Fluorination catalyst and method for preparing 2, 3, 3, 3-tetrafluoropropene

Abstract

The invention relates to a fluorination catalyst and a method for preparing 2, 3, 3, 3-tetrafluoropropene. The fluorination catalyst is prepared by the following steps: (1) preparing a catalyst precursor; (2) activating the catalyst precursor; and (3) fluorinating the catalyst precursor. The catalyst provided by the invention has high stability, and can be used for preparing 2, 3, 3, 3-tetrafluoropropene with high conversion rate and high selectivity through a simple process.

Description

Technical Field

[0001] The present invention relates to the field of chemical catalyst synthesis and application. Specifically, the present invention relates to a fluorination catalyst and a method for preparing 2,3,3,3-tetrafluoropropene. Background Art

[0002] 2,3,3,3-Tetrafluoropropene (HFO-1234yf) is a new type of refrigerant mainly used in automotive air conditioning systems. The atmospheric decomposition products of HFO-1234yf are the same as those of the traditional second-generation refrigerant 1,1,1,2-tetrafluoroethane (HFC-134a), but its physical and chemical properties are significantly better than those of HFC-134a. For example, HFO-1234yf has a lower global warming potential (GWP) (1300 vs. 4), significantly reducing the impact on climate change; its ozone depletion potential (ODP) is zero and it will not damage the ozone layer; it has a low boiling point; a large saturated vapor pressure at normal temperature, resulting in good refrigeration effect; and good miscibility. It is considered an economical solution for directly replacing HFC-134a and has thus become a research hotspot in the fluorochemical industry worldwide.

[0003] Chinese Patent CN 104069878B discloses a catalyst for the cracking of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to prepare HFO-1234yf and its preparation method. The catalyst is a mixture of Pd / LaF3 / A1F3 catalyst and Ag-Ni-Cr2O3 catalyst. In the Pd / LaF3 / AlF3 catalyst, the loading amount of LaF3 is 5% of the mass of AlF3, and the loading amount of Pd is 0.1% of the mass of AlF3. In the Ag-Ni-Cr2O3 catalyst, the molar ratio of Ag, Ni, and Cr is 0.5:4:100. The mass ratio of the Pd / LaF3 / AlF3 catalyst to the Ag-Ni-Cr2O3 catalyst is 1-4:4-1. This catalyst achieves the purpose of directly preparing HFO-1234yf by cracking HFC-245fa, with a conversion rate of about 99.9% and a selectivity of about 15-25%. However, the yield of its by-product 1,3,3,3-tetrafluoropropene (HFO-1234ze) is still relatively high.

[0004] Chinese Patent CN 104710274B discloses a process for co-producing HFO-1234ze and HFO-1234yf using 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) as the starting material and a chromium-based fluorination catalyst. The catalyst is one, two, or more than two mixtures of chromium, chromium oxides, cubic Cr2O3, and chromium fluoride oxides, and the carrier is Al2O3, AIF3, and fluorinated alumina. The reaction temperature is 300-450 °C, the reaction pressure is 0.3-0.4 MPa, the conversion rate of the target product HCFO-1233xf can reach more than 60%, and the selectivity can reach more than 40%.

[0005] Chinese Patent CN 101535228B discloses a method for preparing HFO-1234yf by catalytic isomerization using HFO-1234ze as the starting material, including reacting at 200-500 °C under the action of a catalyst Cr2O x F y (x + y / 2 = 3) for 15-300 min to obtain HFO-1234yf, and the conversion rate of the raw material is 33.8%. However, the raw material price of this method is high and it is not suitable for industrial production.

[0006] Therefore, there is still a need in the art for a method for preparing 2,3,3,3-tetrafluoropropene with a simple process, high conversion rate, and high selectivity. Summary of the Invention

[0007] The present invention aims to provide a method for preparing 2,3,3,3-tetrafluoropropene with a simple process, high conversion rate, and high selectivity.

[0008] The inventors found that by preparing a specific fluorination catalyst and using 2-chloro-3,3,3-trifluoropropene as the starting material under certain process conditions, the advantages of a simple process, high conversion rate, and high selectivity can be achieved, thereby effectively solving or at least alleviating one or more problems existing in the prior art.

[0009] Therefore, according to one aspect of the present invention, there is provided a fluorination catalyst, characterized in that it is prepared by the following steps: 1) Preparation of catalyst precursor: Impregnate and load a water-soluble trivalent chromium salt and a water-soluble silicate on a catalyst carrier according to a Cr:Si mass ratio of 100:0.5-2, dry and calcine the carrier to obtain a catalyst precursor, or Co-precipitate a water-soluble trivalent chromium salt and a water-soluble silicate according to a Cr:Si mass ratio of 100:0.5-2, dry and calcine the precipitate, mix it with a polyvinyl alcohol binder and graphite, and obtain a catalyst precursor after tableting. 2) Activation of the catalyst precursor: Activate the catalyst precursor in an atmosphere of a carrier gas to obtain an activated catalyst precursor; and 3) Fluorination of the catalyst precursor: Fluorinate the activated catalyst precursor with hydrogen fluoride to obtain a fluorinated catalyst.

[0010] According to another aspect of the present invention, there is provided a method for preparing 2,3,3,3-tetrafluoropropene, which is characterized by comprising: reacting 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride in the presence of the above-mentioned fluorinated catalyst and a carrier gas to obtain 2,3,3,3-tetrafluoropropene, wherein the carrier gas is an inert gas, and the molar ratio of the inert gas: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene is 10:(50 - 200):10, the reaction temperature is 300 - 500 °C, and the space velocity is 500 - 2000 h -1 .

[0011] The inventors have found that: compared with the prior art, the present invention has the following beneficial effects: 1. The preparation method of 2,3,3,3-tetrafluoropropene of the present invention has a high conversion rate (up to 30%), a relatively high selectivity for 2-chloro-3,3,3-trifluoropropene (up to 76%), and high catalyst stability, which can stably reach 1000 h; 2. By adding a silicon-containing substance to the chromium-based catalyst, volatile substance SiF4 is generated during the activation of the catalyst, resulting in the catalyst having a porous nature, increasing the surface active centers of the catalyst, and thus enhancing the catalytic ability of the catalyst; 3. The raw materials used in the present invention have low costs, the process is simple, and it is easy to industrialize. Specific Embodiments

[0012] In order to enable those skilled in the art to further understand the present invention, the specific implementation embodiments of the present invention will be described in detail below. However, it should be understood that the described implementation embodiments of the present invention are merely exemplary, and the present invention is not limited to these implementation embodiments.

[0013] Fluorination catalyst According to one aspect of the present invention, there is provided a fluorinated catalyst, which is characterized by being prepared through the following steps: 1) Preparation of the catalyst precursor: Impregnate and load a water-soluble trivalent chromium salt and a water-soluble silicate on a catalyst carrier according to a Cr:Si mass ratio of 100:0.5 - 2, dry and calcine the carrier to obtain a catalyst precursor, or Carry out coprecipitation of a water-soluble trivalent chromium salt and a water-soluble silicate according to a Cr:Si mass ratio of 100:0.5 - 2, dry and calcine the precipitate, mix it with a polyvinyl alcohol binder and graphite, and obtain a catalyst precursor after tabletting and forming; 2) Activation of the catalyst precursor: Activate the catalyst precursor in an atmosphere of a carrier gas to obtain an activated catalyst precursor; and 3) Fluorination of the catalyst precursor: Fluorinate the activated catalyst precursor with hydrogen fluoride to obtain a fluorinated catalyst.

[0014] The water-soluble trivalent chromium salt described herein refers to a trivalent chromium salt having a solubility in water of not less than 10 g / 100 ml of water.

[0015] Preferably, in step 1), the water-soluble trivalent chromium salt is selected from chromium nitrate, chromium chloride, chromium sulfate, and chromium acetate.

[0016] More preferably, in step 1), the water-soluble trivalent chromium salt is chromium nitrate.

[0017] Preferably, in step 1), the water-soluble silicate is selected from potassium silicate, sodium silicate, lithium silicate, and potassium aluminosilicate.

[0018] More preferably, in step 1), the water-soluble silicate is potassium silicate.

[0019] In step 1), the coprecipitation is carried out in an alkaline solution, and the alkaline solution can be selected from the solution systems commonly used in the coprecipitation process. Preferably, the alkaline solution is selected from hydroxide solutions of alkali metals, hydroxide solutions of alkaline earth metals, and ammonia water solutions. More preferably, the alkaline solution is an ammonia water solution. In some embodiments, for example, the water-soluble silicate can be dissolved in ammonia water to obtain an ammonia water solution of potassium silicate for coprecipitation with an aqueous solution of a trivalent chromium salt.

[0020] Preferably, in step 1), the mass ratio of Cr:Si is 100:0.5 - 1.

[0021] In step 1), the drying can be carried out in any suitable manner.

[0022] Preferably, the drying is carried out by maintaining at 100 - 150 °C for 1 - 4 h.

[0023] In step 1), the drying can be carried out in a suitable device, such as in an oven.

[0024] In step 1), the calcination can be carried out in a suitable device, such as in a muffle furnace.

[0025] In step 1), the calcination can be carried out in an inert gas (such as nitrogen, helium, argon, or a mixture thereof, preferably nitrogen) atmosphere.

[0026] Preferably, calcine at 300 - 500 °C for 4 - 8 h in a nitrogen atmosphere.

[0027] More preferably, it is calcined at 350 - 370 °C for 4 - 6 h under a nitrogen atmosphere.

[0028] In some embodiments, step 1) is carried out through the following steps a - d: a. Prepare an aqueous solution of a water - soluble trivalent chromium salt and an aqueous solution of water - soluble potassium silicate respectively; b. Apply the aqueous solution of the trivalent chromium salt onto the catalyst support for impregnation, and dry it after 3 - 5 h; c. Apply the aqueous solution of potassium silicate onto the support dried in step b for impregnation, and dry it after 3 - 5 h; and d. Under an inert gas atmosphere, calcine the support dried in step c at 300 - 500 °C for 4 - 8 h to obtain a catalyst precursor.

[0029] Preferably, the catalyst support is selected from magnesium oxide, aluminum oxide, silicon oxide, and activated carbon.

[0030] More preferably, the catalyst support is selected from activated carbon.

[0031] Preferably, the mass fraction of the catalyst support is preferably 85 - 90% of the total mass of the catalyst precursor.

[0032] In some embodiments, step 1) is carried out through the following steps a' - d': a'. Prepare an aqueous solution of a water - soluble trivalent chromium salt and an aqueous ammonia solution of water - soluble potassium silicate respectively; b'. Add the two solutions simultaneously to deionized water for coprecipitation. After the precipitation is complete, filter and collect the precipitate, and dry the precipitate; c'. Under an inert gas atmosphere, calcine the dried product at 300 - 500 °C for 4 - 8 h; and d'. Mix the calcined product with polyvinyl alcohol binder and graphite, and obtain a catalyst precursor after tabletting.

[0033] In some embodiments, the aqueous solution of the water - soluble trivalent chromium salt and the aqueous ammonia solution of the water - soluble potassium silicate can be prepared according to a Cr:OH⁻ molar ratio approximately equal to 1:3, and the pH of the solution is continuously monitored during the coprecipitation process. When the precipitation is complete, the pH is in the range of 7 - 8.

[0034] The inventors of the present invention have found that when polyvinyl alcohol is used as the binder for preparing the catalyst precursor by the above coprecipitation method, it provides appropriate mechanical strength of the catalyst to ensure high stability and catalytic activity of the catalyst during the subsequent catalytic process, and its mass fraction is preferably in the range of 5-20% of the total mass of the catalyst precursor. Unexpectedly, it is further found that polyvinyl alcohol with a mass fraction of 10-15% of the total mass of the catalyst precursor provides better mechanical strength of the catalyst when used as the binder. In particular, polyvinyl alcohol with a mass fraction of 10-12% of the total mass of the catalyst precursor provides significantly better mechanical strength of the catalyst when used as the binder.

[0035] Preferably, the mass fraction of the graphite is 1-5% of the total mass of the catalyst precursor.

[0036] In some embodiments, step 2) includes: activating the catalyst precursor in a carrier gas atmosphere at 300-500 °C for 10-20 h.

[0037] Preferably, in step 2), the carrier gas is an inert gas, and the inert gas is, for example, nitrogen, helium, argon or a mixture thereof, preferably nitrogen.

[0038] In step 2), the activation can be carried out in appropriate equipment, for example, in a fixed bed reactor.

[0039] In step 3), the fluorination can be carried out in appropriate equipment, for example, in a fixed bed reactor, a kettle fixed bed reactor, a fluidized bed reactor or a entrained flow reactor.

[0040] Preferably, the fluorination is carried out in a fixed bed reactor.

[0041] Preferably, the feed flow rate of hydrogen fluoride is 100-170 ml / min.

[0042] Preferably, the fluorination is carried out at 200-300 °C for 10-20 h.

[0043] The catalyst of the present invention has high stability and can reach 1000 h.

[0044] Process for preparing 2,3,3,3-tetrafluoropropene According to another aspect of the present invention, there is provided a method for preparing 2,3,3,3-tetrafluoropropene, which is characterized by comprising: reacting 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride in the presence of the above fluorination catalyst and a carrier gas to obtain 2,3,3,3-tetrafluoropropene, wherein the carrier gas is an inert gas, and the molar ratio of the inert gas:hydrogen fluoride:2-chloro-3,3,3-trifluoropropene is 10:(50-200):10, the reaction temperature is 300-500 °C, and the space velocity is 500-2000 h-1 。

[0045] The method of the present invention uses an inert gas as the carrier gas, which can play a role in preventing the catalyst from coking. The inert gas is as described above, and is preferably nitrogen. At the same time, a small amount of oxidizing gas can be introduced to enhance the anti-sintering ability of the catalyst, and oxygen, air, and chlorine are preferred.

[0046] Preferably, the molar ratio of the inert gas: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene is 10:(150 - 170):10.

[0047] Preferably, the reaction is carried out in a fixed-bed reactor.

[0048] Preferably, the reaction temperature is 350 - 370 °C.

[0049] Preferably, the reaction space velocity is 800 - 1200 h -1 。

[0050] In some embodiments, the reaction is carried out under atmospheric pressure or pressurized conditions.

[0051] The preparation method of 2,3,3,3-tetrafluoropropene of the present invention has a high conversion rate, up to 30%; and has a relatively high selectivity for 2-chloro-3,3,3-trifluoropropene, up to 76%.

[0052] As used in this application, "comprising" and "including" include both the case of consisting only of the elements contained, and the case of containing other elements in addition to the elements contained.

[0053] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. When the definition of a term in this specification conflicts with the meaning commonly understood by those skilled in the art to which the present invention belongs, the definition in this text shall prevail.

[0054] Unless otherwise specified, all numerical values expressing amounts of ingredients, temperatures, etc. used in the specification and claims are understood to be modified by the term "about". Therefore, unless otherwise indicated, the numerical parameters set forth herein are approximate values that can vary depending on the desired properties to be obtained. Examples

[0055] The present invention will be further described below in conjunction with examples, so that those skilled in the art can fully understand the purpose, features, and effects of the present invention.

[0056] Example 1 Weigh 20 g of Cr(NO3)3·9H2O and 0.07 g of K2SiO3 according to the mass ratio of Cr:Si of 100:0.5. Dissolve Cr(NO3)3·9H2O in 5 ml of deionized water and dissolve K2SiO3 in 2 ml of deionized water.

[0057] Then, the prepared aqueous solution of Cr(NO3)3·9H2O was loaded onto 10 g of activated carbon by impregnation, and dried in an oven at 100 °C for 4 h after 4 h. Then, the prepared aqueous solution of K2SiO3 was loaded onto the above-mentioned dried activated carbon by impregnation, and dried in an oven at 100 °C for 4 h after 4 h.

[0058] Next, in a muffle furnace, under a nitrogen atmosphere, the temperature was raised to 350 °C at a heating rate of 1 °C / min and calcined for 4 h to obtain a catalyst precursor. The catalyst precursor was ground and crushed, sieved through a 7-10 mesh sieve, and 10 ml of the sieved catalyst precursor particles were loaded into a fixed-bed tubular reactor with an inner diameter of 15 mm, activated under a nitrogen atmosphere, the temperature was raised to 350 °C at a heating rate of 1 °C / min, and activated for 16 h to obtain an activated catalyst precursor. Subsequently, the temperature was lowered to 275 °C, and fluorinated with 100 ml / min of hydrogen fluoride for 16 h to obtain a fluorinated catalyst.

[0059] Control the molar ratio of nitrogen:hydrogen fluoride:2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorinated catalyst and at a reaction temperature of 350 °C and a space velocity of 1000 h -1 2-chloro-3,3,3-trifluoropropene was reacted with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0060] After the reaction product was washed with water and alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene was analyzed to be 18% and the selectivity of 2,3,3,3-tetrafluoropropene was 63% by a gas chromatograph (Agilent 7890B gas chromatograph).

[0061] Example 2 The fluorinated catalyst was prepared according to the method of Example 1, except that 0.14 g of K2SiO3 was weighed, that is, the mass ratio of Cr:Si was 100:1.

[0062] Control the molar ratio of nitrogen:hydrogen fluoride:2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorinated catalyst and at a reaction temperature of 350 °C and a space velocity of 1000 h -1 2-chloro-3,3,3-trifluoropropene was reacted with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0063] After the reaction product was washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene was analyzed to be 21% and the selectivity for 2,3,3,3-tetrafluoropropene was 78% using a gas chromatograph (Agilent 7890B).

[0064] Example 3 Weigh 20 g of Cr(NO3)3·9H2O and 0.07 g of K2SiO3 according to a mass ratio of Cr:Si of 100:0.5. Dissolve Cr(NO3)3·9H2O in 5 ml of deionized water, and dissolve K2SiO3 in 2 ml of deionized water and add 52.55 g of 10 wt.% ammonia water solution.

[0065] Drop the two solutions simultaneously into a container containing 5 ml of deionized water while stirring continuously. Continuously monitor the pH of the solution during the dropping process. When the pH reaches 7 - 8, stop dropping. At this time, the precipitation is complete. After continuous stirring for 1 h, filter, and dry the precipitate in an oven at 100 °C for 4 h.

[0066] Then, in a muffle furnace, under a nitrogen atmosphere, heat it to 350 °C at a heating rate of 1 °C / min and calcine for 4 h. Take 10 ml of the calcined powdery product and mechanically mix it with 5 wt.% graphite and 10 wt.% polyvinyl alcohol. After tabletting, a catalyst precursor is obtained. Grind and crush the catalyst precursor, then sieve it through a 7 - 10 mesh sieve. Take 10 ml of the sieved catalyst precursor particles and load them into a fixed-bed tubular reactor with an inner diameter of 15 mm. Activate it under a nitrogen atmosphere, heat it to 350 °C at a heating rate of 1 °C / min, and activate for 16 h to obtain an activated catalyst precursor. Subsequently, cool it to 275 °C and fluorinate it with 100 ml / min of hydrogen fluoride for 16 h to obtain a fluorinated catalyst.

[0067] Control the molar ratio of nitrogen:hydrogen fluoride:2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorinated catalyst, at a reaction temperature of 350 °C and a space velocity of 1000 h -1 , allow 2-chloro-3,3,3-trifluoropropene to react with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0068] After the reaction product was washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene was analyzed to be 25% and the selectivity for 2,3,3,3-tetrafluoropropene was 58% using a gas chromatograph (Agilent 7890B).

[0069] Example 4 Prepare the fluorinated catalyst according to the method of Example 3, with the difference that 0.14 g of K2SiO3 is weighed, i.e., the mass ratio of Cr:Si is 100:1.

[0070] Control the molar ratio of nitrogen: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorination catalyst and at a reaction temperature of 350 °C and a space velocity of 1000 h -1 , react 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0071] After the reaction product is washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene is analyzed to be 30% and the selectivity for 2,3,3,3-tetrafluoropropene is 76% using a gas chromatograph (Agilent 7890B gas chromatograph).

[0072] Comparative Example 1 Prepare the fluorination catalyst according to the method of Example 1, except that 0.21 g of K2SiO3 is weighed, i.e., the mass ratio of Cr:Si is 100:3.

[0073] Control the molar ratio of nitrogen: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorination catalyst and at a reaction temperature of 350 °C and a space velocity of 1000 h -1 , react 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0074] After the reaction product is washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene is analyzed to be 12% and the selectivity for 2,3,3,3-tetrafluoropropene is 55% using a gas chromatograph (Agilent 7890B gas chromatograph).

[0075] Comparative Example 2 Prepare the fluorination catalyst according to the method of Example 3, except that 0.21 g of K2SiO3 is weighed, i.e., the mass ratio of Cr:Si is 100:3.

[0076] Control the molar ratio of nitrogen: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene to be 10:170:10. In the presence of the prepared fluorination catalyst and at a reaction temperature of 350 °C and a space velocity of 1000 h -1 , react 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0077] After the reaction product is washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene is analyzed to be 15% and the selectivity for 2,3,3,3-tetrafluoropropene is 54% using a gas chromatograph (Agilent 7890B gas chromatograph).

[0078] Comparative Example 3 The fluorination catalyst was prepared by the method of Example 3, except that 0.07 g of K2O3Si was replaced with 0.054 g of ZnCl2, i.e., the mass ratio of Cr:Zn was 100:1.

[0079] The molar ratio of nitrogen:hydrogen fluoride:2-chloro-3,3,3-trifluoropropene was controlled to be 10:170:10. In the presence of the prepared fluorination catalyst, at a reaction temperature of 350 °C and a space velocity of 1000 h -1 , 2-chloro-3,3,3-trifluoropropene was reacted with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene.

[0080] After the reaction product was washed with water and then with alkali to remove acidic gases, the conversion rate of 2-chloro-3,3,3-trifluoropropene was analyzed to be 8% and the selectivity of 2,3,3,3-tetrafluoropropene was 21% by a gas chromatograph (Agilent 7890B gas chromatograph).

[0081] The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the essential technical content of the present invention. The essential technical content of the present invention is broadly defined in the scope of the claims of this application. Any technical entity or method completed by others, if it is exactly the same as that defined in the scope of the claims of this application, or is an equivalent change, will be regarded as being covered by the scope of the claims of this application.

Claims

1. A fluorination catalyst, characterized in that Prepared by the following steps: 1) Preparation of catalyst precursor: The catalyst precursor is obtained by impregnating a water-soluble trivalent chromium salt and a water-soluble silicate according to a Cr:Si mass ratio of 100:0.5-2 on a catalyst carrier, and drying and calcining the carrier. Or Co-precipitating a water-soluble trivalent chromium salt and a water-soluble silicate at a Cr:Si mass ratio of 100:0.5-2, drying and calcining the precipitate, mixing it with a polyvinyl alcohol binder and graphite, and pressing it into tablets to obtain a catalyst precursor; 2) Activating the catalyst precursor: activating the catalyst precursor in a carrier gas atmosphere to obtain an activated catalyst precursor; and 3) Fluorination of catalyst precursor: Fluorinating the activated catalyst precursor with hydrogen fluoride to obtain a fluorination catalyst.

2. The fluorination catalyst according to claim 1, characterized in that The water-soluble trivalent chromium salt is selected from chromium nitrate, chromium chloride, chromium sulfate and chromium acetate, and / or The water-soluble silicate is selected from potassium silicate, sodium silicate, lithium silicate and potassium aluminum silicate.

3. The fluorination catalyst according to claim 1 or 2, characterized in that In step 1), the mass ratio of Cr:Si is 100:0.5-1.

4. The fluorination catalyst according to any one of claims 1 to 3, characterized in that Step 1) is implemented by following steps ad: a. preparing a water-soluble trivalent chromium salt aqueous solution and a water-soluble potassium silicate aqueous solution respectively; b. Applying an aqueous solution of trivalent chromium salt to the catalyst support for impregnation and drying after 3-5 hours; c. applying an aqueous solution of potassium silicate to the carrier after drying in step b for impregnation and drying after 3-5h; and d. calcining the dried support in step c for 4-8h at 300-500°C under an inert gas atmosphere to obtain a catalyst precursor; Alternatively, step 1) is implemented by following steps a′-d′: a' respectively prepared water-soluble trivalent chromium salt aqueous solution and water-soluble potassium silicate ammonia solution; b'. The two solutions were simultaneously added to deionized water for co-precipitation. After the precipitation was complete, the precipitate was collected by filtration and the precipitate was dried; c'. The dried product was calcined at 300-500 ℃ for 4-8h under an inert gas atmosphere; and d′. The calcined product is mixed with a polyvinyl alcohol binder and graphite, and the catalyst precursor is obtained after tableting.

5. The fluorination catalyst according to any one of claims 1 to 4, characterized in that The mass fraction of the polyvinyl alcohol binder is 10-15% of the total mass of the catalyst precursor, preferably 10-12%.

6. The fluorination catalyst according to any one of claims 1 to 5, characterized in that Step 2) comprises: activating the catalyst precursor at 300-500° C. for 10-20 hours in a carrier gas atmosphere.

7. The fluorination catalyst according to any one of claims 1 to 6, characterized in that In step 2), the carrier gas is an inert gas.

8. The fluorination catalyst according to any one of claims 1 to 7, characterized in that In step 3), the fluorination is carried out at 200-300° C. for 10-20 h.

9. A method for preparing 2,3,3,3-tetrafluoropropene, characterized in that: include: In the presence of a fluorination catalyst according to any one of claims 1 to 8 and a carrier gas, 2-chloro-3,3,3-trifluoropropene is reacted with hydrogen fluoride to obtain 2,3,3,3-tetrafluoropropene, wherein the carrier gas is an inert gas, the inert gas: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene molar ratio is 10: (50-200): 10, the reaction temperature is 300-500° C., and the space velocity is 500-2000 h -1 .

10. The method according to claim 9, characterized in that The molar ratio of the inert gas: hydrogen fluoride: 2-chloro-3,3,3-trifluoropropene is 10:(150-170):10, the reaction temperature is 350-370°C, and the space velocity is 800-1200h -1 .