A method for preparing 2,3,3,3-tetrafluoropropylene by co-cracking tetrafluorodichloroethane and methane in one step

Abstract

The present invention discloses a method for preparing 2,3,3,3-tetrafluoropropylene by co-cracking tetrafluorodichloroethane and methane in one step, wherein the catalyst is loaded into a nickel tube fixed bed reactor. The catalyst is first pretreated with N2 at 300-400°C. Tetrafluorodichloroethane and methane feed gas are then introduced, and the flow ratio of tetrafluorodichloroethane to methane is set to 1:1-10, and the catalyst bed temperature is 350-550°C. The present invention uses tetrafluorodichloroethane with high GWP, high ODP value and long atmospheric life and CH4, which is also a greenhouse gas, as raw materials for the first time, and converts them into a new generation of automotive refrigerant HFO-1234yf. The present invention not only has a simple process and protects the environment, but the prepared catalyst also has a simple preparation method and extremely high catalytic activity and selectivity.

Description

Technical Field

[0001] The present invention relates to a new route for synthesizing 2,3,3,3-tetrafluoropropene, and in particular to a method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step. Background Art

[0002] 2,3,3,3-tetrafluoropropene, with the molecular formula CF3CFCH2, also known as HFO-1234yf or R1234yf, is a fourth-generation, environmentally friendly refrigerant. HFO-1234yf has an ODP of 0 and an extremely low GWP of approximately 4, far lower than 1,1,1,2-tetrafluoroethane (HFC-134a, GWP = 1300), currently widely used in the refrigerant industry. HFO-1234yf has an atmospheric lifetime of only 11 days. Studies have shown that 2,3,3,3-tetrafluoropropene eventually degrades in the atmosphere through oxidation to trifluoroacetic acid (TFA), a low-toxic, harmless compound. In addition to its use as a refrigerant, HFO-1234yf can also be used as a biocide carrier, foam blowing agent, aerosol propellant, circulating fluid, and fire extinguishing agent.

[0003] Based on the raw materials, traditional HFO-1234yf synthesis methods primarily involve alkyl halide elimination and olefin halide addition reactions. The most typical synthesis methods involve two-step hydrogenation of olefin halide followed by HF removal to produce HFO-1234yf, or direct addition of olefin halide to HF followed by HCl removal to produce HFO-1234yf. For example, 1,1,2,3-tetrachloropropene is treated with HF to produce 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), followed by 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), which is then dehydrated to produce HFO-1234yf. Another example is hexafluoropropylene, which is treated with two-step hydrogenation and HF removal to produce HFO-1234yf. Since liquid-phase fluorination is commonly used in industry, it requires the use of large amounts of caustic soda, resulting in significant environmental pollution.

[0004] Both methane and tetrafluoroethylene (CFC-114) are listed as major greenhouse gases in the Kyoto Protocol. Because CFC-114 contains chlorine atoms, its emissions contribute to stratospheric ozone depletion and the intensification of the greenhouse effect. Both the Montreal Protocol and the Kyoto Protocol encourage the effective treatment of these fluorinated gases. Currently, the main treatment methods for CFC-114 are high-temperature incineration and plasma treatment. However, high-temperature treatment consumes significant energy and is costly, and the incineration products, HF and HCl, can corrode equipment and cause environmental pollution. Plasma treatment, on the other hand, produces highly toxic substances during the process, requiring high equipment and incurring significant costs. Therefore, resource recovery of chlorofluorocarbons (CFCs) into high-value-added products is the most beneficial approach.

[0005] Chinese patent CN 103691430A developed a conversion route for the hydrodechlorination of tetrafluorodichloroethane to primarily tetrafluoromonochloroethane and tetrafluoroethane. However, the reaction products are still fluorinated gases that significantly damage the ozone layer and contribute to the greenhouse effect, and cannot be used to create new, high-value, environmentally friendly refrigerants. Summary of the Invention

[0006] In view of the shortcomings of the existing technology and from the perspective of environmental protection, the present invention aims to provide a method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step. The method uses eliminated harmful tetrafluorodichloroethane and methane as raw materials to synthesize a high-value-added 2,3,3,3-tetrafluoropropene refrigerant, turning waste into treasure. While protecting the environment, the production cost of 2,3,3,3-tetrafluoropropene is reduced. The process of the route is simple, and the catalyst used has high reaction selectivity, high conversion rate, and good stability.

[0007] This method uses a fixed-bed reactor with gas-solid catalysis to co-crackle CFC-114 and methane to produce high-value-added HFO-1234yf in a single step. The specific reactions are shown in formulas (1) to (4). This route converts low-value-added CFC-114 into high-value-added HFO-1234yf for the first time, and has good industrial application prospects and extremely high environmental value. The method of the present invention for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in a single step comprises adding a catalyst to a fixed-bed reactor, raising the temperature to the catalytic reaction temperature, and introducing tetrafluorodichloroethane and methane at normal pressure to react to produce 2,3,3,3-tetrafluoropropene. The product is detected online by GC-MS, and the conversion rate and target product selectivity are calculated.

[0008] CH4→CH3·+H (1)

[0009] CF3CFCl2→CF3CFCl·+Cl (2)

[0010] CF3CFCl·+CH3·→CF3CFClCH3 (3)

[0011] CF3CFClCH3→CF3CFCH2+HCl (4)

[0012] The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step uses lanthanum fluoride doped with the element O as a catalyst. The catalyst is loaded into a nickel tube reactor, first heated to a pretreatment temperature and N2 gas is introduced to pre-treat the catalyst, then heated to a catalytic cracking temperature and tetrafluorodichloroethane is introduced to carry out a co-cracking reaction with methane to prepare 2,3,3,3-tetrafluoropropene.

[0013] Furthermore, the catalyst is prepared by reacting a lanthanum source and a fluorine source as raw materials to generate lanthanum fluoride LaF3, and then calcining the lanthanum fluoride catalyst at 350-450°C for 2-6 hours under an O2 atmosphere to obtain an O-doped lanthanum fluoride catalyst, which is referred to as catalyst LaOF.

[0014] Furthermore, the lanthanum source is at least one of La(NO3)3, La2O3, La2(CO3)3, La2(SO4)3, and LaCl3, and the fluorine source is one of NH4HF2, HF solution, CHClF2, and PVDF.

[0015] Furthermore, when lanthanum fluoride LaF3 is prepared by precipitation method, the fluorine source is selected from NH4HF2 or HF solution. The preparation process is as follows: the lanthanum source and the fluorine source are stirred together in deionized water, stirred at 60-120°C for 4-12 hours, and the lanthanum source and the fluorine source react to generate LaF3 precipitate, which is then centrifuged, washed, and dried to prepare lanthanum fluoride LaF3.

[0016] Furthermore, when lanthanum fluoride LaF3 is prepared by precipitation method, PVDF is selected as the fluorine source. The preparation process is as follows: the lanthanum source and the fluorine source are added to N,N-dimethylformamide solvent, stirred under heating conditions in a water bath to form a transparent colloid, and then placed in a 115-130°C forced air drying oven for drying to prepare lanthanum fluoride LaF3.

[0017] Furthermore, when lanthanum fluoride LaF3 is prepared by ball milling, the fluorine source is NH4HF2 or PVDF, and the preparation process is: the lanthanum source and the fluorine source are placed in a ball mill according to a mass ratio of 1:2.5 to 5, and ball milling is performed at a ball mill speed of 120-180 r / min and a ball milling time of 2-4 h to prepare lanthanum fluoride LaF3.

[0018] Furthermore, when lanthanum fluoride LaF3 is prepared by a vapor phase calcination method, the fluorine source is CHClF2, and the preparation process is: placing the lanthanum source in a tubular furnace, introducing a vapor phase fluorine source, and calcining at 500-700°C for 2-8h to prepare lanthanum fluoride LaF3.

[0019] Furthermore, the temperature of the co-cracking reaction is 350-550°C, preferably 380-470°C.

[0020] Furthermore, the feed volume flow ratio of tetrafluorodichloroethane to methane is 1:1-10, preferably 1:3-5; based on a catalyst loading of 2 mL, the feed volume flow rate of tetrafluorodichloroethane is 10-90 mL / min, preferably 30 mL-70 mL; the space velocity of the entire reaction is 600 h -1 ~29700h -1 , preferably 3600h -1 ~12600h -1 .

[0021] Further, the catalyst is pretreated with N2, the pretreatment temperature is 200-500°C, and the activation time is 2-10 hours. The pretreatment temperature is preferably 300-400°C, and the activation time is preferably 4-8 hours.

[0022] Compared with the prior art, the greatest advantages of the present invention are:

[0023] 1) The present invention prepares LaF3 catalysts using precipitation, mechanical ball milling, and vapor-phase calcination. Specifically, the LaOF catalyst is calcined in O2. The introduction of oxygen atoms improves the catalyst's resistance to sintering and carbonization, while also creating more defects that promote the conversion of methane to methyl groups. The catalyst preparation cycle is short, the method is simple, and reproducible, resulting in stable catalyst performance with high activity and selectivity.

[0024] 2) This invention pioneers a one-step route to produce 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane. This invention offers the advantage of a one-step synthesis of the environmentally friendly fourth-generation refrigerant HFO-1234yf. The process eliminates the need for multiple reactions, making it simple and rapid. It also reduces industrial energy consumption and the extensive use of caustic soda. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the activity and selectivity of the catalysts LaOF and LaF3(N2) in Example 4 of the present invention compared with other catalysts. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited thereto. Any equivalent replacement or modification of the technical solution and inventive concept of the present invention shall fall within the scope of protection of the present invention.

[0027] Example 1

[0028] Weigh 6.48g of La(NO₃)₃ and dissolve it in 30mL of deionized water. Transfer the mixture to a round-bottom flask. Then slowly add 6.24g of NH₄HF₂ dissolved in 30mL of deionized water. Incubate in an oil bath at 60°C for 4 hours. The resulting LaF₃ precipitate is centrifuged, washed, dried, and the catalyst collected. Calcined in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF₃ catalyst. Press the pellets, crush them, and sieve them using a 20-40 mesh sieve.

[0029] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 350°C and an N2 flow rate of 10 mL / min for 2 h. A mixture of tetrafluoroethylene dichloroethane and methane was then introduced at a gas volume flow ratio of 1:1, with the tetrafluoroethylene dichloroethane flow rate of 10 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 600 h -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 55% conversion of tetrafluorodichloroethane and an 88% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0030] The LaOF catalyst of the present invention requires heating pretreatment by introducing N2 before use in catalytic reactions. This pretreatment removes impurities such as physically adsorbed water from the catalyst surface. Nitrogen also acts as a diluent, extending the catalyst's lifespan and preventing sintering. Direct introduction of tetrafluoroethylene dichloroethane and methane feed gases without N2 pretreatment has been shown to accelerate catalyst sintering and carbon deposition, leading to a decrease in catalyst conversion and shortened catalyst lifespan.

[0031] Example 2

[0032] Weigh 6.48g of La(NO₃)₃ and dissolve it in 30mL of deionized water. Transfer the mixture to a round-bottom flask, then slowly add 6.24g of NH₄HF₂ dissolved in 30mL of deionized water. Incubate in an oil bath at 60°C for 4 hours. The resulting LaF₃ precipitate is centrifuged, washed, dried, and the catalyst collected. Calcinate the precipitate in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF₃ catalyst. Press the pellets, crush them, and sieve them using a 20-40 mesh sieve.

[0033] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 500°C and an N2 flow rate of 10 mL / min. The pretreatment time was 4 hours, and the temperature was raised to the catalyst reaction temperature of 550°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:10, with tetrafluoroethylene dichloroethane at 90 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 29700 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 50% conversion of tetrafluorodichloroethane and an 87% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0034] Example 3

[0035] Weigh 6.48g of La(NO₃)₃ and dissolve it in 30mL of deionized water. Transfer the mixture to a round-bottom flask, then slowly add 6.24g of NH₄HF₂ dissolved in 30mL of deionized water. Incubate in an oil bath at 60°C for 4 hours. The resulting LaF₃ precipitate is centrifuged, washed, dried, and the catalyst collected. Calcinate the precipitate in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF₃ catalyst. Press the pellets, crush them, and sieve them using a 20-40 mesh sieve.

[0036] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 300°C and an N2 flow rate of 10 mL / min. The pretreatment time was 4 hours, and the temperature was raised to the catalyst reaction temperature of 380°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:3, with tetrafluoroethylene dichloroethane at 30 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 3600 h / min. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 66% conversion of tetrafluorodichloroethane and an 87% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0037] Example 4

[0038] Weigh 6.5g of La₂O₃ and 18.2g of NH₄HF₂ and mix them equally between two ball mills, achieving a ball-to-material ratio of 4:1. Mill at a speed of 150 r / min for 3 hours. After milling, collect the catalyst and calcine it in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF catalyst. Press the pellets, crush them, and sieve them with a 20-40 mesh sieve.

[0039] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 400°C and a N2 flow rate of 10 mL / min. The pretreatment time was 8 hours, and the temperature was raised to the catalyst reaction temperature of 470°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:5, with tetrafluoroethylene dichloroethane at 70 mL / min. The reaction pressure was atmospheric pressure for 12600 h. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 70% conversion of tetrafluorodichloroethane and an 85% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0040] Comparison of the conversion of tetrafluorodichloroethane and the selectivity of the target product 2,3,3,3-tetrafluoropropene in the co-cracking reaction of tetrafluorodichloroethane and methane catalyzed by LaOF, LaF3(N2) and SrF2 in Example 4 of the present invention. Figure 1 It can be seen that the conversion rate of the catalyst LaOF in Example 4 of the present invention increases steadily within the first 15 hours of the catalytic reaction. After the active sites are fully exposed, the conversion rate stabilizes after 15 hours of the catalytic reaction. The early stage of the catalytic reaction is the induction period of the catalyst, and the conversion rate gradually stabilizes in the later period.

[0041] Figure 1 The preparation method of the LaF3(N2) catalyst is the same as the preparation method of the catalyst LaOF in Example 4 of the present invention. The only difference is that "calcination under O2 atmosphere is replaced by calcination under N2 atmosphere". SrF2 is a commercially available catalyst. The catalytic effects of both are obviously inferior to the catalyst LaOF of the present invention.

[0042] Example 5

[0043] Weigh 6.5g of La₂O₃ and 18.2g of NH₄HF₂ and mix them equally between two ball mills, achieving a ball-to-material ratio of 4:1. Mill at a speed of 150 r / min for 3 hours. After milling, collect the catalyst and calcine it in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF catalyst. Press the pellets, crush them, and sieve them with a 20-40 mesh sieve.

[0044] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 350°C and an N2 flow rate of 10 mL / min. The pretreatment time was 6 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 50 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 7500 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 67% conversion of tetrafluorodichloroethane and an 83% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0045] Example 6

[0046] Weigh 13.71 g of La2(CO3)3, dissolve it in 60 mL of deionized water, and transfer it to a round-bottom flask. Slowly add 20 mL of 40% HF solution dropwise to form a precipitate. Treat in an oil bath for 12 hours at 120°C. The resulting LaF3 precipitate is centrifuged, washed, dried, and the catalyst collected. This precipitate is then calcined in a tube furnace at 400°C under an O2 atmosphere for 4 hours to obtain the LaOF catalyst. This is then pelletized, crushed, and sieved using a 20-40 mesh sieve.

[0047] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 200°C and a N2 flow rate of 10 mL / min. The pretreatment time was 10 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 50 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 7500 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 64% conversion of tetrafluorodichloroethane and an 88% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0048] Example 7

[0049] Weigh 13.71 g of La2(CO3)3, dissolve it in 60 mL of deionized water, and transfer it to a round-bottom flask. Slowly add 20 mL of 40% HF solution dropwise to form a precipitate. Treat in an oil bath for 12 hours at 120°C. The resulting LaF3 precipitate is centrifuged, washed, dried, and the catalyst collected. This precipitate is then calcined in a tube furnace at 400°C under an O2 atmosphere for 4 hours to obtain the LaOF catalyst. This is then pelletized, crushed, and sieved using a 20-40 mesh sieve.

[0050] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 350°C and an N2 flow rate of 10 mL / min. The pretreatment time was 10 h, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 90 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 13500 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 54% conversion of tetrafluorodichloroethane and an 87% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0051] Example 8

[0052] Weigh 13.71 g of La2(CO3)3, dissolve it in 60 mL of deionized water, and transfer it to a round-bottom flask. Slowly add 20 mL of 40% HF solution dropwise to form a precipitate. Treat in an oil bath for 12 hours at 120°C. The resulting LaF3 precipitate is centrifuged, washed, dried, and the catalyst collected. This precipitate is then calcined in a tube furnace at 400°C under an O2 atmosphere for 4 hours to obtain the LaOF catalyst. This is then pelletized, crushed, and sieved using a 20-40 mesh sieve.

[0053] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 350°C and an N2 flow rate of 10 mL / min. The pretreatment time was 10 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 90 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 13500 h / min. -1After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 58% conversion of tetrafluorodichloroethane and an 84% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0054] Example 9

[0055] Weigh 11.36g of La2(SO4)3 into a quartz boat and transfer it to a tube furnace. Calcine at 600°C for 6 hours with a CHClF2 gaseous fluorine source at a controlled flow rate of 40mL / min. Cool to room temperature and collect the catalyst. Calcine it in a tube furnace at 400°C for 4 hours under an O2 atmosphere to obtain the LaOF catalyst. Press it into pellets, crush it, and sieve it with a 20-40 mesh sieve.

[0056] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 380°C and an N2 flow rate of 10 mL / min. The pretreatment time was 6 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 50 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 7500 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 55% conversion of tetrafluorodichloroethane and an 86% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0057] Example 10

[0058] Weigh 11.36g of La2(SO4)3 into a quartz boat and transfer it to a tube furnace. Calcine at 600°C for 6 hours with a CHClF2 gaseous fluorine source at a controlled flow rate of 40mL / min. Cool to room temperature and collect the catalyst. Calcine it in a tube furnace at 400°C for 4 hours under an O2 atmosphere to obtain the LaOF catalyst. Press it into pellets, crush it, and sieve it with a 20-40 mesh sieve.

[0059] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under N2 atmosphere at a temperature of 380°C and an N2 flow rate of 10 mL / min. The pretreatment time was 7 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 70 mL / min. The reaction pressure was atmospheric pressure, and the space velocity was 10500 h -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 60% conversion of tetrafluorodichloroethane and an 87% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0060] Example 11

[0061] Weigh 11.36g of La2(SO4)3 into a quartz boat and transfer it to a tube furnace. Calcine at 600°C for 6 hours with a CHClF2 gaseous fluorine source at a controlled flow rate of 40mL / min. Cool to room temperature and collect the catalyst. Calcine it in a tube furnace at 400°C for 4 hours under an O2 atmosphere to obtain the LaOF catalyst. Press it into pellets, crush it, and sieve it with a 20-40 mesh sieve.

[0062] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 380°C and an N2 flow rate of 10 mL / min. The pretreatment time was 7 hours, and the temperature was raised to the catalyst reaction temperature of 400°C. A mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:4, with tetrafluoroethylene dichloroethane at 70 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 10500 h -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 63% conversion of tetrafluorodichloroethane and an 87% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0063] Example 12

[0064] Weigh 9.81g of LaCl₃ and dissolve it in 500mL of N,N-dimethylformamide. Heat the mixture in a water bath. Gradually add 56g of PVDF to the heated solution while stirring. Dry the homogenized, transparent colloid in a 120°C forced air drying oven and collect the catalyst. Calcinate the mixture in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF catalyst. Press the pellets, crush them, and sieve them using a 20-40 mesh sieve.

[0065] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under N2 atmosphere at a temperature of 350°C and a N2 flow rate of 10 mL / min for 4 hours. After the temperature was raised to the catalyst reaction temperature of 400°C, a mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:8, with tetrafluoroethylene dichloroethane at 60 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 16200 h -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 58% conversion of tetrafluorodichloroethane and an 85% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0066] Example 13

[0067] Weigh 9.81g of LaCl₃ and dissolve it in 500mL of N,N-dimethylformamide. Heat the mixture in a water bath. Gradually add 56g of PVDF to the heated solution while stirring. Dry the homogenized, transparent colloid in a 120°C forced air drying oven and collect the catalyst. Calcinate the mixture in a tube furnace at 400°C under an O₂ atmosphere for 4 hours to obtain the LaOF catalyst. Press the pellets, crush them, and sieve them using a 20-40 mesh sieve.

[0068] In a fixed-bed reactor equipped with a gas chromatography-mass spectrometry system, 2 mL of LaOF catalyst was first loaded and pretreated under a N2 atmosphere at a temperature of 400°C and a N2 flow rate of 10 mL / min for 6 hours. After the pretreatment, a mixture of tetrafluoroethylene dichloroethane and methane was introduced at a gas volume flow ratio of 1:8, with tetrafluoroethylene dichloroethane at 50 mL / min. The reaction pressure was atmospheric pressure and the space velocity was 13500 h-1. -1 After chromatographic online monitoring, samples were taken and analyzed 30 hours after the reaction, revealing a 60% conversion of tetrafluorodichloroethane and an 86% selectivity for the target product, 2,3,3,3-tetrafluoropropene. The remainder consisted of CF3CClCH2 (HFO-1233xf). The selectivity remained essentially unchanged within 30-50 hours of the catalytic reaction, with little decrease in conversion.

[0069] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the examples.

Claims

1. A method for preparing 2,3,3,3-tetrafluoropropylene by co-cracking tetrafluorodichloroethane and methane in one step, characterized in that Lanthanum fluoride is used as a catalyst, and the catalyst is loaded into a nickel tube reactor. It is first heated to a pretreatment temperature and N2 gas is introduced to pretreat the catalyst. Then, it is heated to a catalytic cracking temperature and tetrafluorodichloroethane CF3CFCl2 is introduced to perform a co-cracking reaction with methane to prepare 2,3,3,3-tetrafluoropropylene. The catalyst is lanthanum fluoride doped with oxygen element. The preparation method is as follows: a lanthanum source and a fluorine source are used as raw materials to react to generate lanthanum fluoride LaF3, and then the lanthanum fluoride is calcined at 350-450°C for 2-6 hours in an oxygen atmosphere to obtain a lanthanum fluoride catalyst doped with oxygen element, which is recorded as catalyst LaOF.

2. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 1, characterized in that The lanthanum source is at least one of La(NO3)3, La2O3, La2(CO3)3, La2(SO4)3, and LaCl3, and the fluorine source is one of NH4HF2, HF solution, CHClF2, and PVDF.

3. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 2, characterized in that When lanthanum fluoride LaF3 is prepared by precipitation method, NH4HF2 or HF solution is selected as the fluorine source. The preparation process is as follows: the lanthanum source and the fluorine source are stirred together in deionized water, stirred at 60-120°C for 4-12 hours, and the lanthanum source and the fluorine source react to form LaF3 precipitate, which is then centrifuged, washed, and dried to prepare lanthanum fluoride LaF3.

4. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 2, characterized in that When lanthanum fluoride LaF3 is prepared by precipitation method, PVDF is selected as the fluorine source. The preparation process is as follows: the lanthanum source and the fluorine source are added to N,N-dimethylformamide solvent, stirred under heating conditions in a water bath to form a transparent colloid, and then placed in a 115-130°C forced air drying oven for drying to prepare lanthanum fluoride LaF3.

5. The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 2, characterized in that When lanthanum fluoride LaF3 is prepared by ball milling, the fluorine source is NH4HF2 or PVDF. The preparation process is as follows: the lanthanum source and the fluorine source are placed in a ball mill according to a mass ratio of 1:2.5~5, and ball milling is performed at a ball mill speed of 120-180r / min and a ball milling time of 2-4h to prepare lanthanum fluoride LaF3.

6. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step as claimed in claim 2, characterized in that When lanthanum fluoride LaF3 is prepared by vapor phase calcination method, the fluorine source is CHClF2, and the preparation process is as follows: the lanthanum source is placed in a tube furnace, a vapor phase fluorine source is introduced, and calcined at 500-700°C for 2-8h to prepare lanthanum fluoride LaF3.

7. The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 1, characterized in that The temperature of the co-cracking reaction is 350-550°C.

8. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 7, characterized in that The temperature of the co-cracking reaction is 380°C~470°C.

9. The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 1, characterized in that The feed volume flow ratio of tetrafluorodichloroethane to methane is 1:1~10; based on a catalyst loading of 2mL, the feed volume flow rate of tetrafluorodichloroethane is 10~90mL / min; The space velocity of the entire reaction is 600h -1 ~29700h -1 .

10. A method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 9, characterized in that The feed volume flow ratio of tetrafluorodichloroethane to methane is 1:3~5; based on a catalyst loading of 2mL, the feed volume flow rate of tetrafluorodichloroethane is 30mL~70mL; The space velocity of the entire reaction is 3600h -1 ~12600h -1 .

11. The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 1, wherein: The catalyst is pretreated with N2 at a pretreatment temperature of 200 to 500°C and an activation time of 2 to 10 hours.

12. The method for preparing 2,3,3,3-tetrafluoropropene by co-cracking tetrafluorodichloroethane and methane in one step according to claim 11, characterized in that: The catalyst was pretreated with N2 at a pretreatment temperature of 300°C to 400°C and an activation time of 4 to 8 hours.

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