Process for synthesizing 2,3,3,3-tetrafluoropropene by gas-phase fluorination

Abstract

The present invention discloses a method for synthesizing 2,3,3,3-tetrafluoropropene by gas-phase fluorination. First, in the presence of a chromium-free environmentally friendly fluorination catalyst, a gas phase contacts with a fluorinating agent and a halogenating agent to prepare halogenated trifluoropropene, and the halogenated trifluoropropene reacts with the fluorinating agent in the presence of the chromium-free environmentally friendly fluorination catalyst to prepare 2,3,3,3-tetrafluoropropene. The raw materials of the present invention are cheap and easily available, the synthesis steps are short, the selectivity of the target product is high, the catalyst does not contain chromium, and it is low-carbon and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing 2,3,3,3-tetrafluoropropene by gas-phase catalytic fluorination. Background Art

[0002] 2,3,3,3-Tetrafluoropropene, abbreviated as HFO-1234yf, has an ozone depletion potential (ODP) of 0 and a global warming potential (GWP) of less than 1, which is less than one-thousandth of the currently most widely used hydrofluorocarbon product, 1,1,1,2-tetrafluoroethane (HFC-134a, GWP is 1430). However, its physical properties are similar to those of HFC-134a and can directly replace the latter in existing refrigeration systems. It is a new type of environmentally friendly refrigerant with the most promising development prospects and has been applied in large commercial refrigeration and vehicle refrigeration.

[0003] So far, among the numerous known synthesis methods of HFO-1234yf, the synthesis process routes using chloropropane as the raw material include the following. US Patent No. US8450537B2 discloses a raw material composed of chemical formulas CX3CH2CH2X, CX3CH=CH2 or CH2XCH=CX2 (where each X is independently selected from the group consisting of F and Cl), which reacts with HF and Cl2 (HF / raw material is in a stoichiometric ratio, Cl2 / raw material is 2) under the action of a chromium-containing catalyst to generate a mixture of 2,3,3,3-tetrafluoropropene, 1,1,1,2,2-pentafluoropropane, 2-chloro-3,3,3-trifluoropropene, etc. Chinese Patent No. CN101979364B discloses a method for preparing 2,3,3,3-tetrafluoropropene from 3,3,3-trifluoropropene through four steps of photochlorination, liquid-phase dehydrochlorination, liquid-phase fluorination, and liquid-phase dehydrochlorination. Chinese Patent No. CN103946192B discloses a method using 1,1,2,3-tetrachloropropene as the raw material. First, it is fluorinated in the gas phase or liquid phase to prepare 2-chloro-3,3,3-trifluoropropene, and then it reacts with HF under gas-phase reaction conditions in the presence of a chromium-containing catalyst to synthesize 2,3,3,3-tetrafluoropropene. Chinese Patent No. CN102099319B discloses a method using 1,1,1,3-tetrachloropropane as the starting material. First, it is fluorinated to convert it into 3,3,3-trifluoropropene, then chlorinated to convert it into 1,1,1-trifluoro-2,3-dichloropropane, and then dehydrochlorinated to prepare 2-chloro-3,3,3-trifluoropropene. Finally, it is synthesized into 2,3,3,3-tetrafluoropropene through liquid-phase fluorination and high-temperature dehydrochlorination.

[0004] Although the above-reported synthetic routes have achieved certain effects in the field of HFO-1234yf synthesis technology, they generally suffer from problems such as long reaction steps, poor selectivity, low efficiency, high energy consumption, and poor economy. Moreover, the catalysts used in gas-phase fluorination reactions all have chromium as the core component. However, as a heavy metal element, a large amount of chromium emissions will cause serious pollution to the ecological environment; especially hexavalent chromium is a highly toxic substance that poses a great threat to the health of animals and humans. Based on this, there is an urgent need to develop a new low-carbon and environmentally friendly synthetic route for HFO-1234yf and use high-performance chromium-free fluorination catalysts. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a method for gas-phase fluorination synthesis of 2,3,3,3-tetrafluoropropene to solve problems such as long traditional technical routes, poor selectivity, complex separation, low efficiency, and great environmental harm of catalysts containing heavy metal chromium; this method has cheap and easily available raw materials, short synthesis steps, few reaction steps, high selectivity of the target product, chromium-free catalyst, and is low-carbon and environmentally friendly.

[0006] To solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0007] A method for gas-phase fluorination synthesis of 2,3,3,3-tetrafluoropropene, which uses 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene as raw materials. First, in the presence of a chromium-free environmentally friendly fluorination catalyst, it is contacted with a fluorinating agent and a halogenating agent in the gas phase to prepare halogenated trifluoropropene, and the halogenated trifluoropropene reacts with a fluorinating agent in the presence of a chromium-free environmentally friendly fluorination catalyst to prepare 2,3,3,3-tetrafluoropropene.

[0008] The present invention also includes the following technical features:

[0009] Specifically, it includes the following steps:

[0010] Step 1, in a first reactor, in the presence of a first fluorination catalyst, at 150 - 300 °C and 0.1 - 1.0 MPa, 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene is contacted with a fluorinating agent and a halogenating agent to be converted into halogenated trifluoropropene;

[0011] Step 2, in a second reactor, in the presence of a second fluorination catalyst, at 300 - 450 °C and 0.1 - 1.0 MPa, the halogenated trifluoropropene obtained in Step 1 is contacted with a fluorinating agent to be converted into 2,3,3,3-tetrafluoropropene.

[0012] Specifically, in the step 1, the first fluorination catalyst is a chromium-free and environmentally friendly fluoride catalyst, including FeOxFy (2x + y = 3) and magnesium fluoride; the fluorinating agent is anhydrous hydrogen fluoride; the halogenating agent is chlorine or bromine; the chemical formula of the halogenated trifluoropropene is CF3CX=CH2, where X = Cl or Br.

[0013] Specifically, in the step 1, the molar ratio of 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene to the fluorinating agent and the halogenating agent is 1 / 10 to 50 / 1 to 2.

[0014] Specifically, in the step 1, the first fluorination catalyst further includes a promoter, and the promoter includes lanthanum, copper, nickel, and zirconium; the proportions of the promoter, FeOxFy, and magnesium fluoride in the total weight of the first fluorination catalyst are 1% to 5%, 10% to 20%, and 78% to 88% respectively.

[0015] Specifically, in the step 2, the second fluorination catalyst is a chromium-free and environmentally friendly fluoride catalyst, including FeOxFy (2x + y = 3), aluminum fluoride or magnesium fluoride; the fluorinating agent is anhydrous hydrogen fluoride.

[0016] Specifically, in the step 2, the molar ratio of the halogenated trifluoropropene to the fluorinating agent is 1 / 10 to 50.

[0017] Specifically, in the step 2, the second fluorination catalyst further contains a promoter, and the promoter includes titanium, tin, gallium, and cobalt; the proportions of the promoter, FeOxFy, and aluminum fluoride or magnesium fluoride in the total weight of the second fluorination catalyst are 1% to 5%, 10% to 20%, and 77% to 89% respectively.

[0018] Specifically, the specific surface area of the magnesium fluoride and aluminum fluoride is greater than 100 m 2 / g, the pore size distribution is 5 - 15 nm, and the thermal stability is greater than 400 °C.

[0019] Specifically, at least 80% of 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene in the first reactor is converted into halogenated trifluoropropene, and at least 40% of the halogenated trifluoropropene in the second reactor is converted into 2,3,3,3-tetrafluoropropene.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] ① Compared with traditional preparation methods, the present invention provides a new method for preparing HFO-1234yf with cheap and easily available raw materials, short reaction steps, simple separation, high selectivity, and environmental friendliness; ② The present invention provides a highly active and highly selective fluorination catalyst that is free of chromium and other heavy metals and is environmentally friendly, with FeOxFy (2x + y = 3) as the active center; ③ The composite catalyst of FeOxFy (2x + y = 3) and magnesium fluoride used in the present invention can make 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene contact with a fluorinating agent and a halogenating agent to generate halogenated trifluoropropene with high activity and high selectivity; ④ The composite catalyst of FeOxFy (2x + y = 3) and aluminum fluoride used in the present invention can make halogenated trifluoropropene contact with a fluorinating agent to generate 2,3,3,3-tetrafluoropropene with high activity and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the preparation process of 2,3,3,3-tetrafluoropropene of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention provides a method for synthesizing 2,3,3,3-tetrafluoropropene by gas-phase fluorination. Using 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene as raw materials, first, in the presence of a chromium-free and environmentally friendly fluorination catalyst, it is contacted with a fluorinating agent and a halogenating agent in the gas phase to prepare halogenated trifluoropropene. In the second step, the halogenated trifluoropropene reacts with a fluorinating agent in the presence of a chromium-free and environmentally friendly fluorination catalyst to prepare 2,3,3,3-tetrafluoropropene; it includes the following steps:

[0024] Step 1, in a first reactor, in the presence of a first fluorination catalyst, at 150 - 300 °C and 0.1 - 1.0 MPa, 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene is contacted with a fluorinating agent and a halogenating agent to be converted into halogenated trifluoropropene;

[0025] Specifically, in Step 1, the first fluorination catalyst is a chromium-free and environmentally friendly fluoride catalyst, including FeOxFy (2x + y = 3) and magnesium fluoride; the fluorinating agent is anhydrous hydrogen fluoride; the halogenating agent is chlorine or bromine; the chemical formula of the halogenated trifluoropropene is CF3CX = CH2, where X = Cl or Br; the molar ratio of 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene to the fluorinating agent and the halogenating agent is 1 / 10 - 50 / 1 - 2;

[0026] More specifically, the first fluorination catalyst further includes a promoter, and the promoter includes lanthanum, copper, nickel, and zirconium; the proportions of the promoter, FeOxFy, and magnesium fluoride in the total weight of the first fluorination catalyst are 1% - 5%, 10% - 20%, and 78% - 88% respectively;

[0027] Step 2: In the second reactor, in the presence of a second fluorination catalyst, at 300 - 450 °C and 0.1 - 1.0 MPa, contact the halogenated trifluoropropene obtained in Step 1 with a fluorinating agent to convert it into 2,3,3,3 - tetrafluoropropene;

[0028] Specifically, in Step 2, the second fluorination catalyst is a chromium - free environmentally friendly fluoride catalyst, including FeOxFy (2x + y = 3), aluminum fluoride, or magnesium fluoride; the fluorinating agent is anhydrous hydrogen fluoride; the molar ratio of the halogenated trifluoropropene to the fluorinating agent is 1 / 10 - 50;

[0029] More specifically, the second fluorination catalyst further contains promoters, and the promoters include titanium, tin, gallium, and cobalt; the proportions of the promoters, FeOxFy, aluminum fluoride, or magnesium fluoride in the total weight of the second fluorination catalyst are 1% - 5%, 10% - 20%, and 77% - 89% respectively;

[0030] The specific surface area of magnesium fluoride and aluminum fluoride is greater than 100 m 2 / g, the pore size distribution is 5 - 15 nm, and the thermal stability is greater than 400 °C.

[0031] At least 80% of 1,1,1,3 - tetrachloropropane or 3,3,3 - trichloropropene in the first reactor is converted into halogenated trifluoropropene, and at least 40% of the halogenated trifluoropropene in the second reactor is converted into 2,3,3,3 - tetrafluoropropene.

[0032] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0033] Example 1:

[0034] This example provides a method for gas - phase fluorination synthesis of 2,3,3,3 - tetrafluoropropene, including the following steps:

[0035] Step 1: Prepare 2 - bromo - 3,3,3 - trifluoropropene from 1,1,1,3 - tetrachloropropane:

[0036] Transfer the first fluorination catalyst into a fixed-bed tubular reactor. After heating to the set temperature and drying for 2 h, introduce hydrogen fluoride and bromine, and then introduce 1,1,1,3-tetrachloropropane. The contact time is 8 seconds. After running for 12 h, the product is washed with water and alkali to absorb hydrogen fluoride, hydrogen chloride and hydrogen bromide, and then analyzed by gas chromatography. The conversion rate of 1,1,1,3-tetrachloropropane and the selectivity of the target product 2-bromo-3,3,3-trifluoropropene are calculated by the area normalization method. Specifically, the first fluorination catalyst in this example includes FeOxFy (2x + y = 3), magnesium fluoride and additives. The additives include lanthanum, copper, nickel and zirconium. Among them, 30 mL of the composition of FeOxFy (2x + y = 3) and magnesium fluoride is measured. The specific surface area of magnesium fluoride after calcination at 400 °C is 108 m 2 / g, and the pore diameter is 15 nm.

[0037] The components and ratios of the first fluorination catalyst, reaction temperature, reaction pressure, etc. in Step 1, and the reaction results are as follows in the table:

[0038] Table 1 Reaction results for preparing halogenated trifluoropropene

[0039]

[0040]

[0041] Step 2, prepare 2,3,3,3-tetrafluoropropene from 2-bromo-3,3,3-trifluoropropene:

[0042] Take the second fluorination catalyst and transfer it into a fixed-bed tubular reactor. After heating to the set temperature and drying for 2 h, introduce hydrogen fluoride, and then introduce 2-bromo-3,3,3-trifluoropropene. The contact time is 12 seconds. After running for 12 h, the product is washed with water and alkali to absorb hydrogen fluoride and hydrogen bromide, and then analyzed by gas chromatography. The conversion rate of 2-bromo-3,3,3-trifluoropropene and the selectivity of the target product 2,3,3,3-tetrafluoropropene are calculated by the area normalization method. Specifically, the second fluorination catalyst in this example includes FeOxFy (2x + y = 3), aluminum fluoride or magnesium fluoride and additives. The additives include titanium, tin, gallium and cobalt. Among them, 30 mL of the composition of FeOxFy (2x + y = 3) and aluminum fluoride or magnesium fluoride is used as the catalyst. The specific surface area of aluminum fluoride after calcination at 400 °C is 168 m 2 / g, and the pore diameter is 8 nm.

[0043] The components and ratios of the second fluorination catalyst, reaction temperature, reaction pressure, etc. in Step 2, and the reaction results are as follows in the table:

[0044] Table 2 Reaction results for preparing 2,3,3,3-tetrafluoropropene from halogenated trifluoropropene

[0045]

[0046] Example 2:

[0047] This example provides a method for synthesizing 2,3,3,3-tetrafluoropropene by gas-phase fluorination, which includes the following steps:

[0048] Step 1: Prepare 2-chloro-3,3,3-trifluoropropene from 3,3,3-trichloropropene:

[0049] Use the same first fluorination catalyst as in Example 1. After calcination at 400 °C, the specific surface area of magnesium fluoride is 118 m 2 / g, and the pore size is 10 nm. Apply it to the gas-phase reaction of 3,3,3-trichloropropene with hydrogen fluoride and chlorine to synthesize 2-chloro-3,3,3-trifluoropropene and run for 12 h. The components and ratios of the first fluorination catalyst, reaction temperature, reaction pressure, etc. in Step 1, as well as the reaction results, are shown in the following table:

[0050] Table 3 Reaction results for preparing halogenated trifluoropropene

[0051]

[0052] Step 2: Prepare 2,3,3,3-tetrafluoropropene from 2-chloro-3,3,3-trifluoropropene

[0053] Use the same second fluorination catalyst as in Example 1. After calcination at 400 °C, the specific surface area of aluminum fluoride is 188 m 2 / g, and the pore size is 5 nm. Apply it to the gas-phase reaction of 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride to synthesize 2,3,3,3-tetrafluoropropene and run for 12 h. The components and ratios of the second fluorination catalyst, reaction temperature, reaction pressure, etc. in Step 2, as well as the reaction results, are shown in the following table:

[0054] Table 4 Reaction results for preparing 2,3,3,3-tetrafluoropropene from halogenated trifluoropropene

[0055]

Claims

1. A method for synthesizing 2,3,3,3 - tetrafluoropropene by gas - phase fluorination, characterized in that, This method uses 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene as raw materials. First, in the presence of a chromium-free environmentally friendly fluorination catalyst, it contacts with a fluorinating agent and a halogenating agent in the gas phase to prepare halogenated trifluoropropene. Then, the halogenated trifluoropropene reacts with the fluorinating agent in the presence of a chromium-free environmentally friendly fluorination catalyst to prepare 2,3,3,3-tetrafluoropropene; It includes the following steps: Step 1, in the first reactor, in the presence of the first fluorination catalyst, at 150~300 °C and 0.1~1.0 MPa, contact 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene with the fluorinating agent and the halogenating agent to convert it into halogenated trifluoropropene; Step 2, in the second reactor, in the presence of the second fluorination catalyst, at 300~450 °C and 0.1~1.0 MPa, contact the halogenated trifluoropropene obtained in Step 1 with the fluorinating agent to convert it into 2,3,3,3-tetrafluoropropene; In Step 1, the first fluorination catalyst is a chromium-free environmentally friendly fluoride catalyst, including FeOxFy and magnesium fluoride, where 2x + y = 3; the fluorinating agent is anhydrous hydrogen fluoride; the halogenating agent is chlorine or bromine; the chemical formula of the halogenated trifluoropropene is CF3CX=CH2, where X = Cl or Br; In Step 1, the first fluorination catalyst also includes promoters, and the promoters include lanthanum, copper, nickel, and zirconium; the proportions of the promoters, FeOxFy, and magnesium fluoride in the total weight of the first fluorination catalyst are 1%~5%, 10%~20%, and 78%~88% respectively; In Step 2, the second fluorination catalyst is a chromium-free environmentally friendly fluoride catalyst, including FeOxFy, aluminum fluoride, or magnesium fluoride, where 2x + y = 3; the fluorinating agent is anhydrous hydrogen fluoride; In Step 2, the second fluorination catalyst also contains promoters, and the promoters include titanium, tin, gallium, and cobalt; the proportions of the promoters, FeOxFy, and aluminum fluoride or magnesium fluoride in the total weight of the second fluorination catalyst are 1%~5%, 10%~20%, and 77%~89% respectively.

2. The method for synthesizing 2,3,3,3 - tetrafluoropropene by gas - phase fluorination according to claim 1, characterized in that, In Step 1, the molar ratio of 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene to the fluorinating agent and the halogenating agent is 1 / 10~50 / 1~2.

3. The method for synthesizing 2,3,3,3 - tetrafluoropropene by gas - phase fluorination according to claim 1, characterized in that, In Step 2, the molar ratio of the halogenated trifluoropropene to the fluorinating agent is 1 / 10~50.

4. The method for synthesizing 2,3,3,3 - tetrafluoropropene by gas - phase fluorination according to claim 1, characterized in that, The specific surface area of the magnesium fluoride and aluminum fluoride is greater than 100 m 2 / g, the pore size distribution is 5 - 15 nm, and the thermal stability is greater than 400 °C.

5. The method for synthesizing 2,3,3,3 - tetrafluoropropene by gas - phase fluorination according to claim 1, characterized in that, At least 80% of 1,1,1,3-tetrachloropropane or 3,3,3-trichloropropene in the first reactor is converted into halogenated trifluoropropene, and at least 40% of the halogenated trifluoropropene in the second reactor is converted into 2,3,3,3-tetrafluoropropene.

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