbon is washed to neutrality to obtain nitric acid-modified activated carbon; the second step is to prepare slurry and ultrasonic treatment: the nitric acid-modified activated carbon is added with amine and sodium chloropalladate and mixed to prepare slurry, and ultrasonic treatment is performed at room temperature for 1 hour; the third step is to dry treatment: the ultrasonically treated slurry is heated to 85°C for slow drying, stirred for 1 hour, and then kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step is to soak, stir, filter and wash treatment: hydrochloric acid and ethanol aqueous solution are mixed together to obtain a mixed solution, the dried catalyst is soaked and stirred with the mixed solution for 1 hour, and filtered and washed to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0029] Example 7: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 40 parts of an amine, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically trimethylamine, and the palladium content in the sodium chloropalladate is 36%. A method for preparing a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps: The first step is to prepare nitric acid-modified activated carbon: the activated carbon is heated and refluxed with nitric acid at a temperature of 80-90°C for 1 hour, and the activated carbon is washed to neutrality to obtain nitric acid-modified activated carbon; the second step is to prepare slurry and ultrasonic treatment: the nitric acid-modified activated carbon is added with amine and sodium chloropalladate and mixed to prepare slurry, and ultrasonic treatment is performed at room temperature for 1 hour; the third step is to dry treatment: the ultrasonically treated slurry is heated to 85°C for slow drying, stirred for 1 hour, and then kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step is to soak, stir, filter and wash treatment: hydrochloric acid and ethanol aqueous solution are mixed together to obtain a mixed solution, the dried catalyst is soaked and stirred with the mixed solution for 1 hour, and filtered and washed to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0030] Comparative Example 1: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1As shown, it includes the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 12 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, the concentration of nitric acid is 0.625 mol / L, the weight percentage of hydrochloric acid is 5wt%, the weight percentage of the ethanol aqueous solution is 90wt%, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the palladium content in the sodium chloropalladate is 36%, a method for preparing a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, including the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps: the first step: preparing Nitric acid modified activated carbon: the activated carbon is heated and refluxed with nitric acid at a temperature of 85°C for 1 hour, and the activated carbon is washed to neutrality to obtain nitric acid modified activated carbon; the second step: making a slurry and ultrasonic treatment: the nitric acid modified activated carbon is added to sodium chloropalladate and mixed to form a slurry, and ultrasonicated at room temperature for 1 hour; the third step: drying treatment: the ultrasonically treated slurry is heated to 90°C for slow drying, stirred for 1 hour and then kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst; the fourth step: soaking, stirring, filtering and washing treatment: hydrochloric acid and ethanol aqueous solution are mixed together to obtain a mixed solution, the dried catalyst is soaked and stirred in the mixed solution for 1 hour, filtered and washed to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0031] Comparative Example 2: A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, such as Figure 1 As shown, it is made of the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 40 parts of an amine and 12 parts of sodium chloropalladate, the concentration of the nitric acid is 0.625 mol / L, the material of the carrier is specifically activated carbon, the material of the activated carbon is specifically coconut shell charcoal, the specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g, the particle size of the coconut shell charcoal is 200-300 meshes, the material of the amine is specifically triethylenediamine, and the palladium content in the sodium chloropalladate is 36%. A method for preparing a palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, comprising the above-mentioned palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, specifically comprising the following steps: the first step: preparing nitric acid; Acid-modified activated carbon: reflux the activated carbon with nitric acid at 80-90°C for 1h, wash the activated carbon to neutrality, and obtain nitric acid-modified activated carbon; Step 2: Prepare slurry and ultrasonically treat: add amine and sodium chloropalladate to the nitric acid-modified activated carbon and mix them to prepare slurry, and ultrasonicate at room temperature for 1h; Step 3: Drying: heat the slurry after ultrasonic treatment to 85°C for slow drying, stir for 1h, keep warm for 4h, and finally transfer to 120°C for drying for 4h to obtain a dried catalyst; Step 4: Soak, stir, filter and wash: filter and wash the dried catalyst to obtain a palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

[0032] Comparative Example 3: This example is a conventional method for a palladium carbon catalyst, and the steps are as follows: Step 1: The activated carbon is heated to reflux with 5% by mass nitric acid at 80°C for 1h, and then the activated carbon is washed to neutrality; Step 2: The above-mentioned activated carbon is prepared into a slurry, and a chloropalladic acid solution is added, and the pH is adjusted to about 9 with an alkaline solution; Step 3: Add dropwise a reducing agent, formaldehyde or sodium formate, wherein the molar ratio of the reducing agent to metallic palladium is about 3, reduce for 2h, and then filter and wash until there is no chloride ion detected with an AgNO3 solution. The catalysts of Comparative Example 1 and Comparative Example 2 and Examples 1 to 7 were used for the hydrogenation of polychlorinated pyridine 2,3,6-trichloropyridine to prepare 2,3-dichloropyridine to evaluate the catalytic performance of the prepared catalysts. The specific process is as follows: a certain volume of methanol, a substrate 2,3,6-trichloropyridine and a catalyst mass ratio of 100:1 were added, and a certain mass of sodium bicarbonate solution was added to the reactor, and then the temperature was raised to 50°C, N2 replaced the air in the reactor, H2 was filled to 2MPa, and the reaction was kept warm for 4h, and samples were taken for chromatographic analysis. The results of the catalyst in the hydrogenation of 2,3,6-trichloropyridine to prepare 2,3-dichloropyridine are shown in Table 1:

[0033] Table 1

[0034]

[0035]

[0036] As can be seen from Table 1, the palladium carbon catalyst treated with hydrochloric acid ethanol solution and triethylenediamine added during the preparation process has improved activity compared with the conventionally prepared palladium carbon comparative example 3 and comparative examples 1 and 2, especially the selectivity of the product is significantly improved. Further use of the catalyst in Example 4 found that it can be applied multiple times.

[0037] The working principle of the present invention is as follows: the palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridine prepared by the present invention cleverly introduces triethylenediamine, an amine compound, into the catalyst during the preparation process, and in the subsequent steps, the surface structure and active sites of the catalyst are optimized by soaking and stirring with hydrochloric acid and ethanol aqueous solution, thereby significantly improving the activity and selectivity of the catalyst in the hydrodechlorination reaction of polychlorinated pyridine. The introduction of triethylenediamine may affect the dispersion state of palladium on the activated carbon carrier through its coordination with palladium ions, thereby changing the active site structure of the catalyst, and the subsequent hydrochloric acid ethanol solution treatment may further optimize the surface of the catalyst by dissolving and washing away some inactive substances. The structure and active sites make it easier for the catalyst to adsorb and activate reactant molecules in the reaction, thereby improving the activity and selectivity of the catalyst. In addition, the palladium carbon catalyst prepared by the present invention can still maintain good activity and selectivity after multiple applications, which further proves the stability and practicality of the catalyst. This feature makes the catalyst have broad application prospects in industrial production. In summary, the palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction prepared by the present invention optimizes the surface structure and active sites of the catalyst by introducing triethylenediamine and hydrochloric acid ethanol solution treatment, significantly improves the activity and selectivity of the catalyst, and has good stability and practicality, providing a high-quality catalyst selection for industrial production.

[0038] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of a carrier, 300 parts of nitric acid, 4-60 parts of an amine, 14 parts of sodium chloropalladate, 160 parts of hydrochloric acid and 320 parts of an ethanol aqueous solution, wherein the concentration of the nitric acid is 0.625 mol / L, the weight percentage of the hydrochloric acid is 5wt%, and the weight percentage of the ethanol aqueous solution is 90wt%.

2. The palladium-carbon catalyst for the hydrodechlorination of polychlorinated pyridines according to claim 1, characterized in that: The material of the carrier is specifically activated carbon.

3. The palladium-carbon catalyst for the hydrodechlorination of polychlorinated pyridines according to claim 2, characterized in that: The material of the activated carbon is specifically coconut shell charcoal.

4. The palladium-carbon catalyst for the hydrodechlorination of polychlorinated pyridines according to claim 3, characterized in that: The specific surface area of ​​the coconut shell charcoal is not less than 1500 m2 / g.

5. The palladium-carbon catalyst for the hydrodechlorination of polychlorinated pyridines according to claim 3, characterized in that: The particle size of the coconut shell charcoal is between 200 and 300 meshes.

6. The palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines according to claim 1, characterized in that: The material of the amine is specifically triethylenediamine, tert-butylamine or trimethylamine.

7. The palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines according to claim 1, characterized in that: The content of palladium in the sodium chloropalladate is 36%.

8. A method for preparing a palladium-carbon catalyst for hydrodechlorination of polychlorinated pyridines, characterized in that: The method comprises the palladium-carbon catalyst for the hydrodechlorination reaction of polychlorinated pyridines according to any one of claims 1 to 7, and specifically comprises the following steps: Step 1: Preparation of nitric acid-modified activated carbon: reflux the activated carbon with nitric acid at 80-90°C for 1 hour, wash the activated carbon to neutrality, and obtain nitric acid-modified activated carbon; Step 2: Slurry preparation and ultrasonic treatment: nitric acid-modified activated carbon was added to amine and sodium chloropalladate and mixed to prepare slurry, and ultrasonicated at room temperature for 1 h; Step 3: Drying: The slurry after ultrasonic treatment was heated to 85°C for slow drying, stirred for 1 hour and kept warm for 4 hours, and finally transferred to 120°C for drying for 4 hours to obtain a dried catalyst; Step 4: Soaking, stirring, filtering and washing: Mix hydrochloric acid and ethanol aqueous solution together to obtain a mixed solution, soak the dried catalyst in the mixed solution and stir for 1 hour, filter and wash to obtain the palladium carbon catalyst for polychlorinated pyridine hydrodechlorination reaction.

Images