Perovskite dehydrogenation catalyst, preparation method thereof and method for producing low-carbon olefin

Abstract

The invention relates to a perovskite dehydrogenation catalyst, a preparation method thereof and a method for producing low-carbon olefin. The dehydrogenation catalyst comprises a cerium oxide modified lanthanum-nickel-iron perovskite catalyst and a molecular sieve catalyst, on the basis of the cerium oxide modified lanthanum-nickel-iron perovskite catalyst, the content of cerium oxide in the cerium oxide modified lanthanum-nickel-iron perovskite catalyst is 1 to 15 weight percent; the content of the lanthanum nickel iron perovskite is 85 to 99 weight percent. The invention also relates to a preparation method of the dehydrogenation catalyst. The method comprises the step of stirring and mixing the cerium oxide modified lanthanum-nickel-iron perovskite catalyst and the molecular sieve catalyst. The invention also relates to a method for producing low-carbon olefins. The method comprises the step of contacting a light hydrocarbon raw material with the dehydrogenation catalyst under an oxidative dehydrogenation condition. When the dehydrogenation catalyst is used for producing the low-carbon olefin, the chemical looping circulation reaction can be realized, the energy consumption required by the reaction is reduced, and the conversion rate of alkane and the selectivity of the low-carbon olefin are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, and in particular to a perovskite dehydrogenation catalyst and a preparation method thereof, and a method for producing light olefins. Background Art

[0002] Low-carbon olefins such as ethylene and propylene are the basic raw materials of the modern petrochemical industry. In recent years, the demand for low-carbon olefins in the petrochemical industry has been growing, and the traditional process of obtaining low-carbon olefins through naphtha cracking and catalytic cracking can no longer meet market demand. Therefore, how to convert low-carbon alkanes with low utilization rates into low-carbon olefins is a difficult problem that refining companies urgently need to solve.

[0003] At present, the technology of catalytic dehydrogenation of low-carbon alkanes to produce olefins has attracted much attention. The existing industrial alkane dehydrogenation technologies are all oxygen-free dehydrogenation processes using platinum and chromium catalysts. Chromium catalysts are expensive and harmful to the human body and the environment. From the perspective of process operation, the oxygen-free dehydrogenation process is limited by thermodynamic equilibrium and requires a high temperature and low pressure environment to achieve a good alkane conversion rate and olefin yield. The operation energy consumption is high and the catalyst needs to be regenerated frequently. Compared with oxygen-free dehydrogenation, the oxidative dehydrogenation reaction is an exothermic reaction that is not limited by thermodynamic equilibrium. It is easy to proceed in the positive reaction direction and can be carried out under low temperature conditions, which reduces energy consumption and side reactions. There is less carbon deposition on the catalyst, so that the catalyst can maintain a high activity for a long time. Therefore, oxidative dehydrogenation is an ideal process for the dehydrogenation of low-carbon alkanes to produce olefins.

[0004] In the traditional oxidative dehydrogenation process, the presence of oxygen is an important reason for the low selectivity of olefins. Therefore, realizing the oxidative dehydrogenation of alkanes without the presence of gaseous oxygen is expected to become a new solution. Perovskite materials can act as catalysts for oxidative dehydrogenation reactions through the oxidation and reduction of metal ions and the interaction between oxygen ions and gaseous oxygen in the crystal, which can well overcome a series of problems existing in the existing oxidative dehydrogenation process and provide more possibilities for the industrial application of alkane oxidative dehydrogenation.

[0005] However, when current catalysts are used for oxidative dehydrogenation to produce light olefins, there are still problems of low conversion rate and low selectivity, and the yields of ethylene and propylene still need to be further improved. Summary of the invention

[0006] The purpose of the present invention is to provide a perovskite dehydrogenation catalyst and a preparation method thereof and a method for producing light olefins, so as to further improve the yield of ethylene and propylene by oxidative dehydrogenation of light hydrocarbons.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a perovskite dehydrogenation catalyst, which dehydrogenation catalyst includes a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst; based on the cerium oxide-modified lanthanum nickel iron perovskite catalyst, the content of cerium oxide in the cerium oxide-modified lanthanum nickel iron perovskite catalyst is 1~15% by weight; the content of the lanthanum nickel iron perovskite is 85~99% by weight.

[0008] Optionally, based on the cerium oxide-modified lanthanum nickel iron perovskite catalyst, the content of the cerium oxide in the cerium oxide-modified lanthanum nickel iron perovskite catalyst is preferably 5-10% by weight; the content of the lanthanum nickel iron perovskite is preferably 90-95% by weight.

[0009] Optionally, the weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2~15):1, preferably (2~6):1; the molar ratio of lanthanum nickel iron in the cerium oxide modified lanthanum nickel iron perovskite catalyst is (0.1~10):(0.5~10):1, preferably (0.3~6):(0.8~5):1.

[0010] Optionally, the particle size of the cerium oxide modified lanthanum nickel iron perovskite catalyst is 3-15 nm; the specific surface area is 40-120 m 2 / g, preferably 60~100m 2 / g; the specific surface area of ​​the molecular sieve catalyst is 60~300m 2 / g, a silicon-aluminum ratio of 20-100, and a pore size of 0.2-13nm; the molecular sieve component in the molecular sieve catalyst includes at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-22 molecular sieve and Y molecular sieve.

[0011] The second aspect of the present invention provides a method for preparing the dehydrogenation catalyst provided by the first aspect of the present invention, the method comprising: stirring and mixing a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst.

[0012] Optionally, the weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2-15):1, preferably (2-6):1.

[0013] Optionally, the cerium oxide modified lanthanum nickel iron perovskite catalyst is prepared by a method comprising the following steps: S1, uniformly mixing a lanthanum source, a nickel source, an iron source, a complexing agent and water, and heating and refluxing to obtain a precursor, and performing a first drying and a first calcination on the precursor to obtain a lanthanum nickel iron perovskite; S2, impregnating the lanthanum nickel iron perovskite with an aqueous solution containing a cerium source, and then performing a second drying and a second calcination; The molar ratio of the complexing agent to the metal ion is (0.5-4):1; the mass ratio of the cerium source to the lanthanum nickel iron perovskite is 1:(30-200).

[0014] Optionally, the lanthanum source is one or more of lanthanum nitrate hexahydrate, lanthanum oxide and lanthanum aluminate; the nickel source is one or more of nickel nitrate hexahydrate, nickel acetate, nickel acetate and nickel chloride; the iron source is one or more of ferric nitrate hexahydrate, ferrous sulfate, ferric chloride and ferric oxide; the complexing agent is one or more of citric acid, sodium gluconate, diethanolamine and polyacrylic acid; the heating temperature is 60-90°C and the reflux time is 0.5-5h; the temperature of the first drying is 60-100°C and the time is 6-10h; the temperature of the first calcination is 600-800°C and the time is 1-5h; the temperature of the second drying is 60-100°C and the time is 8-12h; the temperature of the second calcination is 500-800°C and the time is 6-10h.

[0015] The third aspect of the present invention provides a method for producing light olefins, which comprises: contacting a light hydrocarbon feedstock with the dehydrogenation catalyst provided by the first aspect of the present invention under oxidative dehydrogenation conditions.

[0016] Optionally, the final distillation point of the light hydrocarbon feedstock is any value between 20-350°C; the total content of saturated paraffins and cycloalkanes in the light hydrocarbon feedstock is 30~100wt%; the conditions for the oxidative dehydrogenation include: the reaction temperature is 500~750°C, preferably 550~700°C; the weight space velocity is 50~120 (g / hour) / g catalyst, preferably 70~90 (g / hour) / g catalyst.

[0017] Through the above technical scheme, the present invention adopts a method of combining a cerium oxide-modified lanthanum nickel iron perovskite catalyst with a molecular sieve catalyst having catalytic cracking activity to achieve simultaneous oxidative dehydrogenation reaction and catalytic cracking reaction, thereby obtaining a higher alkane conversion rate and olefin selectivity, and improving the yield of ethylene and propylene.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 The LaNi modified by cerium oxide of the present invention 0.8 Fe 0.2 X-ray diffraction pattern of O3 perovskite; Figure 2 The LaNi modified by cerium oxide of the present invention 0.8 Fe 0.2 Scanning tunneling electron microscopy image of O3 perovskite. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0021] A first aspect of the present invention provides a perovskite dehydrogenation catalyst, which includes a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst; based on the cerium oxide-modified lanthanum nickel iron perovskite catalyst, the content of cerium oxide in the cerium oxide-modified lanthanum nickel iron perovskite catalyst is 1 to 15 weight percent; the content of the lanthanum nickel iron perovskite is 85 to 99 weight percent.

[0022] The dehydrogenation catalyst in the present invention is a composite catalyst composed of a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst. Cerium oxide is introduced into the lanthanum nickel iron perovskite, and cerium oxide defect engineering is used to provide more oxygen vacancies and improve the catalytic activity of the catalyst.

[0023] According to the present invention, optionally, based on the cerium oxide modified lanthanum nickel iron perovskite catalyst, the content of cerium oxide in the cerium oxide modified lanthanum nickel iron perovskite catalyst is preferably 5-10% by weight; the content of lanthanum nickel iron perovskite is preferably 90-95% by weight. The above embodiment can make the lanthanum nickel iron perovskite evenly dispersed on the cerium oxide, and exert better catalytic performance.

[0024] According to the present invention, optionally, the weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst can be (2-15): 1, preferably (2-6): 1; the molar ratio of lanthanum nickel iron in the cerium oxide modified lanthanum nickel iron perovskite catalyst can be (0.1-10): (0.5-10): 1, preferably (0.3-6): (0.8-5): 1. In the above embodiment, the cerium oxide modified lanthanum nickel iron perovskite catalyst can be better combined with the molecular sieve catalyst, and the catalytic activity of the obtained composite dehydrogenation catalyst is significantly improved.

[0025] According to the present invention, optionally, the particle size of the cerium oxide modified lanthanum nickel iron perovskite catalyst can be 3-15 nm; the specific surface area is 40-120 m 2 / g, preferably 60~100m 2 / g; the specific surface area of ​​the molecular sieve catalyst can be 60~300m 2 / g, the silicon-aluminum ratio can be 20-100, and the pore size can be 0.2-13nm; the molecular sieve component in the molecular sieve catalyst includes at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-22 molecular sieve and Y molecular sieve.

[0026] The second aspect of the present invention provides a method for preparing the dehydrogenation catalyst provided by the first aspect of the present invention, the method comprising: stirring and mixing a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst.

[0027] According to the present invention, optionally, the weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst can be (2-15):1, preferably (2-6):1.

[0028] According to the present invention, optionally, the cerium oxide modified lanthanum nickel iron perovskite catalyst is prepared by a method comprising the following steps: S1, uniformly mixing a lanthanum source, a nickel source, an iron source, a complexing agent and water, and heating and refluxing to obtain a precursor, and performing a first drying and a first calcination on the precursor to obtain a lanthanum nickel iron perovskite; S2, impregnating the lanthanum nickel iron perovskite with an aqueous solution containing a cerium source, and then performing a second drying and a second calcination; The molar ratio of the complexing agent to the metal ion is (0.5-4):1; the mass ratio of the cerium source to the lanthanum nickel iron perovskite is 1:(30-200).

[0029] According to the present invention, optionally, the lanthanum source can be one or more of lanthanum nitrate hexahydrate, lanthanum oxide and lanthanum aluminate; the nickel source can be one or more of nickel nitrate hexahydrate, nickel acetate, nickel acetate and nickel chloride; the iron source can be one or more of ferric nitrate hexahydrate, ferrous sulfate, ferric chloride and ferric oxide; the complexing agent can be one or more of citric acid, sodium gluconate, diethanolamine and polyacrylic acid.

[0030] According to the present invention, optionally, the heating temperature can be 60-90°C, and the reflux time can be 0.5-5h; the temperature of the first drying can be 60-100°C, and the time can be 6-10h; the temperature of the first calcination can be 600-800°C, and the time can be 1-5h; the temperature of the second drying can be 60-100°C, and the time can be 8-12h; the temperature of the second calcination can be 500-800°C, and the time can be 6-10h.

[0031] The third aspect of the present invention provides a method for producing light olefins, which comprises: contacting a light hydrocarbon feedstock with the dehydrogenation catalyst provided by the first aspect of the present invention under oxidative dehydrogenation conditions.

[0032] When the dehydrogenation catalyst is used in the present invention to carry out the oxidative dehydrogenation of light hydrocarbons to produce ethylene and propylene, a chemical chain cycle reaction can be achieved, the energy consumption required for the reaction is reduced, and the conversion rate of alkanes and the selectivity of low-carbon olefins are improved.

[0033] According to the present invention, optionally, the final distillation point of the light hydrocarbon feedstock can be any value between 20-350°C; the total content of saturated paraffins and cycloalkanes in the light hydrocarbon feedstock can be 30~100wt%; the conditions for the oxidative dehydrogenation include: the reaction temperature can be 500~750°C, preferably 550~700°C; the weight space velocity is 50~120 (g / hour) / g catalyst, preferably 70~90 (g / hour) / g catalyst.

[0034] According to the present invention, optionally, a fixed bed reaction system can be used when the light hydrocarbon feedstock contacts the dehydrogenation catalyst, and the oxidative dehydrogenation reaction and the oxidative regeneration reaction are respectively carried out simultaneously in two parallel fixed bed reactors, which are switched back and forth for continuous operation.

[0035] In the present invention, a fixed bed reaction system can be used. In the process of oxidative dehydrogenation reaction, lanthanum nickel iron perovskite modified by cerium oxide serves as a dehydrogenation active center, on which a reaction of dehydrogenating alkanes to generate olefins and hydrogen occurs, and a catalytic cracking reaction occurs on a molecular sieve catalyst with catalytic cracking activity. The lattice oxygen carried by the lanthanum nickel iron perovskite modified by cerium oxide can selectively react with the hydrogen generated by the dehydrogenation reaction to oxidize it into water vapor, accompanied by the reduction of the lattice oxygen. After the reaction is completed, the lanthanum nickel iron perovskite modified by cerium oxide that has lost its lattice oxygen is oxidized and regenerated in air at 150-220°C, and the lattice oxygen is replenished while removing carbon deposits to restore the reaction activity, thereby completing a redox reaction regeneration cycle.

[0036] According to the present invention, optionally, a circulating fluidized bed reaction system can be used when the light hydrocarbon feedstock contacts the dehydrogenation catalyst, the catalyst is fluidized and circulated in the reactor and the oxidation regenerator, and the heat released by the oxidation and dehydrogenation of the catalyst is supplied to the reactor, thereby reducing the external heating of the reactor.

[0037] According to the present invention, optionally, a moving bed reaction system can be used when the light hydrocarbon feedstock is contacted with the dehydrogenation catalyst, the alkane is introduced from the top inlet of the reactor, and the dehydrogenation catalyst is continuously added from the top of the reactor. As the reaction proceeds, the dehydrogenation catalyst gradually moves downward by gravity, and is finally continuously unloaded from the bottom and lifted to the regenerator by gas for oxidation regeneration. The oxidation regeneration reaction temperature is 600-750°C, preferably 680~700°C, the reaction pressure is normal pressure, and the air flow rate is 35-120mL / min.

[0038] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0039] The present invention describes the preparation of a dehydrogenation catalyst and evaluates the catalytic performance of the catalyst. The dehydrogenation catalyst prepared in the embodiment is evaluated using a fixed bed reactor. A certain amount of catalyst is loaded into a fixed bed reactor, and n-octane is injected by an injection pump to perform a catalytic cracking reaction. The gas product is analyzed online using a gas chromatograph to obtain a detailed composition of the cracked gas.

[0040] The raw material n-octane (mass fraction greater than 99.0%) in the examples was analytically pure and was a product of Acros Organics Reagent Company.

[0041] Example 1 In this example, LaNi was synthesized according to the following steps 0.8 Fe 0.2 O3 Perovskite: La(NO3)3·6H2O, Ni(NO3)2·6H2O and Fe(NO3)3·9H2O were dissolved in deionized water according to the molar ratio of La, Ni and Fe of 5:4:1. Citric acid was weighed and prepared into a solution according to the molar ratio of citric acid to the total amount of metal ions of 3:1. The two were mixed evenly and the solution was adjusted to pH=6 with ammonia water. The mixed solution quickly became turbid and the formation of a precipitate was immediately observed. Then, the mixed solution was transferred to a round-bottom flask, and the solution temperature was raised to 60°C on an electric furnace and heated under stirring and reflux for 4h. The sample collected by centrifugation was washed several times with water and ethanol to obtain a precursor. Finally, the precursor was dried at 80°C for 8h, then placed in a box atmosphere furnace and calcined at 650°C for 2h to finally obtain black LaNi 0.8 Fe 0.2 O3 perovskite sample.

[0042] Weigh Ce(NO3)3·6H2O and LaNi in a mass ratio of 1:50 0.8 Fe 0.2 O3 perovskite, LaNi impregnated with Ce(NO3)3·6H2O aqueous solution 0.8 Fe 0.2 O3 perovskite, stirred for 1 h, then dried at 80 °C for 12 h, and calcined at 600 °C for 8 h to obtain LaNi modified with cerium oxide 0.8 Fe 0.2 O3 perovskite catalyst (CeO2-LaNi 0.8 Fe 0.2 O3), of which the cerium oxide content is 5%, LaNi 0.8 Fe 0.2 The O3 perovskite content is 95%. LaNi modified by cerium oxide 0.8 Fe 0.2 The specific surface area of ​​the O3 perovskite catalyst is 80 m 2 / g. Cerium oxide modified LaNi 0.8 Fe 0.2 The X-ray diffraction pattern and scanning tunneling electron microscopy image of O3 perovskite are shown in Figure 1 and Figure 2 shown.

[0043] Ceria-modified LaNi 0.8 Fe 0.2 O3 perovskite catalyst and ZSM-5 molecular sieve catalyst (specific surface area 83m 2 / g, silicon-aluminum ratio of 60, pore size of 0.6nm) were stirred and mixed in a mass ratio of 5:2 to prepare a composite dehydrogenation catalyst (CeO2-LaNi 0.8 Fe 0.2 O3 / ZSM-5).

[0044] With n-octane as the raw material, at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 23.19% and 33.83%. At a reaction temperature of 700°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 34.43% and 31.53%.

[0045] Example 2 The preparation method of this embodiment is the same as that of embodiment 1, except that: the LaNi modified with cerium oxide in embodiment 1 is 0.8 Fe 0.2 The O3 perovskite catalyst and the ZSM-5 molecular sieve catalyst were ground and mixed in a mass ratio of 6:1 to prepare a composite dehydrogenation catalyst.

[0046] With n-octane as raw material, at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 16.90% and 30.46%. At a reaction temperature of 700°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 29.95% and 27.63%.

[0047] Example 3 The preparation method of this embodiment is the same as that of embodiment 1, except that: the solution is adjusted to pH=10 with aqueous ammonia; Weigh Ce(NO3)3·6H2O and LaNi in a mass ratio of 1:100. 0.8 Fe 0.2 O3 perovskite, LaNi impregnated with Ce(NO3)3·6H2O aqueous solution 0.8 Fe 0.2O3 perovskite, stirred for 1 h, dried at 80 °C for 12 h, and calcined at 600 °C for 8 h to obtain LaNi modified with cerium oxide 0.8 Fe 0.2 O3 perovskite catalyst, in which the cerium oxide content is 10%, LaNi 0.8 Fe 0.2 The content of O3 perovskite is 90%. LaNi modified by cerium oxide 0.8 Fe 0.2 The specific surface area of ​​the O3 perovskite catalyst is 80 m 2 / g.

[0048] With n-octane as the raw material, at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 21.56% and 30.85%. At a reaction temperature of 700°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 31.49% and 30.73%.

[0049] Example 4 The preparation method of this embodiment is the same as that of embodiment 3, except that: the LaNi modified with cerium oxide in embodiment 3 is 0.8 Fe 0.2 The O3 perovskite and the ZSM-5 molecular sieve catalyst were ground and mixed in a mass ratio of 6:1 to prepare a composite dehydrogenation catalyst.

[0050] With n-octane as the raw material, at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 19.59% and 27.86%. At a reaction temperature of 700°C, a pressure of 1 MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass were 29.02% and 30.15%.

[0051] Comparative Example 1 The cerium oxide modified LaNi prepared in Example 1 is used alone 0.8 Fe 0.2 O3 perovskite catalyst is used as dehydrogenation catalyst, with n-octane as raw material, under the conditions of reaction temperature of 650℃, pressure of 1MPa, and weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass are 10.06% and 5.37%. Under the conditions of reaction temperature of 700℃, pressure of 1MPa, and weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in one pass are 13.65% and 5.97%.

[0052] Comparative Example 2 Using a molecular sieve catalyst with a ZSM-5 molecular sieve content of 30% and n-octane as a raw material, the yields of ethylene and propylene in a single pass are 8.83% and 4.76% at a reaction temperature of 650°C, a pressure of 1MPa, and a weight space velocity of 70 (g / h) / g catalyst. Under the conditions of a reaction temperature of 700°C, a pressure of 1MPa, and a weight space velocity of 70 (g / h) / g catalyst, the yields of ethylene and propylene in a single pass are 10.46% and 4.95%.

[0053] Comparative Example 3 The cerium oxide modified LaNi prepared in Example 3 is used alone 0.8 Fe 0.2 O3 perovskite catalyst is used as dehydrogenation catalyst, with n-octane as raw material, under the conditions of reaction temperature of 650℃, pressure of 1MPa, and weight space velocity of 70 (g / h) / g catalyst, the yield of ethylene and propylene in one pass is 6.82% and 3.51%. Under the conditions of reaction temperature of 700℃, pressure of 1MPa, and weight space velocity of 70 (g / h) / g catalyst, the yield of ethylene and propylene in one pass is 19.05% and 8.86%.

[0054] Table 1 Comparison of ethylene and propylene yields of dehydrogenation catalysts in the examples Table 2 Comparison of ethylene and propylene yields of dehydrogenation catalysts in comparative examples The above examples and comparative examples show that the composite dehydrogenation catalyst synthesized by the present invention has good catalytic activity when used for oxidative dehydrogenation to produce light olefins, thereby obtaining a higher alkane conversion rate and olefin selectivity, and can increase the yield of ethylene and propylene.

[0055] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0057] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A perovskite dehydrogenation catalyst, characterized in that: The dehydrogenation catalyst comprises a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst; based on the cerium oxide-modified lanthanum nickel iron perovskite catalyst, the content of cerium oxide in the cerium oxide-modified lanthanum nickel iron perovskite catalyst is 1-15% by weight; the content of lanthanum nickel iron perovskite is 85-99% by weight.

2. The dehydrogenation catalyst according to claim 1, wherein Based on the cerium oxide modified lanthanum nickel iron perovskite catalyst, the content of the cerium oxide in the cerium oxide modified lanthanum nickel iron perovskite catalyst is preferably 5 to 10% by weight; the content of the lanthanum nickel iron perovskite is preferably 90 to 95% by weight.

3. The dehydrogenation catalyst according to claim 1, wherein The weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2-15):1, preferably (2-6):1; The molar ratio of lanthanum, nickel and iron in the cerium oxide modified lanthanum, nickel and iron perovskite catalyst is (0.1-10): (0.5-10): 1, preferably (0.3-6): (0.8-5):

1.

4. The dehydrogenation catalyst according to claim 1, wherein The particle size of the cerium oxide modified lanthanum nickel iron perovskite catalyst is 3-15 nm; the specific surface area is 40-120 m 2 / g, preferably 60~100m 2 / g; The specific surface area of ​​the molecular sieve catalyst is 60-300 m 2 / g, a silicon-aluminum ratio of 20-100, and a pore size of 0.2-13nm; the molecular sieve component in the molecular sieve catalyst includes at least one of ZSM-5 molecular sieve, ZSM-11 molecular sieve, ZSM-22 molecular sieve and Y molecular sieve.

5. A method for preparing the dehydrogenation catalyst according to any one of claims 1 to 4, characterized in that: The method comprises: stirring and mixing a cerium oxide-modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst.

6. The method according to claim 5, wherein: The weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2-15):1, preferably (2-6):

1.

7. The method according to claim 5, wherein: The cerium oxide modified lanthanum nickel iron perovskite catalyst is prepared by a method comprising the following steps: S1, uniformly mixing a lanthanum source, a nickel source, an iron source, a complexing agent and water, and heating and refluxing to obtain a precursor, and performing a first drying and a first calcination on the precursor to obtain a lanthanum nickel iron perovskite; S2, impregnating the lanthanum nickel iron perovskite with an aqueous solution containing a cerium source, and then performing a second drying and a second calcination; The molar ratio of the complexing agent to the metal ion is (0.5-4):1; the mass ratio of the cerium source to the lanthanum nickel iron perovskite is 1:(30-200).

8. The method according to claim 7, wherein: The lanthanum source is one or more of lanthanum nitrate hexahydrate, lanthanum oxide and lanthanum aluminate; the nickel source is one or more of nickel nitrate hexahydrate, nickel acetate, nickel acetate and nickel chloride; the iron source is one or more of ferric nitrate hexahydrate, ferrous sulfate, ferric chloride and ferric oxide; the complexing agent is one or more of citric acid, sodium gluconate, diethanolamine and polyacrylic acid; The heating temperature is 60-90°C and the reflux time is 0.5-5h; The first drying temperature is 60-100°C and the time is 6-10h; The first calcination temperature is 600-800°C and the time is 1-5h; The second drying temperature is 60-100°C and the time is 8-12h; The second calcination temperature is 500-800° C. and the time is 6-10 hours.

9. A method for producing light olefins, characterized in that: The method comprises: contacting a light hydrocarbon feedstock with the dehydrogenation catalyst described in any one of claims 1 to 4 under oxidative dehydrogenation conditions.

10. The method according to claim 8, wherein: The final boiling point of the light hydrocarbon feedstock is any value between 20-350°C; the total content of saturated paraffins and cycloparaffins in the light hydrocarbon feedstock is 30-100wt%; The conditions for the oxidative dehydrogenation include: a reaction temperature of 500-750° C., preferably 550-700° C.; a weight space velocity of 50-120 (g / h) / g catalyst, preferably 70-90 (g / h) / g catalyst.

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