Catalyst for preparing C2 fluorine-containing olefin through gas-phase dehydrofluorination and preparation method thereof

Abstract

The invention discloses a method for preparing a C2 fluorine-containing olefin catalyst through gas-solid phase dehydrofluorination, the catalyst is an A-B / alpha-AlF3 composite catalyst composed of a carrier alpha-AlF3, an auxiliary agent component A and an active component B, the auxiliary agent A is selected from at least one of Pt, Pd, Ru and Rh, and the active component B is selected from at least one of V, Fe, Ni, Co, Ce, Pr and W. The preparation method of the catalyst comprises the following steps: (1) preparing an alpha-AlF3 carrier by adopting a modified sol-gel method; (2) loading the auxiliary component A and the active component B on the carrier step by step by adopting a vacuum impregnation method; and (3) carrying out pre-fluorination treatment on the loaded composite catalyst by sequentially adopting N2 / HF and anhydrous HF atmospheres. When the prepared catalyst is used for preparing C2 fluorine-containing olefin through gas-solid phase dehydrofluorination, especially for preparing 1, 2-difluoroethylene through dehydrofluorination of 1, 1, 2-trifluoroethane, the low-temperature activity and stability of the catalyst are remarkably improved.

Description

Technical Field

[0001] The present invention relates to a catalyst for gas-phase dehydrofluorination reaction, in particular to a catalyst for preparing C2 fluorinated olefins by gas-phase dehydrofluorination, and more particularly to a catalyst for preparing 1,2-difluoroethylene by gas-phase dehydrofluorination of 1,1,2-trifluoroethane and a preparation method thereof. Background Art

[0002] 1,2-difluoroethylene (abbreviated as HFO-1132) has two cis-trans isomers. The GWP 100 value of trans-HFO-1132 (E) is 1.9, the critical temperature is 350.1K, the critical pressure is 6.77MPa, and the boiling point is -53°C; the GWP 100 value of cis-HFO-1132 (Z) is 1.5, the critical temperature is 365.1K, the critical pressure is 5.32MPa, and the boiling point is -26°C. As a typical C2 fluorinated olefin, HFO-1132 is not only a polymer monomer for the development of new polymeric materials, but also a fourth-generation new HFO-type low-GWP refrigerant. Its refrigeration efficiency (COP) and refrigerating capacity are comparable to those of the currently widely used high-GWP household air-conditioning refrigerants R410a, R32, and automotive air-conditioning refrigerant R134a. This working fluid can form a composition with HFO-1234ze, trifluoroethylene, HFC-125, HFC-152a, HCFC-123, etc. and be applied in heat transfer fields such as heat pumps, refrigeration, and refrigeration units; in addition, it can also form a composition with HFO-1234yf, etc. and be applied to electric vehicle refrigerants. Therefore, HFO-1132 has become a hot research alternative product under the increasingly strict environmental protection of the ozone layer.

[0003] 1,1,2-trifluoroethane (abbreviated as HFC-143) is a by-product of the hydrogenation and dechlorination of chlorotrifluoroethylene (CTFE) to prepare trifluoroethylene (TrFE). Currently, it is mostly burned in the fluorochemical industry chain, but the incineration treatment cost is high and there is a phenomenon of resource waste. Therefore, it is necessary to carry out research on the resource utilization of HFC-143 by-products.

[0004] Patent WO2019216175A1 reported the technology for preparing HFO-1132 by dehydrofluorination of HFC-143. In this patent, the differences in the dehydrofluorination reaction activities of pre-fluorinated Cr2O3 catalysts at two temperatures of 350 °C and 400 °C were investigated respectively. The research showed that after the reaction for 1 h at the above two temperatures, the conversion rates of HFC-143 were 68% and 89% respectively; the selectivities of the reaction product HFO-1132 were 94% (E / Z = 24 / 70) and 90% (E / Z = 30 / 60) respectively. However, this catalyst has high toxicity and poor stability. After the reaction at 400 °C for 10 h, the reaction conversion rate rapidly decreased to 52%. It is necessary to delay carbon deposition deactivation through an oxygen atmosphere, but it is difficult to control the reaction heat release. At the same time, other by-products may also be brought about.

[0005] Patent WO2019240233A1 reported the catalytic dehydrofluorination of HFC-143 to prepare HFO-1132 using a chromium fluoride oxide catalyst under the reaction conditions of 350 - 400 °C and an O2 concentration of 5 - 15%. The research showed that the content of HFO-1132 in the reaction product was only 61% under the conditions of 350 °C and 15% O2, and the unreacted raw material HFC-143 reached 28%.

[0006] It can be found that the initial conversion rate and product selectivity of the reaction process for preparing 1,2-difluoroethylene by dehydrofluorination of 1,1,2-trifluoroethane (HFC-143) reported in the existing public patents are relatively high, but there are problems such as high biological toxicity of the catalyst, relatively high reaction temperature, poor catalyst stability, and short service life. As is well known, the reaction temperature in industry will directly affect the production energy consumption and cost; at the same time, the stability and service life of the catalyst are of great significance for reducing production costs and improving production efficiency. Therefore, it is very necessary to seek a more efficient, higher-stability and longer-life catalyst. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention proposes a multi-component composite catalyst capable of significantly improving the catalyst stability and effectively delaying the carbon deposition of the catalyst and its preparation method.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A catalyst for gas-solid phase dehydrofluorination to prepare C2 fluorinated olefins, and the catalyst composition is an A-B / α-AlF3 type multi-component composite catalyst. Among them, the catalyst carrier is α-type AlF3 (hereinafter referred to as α-AlF3); the promoter component A is at least one selected from Pt, Pd, Ru, Rh; the active component B is at least one selected from V, Fe, Ni, Co, Ce, Pr, W, etc.

[0010] The catalyst support α-AlF3 is prepared by a modified sol-gel method, and its morphology is nano-spherical particles with a specific surface area of 159 m 2 .g -1 , the pore volume is 0.48 cm 3 .g -1 , and the average pore diameter is 15.5 nm mesoporous structure with abundant weak acids or medium-strength Lewis acids on its surface.

[0011] In the catalyst, the promoter component A is preferably one of Pd and Ru; the active component B is preferably one of Fe, Ni, and Pr.

[0012] The loading amount of the promoter component A in the catalyst is 0.01% - 2.0% (calculated based on the mass of the carrier α-AlF3), and the loading amount of the active component B is 1 - 20%.

[0013] As a further preference, the loading amount of the promoter component A is 0.01% - 1.0%, and the loading amount of the active component B is 1 - 10%.

[0014] The dehydrofluorination catalyst described in the present invention is applied to the catalytic dehydrofluorination reaction of 1,1,2-trifluoroethane (HFC-143) as follows:

[0015]

[0016] The reaction system pressure of the method of the present invention is atmospheric pressure. The raw material 1,1,2-trifluoroethane enters the reactor after passing through a mass flowmeter and a vaporizer. The reaction temperature is 300 - 500 °C, and the raw material space velocity is 100 - 800 h -1 , and the reaction time is 1 - 100 h. Preferably, the reaction temperature is 350 - 400 °C, the reaction space velocity is 100 - 400 h -1 , and the reaction time is 1 - 50 h. The reaction is carried out in a tubular reactor made of corrosion-resistant Monel 400 material or Inconel 600 material.

[0017] The product 1,2-difluoroethylene obtained from the above reaction is cis-1,2-difluoroethylene and / or trans-1,2-difluoroethylene.

[0018] In the research process of the present invention, it is found that: the gas-phase dehydrohalogenation reaction of hydrofluorocarbons is essentially an elimination process, and its reaction mechanism mainly has three mechanisms: E1, E2, and E1cb. Among them, the E1 mechanism: the carbon-halogen bond C-X in the reaction raw material molecule breaks to generate C + , and then the C + -connected C-H bond breaks to remove the proton H + to complete the elimination of HX reaction; and for some C +Rearrangement occurs, and the corresponding isomers are also generated; in the E2 mechanism, the reaction is completed by the interaction between free X and H. The E1cb mechanism mainly involves the cleavage of C-H to form C - , and then the elimination of X- from C to complete the reaction. The specific reaction mechanism is shown below.

[0019]

[0020] Studies have shown that the dehydrofluorination reaction of fluoroalkanes proceeds through the E1 mechanism, that is, the C-F bond is first activated at the beginning of the reaction, broken to form a carbocation, and then the elimination of H at the β-position occurs to complete the reaction. Due to the characteristics of the C-F bond in hydrofluoroalkanes, such as short bond length, high polarity, and low polarizability, the dissociation energy of the C-F bond is as high as 513.8 ± 10.0 kJ / mol, showing high chemical inertness. Therefore, the cleavage of the C-F bond has become the key step in the dehydrofluorination reaction of fluoroalkanes. It has been found that the dehydrofluorination reaction itself is a highly corrosive environment, so the choice of catalyst is mainly limited to AlF3, chromium fluoride CrO x , MgF2, etc. The activation of the C-F bond usually occurs at the coordinatively unsaturated metal sites or fluorine defect sites on these metal fluorides, that is, the Lewis acidic sites. The F atoms with strong electronegativity can be chemisorbed by the Lewis acid sites, accelerating the cleavage of the C-F bond. However, if the Lewis acidity on the catalyst surface is too strong, although this helps the cleavage of the C-F bond, it also promotes the dissociation of C + ions, and the unsaturated olefins in the products polymerize and coke, forming carbon deposits that deactivate the catalyst; when the Lewis acidity on the catalyst surface is too weak, the C-F bond is difficult to break, hindering the progress of the dehydrofluorination reaction. That is to say, the Lewis acidic sites on the catalyst surface are both the reaction active centers and the carbon deposition centers.

[0021] Therefore, finding a suitable catalyst and controlling the acid amount of the catalyst are the key contents of the dehydrofluorination reaction of hydrofluoroalkanes. Modifying the dehydrofluorination catalyst with noble metals Pd, Pt, Ru can not only improve the structural stability of the catalyst during calcination and reaction, avoid crystal form changes and structural collapse, but also help decompose the olefin by-products that polymerize and coke in the decomposition reaction, so that the Lewis acidic sites of the catalyst are regenerated in-situ and the service life of the catalyst is extended. Modifying the catalyst with transition metals Ni, Fe, etc. can not only promote the dissociation of the C-H bond in the raw material molecules, thus accelerating the removal of HF; but also can regulate the strength and acid density of the acidic sites on the catalyst surface, improve the competitive adsorption of the Lewis acidic active sites on the catalyst surface for the raw materials, weaken the adsorption ability of the olefin products and by-products on the active sites, and to a certain extent avoid the reduction of the number of effective active sites caused by the long-term residence of the olefin products and by-products on the adsorption sites and the occurrence of olefin polymerization and coking.

[0022] The A-B / α-AlF3 catalyst of the present invention is loaded onto the surface of the support by a stepwise vacuum impregnation method, which specifically includes: a support preparation step, a promoter component A vacuum impregnation step, a promoter component A hydrogen reduction step, an active component B vacuum impregnation step, and a catalyst pre-fluorination step.

[0023] In a preferred embodiment, the A-B / α-AlF3 catalyst is prepared by the following steps:

[0024] S1. The support preparation method is a modified sol-gel method, which includes the following steps:

[0025] A1: Weigh the metal organic alkoxide precursor into a PTFE tank, and add 200 ml of anhydrous ethylene glycol and 20 ml of polyethylene glycol respectively;

[0026] A2: Place the PTFE tank containing the above mixture in a low-temperature circulating bath at -10 to -20 °C for low-temperature stirring. At the same time, gradually add the prepared 20 wt% HF solution dropwise to the above solution and continue stirring for 8 to 12 h, then stir at 80 °C for 6 h, followed by filtration and centrifugation, and drying at 120 °C to obtain a yellow block-shaped catalyst precursor;

[0027] A3: Calcinate the above yellow block-shaped catalyst precursor in an air atmosphere at 300 to 500 °C for 3 to 5 h to obtain the metal fluoride support α-AlF3.

[0028] S2. Promoter component A vacuum impregnation: Place the beaker containing the support in a vacuum vessel, and evacuate the system pressure to about -0.05 to -0.06 MPa; Weigh the precious metal chloride according to the loading amount, and add an appropriate amount of 0.1 mol / L dilute hydrochloric acid and deionized water. The fully dissolved aqueous solution of the precious metal chloride is added dropwise to the surface of the support through a micro-injection pump at a rate of 0.5 to 5 ml / min. After completion of impregnation, dry at 120 °C for 6 to 10 h.

[0029] S3. Promoter component A hydrogen reduction: Transfer the catalyst obtained in S2 to a hydrogen reduction reaction furnace, and reduce it at 200 to 350 °C for 1 to 3 h in a reducing atmosphere of N2 / H2 = 2:1 to 4:1 to obtain the A / α-AlF3 catalyst.

[0030] S4. Active component B vacuum impregnation: Weigh the second active component precursor according to the loading amount, add an appropriate amount of deionized water to dissolve it evenly, and then, under a negative pressure system of -0.05 to -0.06 MPa, add the aqueous solution of the precursor dropwise to the surface of the catalyst obtained in step S3 through a micro-injection pump at a rate of 0.5 to 5 ml / min. After completion of impregnation, dry at 120 °C for 6 to 10 h, and calcine at 400 to 550 °C for 2 to 4 h.

[0031] S5. Catalyst pre-fluorination: Pretreat at 200 - 300 °C for 1 - 3 h under the atmosphere condition of N2 / HF = 2:1 - 3:1; Pretreat for 2 - 5 h at 300 - 400 °C in an anhydrous HF atmosphere to obtain the A - B / α - AlF3 catalyst.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The present invention uses the modified sol - gel method to prepare the α - AlF3 support with spherical particles having a large specific surface area. The promoter and active components are dispersed on the surface of the support by the step - by - step vacuum impregnation method. The synergistic effect of the three is significant. The acidity of the catalyst is moderate, the active components are evenly dispersed, and it can in - situ remove the surface carbon deposition of the catalyst while maintaining high stability, reducing the blockage and poisoning inactivation of the active site pores of the catalyst. When used in the gas - solid phase dehydrofluorination reaction, especially in the dehydrofluorination reaction of 1,1,2 - trifluoroethane, it can better delay the carbon deposition inactivation of the catalyst, thereby improving the stability and service life of the catalyst.

[0034] 2. The starting material 1,1,2 - trifluoroethane (HFC - 143) of the present invention is a by - product of the hydrogenation and dechlorination of chlorotrifluoroethylene (CTFE) to prepare trifluoroethylene (TrFE), and the CTFE raw material belongs to the company's advantageous products and is relatively easy to obtain. Through the resource utilization of by - products and the expansion of their uses, not only can the by - product 1,1,2 - trifluoroethane be converted into high - value - added and environmentally friendly fluorine - containing olefin monomers and fluorine - containing refrigerants, but also the production and by - product treatment costs of the enterprise can be greatly reduced.

[0035] Description of the accompanying drawings

[0036] Appendix Figure 1 It is the X - ray diffraction pattern of the catalyst support α - AlF3;

[0037] Appendix Figure 2 It is the comparison of the thermogravimetric diagrams of Cr - based and Al - based catalysts after reacting for 50 h;

[0038] Appendix Figure 3 It is the NH3 - TPD comparison diagram of two catalysts, fluorinated Cr2O3 and Pd - Ni - AlF3;

[0039] Appendix Figure 4 It is the scanning electron microscope image (SEM) of the nano - spherical particle α - AlF3. Detailed implementation manners

[0040] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific implementation manners. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions, and equivalent solutions that may be included within the scope of the claims.

[0041] Preparation Example 1: Preparation of α-AlF3 Support

[0042] Weigh 91.8 g of aluminum isopropoxide, add 200 mL of anhydrous ethylene glycol, fully dissolve to form a suspension solution, then transfer it to a low-temperature reaction tank at -20 °C and continue stirring. Gradually add 135 g of 20% HF solution dropwise, continue stirring for 12 h, then stir at 80 °C for 6 h, followed by washing, filtering, and centrifuging. Dry at 120 °C to obtain a yellow block, and calcine in an air atmosphere at 400 °C for 4 h to obtain the AlF3 support.

[0043] Preparation Example 2: Preparation of 1% Pd / AlF3 Catalyst

[0044] Weigh 10 g of the AlF3 support prepared in Preparation Example 1 and place it in a vacuum impregnation device. Use a vacuum pump to draw the pressure of the device to a negative pressure of about -0.05 to -0.06 MPa; weigh 1.79 g of PdCl2 according to the active component loading amount, and add 10 ml of 0.1 mol / L dilute hydrochloric acid and deionized water. Stir and dissolve at 60 °C for 2 h. The obtained precious metal chloride aqueous solution is added dropwise to the surface of the AlF3 support through a micro-injection pump. The device is in a vacuum state during the impregnation process. After impregnation, it needs to be dried at 120 °C for 6 h. Then transfer the PdCl2 / AlF3 catalyst to a hydrogen reduction reaction furnace and reduce it at 300 °C for about 2 h in a reducing atmosphere of N2 / H2 = 2:1 (H2 flow rate is 30 ml / min) to obtain the 1% Pd / AlF3 catalyst.

[0045] Preparation Example 3: Preparation of 1% Pd - 5% NiF2 / AlF3 Catalyst

[0046] Place the catalyst obtained in Preparation Example 2 in a vacuum impregnation device. Use a vacuum pump to draw the pressure of the device to a negative pressure of about -0.05 to -0.06 MPa; weigh 2.16 g of nickel acetate tetrahydrate according to the active component Ni loading amount, and add an appropriate amount of deionized water solution. After sufficient mixing, add it dropwise to the surface of the 1% Pd / AlF3 catalyst through a micro-injection pump. The device is in a vacuum state during the impregnation process. After impregnation, it needs to be dried at 120 °C for 6 h and calcined at 500 °C for 3 h. After calcination, press and screen the catalyst into 10 - 20 mesh particles at a pressure of 10 - 15 MPa. Before catalyst evaluation, pretreat it at 250 °C for 2 h in an atmosphere of N2 / HF = 3:1; pretreat it at 300 °C in an anhydrous HF atmosphere for 3 h to obtain the 5% NiF2 - 1% Pd / AlF3 catalyst.

[0047] Preparation Example 4: Preparation of 1% Ru - 5% NiF2 / AlF3 Support

[0048] The operation of this example is the same as that of Preparation Example 3, except that: the first active component precursor is changed to 2.09 g of RuCl3, and the others remain unchanged. The obtained catalyst is subjected to tabletting and fluorination pretreatment to obtain a shaped catalyst. Preparation Example 5: Preparation of 1% Pd - 5% FeF3 / AlF3 support

[0049] The operation of this example is the same as that of Preparation Example 3, except that: the second active component precursor is changed to 21.21 g of Fe(NO3)3·9H2O, and the others remain unchanged. The obtained catalyst is subjected to tabletting and fluorination pretreatment to obtain a shaped catalyst.

[0050] Preparation Example 6: Preparation of 0.5% Pd - 5% NiF2 / AlF3 support

[0051] The operation of this example is the same as that of Preparation Example 3, except that: the first active component precursor is changed to 0.9 g of PdCl2, and the others remain unchanged. The obtained catalyst is subjected to tabletting and fluorination pretreatment to obtain a shaped catalyst. Preparation Example 7: Preparation of 1% Pd - 5% PrF3 / AlF3 support

[0052] The operation of this example is the same as that of Preparation Example 3, except that: the second active component precursor is changed to 22.85 g of Pr(NO3)3·6H2O, and the others remain unchanged. The obtained catalyst is subjected to tabletting and fluorination pretreatment to obtain a shaped catalyst.

[0053] Preparation Example 8: Preparation of 1% Pd - 10% NiF2 / AlF3 support

[0054] The operation of this example is the same as that of Preparation Example 3, except that: the first active component precursor is changed to 27.65 g of nickel acetate tetrahydrate, and the others remain unchanged. The obtained catalyst is subjected to tabletting and fluorination pretreatment to obtain a shaped catalyst.

[0055] Example 1

[0056] The raw material 1,1,2-trifluoroethane (HFC-143) is vaporized in the vaporization chamber and then enters the gas-solid phase dehydrofluorination reactor (the catalyst is 1% Pd - 5% NiF2 / α-AlF3), the reaction space velocity is 240 h -1 , the reaction temperature is 350 °C, and the reaction product is 1,2-difluoroethylene (HFO-1132), including cis-1,2-difluoroethylene and trans-1,2-difluoroethylene. The reaction products are analyzed by gas chromatography after 1 h, 10 h, and 50 h respectively. The specific reaction results are shown in Table 1.

[0057] Table 1 Dehydrofluorination reaction results of 1% Pd - 5% NiF2 / AlF3 at 350 °C

[0058]

[0059] Example 2

[0060] The operation of this example is the same as that of Example 1, except that: in the gas-phase dehydrofluorination reaction step, the reaction temperature is 400 °C and the continuous reaction is carried out for 1 h, 10 h, and 50 h to obtain the dehydrofluorination performance. The specific results are shown in Table 2:

[0061] Table 2 Dehydrofluorination reaction results of 1% Pd - 5% NiF2 / AlF3

[0062]

[0063] Example 3

[0064] The operation of this example is the same as that of Example 1, except that: in the gas-phase dehydrofluorination reaction step, the content of the precious metal component Pd in the catalyst is changed to 0.5%, that is, 0.5% Pd - 5% Ni / AlF3. The specific results are shown in Table 3:

[0065] Table 3 Dehydrofluorination reaction results of 0.5% Pd - 5% NiF2 / AlF3

[0066]

[0067]

[0068] Example 4

[0069] The operation of this example is the same as that of Example 1, except that: in the gas-phase dehydrofluorination reaction step, the content of the second component Ni in the catalyst is changed to 10%, that is, 1% Pd - 10% Ni / AlF3. The specific results are shown in Table 4:

[0070] Table 4 Dehydrofluorination reaction results of 1% Pd - 10% NiF2 / AlF3

[0071]

[0072] Examples 5 - 7

[0073] The operation of this example is the same as that of Example 1, except that: in the gas-phase dehydrofluorination reaction step, the dehydrofluorination performance is obtained at reaction temperatures of 300 °C, 450 °C, and 500 °C respectively. The specific results are shown in Table 5:

[0074] Table 5 Dehydrofluorination reaction results of 1% Pd - 5% NiF2 / AlF3 at different temperatures

[0075]

[0076] By investigating the reactivity of HFC-143 at different temperatures, it was found that when the reaction temperature was 350-450 °C, the conversion rate of HFC-143 raw material and the selectivity of HFO-1132 product could be better balanced.

[0077] Examples 8-11

[0078] The operation of this example is the same as that of Example 1, except that: in the gas-phase dehydrofluorination reaction step, the reaction space velocities are 120 h -1 , 360 h -1 , 480 h -1 , 720 h -1 respectively, and the dehydrofluorination reaction results are shown in Table 6 below.

[0079] Table 6 Dehydrofluorination reaction results of 1% Pd-5% NiF2 / AlF3 at different space velocities

[0080]

[0081] By investigating the reactivity of HFC-143 under different space velocity conditions, it was found that when the reaction space velocity was 120-720 h -1 , the conversion rate of HFC-143 raw material and the selectivity of HFO-1132 product could be better balanced.

[0082] Example 12

[0083] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the second component Ni of the catalyst is replaced by Fe, that is, 1% Pd-5% FeF3 / AlF3, and other operations remain unchanged. The specific reaction results are shown in Table 7.

[0084] Table 7 Dehydrofluorination reaction results of 1% Pd-5% FeF3 / AlF3 at 350 °C

[0085]

[0086] Example 13

[0087] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the second component Ni of the catalyst is replaced by Pr, that is, 1% Pd-5% PrF3 / AlF3, and other operations remain unchanged. The specific reaction results are shown in Table 8.

[0088] Table 8 Dehydrofluorination reaction results of 1% Pd-5% PrF3 / AlF3 at 350 °C

[0089]

[0090] Example 14

[0091] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the first component Pd of the catalyst is replaced by Ru, that is, 1% Ru - 5% NiF2 / AlF3, and other operations remain unchanged. The specific reaction results are shown in Table 9.

[0092] Table 9 Dehydrofluorination reaction results of 1% Ru - 5% NiF2 / AlF3 at 350°C

[0093]

[0094] Comparative Example 1

[0095] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the catalyst is only the carrier α - AlF3 prepared by the sol - gel method, and other operations remain unchanged. The reaction results are shown in Table 10.

[0096] Table 10 Dehydrofluorination reaction results of modified α - AlF3 prepared by the sol - gel method at 350°C

[0097]

[0098] Comparative Example 2

[0099] The operation of this example is the same as that of Comparative Example 1, except that: in the dehydrofluorination reaction step, the catalyst AlF3 is prepared by the precipitation method, and other operations remain unchanged. The reaction results are shown in Table 11.

[0100] 11 Dehydrofluorination reaction results of AlF3 prepared by the precipitation method at 350°C

[0101] Comparative Example 3

[0102] The operation of this example is the same as that of Comparative Example 1, except that: in the dehydrofluorination reaction step, the catalyst AlF3 is prepared by the mechanical mixing method, and other operations remain unchanged. The reaction results are shown in Table 12.

[0103] Table 12 Dehydrofluorination reaction results of AlF3 prepared by the mechanical mixing method at 350°C

[0104]

[0105] Comparative Example 4

[0106] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the crystal form of the catalyst carrier is changed to γ - AlF3, and other operations remain unchanged. The reaction results are shown in Table 13.

[0107] Table 13 Reaction Results of Pd-Ni Bicomponent Catalyst Supported on γ-AlF3 Carrier at 350°C

[0108]

[0109] Comparative Example 5

[0110] The operation of this example is the same as that of Comparative Example 1, except that: in the dehydrofluorination reaction step, the catalyst carrier AlF3 is prepared by the precipitation method, and other operations remain unchanged. The reaction results are shown in Table 14.

[0111] Table 14 Dehydrofluorination Reaction Results of Pd-Ni Bicomponent Supported on Precipitation Method-AlF3 Carrier at 350°C

[0112]

[0113] Comparative Example 6

[0114] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the catalyst is 5% NiF / α-AlF3, and other operations remain unchanged. The specific reaction results are shown in Table 15.

[0115] Table 15 Dehydrofluorination Reaction Results of 5% NiF / AlF3 at 350°C

[0116]

[0117] Comparative Example 7

[0118] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the catalyst is 1% Pd / α-AlF3, and other operations remain unchanged. The specific reaction results are shown in Table 16.

[0119] Table 16 Dehydrofluorination Reaction Results of 1% Pd / AlF3 at 350°C

[0120]

[0121] Comparative Example 8

[0122] The operation of this example is the same as that of Example 1, except that: in the dehydrofluorination reaction step, the catalyst carrier is replaced with MgF2, and other operations remain unchanged. The specific reaction results are shown in Table 17.

[0123] Table 17 Dehydrofluorination Reaction Results of MgF2 at 350°C

[0124]

[0125] Comparative Example 9

[0126] The operation of this embodiment is the same as that of Embodiment 1, except that: in the dehydrofluorination reaction step, the catalyst is changed to fluorinated Cr2O3, and other operations remain unchanged. The specific reaction results are shown in Table 18.

[0127] Table 18 Dehydrofluorination reaction results of fluorinated Cr2O3 at 350 °C

[0128]

[0129] Comparative Example 10

[0130] The operation of this embodiment is the same as that of Embodiment 1, except that: in the dehydrofluorination reaction step, the dehydrofluorination reaction temperature is changed to 250 °C, and other operations remain unchanged. The specific reaction results are shown in Table 19.

[0131] Table 19 Dehydrofluorination reaction results of 1% Pd - 5% NiF2 / AlF3 at 250 °C

[0132]

Claims

1. A catalyst for the gas-solid phase dehydrofluorination to prepare C2 fluorinated olefins, characterized in that: The catalyst is an AB / α-AlF3 multi-component composite catalyst composed of a carrier, an auxiliary component A and an active component B, wherein: The carrier is α-type AlF3; The catalyst promoter component A is selected from at least one of Pt, Pd, Ru and Rh; The catalyst active component B is selected from at least one of V, Fe, Ni, Co, Ce, Pr and W.

2. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 1, characterized in that: The catalyst promoter component A is preferably one of Pd and Ru; The catalyst active component B is preferably at least one of Fe, Ni and Pr.

3. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 1, characterized in that: The loading amount of the auxiliary component A is 0.01% to 2.0%, and the loading amount of the active component B is 1% to 20%.

4. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 3, characterized in that: The loading amount of the auxiliary component A is 0.01% to 1.0%, and the loading amount of the active component B is 1% to 10%.

5. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 1, characterized in that: The AB / α-AlF3 catalyst is loaded onto the carrier surface by a step-by-step vacuum impregnation method, which specifically includes: a carrier preparation step, an auxiliary component A vacuum impregnation step, an auxiliary component A hydrogen reduction step, an active component B vacuum impregnation step, and a catalyst pre-fluorination step.

6. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 5, wherein: The carrier preparation method is a modified sol-gel method, comprising the following steps: A1: Weigh the metal organic alkoxide precursor into a PTFE tank, and add 200 ml of anhydrous ethylene glycol and 20 ml of polyethylene glycol respectively; A2: Place the PTFE tank containing the above mixed solution in a low-temperature circulation tank at -10 to -20°C and stir at low temperature. At the same time, add the prepared 20wt% HF solution dropwise into the above solution and continue stirring for 8 to 12 hours. Then, stir at 80°C for 6 hours, filter and centrifuge, and dry at 120°C to obtain a yellow block catalyst precursor. A3: Calcine the yellow block catalyst precursor at 300-500°C in air atmosphere for 3-5 hours to obtain the metal fluoride carrier α-crystalline AlF3.

7. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 5, characterized in that: The active component impregnation step adopts vacuum impregnation method to load onto the carrier surface, the vacuum impregnation pressure is -0.05 to -0.06 MPa, and the impregnation liquid is added dropwise onto the carrier surface at a speed of 0.5 to 5 ml / min through a micro-injection pump.

8. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 5, characterized in that: The hydrogen reduction step is carried out in a reducing atmosphere of N2 / H2=2:1-4:1, the reduction temperature is 200-350°C, and the reduction time is 1-3h.

9. The catalyst for preparing C2 fluorinated olefins by dehydrofluorination according to claim 5, characterized in that: The pre-fluorination step is first carried out in a N2 / HF=2:1~3:1 atmosphere, with a pre-fluorination temperature of 200~300°C and a pre-fluorination time of 1~3h; then it is carried out in an anhydrous HF atmosphere, with a pre-fluorination temperature of 300~400°C and a pre-fluorination time of 2~5h.

10. A method for preparing C2 fluorinated olefins, using 1,1,2-trifluoroethane as a raw material, and preparing 1,2-difluoroethylene through a dehydrofluorination reaction, characterized in that: The catalyst described in any one of claims 1 to 9 is used as the reaction catalyst.

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