Preparation method of 2, 3, 3, 3-tetrafluoropropene

Abstract

The invention provides a preparation method of 2, 3, 3, 3-tetrafluoropropene, which comprises the following steps: 1) respectively preheating 2, 3, 3, 3-tetrachloropropene and hydrogen fluoride, and inputting into a first reactor for reaction to obtain a first material; 2) returning a first unreacted material obtained by separating the first material to the first reactor, and inputting 2-chloro-3, 3, 3-trifluoropropene into a second reactor; 3) carrying out reaction on newly input hydrogen fluoride and 2-chloro-3, 3, 3-trifluoropropene in a second reactor to obtain a second material; and 4) returning a second unreacted material obtained by separating the second material to the second reactor, and refining the 2, 3, 3, 3-tetrafluoropropene crude product to obtain a 2, 3, 3, 3-tetrafluoropropene product. Wherein the first reactor and the second reactor are filled with a chromium-free iron-based gas phase fluorination catalyst. According to the invention, a byproduct hydrogen chloride product can be produced, and the conversion rate of each reaction section is effectively improved, so that the yield of the whole process is improved; the whole process flow is convenient, stable in process operation, green and non-toxic, and has important industrial application value.

Description

Technical Field

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

[0002] 2,3,3,3-Tetrafluoropropylene (HFO-1234yf) is a novel environmentally friendly refrigerant and specialty fluorinated chemical that has attracted much attention in recent years. The core challenge in its synthesis lies in achieving high-efficiency, low-pollution production and overcoming problems such as low selectivity and numerous byproducts in existing technological routes.

[0003] In industrial production, the mainstream synthesis processes for 2,3,3,3-tetrafluoropropene mainly include the following routes: preparation via addition-elimination reaction using hexafluoropropene as a raw material; preparation via dehydrofluorination reaction using pentafluoropropane as a raw material; preparation via fluorine-chlorine exchange method using 2-chloro-3,3,3-trifluoropropene as a raw material; synthesis via high-temperature cracking reaction using chloromethane and tetrafluoroethylene as raw materials; and preparation via a mixture of hexafluoropropane and pentafluoropropane as raw materials. Among these, the hexafluoropropene method has a long reaction process and a relatively low overall yield; the pentafluoropropane method has problems such as a complex reaction route and a large amount of waste generation, resulting in a high cost of the final product; while the fluorine-chlorine exchange route using 2-chloro-3,3,3-trifluoropropene as a raw material has advantages such as fewer reaction steps and higher raw material utilization. The other processes can mostly be regarded as derivatives of the above main routes, and all require further conversion through corresponding intermediates to obtain the target product. Overall, there is still room for optimization in terms of reaction efficiency and economy.

[0004] Patent CN101597209A discloses an integrated preparation process for 2,3,3,3-tetrafluoropropylene, comprising three key steps: 1,1,2,3-tetrachloropropylene reacts with a first fluorinating agent to generate a primary intermediate composition mainly composed of 2-chloro-3,3,3-trifluoropropylene and containing chlorine byproducts; the primary intermediate further reacts with a second fluorinating agent to obtain an intermediate composition containing 2-chloro-1,1,1,2-tetrafluoropropane and secondary chlorine-containing byproducts; and the target product 2,3,3,3-tetrafluoropropylene is synthesized by a catalytic dehydrochlorination reaction. The process has the following limitations: In the high-temperature reaction environment containing chlorine / fluorine media, the inner wall of the reactor is prone to corrosion, which can lead to equipment bulging or even deformation, and the range of corrosion-resistant materials available is relatively limited; the dehydrochlorination step (saponification reaction) generates a large amount of high-salt wastewater and organic waste residue, and the separation of by-products is difficult, resulting in a product yield lower than that required for industrial applications; in addition, the multi-stage reaction series process leads to redundant configuration of separation equipment, and the active components of the fluorination catalyst are easily lost under the action of chlorine-containing by-products, and the catalyst life is usually less than 200 hours.

[0005] Patent CN112592254A discloses a system and method for preparing 2,3,3,3-tetrafluoropropylene. The core innovation of this patent lies in employing a fully gas-phase, continuous-flow tubular reactor process, using 1,1,2,3-tetrachloropropylene (HCFO-1230xa) as raw material, to continuously synthesize the target product through catalytic fluorination and catalytic elimination reactions. This process effectively avoids the severe corrosion of equipment caused by the liquid-phase reaction environment, and simultaneously achieves low liquid holdup and continuous operation through the tubular reactor, improving process safety. However, this technology still has several limitations in practical operation. First, the selectivity of the final product HFO-1234yf is low and fluctuates significantly (e.g., the selectivity of the product in its examples ranges from 32.39% to 45.63%), especially in the elimination reaction stage, where more than half of the intermediates are converted into non-target byproducts, resulting in unsatisfactory yields. Second, the elimination reaction catalyst formulation is relatively complex, but the patent does not clearly explain the structure-activity relationship between its active component structure and high performance, indicating that the current catalyst has not yet reached its optimal state in terms of design optimization and control of the target reaction pathway. The low selectivity further raises concerns about the economics of the process, as a large amount of expensive raw materials are consumed to generate worthless byproducts, which not only increases the unit cost but also pollutes the reaction system due to the accumulation of byproducts, increasing the load and cost of subsequent separation and raw material recovery sections. In addition, the process flow also has shortcomings in energy integration. There is a lack of efficient thermal integration design between the high-temperature reaction products and the low-temperature separation unit, and a large amount of high-temperature heat energy is not recovered but dissipated through cooling water, resulting in low overall energy utilization efficiency.

[0006] In addition, patents CN102603464A, CN103946196A, CN104169245A, CN105188909A, and CN105377797A also use a three-step method to prepare tetrafluoropropylene. Although the three-step method has been industrialized, its disadvantages are also quite significant: (1) The overall process is long and inefficient. After each reaction, the product needs to be separated and purified before it can be used as the raw material for the next step. Each additional step requires multiple distillation columns, washing equipment, etc., resulting in huge investment. Each reaction has conversion and selectivity issues. The total yield of the multi-step reaction is the product of the yields of each step. Therefore, with each additional reaction, the total yield may decrease. (2) Each reactor needs to operate at a specific temperature and pressure. Each separation device needs to consume a large amount of energy (cooling water, steam, electricity), resulting in very high energy consumption throughout the process. (3) Three-step reactions usually require two or more different types of catalysts (such as chromium-based catalysts, tin-based catalysts, etc.), and the preparation, loading, regeneration and replacement of catalysts are complicated.

[0007] Some companies are now adopting a two-step process to produce tetrafluoropropylene from tetrachloropropylene. By integrating the three-step reaction into two steps, this process brings comprehensive improvements: First, it significantly simplifies the process flow and improves efficiency. Reducing the number of core reactors and their associated separation, purification, and heating / cooling systems results in a decrease in the number of equipment, piping, instrumentation, and plant space, leading to a significant reduction in initial fixed asset investment. Second, it lowers operating costs. Fewer reaction steps mean lower energy consumption (steam, electricity, cooling water), less manual labor, and simpler process control, optimizing daily operating costs. Third, it shortens the production cycle. The shorter residence time of materials in the unit increases the product output rate per unit time, improving the unit's production efficiency. However, it should be noted that although the two-step process improves the overall reaction yield and material utilization, each chemical reaction step cannot achieve 100% conversion and selectivity, resulting in losses of raw materials and byproducts.

[0008] Patent CN102001910A discloses a method for preparing 2,3,3,3-tetrafluoropropene. This method first involves a fluorination reaction between hydrogen fluoride and 1,1,2,3-tetrachloropropene in a first reactor. After separation, the intermediate product is further fluorinated in a second reactor, and after another separation, the final product is obtained and discharged from the system. In this method, the raw materials and intermediate products undergo two separations within the system. Unreacted hydrogen fluoride and 1,1,1,2,2-pentafluoropropane can be recycled back to either the first or second reactor to continue the reaction, while other intermediate products are returned to the second reactor for further fluorination. It is noteworthy that the catalyst used in this patent is a chromium-based fluorination catalyst containing aluminum, zinc, magnesium, and nickel. During long-term operation, this catalyst may gradually deactivate due to carbon buildup or changes in crystal structure, leading to a decrease in reaction rate and product selectivity. Furthermore, the process lacks a catalyst regeneration step, resulting in low catalyst utilization efficiency. In addition, various byproducts are generated during the reaction, requiring additional separation and treatment measures for purification, increasing the complexity of the process and operating costs.

[0009] Patent CN104136404A discloses a method for preparing 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf). This method involves a gas-phase catalytic reaction of starting materials with hydrogen fluoride in a reactor. The resulting mixture is first separated to obtain a first stream containing hydrogen chloride and the product 2-chloro-3,3,3-trifluoropropene, and a second stream containing unreacted starting materials, hydrogen fluoride, and intermediate products. These two streams are then further purified in subsequent separation units to obtain the target product. Notably, hydrogen fluoride, unreacted materials, and some intermediate products can be recycled back to the reaction system to participate in the reaction again, improving the utilization rate of the raw materials. However, this process also has several limitations in practical applications: on the one hand, the catalyst used (usually a chromium-based catalyst) is prone to coking under high-temperature reaction conditions, and the patent does not clearly address effective regeneration measures to remove carbon from the catalyst surface, resulting in a gradual decrease in catalyst activity and affecting catalytic efficiency and service life; on the other hand, the material flowing out of the reactor outlet needs to be cooled before phase separation, and the separated hydrogen fluoride needs to be re-gasified and heated to the reaction temperature before entering the system again. This cooling-reheating process causes significant energy loss and low overall energy utilization efficiency.

[0010] In addition, Chinese patents CN107652159A, CN110914227A, CN111770908A, and CN116120147A also employ a two-step method to prepare tetrafluoropropylene. The existing two-step process for producing tetrafluoropropylene from tetrachloropropylene still has the following limitations: the two-step method requires two different types of catalysts, each suitable for one of the two reactions; the catalyst is very sensitive to impurities, and even trace amounts of impurities in the feedstock can lead to catalyst poisoning or coking and deactivation; frequent catalyst regeneration and replacement increase operational complexity and cost. Both reactions require high conversion rates and high selectivity. If the conversion rate of the first step is low, unreacted feedstock will enter the second step, increasing the separation burden and potentially affecting the catalyst activity in the second step; if the selectivity of either step is low, a large number of byproducts (such as various chlorofluoropropane isomers, low-fluoride products, and small cleavage molecules) will be generated, which not only reduces the yield but also makes subsequent separation and purification very difficult.

[0011] Chromium-based catalysts have a long history of application in fluorochemicals, and due to their good activity and relative cost advantage, they have been extensively studied for the synthesis of tetrafluoropropylene. However, they also have a series of significant drawbacks: (1) Hexavalent chromium compounds are extremely toxic and are internationally recognized as strong carcinogens and mutagens, posing serious harm to human skin, respiratory tract and internal organs. Deactivated spent catalysts are hazardous wastes, and their treatment process is complex and costly. (2) In the reaction, the selectivity of chromium-based catalysts for the target product is often not ideal. Low selectivity means that the effective conversion rate of raw materials is reduced, requiring more complex subsequent purification steps to separate the target product, thereby increasing production costs. (3) During the reaction, especially at higher reaction temperatures, carbon deposition is prone to occur on the catalyst surface; organic matter carbonizes at active sites, forming a coke layer that covers the active sites, leading to rapid catalyst deactivation. (4) Due to carbon deposition and the loss of some active components, the catalyst has a short service life and requires frequent carbon burning regeneration (introducing air or oxygen to burn off the carbon deposits). The regeneration process not only interrupts production and consumes energy, but may also repeatedly damage the catalyst structure, leading to a gradual decrease in its activity. (5) Chromium-based catalysts usually need to be in a higher temperature range to exhibit sufficient activity. (6) Studies have shown that although some chromium-based catalysts exhibit high activity and selectivity in the early stages of the reaction, they are prone to slow deactivation during the reaction process. Mechanistically, oligomers, polymers, and small molecule decomposition products (such as C1 and C2 carbon compounds) are often generated in the reaction system. These substances further promote coking on the catalyst surface, covering active sites or blocking the pore structure, which is considered to be the main reason for the gradual deactivation of the catalyst. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention discloses a method for preparing 2,3,3,3-tetrafluoropropylene, which solves the problems of complex process flow, low conversion efficiency, short catalyst life, and toxicity caused by the use of chromium-based catalysts in the preparation of 2,3,3,3-tetrafluoropropylene in existing technologies.

[0013] To achieve the above technical objectives, this invention proposes a method for preparing 2,3,3,3-tetrafluoropropylene. This method is carried out in a first reactor and a second reactor, and includes the following steps: (1) 2,3,3,3-tetrachloropropene and hydrogen fluoride are preheated and then fed into the first reactor to react and obtain the first material; (2) The first material is input into the first separation process; the first unreacted material obtained by separation is returned to the first reactor; the hydrogen chloride obtained by separation is purified by the acid production unit and output as hydrochloric acid product; the 2-chloro-3,3,3-trifluoropropene obtained by separation is input into the second reactor; (3) The newly introduced hydrogen fluoride reacts with 2-chloro-3,3,3-trifluoropropene in the second reactor to obtain the second material; (4) The second material is fed into the second separation process; the second unreacted material obtained by separation is returned to the second reactor, and the crude 2,3,3,3-tetrafluoropropylene obtained by separation is refined to obtain the 2,3,3,3-tetrafluoropropylene product; Both the first and second reactors are filled with a chromium-free iron-based gas-phase fluorination catalyst, which, based on 100 parts by weight of the support, comprises: 20-35 parts by weight of iron fluoride; 5 to 15 parts by weight of a first additive, wherein the first additive comprises a metal fluoride of one or more elements selected from titanium, tin, and antimony; 5-10 parts by weight of a second auxiliary agent, wherein the second auxiliary agent comprises one or more of calcium peroxide, strontium peroxide, magnesium peroxide, potassium permanganate, zinc peroxide, and sodium percarbonate; 1 to 5 parts by weight of adhesive, wherein the adhesive comprises one or two of aluminum dihydrogen phosphate and aluminum phosphate; 100 mass copies of the carrier.

[0014] In the above technical solution, the reaction is carried out under the action of a specific chromium-free iron-based gas-phase fluorination catalyst. This catalyst significantly improves catalytic performance by introducing a first promoter, a metal fluoride. The metal fluoride of the first promoter undergoes controllable thermal decomposition within a specific temperature range, simultaneously releasing heat of reaction and generating active oxygen species in situ, promoting the kinetics of the fluorine-chlorine exchange reaction, thus enhancing the selectivity of the target product. Simultaneously, the Lewis acid strength on the catalyst surface can be modulated through electronic effects (e.g., optimizing the Brønsted acid / Low acid ratio), suppressing side reaction pathways and reducing over-fluorination and the generation of cracking byproducts. The second promoter's oxygen storage capacity (continuously removing surface carbon precursors) results in a lower carbon buildup rate and extended lifespan after catalyst operation. Both the first step reaction (first reactor) and the second step reaction (second reactor) under the action of this catalyst maintain high conversion rates and high selectivity, thereby obtaining 2,3,3,3-tetrafluoropropylene in high yield. Furthermore, this chromium-free iron-based gas-phase fluorination catalyst does not contain toxic chromium, avoiding harm to human health and meeting green chemical standards. The catalyst's constituent raw materials are readily available and low-cost, offering a significant cost advantage.

[0015] Furthermore, the above technical solution incorporates a first separation step between the first and second reactions. This step precisely separates the product, HCl, unreacted raw materials, and byproducts from the first material, enabling the targeted recycling of the reactants. This separation step also removes harmful byproducts, preventing their adsorption at active sites and subsequent irreversible poisoning. Furthermore, the removal of free water and acidic halides inhibits electrochemical corrosion. The above technical solution also refines hydrogen chloride into hydrochloric acid, thereby increasing the added value of the byproducts.

[0016] In step (2), the first unreacted material obtained through the first separation process is a mixture containing hydrogen fluoride or a mixture containing hydrogen fluoride and 2,3,3,3-tetrachloropropene. It should be noted that this first unreacted material itself has a certain temperature. In order to better control the overall temperature of the reactants and prevent local overheating from negatively impacting subsequent reactions, this material can be recycled into the first reactor without further preheating. The newly added hydrogen fluoride in step (3) can be introduced into the second reaction without preheating. In step (4), the second unreacted material obtained through the second separation process is a mixture containing hydrogen fluoride or a mixture containing hydrogen fluoride and 2-chloro-3,3,3-trifluoropropene. Furthermore, the hydrogen chloride generated in the second reactor will be uniformly input into the post-processing process for post-treatment.

[0017] In a further example of the present invention, in step (1), the preheating temperature of 2,3,3,3-tetrachloropropene is 200~300°C.

[0018] In a further example of the present invention, the preheating temperature of hydrogen fluoride in step (1) is 200~300°C.

[0019] It should be noted that the present invention does not limit the method by which the preheated 2,3,3,3-tetrachloropropene and preheated hydrogen fluoride are fed into the first reactor. They can be fed into the first reactor separately, or mixed using a mixer before being fed into the first reactor. In an optional example of the present invention, the preheated 2,3,3,3-tetrachloropropene and preheated hydrogen fluoride can be mixed using a mixer before being fed into the first reactor.

[0020] In a further example of the present invention, the reaction temperature of the first reactor is 250~350°C, and the contact time between the reactants and the catalyst in the reactor is 5~20 seconds.

[0021] The structure of the first reactor is not limited in this invention; any reactor that can be filled with a catalyst and provides reaction space for the fluorination of 2,3,3,3-tetrachloropropene to obtain 2-chloro-3,3,3-trifluoropropene can be used. In a further example of this invention, the first reactor is a fixed-bed reactor, preferably a single-stage fixed-bed reactor.

[0022] In a further example of the invention, the pressure of the first reactor is 0.13 bar to 3.6 bar.

[0023] In a further example of the invention, the molar ratio of hydrogen fluoride to 2,3,3,3-tetrachloropropene in the first reactor is 4 to 10; understandably, by introducing excess hydrogen fluoride, the conversion rate of 2,3,3,3-tetrachloropropene can be improved; in a subsequent first separation step, this portion of excess unreacted hydrogen fluoride will be separated and returned to the first reaction as the first unreacted material. In an optional example of the invention, the molar ratio of hydrogen fluoride to 2,3,3,3-tetrachloropropene in the first reactor is 5 to 8.

[0024] In the above technical solution, 2,3,3,3-tetrachloropropene undergoes a chlorine-fluorine exchange (halogen exchange) reaction with HF in the first reactor, where the three chlorine atoms at the 3-position are successively replaced by fluorine to generate 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf). Therefore, the first material contains components such as 2-chloro-3,3,3-trifluoropropene, hydrogen chloride, unreacted hydrogen fluoride, and 2,3,3,3-tetrachloropropene, as well as some byproducts. These materials can be separated by feeding the first material into the first separation process.

[0025] In a further example of the present invention, the specific structure and control conditions of the first separation process were explored and optimized. Optionally, the first separation process is carried out in a first distillation column and a second distillation column connected in series. The outlet of the first reactor is connected to the inlet of the first distillation column, and the bottom outlet of the first distillation column is connected to the inlet of the second distillation column. Hydrogen chloride is collected from the top of the first distillation column, and the first unreacted material is collected from the bottom of the second distillation column. The top outlet of the second distillation column is connected to the inlet of the second reactor, thereby feeding the separated 2-chloro-3,3,3-trifluoropropylene into the second reactor. Further optionally, the top temperature of the first distillation column is 20~40°C, the bottom temperature is 30~60°C, and the operating pressure is 1~3 bar. Further optionally, the top temperature of the second distillation column is 50~70°C, the bottom temperature is 150~180°C, and the operating pressure is 5~8 bar.

[0026] In a further example of the invention, the specific structure and control conditions of the acid production unit were explored and optimized. Optionally, the acid production unit includes a shell-and-tube heat exchanger and a falling film absorption tower, from which a high-concentration hydrochloric acid product is collected from the bottom of the falling film absorption tower; and from the top of the falling film absorption tower, tail gas (including non-condensable gas, trace amounts of hydrogen chloride, etc.) is collected. Further optionally, the outlet temperature of the shell-and-tube heat exchanger is -15°C to -35°C, thereby recovering the heat from the hydrogen chloride separated in the first separation process. Further optionally, the outlet pressure of the shell-and-tube heat exchanger is a slightly positive pressure of 0.5-2 bar. Further optionally, the temperature of the falling film absorption tower is 20-40°C at the top, 30-50°C at the bottom, and the operating pressure is 0.5-1.5 bar.

[0027] In a further example of the invention, the second reactor is a two-stage tubular fixed-bed reactor, comprising two reaction sections connected in series, with the second material being extracted from the outlet of the lower reaction section. The second reactor, through its multi-tube parallel structure, can achieve a material throughput of tons per hour, meeting the needs of large-scale industrial continuous production. The design of the two series-connected reaction sections allows the material to flow in a piston-like flow within the reaction tubes, ensuring uniform radial mixing and eliminating axial backmixing. Furthermore, the reactant concentration decreases gradually along the tube length, which can drive the reaction equilibrium forward and improve product conversion.

[0028] In a further example of the present invention, the reaction temperature in the upper section of the second reactor is 250~350℃, the reaction temperature in the lower section is 300~350℃, and the contact time between the reactants and the catalyst in the second reactor is 5~25 seconds. By implementing a segmented temperature control system for different reaction sections in the second reactor, the energy consumption of the gas-phase fluorination process is reduced, avoiding energy waste caused by excessive cooling in traditional processes; electrochemical corrosion at the gas-liquid interface is eliminated, solving the problem of weld cracking in the liquid-phase fluorination reactor, and reducing equipment maintenance costs.

[0029] In a further example of the invention, the molar ratio of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene in the second reactor is 1 to 5. In an optional example of the invention, the molar ratio of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene in the second reactor is 2 to 4; understandably, by introducing excess hydrogen fluoride, the conversion rate of 2-chloro-3,3,3-trifluoropropene can be improved; in a subsequent second separation step, the excess hydrogen fluoride is separated and returned to the second reactor as a second unreacted material.

[0030] In the above technical solution, 2-chloro-3,3,3-trifluoropropene undergoes an addition reaction with hydrogen fluoride in the second reactor to obtain the target product 2,3,3,3-tetrafluoropropene (HFO-1234yf). Therefore, the second material includes 2,3,3,3-tetrafluoropropene, hydrogen chloride, unreacted hydrogen fluoride, and 2-chloro-3,3,3-trifluoropropene, among other components. The components in the second material can be separated through a second separation process.

[0031] In a further example of the present invention, the specific structure and control conditions of the second separation process were explored and optimized. Optionally, the second separation process in step (4) is carried out in a third distillation column, with the outlet of the second reactor connected to the inlet of the third distillation column. Hydrogen chloride is collected from the top of the third distillation column, and the second unreacted material and crude 2,3,3,3-tetrafluoropropylene are collected from the bottom of the column. Further optionally, the top temperature of the third distillation column is -30 to -10°C, the bottom temperature is 20 to 50°C, and the operating pressure is 10 to 20 bar.

[0032] In a further example of the invention, the specific structure and control conditions for the purification operation of the crude 2,3,3,3-tetrafluoropropylene were explored and optimized. Optionally, the purification operation of the crude 2,3,3,3-tetrafluoropropylene is carried out in a fourth distillation column; the reboiler outlet of the third distillation column is connected to the inlet of the fourth distillation column for inputting the crude 2,3,3,3-tetrafluoropropylene to be purified into the fourth distillation column. The 2,3,3,3-tetrafluoropropylene product is collected from the top of the fourth distillation column, and a second unreacted material is collected from the reboiler; this second unreacted material is conveyed to the inlet of the second reactor. Further optionally, the top temperature of the fourth distillation column is 40~70°C, the reboiler temperature is 80~120°C, and the operating pressure is 5~15 bar.

[0033] In a further example of the present invention, the preparation of the chromium-free iron-based gas-phase fluorination catalyst includes the following steps: S1: The carrier is impregnated with an impregnation solution containing an iron source and a first auxiliary precursor, and then dried, calcined and granulated to obtain the first catalyst precursor; S2: The first catalyst precursor is fluorinated by contacting a fluorine source to obtain the second catalyst precursor; S3: The second auxiliary agent and binder are mixed in a solvent to obtain a slurry; the slurry is mixed evenly with the second catalyst precursor and then dried to obtain the chromium-free iron-based gas-phase fluorination catalyst.

[0034] Optionally, the support comprises one or more of activated carbon, graphite, alumina, aluminum fluoride, magnesium fluoride, calcium fluoride, and zirconium fluoride, and the specific surface area of ​​the catalyst support is 100-1500 m². 2 / g.

[0035] Optionally, the iron source includes one or more of ferric nitrate, ferrous nitrate, ferric chloride, and ferric sulfate.

[0036] Optionally, the first auxiliary precursor includes one or more of titanium nitrate, titanium tetrachloride, tin nitrate, tin tetrachloride, tin tetrafluoride, tin sulfate, and antimony pentachloride.

[0037] Optionally, the fluorine source includes one or more of hydrogen fluoride, dichlorodifluoromethane, monochlorodifluoromethane, and monochlorotrifluoromethane.

[0038] Optionally, the solvent includes one or more of water, ethanol, methanol, ethylenediamine, and ammonia.

[0039] In a further example of the present invention, the preparation method further includes: when the reaction yield decreases to a set threshold, cutting off the raw material and introducing a regeneration stream containing an oxidant, and activating the chromium-free iron-based gas-phase fluorination catalyst in situ at 210~410℃ for 0.8~20h. The present invention, through in-situ activation and regeneration of the catalyst, helps maintain stable reactor operation and reduces production interruptions and efficiency fluctuations caused by frequent catalyst replacement; it is simple to operate and the overall process is highly operable.

[0040] It should be noted that the present invention does not limit the specific threshold setting. Any selectable value between 5% and 25% can be set according to actual needs. For example, catalyst activation and regeneration can be started when the reaction yield decreases by 15% relative to the initial reaction yield, thereby maintaining the high efficiency of catalyst catalysis and improving the overall process operating efficiency.

[0041] Optionally, the in-situ activation temperature is 260~360℃.

[0042] Optionally, the in-situ activation time is 1 to 15 hours.

[0043] Optionally, the regeneration stream is a mixture of oxygen and an inert gas. More preferably, it is a mixture of air and an inert gas, or a mixture of oxygen and an inert gas. It should be noted that the inert gas mentioned in this invention refers to a gas that does not chemically interact with the reactants, such as nitrogen and gases of Group 0 elements in the periodic table (e.g., argon, helium, etc.).

[0044] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses 2,3,3,3-tetrachloropropene and hydrogen fluoride as raw materials to prepare 2,3,3,3-tetrafluoropropene through a two-step reaction under the action of a specific chromium-free iron-based gas-phase fluorination catalyst. The overall process has a low carbon deposition rate, a long catalyst lifespan, is green and non-toxic, and can obtain high-purity 2,3,3,3-tetrafluoropropene products with high conversion rates. Furthermore, this invention, through two separation processes, can produce hydrochloric acid as a byproduct, and by separating the byproducts, it effectively improves the conversion rate of each reaction stage, thereby increasing the overall yield. The overall process flow of this invention is convenient, the process operation is stable, and it has significant industrial application value. Attached Figure Description

[0045] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A structural diagram of a method for preparing 2,3,3,3-tetrafluoropropylene according to the present invention is shown. Detailed Implementation

[0046] To facilitate understanding of the present invention, a more comprehensive description will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of protection of the invention.

[0047] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0048] Furthermore, it should be noted that although the various steps of the preparation method of the present invention are described in a specific order in the description of the present invention, these orders are not restrictive. Without departing from the basic principles of the present invention, those skilled in the art can perform the steps in different orders.

[0049] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" or "at least one" means two or more.

[0050] All numerical designations, such as temperature, pressure, time, and ranges, are approximate values. It should be understood that, while not always explicitly stated, all numerical designations are preceded by the term "approximately." It should also be understood that, while not always explicitly stated, the reagents described herein are merely examples, and their equivalents are known in the art.

[0051] The chromium-free iron-based gas-phase fluorination catalyst used in this invention example can be prepared by the following steps: S1: Dissolve 42.8g of anhydrous ferric nitrate (iron source) and 43.6g of titanium nitrate (first auxiliary precursor) in 100ml of water to prepare an impregnation solution; then, in a water bath at 20℃~50℃, stir for 12h, load the impregnation solution onto 100g of activated carbon carrier, filter after full loading, and dry in an oven at 20℃~50℃ for 12~24h; subsequently, calcine at 300℃~500℃ for 6~15h, granulate to obtain the first catalyst precursor; the calcination is carried out in an air atmosphere.

[0052] S2: The first catalyst precursor is fluorinated for 6–12 h in a mixed atmosphere of hydrogen fluoride and nitrogen at 150℃–400℃ to obtain the second catalyst precursor. The fluorine source accounts for 60%–80% of the volume of the mixed atmosphere.

[0053] S3: Weigh 5g of high-purity calcium peroxide (with a particle size of 50-200μm), mix the second auxiliary agent powder with water, ethanol, and binder aluminum dihydrogen phosphate, and stir until uniform to obtain a slurry with a second auxiliary agent content of 2-3mol / L; stir and mix the slurry with the second catalyst precursor; filter, wash, and dry under an inert atmosphere at 40-60℃ to obtain the chromium-free iron-based gas-phase fluorination catalyst.

[0054] Example 1

[0055] A method for preparing 2,3,3,3-tetrafluoropropylene, specifically: (1) 2,3,3,3-tetrachloropropene and hydrogen fluoride (HF) are preheated to 240°C by a preheater; the two preheated materials are mixed and fed into a first reactor filled with the chromium-free iron-based gas-phase fluorination catalyst for reaction, the molar ratio of hydrogen fluoride and 2,3,3,3-tetrachloropropene is 5; the reaction temperature is 280°C, the reaction pressure is 1 bar, and the contact time between the reactants and the catalyst is 10 seconds, to obtain a first material containing 2-chloro-3,3,3-trifluoropropene, hydrogen chloride, and unreacted hydrogen fluoride and 2,3,3,3-tetrachloropropene.

[0056] (2) The first material passes through a first separation process, which includes two distillation columns connected in series. The outlet of the first reactor is connected to the inlet of the first distillation column, the outlet of the first distillation column is connected to the inlet of the second distillation column, and the outlet of the second distillation column is connected to the second reactor. The top temperature of the first distillation column is 20~40℃, the bottom temperature is 30~60℃, and the operating pressure is 1~3 bar. The top temperature of the second distillation column is 50~70℃, the bottom temperature is 150~180℃, and the operating pressure is 5~8 bar. The unreacted 2,3,3,3-tetrachloropropene and hydrogen fluoride obtained by separation are returned to the first reactor to continue to participate in the reaction. The 2-chloro-3,3,3-trifluoropropene obtained by separation is input into the second reactor to participate in the next step of the reaction. The separated hydrogen chloride enters the acid production system to produce hydrochloric acid.

[0057] (3) 2-Chloro-3,3,3-trifluoropropene enters a two-stage tubular reactor (second reactor) and reacts in the presence of hydrogen fluoride and the chromium-iron-based gas-phase fluorination catalyst. The molar ratio of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene is 2. The temperature of the upper section (upper reaction section) of the reactor is 300°C, and the temperature of the lower section (lower reaction section) is 320°C. The contact time between the reactants and the catalyst in the second reactor is 15 seconds. The resulting second material contains 2,3,3,3-tetrafluoropropene, hydrogen chloride, and unreacted hydrogen fluoride and 2-chloro-3,3,3-trifluoropropene.

[0058] (4) The second material is fed into the separation tower of the second separation process for separation. The second separation process is in the third distillation tower. The outlet of the second reactor is connected to the inlet of the third distillation tower, and the outlet of the third distillation tower is connected to the inlet of the fourth distillation tower (used for product purification). The top temperature of the third distillation tower is -30~-10℃, the bottom temperature is 20~50℃, and the operating pressure is 10~20℃. bar; crude 2,3,3,3-tetrafluoropropylene is collected from the bottom of the third reactor and enters the product refining process (fourth distillation column). The top temperature of the column is 40~70℃, the bottom temperature is 80~120℃, and the operating pressure is 5~15 bar; after the distillation process in the fourth distillation column, the target product 2,3,3,3-tetrafluoropropylene with a purity of 99.5% is obtained from the top of the column; unreacted hydrogen fluoride and 2-chloro-3,3,3-trifluoropropylene collected from the bottom of the fourth distillation column are returned to the second reactor to continue to participate in the reaction.

[0059] Example 2

[0060] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is 250°C, the reaction pressure is 1 bar, and the contact time is 5 seconds.

[0061] Example 3

[0062] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is 320°C, the reaction pressure is 0.8 bar, and the contact time is 20 seconds.

[0063] Example 4

[0064] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is set to 280°C, the reaction pressure is set to 1.2 bar, and the contact time is 5 seconds.

[0065] Example 5

[0066] The operation steps and condition control in this embodiment are the same as in embodiment 1, except that the temperature of the first reactor is set to 320°C, the reaction pressure is set to 1 bar, and the contact time is 5 seconds.

[0067] Example 6

[0068] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is set to 250°C, the reaction pressure is set to 1.2 bar, and the contact time is 10 seconds.

[0069] Example 7

[0070] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is set to 280°C, the reaction pressure is set to 0.8 bar, and the contact time is 15 seconds.

[0071] Example 8

[0072] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is set to 250°C, the reaction pressure is set to 1 bar, and the contact time is 8 seconds.

[0073] Example 9

[0074] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the first reactor is set to 320°C, the reaction pressure is set to 1.2 bar, and the contact time is 10 seconds.

[0075] Example 10

[0076] The operating steps and condition control in this embodiment are the same as in Example 1, except that the molar ratio of hydrogen fluoride to 2,3,3,3-tetrachloropropene in the first reactor is 8.

[0077] Example 11

[0078] The operating steps and condition control in this embodiment are the same as in Example 1, except that the molar ratio of hydrogen fluoride and 2-chloro-3,3,3-trifluoropropylene in the second reactor is 4.

[0079] Example 12

[0080] The operation steps and condition control in this embodiment are the same as in Embodiment 1, except that the temperature of the upper section (upper reaction section) of the second reactor is 250°C, the temperature of the lower section (lower reaction section) is 300°C, and the contact time is 25s.

[0081] Example 13

[0082] The operation steps and condition control in this embodiment are the same as in embodiment 1, except that the temperature of the upper section (upper reaction section) of the second reactor is 350°C, the temperature of the lower section (lower reaction section) is 350°C, and the contact time is 5s.

[0083] Example 14

[0084] When the preparation method of 2,3,3,3-tetrafluoropropylene shown in Example 1 was run continuously for 100 h (the yield decreased by 5% compared to the initial yield), the feedstock was cut off in this example, and a regeneration stream containing oxygen and an inert gas (nitrogen) was introduced into the reaction system. This regeneration stream contacted the catalysts packed in the first and second reactors for in-situ activation. The in-situ activation temperature was 300°C, and the time was 20 h. After regeneration, the control conditions were switched back to those shown in Example 1, and the preparation of 2,3,3,3-tetrafluoropropylene was continued.

[0085] Comparative Example 1 The operating steps and condition control of this comparative example are the same as those of Example 1, except that the catalyst used in the first reactor is replaced with a conventional chromium-containing gas-phase fluorination catalyst (Al2O3 / Cr, Cr loading rate 6%).

[0086] Comparative Example 2 The operating steps and conditions for this comparative example are the same as those for Example 1, except that the temperature of the first reactor is 280°C, the reaction pressure is 1 bar, and the contact time is 3 seconds.

[0087] Comparative Example 3 The operating steps and conditions for this comparative example are the same as those for Example 1, except that the temperature of the first reactor is 320°C, the reaction pressure is 0.1 bar, and the contact time is 10 seconds.

[0088] Comparative Example 4 The operating steps and conditions for this comparative example are the same as those for Example 1, except that the temperature of the first reactor is 240°C, the reaction pressure is set to 1.2 bar, and the contact time is 10 seconds.

[0089] Comparative Example 5 The operation steps and condition control of this comparative example are the same as those of Example 1. The difference is that after the reaction in the first reactor is completed, the subsequent first separation process is not carried out. Instead, all the material obtained from the first reactor is directly added to the second reactor for reaction.

[0090] Comparative Example 6 The operating steps and conditions for this comparative example are the same as those for Example 1, except that the temperature of the first reactor is 280°C, the reaction pressure is 1 bar, and the contact time is 25 seconds.

[0091] Comparative Example 7 The operating steps and condition control of this comparative example are the same as those of Example 1, except that the second reactor adopts a traditional single-stage fixed-bed reactor.

[0092] Comparative Example 8 The operating procedures and conditions for this comparative example are the same as those for comparative example 7, except that the temperature of the first reactor is set to 280°C, the reaction pressure is set to 1 bar, and the contact time is 15 seconds.

[0093] Table 1 shows the conversion rate and selectivity of 2,3,3,3-tetrachloropropene at the outlet of the first reactor of the above-described embodiments and comparative examples, as well as the conversion rate and selectivity of 2,3,3,3-tetrachloropropene at the outlet of the second reactor.

[0094] Table 1

[0095] As can be seen from the examples in Table 1 and Comparative Examples 2-4 and Comparative Example 6, suitable reaction temperature, pressure, and contact time can promote the catalytic activity of the chromium-free iron-based gas-phase fluorination catalyst. If the reaction temperature is insufficient, the active sites of the catalyst may not be fully activated, resulting in the incomplete conversion of the raw material 2,3,3,3-tetrachloropropylene (HCC-1230xf). If the temperature is too high, the side reactions may be aggravated, and the formation of non-target fluorinated products due to over-fluorination or the potential for molecular chain breakage due to local temperature unevenness may produce low-boiling-point byproducts.

[0096] Combining the results of Example 14 and Example 1, it is evident that the chromium-free iron-based gas-phase fluorination catalyst, after in-situ regeneration and activation, can still maintain high catalytic activity (conversion rate and selectivity). This confirms the effectiveness of the in-situ regeneration operation of this invention for secondary catalyst activation, namely, by removing surface carbon and metal impurities and reducing the crystal structure of the active component, significantly extending the catalyst's lifespan. In actual production, this technology can reduce the frequency of catalyst procurement, lower raw material costs by more than 30%, and simultaneously avoid fluctuations in reaction conditions caused by frequent catalyst replacement, ensuring long-term stable operation of the equipment.

[0097] As verified by combining Example 1 and Comparative Example 1, the specific chromium-free iron-based gas-phase fluorination catalyst used in this invention exhibits significantly better catalytic performance compared to traditional chromium-based catalysts. Specifically, the chromium-free iron-based gas-phase fluorination catalyst can achieve 100% conversion of HCC-1230xf, while the selectivity of the target product HFO-1234yf is as high as 99.5%; while the conversion rate of the chromium-containing catalyst is only 90.3% under the same conditions. Although the conversion rate of traditional chromium-containing catalysts can be improved by increasing the temperature, it will cause over-fluorination and cracking side reactions, resulting in an increase in low-boiling-point byproducts and a sharp drop in the selectivity of HFO-1234yf; while the chromium-free iron-based gas-phase fluorination catalyst, thanks to the oxygen storage capacity of rare earth additives, can effectively suppress carbon deposition and deep side reactions, and maintain higher stability at high temperatures.

[0098] Analysis of Comparative Example 5 shows that when the material from the first reactor outlet enters the second reactor directly without separation, the selectivity of the target product 2,3,3,3-tetrafluoropropylene (HFO-1234yf) decreases significantly, confirming that intermediate product purification and reactor design play a decisive role in selectivity. It is speculated that this may be due to the continuous accumulation of HCl concentration in the system as the fluorination reaction depth increases; HCl strongly adsorbs onto the active sites (such as Lewis acid sites) of the chromium-free iron-based gas-phase fluorination catalyst, forming stable metal chlorides, leading to permanent deactivation of the active sites; simultaneously, the presence of HCl accelerates catalyst surface sintering, increasing the specific surface area decay rate by more than 40%; and the organochlorine byproducts in the unseparated material undergo over-fluorination in the second reactor, generating high-boiling-point tar. This tar not only covers the catalyst active sites but also synergistically interacts with HCl, promoting pore blockage and reducing the effective diffusion channels of the catalyst. In Example 1 of this invention, by separating and removing HCl and organochlorine byproducts from the first reactor outlet, the risk of poisoning in the secondary reactor can be significantly reduced. Experiments show that the catalyst life of the second reactor is extended after separation, and the selectivity of HFO-1234yf is stabilized at 99.5%. The separated HCl can be used to produce electronic-grade hydrochloric acid or as a raw material for the chlor-alkali industry after deep purification (purity ≥99.9%); the organochlorine by-products can be used as flame retardant intermediates (such as hexachlorocyclopentadiene) after purification, thereby increasing the overall value-added rate of process by-products.

[0099] As demonstrated in Example 1 and Comparative Examples 7 and 8, the use of a two-stage reactor in the second step significantly improved the conversion rate of 2-chloro-3,3,3-trifluoropropene and the selectivity of 2,3,3,3-tetrafluoropropene. Its core advantage stems from segmented reaction control and efficient separation of intermediate products. Separate temperature control of the upper and lower reaction stages improved temperature precision, effectively suppressed excessive fluorination side reactions (such as the formation of HFC-245cb), and avoided the accumulation of tar precursors. High-purity feed combined with isothermal control in the two-stage reactor ensured that the selectivity of HFO-1234yf remained stable at 99.5%.

[0100] It should be noted that the above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention and should not be construed as limiting the specific implementation of the invention to these descriptions. For those skilled in the art, several simple modifications can be made without departing from the concept of the present invention, and all such modifications should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing 2,3,3,3-tetrafluoropropylene, characterized in that, The preparation method is carried out in a first reactor and a second reactor, and includes the following steps: (1) 2,3,3,3-tetrachloropropene and hydrogen fluoride are preheated and then fed into the first reactor to react and obtain the first material; (2) The first material is input into the first separation process; the first unreacted material obtained by separation is returned to the first reactor; the hydrogen chloride obtained by separation is purified by the acid production unit and output as hydrochloric acid product; the 2-chloro-3,3,3-trifluoropropene obtained by separation is input into the second reactor; (3) The newly introduced hydrogen fluoride reacts with 2-chloro-3,3,3-trifluoropropene in the second reactor to obtain the second material; (4) The second material is fed into the second separation process; the crude 2,3,3,3-tetrafluoropropylene obtained by separation is refined to obtain the 2,3,3,3-tetrafluoropropylene product, and the second unreacted material obtained by separation is returned to the second reactor; Both the first and second reactors are filled with a chromium-free iron-based gas-phase fluorination catalyst, which, based on 100 parts by weight of the support, comprises: 20-35 parts by weight of iron fluoride; 5 to 15 parts by weight of a first additive, wherein the first additive comprises a metal fluoride of one or more elements selected from titanium, tin, and antimony; 5-10 parts by weight of a second auxiliary agent, wherein the second auxiliary agent comprises one or more of calcium peroxide, strontium peroxide, magnesium peroxide, potassium permanganate, zinc peroxide, and sodium percarbonate; 1 to 5 parts by weight of adhesive, wherein the adhesive comprises one or two of aluminum dihydrogen phosphate and aluminum phosphate; 100 mass copies of the carrier.

2. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, In step (1), the preheating temperature of 2,3,3,3-tetrachloropropene is 200~300℃; And / or, the preheating temperature of hydrogen fluoride in step (1) is 200~300℃; And / or, the reaction temperature of the first reactor is 250~350℃, and the contact time is 5~20 seconds; And / or, the first reactor is a single-stage fixed-bed reactor; And / or, the pressure of the first reactor is 0.13 bar to 3.6 bar.

3. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The molar ratio of hydrogen fluoride to 2,3,3,3-tetrachloropropene in the first reactor is 4 to 10, preferably 5 to 8.

4. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The first separation process is carried out in a first distillation column and a second distillation column connected in series. The outlet of the first reactor is connected to the inlet of the first distillation column, and the bottom outlet of the first distillation column is connected to the inlet of the second distillation column. Hydrogen chloride is collected from the top of the first distillation column, and the first unreacted material is collected from the bottom of the second distillation column. The top outlet of the second distillation column is connected to the inlet of the second reactor. Preferably, the top temperature of the first distillation column is 20~40℃, the bottom temperature is 30~60℃, and the operating pressure is 1~3 bar; Preferably, the top temperature of the second distillation column is 50~70℃, the bottom temperature is 150~180℃, and the operating pressure is 5~8 bar.

5. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The acid production unit includes a shell-and-tube heat exchanger and a falling film absorption tower, from which high-concentration hydrochloric acid product is collected. Preferably, the outlet temperature of the shell-and-tube heat exchanger is -15°C to -35°C; Preferably, the temperature of the falling film absorption tower is 20~40℃ at the top and 30~50℃ at the bottom, and the operating pressure is 0.5~1.5 bar.

6. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The second reactor is a two-stage tubular fixed-bed reactor, comprising two reaction sections connected in series, with the second material being extracted from the outlet of the lower reaction section of the second reactor. Preferably, the reaction temperature in the upper section of the second reactor is 250~350℃, and the reaction temperature in the lower section is 300~350℃; the contact time in the second reactor is 5~25 seconds.

7. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The molar ratio of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropylene in the second reactor is 1 to 5, preferably 2 to 4.

8. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The second separation process is carried out in the third distillation column, and the outlet of the second reactor is connected to the inlet of the third distillation column; hydrogen chloride is collected from the top of the third distillation column. Preferably, the top temperature of the third distillation column is -30 to -10°C, the bottom temperature is 20 to 50°C, and the operating pressure is 10 to 20 bar. And / or, the purification operation of the crude 2,3,3,3-tetrafluoropropylene is carried out in a fourth distillation column; the bottom outlet of the third distillation column is connected to the inlet of the fourth distillation column; Preferably, the top temperature of the fourth distillation column is 40~70℃, the bottom temperature is 80~120℃, and the operating pressure is 5~15 bar.

9. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 1, characterized in that, The preparation of the chromium-free iron-based gas-phase fluorination catalyst includes the following steps: S1: The carrier is impregnated with an impregnation solution containing an iron source and a first auxiliary precursor, and then dried, calcined and granulated to obtain the first catalyst precursor; S2: The first catalyst precursor is fluorinated by contacting a fluorine source to obtain the second catalyst precursor; S3: The second auxiliary agent and binder are mixed in a solvent to obtain a slurry; the slurry is mixed evenly with the second catalyst precursor and then dried to obtain the chromium-free iron-based gas-phase fluorination catalyst.

10. The method for preparing 2,3,3,3-tetrafluoropropylene according to any one of claims 1 to 9, characterized in that, The preparation method further includes: when the reaction yield decreases to a set threshold, cutting off the raw material and introducing a regeneration stream containing an oxidant, and activating the chromium-free iron-based gas-phase fluorination catalyst in situ at 210~410℃ for 0.8~20h. Preferably, the in-situ activation temperature is 260~360℃; Preferably, the in-situ activation time is 1–15 hours; Preferably, the regeneration stream is a mixture of oxygen and an inert gas.

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