Iron-based catalysts, their preparation methods and applications, and methods for preparing low-carbon olefins.

Abstract

This invention relates to the field of catalyst technology, specifically to an iron-based catalyst, its preparation method and application, and a method for preparing low-carbon olefins. The catalyst comprises a support and an active component; wherein, on an atomic basis, the active component has the general formula Fe. 100 A a Nd b Pd 0.01b O x A is selected from at least one metal element from Group IVB, Group VIB, and Group VIIB; the value of a ranges from 2 to 20; the value of b ranges from 1 to 10; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the molar ratio of Nd to Pd on the catalyst surface is 100:4.5-7.5 (elemental). When the catalyst of this invention is used in the FTO reaction, it not only exhibits high catalytic activity but also yields high C2 content. + Selectivity for olefins, especially C2-C4 olefins.

Description

Technical Field

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

[0002] Fischer-Tropsch synthesis is a complex reaction system in which CO and H2 (syngas) react under the action of a catalyst to produce hydrocarbons as the main products. In essence, it involves the hydrogenation of CO and the propagation of the carbon chain. This method was invented in 1923 by German scientists Frans Fischer and Hans Tropsch. The entire process involves reactions that produce alkanes, alkenes, methanation, the formation of oxygen-containing organic compounds, and the disproportionation of CO. Although all of these reactions can occur, the probability of their occurrence varies depending on the catalyst and operating conditions.

[0003] According to catalyst classification, Fischer-Tropsch catalysts can be divided into two main categories: iron-based catalysts and cobalt-based catalysts. According to operating conditions, they can be divided into high-temperature Fischer-Tropsch and low-temperature Fischer-Tropsch. Low-temperature Fischer-Tropsch can use both cobalt-based and iron-based catalysts, and the products are mainly straight-chain alkanes in liquid to waxy form. High-temperature Fischer-Tropsch mostly uses iron-based catalysts, and the products are mainly light gasoline and diesel components, with some C2-C4 low-carbon olefins as byproducts. CN1695804A introduces a precipitated iron-based catalyst for high-temperature Fischer-Tropsch synthesis.

[0004] Because the Fischer-Tropsch reaction is a strongly exothermic reaction, although there have been some attempts to apply fixed beds to the high-temperature Fischer-Tropsch production of light olefins, these methods suffer from drawbacks such as difficulty in heat removal within the reactor, susceptibility to temperature runaway, and easy deactivation of the catalyst. Fluidized beds can effectively overcome these problems associated with fixed beds, but currently, they still suffer from low olefin yields. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of easy deactivation of existing iron-based catalysts and low olefin selectivity in FTO reactions, and to provide a new iron-based catalyst, its preparation method, and its application. When used in the FTO reaction, this catalyst exhibits high catalytic activity, high selectivity for C2-C4 olefins, and also produces C2-C20 olefins with high chemical added value as byproducts.

[0006] To achieve the above objectives, a first aspect of the present invention provides an iron-based catalyst comprising a support and an active component; wherein, in atomic ratio, the active component has the general formula Fe. 100 A a Nd b Pd 0.01b O xA is selected from at least one of Group IVB, Group VIB and Group VIIB metal elements; the value of a ranges from 2 to 20; the value of b ranges from 1 to 10; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the molar ratio of Nd to Pd on the catalyst surface is 100:4.5-7.5 in terms of elements.

[0007] A second aspect of the present invention provides a method for preparing an iron-based catalyst, the method comprising:

[0008] (1) Precipitation is carried out by reacting an aqueous solution containing a soluble Fe source with a precipitant;

[0009] (2) Take the precipitate I obtained in step (1) and mix it with aqueous solution II containing A source, aqueous solution III containing Nd source and Pd source and carrier source, and add pH adjuster to obtain slurry. Then dry, optionally shape, perform first calcination in oxygen atmosphere, and perform second calcination in inert gas containing water vapor; wherein the water content in oxygen atmosphere is not greater than 1 ppm.

[0010] A third aspect of the present invention provides the application of the iron-based catalyst described herein in the FTO reaction.

[0011] A fourth aspect of the present invention provides a method for preparing low-carbon olefins, the method comprising: reacting syngas with a catalyst, wherein the catalyst comprises the iron-based catalyst described in the present invention.

[0012] By employing the above technical solution, the catalyst of this invention, when used in the FTO reaction, not only exhibits high catalytic activity but also yields high C2 content. + Selectivity for olefins, especially C2-C4 olefins. Detailed Implementation

[0013] 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.

[0014] A first aspect of the present invention provides an iron-based catalyst comprising a support and an active component; wherein, on an atomic basis, the active component has the general formula Fe. 100 A a Nd b Pd 0.01b O xA is selected from at least one of Group IVB, Group VIB and Group VIIB metal elements; the value of a ranges from 2 to 20; the value of b ranges from 1 to 10; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the molar ratio of Nd to Pd on the catalyst surface is 100:4.5-7.5 in terms of elements.

[0015] This invention provides a novel iron-based catalyst in which the elements in the active component of the catalyst interact synergistically, and by controlling the molar ratio of Nd to Pd on the catalyst surface to be 100:4.5-7.5, the catalytic activity of the catalyst can be significantly improved. Moreover, when this catalyst is used in the FTO reaction, it not only exhibits high catalytic activity but also yields high C2 content. + Selectivity for olefins, especially C2-C4 olefins.

[0016] In this invention, it is understood that, through the general formula Fe 100 A a Nd b Pd 0.01b O x The molar ratio of Fe, A, Nd, and Pd in ​​the active components is 100:a:b:0.01b, but this does not represent their actual molar content in the catalyst. For example, a = 100 / molar content of Fe in the catalyst * molar content of A in the catalyst.

[0017] According to the present invention, in some embodiments, the support is selected from TiO2. The catalyst of this embodiment exhibits excellent synergistic effects between the support and the active component, resulting in high catalytic activity and selectivity for C2-C4 olefins when used in the FTO reaction.

[0018] According to the present invention, the content of the support and the active component in the catalyst is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the mass ratio of the support to the active component is (50-80):(20-50), for example, 50:50, 60:40, 70:30, 80:20, or any range of two of the above ratios. The catalyst of this embodiment exhibits high catalytic activity and selectivity for C2-C4 olefins when used in the FTO reaction.

[0019] According to the present invention, in some embodiments, A is selected from Group VIB metals. The catalyst of this embodiment exhibits high catalytic activity and selectivity for C2-C4 olefins when used in the FTO reaction.

[0020] According to the present invention, in some preferred embodiments, A is at least one of Cr, Mo, and W. The catalyst of this embodiment exhibits high catalytic activity and selectivity for C2-C4 olefins when used in the FTO reaction.

[0021] According to the present invention, in some preferred embodiments, A is Cr. In the catalyst of this embodiment, the elements in the active component, as well as the active component and the support, exhibit superior synergistic effects. When this catalyst is used in the FTO reaction, it not only possesses high catalytic activity but also further increases C2. + The proportion of C2-C4 olefins in olefins.

[0022] According to the present invention, in some embodiments, the value of a is in the range of 5-15, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range composed of any two of the above values.

[0023] According to the present invention, in some embodiments, the value of b is in the range of 2-8, for example, 2, 3, 4, 5, 6, 7, 8, or any two of the above values.

[0024] According to the present invention, the preparation method of the iron-based catalyst is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the second aspect of the present invention provides a method for preparing an iron-based catalyst, the method comprising:

[0025] (1) Precipitation is carried out by reacting an aqueous solution containing a soluble Fe source with a precipitant;

[0026] (2) Take the precipitate I obtained in step (1) and mix it with aqueous solution II containing A source, aqueous solution III containing Nd source and Pd source and carrier source, and add pH adjuster to obtain slurry. Then dry, optionally shape, perform first calcination in oxygen atmosphere, and perform second calcination in inert gas containing water vapor; wherein the water content in oxygen atmosphere is not greater than 1 ppm.

[0027] In this invention, the preparation method of this invention can be used to prepare a specific catalyst with a molar ratio of Nd to Pd of 100:4.5-7.5 on the catalyst surface. In the specific calcination environment of the first and second calcination of this invention, a catalyst with specific lattice defects can be formed. When used in the FTO reaction, this catalyst not only has high catalytic activity, but also further increases the selectivity of C2+ olefins, especially the selectivity of C2-C4 olefins.

[0028] According to the present invention, in some embodiments, the conditions for the first calcination include a temperature of 550-750°C, preferably 580-720°C. The catalyst prepared using this embodiment, when used in the FTO reaction, not only exhibits high catalytic activity but also further increases C2. + Selectivity of olefins, especially those in the middle C2 region + Selectivity of C2-C4 olefins.

[0029] According to the present invention, in some embodiments, the conditions for the first calcination include a time of 0.5-5 hours, preferably 0.8-4.5 hours.

[0030] According to the present invention, in some embodiments, during the second calcination, the volume ratio of water vapor to inert gas in the water vapor-containing inert gas is 1-5:100, for example, 1:100, 2:100, 3:100, 4:100, 5:100, or any range of two of the above ratios. This embodiment can obtain a catalyst with specific lattice defects, exhibiting high catalytic activity. When this catalyst is used in the FTO reaction, it not only exhibits high catalytic activity but also further increases C2. + Selectivity of olefins, especially those in the middle C2 region + Selectivity of C2-C4 olefins.

[0031] According to the present invention, in some embodiments, the conditions for the second calcination include a temperature of 580-800°C, preferably 600-760°C. The catalyst obtained using this embodiment exhibits higher catalytic activity and yields a higher concentration of the target product C2 when used in the FTO reaction. + The proportion of C2-C4 olefins in olefins.

[0032] According to the present invention, in some embodiments, the conditions for the second calcination include a time of 0.5-5 hours, preferably 0.8-4.5 hours.

[0033] According to the present invention, the specific selection of the oxygen-containing atmosphere is not particularly limited as long as the purpose of the present invention can be achieved. It can be oxygen and / or air. Based on cost considerations, air is selected as the oxygen-containing atmosphere in the present invention, but the present invention is not limited to this.

[0034] According to the present invention, the choice of inert gas is not particularly limited as long as the purpose of the present invention can be achieved; for example, it can be nitrogen or argon.

[0035] According to the present invention, the amount of pH adjuster is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the addition of the pH adjuster makes the pH value of the slurry 1-5.

[0036] According to the present invention, the type of pH adjuster is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the pH adjuster is selected from at least one of ammonia, ethylenediamine, triethanolamine, methylamine and ethylamine.

[0037] According to the present invention, in some embodiments, the solid content of the slurry is 15-45% by weight.

[0038] According to the present invention, in some embodiments, the pulping conditions include: a temperature of 40-80°C, and optionally the addition of water.

[0039] According to the present invention, optional water supplementation means that water may be added or not added during pulping as needed. In the present invention, water may be selectively added during pulping according to the required solid content of the pulp.

[0040] According to the present invention, as long as the purpose of the present invention can be achieved, the method of precipitation in step (1) is not particularly limited. In some embodiments, the precipitation method in step (1) is co-current precipitation, that is, co-current precipitation of an aqueous solution containing a soluble Fe source and an aqueous solution containing a precipitant.

[0041] In this invention, it is understood that, in order to make the co-current sedimentation process more efficient, the precipitant in step (1) can be mixed with water before use.

[0042] According to the present invention, those skilled in the art will understand that precipitation is a fixed chemical reaction that occurs when the isoelectric point is reached, meaning that those skilled in the art can select the amount of precipitant as needed.

[0043] According to the present invention, the type of precipitant is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the precipitant is selected from alkaline precipitants, preferably at least one of ammonia, KOH, NaOH, K2CO3 and KHCO3.

[0044] According to the present invention, the precipitate I obtained in step (1) refers to the solid substance after precipitation in step (1). Those skilled in the art can obtain the solid substance in the material after precipitation in step (1) using conventional methods in the art. For example, the method of obtaining precipitate I includes: performing solid-liquid separation and washing on the material after precipitation in step (1) to obtain precipitate I.

[0045] According to the present invention, there is no particular limitation on the drying method when preparing the iron-based catalyst of the present invention. For example, a spray dryer can be used for spray drying. Optionally, molding means that molding can be selected or not selected as needed. When using a spray dryer for drying, the solid substances in the slurry can be directly dried and shaped into microspheres, that is, molding is carried out simultaneously during the drying process. Subsequent molding can be selected or not selected as needed.

[0046] According to the present invention, only the purpose of the present invention can be achieved. There are no special limitations on the conditions for drying using a spray dryer, such as the sprayer inlet temperature being 300-350°C and / or the outlet temperature being 170-230°C.

[0047] According to the present invention, the hot air medium used in spray drying is not particularly limited, and can be, for example, an inert gas and / or air, preferably a mixture of air and an inert gas (such as nitrogen and / or argon) in a volume ratio of 1:(3-7).

[0048] In this invention, the aqueous solution containing Fe source refers to a solution made by dissolving Fe source in water; the aqueous solution containing A source II refers to a solution made by dissolving A source in water; the aqueous solution containing Nd source and Pd source III refers to a solution made by dissolving Nd source and Pd source in water; the amount of water used in the aqueous solution containing Fe source, the aqueous solution containing A source II, and the aqueous solution containing Nd source and Pd source III is not particularly limited, as long as it can dissolve the corresponding raw material source and meet the requirements of the subsequent slurry.

[0049] According to the present invention, in some embodiments, the support source is selected from a sol solution of a support, preferably TiO2 sol. The catalyst obtained using the foregoing embodiments has better catalytic performance.

[0050] According to some embodiments of the present invention, the Fe source is selected from at least one of Fe nitrate, citrate, chloride and nitrite.

[0051] According to some embodiments of the present invention, the A source is selected from at least one of the nitrates, oxides and chlorides of A.

[0052] According to the present invention, in some embodiments, the Nd source comprises Nd nitrate and / or chloride.

[0053] According to the present invention, in some embodiments, the Pd source includes Pd nitrates and / or chlorides.

[0054] A third aspect of the present invention provides the application of the iron-based catalyst described herein in the FTO reaction.

[0055] FTO reaction refers to the reaction of syngas directly producing olefins. In this invention, the iron-based catalyst of this invention is used in the FTO reaction, which has a high conversion rate of CO in the syngas and can obtain a high proportion of C2-C4 olefin products.

[0056] A fourth aspect of the present invention provides a method for preparing low-carbon olefins, the method comprising: reacting syngas with a catalyst, wherein the catalyst comprises the iron-based catalyst described in the present invention.

[0057] In this invention, low-carbon olefins refer to C2-C4 olefins. When the iron-based catalyst of this invention is used to prepare low-carbon olefins, CO has a high conversion rate and a high proportion of C2-C4 olefin products can be obtained.

[0058] When the iron-based catalyst of this invention is used to prepare low-carbon olefins, it may or may not undergo reduction before the reaction. Preliminary reduction is preferred. More preferably, the reduction conditions include: under a H2 atmosphere, a preferred temperature of 380-500°C, a preferred pressure of atmospheric pressure to 8.0 MPa, and a preferred standard volume hourly space velocity of 2000-12000 h⁻¹. -1 The preferred reduction time is 4-500 hours.

[0059] According to a preferred embodiment of the present invention, the synthesis gas includes CO and H2, and preferably the volume ratio of CO to H2 is 1:2.5-4.5.

[0060] According to the present invention, the conditions for the contact reaction are not particularly limited as long as the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, the conditions for the contact reaction include: a reaction temperature of 300-380°C.

[0061] According to a preferred embodiment of the present invention, the conditions for the contact reaction include: a reaction pressure of 0.5-8.0 MPa.

[0062] According to a preferred embodiment of the present invention, the conditions for the contact reaction include: a standard volume hourly space velocity of 2000-12000 h⁻¹. -1 .

[0063] The present invention will be described in detail below through examples, in which the moisture content in the air is less than 1 ppm.

[0064] The catalysts in the examples and comparative examples were used in the reaction to prepare olefins from syngas. The catalysts were reduced by in-situ reduction. After the reduction was completed, the process conditions were directly switched to the synthesis reaction conditions in the reactor used for the reduction to start the reaction.

[0065] Reactor specifications: φ38 mm fluidized bed reactor;

[0066] Catalyst loading: 50 grams;

[0067] The reduction conditions were: temperature 00℃, pressure 1.2MPa, and catalyst loading (standard volume hourly space velocity) of 6000 hours. -1 The reducing gas is H2, and the reduction time is 12 hours.

[0068] The synthesis conditions for preparing low-carbon olefins from syngas were: reaction temperature of 350℃, reaction pressure of 1.5 MPa, and catalyst loading (standard volume hourly space velocity) of 6000 hours. -1 The ratio of raw materials in the syngas (molar) is CO / H2 = 1:4, and the reaction runs for 100 hours.

[0069] CO conversion rate = (CO reactor inlet flow rate - CO reactor outlet flow rate) / CO reactor inlet flow rate;

[0070] C2 + Olefin selectivity = C2 + Total carbon number of olefins / Total carbon number of organic matter in the product;

[0071] C a -C b Olefins / C2 + Mass content = C a -C b Total carbon number of olefins / C2 + Total carbon number of hydrocarbons.

[0072] Example 1

[0073] Preparation of iron-based catalysts:

[0074] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0075] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0076] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0077] Take 40wt% titanium sol containing 142g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0078] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ in air for 1 hour, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of steam to nitrogen of 3:100, to obtain an iron-based catalyst.

[0079] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0080] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:5.7.

[0081] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0082] Example 2

[0083] Preparation of iron-based catalysts:

[0084] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0085] Dissolve 3.8g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0086] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0087] Take 40wt% titanium sol containing 136.3g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0088] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 320℃ and the outlet temperature was 185℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 630℃ in air for 2 hours, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of steam to nitrogen of 4:100, to obtain an iron-based catalyst.

[0089] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr5Nd4Pd 0.04 O x +60wt%TiO2.

[0090] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:5.9.

[0091] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0092] Example 3

[0093] Preparation of iron-based catalysts:

[0094] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0095] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0096] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 35 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0008 mol of Nd(NO3)3·6H2O.

[0097] Take 40wt% titanium sol containing 152g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 30% with water to obtain slurry III.

[0098] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 300℃ and the outlet temperature was 170℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 600℃ in air for 3.5h, and then calcined at 750℃ for 1h in an atmosphere of water vapor:nitrogen with a volume ratio of 2:100, to obtain an iron-based catalyst.

[0099] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd8Pd 0.08 O x +60wt%TiO2.

[0100] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:6.2.

[0101] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0102] Example 4

[0103] Preparation of iron-based catalysts:

[0104] Dissolve 404g of Fe(NO3)3·9H2O in water to prepare a 0.5mol / L Fe elemental solution I;

[0105] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0106] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0107] Take 40wt% titanium sol containing 142g TiO2 and mix it with solution I, solution II and III. Stir and slurry at 50℃. At the same time, adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 18% with water to obtain slurry III.

[0108] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 183℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ in an air atmosphere for 1 hour, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of steam to nitrogen of 3:100, to obtain an iron-based catalyst.

[0109] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0110] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:4.5.

[0111] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0112] Example 5

[0113] Preparation of iron-based catalysts:

[0114] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0115] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0116] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0117] Take 40wt% titanium sol containing 142g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0118] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ in an air atmosphere for 1 hour, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of water vapor to nitrogen of 6:100, to obtain an iron-based catalyst.

[0119] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0120] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:7.5.

[0121] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0122] Example 6

[0123] Preparation of iron-based catalysts:

[0124] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0125] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0126] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0127] Take 40wt% silica sol containing 142g of SiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0128] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ in air for 1 hour, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of steam to nitrogen of 3:100, to obtain an iron-based catalyst.

[0129] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt% SiO2.

[0130] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:4.4.

[0131] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0132] Example 7

[0133] Preparation of iron-based catalysts:

[0134] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0135] Take 17.65g of (NH4)6Mo7O 24 Dissolve in water to prepare a 0.5 mol / L aqueous solution of Mo (II);

[0136] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O and PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0137] Take 40wt% titanium sol containing 142g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0138] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ in air for 1 hour, and then calcined at 600℃ for 2 hours in an atmosphere with a volume ratio of steam to nitrogen of 3:100, to obtain an iron-based catalyst.

[0139] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Mo 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0140] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:6.7.

[0141] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0142] Comparative Example 1

[0143] Preparation of iron-based catalysts:

[0144] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0145] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0146] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0147] Take 40wt% titanium sol containing 142g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0148] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was calcined in an air atmosphere at 650℃ for 1 hour and then calcined in an air atmosphere at 600℃ for 2 hours to obtain an iron-based catalyst.

[0149] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0150] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:2.2.

[0151] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0152] Comparative Example 2

[0153] Preparation of iron-based catalysts:

[0154] 404g of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5mol / L Fe elemental solution. The solution was then separated by co-current precipitation with 5wt% ammonia water containing 3.5mol of NH3. After washing three times with deionized water, fresh Fe(OH)3 precipitate I was obtained.

[0155] Dissolve 7.6g of Cr2O3 in water to prepare a 0.5mol / L aqueous solution of Cr II;

[0156] Prepare a 0.5 mol / L (Nd + 0.01 Pt) solution III by taking 17.5 g of Nd(NO3)3·6H2O and a 50 mg / ml PdCl2 solution containing 0.0004 mol of Nd(NO3)3·6H2O.

[0157] Take 40wt% titanium sol containing 142g TiO2, mix it with precipitate I and solutions II and III, stir and slurry at 50℃, and adjust the pH of the mixture to 5 with 25wt% ammonia water. Adjust the solid content of the mixture to 35% with water to obtain slurry III.

[0158] The slurry was spray-dried and shaped. The inlet temperature of the sprayer was 350℃ and the outlet temperature was 200℃. The hot air medium of the sprayer was a mixture of air and nitrogen with a volume ratio of 1:5, and the spray-dried material was obtained. The spray-dried material was first calcined at 650℃ for 1 hour in an atmosphere with a volume ratio of water vapor to nitrogen of 3:100, and then calcined at 600℃ for 2 hours to obtain an iron-based catalyst.

[0159] The composition of the obtained iron-based catalyst is: 40 wt% Fe 100 Cr 10 Nd4Pd 0.04 O x +60wt%TiO2.

[0160] XPS analysis showed that the molar ratio of Nd to Pd on the surface of the prepared catalyst was 100:8.1.

[0161] The catalyst was used in the reaction to produce low-carbon olefins from syngas, and the results are shown in Table 1.

[0162] Table 1

[0163]

[0164]

[0165] 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 includes a support and an active component; Wherein, in terms of atomic ratio, the general formula of the active component is Fe 100 A a Nd b Pd 0.01b O x ; A is selected from at least one metal element in Group VIB; the value of a ranges from 2 to 20; the value of b ranges from 1 to 10; and x is the total number of oxygen atoms required to satisfy the oxidation states of each element in the catalyst. On an elemental basis, the molar ratio of Nd to Pd on the catalyst surface is 100:4.5-7.5; The carrier is selected from TiO2; The mass ratio of the carrier to the active component is (50-80):(20-50).

2. The iron-based catalyst according to claim 1, wherein, A is selected from at least one of Cr, Mo, and W; and / or The value of 'a' ranges from 5 to 15; and / or The value of b ranges from 2 to 8.

3. The iron-based catalyst according to claim 2, wherein, A represents Cr.

4. A method for preparing the iron-based catalyst according to any one of claims 1-3, characterized in that, The preparation method includes: (1) Precipitation is carried out by reacting an aqueous solution containing Fe source with a precipitant; (2) Take the precipitate I obtained in step (1) and mix it with aqueous solution II containing A source, aqueous solution III containing Nd source and Pd source and carrier source, and add pH adjuster to obtain slurry. Then dry, optionally shape, perform first calcination in oxygen atmosphere, and perform second calcination in inert gas containing water vapor; wherein the water content in oxygen atmosphere is not greater than 1 ppm.

5. The preparation method according to claim 4, wherein, The conditions for the first roasting include: a temperature of 550-750℃; and / or a time of 0.5-5 hours; and / or During the second roasting, the volume ratio of water vapor to inert gas in the water vapor-containing inert gas is 1-5:100; and / or The conditions for the second roasting include: a temperature of 580-800℃; and / or a time of 0.5-5h.

6. The preparation method according to claim 5, wherein, The conditions for the first roasting include: a temperature of 580-720℃; and / or a time of 0.8-4.5 h; and / or The conditions for the second roasting include: a temperature of 600-760℃; and / or a time of 0.8-4.5h.

7. The preparation method according to claim 4, wherein, The addition of the pH adjuster makes the pH of the slurry 1-5; and / or The pH adjuster is selected from at least one of ammonia, ethylenediamine, triethanolamine, methylamine, and ethylamine; and / or The solid content of the slurry is 15-45% by weight; and / or The pulping conditions include a temperature of 40-80℃ and optional water addition.

8. The preparation method according to claim 4, wherein, In step (1), the precipitation method is co-current precipitation; and / or The precipitant is selected from alkaline precipitants; and / or The method for obtaining precipitate I includes: performing solid-liquid separation and washing on the precipitated material in step (1) to obtain precipitate I.

9. The preparation method according to claim 8, wherein, The precipitant is selected from at least one of ammonia, KOH, NaOH, K2CO3, and KHCO3.

10. The preparation method according to claim 4, wherein, The carrier source is selected from a sol solution of a carrier; and / or The Fe source is selected from at least one of Fe nitrate, citrate, chloride, and nitrite; and / or The A source is selected from at least one of the nitrates, oxides, and chlorides of A; and / or The Nd source includes Nd nitrates and / or chlorides; and / or The Pd source includes Pd nitrates and / or chlorides.

11. The preparation method according to claim 10, wherein, The carrier source is selected from TiO2 sol.

12. The use of the iron-based catalyst according to any one of claims 1-3 in the FTO reaction.

13. A method for preparing low-carbon olefins, characterized in that, The preparation method includes: Syngas is reacted with a catalyst, wherein the catalyst comprises the iron-based catalyst according to any one of claims 1-3.

14. The preparation method according to claim 13, wherein, The method also includes reducing the catalyst before use.

15. The preparation method according to claim 14, wherein, The reduction conditions include: under an H2 atmosphere; and / or a temperature of 380-500°C; and / or a pressure of atmospheric pressure to 8.0 MPa; and / or a standard volume hourly space velocity of 2000-12000 h⁻¹. -1 ; and / or the recovery time is 4-500 hours.

16. The preparation method according to claim 13, wherein, The synthesis gas includes CO and H2; and / or The conditions for the contact reaction include: a reaction temperature of 300-380℃; and / or a reaction pressure of 0.5-8.0 MPa; and / or a standard volume hourly space velocity of 2000-12000 h⁻¹. -1 .

17. The preparation method according to claim 16, wherein, The volume ratio of CO to H2 is 1:2.5-4.5.

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