Preparation method of chromium-based composite catalyst and application thereof

Abstract

The application provides a chromium-based composite catalyst preparation method and application thereof, and belongs to fluorine chemical technology, wherein the chromium-based composite catalyst preparation method comprises the following steps: S1: dissolving chromium salt, soluble salt corresponding to an auxiliary component metal and fluorine-containing polymer in deionized water, stirring and dissolving, then adding a precipitant and continuing to stir for a set time to obtain a precipitate mixture; S2: loading the precipitate mixture obtained in the step S1 into a centrifugal container, centrifugally washing, drying, and then high-temperature calcining to obtain a composite metal oxide. The chromium oxide catalyst is prepared by using the precipitation method, fluorine-containing polymer is used as a fluorine source, hydrogen fluoride is decomposed and released in the calcining process, and thus the in-situ fluorination of the metal is prepared in one step, and the prepared catalyst has the advantages of simple preparation method, large specific surface area and high stability.

Description

[Technical Field]

[0001] This invention belongs to the field of fluorochemical technology, specifically relating to a method for preparing chromium-based composite catalysts. [Background Technology]

[0002] HFO-1234ze (1,3,3,3-tetrafluoropropylene) is non-flammable, with an ODP value of 0 and a GWP value of 6. Studies have found that HFO-1234ze is considered the most promising next-generation refrigerant to replace HFC-134a, and therefore has a very promising application prospect.

[0003] Currently, the synthesis of HFO-1234ze mainly includes the dehydrofluorination method using 1,1,1,3,3-pentafluoropropane (HFC-245fa) as a raw material, the direct addition method of trifluoropropyne, the direct substitution method of trifluorochloropropene, and the thermal cracking method. Among them, the synthetic route for preparing HFO-1234ze by catalytic gas-phase dehydrofluorination of HFC-245fa is simple and has a high yield of the target product, making it the synthetic route with the greatest development potential.

[0004] Patent CN103537305B discloses a Ni-Ag-Cr2O3-AlF3 catalyst for defluorination to co-produce 1,3,3,3-tetrafluoropropylene and 2,3,3,3-tetrafluoropropylene. The reaction temperature is 400℃, and the conversion rate of HFC-245fa is 98.5% with a selectivity of 90%, but a high reaction temperature is required.

[0005] Patent US5986151A uses the precious metal palladium as a catalyst and reacts at 470°C. The selectivity and conversion rate are both over 90%, but the precious metal raw material is expensive.

[0006] Patent CN109499590A uses the sol-gel method to load the active component onto a magnesium fluoride support, thereby increasing the specific surface area and maintaining the conversion rate of 245fa above 70%. However, the catalyst preparation process requires fluorination with hydrofluoric acid solution, which is complex and dangerous.

[0007] The catalysts used in the existing technology for the preparation of 1,3,3,3-tetrafluoropropylene from 1,1,1,3,3-pentafluoropropane by defluorination have disadvantages such as high reaction temperature, complex preparation process, and expensive raw materials. [Summary of the Invention]

[0008] To address the problems existing in the prior art, this invention provides a method for preparing a chromium-based composite catalyst and its application, which reduces costs and simplifies the preparation process.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] First, this invention provides a method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis, comprising the following steps:

[0011] S1: Dissolve the chromium salt, the soluble salt corresponding to the metal component of the auxiliary agent, and the fluorinated polymer in deionized water, stir to dissolve, add the precipitant and continue stirring for a set time to obtain a precipitated mixture.

[0012] The mass ratio of the chromium salt, the soluble salt corresponding to the auxiliary metal component, and the fluoropolymer is 1:0.05-0.2:0.05-0.2. The auxiliary metal component includes Zn, Al, Mg, La, Ni, Co, Mn, and Y.

[0013] S2: The precipitate mixture obtained in step S1 is placed in a centrifuge container, centrifuged, washed, and dried, and then calcined at high temperature to obtain the composite metal oxide.

[0014] Preferably, the soluble salt corresponding to the metal component of the auxiliary agent is any one or a combination of at least two of chloride, nitrate, acetate and carbonate.

[0015] Preferably, the fluoropolymer is any one or a combination of at least two of PVDF, PTFE, PVF, PTrFE and FEP.

[0016] Preferably, the precipitant is any one of sodium hydroxide, ammonia, and potassium hydroxide.

[0017] Preferably, the mass ratio of the chromium salt, the soluble salt corresponding to the metal auxiliary component, and the fluoropolymer is 1:0.1:0.1.

[0018] Preferably, in step S1, the mixture is stirred using a constant pressure heat-collecting stirrer at a water bath temperature of 25-35℃, with a stirring speed of 300-500 r / min and a stirring time of 10-40 min, and then a precipitant is added and stirring is continued for 0.5-5 h.

[0019] Preferably, the roasting atmosphere in step S2 is a mixture of O2 and N2, wherein the O2 content is 1-10%.

[0020] Preferably, in step S2, the calcination temperature is 300-500℃, the calcination time is 5-10h, and the calcination heating rate is 1-10℃ / min.

[0021] In another aspect, the present invention also provides a method for preparing 1,3,3,3-tetrafluoropropylene by dehydrofluorination of 1,1,1,3,3-pentafluoropropane, wherein a catalyst is used in the preparation process, and the catalyst is a chromium-based composite catalyst prepared by the above method.

[0022] The technical solution adopted in this invention uses a precipitation method to prepare chromium oxide catalyst, utilizing a fluoropolymer as a fluorine source. During the calcination process, hydrogen fluoride is released through decomposition, thereby achieving in-situ fluorination of the metal in one step. This method has the advantages of simple preparation method, large specific surface area of ​​the prepared catalyst, and high stability.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The catalyst is synthesized by co-precipitation of multiple soluble inorganic metal salts, without the use of precious metals, which significantly reduces the preparation cost of the catalyst and the synthesis route is simple.

[0025] (2) This invention does not require the use of a mixture of inert gas and hydrogen fluoride to fluorinate the precursor. It only requires one calcination step to obtain the fluorinated and activated chromium-based composite catalyst, which significantly shortens the fluorination time. The process is simple, has few operation steps, generates less organic waste liquid, has high preparation efficiency, and is green and environmentally friendly.

[0026] (3) The chromium-based composite catalyst prepared by the present invention using fluoropolymer as fluorine source has high catalytic activity and good stability in the HFC-245fa deHF to prepare HFO-1234ze reaction, and can run continuously and stably in a fixed bed reactor for 1000h.

[0027] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments. [Attached Image Description]

[0028] Figure 1 This is the catalyst lifetime evaluation activity diagram for Example 14.

Detailed Implementation Methods

[0029] The technical solution of the present invention will be explained and described below with reference to the embodiments of the present invention. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0030] This invention provides a method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis, comprising the following steps:

[0031] S1: Dissolve the chromium salt, the soluble salt corresponding to the metal component of the auxiliary agent, and the fluorinated polymer in deionized water, stir to dissolve, add the precipitant and continue stirring for a set time to obtain a precipitated mixture.

[0032] The mass ratio of the chromium salt, the soluble salt corresponding to the auxiliary metal component, and the fluoropolymer is 1:0.05-0.2:0.05-0.2. Catalysts prepared at this ratio exhibit better activity than those prepared from chromium salt alone, for example, 1:0.1:0.1. The auxiliary metal component includes Zn, Al, Mg, La, Ni, Co, Mn, and Y.

[0033] S2: The precipitate mixture obtained in step S1 is placed in a centrifuge container, centrifuged, washed, and dried, and then calcined at high temperature to obtain the composite metal oxide.

[0034] Preferably, the soluble salt corresponding to the metal component of the auxiliary agent is any one or a combination of at least two of chloride, nitrate, acetate, and carbonate. The fluoropolymer is any one or a combination of at least two of PVDF, PTFE, PVF, PTrFE, and FEP. The precipitant is any one of sodium hydroxide, ammonia, and potassium hydroxide.

[0035] In step S1, stir the mixture using a constant temperature heat collector at a water bath temperature of 25-35℃ to ensure uniform mixing. The stirring speed is 300-500 r / min and the time is 10-40 min. Then add the precipitant and continue stirring for 0.5-5 h.

[0036] In step S2, the calcination atmosphere is a mixture of O2 and N2, with the O2 content being 1-10% by volume. The calcination temperature is 300-500℃, the calcination time is 5-10h, and the calcination heating rate is 1-10℃ / min.

[0037] In addition, the method described above is used to prepare a chromium-based composite catalyst for the defluorination of 1,1,1,3,3-pentafluoropropane to prepare 1,3,3,3-tetrafluoropropylene.

[0038] Example 1

[0039] Chromium chloride, different types of auxiliary components, and PVDF powder were weighed and dissolved in 600 mL of deionized water according to a Cr, M, and PVDF mass ratio of 1:0.1:0.05. The mixture was stirred for 3 h at 400 r / min using a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol using a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h at a heating rate of 2 °C / min in a 1% O2 / N2 mixed gas to obtain a chromium-based composite catalyst.

[0040] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0041] Example 2

[0042] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.1:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0043] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0044] Example 3

[0045] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0046] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0047] Example 4

[0048] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 10 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0049] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0050] Example 5

[0051] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Sodium hydroxide was added until the pH was 9.0 and stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0052] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0053] Example 6

[0054] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 5% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0055] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0056] Example 7

[0057] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 10% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0058] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0059] Example 8

[0060] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 4 °C / min to obtain a chromium-based composite catalyst.

[0061] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0062] Example 9

[0063] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 10 °C / min to obtain a chromium-based composite catalyst.

[0064] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0065] Example 10

[0066] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a Cr:La:FEP mass ratio of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was then washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0067] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0068] Example 11

[0069] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a Cr:La:PTFE mass ratio of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0070] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0071] Example 12

[0072] Chromium chloride, lanthanum chloride, magnesium chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to the mass ratio of Cr, La, Mg, and PTFE of 1:0.02:0.03:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0073] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0074] Example 13

[0075] Chromium chloride, lanthanum chloride, zinc chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to the mass ratio of Cr, La, Zn, and PTFE of 1:0.02:0.03:0.2. The mixture was stirred for 3 h at 400 r / min using a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol using a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h at a heating rate of 2 °C / min in a 1% O2 / N2 mixed gas to obtain a chromium-based composite catalyst.

[0076] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃. Samples were taken for analysis after 50 hours of reaction.

[0077] Example 14

[0078] Chromium chloride, lanthanum chloride, and PVDF were weighed and dissolved in 600 mL of deionized water according to a mass ratio of Cr, La, and PVDF of 1:0.05:0.2. The mixture was stirred at 400 r / min for 3 h in a constant pressure heat-collecting stirrer at 30 °C. Ammonia was added until the pH reached 9.0, at which point stirring was stopped. The suspension was washed 3-4 times with deionized water and ethanol in a high-speed centrifuge. The supernatant was filtered off, and the solid precipitate was dried at 110 °C for 6 h. Subsequently, it was calcined at 350 °C for 5 h in a 1% O2 / N2 mixed gas at a heating rate of 2 °C / min to obtain a chromium-based composite catalyst.

[0079] The catalyst prepared in this example was applied to the gas-phase deHF removal and synthesis of HFO-1234ze from HFC-245fa. The reaction was carried out in a fixed-bed reactor under atmospheric pressure, with a catalyst loading of 4 mL and a space velocity of 600 h⁻¹. -1 The reaction temperature was 300℃, and a long-term lifespan evaluation was conducted. Detailed results can be found in [link to results]. Figure 1 .

[0080] Table 1. Activity test results of HFO-1234ze synthesized from HFC-245fa gas-phase deHF under the same conditions using the catalyst of Example 1.

[0081] catalyst HFC-245fa conversion rate / % HFO-1234ze selectivity / % Cr-Zn-PVDF 90.5 98.1 Cr-Al-PVDF 82 98.5 Cr-Co-PVDF 78.2 97.9 Cr-La-PVDF 96.8 96.4 Cr-Mg-PVDF 70.4 95.4 Cr-Y-PVDF 92.7 97.2 Cr-Ni-PVDF 76.7 97.9 Cr-Mn-PVDF 65.8 97.7

[0082] Table 2 shows the activity test results of the catalysts in Examples 2-13 for the gas-phase deHF removal synthesis of HFO-1234ze under the same conditions for HFC-245fa.

[0083] catalyst HFC-245fa conversion rate / % HFO-1234ze selectivity / % Example 2 85.3 91.1 Example 3 96.5 92.8 Example 4 96.4 96.9 Example 5 87.7 97.4 Example 6 93.8 98.7 Example 7 90.6 96.1 Example 8 89.6 95.2 Example 9 85.8 97.7 Example 10 92.6 96.3 Example 11 93.8 99.2 Example 12 96.9 97.8 Example 13 90.7 96.3

[0084] From the above Figure 1 As shown in Tables 1 and 2, the activity results of each catalyst in the examples demonstrate that the chromium-based composite catalyst provided by this invention exhibits high conversion rate, target product selectivity, and catalytic stability at a reaction temperature of 330°C when used in the catalytic cracking reaction of HFC-245fa. Furthermore, this method offers a simple catalyst preparation route, low raw material cost, and minimal waste generation, indicating promising development prospects.

[0085] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis, characterized in that, Includes the following steps: S1: Dissolve the chromium salt, the soluble salt corresponding to the metal component of the auxiliary agent, and the fluorinated polymer in deionized water, stir to dissolve, add the precipitant and continue stirring for a set time to obtain a precipitated mixture. The mass ratio of the chromium salt, the soluble salt corresponding to the auxiliary metal component, and the fluoropolymer is 1:0.05-0.2:0.05-0.2, and the auxiliary metal component includes Ni, La, Mn, and Y; S2: The precipitate mixture obtained in step S1 is placed in a centrifuge container, centrifuged, washed, and dried, and then calcined at high temperature to obtain the composite metal oxide.

2. The method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis according to claim 1, characterized in that, The fluoropolymer is any one or a combination of at least two of PVDF, PTFE, PVF, PTrFE and FEP.

3. The method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis according to claim 1, characterized in that, The mass ratio of the chromium salt, the soluble salt corresponding to the metal auxiliary component, and the fluoropolymer is 1:0.1:0.

1.

4. The method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis according to claim 1, characterized in that, In step S1, stir the mixture using a constant pressure heat collector at a water bath temperature of 25-35℃, at a stirring speed of 300-500 r / min for 10-40 min, then add the precipitant and continue stirring for 0.5-5 h.

5. The method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis according to claim 1, characterized in that, In step S2, the roasting atmosphere is a mixture of O2 and N2, wherein the O2 content is 1-10%.

6. The method for preparing a chromium-based composite catalyst mediated by fluoropolymer synthesis according to claim 5, characterized in that, In step S2, the calcination temperature is 300-500℃, the calcination time is 5-10h, and the calcination heating rate is 1-10℃ / min.

7. A method for preparing 1,3,3,3-tetrafluoropropylene by dehydrofluorination of 1,1,1,3,3-pentafluoropropane, wherein a catalyst is used in the preparation process, characterized in that, The catalyst is a chromium-based composite catalyst prepared by the method described in any one of claims 1 to 6.

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