Preparation method of dichlorooctafluorobutane

Abstract

The invention relates to the technical field of dichlorooctafluorobutane, in particular to a preparation method of dichlorooctafluorobutane, which comprises the following specific steps: S1, preparation of potassium nickel monohydrogen dichloride: the preparation method comprises the following steps: A, dissolving potassium chloride in deionized water to obtain a potassium chloride solution with the weight percentage concentration of 20-30%; b, dissolving nickel chloride in deionized water to obtain a nickel chloride solution, wherein the weight percentage concentration of the nickel chloride solution is 50-80%; and C, dropwise adding the nickel chloride solution obtained in the step B into the potassium chloride solution obtained in the step A, and reacting to prepare the potassium nickel trichloride solution. The 1, 1, 2-tetrafluoroethane with low raw material cost reacts with the catalyst nickel potassium hydrogen dichloride under ultraviolet light to generate the dichlorooctafluorobutane, so that the dichlorooctafluorobutane is low in cost, high in yield, low in waste content, easy to industrialize and suitable for industrial production. And the application process of replacing the traditional electronic etching agent carbon tetrafluoride with hexafluorobutadiene can be effectively accelerated.

Description

Technical Field

[0001] The invention relates to the technical field of dichlorooctafluorobutane, in particular to a method for preparing dichlorooctafluorobutane. Background Art

[0002] Dichlorooctafluorobutane is a chemical substance with the chemical formula C4Cl2F8 and a molecular weight of 270.94. Its density is 1.719 g / mL, melting point is -68°C, boiling point is 63°C, and refractive index is 1.313. In addition, the purity of dichlorooctafluorobutane can reach 99% and it has high chemical stability. Dichlorooctafluorobutane is the basic raw material for the preparation of hexafluorobutadiene, hexafluorobutyne, etc. Hexafluorobutadiene is a new type of environmentally friendly electronic etchant with the advantage of good etching accuracy.

[0003] At present, the invention patent with publication number CN113527033A discloses a method for preparing dichlorooctafluorobutane by photochlorination; the method for preparing dichlorooctafluorobutane by photochlorination of the invention promotes the reaction speed of the photochlorination, reduces the progress of side reactions, and reduces the phenomenon that it is difficult to separate by distillation due to the similar structure of by-product impurities. The high-purity product 2,3-dichlorooctafluorobutane can be obtained after further distillation and purification. At the same time, the reactant perfluorobutene itself is a solvent, and no additional solvent needs to be added, which significantly reduces the cost. However, the above method is to obtain the target product by reacting 2-perfluorobutene with chlorine, wherein the raw material cost is very expensive, the yield is low, there are many wastes, and the atom economy is not good. At the same time, the high cost restricts the application process of replacing traditional electronic etching agent carbon tetrafluoride with hexafluorobutadiene in my country. For this reason, we propose a method for preparing dichlorooctafluorobutane. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing dichlorooctafluorobutane, which has the advantages of low raw material cost, high yield and less waste, and solves the disadvantages of high raw material cost, low yield, much waste and poor atom economy. At the same time, the high cost restricts the application process of using hexafluorobutadiene to replace traditional electronic etching agent carbon tetrafluoride in my country.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing dichlorooctafluorobutane, in a tubular reactor, 1,1,1,2-tetrafluoroethane reacts with a catalyst of potassium dichloronickel under ultraviolet light to generate dichlorooctafluorobutane, and the reaction equation is as follows: 2CF3CH2F + 4Cl2 + KNiHCl2 ----- CF3CFCl-CFClCF3 + KNiCl3 + 5HCl The above catalyst can be reused by a hydrogenation activation method. The catalyst activation method is that the catalyst is activated under the action of hydrogen. The activation equation is: KNiCl3+H2-----KNiHCl2+HCl The method for preparing dichlorooctafluorobutane comprises the following specific steps: S1: Preparation of potassium nickel monohydrogen chloride: The preparation method comprises the following steps: A: Dissolve potassium chloride in deionized water to obtain a potassium chloride solution with a weight percentage concentration of 20-30%; B: dissolving nickel chloride in deionized water to obtain a nickel chloride solution having a weight percentage concentration of 50-80%; C: adding the nickel chloride solution obtained in B dropwise to the potassium chloride solution obtained in A to react and prepare a nickel potassium chloride solution, and evaporating the nickel potassium chloride solution to obtain nickel potassium chloride; D: directly subjecting the potassium nickel trichloride obtained in C to a hydrogenation reaction with hydrogen to obtain potassium nickel monohydrogen dichloride; S2: 17-27 kg of potassium nickel dichloride monohydrogenate are filled into 6 40x6000 transparent quartz tube reactors, the filling volume of the catalyst potassium nickel dichloride monohydrogenate is 27-34 liters, and the reactor is heated to 180-250°C; S3: N2 is introduced at a rate of 8-13 L / min to further dry the catalyst. After 4-6.5 hours, the temperature is raised to 230-270°C, and 1,1,1,2-tetrafluoroethane is preheated and introduced from the upper part of the tubular reactor, and chlorine is introduced from the lower part of the tubular reactor; S4: removing the reaction material from the bottom of the tubular reactor, washing it with water and alkali, drying it with molecular sieves, condensing it, collecting it with rectification, and sampling and analyzing it to obtain dichlorooctafluorobutane; S5: When the conversion rate and yield of 1,1,1,2-tetrafluoroethane decrease, stop feeding and switch to hydrogen feeding, keep the temperature of the tubular reactor at 350-420°C, the hydrogen feeding rate at 340-380L / min under standard conditions, and the pressure of the tubular reactor at 0.9Mpa. After 25-30min, the activation is completed; S6: Prepare to switch the feeding, the feeding rate of 1,1,1,2-tetrafluoroethane is 170-190 liters / min under standard conditions, the feeding rate of chlorine is 340-380 liters / min under standard conditions, the pressure of the tube reactor is maintained at 0.08 MPa, the reaction materials are removed from the bottom of the tube reactor, directly washed with water alkali, dried with molecular sieves, condensed, distilled, collected and sampled to obtain dichlorooctafluorobutane.

[0006] Preferably, the catalytic reaction temperature in the catalytic reaction equation is 150-250° C., the reaction pressure is 0.01-0.1 MPa, and the residence time is 10-20 seconds.

[0007] Preferably, the activation reaction temperature in the activation equation is 350-450° C., the reaction pressure is 0.1-0.8 MPa, and the residence time is 10-20 seconds.

[0008] Preferably, the ultraviolet light source in the catalytic reaction is a 110 volt 275 watt ultraviolet lamp source.

[0009] Preferably, the reaction temperature for preparing the potassium nickel chloride solution in step S1 C is 50-80° C., the pressure is normal pressure, and the reaction time is 5-8 hours.

[0010] Preferably, in step S1 D, the molar ratio of potassium nickel chloride to hydrogen is 1:1-1.2, the hydrogenation temperature is 350-450° C., the reaction pressure is 0.1-1 MPa, and the residence time is 10-20 seconds.

[0011] Preferably, the jacket of the quartz transparent tubular reactor in step S2 is heated by heat transfer oil.

[0012] Preferably, the feeding rate of 1,1,1,2-tetrafluoroethane in step S3 is 170-190 liters / min under standard conditions, the feeding rate of chlorine is 340-380 liters / min under standard conditions, and the pressure of the tubular reactor is maintained at 0.08 MPa.

[0013] Preferably, the molecular sieve drying temperature in step S4 is 200-350° C., and the drying time is 2-3.5 hours.

[0014] Preferably, the condensation temperature in step S4 is 62-63°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can generate dichlorooctafluorobutane by reacting 1,1,2-tetrafluoroethane with a low raw material cost with a catalyst of potassium dichloronickel under ultraviolet light, so that the cost of preparing dichlorooctafluorobutane is low, the yield is high, and the waste content is small, and it is easy to realize industrialization, and can effectively accelerate the application process of hexafluorobutadiene replacing traditional electronic etching agent carbon tetrafluoride.

[0016] 2. The catalyst of the present invention can be reused by a hydrogenation activation method, which ensures the production efficiency of the product and facilitates people's use, and can reduce the waste of resources and the preparation cost of dichlorooctafluorobutane. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the method steps of Comparative Example 1 of the present invention; Figure 2 This is a schematic diagram of the method steps of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0018] Embodiment 1: In this embodiment, dichlorooctafluorobutane is prepared by the following method, comprising the following steps: S1: Preparation of potassium nickel monohydrogen chloride: The preparation method comprises the following steps: A: Dissolve potassium chloride in deionized water to obtain a potassium chloride solution with a weight percentage concentration of 20%; B: dissolving nickel chloride in deionized water to obtain a nickel chloride solution having a weight percent concentration of 50%; C: adding the nickel chloride solution obtained in B dropwise to the potassium chloride solution obtained in A to react and prepare a nickel potassium chloride solution. The reaction temperature of the nickel potassium chloride solution is 50° C., the pressure is normal pressure, and the reaction time is 5 hours. The nickel potassium chloride solution is evaporated to obtain nickel potassium chloride. D: directly subjecting the potassium nickel trichloride obtained in C to a hydrogenation reaction with hydrogen, wherein the molar ratio of potassium nickel trichloride to hydrogen is 1:1, the hydrogenation temperature is 350°C, the reaction pressure is 0.1 MPa, and the residence time is 10 seconds, to obtain potassium nickel dichloride monohydrogenate; S2: 17 kg of potassium nickel monohydrogen chloride was filled into 6 40x6000 transparent quartz tube reactors. The jacket of the transparent quartz tube reactor was heated by heat transfer oil. The filling volume of the catalyst potassium nickel monohydrogen chloride was 27 liters. The reactor was heated to 180°C. The ultraviolet light source in the catalytic reaction was a 110V 275W ultraviolet lamp. S3: N2 is introduced at a rate of 8 L / min to further dry the catalyst. After 4 hours, the temperature is then raised to 230°C. 1,1,1,2-tetrafluoroethane is preheated and introduced from the upper part of the tubular reactor. The feeding rate of 1,1,1,2-tetrafluoroethane is 170 L / min under standard conditions. Chlorine is introduced from the lower part of the tubular reactor. The feeding rate of chlorine is 340 L / min under standard conditions. The pressure of the tubular reactor is maintained at 0.08 MPa. S4: The reaction material is removed from the bottom of the tubular reactor, washed with water and alkali, dried with molecular sieves, condensed, collected by distillation and sampled for analysis. After 1 hour, dichlorooctafluorobutane with a purity of 99% is collected, the conversion rate of 1,1,1,2-tetrafluoroethane is 95.3%, and the yield is 90.4%; S5: When the conversion rate and yield of 1,1,1,2-tetrafluoroethane decrease, stop feeding and switch to hydrogen feeding. Keep the temperature of the tubular reactor at 350°C, the hydrogen feeding rate at 340L / min under standard conditions, and the pressure of the tubular reactor at 0.9Mpa. After 25min, the activation is completed. S6: Prepare to switch the feeding, the feeding rate of 1,1,1,2-tetrafluoroethane is 170 L / min under standard conditions, the feeding rate of chlorine is 340 L / min under standard conditions, the pressure of the tube reactor is maintained at 0.08 MPa, the reaction materials are removed from the bottom of the tube reactor, directly washed with water alkali, dried with molecular sieves, condensed, distilled, collected and sampled, and after 1 hour, dichlorooctafluorobutane with a purity of 99% was collected, the conversion rate of 1,1,1,2-tetrafluoroethane was 95.1%, and the yield was 90.2%.

[0019] It should be noted that the preparation principle of the method for preparing dichlorooctafluorobutane from third-generation refrigeration-grade tetrafluoroethane is: CF3CFH2 is subjected to a photocatalytic chlorination coupling reaction to obtain CF3CFCl-CFClCF3, and the coupling agent used is KNiHCl2.

[0020] Embodiment 2: In this embodiment, dichlorooctafluorobutane is prepared by the following method, comprising the following steps: S1: Preparation of potassium nickel monohydrogen chloride: The preparation method comprises the following steps: A: Dissolve potassium chloride in deionized water to obtain a potassium chloride solution with a weight percentage concentration of 30%; B: dissolving nickel chloride in deionized water to obtain a nickel chloride solution having a weight percentage concentration of 80%; C: adding the nickel chloride solution obtained in B dropwise to the potassium chloride solution obtained in A to react and prepare a nickel potassium chloride solution. The reaction temperature of the nickel potassium chloride solution is 80° C., the pressure is normal pressure, and the reaction time is 8 hours. The nickel potassium chloride solution is evaporated to obtain nickel potassium chloride. D: directly subjecting the potassium nickel trichloride obtained in C to a hydrogenation reaction with hydrogen, wherein the molar ratio of potassium nickel trichloride to hydrogen is 1:1.2, the hydrogenation temperature is 450°C, the reaction pressure is 1 MPa, and the residence time is 20 seconds, to obtain potassium nickel dichloride monohydrogenate; S2: 27 kg of potassium nickel monohydrogen chloride was filled into 6 40x6000 transparent quartz tube reactors. The jacket of the transparent quartz tube reactor was heated by heat transfer oil. The filling volume of the catalyst potassium nickel monohydrogen chloride was 34 liters. The reactor was heated to 250°C. The ultraviolet light source in the catalytic reaction was a 110V 275W ultraviolet lamp. S3: N2 was introduced at a rate of 8 L / min to further dry the catalyst. After 6.5 hours, the temperature was raised to 270°C. 1,1,1,2-tetrafluoroethane was preheated and introduced from the upper part of the tubular reactor. The feeding rate of 1,1,1,2-tetrafluoroethane was 190 L / min under standard conditions. Chlorine was introduced from the lower part of the tubular reactor. The feeding rate of chlorine was 380 L / min under standard conditions. The pressure of the tubular reactor was maintained at 0.08 MPa. S4: The reaction material is removed from the bottom of the tubular reactor, washed directly with water, dried with molecular sieves, condensed, collected by distillation and sampled for analysis. One hour later, dichlorooctafluorobutane with a purity of 99% is collected, the conversion rate of 1,1,1,2-tetrafluoroethane is 94.5%, and the yield is 90.4%; S5: When the conversion rate and yield of 1,1,1,2-tetrafluoroethane decrease, stop feeding and switch to hydrogen feeding. Keep the temperature of the tubular reactor at 420°C, the hydrogen feeding rate at 380L / min under standard conditions, and the pressure of the tubular reactor at 0.9Mpa. After 30min, the activation is completed. S6: Prepare to switch the feeding, the feeding rate of 1,1,1,2-tetrafluoroethane is 190 L / min under standard conditions, the feeding rate of chlorine is 380 L / min under standard conditions, the pressure of the tube reactor is maintained at 0.08 MPa, the reaction materials are removed from the bottom of the tube reactor, directly washed with water alkali, dried with molecular sieves, condensed, distilled, collected and sampled, and after 1 hour, dichlorooctafluorobutane with a purity of 99% was collected, the conversion rate of 1,1,1,2-tetrafluoroethane was 94.4%, and the yield was 90.2%.

[0021] Embodiment 3: In this embodiment, a dichlorooctafluorobutane is prepared by the following method, comprising the following steps: S1: Preparation of potassium nickel monohydrogen chloride: The preparation method comprises the following steps: A: Dissolve potassium chloride in deionized water to obtain a potassium chloride solution with a weight percentage concentration of 25%; B: dissolving nickel chloride in deionized water to obtain a nickel chloride solution having a weight percentage concentration of 65%; C: adding the nickel chloride solution obtained in B dropwise to the potassium chloride solution obtained in A to react and prepare a nickel potassium chloride solution. The reaction temperature of the nickel potassium chloride solution is 65° C., the pressure is normal pressure, and the reaction time is 6.5 hours. The nickel potassium chloride solution is evaporated to obtain nickel potassium chloride. D: directly subjecting the potassium nickel trichloride obtained in C to a hydrogenation reaction with hydrogen, wherein the molar ratio of potassium nickel trichloride to hydrogen is 1:1.1, the hydrogenation temperature is 400°C, the reaction pressure is 0.5 MPa, and the residence time is 15 seconds, to obtain potassium nickel dichloride monohydrogenate; S2: 27 kg of potassium nickel monohydrogen chloride was filled into 6 40x6000 transparent quartz tube reactors. The jacket of the transparent quartz tube reactor was heated by heat transfer oil. The filling volume of the catalyst potassium nickel monohydrogen chloride was 31 liters. The reactor was heated to 215°C. The ultraviolet light source in the catalytic reaction was a 110V 275W ultraviolet lamp. S3: N2 is introduced at a rate of 8 L / min to further dry the catalyst. After 5 hours, the temperature is then raised to 255°C. 1,1,1,2-tetrafluoroethane is preheated and introduced from the upper part of the tubular reactor. The feeding rate of 1,1,1,2-tetrafluoroethane is 180 L / min under standard conditions. Chlorine is introduced from the lower part of the tubular reactor. The feeding rate of chlorine is 360 L / min under standard conditions. The pressure of the tubular reactor is maintained at 0.08 MPa. S4: The reaction material is removed from the bottom of the tubular reactor, washed directly with water, dried with molecular sieves, condensed, collected by distillation and sampled for analysis. After 1 hour, dichlorooctafluorobutane with a purity of 99% is collected, the conversion rate of 1,1,1,2-tetrafluoroethane is 96%, and the yield is 92%; S5: When the conversion rate and yield of 1,1,1,2-tetrafluoroethane decrease, stop feeding and switch to hydrogen feeding. Keep the temperature of the tubular reactor at 380°C, the hydrogen feeding rate at 360L / min under standard conditions, and the pressure of the tubular reactor at 0.9Mpa. After 28min, the activation is completed. S6: Prepare to switch the feeding, the feeding rate of 1,1,1,2-tetrafluoroethane is 180 L / min under standard conditions, the feeding rate of chlorine is 360 L / min under standard conditions, the pressure of the tube reactor is maintained at 0.08 MPa, the reaction materials are removed from the bottom of the tube reactor, directly washed with water alkali, dried with molecular sieves, condensed, distilled, collected and sampled, and after 1 hour, dichlorooctafluorobutane with a purity of 99% was collected, the conversion rate of 1,1,1,2-tetrafluoroethane was 95.8%, and the yield was 91.9%.

[0022] Comparative Example 1, compared with Example 1, dichlorooctafluorobutane was prepared by reacting 2-perfluorobutene with chlorine.

[0023] The preparation method comprises the following contents: Perfluorobutene and chlorine are introduced into a reactor, wherein the molar ratio of chlorine to perfluorobutene is 1-5:1, and a photochlorination reaction is carried out under a light environment. The reaction temperature is -20-100°C, the reaction pressure is 10-800 kPa, and the reaction residence time is 10-100 s. After the reaction is completed, the product 2,3-dichlorooctafluorobutane is obtained after discharging the material, alkali washing, drying, and distillation purification.

[0024] Comparative Example 2, compared with Example 1, according to the document Chemistry letters (1991)(10), 1825-6 describes a method for preparing dichlorooctafluorobutane, in which dichlorotetrafluoroethane is used as a raw material to react and prepare dichlorooctafluorobutane.

[0025] Application performance verification: the products prepared in Examples 1 to 3 of the present invention and the products prepared in Comparative Examples 1 to 2 were subjected to gas chromatography to detect the finished product content. The measured yield and selectivity of dichlorooctafluorobutane are shown in Table 1.

[0026] Table 1 is the yield and selectivity analysis of dichlorooctafluorobutane prepared in Examples 1-3 and Comparative Examples 1-2 Dichlorooctafluorobutane yield / % Dichlorooctafluorobutane selectivity / % Embodiment 1 99.1 99.2 Embodiment 2 99 99.1 Embodiment 3 98.9 99.02 Comparative Example 1 98.6 98.2 Comparative Example 2 89.01 90.21 As can be seen from Table 1, the dichlorooctafluorobutane prepared in Examples 1 to 3 has excellent yield and selectivity compared with the dichlorooctafluorobutane prepared in Comparative Examples 1 to 2.

[0027] The waste content and product cost of the products prepared in Examples 1 to 3 of the present invention were compared with those of the products prepared in Comparative Examples 1 to 2, and the waste content and product cost of the products were divided into ten stages from low to high, and the stages 1 to 10 were replaced by 1 to 10 points, where 1 to 3 points were low, 4 to 6 points were average, 7 to 8 points were relatively high, and 9 to 10 points were very high. The measured waste content and product cost of dichlorooctafluorobutane are shown in Table 2.

[0028] Table 2 is an analysis of the content and total cost of dichlorooctafluorobutane prepared in Examples 1-3 and Comparative Examples 1-2 Waste content Product Cost Embodiment 1 1 1 Embodiment 2 1 1 Embodiment 3 1 1 Comparative Example 1 1 7 Comparative Example 2 2 4 As can be seen from Table 2, the waste content and product cost of the dichlorooctafluorobutane prepared in Examples 1-3 are lower than those of the products prepared in Comparative Examples 1-2.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing dichlorooctafluorobutane, characterized in that: In a tubular reactor, 1,1,1,2-tetrafluoroethane reacts with the catalyst potassium dichloronickel under ultraviolet light to generate dichlorooctafluorobutane. The reaction equation is as follows: 2CF3CH2F + 3Cl2 + KNiHCl2 ----- CF3CFCl-CFClCF3 + KNiCl3 + 3HCl + H2 The above catalyst can be reused by a hydrogenation activation method. The catalyst activation method is that the catalyst is activated under the action of hydrogen, and the activation equation is: KNiCl3+H2-----KNiHCl2+HCl The method for preparing dichlorooctafluorobutane comprises the following specific steps: S1: Preparation of potassium nickel monohydrogen chloride: The preparation method comprises the following steps: A: Dissolve potassium chloride in deionized water to obtain a potassium chloride solution with a weight percentage concentration of 20-30%; B: dissolving nickel chloride in deionized water to obtain a nickel chloride solution having a weight percentage concentration of 50-80%; C: adding the nickel chloride solution obtained in B dropwise to the potassium chloride solution obtained in A to react and prepare a nickel potassium chloride solution, and evaporating the nickel potassium chloride solution to obtain nickel potassium chloride; D: directly subjecting the potassium nickel trichloride obtained in C to a hydrogenation reaction with hydrogen to obtain potassium nickel monohydrogen dichloride; S2: 17-27 kg of potassium nickel dichloride monohydrogenate are filled into 6 40x6000 transparent quartz tube reactors, the filling volume of the catalyst potassium nickel dichloride monohydrogenate is 27-34 liters, and the reactor is heated to 180-250°C; S3: N2 is introduced at a rate of 8-13 L / min to further dry the catalyst. After 4-6.5 hours, the temperature is raised to 230-270°C, and 1,1,1,2-tetrafluoroethane is preheated and introduced from the upper part of the tubular reactor, and chlorine is introduced from the lower part of the tubular reactor; S4: removing the reaction material from the bottom of the tubular reactor, washing it with water and alkali, drying it with molecular sieves, condensing it, collecting it with rectification, and sampling and analyzing it to obtain dichlorooctafluorobutane; S5: When the conversion rate and yield of 1,1,1,2-tetrafluoroethane decrease, stop feeding and switch to hydrogen feeding, keep the temperature of the tubular reactor at 350-420°C, the hydrogen feeding rate at 340-380L / min under standard conditions, and the pressure of the tubular reactor at 0.9Mpa. After 25-30min, the activation is completed; S6: Prepare to switch the feeding, the feeding rate of 1,1,1,2-tetrafluoroethane is 170-190 liters / min under standard conditions, the feeding rate of chlorine is 340-380 liters / min under standard conditions, the pressure of the tube reactor is maintained at 0.08 MPa, the reaction materials are removed from the bottom of the tube reactor, directly washed with water alkali, dried with molecular sieves, condensed, distilled, collected and sampled to obtain dichlorooctafluorobutane.

2. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The catalytic reaction temperature in the catalytic reaction equation is 150-250° C., the reaction pressure is 0.01-0.1 MPa, and the residence time is 10-20 seconds.

3. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The activation reaction temperature in the activation equation is 350-450° C., the reaction pressure is 0.1-0.8 MPa, and the residence time is 10-20 seconds.

4. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The ultraviolet light source in the catalytic reaction is a 110 volt 275 watt ultraviolet lamp source.

5. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The reaction temperature for preparing the potassium nickel chloride solution in step S1 C is 50-80° C., the pressure is normal pressure, and the reaction time is 5-8 hours.

6. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: In step S1 D, the molar ratio of potassium nickel chloride to hydrogen is 1:1-1.2, the hydrogenation temperature is 350-450° C., the reaction pressure is 0.1-1 MPa, and the residence time is 10-20 seconds.

7. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The jacket of the quartz transparent tubular reactor in step S2 is heated by heat transfer oil.

8. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: In step S3, the feeding rate of 1,1,1,2-tetrafluoroethane is 170-190 liters / min under standard conditions, the feeding rate of chlorine is 340-380 liters / min under standard conditions, and the pressure of the tubular reactor is maintained at 0.08 MPa.

9. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The molecular sieve drying temperature in step S4 is 200-350° C., and the drying time is 2-3.5 hours.

10. The method for preparing dichlorooctafluorobutane according to claim 1, characterized in that: The condensation temperature in step S4 is 62-63°C.

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