Process for the preparation of 2,3,3,3-tetrafluoropropene

Abstract

This invention discloses a method for preparing 2,3,3,3-tetrafluoropropylene, comprising reacting carbon tetrachloride with ethylene in the presence of a catalyst containing reduced iron powder and a co-catalyst, separating and purifying the reactants to obtain HCC-250fb; subjecting HCC-250fb to dehydrochlorination to generate HCC-1240za; reacting HCC-250fb with chlorine in a liquid-phase or gas-phase chlorination reaction to obtain HCC-240db; reacting HCC-240db with hydrogen fluoride in a gas-phase fluorination reaction to generate HCFO-1233xf; and reacting HCFO-1233xf with hydrogen fluoride in a gas-phase fluorination reaction in the presence of a supported or unsupported chromium oxide catalyst to generate HFO-1234yf. The method of this invention uses readily available raw materials, has low cost, and allows unreacted raw materials to be recycled for further reactions, resulting in minimal waste emissions.

Description

Technical Field

[0001] This invention relates to the field of organofluorine chemical technology, and more particularly to a method for preparing 2,3,3,3-tetrafluoropropylene. Background Technology

[0002] 2,3,3,3-Tetrafluoropropylene (HFO-1234yf) is an important fourth-generation fluorinated hydrocarbon refrigerant with zero ozone depletion potential (ODP), a global warming potential (GWP) of less than 1, and a short atmospheric lifetime. It is widely recognized as an ideal environmentally friendly alternative to the traditional high-GWP refrigerant HFC-134a in fields such as automotive air conditioning.

[0003] There are numerous synthetic routes for HFO-1234yf. Typical routes include: using pentachloropropane (HCC-240fa) as a starting material, followed by fluorination, dehydrochlorination, and other multi-step reactions; or using 1,1,1,2,3-pentachloropropane (HCC-240db) as a key intermediate for gas-phase fluorination; and routes using trichloroethylene as a starting material for telomerization, chlorination, and refluorination. While these existing technologies have achieved industrialization or have industrialization potential, they still suffer from some common or route-specific drawbacks. For example, some routes involve expensive or limited-supply starting materials, leading to high production costs; the reaction steps are lengthy, limiting the overall yield and affecting economic efficiency; in the crucial gas-phase fluorination step, the catalyst is prone to deactivation due to carbon buildup, requiring frequent regeneration and affecting the stability of continuous production; some routes involve highly toxic or corrosive intermediates, placing higher demands on equipment materials and operational safety; furthermore, some routes produce complex byproducts that are difficult to separate and purify, increasing post-processing costs and environmental burden. Summary of the Invention

[0004] The purpose of this invention is to provide a technical solution for preparing 2,3,3,3-tetrafluoropropylene by addressing the shortcomings of existing technologies. This method uses readily available raw materials, has low cost, and allows unreacted raw materials to be recycled for further reaction, resulting in minimal emissions of waste.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for preparing 2,3,3,3-tetrafluoropropylene, characterized by comprising the following steps:

[0007] Step 1: In the presence of a catalyst containing reduced iron powder and a co-catalyst, carbon tetrachloride is reacted with ethylene at a reaction temperature of 80℃~150℃, a reaction pressure of 0~3MPa, and a reaction time of 2h~10h. 1,1,1,3-Tetrachloropropane (HCC-250fb) is obtained by separation and purification.

[0008] Step 2: In the presence of a catalyst containing metal chloride supported on activated carbon, the 1,1,1,3-tetrachloropropane obtained in Step 1 is subjected to a dehydrochlorination reaction at a temperature of 200℃~400℃ to produce 1,1,3-trichloropropene (HCC-1240za).

[0009] Step 3: In a solvent, at a temperature of 30℃~200℃, and in the presence of a metal halide catalyst, 1,1,3-trichloropropene obtained in Step 2 is subjected to a liquid-phase or gas-phase chlorination reaction with chlorine to obtain 1,1,1,2,3-pentachloropropane (HCC-240db).

[0010] Step 4: In the presence of a supported or unsupported chromium oxide catalyst, the 1,1,1,2,3-pentachloropropane obtained in Step 3 is subjected to a gas-phase fluorination reaction with hydrogen fluoride at a temperature of 200℃~400℃ to generate 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf).

[0011] Step 5: In the presence of a supported or unsupported chromium oxide catalyst, the 2-chloro-3,3,3-trifluoropropene obtained in Step 4 is subjected to a gas-phase fluorination reaction with hydrogen fluoride at a temperature of 200℃~450℃ to generate 2,3,3,3-tetrafluoropropene (HFO-1234yf).

[0012] Furthermore, the cocatalyst in step 1 includes phosphate esters or phosphites, wherein the cocatalyst is at least one of tributyl phosphate, dibutyl phosphate, triethyl phosphate, trimethyl phosphite, and tributyl phosphite.

[0013] Furthermore, the metal chloride in step 2 is at least one of ferric chloride, barium chloride, and copper chloride.

[0014] Furthermore, in step 3, when a liquid-phase reaction is used, the metal halide catalyst is at least one of ferric chloride, chromium chloride, aluminum chloride, and copper chloride, the solvent is at least one of carbon tetrachloride, chloroform, and dichloromethane, and the reaction temperature is 30℃~150℃.

[0015] Furthermore, in step 3, when a gas-phase reaction is used, the metal halide catalyst is ferric chloride, chromium chloride, aluminum chloride, and copper chloride supported on activated carbon, and the reaction temperature is 50℃~200℃.

[0016] Furthermore, the loading in step 4 and / or step 5 is at least one of magnesium, zinc, aluminum, nickel, and cobalt.

[0017] Furthermore, the reaction temperature in step 5 is 20°C to 80°C higher than that in step 4.

[0018] Furthermore, the method includes an alternative route for converting the 2-chloro-3,3,3-trifluoropropene generated in step 4 to 2,3,3,3-tetrafluoropropene, the alternative route comprising the following steps in sequence:

[0019] Liquid-phase fluorination reaction: In the presence of a catalyst, 2-chloro-3,3,3-trifluoropropene obtained in step 4 is reacted with hydrogen fluoride at a temperature of 30℃~150℃ to generate 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb).

[0020] Dehydrochlorination reaction: In the presence of a catalyst, 2-chloro-1,1,1,2-tetrafluoropropane obtained from the liquid-phase fluorination reaction is subjected to a gas-phase dehydrochlorination reaction at a temperature of 200℃~450℃ to produce 2,3,3,3-tetrafluoropropene (HFO-1234yf).

[0021] Furthermore, the catalyst in the liquid-phase fluorination reaction is at least one of titanium tetrachloride, tin tetrachloride, antimony pentachloride, and fluorosulfonic acid.

[0022] Furthermore, the catalyst in the dehydrochlorination reaction is at least one of activated carbon, palladium-supported activated carbon, platinum-supported activated carbon, and metal halide-supported activated carbon.

[0023] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0024] The method and route for preparing 2,3,3,3-tetrafluoropropylene according to the present invention uses readily available raw materials, has low cost, and unreacted raw materials can be recycled for further reaction, resulting in low emissions of waste. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] Example 1

[0028] The method for preparing 2,3,3,3-tetrafluoropropylene according to the present invention includes the following steps:

[0029] Step 1: CH2=CH2 + CCl4 → CCl3CH2CH2Cl (HCC-250fb)

[0030] 2 kg of carbon tetrachloride, 20 g of reduced iron powder, and 20 g of tributyl phosphate were added to a 5 L reactor purged with nitrogen. Stirring was started, and the reactor temperature was raised to 100 °C. At the reaction temperature, ethylene was introduced into the reactor at a rate of 80 g / h. Cooling water was circulated through the reactor to remove the heat of reaction. 260 g of ethylene was introduced, and the reaction was terminated after 5 hours. GC analysis showed a conversion rate of 96% (based on ethylene) and a selectivity of 93% for 1,1,1,3-tetrachloropropane.

[0031] Step 2: CCl3CH2CH2Cl → CCl2=CHCH2Cl (HCC-1240za) + HCl

[0032] 200 mL of activated carbon-supported barium chloride catalyst was packed in a fixed-bed reactor and reacted at 280 °C. After purification, 99.9% of 1,1,1,3-tetrachloropropane was passed into the reactor at a rate of 130 g / h to remove hydrogen chloride. The product was washed with alkali and analyzed by GC, which showed that it contained 73.4% 1,1,3-trichloropropene, 24.5% 1,1,1,3-tetrachloropropane, and 2.0% high-boiling chlorocycloalkanes or chlorocycloolefins.

[0033] Step 3: CCl2=CHCH2Cl + Cl2 → CCl3CHClCH2Cl (HCC-240db)

[0034] 100g of purified 99.9% 1,1,3-trichloropropene and 0.013mol Lewis acid catalyst dissolved in carbon tetrachloride were introduced into a reactor, and 48.8g of chlorine gas was introduced at 150℃ to react. The product was washed with alkali and analyzed by GC. The results are shown in Table 1.

[0035] catalyst Reaction temperature / ℃ Conversion rate / selectivity (%) <![CDATA[FeCl3]]> 120 70 / 100 <![CDATA[FeCl3]]> 100 23 / 95.6 <![CDATA[AlCl3]]> 120 65 / 93.7 <![CDATA[CuCl2]]> 120 43 / 89 <![CDATA[CrCl3]]> 120 57 / 95.2 none 150 15 / 30

[0036] Table 1

[0037] Gas-phase reaction: 200 mL of activated carbon-supported ferric chloride catalyst was packed in a fixed-bed reactor. 1,1,3-trichloropropene and Cl2 were mixed at a molar ratio of 1:0.1 to 1:1.1. After purification, 99.9% 1,1,3-trichloropropene was preheated in a preheater at a rate of 100 g / h, and chlorine gas was introduced into the reactor at a rate of 48.8 g / h. The chlorination reaction was carried out at a temperature of 200℃ to 300℃. The product was washed with alkali and analyzed by GC. The results are shown in Table 2.

[0038] Reaction temperature / ℃ Conversion rate / selectivity (%) 60 70 / 95 60 68 / 95.6 80 86 / 93 80 89 / 90 100 96 / 80 100 95 / 84

[0039] Table 2

[0040] Step 4: CCl3CHClCH2Cl + 3HF → CF3CCl=CH2 (HCFO-1233xf) + 3HCl

[0041] 200 mL of chromium oxide was placed in a fixed-bed reactor, and HF was passed through to completely fluorinate the catalyst. 1,1,1,2,3-pentachloropropane and HF were mixed at a molar ratio of 1:8. After purification, 99.9% of the 1,1,1,2,3-pentachloropropane was introduced into a preheater at a rate of 107 g / h for preheating, and then introduced into the reactor along with HF. The fluorination reaction was carried out at 280 °C. The product was washed with alkali, and GC analysis revealed that it contained 53.2% 2-chloro-3,3,3-trifluoropropene, 0.8% 2,3,3,3-tetrafluoropropene, 44.3% 1,1,1-trifluoro-2,3-dichloropropane, 1.2% 1-chloro-3,3,3-trifluoropropene, and 0.3% 1,1,1,2,3-pentachloropropane. 1,1,1-trifluoro-2,3-dichloropropane and 1,1,1,2,3-pentafluoropropane were returned to the reactor in step 4 to continue the reaction and yield 2-chloro-3,3,3-trifluoropropene.

[0042] The reaction temperature in step 5 is 20°C to 80°C higher than that in step 4.

[0043] 200 mL of chromium oxide was placed in a fixed-bed reactor, and HF was passed through to completely fluorinate the catalyst. 2-Chloro-3,3,3-trifluoropropene and HF were mixed at a molar ratio of 1:5. The purified 2-chloro-3,3,3-trifluoropropene was preheated in a preheater at a rate of 97.1 g / h before being introduced into the reactor with HF. The fluorination reaction was carried out at 320 °C. The product was washed with alkali and analyzed by GC, revealing that it contained 0.1% 2-chloro-3,3,3-trifluoropropene, 84.3% 2,3,3,3,-tetrafluoropropene, 15.2% 1,1,1,2,2-pentafluoropropane, and 0.3% 1,1,1,2,3-pentafluoropropane. 1,1,1,2,2-pentafluoropropane and 1,1,1,2,3-pentafluoropropane were separated from unconverted 2-chloro-3,3,3-trifluoropropene and returned to the reactor to continue the reaction to obtain 2,3,3,3-tetrafluoropropene.

[0044] Example 2 (Alternative Route)

[0045] Steps 1 to 4: Same as in Example 1, to obtain intermediate HCFO-1233xf.

[0046] The alternative route includes the following steps in sequence:

[0047] Liquid-phase fluorination reaction: CF3CCl=CH2 + HF → CF3CClFCH3 (HFC-244bb)

[0048] Titanium tetrachloride catalyst was added to the reactor, and hydrofluoric acid was introduced for reaction. The reaction temperature was raised to 100℃, and 2-chloro-3,3,3-trifluoropropene and hydrofluoric acid were introduced into the reactor at a molar ratio of 1:1. The discharge pipe valve was adjusted, and the gaseous material passed through a water scrubber and an alkali scrubber. A GC sample was taken from the outlet of the alkali scrubber and tested. It contained 0.3% 2-chloro-3,3,3-trifluoropropene, 97.3% 2-chloro-1,1,1,2-tetrafluoropropane, and 1.5% 1,1,1,2,2-pentafluoropropane.

[0049] Dehydrochlorination reaction: CF3CClFCH3 → CF3CF=CH2 (HFO-1234yf) + HCl

[0050] 200 mL of barium chloride-supported activated carbon was placed in a fixed-bed reactor. Purified 2-chloro-1,1,1,2-tetrafluoropropane was preheated in a preheater at a flow rate of 50 g / h before entering the reactor, where it underwent dehydrochlorination at 280 °C. The product was then passed through a water scrubber and an alkali scrubber. A GC sample was taken from the alkali scrubber outlet; the sample contained 80.3% 2,3,3,3-tetrafluoropropene and 19.2% 2-chloro-1,1,1,2-tetrafluoropropane.

[0051] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to achieve substantially the same technical effect are all covered within the protection scope of the present invention.

Claims

1. A method for preparing 2,3,3,3-tetrafluoropropylene, characterized in that... Includes the following steps: Step 1: In the presence of a catalyst containing reduced iron powder and a co-catalyst, carbon tetrachloride is reacted with ethylene at a reaction temperature of 80℃~150℃, a reaction pressure of 0~3MPa, and a reaction time of 2h~10h. 1,1,1,3-Tetrachloropropane is obtained by separation and purification. Step 2: In the presence of a catalyst containing metal chlorides supported on activated carbon, the 1,1,1,3-tetrachloropropane obtained in Step 1 is subjected to a dehydrochlorination reaction at a temperature of 200°C to 400°C to produce 1,1,3-trichloropropene. Step 3: In a solvent, at a temperature of 30℃~200℃, in the presence of a metal halide catalyst, 1,1,3-trichloropropene obtained in Step 2 is subjected to a liquid-phase or gas-phase chlorination reaction with chlorine to obtain 1,1,1,2,3-pentachloropropane. Step 4: In the presence of a supported or unsupported chromium oxide catalyst, the 1,1,1,2,3-pentachloropropane obtained in Step 3 is subjected to a gas-phase fluorination reaction with hydrogen fluoride at a temperature of 200℃~400℃ to produce 2-chloro-3,3,3-trifluoropropene. Step 5: In the presence of a supported or unsupported chromium oxide catalyst, the 2-chloro-3,3,3-trifluoropropene obtained in Step 4 is subjected to a gas-phase fluorination reaction with hydrogen fluoride at a temperature of 200℃~450℃ to generate 2,3,3,3-tetrafluoropropene.

2. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: The cocatalyst in step 1 includes phosphate esters or phosphites, and the cocatalyst is at least one of tributyl phosphate, dibutyl phosphate, triethyl phosphate, trimethyl phosphite, and tributyl phosphite.

3. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: The metal chloride in step 2 is at least one of ferric chloride, barium chloride, and copper chloride.

4. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: When a liquid-phase reaction is used in step 3, the metal halide catalyst is at least one of ferric chloride, chromium chloride, aluminum chloride, and copper chloride, the solvent is at least one of carbon tetrachloride, chloroform, and dichloromethane, and the reaction temperature is 30℃~150℃.

5. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: When a gas-phase reaction is used in step 3, the metal halide catalyst is ferric chloride, chromium chloride, aluminum chloride, and copper chloride supported on activated carbon, and the reaction temperature is 50℃~200℃.

6. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: The load in step 4 and / or step 5 is at least one of magnesium, zinc, aluminum, nickel and cobalt.

7. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that: The reaction temperature in step 5 is 20°C to 80°C higher than that in step 4.

8. The method for preparing 2,3,3,3-tetrafluoropropylene according to any one of claims 1 to 7, characterized in that: The method includes an alternative route for converting the 2-chloro-3,3,3-trifluoropropene generated in step 4 into 2,3,3,3-tetrafluoropropene, the alternative route comprising the following steps in sequence: Liquid-phase fluorination reaction: In the presence of a catalyst, at a temperature of 30℃~150℃, 2-chloro-3,3,3-trifluoropropene obtained in step 4 is reacted with hydrogen fluoride to generate 2-chloro-1,1,1,2-tetrafluoropropane. Dehydrochlorination reaction: In the presence of a catalyst, 2-chloro-1,1,1,2-tetrafluoropropane obtained from the liquid-phase fluorination reaction is subjected to a gas-phase dehydrochlorination reaction at a temperature of 200℃~450℃ to produce 2,3,3,3-tetrafluoropropene.

9. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 8, characterized in that: The catalyst in the liquid-phase fluorination reaction is at least one of titanium tetrachloride, tin tetrachloride, antimony pentachloride, and fluorosulfonic acid.

10. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 8, characterized in that: The catalyst in the dehydrochlorination reaction is at least one of activated carbon, palladium-supported activated carbon, platinum-supported activated carbon, and metal halide-supported activated carbon.