Preparation of HFO-1234yf by dehydrofluorination of HFC-245eb

Abstract

The invention discloses a method for preparing HFO-1234yf by dehydrofluorination of HFC-245eb, which comprises the following steps: under the action of a catalyst, dehydrofluorination of HFC-245eb is carried out to obtain HFO-1234yf; the catalyst comprises an aluminum fluoride coated SBA-15 carrier and multi-metal active components A and B loaded on the carrier, A is Cr, and B is one or more than two of Mg, Fe, Ni, Co and Zn. According to the invention, high dispersity of active sites and rapid mass transfer of reactants / products are ensured by utilizing high specific surface area and uniform pore channels of SBA-15. The multi-metal nanoparticles provided by the invention have higher thermal stability. The strong interaction among various metals can improve the Tanchmann temperature of the nano particles, so that the nano particles can better maintain fine sizes at the reaction temperature, and more active sites are exposed.

Description

Technical Field

[0001] This invention relates to the field of 2,3,3,3-tetrafluoropropylene (HFO-1234yf) preparation technology, specifically to a method for preparing HFO-1234yf by dehydrofluorination of 1,1,1,2,3-pentafluoropropane (HFC-245eb). Background Technology

[0002] 2,3,3,3-Tetrafluoropropylene, as a novel hydrofluoroolefin (HFO), has an extremely low global warming potential (GWP<1) and a short atmospheric lifetime (about 11 days), making it an ideal alternative to high GWP refrigerants (such as R134a). It is widely used in automotive air conditioning, heat pumps and other fields.

[0003] Currently, the industrial preparation of HFO-1234yf is mainly achieved through the dehydrofluorination reaction of HFC-245eb, with the reaction formula: CF3CHFCH2F→CF3CF=CH2+HF. The core of this reaction is the development of a highly efficient catalyst, which must simultaneously meet the requirements of high activity (HFC-245eb conversion), high selectivity (HFO-1234yf formation), and long-term stability (resistance to fluorine corrosion and carbon deposition).

[0004] In existing technologies, catalysts are mainly divided into two categories: Metal oxide catalysts: Although they have certain activity, their strong acidity leads to excessive defluorination or isomerization. The selectivity of HFO-1234yf is usually less than 90%, and they are easily corroded in HF atmosphere and have poor stability.

[0005] Supported metal catalysts: Metal active centers can activate CF bonds, but single metals are prone to aggregation, and the synergistic effect between the support and the metal is weak, resulting in insufficient activity. In addition, precious metal catalysts are expensive and difficult to industrialize.

[0006] Therefore, developing a non-precious metal catalyst with high activity, high selectivity and high stability is of great significance for the efficient preparation of HFO-1234yf.

[0007] The following existing technologies were found through a search: Patent specification CN103073386A discloses a method for preparing 2,3,3,3-tetrafluoropropene, in which 1,1,1,2,3-pentafluoropropane is reacted with a catalyst at a reaction temperature of 300-350℃ and a space velocity of 300-500 h⁻¹. -1Under specific conditions, hydrogen fluoride is defluorinated, and impurities are separated to obtain 2,3,3,3-tetrafluoropropylene. The catalyst used can be a common defluorination catalyst, such as metal fluorides known in the art: aluminum fluoride, fluorinated chromium oxide, metal supported on chromium fluoride, and metal supported on fluorinated alumina; activated carbon and three-dimensional carbon-containing matrix materials can also be used as supports. Furthermore, defluorination catalysts include, but are not limited to, magnesium fluorides, fluorides of magnesium and zinc mixtures, or fluorides of magnesium and aluminum mixtures, as well as fluorinated oxides and fluorine oxides. Zn-Ni / CrF3 is preferred. The catalyst can be prepared using methods known in the art for preparing fluorination catalysts, such as dissolving zinc and nickel salts in water, impregnating chromium fluoride in the above salt solution, and then drying and calcining to obtain the catalyst.

[0008] Patent specifications with publication numbers CN118698439A and CN118108570A both disclose a method for synthesizing 2,3,3,3-tetrafluoropropylene. 1,1,1,2,3-pentafluoropropane reacts under the action of a catalyst to obtain 2,3,3,3-tetrafluoropropylene. The catalyst used can be a chromium-based catalyst known in the art, with γ-Al₂O₃ and / or AlF₃ as the support, and one or more auxiliary metals selected from Mg, Zn, Co, Fe, In, and Ga are added to increase the dispersion of chromium. The catalyst can be prepared using conventional methods in the art: for example, mixing chromium and auxiliary metal nitrates in a certain ratio to prepare a dilute solution of a certain concentration, adding a precipitant for reaction, then filtering, washing, drying, calcining, granulating, and pressing into a precursor, followed by fluorination to obtain the catalyst. The catalyst pretreatment can be carried out in other reactors. Summary of the Invention

[0009] This invention provides a method for preparing HFO-1234yf by defluorinating HFC-245eb.

[0010] The specific technical solution is as follows: A method for preparing HFO-1234yf by defluorinating HFC-245eb includes: defluorinating HFC-245eb with hydrogen to obtain HFO-1234yf under the action of a catalyst; The catalyst comprises an aluminum fluoride-coated SBA-15 support and multi-metallic active components A and B supported on the support, wherein A is Cr and B is one or more of Mg, Fe, Ni, Co, and Zn. As a preferred example, B is Co, or Zn, or nickel and magnesium. When B is nickel and magnesium, the mass ratio of nickel to magnesium is preferably 1:1.

[0011] Furthermore, in the catalyst of the present invention, the multi-metal active components A and B exist in the form of composite oxides of A oxide and B oxide, for example, Cr oxide is Cr2O3, Co oxide is CoO, Zn oxide is ZnO, Ni oxide is NiO, and Mg oxide is MgO.

[0012] In some preferred embodiments, the loaded mass of A in the catalyst is greater than the loaded mass of B.

[0013] Based on the total mass of the catalyst, the loading mass of A is preferably 4%-16%, for example 10%.

[0014] Based on the total mass of the catalyst, the loading mass of B is preferably 1%-4%, such as 2%, 3%, etc.

[0015] Based on the total mass of the catalyst, the mass percentage of the aluminum fluoride-coated SBA-15 support is preferably 80%-95%.

[0016] In some preferred embodiments, the method for preparing the aluminum fluoride-coated SBA-15 carrier includes: first loading Al2O3 onto SBA-15 using a hydrothermal method, and then fluorinating Al2O3 into aluminum fluoride using NH4F.

[0017] In the preparation method of aluminum fluoride coated SBA-15 carrier, the preferred mass ratio of Al2O3 to SBA-15 is (1:9)-(3:7), for example, 2:8.

[0018] In some preferred embodiments, the hydrothermal method includes: uniformly dispersing SBA-15 mesoporous molecular sieve in an aluminum nitrate solution, heating and crystallizing the resulting mixture in a sealed container under autogenous pressure, and washing, drying, and calcining the crystallized product to complete the loading of Al2O3 on SBA-15.

[0019] Furthermore, the specific surface area of ​​the SBA-15 mesoporous molecular sieve is 500-1000 m². 2 / g.

[0020] Furthermore, the SBA-15 mesoporous molecular sieve has a pore structure of 5-10 nm.

[0021] In the hydrothermal method, the preferred temperature for heating and crystallization is 120-180℃, such as 150℃.

[0022] In the hydrothermal method, the heating and crystallization time is preferably 12-48 h, such as 24 h.

[0023] In the hydrothermal method, the heating rate of the calcination is preferably 1-10℃ / min, for example 2℃ / min.

[0024] In the hydrothermal method, the calcination temperature is preferably 500-700℃, such as 600℃.

[0025] In the hydrothermal method, the calcination time is preferably 2-10 h, for example 4 h.

[0026] In some preferred embodiments, the fluorination of Al2O3 into aluminum fluoride using NH4F specifically includes: adding SBA-15 loaded with Al2O3 into an NH4F solution, stirring thoroughly, allowing it to stand, and drying it to obtain the aluminum fluoride-coated SBA-15 carrier.

[0027] The concentration of NH4F in the NH4F solution is preferably 0.5-2.0 M, for example, 1 mol / L.

[0028] The preferred ratio of NH4F to Al2O3, based on the F:Al molar ratio, is 3:1.

[0029] In some preferred embodiments, the preparation method of the catalyst includes: impregnating the precursors of the multi-metal active components A and B into the pores of an aluminum fluoride-coated SBA-15 support, and drying and calcining to obtain the catalyst.

[0030] The precursors of the multimetallic active components A and B preferably include at least one of nitrates and chlorides.

[0031] In the method for preparing the catalyst, the impregnation is preferably an equal-volume impregnation.

[0032] In some preferred embodiments, the calcination process of the catalyst includes two holding stages, wherein the first holding stage is at 200°C for 1 h and the second holding stage is at 350-500°C (e.g., 400°C) for 4 h.

[0033] In the method for preparing the catalyst, the calcination heating rate is 1-10℃ / min, for example, 2℃ / min.

[0034] Furthermore, in the method for preparing the catalyst, the calcination atmosphere is an air atmosphere.

[0035] In some preferred embodiments, in the method for preparing HFO-1234yf from HFC-245eb defluorination, the catalyst is first subjected to HF activation treatment before being used to catalyze the defluorination of HFC-245eb, so that the oxides on the catalyst surface are converted into fluorine oxides. Further, the HF activation treatment temperature is preferably 350°C.

[0036] In some preferred embodiments, the catalyst is activated using an HF / N2 mixture.

[0037] In the method for preparing HFO-1234yf by defluorinating HFC-245eb, the preferred temperature for defluorinating HFC-245eb under the action of a catalyst is 180-320℃, for example, 250℃.

[0038] In the method for preparing HFO-1234yf from HFC-245eb defluorination, the pressure of HFC-245eb defluorination is preferably 0.1-1.5 MPa, for example, 0.8 MPa, under the action of a catalyst.

[0039] In the method for preparing HFO-1234yf from HFC-245eb defluorination, the preferred mass hourly space velocity (MSV) of the HFC-245eb defluorination hydrogen is 50-1000 h⁻¹ under the action of a catalyst. -1 For example, 100 h -1 500 h -1 wait.

[0040] Furthermore, in the method for preparing HFO-1234yf from HFC-245eb defluorination, under the action of a catalyst, the conversion rate of HFC-245eb defluorination is above 94%, and can further reach above 97%, the selectivity of HFO-1234yf is above 80%, and can further reach above 90%, and the catalyst stability is above 500 h.

[0041] Compared with the prior art, the beneficial effects of this invention are as follows: SBA-15 itself has a high specific surface area (500-1000 m²). 2 The uniform pore size (approximately 5-10 nm) and uniform pore size ensure high dispersion of active sites and rapid mass transfer of reactants / products. Reactants and products can diffuse freely within the pores, avoiding pore blockage. Regular pores limit metal particle aggregation while providing diffusion pathways for reactants.

[0042] Al2O3 was doped into the pore walls of SBA-15, Al 3+ The formed Lewis acidic sites can help activate CF bonds, and their acidity is weaker than that of pure Al2O3, thus avoiding excessive defluorination.

[0043] The Al-F protective layer and pre-passivation effect formed by fluorine modification make the support immune to HF, thus maintaining structural integrity and significantly extending its lifespan during long-term reactions.

[0044] The multi-metal nanoparticles of this invention exhibit higher thermal stability. The strong interactions between the various metals can increase the Taman temperature (the temperature at which significant sintering begins) of the nanoparticles, enabling them to maintain a smaller size at reaction temperatures and expose more active sites.

[0045] The catalyst of this invention is used in the reaction of HFC-245eb defluorination to prepare HFO-1234yf. The conversion rate of HFC-245eb is 94% or even 97% or more, the selectivity of HFO-1234yf is 80% or even 90% or more, and the stability can reach more than 500h. Detailed Implementation

[0046] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0047] The SBA-15 mesoporous molecular sieve used in the following examples has a molecular sieve size of 500-1000 μm. 2 / g specific surface area and 5-10 nm pore structure.

[0048] Example 1: Step 1: Introduction of aluminum species: Aluminum nitrate nonahydrate was dissolved in deionized water by stirring until clear. SBA-15 mesoporous molecular sieve was added to the aluminum nitrate solution. The mixture was stirred continuously at room temperature for 2 hours. The mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and crystallized at 120°C for 24 hours. The crystallized product was washed, dried, and then calcined at 500°C for 4 hours at a heating rate of 2°C / min to complete the loading of Al2O3 onto SBA-15, obtaining an Al2O3-SBA-15 composite support (the amount of aluminum nitrate nonahydrate used was calculated based on a mass ratio of Al2O3 to SBA-15 of 1:9).

[0049] Step 2: Fluorine modification: Weigh out NH4F and dissolve it in deionized water at an F / Al molar ratio of 3:1, stirring until completely dissolved (forming a 0.5 mol / L NH4F solution). Take the Al2O3-SBA-15 composite support and slowly add it to the above NH4F solution. Stir for 30 min and let stand for 12 h. Dry under vacuum at 60℃ for 8 h, then raise the temperature to 120℃ and dry for another 8 h. After cooling, obtain the aluminum fluoride-coated SBA-15 support.

[0050] Step 3: Metal Loading Chromium nitrate and cobalt nitrate (based on the total mass of the catalyst, with 4% chromium and 1% cobalt loaded) were dissolved in deionized water and stirred until completely dissolved. The solution was then brought to a volume corresponding to the water absorption rate of the support. The aluminum fluoride-coated SBA-15 support was placed in a beaker, and the above metal salt solution was slowly added dropwise while stirring until the solution was completely absorbed by the support. The impregnated sample was allowed to stand at room temperature for 12 hours to allow the metal ions to fully diffuse into the pores of the support. The sample was transferred to an evaporating dish and dried in an oven at 80°C for 4 hours, then heated to 120°C and dried for another 8 hours. The dried solid was transferred to a porcelain boat and placed in a muffle furnace. The temperature was increased to 200°C at a rate of 2°C / min and held for 1 hour; then increased to 350°C at a rate of 2°C / min and held in air for 4 hours. The solution was then allowed to cool naturally to room temperature to obtain the Cr2O3-CoO / aluminum fluoride-coated SBA-15 catalyst.

[0051] Step 4: HF activation: Place the catalyst from step 3 into a quartz tube reactor. Purge with inert gas to remove air. Proceed to the target activation temperature of 350°C using a programmed temperature rise method. Switch to an HF / N2 mixture (HF volume content 2%) and maintain at this temperature for 4 hours. After activation, purge the system with pure inert gas to remove residual HF.

[0052] Step 5: Activity test: After HF activation, high-purity HFC-245eb feed gas is introduced. At a reaction temperature of 0.1 MPa and 180 °C, the feed mass hourly space velocity (MHSV) is adjusted to 100 h⁻¹. -1 The reaction was carried out continuously. The gas stream at the reaction outlet was condensed and washed with 5wt% KOH solution to remove HF. The dried gaseous products were quantitatively analyzed by gas chromatography. After 24 h of continuous reaction, the conversion rate of HFC-245eb was 94.6%, the selectivity of HFO-1234yf was 81.8%, and the selectivity of HFC-245cb was 17.9%. After 500 h of continuous reaction, there were no significant changes in the conversion rate of HFC-245eb, the selectivity of HFO-1234yf, and the selectivity of HFC-245cb.

[0053] Example 2: Step 1: Introduction of aluminum species: Aluminum nitrate nonahydrate was dissolved in deionized water by stirring until clear. SBA-15 mesoporous molecular sieve was added to the aluminum nitrate solution. The mixture was stirred continuously at room temperature for 2 hours. The solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and crystallized at 150°C for 24 hours. The crystallized product was washed, dried, and then calcined at 600°C for 4 hours at a heating rate of 2°C / min to complete the loading of Al2O3 onto SBA-15, yielding an Al2O3-SBA-15 composite support (the amount of aluminum nitrate nonahydrate used was calculated based on a mass ratio of Al2O3 to SBA-15 of 2:8).

[0054] Step 2: Fluorine modification: Weigh out NH4F and dissolve it in deionized water at an F / Al molar ratio of 3:1, stirring until completely dissolved (forming a 1 mol / L NH4F solution). Take the Al2O3-SBA-15 composite support and slowly add it to the above NH4F solution. Stir for 30 min and let stand for 12 h. Dry under vacuum at 60℃ for 8 h, then raise the temperature to 120℃ and dry for another 8 h. After cooling, obtain the aluminum fluoride-coated SBA-15 support.

[0055] Step 3: Metal Loading Chromium nitrate and zinc nitrate (based on the total mass of the catalyst, with 10% chromium and 3% zinc loading) were dissolved in deionized water and stirred until completely dissolved. The solution was then brought to a volume corresponding to the water absorption rate of the support. The aluminum fluoride-coated SBA-15 support was placed in a beaker, and the above metal salt solution was slowly added dropwise while stirring until the solution was completely absorbed by the support. The impregnated sample was allowed to stand at room temperature for 12 hours to allow the metal ions to fully diffuse into the pores of the support. The sample was transferred to an evaporating dish and dried in an oven at 80°C for 4 hours, then heated to 120°C and dried for another 8 hours. The dried solid was transferred to a porcelain boat and placed in a muffle furnace. The temperature was increased to 200°C at a rate of 2°C / min and held for 1 hour; then increased to 400°C at a rate of 2°C / min and held in air for 4 hours. The solution was then allowed to cool naturally to room temperature to obtain the Cr2O3-ZnO / aluminum fluoride-coated SBA-15 catalyst.

[0056] Step 4: HF activation: Place the catalyst from step 3 into a quartz tube reactor. Purge with inert gas to remove air. Proceed to the target activation temperature of 350°C using a programmed temperature rise method. Switch to an HF / N2 mixture (HF volume content 2%) and maintain at this temperature for 4 hours. After activation, purge the system with pure inert gas to remove residual HF.

[0057] Step 5: Activity test: After HF activation, high-purity HFC-245eb feed gas is introduced. At a reaction temperature of 0.8 MPa and 250 °C, the feed mass hourly space velocity (MHSV) is adjusted to 500 h⁻¹. -1The reaction was carried out continuously. The gas stream at the reaction outlet was condensed and washed with 5wt% KOH solution to remove HF. The dried gaseous products were quantitatively analyzed by gas chromatography. After 24 h of continuous reaction, the conversion rate of HFC-245eb was 96.2%, the selectivity of HFO-1234yf was 85.4%, and the selectivity of HFC-245cb was 13.4%. After 500 h of continuous reaction, there were no significant changes in the conversion rate of HFC-245eb, the selectivity of HFO-1234yf, and the selectivity of HFC-245cb.

[0058] Example 3: Step 1: Introduction of aluminum species: Aluminum nitrate nonahydrate was dissolved in deionized water by stirring until clear. SBA-15 mesoporous molecular sieve was added to the aluminum nitrate solution. The mixture was stirred continuously at room temperature for 2 hours. The solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and crystallized at 180°C for 24 hours. The crystallized product was washed, dried, and then calcined at 700°C for 4 hours at a heating rate of 2°C / min to complete the loading of Al2O3 onto SBA-15, yielding an Al2O3-SBA-15 composite support (the amount of aluminum nitrate nonahydrate used was calculated based on a mass ratio of Al2O3 to SBA-15 of 3:7).

[0059] Step 2: Fluorine modification: Weigh out NH4F and dissolve it in deionized water at an F / Al molar ratio of 3:1, stirring until completely dissolved (forming a 2 mol / L NH4F solution). Take the Al2O3-SBA-15 composite support and slowly add it to the above NH4F solution. Stir for 30 min and let stand for 12 h. Dry under vacuum at 60℃ for 8 h, then raise the temperature to 120℃ and dry for another 8 h. After cooling, obtain the aluminum fluoride-coated SBA-15 support.

[0060] Step 3: Metal Loading Chromium nitrate, nickel nitrate, and magnesium nitrate (based on the total mass of the catalyst, with chromium loading at 16%, nickel loading at 2%, and magnesium loading at 2%) were dissolved in deionized water and stirred until completely dissolved. The solution was then brought to a volume corresponding to the water absorption rate of the support. The aluminum fluoride-coated SBA-15 support was placed in a beaker, and the above metal salt solution was slowly added dropwise while stirring until the solution was completely absorbed by the support. The impregnated sample was allowed to stand at room temperature for 12 hours to allow the metal ions to fully diffuse into the pores of the support. The sample was transferred to an evaporating dish and dried in an oven at 80°C for 4 hours, then heated to 120°C and dried for another 8 hours. The dried solid was transferred to a porcelain boat and placed in a muffle furnace. The temperature was increased to 200°C at a rate of 2°C / min and held for 1 hour; then increased to 500°C at a rate of 2°C / min and held in air for 4 hours. The solution was naturally cooled to room temperature to obtain the Cr2O3-NiO-MgO / aluminum fluoride-coated SBA-15 catalyst.

[0061] Step 4: HF activation: Place the catalyst from step 3 into a quartz tube reactor. Purge with inert gas to remove air. Proceed to the target activation temperature of 350°C using a programmed temperature rise method. Switch to an HF / N2 mixture (HF volume content 2%) and maintain at this temperature for 4 hours. After activation, purge the system with pure inert gas to remove residual HF.

[0062] Step 5: Activity test: After HF activation, high-purity HFC-245eb feed gas is introduced. At a reaction temperature of 1.5 MPa and 320 °C, the feed mass hourly space velocity (MHSV) is adjusted to 1000 h⁻¹. -1 The reaction was carried out continuously. The gas stream at the reaction outlet was condensed and washed with 5wt% KOH solution to remove HF. The dried gaseous products were quantitatively analyzed by gas chromatography. After 24 h of continuous reaction, the conversion rate of HFC-245eb was 97.8%, the selectivity of HFO-1234yf was 90.2%, and the selectivity of HFC-245cb was 8.3%. After 500 h of continuous reaction, there were no significant changes in the conversion rate of HFC-245eb, the selectivity of HFO-1234yf, and the selectivity of HFC-245cb.

[0063] Comparative Example 1: Step 1: Fluorine modification: Weigh out NH4F and dissolve it in deionized water at an F / Al molar ratio of 3:1, stirring until completely dissolved (forming a 1 mol / L NH4F solution). Take commercially available Al2O3 support and slowly add it to the above NH4F solution, stirring for 30 min and then allowing it to stand for 12 h. Dry under vacuum at 60℃ for 8 h, then raise the temperature to 120℃ and dry for another 8 h. After cooling, obtain the aluminum fluoride support.

[0064] Step 2: Metal load: Chromium nitrate and zinc nitrate (based on the total mass of the catalyst, with 10% chromium and 3% zinc loaded) were dissolved in deionized water and stirred until completely dissolved. The solution was then brought to a volume corresponding to the water absorption rate of the support. The aluminum fluoride support was placed in a beaker, and the above metal salt solution was slowly added dropwise while stirring until the solution was completely absorbed by the support. The impregnated sample was allowed to stand at room temperature for 12 hours. The sample was then transferred to an evaporating dish and dried in an oven at 80°C for 4 hours, followed by drying at 120°C for 8 hours. The dried solid was transferred to a porcelain boat and placed in a muffle furnace. The temperature was increased to 200°C at a rate of 2°C / min and held for 1 hour; then increased to 400°C at a rate of 2°C / min and held in air for 4 hours. The solution was then allowed to cool naturally to room temperature to obtain the Cr2O3-ZnO / aluminum fluoride catalyst.

[0065] Step 3: HF activation: Place the catalyst from step 2 in a quartz tube reactor. Purge with inert gas to remove air. Proceed to the target activation temperature of 350°C using a programmed temperature rise method. Switch to an HF / N2 mixture (HF volume content 2%) and maintain at this temperature for 4 hours. After activation, purge the system with pure inert gas to remove residual HF.

[0066] Step 4: Activity test: After HF activation, high-purity HFC-245eb feed gas is introduced. At a reaction temperature of 0.8 MPa and 250 °C, the feed mass hourly space velocity (MHSV) is adjusted to 500 h⁻¹. -1 The reaction was carried out continuously. The gas stream at the reaction outlet was condensed and washed with 5wt% KOH solution to remove HF. The dried gaseous products were quantitatively analyzed by gas chromatography. After 24 h of continuous reaction, the conversion rate of HFC-245eb was 35.1%, the selectivity of HFO-1234yf was 92.3%, and the selectivity of HFC-245cb was 7.1%. After 500 h of continuous reaction, the conversion rate of HFC-245eb and the selectivity of HFO-1234yf both decreased significantly.

[0067] Comparative Example 2: Step 1: Introduction of aluminum species: Aluminum nitrate nonahydrate was dissolved in deionized water by stirring until clear. SBA-15 mesoporous molecular sieve was added to the aluminum nitrate solution. The mixture was stirred continuously at room temperature for 2 hours. The solution was then transferred to a polytetrafluoroethylene-lined hydrothermal reactor and crystallized at 150°C for 24 hours. The crystallized product was washed, dried, and then calcined at 600°C for 4 hours at a heating rate of 2°C / min to complete the loading of Al2O3 onto SBA-15, yielding an Al2O3-SBA-15 composite support (the amount of aluminum nitrate nonahydrate used was calculated based on a mass ratio of Al2O3 to SBA-15 of 2:8).

[0068] Step 2: Fluorine modification: Weigh out NH4F and dissolve it in deionized water at an F / Al molar ratio of 3:1, stirring until completely dissolved (forming a 1 mol / L NH4F solution). Take the Al2O3-SBA-15 composite support and slowly add it to the above NH4F solution. Stir for 30 min and let stand for 12 h. Dry under vacuum at 60℃ for 8 h, then raise the temperature to 120℃ and dry for another 8 h. After cooling, obtain the aluminum fluoride-coated SBA-15 support.

[0069] Step 3: Metal Loading Chromium nitrate (with a chromium loading of 15% based on the total mass of the catalyst) was dissolved in deionized water and stirred until completely dissolved. The solution was then brought to a volume corresponding to the water absorption rate of the support. The aluminum fluoride-coated SBA-15 support was placed in a beaker, and the above metal salt solution was slowly added dropwise while stirring until the solution was completely absorbed by the support. The impregnated sample was allowed to stand at room temperature for 12 hours to allow the metal ions to fully diffuse into the pores of the support. The sample was transferred to an evaporating dish and dried in an oven at 80°C for 4 hours, then heated to 120°C and dried for another 8 hours. The dried solid was transferred to a porcelain boat and placed in a muffle furnace. The temperature was increased to 200°C at a rate of 2°C / min and held for 1 hour; then increased to 400°C at a rate of 2°C / min and held in air for 4 hours. The solution was then allowed to cool naturally to room temperature to obtain the Cr2O3 / aluminum fluoride-coated SBA-15 catalyst.

[0070] Step 4: HF activation: Place the catalyst from step 3 into a quartz tube reactor. Purge with inert gas to remove air. Proceed to the target activation temperature of 350°C using a programmed temperature rise method. Switch to an HF / N2 mixture (HF volume content 2%) and maintain at this temperature for 4 hours. After activation, purge the system with pure inert gas to remove residual HF.

[0071] Step 5: Activity test: After HF activation, high-purity HFC-245eb feed gas is introduced. At a reaction temperature of 0.8 MPa and 250 °C, the feed mass hourly space velocity (MHSV) is adjusted to 500 h⁻¹. -1 The reaction was carried out continuously. The gas stream at the reaction outlet was condensed and washed with 5wt% KOH solution to remove HF. The dried gaseous products were quantitatively analyzed by gas chromatography. After 24 h of continuous reaction, the conversion rate of HFC-245eb was 61.1%, the selectivity of HFO-1234yf was 82.9%, and the selectivity of HFC-245cb was 16.3%. After 500 h of continuous reaction, the conversion rate of HFC-245eb and the selectivity of HFO-1234yf both decreased significantly.

[0072] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing HFO-1234yf by defluorination of HFC-245eb, characterized in that, include: Under the action of a catalyst, HFC-245eb was dehydrofluorinated to obtain HFO-1234yf; The catalyst comprises an aluminum fluoride-coated SBA-15 support and multi-metallic active components A and B supported on the support, wherein A is Cr and B is one or more of Mg, Fe, Ni, Co, and Zn.

2. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, The loaded mass of A in the catalyst is greater than the loaded mass of B.

3. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Based on the total mass of the catalyst, the loading mass of A is 4%-16%.

4. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Based on the total mass of the catalyst, the loading mass of B is 1%-4%.

5. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Based on the total mass of the catalyst, the mass percentage of the aluminum fluoride-coated SBA-15 support is 80%-95%.

6. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, The preparation method of the aluminum fluoride-coated SBA-15 carrier includes: first loading Al2O3 onto SBA-15 using a hydrothermal method, and then fluorinating Al2O3 into aluminum fluoride using NH4F.

7. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 6, characterized in that, In the preparation method of aluminum fluoride coated SBA-15 carrier, the mass ratio of Al2O3 to SBA-15 is (1:9)-(3:7).

8. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 6, characterized in that, The hydrothermal method includes: uniformly dispersing SBA-15 mesoporous molecular sieve in aluminum nitrate solution, heating and crystallizing the resulting mixture in a closed container under autogenous pressure, washing, drying and calcining the crystallized product to complete the loading of Al2O3 on SBA-15.

9. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The specific surface area of ​​the SBA-15 mesoporous molecular sieve is 500-1000 m². 2 / g; The SBA-15 mesoporous molecular sieve has a pore structure of 5-10 nm.

10. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The temperature for the heating and crystallization is 120-180℃.

11. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The heating and crystallization time is 12-48 h.

12. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The heating rate for roasting is 1-10℃ / min.

13. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The roasting temperature is 500-700℃.

14. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 8, characterized in that, The roasting time is 2-10 h.

15. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 6, characterized in that, The process of fluorinating Al2O3 into aluminum fluoride using NH4F specifically includes: adding SBA-15 loaded with Al2O3 into an NH4F solution, stirring thoroughly, allowing it to stand, and drying it to obtain the aluminum fluoride-coated SBA-15 carrier.

16. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 15, characterized in that, The concentration of NH4F in the NH4F solution is 0.5-2.0 M.

17. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 6, characterized in that, The ratio of NH4F to Al2O3 is 3:1 based on the F:Al molar ratio.

18. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, The catalyst is prepared by impregnating the precursors of the multi-metal active components A and B into the pores of an aluminum fluoride-coated SBA-15 support, followed by drying and calcination to obtain the catalyst.

19. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 18, characterized in that, The precursors of the multimetallic active components A and B include at least one of nitrates and chlorides.

20. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 18, characterized in that, The impregnation is an equal-volume impregnation.

21. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 18, characterized in that, The calcination includes two heat preservation stages, in which the first heat preservation stage is at 200℃ for 1 hour and the second heat preservation stage is at 350-500℃ for 4 hours.

22. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 18, characterized in that, The heating rate for calcination is 1-10℃ / min.

23. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, The catalyst is first activated with HF before being used to catalyze the defluorination of HFC-245eb, so that the oxides on the catalyst surface are converted into fluorine oxides.

24. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 23, characterized in that, The HF activation treatment is performed at a temperature of 350°C.

25. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Under the action of a catalyst, the temperature for defluorination of HFC-245eb is 180-320℃.

26. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Under the action of a catalyst, the pressure of defluorinated hydrogen in HFC-245eb is 0.1-1.5 MPa.

27. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Under the action of a catalyst, the mass hourly space velocity (MSV) of HFC-245eb defluorinated hydrogen is 50-1000 h⁻¹. -1 .

28. The method for preparing HFO-1234yf by defluorination of HFC-245eb according to claim 1, characterized in that, Under the action of the catalyst, the conversion rate of defluorinated hydrogen by HFC-245eb is above 94%, the selectivity of HFO-1234yf is above 80%, and the catalyst stability is above 500 h.