Iron-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, and discloses an iron-based catalyst as well as a preparation method and application thereof, the catalyst has a structure as shown in the following formula: FeAaMbQcOx, wherein A is Cu and / or Zr; m is selected from at least one of IIA group metal elements; q is selected from at least one of lanthanide elements; a, b and c are respectively molar ratios of A, M and Q to Fe, and a is equal to 0.1-0.6; b is equal to 0.1 to 0.4; c is equal to 0.05 to 0.2; x is the total number of oxygen atoms required by valence of each element in the active component. The iron-based catalyst has high CO conversion rate and low-carbon olefin selectivity through matching of specific active metal components and contents.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to an iron-based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The main components of syngas are CO and H 2 , and converting syngas into olefins can, on the one hand, solve the pollution generated during coal combustion, and on the other hand, improve energy utilization efficiency. There are direct and indirect methods for converting syngas into olefins. The indirect method generally adopts the route of syngas to methanol and then to light olefins, while the Fischer-Tropsch process is one of the efficient routes for directly synthesizing olefins from syngas in one step.

[0003] CN106311317A discloses a catalyst and a method for directly preparing light olefins from syngas in one step. The catalyst uses a composite material composed of a multi-component metal complex and a mesoporous inorganic solid acid. However, when this catalyst is used for synthesizing light olefins, there are problems such as low single-pass conversion rate of CO, wide reaction product distribution, and low selectivity for light olefins. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of low carbon monoxide conversion rate and low selectivity for light olefins in the reaction of converting syngas into light olefins existing in the prior art, and to provide an iron-based catalyst, a preparation method thereof, and an application thereof. The iron-based catalyst has high CO conversion rate and selectivity for light olefins through the cooperation of specific active metal components and contents.

[0005] To achieve the above purpose, the first aspect of the present invention provides an iron-based catalyst, wherein the catalyst has a structure shown by the following formula: FeA a M b Q c O x ;

[0006] wherein, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements;

[0007] a, b, and c are the molar ratios of A, M, and Q to Fe respectively, a = 0.1 - 0.6; b = 0.1 - 0.4; c = 0.05 - 0.2; x is the total number of oxygen atoms required to satisfy the valence of each element in the active component.

[0008] The second aspect of the present invention provides a preparation method of an iron-based catalyst, wherein the method includes:

[0009] (1) Prepare a mixed solution containing an Fe source, an A source, an M source, a Q source, and a structure regulator;

[0010] (2) Hydrothermally treat the mixed solution, dry and calcine the obtained solid product to obtain an iron-based catalyst;

[0011] Among them, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements.

[0012] The third aspect of the present invention provides an iron-based catalyst prepared by the preparation method described in the second aspect.

[0013] The fourth aspect of the present invention provides an application of the iron-based catalyst described in the first aspect or the third aspect in the conversion of syngas to light olefins.

[0014] Through the above technical solutions, the beneficial effects obtained are as follows:

[0015] The iron-based catalyst provided by the present invention, through the cooperation of the types and contents of specific active metals, and by adding a structure regulator during the preparation process, makes the catalyst particles not easily agglomerate during the preparation process, and improves the conversion rate and the selectivity of light olefins. Detailed implementation manners

[0016] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0017] The first aspect of the present invention provides an iron-based catalyst, and the catalyst has a structure shown by the following formula: FeA a M b Q c O x ;

[0018] Among them, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements;

[0019] a, b, and c are the molar ratios of A, M, and Q to Fe respectively, a = 0.1 - 0.6; b = 0.1 - 0.4; c = 0.05 - 0.2; x is the total number of oxygen atoms required to satisfy the valence of each element in the active component.

[0020] In the present invention, for the iron-based catalyst having the above composition, the cooperation between the components can improve the catalytic activity of the iron-based catalyst, and improve the conversion rate and the selectivity of light olefins.

[0021] It should be noted that in the present invention, "FeA a Mb Q c O x The general formula of "" only represents the respective elements and their molar contents of the active components in the catalyst, and does not represent that the active components of the catalyst in the present invention exist in the form of molecules of this general formula.

[0022] According to the present invention, preferably, a = 0.2 - 0.5.

[0023] According to the present invention, preferably, M is Mg and / or Sr.

[0024] According to the present invention, preferably, b = 0.1 - 0.35.

[0025] According to the present invention, preferably, Q is Nd and / or Sm.

[0026] According to the present invention, preferably, c = 0.05 - 0.15.

[0027] In the present invention, the iron-based catalyst has the above-mentioned preferred combination of elemental composition and content, has many active sites and high catalytic activity, is used for the syngas conversion reaction, and has higher CO conversion rate and higher light olefin selectivity.

[0028] In the present invention, the elemental composition and content of the iron-based catalyst are obtained by calculating the feeding ratio in the preparation process.

[0029] According to the present invention, preferably, the particle size of the catalyst is 200 - 900 nm, such as 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, or the range between any two of them, preferably 250 - 500 nm. In the present invention, the particle size of the catalyst is finer, which can provide more active sites. When the catalyst is used for the syngas conversion reaction, the conversion rate is higher and the light olefin selectivity is higher.

[0030] In the present invention, the particle size of the catalyst is measured by a ZETASIZER Nano-ZS type laser nanometer particle size analyzer of Malvern Instruments Limited.

[0031] The second aspect of the present invention provides a preparation method of an iron-based catalyst, wherein the method includes:

[0032] (1) Prepare a mixed solution containing an Fe source, an A source, an M source, a Q source and a structure regulator;

[0033] (2) Carry out hydrothermal treatment on the mixed solution, and dry and calcine the obtained solid product to obtain an iron-based catalyst;

[0034] Among them, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements.

[0035] In the present invention, a structure regulator is added for hydrothermal treatment to prepare the catalyst. During the preparation process, the catalyst particles are not easily agglomerated, the particles are finer, and the conversion rate of the catalyst in the syngas conversion reaction and the selectivity for light olefins can be improved.

[0036] According to the present invention, the type of the Fe source is not particularly limited, and a soluble iron salt can be used. Preferably, the Fe source is selected from at least one of iron nitrate, iron chloride, and iron sulfate.

[0037] According to the present invention, the types of the A source, the M source, and the Q source are not particularly limited, and soluble salts can be used. Preferably, the A source, the M source, and the Q source are each independently a nitrate and / or a chloride.

[0038] According to the present invention, preferably, M is Mg and / or Sr.

[0039] According to the present invention, preferably, Q is Nd and / or Sm.

[0040] According to the present invention, preferably, in the mixed solution, the molar amount of the Fe source is based on Fe, the molar amount of the A source is based on A, and the molar ratio of the Fe source to the A source is 1:0.1 - 0.6, such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, or the range between any two of them, and preferably 1:0.2 - 0.5.

[0041] According to the present invention, preferably, the molar amount of the Fe source is based on Fe, the molar amount of the M source is based on M, and the molar ratio of the Fe source to the M source is 1:0.1 - 0.4, such as 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, or the range between any two of them, and preferably 1:0.1 - 0.35.

[0042] According to the present invention, preferably, the molar amount of the Fe source is based on Fe, the molar amount of the Q source is based on Q, and the molar ratio of the Fe source to the Q source is 1:0.05 - 0.2, such as 1:0.05, 1:0.1, 1:0.15, 1:0.2, or the range between any two of them, and preferably 1:0.05 - 0.15.

[0043] In the present invention, preferably, the catalyst further contains an O element.

[0044] According to the present invention, preferably, the content of the O element is the total number of oxygen atoms required to satisfy the valence of each element in the active component.

[0045] According to the present invention, the structural regulator is an auxiliary agent capable of improving the dispersibility of catalyst particles. Preferably, the structural regulator is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and / or ammonium polyacrylate. In the present invention, using the above structural regulator to prepare the catalyst can improve the dispersion of catalyst particles during the preparation process, the obtained catalyst particles have a finer particle size, better conversion rate during the syngas conversion reaction, and better selectivity for light olefins.

[0046] According to the present invention, preferably, the structural regulator is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and ammonium polyacrylate.

[0047] According to the present invention, preferably, the mass ratio of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer to ammonium polyacrylate is 0.5 - 5:1, such as 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or the range between any two of them, preferably 1 - 4:1. In the present invention, using the structural regulator with the above mass ratio to prepare the catalyst can adsorb on the particle surface, effectively inhibit the aggregation of particles, and obtain good dispersibility.

[0048] In the present invention, preferably, the weight-average molecular weight of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer is 5000 - 7000; the weight-average molecular weight of the ammonium polyacrylate is 4000 - 6000.

[0049] According to the present invention, preferably, the addition amount of the structural regulator is 30 - 60 wt% of the total weight of the prepared catalyst, preferably 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or the range between any two of them, preferably 35 - 55 wt%.

[0050] According to a preferred embodiment of the present invention, the preparation process of the mixed solution in step (1) includes: preparing a mixed solution I containing Fe source, A source, M source, and Q source, and then preparing an aqueous solution of the structural regulator and mixing it with the mixed solution I to obtain a mixed solution II.

[0051] According to the present invention, preferably, the conditions of the hydrothermal treatment include: the reaction temperature is 120 - 260 °C, such as 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, or the range between any two of them, preferably 140 - 240 °C; the reaction time is 12 - 60 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, 48 hours, 54 hours, 56 hours, 60 hours, or the range between any two of them, preferably 18 - 54 hours. In the present invention, under the above conditions, the hydrothermal treatment can make the particle size distribution more uniform.

[0052] In the present invention, there is no particular limitation on the equipment for carrying out the hydrothermal treatment, and those skilled in the art can make an adaptive selection. Preferably, the hydrothermal treatment is carried out in a reaction kettle.

[0053] In the present invention, after the hydrothermal treatment, the reaction kettle is cooled to room temperature, which is convenient for the subsequent steps and at the same time avoids potential safety hazards caused by opening the kettle at high temperature.

[0054] In the present invention, preferably, after the hydrothermal treatment, it further includes the steps of aging treatment, filtration, washing, and drying of the hydrothermal treatment product. There is no particular limitation on the aging conditions, and those skilled in the art can select conventional aging conditions. Preferably, the conditions of the aging treatment include: at room temperature, the aging time is 2 - 12 h.

[0055] In the present invention, there is no particular limitation on the separation method of the aged product. For example, conventional separation methods in the art such as filtration, suction filtration, and centrifugation can all achieve the purpose of the present invention.

[0056] In the present invention, the washing method is a conventional washing method in the art, and there is no particular limitation on the washing method and the washing solvent. Preferably, deionized water and ethanol can be used to wash the aged product.

[0057] In the present invention, there is no particular limitation on the drying conditions. According to a preferred embodiment of the present invention, the drying is carried out under vacuum, and the drying temperature is 50 - 100 °C. The reaction time can be reasonably adjusted according to actual needs. Preferably, the drying time is 12 - 48 h. Drying under vacuum can more fully remove the washing solvent.

[0058] According to the present invention, preferably, the calcination conditions include: the calcination temperature is 400 - 600 °C, preferably 450 - 550 °C; the calcination time is 3 - 36 hours, preferably 6 - 30 hours.

[0059] The third aspect of the present invention provides an iron-based catalyst prepared by the preparation method described in the second aspect.

[0060] The fourth aspect of the present invention provides an application of the iron-based catalyst described in the first aspect or the third aspect in the conversion of syngas to lower olefins.

[0061] In the present invention, the method for directly producing lower olefins from syngas includes: using syngas as a raw material, and contacting the raw material with the iron-based catalyst to react to produce lower olefins.

[0062] In the present invention, the lower olefins have the conventional meaning in the art, referring to hydrocarbons containing carbon-carbon double bonds with C2-C4.

[0063] According to the present invention, preferably, the conditions for the syngas conversion reaction include: the syngas includes CO and H 2 ; the reaction temperature is 280 - 400 °C; the reaction pressure is atmospheric pressure - 8 MPa; H 2 / CO molar ratio is 1 - 5:1; the catalyst loading is 500 - 12000 h -1 .

[0064] Before the catalyst of the present invention is used in the reaction for directly producing lower olefins from syngas, it is preferably first subjected to an on-line reduction treatment step. Specific reduction conditions can be reasonably selected by those skilled in the art without creative labor. For example, but not limited to, the reduction conditions include:

[0065] the reduction temperature is 350 - 600 °C;

[0066] the reducing agent is H 2 and / or CO;

[0067] the reduction pressure is atmospheric pressure - 2 MPa (gauge pressure);

[0068] the volumetric space velocity of the reducing agent is 2000 - 9000 h -1 ;

[0069] the reduction time is 12 - 60 hours.

[0070] According to a particularly preferred embodiment of the present invention, a method for preparing an iron-based catalyst, the method includes:

[0071] (1) Prepare a mixed solution containing an Fe source, an A source, an M source, a Q source, and a structure regulator;

[0072] (2) Hydrothermally treat the mixed solution, and dry and calcine the obtained solid product to obtain an iron-based catalyst;

[0073] wherein, A is Cu and / or Zr; M is Mg and / or Sr; Q is Nd and / or Sm;

[0074] In the mixed solution, the molar amount of the Fe source is calculated as Fe, the molar amount of the A source is calculated as A, and the molar ratio of the Fe source to the A source is 1:0.2 - 0.5;

[0075] The molar amount of the Fe source is calculated as Fe, the molar amount of the M source is calculated as M, and the molar ratio of the Fe source to the M source is 1:0.1 - 0.35;

[0076] The molar amount of the Fe source is calculated as Fe, the molar amount of the Q source is calculated as Q, and the molar ratio of the Fe source to the Q source is 1:0.05 - 0.15;

[0077] The structure regulator is poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and ammonium polyacrylate;

[0078] The addition amount of the structure regulator is 35 - 55 wt% of the total weight of the catalyst obtained.

[0079] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, the reagents used in the present invention are all commercially available;

[0080] The weight-average molecular weight of ammonium polyacrylate is 5000;

[0081] The weight-average molecular weight of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer is 5800.

[0082] Example 1

[0083] Dissolve ferric nitrate nonahydrate (molecular formula: Fe(NO 3 ) 3 ·9H 2 O) containing 0.1 mole of Fe, copper nitrate trihydrate (molecular formula: Cu(NO 3 ) 2 ·3H 2 O) containing 0.04 mole of Cu, magnesium nitrate hexahydrate (molecular formula: Mg(NO 3 ) 2 ·6H 2 O) containing 0.025 mole of Mg, and neodymium nitrate hexahydrate (molecular formula: Nd(NO 3 ) 3 ·6H 2 O) containing 0.01 mole of Nd in 100 mL of deionized water in sequence. After complete dissolution, a mixed solution I is obtained. Dissolve 4.8 grams of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) and 1.6 grams of ammonium polyacrylate in 30 mL of deionized water. After complete dissolution, add it to the mixed solution I and stir continuously to obtain a mixed solution II.

[0084] Pour the mixture II into a reaction kettle with a polytetrafluoroethylene substrate for hydrothermal treatment. Conduct hydrothermal treatment at a constant temperature of 180 °C for 36 hours, then cool to room temperature and age for 6 hours to obtain a solid product. Filter the solid product, wash it repeatedly with deionized water and ethanol, dry it under vacuum at 70 °C for 24 h, and then perform calcination at a calcination temperature of 500 °C for 16 h to obtain the catalyst.

[0085] Example 2

[0086] Dissolve ferric nitrate nonahydrate containing 0.1 mole of Fe (molecular formula: Fe(NO 3 ) 3 ·9H 2 O), cupric nitrate trihydrate containing 0.03 mole of Cu (molecular formula: Cu(NO 3 ) 2 ·3H 2 O), strontium nitrate containing 0.02 mole of Sr (molecular formula: Sr(NO 3 ) 2 ), and samarium nitrate hexahydrate containing 0.015 mole of Sm (molecular formula: Sm(NO 3 ) 2 ·6H 2 O) in 100 mL of deionized water in sequence. After complete dissolution, obtain mixture I. Dissolve 5.2 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) and 1.5 g of ammonium polyacrylate in 30 mL of deionized water. After complete dissolution, add it to mixture I and stir continuously to obtain mixture II.

[0087] Pour the mixture II into a reaction kettle with a polytetrafluoroethylene substrate for hydrothermal treatment. Conduct hydrothermal treatment at a constant temperature of 160 °C for 40 hours, then cool to room temperature and age for 5 hours to obtain a solid product. Filter the solid product, wash it repeatedly with deionized water and ethanol, dry it under vacuum at 70 °C for 20 h, and then perform calcination at a calcination temperature of 520 °C for 12 h to obtain the catalyst.

[0088] Example 3

[0089] Dissolve ferric nitrate nonahydrate containing 0.1 mole of Fe (molecular formula: Fe(NO 3 ) 3 ·9H 2 O), cupric nitrate trihydrate containing 0.04 mole of Cu (molecular formula: Cu(NO 3 ) 2 ·3H 2 O), barium nitrate containing 0.025 mole of Ba (molecular formula: Ba(NO 3 ) 2), lanthanum nitrate containing 0.01 mol of La (molecular formula: La(NO 3 ) 3 ) was successively dissolved in 100 mL of deionized water. After complete dissolution, a mixed solution I was obtained. 4.8 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) and 1.6 g of ammonium polyacrylate were dissolved in 30 mL of deionized water. After complete dissolution, it was added to the mixed solution I, and the mixture was continuously stirred to obtain a mixed solution II.

[0090] Under other conditions the same as in Example 1, a catalyst was obtained.

[0091] Example 4

[0092] According to the method of Example 1, the difference was that the structure regulator was changed to 7.6 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123), and other conditions were the same as in Example 1, to prepare a catalyst.

[0093] Example 5

[0094] According to the method of Example 1, the difference was that the hydrothermal treatment conditions were: hydrothermal treatment at 250 °C for 15 hours, and other conditions were the same as in Example 1, to prepare a catalyst.

[0095] Comparative Example 1

[0096] According to the method of Example 1, the difference was that the contents of the Fe source, A source, M source, and Q source in the mixed solution I were changed. Specifically:

[0097] Ferric nitrate nonahydrate containing 0.1 mol of Fe (molecular formula: Fe(NO 3 ) 3 ·9H 2 O), copper nitrate trihydrate containing 0.15 mol of Cu (molecular formula: Cu(NO 3 ) 2 ·3H 2 O), magnesium nitrate hexahydrate containing 0.4 mol of Mg (molecular formula: Mg(NO 3 ) 2 ·6H 2 O), neodymium nitrate hexahydrate containing 0.2 mol of Nd (molecular formula: Nd(NO 3 ) 3 ·6H 2 O) were successively dissolved in 100 mL of deionized water. After complete dissolution, a mixed solution I was obtained. Other conditions were the same as in Example 1, to prepare a catalyst.

[0098] Example 6

[0099] Prepare mixture I according to the method of Example 1, except that 28 wt% aqueous ammonia solution (molecular formula: NH 3 ·H 2 O) is added to mixture I, the pH value is maintained at 9.0, and after continuous stirring, it is aged at room temperature for 6 hours to obtain mixture II. Filter mixture II, wash it repeatedly with deionized water and ethanol, dry it under vacuum at 70 °C, and then carry out calcination. The calcination temperature is 500 °C and the calcination time is 16 h to obtain the catalyst.

[0100] Test Example

[0101] Evaluate the catalytic performance of the catalyst. The synthesis gas conversion reaction is carried out in a mm fixed-bed reactor. The composition, particle size and evaluation results of the catalyst are listed in Table 1.

[0102] Reduction conditions: The reduction temperature is 470 °C, the reducing agent is hydrogen, the reduction pressure is atmospheric pressure, the catalyst loading is 4 mL, and the volume space velocity of the reducing agent is 6500 h -1 , and the reduction time is 40 hours.

[0103] Reaction conditions: The reaction temperature is 370 °C, the reaction pressure is 1.3 MPa, the catalyst loading is 4 mL, the catalyst load is 5500 h -1 , and the raw material ratio (molar) H 2 / CO = 2.5 / 1.

[0104] Table 1

[0105]

[0106] It can be seen from the results in Table 1 that when the iron-based catalyst of the embodiment of the present invention is used for the reaction of synthesizing syngas to produce light olefins, it has a higher CO conversion rate and a higher light olefin selectivity.

[0107] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An iron-based catalyst, characterized in that, The catalyst has a structure represented by the following formula: FeA a M b Q c O x ; wherein, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements; a, b, and c are the molar ratios of A, M, and Q to Fe respectively, a = 0.1 - 0.6; b = 0.1 - 0.4; c = 0.05 - 0.2; x is the total number of oxygen atoms required to satisfy the valence of each element in the active component.

2. The catalyst according to claim 1, wherein, a＝0.2-0.5； preferably, M is Mg and / or Sr; preferably, b = 0.1 - 0.35; preferably, Q is Nd and / or Sm; preferably, c = 0.05 - 0.

15.

3. The catalyst according to claim 1 or 2, wherein, the particle size of the catalyst is 200 - 900 nm, preferably 250 - 500 nm.

4. A method for preparing an iron-based catalyst, characterized in that, the method comprises: (1) preparing a mixed solution containing an Fe source, an A source, an M source, a Q source, and a structure regulator; (2) subjecting the mixed solution to hydrothermal treatment, and drying and calcining the obtained solid product to obtain an iron-based catalyst; wherein, A is Cu and / or Zr; M is selected from at least one of the Group IIA metal elements; Q is selected from at least one of the lanthanide elements.

5. The preparation method according to claim 4, wherein, the Fe source is selected from at least one of iron nitrate, iron chloride, and iron sulfate; preferably, the A source, the M source, and the Q source are each independently a nitrate and / or a chloride; preferably, M is Mg and / or Sr; preferably, Q is Nd and / or Sm.

6. The preparation method according to claim 4 or 5, wherein, in the mixed solution, the molar amount of the Fe source is calculated as Fe, the molar amount of the A source is calculated as A, and the molar ratio of the Fe source to the A source is 1:0.1 - 0.6, preferably 1:0.2 - 0.5; preferably, the molar amount of the Fe source is calculated as Fe, the molar amount of the M source is calculated as M, and the molar ratio of the Fe source to the M source is 1:0.1 - 0.4, preferably 1:0.1 - 0.35; preferably, the molar amount of the Fe source is calculated as Fe, the molar amount of the Q source is calculated as Q, and the molar ratio of the Fe source to the Q source is 1:0.05 - 0.2, preferably 1:0.05 - 0.

15.

7. The preparation method according to any one of claims 4 - 6, wherein, the structure regulator is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and / or ammonium polyacrylate; preferably, the structure regulator is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer and ammonium polyacrylate; preferably, the mass ratio of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer to ammonium polyacrylate is 0.5 - 5:1, preferably 1 - 4:1; preferably, the addition amount of the structure regulator is 30 - 60 wt% of the total weight of the prepared catalyst, preferably 35 - 55 wt%.

8. The preparation method according to any one of claims 4 - 7, wherein, The conditions of the hydrothermal treatment include: the reaction temperature is 120 - 260 °C, preferably 140 - 240 °C; the reaction time is 12 - 60 hours, preferably 18 - 54 hours; Preferably, the calcination conditions include: the calcination temperature is 400 - 600 °C, preferably 450 - 550 °C; the calcination time is 3 - 36 hours, preferably 6 - 30 hours.

9. An iron-based catalyst prepared by the preparation method according to any one of claims 4 - 8.

10. Use of an iron-based catalyst according to any one of claims 1 - 3, 9 in the conversion of syngas into light olefins; Preferably, the conditions of the syngas conversion reaction include: The syngas includes CO and H 2 ; the reaction temperature is 280 - 400 °C; the reaction pressure is atmospheric pressure - 8 MPa; H 2 / CO molar ratio is 1 - 5:1; the catalyst loading is 500 - 12000 h -1 .

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