A polyphosphoric acid surface-modified metal-based catalyst, and a preparation method and application thereof

Abstract

The application discloses a polyphosphoric acid surface modified metal-based catalyst and a preparation method and application thereof. The catalyst comprises a metal compound and polyphosphoric acid surface modification thereof. The type of metal in the catalyst comprises at least one of Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb and Ti. The metal compound is one of fluoride, oxide, sulfate and nitrate of any one of the above metals or a combination of any two to three thereof. The source of polyphosphoric acid in the catalyst comprises at least one of inorganic phosphate, hypophosphite, phosphite or phosphoric acid ester compound. The polyphosphoric acid surface modified metal-based catalyst prepared by the application has higher selectivity and stability in the reaction of preparing fluorine-containing olefins (HFOs) through gas phase dehydrofluorination of fluorine-containing alkanes and gas phase dehydrochlorination of fluorine-containing chloroalkanes (HCFCs), improves the service life of the catalyst, and is not easy to form carbon deposition in the reaction, has high yield of target products, high conversion rate of raw materials and is easy to be industrialized.

Description

Technical Field

[0001] The present application belongs to the technical field of heterogeneous thermal catalysts, and specifically relates to a metal-based catalyst surface-modified with polyphosphoric acid, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are non-CO2 greenhouse gases with long atmospheric lifetimes and a strong greenhouse effect. To reduce their environmental impact, resource conversion can be used to produce environmentally friendly fluorinated olefins (HFOs). These fluorinated olefins have a wide range of applications in refrigerants, foams, and aerosols, and offer high economic benefits. Therefore, converting HFCs and HCFCs into economically valuable fluorinated intermediates and fluorinated olefins, among other fluorinated compounds, contributes to the efficient utilization of fluorine resources.

[0003] Currently, the most common method is to use metal compounds as catalysts to crack hydrofluorocarbons and hydrochlorofluorocarbons to remove HF and HCl to produce fluorinated olefins. However, due to the high bond energy of the C—X bond, the reaction requires high reaction temperatures (300-800°C), which can easily lead to carbon deposits and coking, shortening the catalyst's service life. Therefore, developing a catalyst that is resistant to carbon deposits and highly stable is crucial for the success of the reaction.

[0004] Ligand modification of the surface of nanocatalysts is a simple, inexpensive and efficient means of regulation. Through surface ligand modification, the interaction between the ligand and the catalyst produces certain electronic effects and steric effects, which often affect the catalytic activity, catalytic selectivity and catalytic stability of the catalyst. We innovatively used polyphosphoric acid as a surface modification material for metal-based catalysts, and used metal compounds modified with polyphosphoric acid as catalysts for the cracking and removal of HF from hydrofluorocarbons and hydrochlorofluorocarbons, and the preparation of fluorinated olefins from HCl. The research results show that the metal-based catalyst modified with polyphosphoric acid has excellent catalytic activity, stability and outstanding carbon deposition ability in the cracking and removal of HF from hydrofluorocarbons and hydrochlorofluorocarbons, and the preparation of fluorinated olefins from HCl. Therefore, the metal-based catalyst modified with polyphosphoric acid prepared by this method has good application prospects in the field of cracking and removal of HF from hydrofluorocarbons and hydrochlorofluorocarbons, and the preparation of fluorinated olefins from HCl. Summary of the Invention

[0005] To address the problem of carbon deposition leading to catalyst deactivation in existing metal-based catalysts, the present invention provides a polyphosphoric acid surface-modified metal-based catalyst, its preparation method, and its application. The present method for preparing the polyphosphoric acid surface-modified metal-based catalyst is characterized by ease of preparation and controllability. The synthesized catalyst exhibits high catalytic activity and stability in the cracking of hydrofluorocarbons and hydrochlorofluorocarbons to remove HF and in the preparation of fluorinated olefins from HCl. The catalyst is not easily deactivated by carbon deposition, thus demonstrating high practicality.

[0006] The metal-based catalyst for surface-modified polyphosphoric acid comprises a metal compound and surface-modified polyphosphoric acid thereof, wherein the metal in the catalyst comprises at least one of Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, and Ti.

[0007] Furthermore, the metal compound includes fluorides, sulfates, nitrates or oxides of 1-3 metals selected from Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb and Ti.

[0008] For example, metal fluorides include but are not limited to metal fluorides of any one of the metals such as Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, Ti, or a combination of two to three metal fluorides: aluminum fluoride (AlF3), lead fluoride (PbF2), cerium fluoride (CeF3), magnesium fluoride (MgF2), ferrous fluoride (FeF2), zirconium fluoride (ZrF4), nickel fluoride (NiF2), copper fluoride (CuF2), manganese fluoride (MnF2), barium fluoride (BaF2), zinc fluoride (ZnF2), cobalt fluoride (CoF2), strontium fluoride (SrF2), etc.

[0009] For example, metal oxides include but are not limited to oxides of any one of the metals such as Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, Ti, and a combination of two to three metal oxides: aluminum oxide (Al2O3), iron oxide (Fe2O3), magnesium oxide (MgO), zinc oxide (ZnO), copper oxide (CuO), lead oxide (PbO), manganese oxide (MnO2), nickel oxide (NiO), chromium oxide (Cr2O3), titanium oxide (TiO2), barium oxide (BaO), cobalt oxide (CoO), etc.

[0010] For example, metal salts include but are not limited to metal sulfates of any one of the metals such as Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, Ti, or a combination of two to three metal sulfates: copper sulfate (CuSO4), iron sulfate (FeSO4), zinc sulfate (ZnSO4), magnesium sulfate (MgSO4), aluminum sulfate (Al2(SO4)3), manganese sulfate (MnSO4), barium sulfate (BaSO4), lead sulfate (PbSO4), nickel sulfate (NiSO4), cobalt sulfate (CoSO4), and chromium sulfate (Cr2(SO4)3).

[0011] For example, metal salts include but are not limited to metal nitrates of any one of the metals such as Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, Ti, or a combination of two or three metal nitrates: copper nitrate (Cu(NO3)2), iron nitrate (Fe(NO3)3), ferrous nitrate (Fe(NO3)2), zinc nitrate (Zn(NO3)2), magnesium nitrate (Mg(NO3)2), aluminum nitrate (Al2((NO3)3), manganese nitrate (Mn(NO3)2), barium nitrate (Ba(NO3)2), lead nitrate (Pb(NO3)2), nickel nitrate (Ni(NO3)2), cobalt nitrate (Co(NO3)2), and chromium nitrate (Cr(NO3)3).

[0012] Furthermore, the phosphorus source of the polyphosphoric acid in the polyphosphoric acid surface-modified metal-based catalyst includes but is not limited to phosphoric acid (H3PO4), phosphorus dioxide (P2O5), phosphorous acid (H3PO2), dimethyl phosphate (CH3OP(O)(OCH3)), triethyl phosphate (C6H 15 O4P), sodium dihydrogen phosphate (NaH2PO4), trimethyl phosphate (P(OCH3)3), trimethyl phosphate (P(OCH3)3), ammonium phosphate (NH4H2PO4), trimethyl phosphite (P(OCH3)3), diethyl phosphate (C4H 11 O3P), triisopropyl phosphate (C9H 21 O4P), sodium phosphite (Na3PO2), ammonium phosphite ((NH3)3PO2), potassium dihydrogen phosphate (KH2PO4), tripropyl phosphate (C9H 21 O4P), dimethyl trihydrogen phosphate (H3PO4·2CH3OH), diethyl hydrogen phosphate (C6H 15 The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials, stirring the metal compound to react with a phosphorus source solution, separating a solid product, and then calcining the solid product under an air atmosphere; the molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:1, preferably 0.5 to 3:1.

[0013] The method for preparing a polyphosphoric acid surface-modified metal-based catalyst is prepared by a solution calcination method. The specific steps are as follows: dispersing metal compound powder in a phosphorus source solution, wherein the molar ratio of the phosphorus element in the phosphorus source to the metal compound is 0.1 to 5:1, stirring at room temperature for 1 to 10 hours, then centrifuging and drying, and calcining the solid powder in a muffle furnace at 300 to 600°C for 1 to 8 hours to obtain the polyphosphoric acid surface-modified metal-based catalyst. The metal compound includes fluorides, sulfates, or nitrates of one to three metals selected from the group consisting of Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ba, Sr, Pb, and Ti.

[0014] Furthermore, the molar ratio of the P element in the phosphorus source to the metal compound is 0.5 to 3:1, preferably 0.5 to 1.5:1, and the stirring time at room temperature is 1.5 to 6 hours. The mixture is then centrifuged and dried at a temperature of 60 to 140°C for 8 to 16 hours, preferably 60 to 110°C for 10 to 13 hours. The solid powder is calcined in a muffle furnace at 300 to 600°C for 1 to 8 hours, preferably 450 to 550°C, and 2 to 6 hours.

[0015] The metal-based catalyst with the surface modified with polyphosphoric acid is prepared by the method defined in the present invention.

[0016] The invention discloses a preparation method of a polyphosphoric acid surface-modified metal-based catalyst and its application in catalyzing the dehydrofluorination reaction of cracking fluorinated alkanes, wherein the fluorinated alkanes include but are not limited to 1,1-difluoroethane, tetrafluoroethane or 1,1,1,3,3-pentafluoropropane.

[0017] The polyphosphoric acid surface-modified metal-based catalyst is used in the catalytic dehydrofluorination reaction of fluorinated alkanes, including but not limited to 1,1-difluoroethane (HFC-152a), 1,1,1,2-tetrafluoroethane (HFC-134a), and 1,1,1,3,3-pentafluoropropane (HFC-245fa). The fluorinated chloroalkanes include 1,1-difluoro-1-chloroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), and dichlorodifluoroethane (HCFC-132b). The reaction temperature is 300-450°C and the reaction pressure is atmospheric pressure.

[0018] Furthermore, when the fluorine-containing alkane is 1,1-difluoroethane HFC-152a, the corresponding target product is vinyl fluoride VF, and the metal species in the catalyst include Al, Cr, Ba, Mg or Co, preferably Al or Cr.

[0019] Furthermore, when the fluorinated alkane is 1,1,1,3,3-pentafluoropropane HFC-245fa, the corresponding target product is 1,3,3,3-tetrafluoropropene HFO-1234ze, and the metal species in the catalyst include Ni or Al.

[0020] Furthermore, when the fluorinated alkane is HFC-134a, the corresponding target product is CF2=CHF, and the metal species in the catalyst include Mg, Mn or Zn.

[0021] Furthermore, when the fluorine-containing alkane is 1,1-difluoro-1-chloroethane HCFC-142b, the corresponding target product is 1,1-difluoroethylene VDF, and the metal species in the catalyst include Pb, Ba or Al.

[0022] Furthermore, when the fluorinated alkane is HCFC-244bb, the corresponding target product is HFO-1234yf, and the metal species in the catalyst include Sr, Cr, Mg or Fe.

[0023] Furthermore, when the fluorinated alkane is HCFC-132b, the corresponding target product is 1,1-difluoro-2-chloroethylene, and the metal species in the catalyst include Ni, Zr, Cu, Ce, Zn or Mg, preferably Ce, Zn or Mg.

[0024] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The polyphosphoric acid surface-modified metal-based catalyst of the present invention is prepared by a solution roasting method using polyphosphoric acid as a surface modification material. The preparation method is simple. The obtained polyphosphoric acid surface-modified metal-based catalyst has high catalytic activity and stability in the reaction of decomposing hydrofluorocarbons and hydrochlorofluorocarbons to remove HF and preparing fluorinated olefins from HCl, thereby increasing the service life of the catalyst. The catalyst is not prone to carbon deposition during the reaction, has a high yield of the target product, a high conversion rate of the fluorinated alkane, and is easy to industrialize. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Example 1

[0028] 5.1 g of alumina powder was dispersed in 50 mL of sodium dihydrogen phosphate aqueous solution at a molar ratio of sodium dihydrogen phosphate to alumina of 0.5. The mixture was stirred at room temperature for 6 hours, then centrifuged and dried at 80°C for 12 hours. The solid powder was then calcined in a muffle furnace at 550°C for 3 hours to produce a polyphosphoric acid surface-modified alumina catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0029] The polyphosphoric acid surface-modified alumina catalyst prepared above was used to catalyze the cracking of 1,1-difluoroethane (HFC-152a) to produce vinyl fluoride, and the reaction formula is as follows:

[0030]

[0031] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N2 and HFC-152a was introduced at an N2 flow rate of 10 mL / min and an HFC-152a flow rate of 10 mL / min, a total space velocity of 1200 / h for the N2 and HCFC-152a mixture, and a reaction temperature of 350°C. Sampling and analysis after 6 hours of reaction revealed a 77.5% conversion of the reactant 1,1-difluoroethane (HFC-152a) and a 100% selectivity for the product vinyl fluoride. Furthermore, sampling and analysis after 30 hours of catalytic reaction revealed a 75.8% conversion of the reactant HFC-152a and a 100% selectivity for the product vinyl fluoride (i.e., the reactant conversion and the target product selectivity remained essentially unchanged).

[0032] The above catalyst preparation steps were repeated, with the difference being that some conditions were changed, such as "type of metal compound", "type of phosphorus source", "molar ratio of P element in phosphorus source to metal compound", stirring time at room temperature and calcination conditions in a muffle furnace.

[0033] The different catalysts prepared under varying conditions were then used to catalyze the production of vinyl fluoride (VF) from HFC-152a. The catalytic application parameters were repeated in the same manner as in Example 1, with the catalytic application conditions remaining unchanged. The catalytic application results of the different catalysts are shown in Table 1.

[0034] Table 1: Catalytic production of VF by HFC-152a

[0035]

[0036] The feed ratio in Table 1 refers to the molar ratio of phosphorus source to metal source.

[0037] It can be seen from Table 1 that when the metals are Al, Cr, Ba, Mg and Co, good catalytic reaction effects can be achieved, especially when Al and Cr are selected as metals, the effects are better.

[0038] In addition, control experiments were conducted using the conditions described in Table 1 for each experimental group. The only differences were that no phosphorus source was added during the catalyst preparation process and that the final catalyst was not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table a.

[0039] Table a Catalytic Preparation of VF by HFC-152a

[0040]

[0041] Example 2

[0042] 5.45 g of nickel oxide powder was dispersed in 48 mL of sodium dihydrogen phosphate aqueous solution at a molar ratio of 0.8. The mixture was stirred at room temperature for 5 hours, then centrifuged and dried at 80°C for 20 hours. The solid powder was then calcined in a muffle furnace at 550°C for 4 hours to produce a polyphosphoric acid surface-modified nickel oxide catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0043] The nickel oxide catalyst modified with polyphosphoric acid prepared above was used to catalyze the cracking of 1,1,1,3,3-pentafluoropropane (HFC-245fa) to prepare 1,3,3,3-tetrafluoropropylene (HFO-1234ze), and the reaction formula is as follows:

[0044]

[0045] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N₂ and HFC-245fa was introduced at an N₂ flow rate of 10 mL / min, an HFC-245fa flow rate of 10 mL / min, a total space velocity of 1200 / h, and a reaction temperature of 350°C. Sampling and analysis after 5 hours of reaction revealed a 79.5% conversion of the reactant 1,1,1,3,3-pentafluoropropane and an 88.6% selectivity for the product cis-trans 1,3,3,3-tetrafluoropropene (HFO-1234ze). Furthermore, sampling and analysis after 12 hours of catalytic reaction showed a 99.2% conversion of the reactants and a 99.5% selectivity for the target product.

[0046] The above catalyst preparation steps were repeated, with the following variations: the type of metal compound, the type of phosphorus source, the molar ratio of P in the phosphorus source to the metal compound, the stirring time at room temperature, and the calcination conditions in the muffle furnace. When the metal compound is a soluble metal salt, such as ferric nitrate in Table 2, the centrifugal separation step is omitted during the catalyst preparation process. The catalyst is directly stirred at 80°C to evaporate the water, followed by drying at 80°C for 20 hours. The same applies below.

[0047] The different catalysts prepared under varying conditions were then applied to the reaction of HFC-245fa to HFO-1234ze, repeating the process described in Example 2 with the same catalytic application conditions. The catalytic application results of the different catalysts are shown in Table 2.

[0048] Table 2: Catalytic production of HFO-1234ze from HFC-245fa

[0049]

[0050]

[0051] The feed ratio in Table 2 refers to the molar ratio of phosphorus source to metal source.

[0052] As can be seen from Table 2, the choice of metal has a great influence on the catalytic activity. Al and Ni have better catalytic effects, while Fe, Sr and Zn have relatively poor catalytic activity.

[0053] In addition, control experiments were conducted using the conditions described in Table 2 for each experimental group. The only differences were that no phosphorus source was added during the catalyst preparation process and that the final catalyst was not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table b.

[0054] Table b Catalytic preparation of HFO-1234ze from HFC-245fa

[0055]

[0056] Example 3

[0057] 7.25 g of magnesium oxide powder was dispersed in 68 mL of trimethyl phosphate aqueous solution at a molar ratio of trimethyl phosphate to magnesium oxide of 0.9. The mixture was stirred at room temperature for 5 hours, centrifuged, and dried at 80°C for 18 hours. The solid powder was then calcined in a muffle furnace at 500°C for 5 hours to produce a polyphosphoric acid surface-modified magnesium oxide catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0058] The polyphosphoric acid surface-modified magnesium oxide catalyst prepared above is used to catalyze the cracking of CH2FCF3 (HFC-134a) to prepare CF2=CHF.

[0059] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N2 and HFC-134a was introduced at an N2 flow rate of 10 mL / min, an HFC-134a flow rate of 10 mL / min, a total space velocity of 1200 / h, and a reaction temperature of 450° C. Sampling and analysis after 6 hours of reaction revealed a 48.5% conversion of the reactant CH2FCF3 (HFC-134a) and a 100% selectivity for the product CF2=CHF. Furthermore, sampling and analysis after 28 hours of catalytic reaction revealed a 47.8% conversion of the reactant HFC-134a and a 100% selectivity for the product CF2=CHF.

[0060] The above catalyst preparation steps were repeated, with the difference being that some conditions were changed, such as "type of metal compound", "type of phosphorus source", "molar ratio of P element in phosphorus source to metal compound", stirring time at room temperature and calcination conditions in a muffle furnace.

[0061] The different catalysts prepared under varying conditions were then applied to the reaction of HFC-134a to produce TrFE. The catalytic application parameters were repeated in the same manner as in Example 3, with the catalytic application remaining unchanged. The catalytic application results of the different catalysts are shown in Table 3.

[0062] Table 3: Preparation of TrFE by catalysis of HFC-134a

[0063]

[0064] The feed ratio in Table 3 refers to the molar ratio of phosphorus source to metal source.

[0065] In addition, control experiments were conducted using the conditions described in Table 3 for each experimental group. The only differences were that no phosphorus source was added during the catalyst preparation process and that the final catalyst was not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table C.

[0066] Table c Preparation of TrFE by catalysis of HFC-134a

[0067]

[0068]

[0069] Example 4

[0070] 7.37 g of lead oxide powder was dispersed in 61 mL of diethyl hydrogen phosphate aqueous solution at a molar ratio of diethyl hydrogen phosphate to lead oxide of 1.2. The mixture was stirred at room temperature for 4 hours, then centrifuged and dried at 65°C for 10 hours. The solid powder was then calcined in a muffle furnace at 550°C for 2.5 hours to produce a polyphosphoric acid-surface-modified lead oxide catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0071] The polyphosphoric acid surface-modified lead oxide catalyst prepared above is used to catalyze the cracking of 1,1-difluoro-1-chloroethane (HCFC-142b) to prepare 1,1-difluoroethylene (VDF).

[0072] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N2 and HCFC-142b was introduced at an N2 flow rate of 10 mL / min, an HCFC-142b flow rate of 10 mL / min, a total space velocity of 1200 / h, and a reaction temperature of 450°C. Sampling and analysis after 11 hours of reaction revealed a 95.3% conversion of the reactant 1,1-difluoro-1-chloroethane (HCFC-142b) and a 100% selectivity for the product 1,1-difluoroethylene (VDF). Furthermore, sampling and analysis after 30 hours of catalytic reaction showed a 94.8% conversion of the reactant and a 100% selectivity for the target product.

[0073] The above catalyst preparation steps were repeated, with the difference being that some conditions were changed, such as "type of metal compound", "type of phosphorus source", "molar ratio of P element in phosphorus source to metal compound", stirring time at room temperature and calcination conditions in a muffle furnace.

[0074] The different catalysts prepared under varying conditions were then applied to the reaction of preparing VDF from HCFC-142b. The catalytic application parameters were repeated in the same manner as in Example 4, with the catalytic application remaining unchanged. The catalytic application results of the different catalysts are shown in Table 4.

[0075] Table 4: Catalytic production of VDF by HCFC-142b

[0076]

[0077] The feed ratio in Table 4 refers to the molar ratio of the phosphorus source to the metal source.

[0078] In addition, control experiments were conducted using the conditions described in Table 4 for each experimental group. The only differences were that no phosphorus source was added during the catalyst preparation process and that the final catalyst was not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table d.

[0079] Table d Preparation of VDF by catalysis of HCFC-142b

[0080]

[0081]

[0082] Example 5

[0083] 6.51 g of strontium fluoride powder was dispersed in 50 mL of diethyl phosphate aqueous solution at a molar ratio of diethyl phosphate to strontium fluoride of 1.2. The mixture was stirred at room temperature for 3 hours, centrifuged, and dried at 60°C for 18 hours. The solid powder was then calcined in a muffle furnace at 550°C for 5 hours to produce a polyphosphoric acid surface-modified strontium fluoride catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0084] The polyphosphoric acid surface-modified strontium fluoride catalyst prepared above is used to catalyze the cracking of 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) to prepare 2,3,3,3-tetrafluoropropylene (HFO-1234yf).

[0085] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N₂ and HCFC-244bb was introduced at an N₂ flow rate of 10 mL / min, an HCFC-244bb flow rate of 10 mL / min, a total space velocity of 1200 / h, and a reaction temperature of 550°C. Sampling and analysis after 4 hours of reaction revealed a 91.3% conversion of the reactant HCFC-244bb and a 100% selectivity for the product HFO-1234yf. Furthermore, sampling and analysis after 20 hours of catalytic reaction showed a 92.1% conversion and 100% selectivity for the target product.

[0086] The above catalyst preparation steps were repeated, with the difference being that some conditions were changed, such as "type of metal compound", "type of phosphorus source", "molar ratio of P element in phosphorus source to metal compound", stirring time at room temperature and calcination conditions in a muffle furnace.

[0087] The different catalysts prepared under varying conditions were then applied to the reaction of HCFC-244bb to produce HFO-1234yf. The catalytic application parameters were repeated in the same manner as in Example 5, with the catalytic application remaining unchanged. The catalytic application results of the different catalysts are shown in Table 5.

[0088] Table 5: Catalytic preparation of HFO-1234yf by HCFC-244bb

[0089]

[0090] The feed ratio in Table 5 refers to the molar ratio of phosphorus source to metal source.

[0091] In addition, control experiments were conducted using the conditions described in Table 5 for each experimental group. The only differences were that no phosphorus source was added during catalyst preparation and that the final catalysts were not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table e.

[0092] Table e Catalytic preparation of HFO-1234yf from HCFC-244bb

[0093]

[0094]

[0095] Example 6

[0096] 6.98 g of nickel oxide powder was dispersed in 69 mL of diethyl hydrogen phosphate aqueous solution at a molar ratio of diethyl hydrogen phosphate to nickel oxide of 1.1. The mixture was stirred at room temperature for 4 hours, then centrifuged and dried at 60°C for 18 hours. The solid powder was then calcined in a muffle furnace at 500°C for 4 hours to produce a polyphosphoric acid surface-modified nickel oxide catalyst. The resulting catalyst sample was pelletized at 10-20 MPa, crushed, and sieved using a 20-40 mesh sieve.

[0097] The nickel oxide catalyst surface-modified with polyphosphoric acid prepared above is used to catalyze the cracking of dichlorodifluoroethane (HCFC-132b) to prepare 1,1-difluoro-2-chloroethylene.

[0098] The reaction conditions were as follows: a fixed-bed reactor was loaded with 1 mL of catalyst, a mixture of N₂ and HCFC-132b was introduced at an N₂ flow rate of 10 mL / min, an HCFC-132b flow rate of 10 mL / min, a total space velocity of 1200 / h, and a reaction temperature of 550°C. Sampling and analysis after 11 hours of reaction revealed a 79.1% conversion of the reactant HCFC-132b and a 100% selectivity for the product 1,1-difluoro-2-chloroethylene. Furthermore, sampling and analysis after 7 hours of catalytic reaction showed a 79.6% conversion of the reactant and a 100% selectivity for the target product.

[0099] The above catalyst preparation steps were repeated, with the difference being that some conditions were changed, such as "type of metal compound", "type of phosphorus source", "molar ratio of P element in phosphorus source to metal compound", stirring time at room temperature and calcination conditions in a muffle furnace.

[0100] The different catalysts prepared under varying conditions were then applied to the reaction of 1,1-difluoro-2-chloroethylene from HCFC-132b. The catalytic application parameters were repeated in the same manner as in Example 18, with the catalytic application remaining unchanged. The catalytic application results of the different catalysts are shown in Table 6.

[0101] Table 6: Catalytic preparation of 1,1-difluoro-2-chloroethylene by HCFC-132b

[0102]

[0103] The feed ratio in Table 6 refers to the molar ratio of the phosphorus source to the metal source.

[0104] In addition, control experiments were conducted using the conditions described in Table 6 for each experimental group. The only differences were that no phosphorus source was added during the catalyst preparation process and that the final catalyst was not surface-modified with polyphosphoric acid. The catalytic performance of each control catalyst is shown in Table f.

[0105] Table f Catalytic preparation of 1,1-difluoro-2-chloroethylene by HCFC-132b

[0106]

[0107] The contents described in this specification are merely an enumeration of 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 embodiments.

Claims

1. Application of a metal-based catalyst modified with polyphosphoric acid, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of removing HF from 1,1-difluoroethane in the gas phase to prepare vinyl fluoride; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Al, Cr, Ba, Mg or Co; The phosphorus sources of polyphosphoric acid include sodium dihydrogen phosphate, sodium phosphite, ammonium phosphate or diethyl phosphate.

2. The use according to claim 1, characterized in that The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Al or Cr.

3. Application of a metal-based catalyst modified with polyphosphoric acid surface, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of removing HF from 1,1,1,3,3-pentafluoropropane in the gas phase to prepare 1,3,3,3-tetrafluoropropene; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Ni or Al; The phosphorus source of polyphosphoric acid includes sodium dihydrogen phosphate or triethyl phosphate.

4. Application of a metal-based catalyst modified with polyphosphoric acid surface, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of removing HF from HFC-134a in the gas phase to produce CF2=CHF; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Mg, Mn or Zn; The phosphorus sources of polyphosphoric acid include trimethyl phosphate, ammonium phosphate, sodium phosphite or diethyl hydrogen phosphate.

5. Application of a metal-based catalyst modified with polyphosphoric acid surface, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of removing HF from 1,1-difluoro-1-chloroethane in the gas phase to prepare 1,1-difluoroethylene; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Pb, Ba or Al; The phosphorus source of polyphosphoric acid includes diethyl hydrogen phosphate, sodium dihydrogen phosphate or phosphoric acid.

6. Application of a metal-based catalyst modified with polyphosphoric acid surface, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of HCFC-244bb gas phase de-HF to produce HFO-1234yf; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Sr, Cr, Mg or Fe; The phosphorus source of polyphosphoric acid includes diethyl phosphate, phosphoric acid, trimethyl phosphate or phosphorous acid.

7. Application of a metal-based catalyst modified with polyphosphoric acid surface, characterized in that The catalyst is composed of a metal compound and polyphosphoric acid modified on its surface; The catalyst is used to catalyze the reaction of removing HF from HCFC-132b in the gas phase to prepare 1,1-difluoro-2-chloroethylene; The catalyst is prepared by adding a metal compound and a phosphorus source of polyphosphoric acid as raw materials. The metal compound is added to a phosphorus source solution, stirred for reaction, and then a solid product is separated and calcined in an air atmosphere. The molar ratio of the P element in the phosphorus source to the metal compound is 0.1 to 5:

1. The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Ni, Zr, Cu, Ce, Zn or Mg; The phosphorus source of polyphosphoric acid includes diethyl hydrogen phosphate, sodium dihydrogen phosphate, trimethyl phosphite, diethyl phosphate or phosphorous acid.

8. The use according to claim 7, characterized in that The metal compounds in the catalyst include fluorides, sulfates, nitrates or oxides of Ce, Zn or Mg.

9. The use according to any one of claims 1 to 7, characterized in that The molar ratio of the P element in the phosphorus source to the metal compound is 0.5-3:1, the stirring reaction is carried out at room temperature for 1-10 hours, and the calcination is carried out in a muffle furnace at 300-600° C. for 1-8 hours.

10. The use according to claim 9, characterized in that The molar ratio of the P element in the phosphorus source to the metal compound is 0.5-1.5:1, the stirring reaction is carried out at room temperature for 1.5-6 hours, and the calcination is carried out at 450-550° C. in a muffle furnace for 2-6 hours.

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