Iron-based catalysts, methods of making and using the same, and methods of producing lower olefins from synthesis gas

Abstract

The present application relates to the technical field of iron-based catalyst, in particular to an iron-based catalyst, a preparation method and application thereof, and a method for producing low-carbon olefins from synthesis gas, wherein the catalyst comprises the following components in parts by weight: component a) 20-40 parts, iron element and / or oxide of iron element; component b) 5-20 parts, at least one of alkaline earth metal element and oxide of alkaline earth metal element; component c) 1-10 parts, at least one of lanthanide metal or oxide of lanthanide metal; component d) 40-75 parts, SBA-15 molecular sieve; and the average pore size of the catalyst is 5-20 nm. The iron-based catalyst has the advantages of high carbon monoxide conversion rate and high low-carbon olefin selectivity when used in the reaction of producing low-carbon olefins from synthesis gas.

Description

Technical Field

[0001] This invention relates to the field of iron-based catalyst technology, specifically to an iron-based catalyst, its preparation method and application, and a method for producing low-carbon olefins from syngas. Background Technology

[0002] Syngas (CO+H2) can be used to directly produce low-carbon olefins (≤4 carbon atoms) through the Fischer-Tropsch synthesis reaction, which has the advantages of short process route, low energy consumption and wide availability of raw materials.

[0003] Mainstream research on catalysts for the Fischer-Tropsch synthesis of low-carbon olefins focuses primarily on iron-based catalysts, where the addition of promoters can significantly improve catalyst activity and selectivity. CN107961783A discloses a catalyst for synthesizing low-carbon olefins, using an impregnation method to prepare an iron-based catalyst. First, Sn-modified Al₂O₃ is used as a support, then the active component Fe and promoters are impregnated. This catalyst is used in the synthesis of low-carbon olefins from syngas at a reaction pressure of 3.0 MPa, a reaction temperature of 285 °C, and a volume hourly space velocity of 2400. -1 Under the condition that the H2:CO molar ratio is 2, the catalyst yields 55.49% of low-carbon olefins and has a low-carbon olefin selectivity of 61.61%, with a corresponding CO conversion of 90.07%. However, the catalyst has low carbon monoxide conversion and low-carbon olefin selectivity. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low carbon monoxide conversion and low selectivity of low-carbon olefins in the reaction of syngas to produce low-carbon olefins in the prior art, and to provide an iron-based catalyst, its preparation method and application, and a method for producing low-carbon olefins from syngas. When used in the reaction of syngas to produce low-carbon olefins, this catalyst has the advantages of high carbon monoxide conversion and high selectivity of low-carbon olefins.

[0005] To achieve the above objectives, a first aspect of the present invention provides an iron-based catalyst, which, by weight, comprises the following components:

[0006] Component a) 20-40 parts, iron and / or iron oxide;

[0007] Component b) 5-20 parts, at least one of alkaline earth metal elements and oxides of alkaline earth metal elements;

[0008] Component c) 1-10 parts, at least one of lanthanide metals or lanthanide metal oxides;

[0009] Component d) 40-75 parts, SBA-15 molecular sieve;

[0010] The catalyst has an average pore size of 5-20 nm.

[0011] A second aspect of the present invention provides a method for preparing the iron-based catalyst of the present invention, the method comprising:

[0012] (1) Dissolve the soluble compounds of alkaline earth metals, Ho soluble compounds and / or Gd soluble compounds in water to prepare solution A;

[0013] (2) The SBA-15 molecular sieve was impregnated in solution A to obtain mixture B;

[0014] (3) The mixture B was dried and calcined to obtain the modified SBA-15 molecular sieve;

[0015] (4) Add the modified SBA-15 molecular sieve to water to obtain a dispersion, add a Fe-soluble compound to the dispersion to obtain mixture D;

[0016] (5) Add a reducing agent to mixture D, and after the reaction, separate to obtain mixture E;

[0017] (6) Roast mixture E in air.

[0018] A third aspect of the present invention provides the application of the iron-based catalyst described herein in the reaction of syngas to produce low-carbon olefins.

[0019] A fourth aspect of the present invention provides a method for producing low-carbon olefins from syngas, the method comprising:

[0020] Syngas feedstock reacts with a catalyst, wherein the catalyst contains the iron-based catalyst described in this invention.

[0021] Through the above technical solution, the iron-based catalyst provided by the present invention has an average pore size of 5-20 nm, thereby improving catalyst activity and selectivity for low-carbon olefins.

[0022] Alkaline earth elements and lanthanides are used to modify the SBA-15 molecular sieve support, and then the supported active iron is reduced to prepare an iron-based catalyst. This allows for control of the catalyst's pore structure, resulting in a uniform distribution of the supported active iron particles, thereby improving the catalyst's activity and selectivity for low-carbon olefins.

[0023] The iron-based catalyst described in this invention has the advantages of high carbon monoxide conversion and high selectivity for low-carbon olefins when used in the synthesis of low-carbon olefins from syngas. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] The first aspect of the present invention provides an iron-based catalyst, which, by weight, comprises the following components:

[0026] Component a) 20-40 parts, iron and / or iron oxide;

[0027] Component b) 5-20 parts, at least one of alkaline earth metal elements and oxides of alkaline earth metal elements;

[0028] Component c) 1-10 parts, at least one of lanthanide metals and lanthanide metal oxides;

[0029] Component d) 40-75 parts, SBA-15 molecular sieve;

[0030] The catalyst has an average pore size of 5-20 nm.

[0031] According to a preferred embodiment of the present invention, the alkaline earth metal element is selected from Ca and / or Mg.

[0032] According to a preferred embodiment of the present invention, the content of component b) in the catalyst is 8-18 parts; this is beneficial to improving catalyst activity and low-carbon olefin selectivity.

[0033] According to a preferred embodiment of the present invention, the lanthanide metal is selected from Ho and / or Gd.

[0034] According to a preferred embodiment of the present invention, in the catalyst, component c) is an oxide of Ho and an oxide of Gd. Preferably, the mass ratio of Ho to Gd, based on the oxides, is 1:0.5-2; this is beneficial for improving catalyst activity and selectivity for low-carbon olefins.

[0035] Iron-based catalysts possessing the aforementioned characteristics of this invention can all achieve the objectives of this invention, and their preparation methods are not particularly required. Regarding this invention, according to a preferred embodiment of this invention, this invention provides a method for preparing the iron-based catalyst described herein, the method comprising:

[0036] (1) Dissolve the soluble compounds of alkaline earth metals and soluble compounds of lanthanides in water to prepare solution A;

[0037] (2) The SBA-15 molecular sieve was impregnated in solution A to obtain mixture B;

[0038] (3) The mixture B was dried and calcined to obtain the modified SBA-15 molecular sieve;

[0039] (4) Add the modified SBA-15 molecular sieve to water to obtain a dispersion, add a Fe-soluble compound to the dispersion to obtain mixture D;

[0040] (5) Add a reducing agent to mixture D, and after the reaction, separate to obtain mixture E;

[0041] (6) Roast mixture E in air.

[0042] In this invention, the range of types of reducing agents that can be selected is relatively wide, as long as ferrous ions are reduced. According to a preferred embodiment of this invention, the reducing agent is selected from at least one of sodium borohydride and / or triethylsodium borohydride.

[0043] In this invention, all ferrous salts can achieve the purpose of this invention, and there is no particular limitation on their types. According to a preferred embodiment of this invention, the soluble compound of Fe is selected from soluble ferrous salts, such as at least one of ferrous ammonium sulfate, ferrous sulfate and ferrous chloride, preferably ferrous ammonium sulfate and / or ferrous sulfate.

[0044] In this invention, the range of reducing agents and Fe-soluble compounds that can be selected is relatively wide. According to a preferred embodiment of this invention, the mass ratio of reducing agent to Fe element is 1.5-3.0.

[0045] In this invention, there is no particular limitation on the type of soluble compound of alkaline earth metal, as long as it can be soluble in water. For example, it can be a soluble salt of alkaline earth metal. According to a preferred embodiment of the present invention, the soluble compound of alkaline earth metal is selected from nitrates and / or acetates of alkaline earth metal, preferably calcium acetate and / or magnesium acetate.

[0046] In this invention, the lanthanide metal soluble compound is selected from at least one of Ho soluble compounds and Gd soluble compounds.

[0047] In this invention, there is no particular limitation on the type of soluble compound of Ho, as long as it can be soluble in water. For example, it can be a soluble salt of Ho. According to a preferred embodiment of the present invention, the soluble compound of Ho is selected from nitrates and / or acetates of Ho, preferably holmium acetate.

[0048] In this invention, there is no particular limitation on the type of soluble compound of Gd, as long as it can be soluble in water. For example, it can be a soluble salt of Gd. According to a preferred embodiment of the present invention, the soluble compound of Gd is selected from the nitrate and / or acetate of Gd; preferably gadolinium acetate.

[0049] In this invention, the range of roasting conditions that can be selected in steps (3) and (6) is relatively wide. According to a preferred embodiment of this invention, the roasting conditions in steps (3) and (6) each independently include: a temperature of 400-600℃; and adjusting the pulping time according to actual needs. Preferably, the time is 2-12 hours.

[0050] In this invention, there is no particular limitation on the separation method for solid-liquid separation. For example, conventional separation methods in the art, such as filtration, vacuum filtration, and centrifugation, can all achieve the purpose of this invention.

[0051] According to a preferred embodiment of the present invention, in step (5), after solid-liquid separation, the separated solid is washed alternately with water and anhydrous ethanol, and then vacuum dried to obtain mixture E.

[0052] According to a preferred embodiment of the present invention, the method for preparing the catalyst includes:

[0053] (1) Dissolve the soluble salts of alkaline earth metals, the soluble salts of Ho and / or the soluble salts of Gd in water to prepare solution A;

[0054] (2) The SBA-15 molecular sieve was impregnated in solution A to obtain a mixture. B ;

[0055] (3) The mixture B was dried and calcined in air to obtain the modified SBA-15 molecular sieve;

[0056] (4) Add the modified SBA-15 molecular sieve to an appropriate amount of water, and ultrasonically vibrate it to disperse it evenly; Fe soluble salt, stir evenly to obtain mixture D;

[0057] (5) Under stirring conditions, the reducing agent is slowly added to mixture D. After the reaction is complete, the mixture is centrifuged to obtain mixture E.

[0058] (6) The mixture E was washed alternately with water and anhydrous ethanol, dried under vacuum, and calcined in air to obtain the desired iron-based catalyst.

[0059] A third aspect of this invention provides the application of the iron-based catalyst described herein in the reaction of syngas to produce low-carbon olefins. When used in the reaction of syngas to produce low-carbon olefins, the catalyst described herein has the advantages of high carbon monoxide conversion and high selectivity for low-carbon olefins.

[0060] A fourth aspect of the present invention provides a method for producing low-carbon olefins from syngas, the method comprising:

[0061] Syngas feedstock reacts with a catalyst, wherein the catalyst contains the iron-based catalyst described in this invention.

[0062] According to a preferred embodiment of the present invention, the molar ratio of H2 to CO in the syngas feedstock is 0.5-4.

[0063] According to a preferred embodiment of the present invention, the contact reaction conditions include a temperature of 260-450°C.

[0064] According to a preferred embodiment of the present invention, the pressure is 0.1-4.0 MPa.

[0065] According to a preferred embodiment of the present invention, the volume hourly space velocity of the syngas feedstock is 1000-10000 h⁻¹. -1 .

[0066] Those skilled in the art will understand that the catalyst of the present invention preferably undergoes an online reduction process before being used in the direct production of low-carbon olefins from syngas. Specific reduction conditions can be reasonably selected by those skilled in the art without requiring inventive effort; for example, but not limited to, reduction conditions include:

[0067] The reduction temperature is 300-600℃;

[0068] The reducing agent is H2 and / or CO;

[0069] The reduction pressure is atmospheric pressure - 4 MPa (gauge pressure);

[0070] The volume hourly space velocity of the reducing agent is 1000-10000 hr. -1 ;

[0071] The restoration time is 2-60 hours.

[0072] Using the iron-based catalyst described in this invention, the CO conversion rate can reach 98.0%, and the selectivity of low-carbon olefins in hydrocarbons can reach 73.2%, achieving good technical results.

[0073] The present invention will be described in detail below through embodiments.

[0074] In the following examples, the reduction conditions for the iron-based catalyst are:

[0075] Temperature: 400℃

[0076] Pressure: Atmospheric pressure

[0077] Catalyst loading: 3ml

[0078] Volume hourly space velocity of the reducing agent: 5000 hours -1

[0079] Reducing gas: H2

[0080] Restoration time: 36 hours.

[0081] In this invention, the average pore size of the catalyst was measured using the BET cryogenic liquid nitrogen adsorption method on a Micromeritics TriStar 3000 multichannel physical adsorption instrument at an operating temperature of -196°C.

[0082] Example 1

[0083] (1) Weigh out 10.0 parts by weight of calcium acetate monohydrate (molecular formula: Ca(CH3COO)·H2O) and 6.0 parts by weight of holmium acetate hexahydrate (molecular formula: Ho(CH3COO)3·6H2O) and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0084] (2) The above solution A was immersed in 56.0 parts by weight of SBA-15 molecular sieve and left to stand for 24 hours to obtain mixture B;

[0085] (3) The mixture B was dried in air at 120°C and then calcined at 400°C for 15 hours to obtain the modified SBA-15 molecular sieve.

[0086] (4) Add the modified SBA-15 molecular sieve to 100 parts by weight of water, sonicate to disperse it evenly, add 28.0 parts by weight of Fe2O3 of ferrous ammonium sulfate hexahydrate (molecular formula: (NH4)2Fe(SO4)2·6H2O), stir evenly to obtain mixture D;

[0087] (5) Under stirring conditions, a sodium borohydride solution containing 39.7 parts by weight of NaBH4 was added to mixture D. After the reaction was complete, mixture E was obtained by centrifugation. Mixture E was washed alternately with water and anhydrous ethanol and dried under vacuum at 70°C.

[0088] (6) The dried mixture E was calcined in air at a temperature of 500°C for 6 hours to obtain the desired iron-based catalyst.

[0089] The prepared catalyst contained the following components by weight percentage: 28% Fe₂O₃, 10% CaO, 6% Ho₂O₃, and 56% SBA-15. The average pore size results of the catalyst characterized by BET are shown in Table 1.

[0090] The catalyst was evaluated after reduction, and the evaluation conditions were as follows:

[0091] φ8 mm fixed bed reactor

[0092] Reaction temperature 370℃

[0093] Reaction pressure 2.5 MPa

[0094] Catalyst loading volume 3ml

[0095] Catalyst loading 4000 hours -1

[0096] Raw material ratio (moles): H2 / CO = 3.0 / 1.

[0097] For ease of comparison, the composition and evaluation results of the catalyst of this invention are listed in Table 1.

[0098] Example 2

[0099] (1) Weigh out magnesium acetate tetrahydrate equivalent to 8.0 parts by weight of MgO and gadolinium acetate hexahydrate equivalent to 10.0 parts by weight of Gd2O3, and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0100] (2) The above solution A was immersed in 42.0 parts by weight of SBA-15 molecular sieve and left to stand for 24 hours to obtain mixture B;

[0101] (3) The mixture B was dried in air at 120°C and then calcined at 400°C for 15 hours to obtain the modified SBA-15 molecular sieve.

[0102] (4) Add the modified SBA-15 molecular sieve to 100 parts by weight of water, sonicate to disperse it evenly, add 40.0 parts by weight of Fe2O3 of ferrous ammonium sulfate hexahydrate (molecular formula: (NH4)2Fe(SO4)2·6H2O), stir evenly to obtain mixture D;

[0103] (5) Under stirring conditions, a solution of sodium triethylborohydride containing 42 parts by weight of sodium triethylborohydride was added to mixture D. After the reaction was complete, mixture E was obtained by centrifugation. Mixture E was washed alternately with water and anhydrous ethanol and dried under vacuum at 70°C.

[0104] (6) The dried mixture E was calcined in air at a temperature of 500°C for 6 hours to obtain the desired iron-based catalyst.

[0105] The catalyst, by weight percentage, contains the following components: 40% Fe2O3, 8% CaO, 10% Ga2O3, and 42% SBA-15.

[0106] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0107] Example 3

[0108] (1) Weigh out 18.0 parts by weight of calcium acetate monohydrate of CaO and 2.0 parts by weight of holmium acetate hexahydrate of Ho2O3, and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0109] (2) The above solution A was immersed in 60.0 parts by weight of SBA-15 molecular sieve and left to stand for 24 hours to obtain mixture B;

[0110] (3) The mixture B was dried in air at 120°C and then calcined at 400°C for 15 hours to obtain the modified SBA-15 molecular sieve.

[0111] (4) Add the modified SBA-15 molecular sieve to 100 parts by weight of water, sonicate to disperse it evenly, add 20.0 parts by weight of Fe2O3 of ferrous ammonium sulfate hexahydrate (molecular formula: (NH4)2Fe(SO4)2·6H2O), stir evenly to obtain mixture D;

[0112] (5) Under stirring conditions, a sodium borohydride solution containing 40 parts by weight of NaBH4 was added to mixture D. After the reaction was complete, the mixture was centrifuged to obtain mixture E. Mixture E was washed alternately with water and anhydrous ethanol and dried under vacuum at 70°C.

[0113] (6) The dried mixture E was calcined in air at a temperature of 500°C for 6 hours to obtain the desired iron-based catalyst.

[0114] The catalyst, by weight percentage, contains the following components: 20% Fe2O3, 18% CaO, 2% Ho2O3, and 60% SBA-15.

[0115] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0116] Example 4

[0117] The method is the same as in Example 1, except that the weight percentage of calcium in step (1) is different from that in Example 1, and the weight percentage of SBA-15 molecular sieve in step (2) is different from that in Example 1. Specifically:

[0118] (1) Weigh out 20.0 parts by weight of calcium acetate monohydrate (molecular formula: Ca(CH3COO)·HO) and 6.0 parts by weight of holmium acetate hexahydrate (molecular formula: Ho(CH3COO)3·6H2O) and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0119] (2) The above solution A was immersed in 46.0 parts by weight of SBA-15 molecular sieve and allowed to stand for 24 hours to obtain mixture B. The remaining conditions were the same as in Example 1.

[0120] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0121] Example 5

[0122] The method is the same as in Example 1, except that the weight percentage of calcium in step (1) is different from that in Example 1, and the weight percentage of SBA-15 molecular sieve in step (2) is different from that in Example 1. Specifically:

[0123] (1) Weigh out 5.0 parts by weight of calcium acetate monohydrate (molecular formula: Ca(CH3COO)·HO) and 6.0 parts by weight of holmium acetate hexahydrate (molecular formula: Ho(CH3COO)3·6H2O) and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0124] (2) The above solution A was immersed in 61.0 parts by weight of SBA-15 molecular sieve and allowed to stand for 24 hours to obtain mixture B. The remaining conditions were the same as in Example 1.

[0125] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0126] Example 6

[0127] The method is the same as in Example 1, except that component c is a mixture of Ho2O3 and Gd2O3 in a mass ratio of 1:2, specifically:

[0128] (1) Weigh out 10.0 parts by weight of calcium acetate monohydrate (molecular formula: Ca(CH2COO)·HO), 2.0 parts by weight of holmium acetate hexahydrate (Ho2O3), and 4.0 parts by weight of gadolinium acetate hexahydrate (Gd2O3), and dissolve them in 50.0 parts by weight of deionized water to prepare solution A. The remaining conditions are the same as in Example 1.

[0129] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0130] Comparative Example 1

[0131] The method is the same as in Example 1, except that Ca, Ho, and Fe are impregnated and loaded onto the SBA-15 molecular sieve, specifically as follows:

[0132] (1) Weigh out 10.0 parts by weight of calcium acetate monohydrate (molecular formula: Ca(CH3COO)2·H2O), 6.0 parts by weight of holmium acetate hexahydrate (molecular formula: Ho(CH3COO)3·6H2O), and 28.0 parts by weight of ferrous ammonium sulfate hexahydrate (molecular formula: (NH4)2Fe(SO4)2·6H2O) and dissolve them in 50.0 parts by weight of deionized water to prepare solution A;

[0133] (2) The above solution A was immersed in 56.0 parts by weight of SBA-15 molecular sieve and left to stand for 24 hours to obtain mixture B;

[0134] (3) Mixture B was vacuum dried at 70°C and calcined in air at 500°C for 6 hours to obtain the catalyst of this comparative example.

[0135] The catalyst was prepared and contained the following components by weight percentage: 28% Fe2O3, 10% CaO, 6% Ho2O3, and 56% SBA-15.

[0136] The catalyst was evaluated in the same manner as in Example 1, and the test results are shown in Table 1.

[0137] Comparative Example 2

[0138] The method of Example 1 was followed, except that sodium borohydride was not added in step (5). All other conditions were the same as in Example 1. The catalyst was evaluated as in Example 1, and the test results are shown in Table 1.

[0139] Table 1

[0140]

[0141] As can be seen from the results in Table 1, the catalysts described in Examples 1-6 of this invention have the advantages of high CO conversion and high selectivity for C2-C4 low-carbon olefins.

[0142] 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 inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An iron-based catalyst, characterized in that, The catalyst comprises the following components in parts by weight: Component a) 20-40 parts, iron and / or iron oxide; Component b) 5-20 parts, at least one of alkaline earth metal elements and oxides of alkaline earth metal elements; Component c) 1-10 parts, at least one of lanthanide metals and lanthanide metal oxides; Component d) 40-75 parts, SBA-15 molecular sieve; The catalyst has an average pore size of 5-20 nm; Lanthanide metals are selected from Ho and / or Gd. The preparation method of the iron-based catalyst includes: (1) dissolving soluble compounds of alkaline earth metals and soluble compounds of lanthanides in water to prepare solution A; (2) The SBA-15 molecular sieve was impregnated in solution A to obtain mixture B; (3) The mixture B was dried and calcined to obtain the modified SBA-15 molecular sieve; (4) Add the modified SBA-15 molecular sieve to water to obtain a dispersion, add a Fe-soluble compound to the dispersion to obtain mixture D; (5) Add a reducing agent to mixture D, and after the reaction, separate to obtain mixture E; (6) Roast mixture E in air.

2. The iron-based catalyst according to claim 1, wherein, The alkaline earth metal element is selected from Ca and / or Mg; and / or In the catalyst, the content of component b) is 8-18 parts.

3. The iron-based catalyst according to claim 1 or 2, wherein, Component c) consists of oxides of Ho and Gd, with the mass ratio of Ho to Gd being 1:0.5-2 based on the oxides.

4. The iron-based catalyst according to claim 1, wherein, The mass ratio of reducing agent to Fe element is 1.5-3.

0.

5. The iron-based catalyst according to claim 1 or 4, wherein, The reducing agent is selected from sodium borohydride and / or triethylborohydride; and / or The soluble compounds of Fe are selected from soluble ferrous salts.

6. The iron-based catalyst according to claim 1 or 4, wherein, The soluble compounds of Fe are at least one of ferrous ammonium sulfate, ferrous chloride, and ferrous sulfate.

7. The iron-based catalyst according to claim 1 or 4, wherein, Soluble compounds of alkaline earth metals are selected from nitrates and / or acetates of alkaline earth metals; and / or The lanthanide metal soluble compounds are selected from at least one of the soluble compounds of Ho and the soluble compounds of Gd.

8. The iron-based catalyst according to claim 1 or 4, wherein, The soluble compounds of alkaline earth metals are calcium acetate and / or magnesium acetate; and / or The lanthanide metal soluble compounds are selected from at least one of the following: nitrates and acetates of Ho, nitrates and acetates of Gd.

9. The iron-based catalyst according to claim 1 or 4, wherein, In steps (3) and (6), the roasting conditions are each independently included: temperature of 400-600℃; time of 2-12 hours.

10. The use of the iron-based catalyst according to any one of claims 1-9 in the reaction of producing low-carbon olefins from syngas.

11. A method for producing low-carbon olefins from syngas, characterized in that, The method includes: The syngas feedstock reacts with a catalyst, wherein the catalyst contains an iron-based catalyst as described in any one of claims 1-9.

12. The method according to claim 11, wherein, In the syngas feedstock, the molar ratio of H2 to CO is 0.5–4; and / or The contact reaction conditions include: a temperature of 260~450℃; a pressure of 0.1~4.0MPa; and / or Syngas feedstock volume hourly space velocity (VHSV) is 1000~10000 h⁻¹ -1 .

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