Method for preparing octafluoropropane by taking nitrogen trifluoride as fluorine source

Abstract

The invention relates to a method for preparing octafluoropropane by taking nitrogen trifluoride as a fluorine source, which comprises the following steps: S1, introducing nitrogen trifluoride into a reactor, and preheating the reactor; s2, after preheating is completed, hexafluoropropylene is introduced into the reactor, and heating is stopped after reaction is started; s3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when the reactor reaches specified pressure, reaction products octafluoropropane and nitrogen are discharged out of the reactor; s4, after octafluoropropane and nitrogen are discharged, low-temperature condensation is conducted, octafluoropropane is collected during low-temperature condensation, and residual nitrogen is discharged after tail gas treatment. According to the invention, free fluorine ions generated by cracking nitrogen trifluoride at a certain temperature directly react with hexafluoropropylene to generate octafluoropropane, the reaction process is mild, and continuous production can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing fine chemical synthesis, and in particular to a method for preparing octafluoropropane by using nitrogen trifluoride as a fluorine source. Background Art

[0002] High-purity octafluoropropane has the advantages of small edge lateral erosion, high etching rate and high precision in certain processes of ultra-high integrated circuit etching and CVD chamber cleaning, which can well meet the requirements of low line width. With the rapid development of the global semiconductor industry, the demand for octafluoropropane as chip etching gas is also increasing.

[0003] One preparation process that has been reported in China is to extract octafluoropropane as a by-product produced during the production of carbon tetrafluoride or hexafluoropropylene. The octafluoropropane extracted as a by-product has a very high impurity content and its quality indicators are difficult to control.

[0004] Another process reported in China is to synthesize octafluoropropane by reacting hexafluoropropylene or heptafluoropropane with fluorine gas catalyzed by cobalt trifluoride. CN107540515A discloses a method for preparing octafluoropropane, which includes the following steps: S1, uniformly mixing hexafluoropropylene and diluted fluorine gas in molar ratio to obtain a mixed raw material gas; S2, passing the obtained mixed raw material gas into a fixed bed reactor equipped with a cobalt-based catalyst under appropriate temperature and pressure conditions to react and generate a mixed gas containing octafluoropropane; S3, passing the mixed gas containing octafluoropropane into an alkali washing tower and an adsorber in sequence for treatment to remove trace amounts of fluorine gas, hydrogen fluoride and water to obtain crude octafluoropropane; S4, conveying the obtained crude octafluoropropane into a distillation system for further refining to obtain high-purity octafluoropropane. CN107098790B discloses a method for preparing high-purity octafluoropropane, comprising the steps of: setting the reaction temperature to 50-250°C in a reactor, using cobalt trifluoride as a catalyst, hexafluoropropylene and fluorine gas as reaction gases, and reacting to prepare octafluoropropane; the molar ratio of the hexafluoropropylene to the fluorine gas is 1:2-6. The direct reaction of fluorine gas and hexafluoropropylene will release heat violently, the reaction process is uncontrollable, and the process risk is relatively large. Therefore, the cobalt trifluoride catalytic method uses cobalt trifluoride as a catalyst, which can make the reaction peaceful, with a high safety factor, and the output octafluoropropane has a relatively high purity and is easy to purify. However, the production process is discontinuous, the process is complicated, and the cobalt fluoride produced during the reaction is prone to coking, clogging and powdering. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source, so as to solve the technical problem that the cobalt fluoride produced in the process of preparing octafluoropropane by a cobalt trifluoride catalytic method is easy to pulverize and coke to block the production equipment.

[0006] To achieve the purpose of the present invention, the specific technical solutions provided by the present invention are as follows:

[0007] A method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source comprises the following steps:

[0008] S1, introducing nitrogen trifluoride into the reactor, and then preheating the reactor;

[0009] S2, after preheating is completed, hexafluoropropylene is introduced into the reactor, and heating is stopped after the reaction starts;

[0010] S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when the reactor reaches a specified pressure, the reaction products octafluoropropane and nitrogen are discharged from the reactor;

[0011] After S4, octafluoropropane and nitrogen are discharged, they are subjected to low-temperature condensation. Octafluoropropane is collected during the low-temperature condensation, and the remaining nitrogen is discharged after tail gas treatment.

[0012] Preferably, the purity of nitrogen trifluoride is ≥99.95%, and the purity of hexafluoropropylene is ≥99%.

[0013] Preferably, the nitrogen trifluoride and hexafluoropropylene are introduced into the reactor after being decompressed to 0.05-0.5 MPa.

[0014] Preferably, the reactor preheating temperature is 100-200° C., and the reactor pressure is controlled within 0.5 MPa.

[0015] Preferably, the volume ratio of the flow rates of nitrogen trifluoride and hexafluoropropylene introduced into the reactor is 0.6 to 2.4:1.

[0016] Preferably, the temperature of the low-temperature condensation is controlled to be -160 to -30°C.

[0017] Preferably, the purity of the reaction product octafluoropropane is ≥ 99%.

[0018] Preferably, the method comprises the following steps:

[0019] S1. Nitrogen trifluoride with a purity of ≥99.95% is decompressed to 0.05-0.5 MPa and then introduced into a reactor, and then the reactor is preheated to 100-200° C.;

[0020] S2. After preheating, hexafluoropropylene with a purity of ≥99% is depressurized to 0.05-0.5 MPa and then introduced into the reactor. The volume ratio of nitrogen trifluoride and hexafluoropropylene introduced into the reactor is 0.6-2.4:1. After the reaction starts, heating is stopped and the pressure of the reactor is controlled to be ≤0.5 MPa.

[0021] S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when the reactor reaches a predetermined value of 0.5MPa, the reaction products octafluoropropane and nitrogen are discharged from the reactor;

[0022] S4. After octafluoropropane and nitrogen are discharged, they are subjected to low-temperature condensation. The temperature of the low-temperature condensation is controlled at -160 to -30°C. Octafluoropropane is collected during the low-temperature condensation. The purity of the product octafluoropropane is ≥99%. The remaining nitrogen is discharged after tail gas treatment.

[0023] The present invention provides a method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source, which has the following beneficial effects:

[0024] 1. The present application utilizes the free fluoride ions generated by the cracking of nitrogen trifluoride at a certain temperature to directly react with hexafluoropropylene to generate octafluoropropane. The reaction process is mild and can achieve continuous production, avoiding the harmful fluorinating agents used in traditional fluorination methods. It is a safer and more environmentally friendly fluorination technology.

[0025] 2. This method uses high-purity raw materials (nitrogen trifluoride ≥ 99.95%, hexafluoropropylene ≥ 99%), combined with precisely controlled reaction conditions (inlet pressure is reduced to 0.05-0.5MPa, reaction temperature is 100-200°C), to ensure efficient reaction and produce octafluoropropane products with a purity of ≥ 99%. In this process, the utilization rate of raw materials is high and the amount of unreacted residues is small, which not only improves product quality but also reduces production costs. At the same time, the mildness and controllability of the reaction conditions make the entire production process safer and more stable, support continuous production mode, and further improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a device for preparing octafluoropropane according to the present invention;

[0027] Explanation of the markings in the figure: 1. Nitrogen trifluoride gas cylinder; 2. Hexafluoropropylene gas cylinder; 3. Reactor; 4. Low temperature cold trap. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation method, structure, characteristics and effects of the present invention are described in detail below in combination with the preferred embodiments.

[0029] The present application provides a method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source, such as Figure 1As shown, it is a schematic diagram of the device for preparing octafluoropropane in the present application. The specific method includes the following steps: nitrogen trifluoride with a purity of ≥99.95% stored in a nitrogen trifluoride gas cylinder 1 is depressurized to 0.05-0.5MPa by a pressure reducer, and then introduced into a reactor 3 at a certain flow rate, and the reactor 3 is preheated to 100-200°C; then hexafluoropropylene with a purity of ≥99% stored in a hexafluoropropylene gas cylinder 2 is depressurized to 0.05-0.5MPa by a pressure reducer, and then introduced into the reactor 3 at a certain flow rate, and the volume ratio of nitrogen trifluoride and hexafluoropropylene introduced into the reactor 3 is 0.6-2 .4:1, control the pressure of reactor 3 to ≤0.5MPa, and stop heating after the reaction starts; nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when reactor 3 reaches a predetermined value of 0-0.5MPa, open the valve into the cold trap to discharge the reaction products octafluoropropane and nitrogen out of reactor 3; after the octafluoropropane and nitrogen are discharged, they enter the low-temperature cold trap 4, and the temperature of the low-temperature cold trap 4 is controlled to be -160--30°C. Octafluoropropane is stored in the cold trap in liquid form, and the purity of the product octafluoropropane is ≥99%, and the remaining by-product nitrogen is discharged to the tail gas absorption tower through the valve.

[0030] Example 1

[0031] A method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source comprises the following steps:

[0032] S1. After nitrogen trifluoride with a purity of ≥99.95% stored in a gas cylinder is reduced to 0.05 MPa by a pressure reducer, it is introduced into the reactor 3 at a flow rate of 30 L / min, and the reactor 3 is preheated to 100° C.;

[0033] S2. After the preheating is completed, the hexafluoropropylene with a purity of ≥99% stored in the gas cylinder is depressurized to 0.05MPa by a pressure reducer, and then introduced into the reactor 3 at a flow rate of 50L / min, and the pressure of the reactor 3 is controlled to be ≤0.5MPa. After the reaction starts, the reactor 3 is closed for heating;

[0034] S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen. When the pressure in reactor 3 reaches a predetermined value of 0.5 MPa, the valve into the cold trap is opened to discharge the reaction products octafluoropropane and nitrogen out of reactor 3;

[0035] After S4, octafluoropropane and nitrogen are discharged, they first enter the low-temperature cold trap 4, the temperature of which is controlled at -160°C. Octafluoropropane is stored in the cold trap in liquid form, and the remaining by-product nitrogen is discharged to the tail gas absorption tower through a valve. After the obtained product is tested, the purity of octafluoropropane is 99.3%.

[0036] Example 2

[0037] A method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source comprises the following steps:

[0038] S1. After nitrogen trifluoride with a purity of ≥99.95% stored in a gas cylinder is reduced to 0.5 MPa by a pressure reducer, it is introduced into the reactor 3 at a flow rate of 110 L / min, and the reactor 3 is preheated to 200° C.;

[0039] S2. After preheating is completed, the hexafluoropropylene with a purity of ≥99% stored in the gas cylinder is depressurized to 0.5MPa by a pressure reducer, and then introduced into the reactor 3 at a flow rate of 50L / min, and the pressure of the reactor 3 is controlled to be ≤0.5MPa. After the reaction starts, the heating is stopped;

[0040] S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen. When the pressure in reactor 3 reaches a predetermined value of 0.5 MPa, the valve into the cold trap is opened to discharge the reaction products octafluoropropane and nitrogen out of reactor 3;

[0041] After S4, octafluoropropane and nitrogen are discharged, they first enter the low-temperature cold trap 4, the temperature of which is controlled at -30°C. Octafluoropropane is stored in the cold trap in liquid form, and the remaining by-product nitrogen is discharged to the tail gas absorption tower through a valve. After the obtained product is tested, the purity of octafluoropropane is 99.6%.

[0042] Example 3

[0043] A method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source comprises the following steps:

[0044] S1. After nitrogen trifluoride with a purity of ≥99.95% stored in a gas cylinder is reduced to 0.15 MPa through a pressure reducer, it is introduced into the reactor 3 at a flow rate of 55 L / min, and the reactor 3 is preheated to 150° C.;

[0045] S2. After preheating is completed, the hexafluoropropylene with a purity of ≥99% stored in the gas cylinder is depressurized to 0.15MPa by a pressure reducer, and then introduced into the reactor 3 at a flow rate of 50L / min, and the pressure of the reactor 3 is controlled to be ≤0.5MPa. After the reaction starts, the heating is stopped;

[0046] S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen. When the pressure in reactor 3 reaches a predetermined value of 0.5 MPa, the valve into the cold trap is opened to discharge the reaction products octafluoropropane and nitrogen out of reactor 3;

[0047] After S4, octafluoropropane and nitrogen are discharged, they first enter the low-temperature cold trap 4, the temperature of which is controlled at -60°C. Octafluoropropane is stored in the cold trap in liquid form, and the remaining by-product nitrogen is discharged to the tail gas absorption tower through a valve. After the obtained product is tested, the purity of octafluoropropane is 99.4%.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source, characterized in that: The method comprises the following steps: S1, introducing nitrogen trifluoride into the reactor, and then preheating the reactor; S2, after preheating is completed, hexafluoropropylene is introduced into the reactor, and heating is stopped after the reaction starts; S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when the reactor reaches a specified pressure, the reaction products octafluoropropane and nitrogen are discharged from the reactor; After S4, octafluoropropane and nitrogen are discharged, they are subjected to low-temperature condensation. Octafluoropropane is collected during the low-temperature condensation, and the remaining nitrogen is discharged after tail gas treatment.

2. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: The purity of nitrogen trifluoride is ≥99.95%, and the purity of hexafluoropropylene is ≥99%.

3. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: Nitrogen trifluoride and hexafluoropropylene are first decompressed to 0.05-0.5 MPa and then introduced into the reactor.

4. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: In step S1, the reactor preheating temperature is 100-300°C, and in step S3, the reactor pressure is controlled within 0.5 MPa.

5. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: The volume ratio of nitrogen trifluoride and hexafluoropropylene introduced into the reactor is 0.6 to 2.4:

1.

6. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: In step S4, the temperature of the low temperature condensation is -160 to -30°C.

7. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: The purity of the reaction product octafluoropropane is ≥99%.

8. The method for preparing octafluoropropane using nitrogen trifluoride as a fluorine source according to claim 1, characterized in that: The method comprises the following steps: S1. Nitrogen trifluoride with a purity of ≥99.95% is decompressed to 0.05-0.5 MPa and then introduced into a reactor, and then the reactor is preheated to 100-200° C.; S2. After preheating, hexafluoropropylene with a purity of ≥99% is depressurized to 0.05-0.5 MPa and then introduced into the reactor. The volume ratio of nitrogen trifluoride and hexafluoropropylene introduced into the reactor is 0.6-2.4:

1. After the reaction starts, heating is stopped and the pressure of the reactor is controlled to be ≤0.5 MPa. S3, nitrogen trifluoride and hexafluoropropylene react to generate octafluoropropane and nitrogen, and when the reactor reaches a predetermined value of 0.5MPa, the reaction products octafluoropropane and nitrogen are discharged from the reactor; S4. After octafluoropropane and nitrogen are discharged, they are subjected to low-temperature condensation. The temperature of the low-temperature condensation is controlled at -160 to -30°C. Octafluoropropane is collected during the low-temperature condensation. The purity of the product octafluoropropane is ≥99%. The remaining nitrogen is discharged after tail gas treatment.

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