A catalyst for the preparation of pentafluoropropylene from hexafluoropropane, its preparation method and application

Abstract

This invention relates to a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, its preparation method, and its application. The catalyst includes a support, and an active component and an auxiliary agent supported on the support. The active component includes transition metal oxides, specifically cerium oxide and zirconium oxide. The auxiliary agent includes rare earth oxides, specifically yttrium. The support comprises a molecular sieve with a mesoporous structure. This invention uses transition metal oxides cerium oxide and zirconium oxide as the active components and yttrium oxide as the auxiliary agent, which can form a good solid solution structure and create a certain oxygen vacancy concentration within the solid solution structure. When supported on a support, this catalyst for the preparation of pentafluoropropylene from hexafluoropropane exhibits high conversion rate, selectivity, and stability.

Description

Technical Field

[0001] This invention relates to the field of fluorochemical technology, specifically to the preparation of pentafluoropropylene from hexafluoropropane, and more particularly to a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, its preparation method, and its application. Background Technology

[0002] The dehydrogenation of hexafluoropropane to produce pentafluoropropylene is a reaction with great industrial value in the fluorochemical field. As an environmentally friendly fluorinated olefin, pentafluoropropylene has zero ozone depletion potential and low global warming potential, and is widely used in the synthesis of refrigerants, foaming agents, fluoropolymer monomers and fine chemicals.

[0003] However, the dehydrogenation of hexafluoropropane to produce pentafluoropropylene is a strongly endothermic reaction that requires high temperature conditions (usually 400℃~450℃). Existing catalysts do not perform well in terms of conversion and selectivity, and the conversion rate of hexafluoropropane can only reach 20%-30%, resulting in low production efficiency and unstable product quality.

[0004] CN117943030A discloses a method for preparing a catalyst for synthesizing 1,2,3,3,3-pentafluoropropylene and its application. The preparation method includes the following steps: (1) mixing the active component of the support, the pore expander, and the binder, and transferring the mixture to a kneader after uniform mixing. Nitric acid solution is added to the mixture to form a binder. The binder is kneaded, extruded, and cut by the kneader, and then dried and calcined to obtain the support. The active component of the support is composed of at least one of magnesium dihydrogen phosphate, zirconium oxychloride, and zinc oxide, along with titanium oxide and aluminum oxide. (2) Using an equal-volume impregnation method, the auxiliary component and the active component are loaded separately. (3) Reduction is performed to obtain the catalyst. The catalyst provided by this invention has high activity, good stability, and good product selectivity when preparing 1,2,3,3,3-pentafluoropropylene, but it has problems such as poor dispersion of the active component and easy sintering at high temperatures.

[0005] CN111484391A discloses a method for preparing 1,2,3,3,3-pentafluoropropylene from hexafluoropropylene. The method uses a mixture of one or more halide oxides or derivatives of transition metals, Group IIA, and Group IIIA metals, and a Group VIII metal-based compound as a solid mixture catalyst. A dual-bed packing is employed, with the Group VIII metal-based compound on top and one or more halide oxides or derivatives of transition metals, Group IIA, and Group IIIA metals on the bottom. The method involves a one-step gas-phase reaction of hexafluoropropylene with hydrogen to prepare 1,2,3,3,3-pentafluoropropylene. The solid mixture catalyst used in this method exhibits higher selectivity and reaction stability for pentafluoropropylene.

[0006] CN119118778A discloses a catalytic synthesis method for 1,1,3,3,3-pentafluoropropylene, comprising: (1) feeding 1,1,1,3,3,3-hexafluoropropane into a reactor and reacting it under the action of a catalyst to obtain crude 1,1,3,3,3-pentafluoropropylene, wherein the catalyst contains one of Cr2O3 and metal oxides of Al, Bi, and Co; (2) washing the crude 1,1,3,3,3-pentafluoropropylene with water, alkali, and drying it, and then passing it into a first distillation column for separation to obtain a mixture containing 1,1,3,3,3-pentafluoropropylene and a small amount of byproducts; (3) passing the mixture containing 1,1,3,3,3-pentafluoropropylene and a small amount of byproducts into a second distillation column for separation to obtain the 1,1,3,3,3-pentafluoropropylene product. This invention has the advantages of simple process, high catalyst activity, low cost, and green environmental protection, but it has the defects of difficult control of oxygen vacancy concentration and insufficient selectivity.

[0007] Therefore, it is of great significance to provide a catalyst for the preparation of pentafluoropropylene from hexafluoropropane with high conversion and selectivity and good stability, as well as a method for preparing pentafluoropropylene from hexafluoropropane. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, its preparation method, and its applications. This invention uses transition metal oxides cerium oxide and zirconium oxide as active components, and yttrium oxide as a promoter, to construct a favorable solid solution structure. A specific oxygen vacancy concentration is formed within the solid solution structure, which, when supported on a carrier, serves as a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, exhibiting high conversion rate, selectivity, and stability. This invention, through the design of a "cerium oxide-zirconia-yttrium oxide" solid solution structure, precisely controls the oxygen vacancy concentration, specifically addressing the three core problems of existing catalysts: low conversion rate, poor selectivity, and weak stability.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, the catalyst comprising a support, and an active component and an auxiliary agent supported on the support; the active component comprises a transition metal oxide, the transition metal oxide comprising cerium oxide and zirconium oxide; the auxiliary agent comprises a rare earth oxide, the rare earth oxide comprising yttrium oxide; and the support comprises a molecular sieve having a mesoporous structure.

[0011] This invention uses transition metal oxides cerium oxide and zirconium oxide as active components and yttrium oxide as a promoter. Yttrium oxide optimizes catalyst performance through the following mechanisms: First, it forms a more stable solid solution structure with cerium oxide and zirconium oxide, inhibiting sintering and agglomeration of the active components during high-temperature reactions and improving the catalyst's structural stability. Second, by doping yttrium, it regulates the concentration and distribution of oxygen vacancies within the solid solution, enhancing the catalyst's adsorption and activation capacity for hexafluoropropane molecules, promoting the breaking of CF bonds and the formation of the target product pentafluoropropylene. Third, it improves the interaction between the active components and the support, reducing the loss of active components and extending the catalyst's lifespan. This invention, through its "cerium oxide-zirconia-yttrium oxide" solid solution structure design, precisely controls the oxygen vacancy concentration, specifically addressing the three core problems of existing catalysts: low conversion rate, poor selectivity, and weak stability.

[0012] Preferably, the molar ratio of cerium oxide to zirconium oxide in the active component is (0.5~3):1, more preferably (1~2):1.

[0013] Preferably, the molar ratio of the transition metal oxide in the active component to the rare earth oxide in the additive is (8~17):1.

[0014] Preferably, the total mass percentage of the active component and the auxiliary agent in the catalyst is 10wt% to 20wt%.

[0015] Preferably, the molecular sieve has an average pore size of 2 nm to 5 nm and a specific surface area of ​​500 m². 2 / g~1000m 2 / g.

[0016] Preferably, the molecular sieve includes any one or a combination of at least two of MCM-41 molecular sieve, SBA-15 molecular sieve, or MCM-48 molecular sieve.

[0017] In a second aspect, the present invention provides a method for preparing a catalyst for the preparation of pentafluoropropylene from hexafluoropropane as described in the first aspect, the method comprising:

[0018] According to stoichiometric ratio, transition metal salts and rare earth salts are mixed in a solvent to obtain a precursor solution; the support is immersed in the precursor solution and dried to obtain a catalyst precursor; the catalyst precursor is calcined to obtain the catalyst for preparing pentafluoropropylene from hexafluoropropane; the transition metal salts include cerium salts and zirconium salts, and the rare earth salts include yttrium salts.

[0019] Preferably, the cerium salt includes any one or a combination of at least two of cerium nitrate, cerium chloride, cerium sulfate, cerium ammonium nitrate, or cerium ammonium sulfate.

[0020] Preferably, the zirconium salt includes any one or a combination of at least two of zirconium nitrate, zirconium oxynitrate, zirconium oxychloride, or zirconium sulfate.

[0021] Preferably, the yttrium salt includes any one or a combination of at least two of yttrium nitrate, yttrium chloride, yttrium sulfate, or yttrium acetate.

[0022] Preferably, the solvent includes water.

[0023] Preferably, the concentration of the precursor solution is 0.1 mol / L to 0.5 mol / L.

[0024] Preferably, the drying temperature is 60℃~80℃.

[0025] Preferably, the calcination temperature is 400℃~500℃.

[0026] Preferably, the roasting time is 2h to 5h.

[0027] Preferably, the heating rate of the calcination is 5℃ / min to 10℃ / min.

[0028] Preferably, the impregnation method includes equal-volume impregnation.

[0029] Thirdly, the present invention provides a method for preparing pentafluoropropylene from hexafluoropropane, the method comprising:

[0030] The catalyst for preparing pentafluoropropylene from hexafluoropropane as described in the first aspect is placed in a reaction apparatus, and then a mixture of hexafluoropropane and nitrogen is introduced into the reaction apparatus. Preheating, a first stage reaction, a second stage reaction, and a third stage reaction are carried out in sequence to prepare pentafluoropropylene; the temperature of the first stage reaction is less than the temperature of the third stage reaction, which is less than the temperature of the second stage reaction.

[0031] In the method for preparing pentafluoropropylene from hexafluoropropane provided by the present invention, the temperatures of the first, second, and third reactions are set in a gradient of "medium temperature - high temperature - medium-high temperature". By combining preheating with the three-stage reaction and using a specific catalyst, high conversion rate and high selectivity of hexafluoropropane to prepare pentafluoropropylene are achieved, thereby improving the stability of the reaction.

[0032] Preferably, the volume ratio of hexafluoropropane to nitrogen is 1:(3~5).

[0033] Preferably, the space velocity of the mixed gas is 60 h⁻¹. -1 ~180h -1 .

[0034] Preferably, the pressure in the reaction device is 0.5 MPa to 1.5 MPa.

[0035] Preferably, the preheating temperature is 150℃~200℃, and the dwell time is 10s~30s.

[0036] Preferably, the temperature of the first stage reaction is 350℃~400℃, and the residence time is 20s~60s.

[0037] Preferably, the temperature of the second stage reaction is 400℃~450℃, and the residence time is 20s~60s.

[0038] Preferably, the temperature of the third stage reaction is 380℃~420℃, and the residence time is 20s~60s.

[0039] Preferably, the heating rate of the preheating, the first stage reaction, the second stage reaction, and the third stage reaction is 5℃ / min to 10℃ / min.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention uses transition metal oxides cerium oxide and zirconium oxide as active components and yttrium oxide as an auxiliary agent to form a good solid solution structure and form a certain oxygen vacancy concentration inside the solid solution structure. When loaded on a support, it is used as a catalyst for the preparation of pentafluoropropylene from hexafluoropropane and exhibits high conversion rate, selectivity and stability.

[0042] (2) In the method for preparing pentafluoropropylene from hexafluoropropane provided by the present invention, by combining preheating with three stages of reaction at different temperatures and with a specific catalyst, the high conversion rate and high selectivity of hexafluoropropane to prepare pentafluoropropylene are achieved. Under reaction conditions of 400℃~450℃, the conversion rate of hexafluoropropane is increased to more than 50% and the selectivity reaches more than 92%, which significantly improves production efficiency and product stability and has important industrial application value. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0045] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0047] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0048] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0050] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0051] In this invention, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0052] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0053] In this invention, unless otherwise specified, it is assumed that the experiments are conducted at room temperature or a temperature conventionally set in the art. "Room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments of this invention, room temperature refers to 20°C to 30°C.

[0054] In one specific embodiment, the present invention provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, the catalyst comprising a support, and an active component and an auxiliary agent supported on the support; the active component comprises a transition metal oxide, the transition metal oxide comprising cerium oxide and zirconium oxide; the auxiliary agent comprises a rare earth oxide, the rare earth oxide comprising yttrium oxide; the support comprises a molecular sieve having a mesoporous structure.

[0055] This invention uses transition metal oxides cerium oxide and zirconium oxide as active components and yttrium oxide as an auxiliary agent to construct a good solid solution structure and form a certain oxygen vacancy concentration inside the solid solution structure. When loaded onto a support, it serves as a catalyst for the preparation of pentafluoropropylene from hexafluoropropane, exhibiting high conversion rate, selectivity and stability.

[0056] In some embodiments, the molar ratio of cerium oxide to zirconium oxide in the active components is (0.5~3):1, for example, it can be 0.5:1, 0.75:1, 1:1, 1.25:1, 1.5:1, 1.75:1, 2:1, 2.25:1, 2.5:1, 2.75:1 or 3:1, preferably (1~2):1.

[0057] In some embodiments, the molar ratio of the transition metal oxide in the active component to the rare earth oxide in the auxiliary is (8~17):1, for example, it can be 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1 or 17:1.

[0058] In some embodiments, the total mass percentage of the active component and the auxiliary agent in the catalyst is 10wt% to 20wt%, for example, it can be 10wt%, 12wt%, 14wt%, 16wt%, 18wt% or 20wt%.

[0059] Preferably, the molecular sieve has an average pore size of 2nm to 5nm, for example, 2nm, 3nm, 4nm or 5nm; and a specific surface area of ​​500m². 2 / g~1000m 2 / g, for example, could be 500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g or 1000m 2 / g. This invention selects molecular sieves with mesoporous structures and large specific surface areas as carriers to ensure uniform loading of active components.

[0060] Preferably, the molecular sieve includes any one or a combination of at least two of MCM-41 molecular sieve, SBA-15 molecular sieve, or MCM-48 molecular sieve.

[0061] In another specific embodiment, the present invention provides a method for preparing a catalyst for the preparation of pentafluoropropylene from hexafluoropropane as described in one of the foregoing specific embodiments, the preparation method comprising:

[0062] According to stoichiometric ratio, transition metal salts and rare earth salts are mixed in a solvent to obtain a precursor solution; the support is immersed in the precursor solution and dried to obtain a catalyst precursor; the catalyst precursor is calcined to obtain the catalyst for preparing pentafluoropropylene from hexafluoropropane; the transition metal salts include cerium salts and zirconium salts, and the rare earth salts include yttrium salts.

[0063] In some embodiments, the cerium salt includes any one or a combination of at least two of cerium nitrate, cerium chloride, cerium sulfate, cerium ammonium nitrate, or cerium ammonium sulfate, typically when non-limiting combinations include a combination of cerium nitrate and cerium chloride, a combination of cerium sulfate and cerium ammonium nitrate, or a combination of cerium nitrate and cerium ammonium sulfate.

[0064] In some embodiments, the zirconium salt includes any one or a combination of at least two of zirconium nitrate, zirconium oxynitrate, zirconium oxychloride, or zirconium sulfate. Typical but non-limiting combinations include a combination of zirconium nitrate and zirconium oxynitrate, or a combination of zirconium oxychloride and zirconium sulfate.

[0065] In some embodiments, the yttrium salt includes any one or a combination of at least two of yttrium nitrate, yttrium chloride, yttrium sulfate, or yttrium acetate. Typical but non-limiting combinations include a combination of yttrium nitrate and yttrium chloride, or a combination of yttrium sulfate and yttrium acetate.

[0066] In some embodiments, the solvent includes water.

[0067] In some embodiments, the concentration of the precursor solution is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0068] In some embodiments, the drying temperature is 60°C to 80°C, for example, 60°C, 65°C, 70°C, 75°C, or 80°C. The drying in this invention aims at complete solvent evaporation, and the drying time is not particularly limited.

[0069] In some embodiments, the calcination temperature is 400°C to 500°C, for example, 400°C, 420°C, 440°C, 460°C, 480°C or 500°C.

[0070] In some embodiments, the calcination time is 2h to 5h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.

[0071] In some embodiments, the heating rate of the calcination is 5°C / min to 10°C / min, for example, it can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min.

[0072] In some embodiments, the impregnation method includes equal-volume impregnation.

[0073] In yet another specific embodiment, the present invention provides a method for preparing pentafluoropropylene from hexafluoropropane, the method comprising:

[0074] The catalyst for preparing pentafluoropropylene from hexafluoropropane, as described in one of the aforementioned specific embodiments, is placed in a reaction apparatus. Then, a mixture of hexafluoropropane and nitrogen is introduced into the reaction apparatus, and preheating, a first stage reaction, a second stage reaction, and a third stage reaction are carried out sequentially to prepare pentafluoropropylene. The temperature of the first stage reaction is less than the temperature of the third stage reaction, which is less than the temperature of the second stage reaction.

[0075] In the method for preparing pentafluoropropylene from hexafluoropropane provided by the present invention, the temperatures of the first, second, and third reactions are set in a gradient of "medium temperature - high temperature - medium-high temperature". By combining preheating with the three-stage reaction and using a specific catalyst, high conversion rate and high selectivity of hexafluoropropane to prepare pentafluoropropylene are achieved, thereby improving the stability of the reaction.

[0076] In some embodiments, the volume ratio of hexafluoropropane to nitrogen is 1:(3~5), for example, it can be 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0077] In some embodiments, the space velocity of the mixed gas is 60 h⁻¹. -1 ~180h -1 For example, it could be 60h -1 80h -1 120h -1 140h-1 or 180h -1 .

[0078] In some embodiments, the pressure in the reaction device is 0.5 MPa to 1.5 MPa, for example, it can be 0.5 MPa, 0.75 MPa, 1 MPa, 1.25 MPa or 1.5 MPa.

[0079] In some embodiments, the preheating temperature is 150°C to 200°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C; the dwell time is 10s to 30s, for example, 10s, 15s, 20s, 25s or 30s.

[0080] In some embodiments, the temperature of the first reaction stage is 350°C to 400°C, for example, 350°C, 360°C, 370°C, 380°C, 390°C or 400°C; the residence time is 20s to 60s, for example, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0081] In some embodiments, the temperature of the second stage reaction is 400°C to 450°C, for example, 400°C, 410°C, 420°C, 430°C, 440°C or 450°C; the residence time is 20s to 60s, for example, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 30s.

[0082] In some embodiments, the temperature of the third reaction stage is 380°C to 420°C, for example, 380°C, 390°C, 400°C, 410°C or 420°C; the residence time is 20s to 60s, for example, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 30s.

[0083] In some embodiments, the heating rate of the preheating, the first stage reaction, the second stage reaction, and the third stage reaction is 5°C / min to 10°C / min, for example, it can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min.

[0084] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0085] Example 1

[0086] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. The catalyst comprises components with an average pore size of 3 nm and a specific surface area of ​​750 m². 2 / g of MCM-41 molecular sieve, and active components and additives supported on MCM-41 molecular sieve; the active components are cerium oxide and zirconium oxide in a molar ratio of 2:1, the additives are yttrium oxide, and the total amount of cerium oxide and zirconium oxide is in a molar ratio of 15:1 to yttrium oxide; in the catalyst, the total mass percentage of active components and additives is 15wt%.

[0087] The method for preparing the catalyst includes:

[0088] Cerium nitrate, zirconium nitrate, and yttrium nitrate were mixed in water according to stoichiometric ratio to obtain a 0.2 mol / L precursor solution. The molecular sieve support was impregnated in the precursor solution by equal volume impregnation and dried under vacuum at 70 °C to obtain a catalyst precursor. The catalyst precursor was calcined at 450 °C for 3 h by heating at a heating rate of 7 °C / min to obtain the catalyst for the preparation of pentafluoropropylene from hexafluoropropane.

[0089] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method comprising:

[0090] The prepared catalyst was placed in a fluidized bed, and a mixture of hexafluoropropane and nitrogen with a volume ratio of 1:4 was introduced, with a gas space velocity of 120 h⁻¹. -1 The reaction pressure was 1 MPa. The temperature was increased to 180℃ for 25 seconds at a heating rate of 6℃ / min. Then the temperature was increased to 380℃ for 45 seconds for the first stage reaction. The temperature was increased to 420℃ for 40 seconds for the second stage reaction. Finally, the temperature was increased to 400℃ for 50 seconds for the third stage reaction, thus preparing pentafluoropropylene.

[0091] Example 2

[0092] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. The catalyst comprises components with an average pore size of 5 nm and a specific surface area of ​​500 m². 2 / g of SBA-15 molecular sieve, and active components and additives supported on SBA-15 molecular sieve; the active components are cerium oxide and zirconium oxide in a molar ratio of 1:1, the additive is yttrium, and the total amount of cerium oxide and zirconium oxide is in a molar ratio of 8:1 to yttrium; in the catalyst, the total mass percentage of active components and additives is 10wt%.

[0093] The method for preparing the catalyst includes:

[0094] Cerium nitrate, zirconium nitrate, and yttrium nitrate were mixed in water according to stoichiometric ratio to obtain a 0.1 mol / L precursor solution. The molecular sieve support was impregnated in the precursor solution by equal volume impregnation and dried at 60°C to obtain a catalyst precursor. The catalyst precursor was calcined at a heating rate of 5°C / min to 400°C for 5 hours to obtain the catalyst for the preparation of pentafluoropropylene from hexafluoropropane.

[0095] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method comprising:

[0096] The prepared catalyst was placed in a fluidized bed, and a mixture of hexafluoropropane and nitrogen with a volume ratio of 1:3 was introduced, with a gas space velocity of 60 h⁻¹. -1 The reaction pressure was 0.5 MPa. The temperature was increased to 150℃ for 30 s preheating at a rate of 5℃ / min, then increased to 350℃ for 60 s first stage reaction, increased to 400℃ for 50 s second stage reaction, and finally increased to 380℃ for 55 s third stage reaction to prepare pentafluoropropylene.

[0097] Example 3

[0098] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. The catalyst comprises components with an average pore size of 2.5 nm and a specific surface area of ​​1000 m². 2 / g of MCM-48 molecular sieve, and active components and additives supported on MCM-48 molecular sieve; the active components are cerium oxide and zirconium oxide in a molar ratio of 1.5:1, the additive is yttrium, and the total amount of cerium oxide and zirconium oxide to yttrium is in a molar ratio of 17:1; in the catalyst, the total mass percentage of active components and additives is 20wt%.

[0099] The method for preparing the catalyst includes:

[0100] Cerium nitrate, zirconium nitrate, and yttrium nitrate were mixed in water according to stoichiometric ratio to obtain a 0.5 mol / L precursor solution. The molecular sieve support was impregnated in the precursor solution by equal volume impregnation and dried at 80°C to obtain a catalyst precursor. The catalyst precursor was calcined at 500°C for 2 hours by heating at a rate of 10°C / min to obtain the catalyst for the preparation of pentafluoropropylene from hexafluoropropane.

[0101] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method comprising:

[0102] The prepared catalyst was placed in a fluidized bed, and a mixture of hexafluoropropane and nitrogen with a volume ratio of 1:5 was introduced, with a gas space velocity of 180 h⁻¹. -1The reaction pressure was 1.5 MPa. The temperature was increased to 200℃ for 10 s preheating at a rate of 10℃ / min, then increased to 400℃ for 25 s first stage reaction, increased to 450℃ for 23 s second stage reaction, and finally increased to 420℃ for 20 s third stage reaction to prepare pentafluoropropylene.

[0103] Example 4

[0104] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of cerium oxide to zirconium oxide being 0.5:1, the catalyst is the same as in Example 1.

[0105] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate and zirconium nitrate are mixed in a molar ratio of cerium oxide to zirconium oxide of 0.5:1.

[0106] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0107] Example 5

[0108] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of cerium oxide to zirconium oxide being 3:1, the catalyst is the same as in Example 1.

[0109] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate and zirconium nitrate are mixed in a molar ratio of cerium oxide to zirconium oxide of 3:1.

[0110] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0111] Example 6

[0112] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of cerium oxide to zirconium oxide being 0.45:1, the catalyst is the same as that in Example 1.

[0113] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate and zirconium nitrate are mixed in a molar ratio of cerium oxide to zirconium oxide of 0.45:1.

[0114] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0115] Example 7

[0116] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of cerium oxide to zirconium oxide being 3.5:1, the catalyst is the same as that in Example 1.

[0117] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate and zirconium nitrate are mixed in a molar ratio of cerium oxide to zirconium oxide of 3.5:1.

[0118] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0119] Example 8

[0120] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of the total amount of cerium oxide and zirconium oxide to yttrium being 7:1, all other aspects are the same as in Example 1.

[0121] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate, zirconium nitrate and yttrium are mixed in a molar ratio of cerium oxide and zirconium oxide to yttrium of 7:1.

[0122] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0123] Example 9

[0124] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the molar ratio of the total amount of cerium oxide and zirconium oxide to yttrium being 18:1, all other aspects are the same as in Example 1.

[0125] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate, zirconium nitrate and yttrium are mixed in a molar ratio of cerium oxide and zirconium oxide to yttrium of 18:1.

[0126] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0127] Example 10

[0128] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the calcination temperature of 350°C in the preparation method, the rest is the same as in Example 1.

[0129] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0130] Example 11

[0131] This embodiment provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the calcination temperature of 550°C in the preparation method, the rest is the same as in Example 1.

[0132] This embodiment also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Embodiment 1.

[0133] Example 12

[0134] This embodiment provides a method for preparing pentafluoropropylene from hexafluoropropane. Except for not preheating, and directly raising the temperature to 380°C, 420°C and 400°C respectively to carry out the first stage reaction, the second stage reaction and the third stage reaction, the rest is the same as in Example 1.

[0135] Example 13

[0136] This embodiment provides a method for preparing pentafluoropropylene from hexafluoropropane. Except for preheating to 180°C and then directly heating to 420°C for a single reaction, the rest is the same as in Example 1.

[0137] Comparative Example 1

[0138] This comparative example provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the active component, which only includes cerium oxide, the catalyst is the same as that in Example 1.

[0139] The preparation method of the catalyst is the same as in Example 1, except that cerium nitrate and yttrium nitrate are mixed in stoichiometric proportions.

[0140] This comparative example also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Example 1.

[0141] Comparative Example 2

[0142] This comparative example provides a catalyst for the preparation of pentafluoropropylene from hexafluoropropane. Except for the active component, which only includes zirconium oxide, the catalyst is the same as that in Example 1.

[0143] The preparation method of the catalyst is the same as in Example 1, except that zirconium nitrate and yttrium nitrate are mixed in stoichiometric ratio.

[0144] This comparative example also provides a method for preparing pentafluoropropylene from hexafluoropropane, the method being the same as in Example 1.

[0145] Performance testing:

[0146] Gas chromatography was used to analyze the reaction products obtained by the methods for preparing pentafluoropropylene from hexafluoropropane provided in all the above examples and comparative examples. The conversion rate of hexafluoropropane and the selectivity for conversion to pentafluoropropylene were calculated. The standard deviation of conversion rate and selectivity were calculated through multiple experiments to characterize the stability of the reaction. The test results are shown in Table 1.

[0147] The catalytic activity, electron cloud density, and electron conductivity of the catalyst provided in Example 1 were evaluated and tested at 350°C, 400°C, and 450°C using a fixed-bed reactor, XPS, and H2-TPR. The results are shown in Table 2.

[0148] Table 1

[0149]

[0150] Table 2

[0151]

[0152] In summary, based on the data in Table 1, this invention uses transition metal oxides cerium oxide and zirconium oxide as active components and yttrium oxide as an auxiliary agent to construct a good solid solution structure. Through the design of the "cerium oxide-zirconia-yttrium oxide" solid solution structure, the oxygen vacancy concentration is precisely controlled, which specifically solves the three core problems of low conversion rate, poor selectivity, and weak stability of existing catalysts. It exhibits high conversion rate, selectivity, and stability. Under reaction conditions of 400℃~450℃, the conversion rate of hexafluoropropane is increased to over 50%, and the selectivity reaches over 92%, which significantly improves production efficiency.

[0153] According to the activity of the catalyst provided in Example 1 at 350℃, 400℃ and 450℃, the activity of the catalyst shows an increasing trend with increasing temperature. The electron cloud density and electron conductivity of the catalyst hardly change with temperature, which proves that the catalyst provided by the present invention has excellent high temperature stability and has important industrial application value.

[0154] Based on the test results of Examples 1 and 4 to 7, a suitable molar ratio of cerium oxide to zirconium oxide in the active components is beneficial for forming a solid solution structure with a suitable oxygen vacancy concentration. If the molar ratio of cerium oxide to zirconium oxide deviates from the range selected in this invention, the conversion rate of hexafluoropropane will decrease significantly.

[0155] Based on the test results of Examples 1, 8, and 9, the catalyst provided by this invention uses yttrium oxide as a promoter, which is beneficial for forming a stable solid solution structure with cerium oxide and zirconium oxide, regulating the oxygen vacancy concentration, and enhancing the catalyst's adsorption and activation ability for hexafluoropropane. When the amount of yttrium oxide added is too small, it is not conducive to the formation of a solid solution structure, the number of oxygen vacancies is insufficient, and the synergistic effect of the active components is weakened; when the amount of yttrium oxide added is too large, it is not conducive to the dispersibility of the active components, easily covers the active sites on the catalyst surface, and hinders the contact between the reaction substrate and the active center, both of which lead to a decrease in catalyst performance.

[0156] Based on the test results of Examples 1, 10, and 11, the calcination temperature affects the crystal phase structure of the catalyst, the dispersion of the active component, and the degree of solid solution formation. If the calcination temperature is too low, the precursor decomposes insufficiently, the active component cannot be completely converted into the target oxide, and the number of active sites on the catalyst is insufficient. If the calcination temperature is too high, the active component is prone to sintering and agglomeration, the solid solution structure is destroyed, the oxygen vacancy concentration decreases, and the pore structure of the support may collapse.

[0157] Based on the test results of Examples 1, 12, and 13, the method for preparing pentafluoropropylene from hexafluoropropane provided by the present invention achieves improved hexafluoropropane conversion and pentafluoropropylene selectivity through a three-stage reaction with a "medium-high-medium-high temperature" gradient setting. Preheating helps to uniformly raise the temperature of the mixed gas to the reaction initiation temperature, avoiding non-selective adsorption of raw materials on the catalyst surface at low temperatures and reducing byproduct formation. The three-stage reaction with the "medium-high-high-medium-high temperature" gradient setting facilitates the stepwise dehydrogenation of hexafluoropropane, selective CF bond breaking, and directional conversion of intermediate products, suppressing side reactions such as excessive cracking while achieving high conversion. Failure to follow the method provided by the present invention will hinder the improvement of hexafluoropropane conversion and pentafluoropropylene selectivity.

[0158] Based on the test results of Example 1 and Comparative Examples 1 and 2, in this invention, the active component includes both cerium oxide and zirconium oxide, which work synergistically with yttrium oxide to form a solid solution structure with a suitable oxygen vacancy concentration. If the active component includes only cerium oxide or only zirconium oxide, a specific solid solution structure cannot be formed, and the improvement of hexafluoropropane conversion rate and pentafluoropropylene selectivity cannot be achieved.

[0159] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A catalyst for the preparation of pentafluoropropylene from hexafluoropropane, characterized in that, The catalyst includes a support, and an active component and an additives supported on the support; The active component includes transition metal oxides, which include cerium oxide and zirconium oxide, wherein the molar ratio of cerium oxide to zirconium oxide is (0.5~3):1; The additives include rare earth oxides, and the rare earth oxides include yttrium oxide; The molar ratio of the transition metal oxide in the active component to the rare earth oxide in the additive is (8~17):

1. The carrier includes a molecular sieve with a mesoporous structure; The oxygen vacancy concentration was controlled by designing a solid solution structure of "cerium oxide-zirconia-yttrium oxide"; The catalyst is obtained by the following preparation method, the preparation method comprising: According to the stoichiometric ratio, transition metal salts and rare earth salts are mixed in a solvent to obtain a precursor solution; the support is immersed in the precursor solution and dried to obtain a catalyst precursor; the catalyst precursor is calcined to obtain the catalyst for preparing pentafluoropropylene from hexafluoropropane; the transition metal salts include cerium salts and zirconium salts, and the rare earth salts include yttrium salts. The roasting temperature is 400℃~500℃; the roasting time is 2h~5h.

2. The catalyst for preparing pentafluoropropylene from hexafluoropropane as described in claim 1, characterized in that, The total mass percentage of the active component and the auxiliary agent in the catalyst is 10wt%~20wt%; And / or, the molecular sieve has an average pore size of 2nm~5nm and a specific surface area of ​​500m². 2 / g~1000m 2 / g; And / or, the molecular sieve includes any one or a combination of at least two of MCM-41 molecular sieve, SBA-15 molecular sieve, or MCM-48 molecular sieve.

3. A method for preparing a catalyst for the preparation of pentafluoropropylene from hexafluoropropane as described in claim 1 or 2, characterized in that, The preparation method includes: According to the stoichiometric ratio, transition metal salts and rare earth salts are mixed in a solvent to obtain a precursor solution; the support is immersed in the precursor solution and dried to obtain a catalyst precursor; the catalyst precursor is calcined to obtain the catalyst for the preparation of pentafluoropropylene from hexafluoropropane. The transition metal salts include cerium salts and zirconium salts, and the rare earth salts include yttrium salts; The roasting temperature is 400℃~500℃; the roasting time is 2h~5h.

4. The preparation method according to claim 3, characterized in that, The cerium salt includes any one or a combination of at least two of cerium nitrate, cerium chloride, cerium sulfate, cerium ammonium nitrate, or cerium ammonium sulfate; And / or, the zirconium salt includes any one or a combination of at least two of zirconium nitrate, zirconium oxynitrate, zirconium oxychloride, or zirconium sulfate; And / or, the yttrium salt includes any one or a combination of at least two of yttrium nitrate, yttrium chloride, yttrium sulfate, or yttrium acetate; And / or, the solvent includes water.

5. The preparation method according to claim 3, characterized in that, The concentration of the precursor solution is 0.1 mol / L to 0.5 mol / L; And / or, the drying temperature is 60℃~80℃.

6. The preparation method according to claim 3, characterized in that, The heating rate of the calcination is 5℃ / min to 10℃ / min; And / or, the impregnation method includes equal-volume impregnation.

7. A method for preparing pentafluoropropylene from hexafluoropropane, characterized in that, The method includes: The catalyst for preparing pentafluoropropylene from hexafluoropropane as described in claim 1 or 2 is placed in a reaction apparatus, and then a mixture of hexafluoropropane and nitrogen is introduced into the reaction apparatus. Preheating, first stage reaction, second stage reaction and third stage reaction are carried out in sequence to prepare pentafluoropropylene. The temperature of the first reaction stage is less than the temperature of the third reaction stage, which in turn is less than the temperature of the second reaction stage.

8. The method as described in claim 7, characterized in that, The volume ratio of hexafluoropropane to nitrogen is 1:(3~5).

9. The method as described in claim 7, characterized in that, The space velocity of the mixed gas is 60 h⁻¹. -1 ~180h -1 ; And / or, the pressure in the reaction device is 0.5 MPa to 1.5 MPa.

10. The method as described in claim 7, characterized in that, The preheating temperature is 150℃~200℃, and the dwell time is 10s~30s; And / or, the temperature of the first reaction stage is 350℃~400℃, and the residence time is 20s~60s; And / or, the temperature of the second stage reaction is 400℃~450℃, and the residence time is 20s~60s; And / or, the temperature of the third stage reaction is 380℃~420℃, and the residence time is 20s~60s; And / or, the heating rate of the preheating, the first stage reaction, the second stage reaction and the third stage reaction is 5℃ / min~10℃ / min.

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