A perovskite dehydrogenation catalyst and its preparation method and method for producing light olefins

Abstract

The present application relates to a perovskite dehydrogenation catalyst, a preparation method thereof and a method for producing low carbon olefins, the dehydrogenation catalyst comprising a cerium oxide modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst; the content of the cerium oxide in the cerium oxide modified lanthanum nickel iron perovskite catalyst is 1-15% by weight, based on the cerium oxide modified lanthanum nickel iron perovskite catalyst; and the content of the lanthanum nickel iron perovskite is 85-99% by weight. The present application also relates to a preparation method of the above dehydrogenation catalyst, the method comprising stirring and mixing the cerium oxide modified lanthanum nickel iron perovskite catalyst and the molecular sieve catalyst. The present application also relates to a method for producing low carbon olefins, the method comprising contacting a light hydrocarbon raw material with the above dehydrogenation catalyst under oxidative dehydrogenation conditions. When the dehydrogenation catalyst is used to produce low carbon olefins, the present application can realize a chemical chain cyclic reaction, reduce the energy consumption required for the reaction, and improve the conversion rate of alkanes and the selectivity of low carbon olefins.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum chemical industry, in particular to a perovskite dehydrogenation catalyst, a preparation method thereof and a method for producing low-carbon olefins. BACKGROUND

[0002] Low-carbon olefins such as ethylene and propylene are basic raw materials for modern petrochemical industry. In recent years, the demand for low-carbon olefins in the petrochemical industry is increasing, and the traditional naphtha cracking and catalytic cracking process for obtaining low-carbon olefins cannot meet the market demand. Therefore, how to convert low-carbon alkanes with low utilization rate into low-carbon olefins is a difficult problem that needs to be solved by refining enterprises.

[0003] At present, the catalytic dehydrogenation of low-carbon alkanes to olefins is attracting much attention. The existing industrialized alkanes dehydrogenation technology is an oxygen-free dehydrogenation process using platinum and chromium catalysts. The chromium catalyst has high cost and is harmful to the human body and the environment. From the process operation, the oxygen-free dehydrogenation process is limited by thermodynamic equilibrium and needs to be operated at high temperature and low pressure to achieve good alkanes conversion rate and olefin yield. The operation energy consumption is high, and the catalyst needs to be regenerated frequently. Compared with oxygen-free dehydrogenation, oxidative dehydrogenation is an exothermic reaction not limited by thermodynamic equilibrium, which is easy to proceed in the forward direction and can be carried out at a lower temperature, thereby reducing energy consumption and the occurrence of side reactions, and the catalyst has less carbon deposition, so that the catalyst can maintain high activity for a longer period of time. Therefore, oxidative dehydrogenation is an ideal process for the dehydrogenation of low-carbon alkanes to olefins.

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

[0005] However, the existing catalysts for the oxidative dehydrogenation to produce low-carbon olefins still have the problems of low conversion rate and low selectivity, and the yield of ethylene and propylene still needs to be further improved. SUMMARY

[0006] The purpose of the present application is to provide a perovskite dehydrogenation catalyst, a preparation method thereof and a method for producing low-carbon olefins, so as to further improve the yield of ethylene and propylene produced by the 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 weight%; the content of the lanthanum nickel iron perovskite is 85~99 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 to 10 weight %; the content of the lanthanum nickel iron perovskite is preferably 90 to 95 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 to 15 nm; the specific surface area is 40 to 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 0.2-13 nm; 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:

[0014] S1, uniformly mixing a lanthanum source, a nickel source, an iron source, a complexing agent, and water, and then 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;

[0015] 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;

[0016] 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).

[0017] 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.

[0018] 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.

[0019] 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: a reaction temperature of 500~750°C, preferably 550~700°C; a weight space velocity of 50~120 (g / hour) / g catalyst, preferably 70~90 (g / hour) / g catalyst.

[0020] Through the above technical scheme, the present invention adopts the 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.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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 detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1The LaNi modified by cerium oxide of the present invention 0.8 Fe 0.2 X-ray diffraction pattern of O3 perovskite;

[0024] 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

[0025] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] 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.

[0027] 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.

[0028] According to the present invention, optionally, based on the cerium oxide-modified lanthanum nickel iron perovskite catalyst, the cerium oxide content in the cerium oxide-modified lanthanum nickel iron perovskite catalyst is preferably 5 to 10% by weight; and the lanthanum nickel iron perovskite content is preferably 90 to 95% by weight. This embodiment allows the lanthanum nickel iron perovskite to be evenly dispersed on the cerium oxide, thereby achieving better catalytic performance.

[0029] 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 and the molecular sieve catalyst can be better combined, and the catalytic activity of the resulting composite dehydrogenation catalyst is significantly improved.

[0030] 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 0.2-13 nm; 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.

[0031] 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.

[0032] 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.

[0033] According to the present invention, optionally, the cerium oxide modified lanthanum nickel iron perovskite catalyst is prepared by a method comprising the following steps:

[0034] S1, uniformly mixing a lanthanum source, a nickel source, an iron source, a complexing agent, and water, and then 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;

[0035] 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;

[0036] 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).

[0037] 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.

[0038] According to the present invention, optionally, the heating temperature can be 60-90°C, and the reflux time can be 0.5-5h; the first drying temperature can be 60-100°C, and the time can be 6-10h; the first calcination temperature can be 600-800°C, and the time can be 1-5h; the second drying temperature can be 60-100°C, and the time can be 8-12h; the second calcination temperature can be 500-800°C, and the time can be 6-10h.

[0039] 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.

[0040] 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 light olefins are improved.

[0041] According to the present invention, optionally, the final boiling 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 / h) / g catalyst, preferably 70~90 (g / h) / g catalyst.

[0042] 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 and simultaneously carried out in two parallel fixed bed reactors, which are switched back and forth for continuous operation.

[0043] In the present invention, a fixed bed reaction system can be used. During the oxidative dehydrogenation reaction, the lanthanum nickel iron perovskite modified by cerium oxide serves as the dehydrogenation active center, on which the reaction of dehydrogenating alkanes to generate olefins and hydrogen occurs. The 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 and restoring the reaction activity, thus completing a redox reaction regeneration cycle.

[0044] 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 catalyst oxidation and dehydrogenation is supplied to the reactor, reducing the external heating of the reactor.

[0045] 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 by gas to the regenerator for oxidative regeneration. The oxidative regeneration reaction temperature is 600-750°C, preferably 680-700°C, the reaction pressure is atmospheric pressure, and the air flow rate is 35-120 mL / min.

[0046] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0047] The present examples describe the preparation of a dehydrogenation catalyst and evaluate its catalytic performance. The dehydrogenation catalyst prepared in these examples was evaluated using a fixed-bed reactor. A predetermined amount of catalyst was loaded into the fixed-bed reactor, and n-octane was injected via a syringe pump to initiate a catalytic cracking reaction. The gas products were analyzed online using a gas chromatograph to obtain a detailed composition of the cracked gas.

[0048] The raw material n-octane (mass fraction greater than 99.0%) in the examples was analytical grade and was a product of Acros Organics Reagent Company.

[0049] Example 1

[0050] In this example, LaNi was synthesized according to the following steps 0.8 Fe 0.2 O3 perovskite:

[0051] 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 stirred and heated under reflux for 4 hours. 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 8 hours, then placed in a box atmosphere furnace and calcined at 650°C for 2 hours to finally obtain black LaNi. 0.8 Fe 0.2 O3 perovskite sample.

[0052] Weigh Ce(NO3)3·6H2O and LaNi in a mass ratio of 1:50 0.8 Fe 0.2 O3 perovskite, using Ce(NO3)3·6H2O aqueous solution to impregnate LaNi0.8 Fe 0.2 O3 perovskite, stirred for 1 hour, then dried at 80 ° C for 12 hours, and calcined at 600 ° C for 8 hours to obtain cerium oxide modified LaNi 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 pattern of O3 perovskite are shown in Figure 2. Figure 1 and Figure 2 shown.

[0053] 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).

[0054] Using 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 single-pass yields of ethylene and propylene 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 single-pass yields of ethylene and propylene were 34.43% and 31.53%.

[0055] Example 2

[0056] 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.

[0057] Using 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 single-pass yields of ethylene and propylene 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 single-pass yields of ethylene and propylene were 29.95% and 27.63%.

[0058] Example 3

[0059] 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;

[0060] Weigh Ce(NO3)3·6H2O and LaNi in a mass ratio of 1:100. 0.8 Fe 0.2 O3 perovskite, using Ce(NO3)3·6H2O aqueous solution to impregnate LaNi 0.8 Fe 0.2 O3 perovskite, stirred for 1 hour, dried at 80℃ for 12 hours, and calcined at 600℃ for 8 hours to obtain cerium oxide-modified LaNi 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%. Cerium oxide modified LaNi 0.8 Fe 0.2 The specific surface area of ​​the O3 perovskite catalyst is 80 m 2 / g.

[0061] Using 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 single-pass yields of ethylene and propylene 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 single-pass yields of ethylene and propylene were 31.49% and 30.73%.

[0062] Example 4

[0063] 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.

[0064] Using 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 single-pass yields of ethylene and propylene 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 single-pass yields of ethylene and propylene were 29.02% and 30.15%.

[0065] Comparative Example 1

[0066] The LaNi modified by cerium oxide prepared in Example 1 was used alone 0.8 Fe 0.2 Using an O3 perovskite catalyst as a dehydrogenation catalyst with n-octane as the raw material, the yields of ethylene and propylene per pass were 10.06% and 5.37% at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 g / h / g catalyst. 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 per pass were 13.65% and 5.97%.

[0067] Comparative Example 2

[0068] Using a molecular sieve catalyst containing 30% ZSM-5 molecular sieve as a catalyst, 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 single-pass yields of ethylene and propylene were 8.83% and 4.76%. At a reaction temperature of 700°C, a pressure of 1 MPa, and a weight space velocity of 70 g / h / g catalyst, the single-pass yields of ethylene and propylene were 10.46% and 4.95%.

[0069] Comparative Example 3

[0070] The LaNi modified with cerium oxide prepared in Example 3 was used alone. 0.8 Fe 0.2 Using an O3 perovskite catalyst as a dehydrogenation catalyst with n-octane as the raw material, the yields of ethylene and propylene per pass were 6.82% and 3.51% at a reaction temperature of 650°C, a pressure of 1 MPa, and a weight space velocity of 70 g / h / g catalyst. 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 per pass were 19.05% and 8.86%.

[0071] Table 1 Comparison of ethylene and propylene yields of dehydrogenation catalysts in the examples

[0072]

[0073] Table 2 Comparison of ethylene and propylene yields of dehydrogenation catalysts in comparative examples

[0074]

[0075] 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 achieving higher alkane conversion and olefin selectivity, and improving the yields of ethylene and propylene.

[0076] 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, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0078] In addition, the 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 to 15% by weight; the content of the lanthanum nickel iron perovskite is 85 to 99% by weight; 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.

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 5 to 10 weight %; the content of the lanthanum nickel iron perovskite is 90 to 95 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; 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.

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

1.

5. 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; The specific surface area of ​​the molecular sieve catalyst is 60~300m 2 / g, the silicon-aluminum ratio is 20~100, and the pore size is 0.2~13nm. The dehydrogenation catalyst according to claim 5, wherein The specific surface area of ​​the cerium oxide modified lanthanum nickel iron perovskite catalyst is 60-100 m 2 / g.

7. A method for preparing the dehydrogenation catalyst according to any one of claims 1 to 6, characterized in that: The method comprises: stirring and mixing a cerium oxide modified lanthanum nickel iron perovskite catalyst and a molecular sieve catalyst.

8. The method according to claim 7, wherein: The weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2-15):

1.

9. The method according to claim 8, wherein The weight ratio of the cerium oxide modified lanthanum nickel iron perovskite catalyst to the molecular sieve catalyst is (2-6):

1.

10. The method according to claim 7, 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 then 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).

11. The method according to claim 10, 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 6-10 hours; 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.

12. A method for producing light olefins, characterized in that: The method comprises: contacting a light hydrocarbon feedstock with the dehydrogenation catalyst according to any one of claims 1 to 6 under oxidative dehydrogenation conditions.

13. The method according to claim 12, wherein: The final boiling point of the light hydrocarbon feedstock is any value between 20° C. and 350° C.; the total content of saturated paraffins and cycloalkanes in the light hydrocarbon feedstock is 30 to 100 wt %; The conditions for the oxidative dehydrogenation include: a reaction temperature of 500-750° C.; and a weight space velocity of 50-120 (g / h) / g of catalyst.

14. The method according to claim 13, wherein The conditions for the oxidative dehydrogenation include: a reaction temperature of 550-700° C.; and a weight space velocity of 70-90 (g / h) / g catalyst.

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