Method for continuously preparing 2-bromoheptafluoropropane

Abstract

The invention provides a method for continuously preparing 2-bromoheptafluoropropane, which belongs to the field of preparation of fluorine-containing organic intermediates, and is characterized in that heptafluoropropane and bromine are used as reaction raw materials, continuously pass through a reactor filled with a palladium-manganese bimetallic catalyst, and react at the temperature of 200-300 DEG C to prepare the 2-bromoheptafluoropropane. The used raw materials are cheap and easy to obtain, the catalyst preparation process is simple, the reaction temperature is low, the yield is high, and industrial production is easy.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing fluorine-containing organic intermediates, in particular to a method for continuously preparing 2-bromoheptafluoropropane. BACKGROUND

[0002] 2-bromoheptafluoropropane is an important bromine-based fine chemical, which is currently mainly used to replace 2-iodoheptafluoropropane to synthesize pharmaceutical and pesticide intermediates. As a raw material intermediate for the synthesis of bromofenoximate, 2-bromoheptafluoropropane plays a key role. With pharmaceutical and pesticide enterprises trying to introduce heptafluoroisopropyl into the molecular formula of pharmaceuticals and pesticides by using 2-bromoheptafluoropropane, and replacing the reactions involving 2-iodoheptafluoropropane with 2-bromoheptafluoropropane as much as possible to synthesize more key intermediates of pharmaceuticals and pesticides, the demand for 2-bromoheptafluoropropane will further increase.

[0003]

[0004] 2-bromoheptafluoropropane production and storage conditions are harsh, so there are only a few manufacturers in the world. There are two main synthesis routes for 2-bromoheptafluoropropane: hexafluoropropene method and heptafluoropropane method. The hexafluoropropene method uses hexafluoropropene as the raw material, first adds bromine to generate 1,2-dibromoheptafluoropropane; and then 1,2-dibromoheptafluoropropane is fluorinated with potassium fluoride or other fluorinating reagents to generate 2-bromoheptafluoropropane. For example, the Chinese patent document with publication number CN 117986079 A discloses a method for continuously preparing 2-bromoheptafluoropropane in a high-throughput microchannel full-process, which has mild reaction conditions, high yield, safe and controllable reaction process, and reduces energy consumption. However, KF is easy to be damp and toxic, and more solvents are used, which has great environmental pressure.

[0005]

[0006] The heptafluoropropane method uses heptafluoropropane as the raw material, and directly performs bromination reaction with bromine at high temperature to generate 2-bromoheptafluoropropane. For example, the Chinese patent document with publication number CN 101768047 B discloses a method for preparing 2-bromoheptafluoropropane, which has a short process flow and does not need solvents, and has great potential for industrialization. However, the reaction temperature is high, and the conversion rate of the raw material heptafluoropropane is low, which is 52.7% when the reaction temperature is 450-500℃. Meanwhile, the relative amount of the byproduct HBr is large, and the post-processing process has great load. Meanwhile, the patent tries to use copper bromide and cuprous bromide as catalysts to reduce the reaction temperature, but the effect is not ideal, and the conversion rate of heptafluoropropane is only 28.5% and the selectivity is 98.3% under the reaction condition of 350℃. SUMMARY

[0007] The purpose of this invention is to provide a continuous method for preparing 2-bromoheptafluoropropane. This method uses heptafluoropropane and bromine as reactants and achieves efficient synthesis of 2-bromoheptafluoropropane under the action of a palladium-manganese bimetallic catalyst. It has the advantages of fewer side reactions, lower reaction temperature, and higher reaction conversion rate.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A continuous method for preparing 2-bromoheptafluoropropane, comprising the following steps: Heptafluoropropane and bromine are mixed and continuously fed into a reactor containing a Pd-Mn / C bimetallic catalyst for reaction. After the reaction is completed, the reactants are cooled and then subjected to alkaline washing, dehydration, distillation and drying to finally obtain 2-bromoheptafluoropropane.

[0009] The Pd-Mn / C bimetallic catalyst is prepared by preparing an impregnation solution of palladium salt, manganese salt and ammonia solution, impregnating it on an activated carbon support, and then filtering, washing, drying and calcining it after a certain impregnation time. The mass fraction of palladium is 2.0-6.8%, the mass fraction of manganese is 2.6-8.0%, and the remainder is activated carbon support.

[0010] Preferably, the reaction temperature is 200–300°C.

[0011] Preferably, the mixture of heptafluoropropane and bromine is continuously fed into a reactor containing a Pd-Mn / C bimetallic catalyst for reaction, with a feed mass hourly space velocity (WHSV) of 50–200 h⁻¹. -1 .

[0012] Preferably, the mass ratio of heptafluoropropane to bromine is 0.6 to 1.2:1.

[0013] Preferably, the palladium salt is any one of palladium chloride, palladium acetate, palladium nitrate, and palladium acetylacetonate.

[0014] Preferably, the manganese salt is one of manganese chloride, manganese acetate, manganese nitrate, or manganese sulfate.

[0015] Preferably, the ammonia water has a mass fraction of 20-40%, and the mass ratio of ammonia water to palladium salt is 10-20:1.

[0016] Preferably, the immersion temperature is 40–80°C and the immersion time is 2–6 hours.

[0017] Preferably, the calcination temperature is 400–600°C and the calcination time is 2–8 hours.

[0018] The beneficial effects of the present invention are as follows: (1) The present invention uses palladium-manganese bimetallic catalyst. Through the combination of palladium atoms in the catalyst and hydrogen atoms in heptafluoropropane, the dissociation energy of the CH bond of heptafluoropropane can be effectively reduced, thereby reducing the reaction temperature from 450℃ in the traditional method to below 300℃. At the same time, manganese atoms in the catalyst can effectively promote the cracking of bromine and generate bromine free radicals. The high specific surface area of ​​activated carbon can effectively adsorb heptafluoropropane and bromine, causing a large number of collisions in the pore structure, promoting the reaction, thereby effectively improving the conversion rate of the reaction, increasing the conversion rate of heptafluoropropane from 52.7% to more than 85%, and reducing the energy and material consumption of heptafluoropropane recycling. (2) The reduction in reaction temperature not only reduces energy consumption, but also reduces the corrosiveness of bromine, reducing the corrosion resistance requirements of equipment, reducing investment costs and operating costs, and is more conducive to industrial production. (3) Compared with the hexafluoropropylene method, the process flow of the present invention is shorter, does not require solvents, and has less wastewater discharge. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention. Example 1

[0020] Activated carbon was dried in a tube furnace at 300℃ for 4 hours to obtain dried activated carbon. 3g of palladium chloride, 5g of manganese dichloride, and 60ml of 20% ammonia water were weighed to prepare a bimetallic salt solution. 20g of dried activated carbon was weighed and placed in a three-necked flask. The prepared bimetallic salt solution was then poured onto the dried activated carbon, stirred evenly, and allowed to stand at 40℃ for 6 hours. After impregnation, the solution was cooled to room temperature, filtered, washed three times with acetone, dried under vacuum, and placed in a vacuum drying oven at 100℃ for 10 hours. The dried catalyst was calcined at 400℃ for 8 hours, then pressed, crushed, and sieved to obtain a 20-40 mesh catalyst with 6.8Pd-8.0Mn / C, denoted as catalyst A.

[0021] 10g of catalyst A particles were loaded into a fixed-bed tubular reactor and purged three times with nitrogen, maintaining the temperature at 300℃. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed tubular reactor containing catalyst A, with a mass ratio of heptafluoropropane to bromine of 1.2:1 and a feed mass hourly space velocity of 200 h⁻¹. -1After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 85.3% and a selectivity of 99.7%. Example 2

[0022] Activated carbon was dried in a tube furnace at 400℃ for 5 hours to obtain dried activated carbon. 2g of palladium acetate, 2g of manganese sulfate, and 20ml of 40wt% ammonia water were weighed to prepare a bimetallic salt solution. 20g of dried activated carbon was weighed and placed in a three-necked flask. The prepared bimetallic salt solution was then poured onto the dried activated carbon, stirred evenly, and allowed to stand at 80℃ for 2 hours. After impregnation, the solution was cooled to room temperature, filtered, washed three times with acetone, dried under vacuum, and placed in a vacuum drying oven at 100℃ for 10 hours. The dried catalyst was calcined at 600℃ for 2 hours, then pressed, crushed, and sieved to obtain a 20-40 mesh catalyst with 3.9Pd-4.5Mn / C, denoted as Catalyst B.

[0023] 10g of catalyst B particles were loaded into a fixed-bed tubular reactor, and the reactor temperature was maintained at 200℃ using nitrogen purging three times and high-low temperature cycling. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed tubular reactor containing catalyst B, with a mass ratio of heptafluoropropane to bromine of 0.6:1 and a feed mass hourly space velocity of 50 h⁻¹. -1 After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 91.5% and a selectivity of 99.4%. Example 3

[0024] Activated carbon was dried in a tube furnace at 400℃ for 5 hours to obtain dried activated carbon. A bimetallic salt solution was prepared by weighing 1g palladium nitrate, 2g manganese acetate, and 30ml of 30wt% ammonia. 20g of dried activated carbon was placed in a three-necked flask, and the prepared bimetallic salt solution was poured onto the dried activated carbon. After stirring evenly, the solution was allowed to stand at 60℃ for 4 hours. After impregnation, the solution was cooled to room temperature, filtered, washed three times with acetone, dried under vacuum, and then placed in a vacuum drying oven at 100℃ for 10 hours. The dried catalyst was calcined at 500℃ for 4 hours, and then the catalyst was pressed, crushed, and sieved to obtain a 20-40 mesh catalyst with 2.0Pd-2.6Mn / C, denoted as catalyst C.

[0025] 10g of catalyst C particles were loaded into a fixed-bed reactor and purged three times with nitrogen. The reactor temperature was controlled at 250℃ using a high-low temperature cycle. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed reactor containing catalyst B, with a mass ratio of heptafluoropropane to bromine of 1:1 and a feed mass hourly space velocity of 100 h⁻¹. -1 After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 88.7% and a selectivity of 99.6%. Example 4

[0026] Activated carbon was dried in a tube furnace at 400℃ for 5 hours to obtain dried activated carbon. 2g of palladium acetylacetonate, 3g of manganese nitrate, and 30ml of 25wt% ammonia water were weighed to prepare a bimetallic salt solution. 20g of dried activated carbon was weighed and placed in a three-necked flask. The prepared bimetallic salt solution was then poured onto the dried activated carbon, stirred thoroughly, and allowed to stand at 50℃ for 3 hours. After the reaction was complete, the solution was cooled to room temperature, filtered, washed three times with acetone, dried under vacuum, and placed in a vacuum drying oven at 100℃ for 10 hours. The dried catalyst was calcined at 500℃ for 4 hours, then pressed, crushed, and sieved to obtain a 20-40 mesh catalyst with 2.8Pd-3.8Mn / C, denoted as catalyst D.

[0027] 10g of catalyst D particles were loaded into a fixed-bed tubular reactor, and the reactor temperature was maintained at 280℃ through nitrogen purging three times and high-low temperature circulation. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed tubular reactor containing catalyst B, with a mass ratio of heptafluoropropane to bromine of 0.8:1 and a feed mass hourly space velocity of 150 h⁻¹. -1 After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 90.8% and a selectivity of 99.7%. Example 5

[0028] The catalyst preparation conditions were the same as in Example 1. 10g of catalyst A particles were loaded into a fixed-bed tubular reactor, purged three times with nitrogen, and the temperature was controlled at 300℃. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed tubular reactor containing catalyst A, with a mass ratio of heptafluoropropane to bromine of 0.8:1 and a feed mass hourly space velocity of 100 h⁻¹. -1After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 91.2% and a selectivity of 99.5%. Example 6

[0029] The catalyst preparation conditions were the same as in Example 1. 10g of catalyst A particles were loaded into a fixed-bed tubular reactor, and the reactor was purged three times with nitrogen. The reactor temperature was controlled at 250℃ using a high-low temperature cycle. Heptafluoropropane and bromine were mixed in a mixer and continuously fed into the fixed-bed tubular reactor containing catalyst A, with a mass ratio of heptafluoropropane to bromine of 1:1 and a feed mass hourly space velocity (WHSV) of 50 h⁻¹. -1 After the reaction is complete, the temperature is lowered to room temperature through a heat exchanger, and then an aqueous sodium hydroxide solution is passed through to absorb the unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane is obtained as the final product, with a conversion rate of 89.5% and a selectivity of 99.8%. Comparative Example 1

[0030] The difference from Example 1 is that 4g of palladium chloride was added in the catalyst preparation, resulting in a catalyst with 8.8Pd-7.8Mn / C. All other conditions remained the same. After the reaction, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a heptafluoropropane conversion rate of 90.2% and a selectivity of 94.3%. Comparative Example 2

[0031] The difference from Example 1 is that 0.5 g of palladium chloride was added in the catalyst preparation, resulting in a catalyst with a concentration of 0.7Pd-8.0Mn / C. All other conditions remained the same. After the reaction, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a heptafluoropropane conversion rate of 78.3% and a selectivity of 99.4%. Comparative Example 3

[0032] The difference from Example 1 is that 6g of manganese dichloride was added in the catalyst preparation, resulting in a catalyst with a Pd-9.5Mn / C ratio of 6.7%. All other conditions remained the same. After the reaction, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a heptafluoropropane conversion rate of 82.3% and a selectivity of 95.4%. Comparative Example 4

[0033] The difference from Example 1 is that 1g of manganese dichloride was added in the catalyst preparation, resulting in a catalyst with a composition of 7.6Pd-1.4Mn / C. All other conditions remained the same. After the reaction, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a conversion rate of 85.7% and a selectivity of 94.7%. Comparative Example 5

[0034] The difference from Example 5 is that the reaction temperature was 350°C, while other conditions remained the same. After the reaction was completed, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a heptafluoropropane conversion rate of 90.1% and a selectivity of 76.3%. Comparative Example 6

[0035] The difference from Example 5 is that the reaction temperature was 150°C, while other conditions remained the same. After the reaction was completed, the temperature was lowered to room temperature using a heat exchanger, and then an aqueous sodium hydroxide solution was passed through to absorb unreacted bromine and the byproduct hydrogen bromide. Finally, after dehydration, distillation, and drying, 2-bromoheptafluoropropane was obtained as the final product, with a heptafluoropropane conversion rate of 50.6% and a selectivity of 99.7%.

[0036]

[0037] As shown in Table 1, the technical solution provided in this application achieves a 2-bromoheptafluoropropane conversion rate of 85.3%–91.2% and a selectivity greater than 99%. However, in the comparative examples, excessively high or low proportions of palladium or manganese salts lead to decreased reaction conversion or selectivity, indicating that the proportion of metal salts in the catalyst has a significant impact on the reaction. Similarly, excessively high or low reaction temperatures also significantly affect the reaction conversion or selectivity.

[0038] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A continuous method for preparing 2-bromoheptafluoropropane, characterized in that, Heptafluoropropane and bromine are mixed and continuously fed into a reactor containing a Pd-Mn / C bimetallic catalyst for reaction. After the reaction is completed, the reactants are cooled to room temperature and then subjected to alkaline washing, dehydration, distillation and drying to finally obtain 2-bromoheptafluoropropane product. The Pd-Mn / C bimetallic catalyst is prepared by preparing an impregnation solution of palladium salt, manganese salt and ammonia solution, impregnating it on an activated carbon support, and after sufficient impregnation, filtering, washing, drying and calcining. The mass fraction of palladium in the Pd-Mn / C bimetallic catalyst is 2.0-6.8%, the mass fraction of manganese is 2.6-8.0%, and the balance is activated carbon support.

2. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The process involves continuously feeding a mixture of heptafluoropropane and bromine into a reactor containing a Pd-Mn / C bimetallic catalyst, with a feed mass hourly space velocity (WHSV) of 50–200 h⁻¹. -1 The reaction temperature is 200–300℃.

3. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The mass ratio of heptafluoropropane to bromine is 0.6 to 1.2:

1.

4. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The palladium salt is any one of palladium chloride, palladium acetate, palladium nitrate, and palladium acetylacetonate.

5. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The manganese salt mentioned is one of manganese chloride, manganese acetate, manganese nitrate, or manganese sulfate.

6. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The ammonia water has a mass fraction of 20-40%, and the mass ratio of ammonia water to palladium salt is 10-20:

1.

7. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The impregnation temperature is 40–80°C, and the impregnation time is 2–6 hours.

8. The method for continuous preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The roasting temperature is 400-600℃, and the roasting time is 2-8 hours.

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