A process for the preparation of hexafluoroethane

Abstract

The present application relates to a kind of preparation methods of hexafluoroethane, which includes cobalt chloride loaded on activated carbon, fluorination process of doping metal elements such as nickel, copper, greatly increases the contact area of catalyst, and five fluorinated ethane is generated under the action of catalyst by being passed into at 200-700 DEG C.The catalyst after reaction can be repeatedly fluorinated and utilized, and the method of the present application has the advantages of easy availability of raw materials, simple process, high selectivity, high conversion rate, and reusable catalysts.

Description

Technical Field

[0001] This invention relates to a method for preparing hexafluoroethane. Background Technology

[0002] Hexafluoroethane is widely used in semiconductor manufacturing processes, such as as an etching gas for wafers and for cavity cleaning after chemical vapor deposition. With the development of semiconductor devices, the precision requirements of integrated circuits are becoming increasingly stringent, and hexafluoroethane, as a dry etching agent, offers advantages such as minimal edge-to-edge erosion, high etching rate, and high accuracy.

[0003] Currently, the industry generally uses the fluorine-chlorine exchange method to produce hexafluoroethane. However, the raw material used in this method, pentafluorochloroethane, is a highly toxic hazardous material. Furthermore, due to its susceptibility to heat and pressure buildup during transportation, it is prone to container rupture and is therefore a controlled product, making it difficult or even impossible to purchase.

[0004] There are also methods in the industry that use pentafluoroethane as a raw material to prepare hexafluoroethane, which has the advantages of readily available raw materials and low cost. However, the current catalyst used in the preparation of hexafluoroethane from pentafluoroethane is cobalt fluoride. The reaction process involves cobalt fluoride being fluorinated by hydrogen fluoride and / or fluorine gas to produce cobalt trifluoride. Cobalt trifluoride is then reacted with pentafluoroethane to produce hexafluoroethane. The unreacted pentafluoroethane can be reused through processes such as distillation. However, the cobalt fluoride catalyst in this method has problems such as amorphous shape and easy pulverization, which leads to a reduction in catalytic performance during production, significantly affecting the yield, and easily causing pipeline blockage and safety issues. Furthermore, cobalt trifluoride is extremely unstable and readily oxidizes and reduces to cobalt fluoride in air at room temperature. Therefore, cobalt trifluoride is not directly used in the process of preparing hexafluoroethane from pentafluoroethane. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art that uses pentafluorochloroethane as a raw material, and to provide a method for preparing hexafluoroethane using pentafluoroethane as a raw material. This method includes a method for preparing a catalyst. The catalyst obtained has the advantages of high specific surface area and high dispersibility, which can avoid the problems of amorphous cobalt fluoride and easy pulverization of catalysts in the prior art. It can also greatly improve the conversion rate and selectivity of hexafluoroethane. Furthermore, the catalyst can be repeatedly fluorinated and reused after the reaction is completed using the process of this invention.

[0006] To achieve the objectives of the above-mentioned invention, the technical solution adopted by this invention is as follows: A method for preparing hexafluoroethane, comprising the following steps: S1. Activated carbon pretreatment: Place the activated carbon in a muffle furnace and calcine it at 200-300℃ for 1-2 hours under a nitrogen atmosphere to remove the contaminants attached to the activated carbon. The calcined activated carbon is then ready for use. S2. Prepare a cobalt chloride solution using a suitable solvent (the amount of cobalt chloride does not need to be measured, just dissolved). Soak activated carbon in the cobalt chloride solution, with the mass ratio of cobalt chloride to activated carbon being 10-30% cobalt chloride. After soaking at room temperature (25-30℃) for 8 hours, the cobalt chloride solution soaked with activated carbon is then subjected to evaporation, drying, and calcination treatments. S3. The material obtained after calcination in S2, i.e., activated carbon loaded with cobalt chloride, is placed in a reactor. Fluorine gas and hydrogen fluoride gas are introduced to carry out fluorination and prepare the corresponding catalyst cobalt trifluoride. The flow rate of fluorine gas and hydrogen fluoride gas is 50-150 ml / min, the reaction temperature is 100℃-500℃, and the volume ratio of fluorine gas to hydrogen fluoride gas is 1:1-5:1. S4. After fluorination, switch to pentafluoroethane gas. Pentafluoroethane is converted to hexafluoroethane under the action of cobalt trifluoride catalyst. The flow rate of pentafluoroethane gas is 20-200 ml / min, and the reaction temperature is set to 200-700℃. After the reaction is completed, take a sample for testing (this process is continuous and samples are taken in real time).

[0007] Furthermore, the activated carbon selected in step s1 of this invention is activated carbon with a high specific surface area (high specific surface area activated carbon refers to activated carbon with a specific surface area exceeding 2500 m²). 2 / g of activated carbon).

[0008] Furthermore, the cobalt chloride used in step s2 of the present invention may contain a small amount (1%-5%) of metals such as copper chloride and nickel chloride.

[0009] Furthermore, the solvent used to prepare the cobalt chloride solution in step s2 of the present invention is a mixture of one or more solvents selected from deionized water, ethanol, and acetone.

[0010] Furthermore, in step s2 of this invention, the evaporation treatment involves heating the cobalt chloride solution soaked with activated carbon to 100-110°C until the solution is completely evaporated. After the evaporation treatment, the drying treatment is carried out at a temperature of 70-85°C for 6-8 hours. The calcination treatment is carried out in a muffle furnace under nitrogen protection at a temperature of 450-1100°C for 8-10 hours.

[0011] Furthermore, the cobalt chloride described in step s2 of the present invention is dissolved in deionized water or ethanol solution or a mixture of deionized water and ethanol solution, and its drying temperature is 70-85℃.

[0012] Furthermore, the calcination treatment in step s2 of this invention is carried out in a muffle furnace under nitrogen protection at a temperature of 450-1100℃ for 8-10 hours.

[0013] Furthermore, the preferred calcination temperature of the present invention is 800-900℃.

[0014] Furthermore, in step s3 of the present invention, the volume ratio of fluorine gas to hydrogen fluoride gas is 1:1-3:1, and the fluorination temperature is 100-200℃.

[0015] Furthermore, after step s4 of the present invention, that is, after the reaction is completed, fluorine gas is introduced again. Under the fluorination of fluorine gas, cobalt difluoride reacts again to generate cobalt trifluoride, which is used to synthesize hexafluoroethane again, realizing the repeated fluorination utilization of the catalyst. The fluorine gas flow rate is 100-200 ml / min; the fluorine gas temperature selected for this fluorination is 100-500℃.

[0016] Furthermore, in the present invention, the cobalt difluoride is fluorinated again under the fluorination of the fluorine gas to generate cobalt trifluoride. The preferred flow rate of the fluorine gas is 100-150 ml / min, and the preferred temperature of the fluorine gas is 100-200℃.

[0017] The beneficial effects of this invention are as follows: Traditional hexafluoroethane is prepared using the fluorine-chlorine exchange method. Due to regulatory requirements, the raw material pentafluorochloroethane is unavailable. This invention uses pentafluoroethane as a raw material to prepare hexafluoroethane, offering advantages such as readily available raw materials and low cost. However, existing technologies using pentafluoroethane as a raw material to prepare hexafluoroethane employ cobalt fluoride as a catalyst. As a solid powder, cobalt fluoride is amorphous and easily pulverized, leading to reduced catalytic performance, significantly impacting yield, and causing pipeline blockage and safety hazards. This invention uses a novel method to prepare the catalyst, completely solving these problems. This invention loads cobalt fluoride into the porous structure of activated carbon, impregnating powdered cobalt fluoride onto activated carbon, thus completely avoiding pulverization. Furthermore, this invention utilizes the properties of activated carbon to significantly increase the specific surface area of ​​cobalt fluoride. A larger specific surface area results in a multiplied increase in the contact area with the compound, thereby significantly improving the conversion rate and enhancing the selectivity of cobalt hexafluoroethane. Detailed Implementation

[0018] Example 1 Weigh 100g of activated carbon and place it in a muffle furnace under a nitrogen atmosphere for high-temperature treatment for 2 hours.

[0019] Weigh 30g of cobalt chloride and 5g of copper chloride, dissolve them in 100ml of deionized water, stir, and after they are completely dissolved, soak the dried activated carbon in the cobalt chloride and copper chloride aqueous solution for 4 hours.

[0020] After soaking, heat the beaker to 110°C until the aqueous solution is completely evaporated.

[0021] After evaporation, place the beaker in a drying oven at 75°C and dry for 8 hours.

[0022] After drying, the dried material is placed in a muffle furnace, purged with nitrogen, and calcined at 800℃ for 8 hours. The resulting catalyst precursor is then placed in a reactor, and fluorine and hydrogen fluoride gases are introduced. The flow rate of fluorine gas is 100 ml / min, and the flow rate of hydrogen fluoride is 100 ml / min. Fluorination is carried out at 200℃ for 3 hours.

[0023] After fluorination, pentafluoroethane was introduced (flow rate 20 ml / min), and the fluorination reaction was carried out at 400 °C. Samples were then taken for testing.

[0024] Example 2 Weigh 100g of activated carbon and place it in a muffle furnace under a nitrogen atmosphere for high-temperature treatment for 2 hours.

[0025] Weigh 30g of cobalt chloride and 5g of nickel chloride, dissolve them in 100ml of deionized water, stir, and after they are completely dissolved, soak the dried activated carbon in the cobalt chloride and nickel chloride aqueous solution for 4 hours.

[0026] After soaking, heat the beaker to 110°C until the aqueous solution is completely evaporated.

[0027] After evaporation, place the beaker in a drying oven at 75°C and dry for 8 hours.

[0028] After drying, the dried material is placed in a muffle furnace, purged with nitrogen, and calcined at 800℃ for 8 hours. The resulting catalyst precursor is then placed in a reactor, and fluorine and hydrogen fluoride gases are introduced. The flow rate of fluorine gas is 100 ml / min, and the flow rate of hydrogen fluoride is 100 ml / min. Fluorination is carried out at 200℃ for 3 hours.

[0029] After fluorination, pentafluoroethane was introduced (flow rate 20 ml / min), and the fluorination reaction was carried out at 400 °C. Samples were then taken for testing.

[0030] Example 3 Weigh 100g of activated carbon and place it in a muffle furnace under a nitrogen atmosphere for high-temperature treatment for 2 hours.

[0031] Weigh out 30g of cobalt chloride, 5g of copper chloride, and 5g of nickel chloride, dissolve them in 100ml of deionized water, stir, and after they are completely dissolved, soak the dried activated carbon in the aqueous solution of cobalt chloride, copper chloride, and nickel chloride for 4 hours.

[0032] After soaking, heat the beaker to 110°C until the aqueous solution is completely evaporated.

[0033] After evaporation, place the beaker in a drying oven at 75°C and dry for 8 hours.

[0034] After drying, the dried material is placed in a muffle furnace, purged with nitrogen, and calcined at 800℃ for 8 hours. The resulting catalyst precursor is then placed in a reactor, and fluorine and hydrogen fluoride gases are introduced. The flow rate of fluorine gas is 100 ml / min, and the flow rate of hydrogen fluoride is 100 ml / min. Fluorination is carried out at 200℃ for 3 hours.

[0035] After fluorination, pentafluoroethane was introduced (flow rate 20 ml / min), and the fluorination reaction was carried out at 400 °C. Samples were then taken for testing.

[0036] Example 4 Weigh 100g of activated carbon and place it in a muffle furnace under a nitrogen atmosphere for high-temperature treatment for 2 hours.

[0037] Weigh out 30g of cobalt chloride, 5g of copper chloride, and 5g of nickel chloride, dissolve them in 100ml of deionized water, stir, and after they are completely dissolved, soak the dried activated carbon in the aqueous solution of cobalt chloride, copper chloride, and nickel chloride for 4 hours.

[0038] After soaking, heat the beaker to 110°C until the aqueous solution is completely evaporated.

[0039] After evaporation, place the beaker in a drying oven at 75°C and dry for 8 hours.

[0040] After drying, the dried material is placed in a muffle furnace, purged with nitrogen, and calcined at 800℃ for 8 hours. The resulting catalyst precursor is then placed in a reactor, and fluorine and hydrogen fluoride gases are introduced. The flow rate of fluorine gas is 200 ml / min, and the flow rate of hydrogen fluoride is 100 ml / min. Fluorination is carried out at 200℃ for 3 hours.

[0041] After fluorination, pentafluoroethane was introduced (flow rate 20 ml / min), and the fluorination reaction was carried out at 400 °C. Samples were then taken for testing.

[0042] Once the catalytic efficiency of the catalyst decreases, fluorine gas is introduced at a flow rate of 100 ml / min. A second fluorination of the catalyst is then performed at 300°C for 3 hours. After fluorination, the catalyst can be used for the preparation of hexafluoroethane.

[0043] The following are the data results obtained by using an Agilent-7820 gas chromatograph for sampling and detection in the above embodiments 1-3 of the present invention.

[0044] Table 1 summarizes the catalyst state and catalytic experimental data. Table 2: Summary of catalytic yields for the catalyst used in Example 4 for secondary fluorination and reuse.

[0045] Based on the above test data, we can draw the following conclusions: Using the method of this invention, the catalyst prepared can increase the selectivity of hexafluoroethane to over 88% and the conversion rate to over 95% throughout the entire catalytic reaction experiment. Furthermore, reactivating and regenerating the catalyst further improves the reaction yield. Moreover, the catalyst after secondary reactivation retains a uniform distribution and does not pulverize. Therefore, the method of this invention not only avoids the problems of amorphous cobalt fluoride and easy catalyst pulverization in existing technologies, but also significantly improves the overall yield and selectivity, solving the problem of low yield and selectivity in existing technologies.

[0046] The advantages of this invention are that both selectivity and yield can reach a high level, while the raw material price is advantageous, the catalyst performance is good and avoids the problems of amorphous cobalt fluoride and easy pulverization of catalyst in the prior art. Furthermore, the secondary fluorination can make the catalyst reused, and the reuse of the catalyst can also improve the yield.

Claims

1. A method for preparing hexafluoroethane, characterized in that: The preparation method involves the following steps. S1. Activated carbon pretreatment: Place the activated carbon in a muffle furnace and calcine it at 200-300℃ for 1-2 hours under a nitrogen atmosphere to remove the contaminants attached to the activated carbon. The calcined activated carbon is then ready for use. S2. Prepare a cobalt chloride solution using a suitable solvent. Then, soak the activated carbon prepared in S1 into the cobalt chloride solution. The mass ratio of cobalt chloride to activated carbon is 10-30% of cobalt chloride. After soaking at 25-30℃ for 7-8 hours, the cobalt chloride solution soaked with activated carbon is successively subjected to evaporation, drying, and calcination. S3. The material obtained after calcination in S2, i.e., activated carbon loaded with cobalt chloride, is placed in a reactor. Fluorine gas and hydrogen fluoride gas are introduced to carry out fluorination and prepare the corresponding catalyst cobalt trifluoride. The flow rate of fluorine gas and hydrogen fluoride gas is 50-150 ml / min, the reaction temperature is 100-500℃, and the volume ratio of fluorine gas to hydrogen fluoride gas is 1:1-5:

1. S4. After fluorination, the flow rate of pentafluoroethane gas is changed to hexafluoroethane under the action of cobalt trifluoride catalyst. The flow rate of pentafluoroethane gas is 20-200 ml / min, and the reaction temperature is 200-700℃. After the reaction is completed, a sample is taken for testing. S5. After the reaction is complete, fluorine gas is introduced again. Under the fluorination of fluorine gas, cobalt difluoride reacts again to generate cobalt trifluoride, which is used to synthesize hexafluoroethane again, realizing the repeated fluorination and utilization of the catalyst. The fluorine gas flow rate is 100-200 ml / min, and the fluorine gas temperature selected for this fluorination is 100-500℃.

2. The method for preparing hexafluoroethane according to claim 1, characterized in that: The activated carbon used in step s1 is selected as high specific surface area activated carbon, which refers to activated carbon with a specific surface area exceeding 2500 m2 / g.

3. The method for preparing hexafluoroethane according to claim 1, characterized in that: The cobalt chloride used in step s2 is doped with 1%-5% copper chloride and / or nickel chloride.

4. The method for preparing hexafluoroethane according to claim 1, characterized in that: The solvent used to prepare the cobalt chloride solution in step s2 is a mixture of one or more solvents selected from deionized water, ethanol, and acetone.

5. The method for preparing hexafluoroethane according to claim 1, characterized in that: The cobalt chloride described in step s2 is dissolved in deionized water or ethanol solution or a mixture of deionized water and ethanol solution.

6. The method for preparing hexafluoroethane according to claim 1, characterized in that: The evaporation treatment in step s2 involves heating the cobalt chloride solution soaked with activated carbon to 100-110℃ until the solution is completely evaporated. After evaporation, the drying treatment is carried out at a temperature of 70-85℃ for 6-8 hours. The calcination treatment uses a muffle furnace under nitrogen protection at a temperature of 450-1100℃ for 8-10 hours.

7. The method for preparing hexafluoroethane according to claim 6, characterized in that: The calcination treatment in step s2 above is performed at a temperature of 800-900℃.

8. The method for preparing hexafluoroethane according to claim 1, characterized in that: In step s3, fluorination is carried out at a temperature of 100-200℃, with a flow rate of fluorine gas and hydrogen fluoride gas of 100-150 ml / min and a volume ratio of fluorine gas to hydrogen fluoride gas of 1:1-3:

1.

9. The method for preparing hexafluoroethane according to claim 1, characterized in that: In step S5, the re-introduction of fluorine gas is carried out at a flow rate of 100-150 ml / min and a temperature of 100-200℃.

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