Catalyst for preparing olefin from synthesis gas and preparation method thereof

Abstract

According to the catalyst for preparing olefin from synthesis gas and the preparation method, by means of the pore channel structure of porous carbon, active metal cobalt and iron are loaded in pore channels of a porous carbon carrier in a layered mode, an auxiliary is loaded on the surface of the porous carbon carrier, and due to the fact that the catalytic activation temperature of cobalt is lower, the catalytic activity of the catalyst is improved; the synthesis gas conversion reaction can be firstly started at a relatively low temperature, so that energy waste caused by activation of iron at a high temperature is avoided; an iron-based catalyst is high in activity but serious in internal diffusion, iron in a porous carbon carrier pore channel is difficult to quickly contact a reactant and start a reaction, and after cobalt is activated firstly, heat is transferred through a reaction atmosphere in the pore channel to drive the iron in the pore channel to participate in the reaction. Therefore, the catalyst provided by the invention does not need to depend on the high-temperature activation condition of iron, and the activity temperature of the whole catalyst is lowered; meanwhile, a large amount of iron serves as a main active center, and synthesis gas can be efficiently converted.

Description

Technical Field

[0001] This invention relates to the field of basic organic chemical manufacturing technology, and in particular to a catalyst for the preparation of olefins from syngas and a preparation method thereof. Background Technology

[0002] Olefins are the most important bulk organic chemical raw materials, with an annual output exceeding 100 million tons in my country. Traditional olefin production mainly involves high-temperature steam cracking of petroleum-based hydrocarbons, or the catalytic conversion of methanol obtained from coal or natural gas chemical processes onto molecular sieves. The former suffers from a heavy reliance on imported raw materials, while the latter faces challenges such as long processing routes, high energy consumption, and significant emissions.

[0003] One-step syngas-to-olefins (STO) is a recently emerging catalytic route with the potential to shorten processing time and reduce wastewater and CO2 emissions. However, STO essentially combines the two exothermic reactions of syngas-to-methanol and methanol-to-olefins into one, resulting in greater heat release. The thermal stability of the target product is low, leading to side reactions such as continuous hydrogenation or dehydrogenation and coking. Solutions include using reactors with excellent heat transfer properties; however, even with these solutions, porous catalysts exhibit strong internal diffusion effects, resulting in high internal temperatures. This means that macroscopic temperature control cannot accurately reflect the internal temperature of the catalyst, still leading to olefin loss.

[0004] Therefore, lowering the absolute reaction temperature is a viable approach. However, at low temperatures, the activity of iron-based catalysts is limited. While cobalt-based catalysts exhibit good low-temperature performance, their hydrogenation activity is too high, resulting in alkanes as the primary product. Currently, designing catalysts with high activity at low temperatures remains a challenge for the industry. Summary of the Invention

[0005] In view of the problems existing in the background art, the present invention provides a catalyst for the preparation of olefins from syngas with low temperature and high activity, and a preparation method thereof.

[0006] The specific details of the invention are as follows: In a first aspect, the present invention provides a catalyst for the preparation of olefins from syngas, the catalyst comprising: an active metal, a promoter metal, and a porous carbon support; wherein, The active metal includes cobalt and iron; wherein the cobalt and iron are layered and loaded inside the pores of the porous carbon support, the cobalt is loaded on the side closest to the porous carbon support, and the loading of iron is greater than the loading of cobalt. The auxiliary metal is selected from at least one of potassium, sodium, magnesium, cesium, lanthanum, cerium and thorium; In the catalyst, the active metal accounts for 20-35% of the total mass.

[0007] Optionally, the porous carbon support has a particle size of 3-300 μm and a specific surface area of ​​300-2200 m². 2 / g, with micropore volume of 0.5-1.2 ml / g and mesopore volume of 0.2-0.5 ml / g.

[0008] Optionally, in the catalyst, the cobalt accounts for 1-10% by mass, the iron accounts for 5-40% by mass, the auxiliary metal accounts for 2-15%, and the remainder is the porous carbon support.

[0009] Optionally, the catalyst is reduced at 350-400 °C for 2-6 hours and then used to catalyze the conversion of syngas into olefins; wherein the reaction of catalyzing the conversion of syngas into olefins is carried out at 260-320 °C and 2-4 MPa.

[0010] Optionally, the mass hourly space velocity of the syngas is 1-20 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 90-97%, and the hydrocarbon product yield is 27-32% based on syngas feedstock, of which the olefin selectivity is 60-80%.

[0011] Secondly, the present invention provides a method for preparing a catalyst for the synthesis of olefins from syngas, the method comprising: Cobalt salt, porous carbon, and deionized water are mixed to form a first dispersion, which is then dried at 1.5-2 MPa and 160-190 °C. The resulting solid is further calcined at 350-500 °C in an inert atmosphere to obtain the first catalyst precursor. The first catalyst precursor, iron salt and deionized water are mixed to form a second dispersion, which is then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined at 400-800 °C in an inert atmosphere to obtain the second catalyst precursor. The second catalyst precursor, the auxiliary metal salt, and deionized water are mixed to form a third dispersion, which is then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined in an inert atmosphere at 350-600 °C to obtain the catalyst.

[0012] Optionally, in the first dispersion, the mass ratio of the cobalt salt to the porous carbon is 0.01-0.3.

[0013] Optionally, the viscosity of the first dispersion is less than 1.1-1.2 centipoise.

[0014] Optionally, in the second dispersion, the mass ratio of the first catalyst precursor to the iron salt is 1-20.

[0015] Optionally, in the third dispersion, the mass ratio of the second catalyst precursor to the auxiliary metal salt is 5-50.

[0016] This invention provides a catalyst for the synthesis of olefins from syngas. The catalyst comprises an active metal, an additive, and a porous carbon support. The active metal includes cobalt and iron. The cobalt and iron are layered and loaded within the pores of the porous carbon support, with the cobalt loaded on the side closest to the porous carbon support, and the iron loading exceeding the cobalt loading. The additive is selected from at least one of potassium, sodium, magnesium, cesium, lanthanum, cerium, and thorium, and is loaded on the surface of the porous carbon support. The active metal comprises 20-35% by mass in the catalyst. Compared with the prior art, this invention has the following advantages: This invention effectively utilizes the principle that the internal temperature of the catalyst is higher in exothermic reactions. By leveraging the porous structure of carbon, active metals cobalt and iron are layered and loaded inside the pores of the porous carbon support, while the additives are loaded on the surface. Because cobalt has a lower catalytic activation temperature, it can initiate the syngas conversion reaction at a lower temperature. The released heat accumulates within the pores, effectively "igniting" the iron component deep within the pores, avoiding the energy waste caused by iron requiring high temperatures to activate. Iron-based catalysts have high activity but suffer from severe internal diffusion, making it difficult for iron within the porous carbon support pores to quickly contact reactants and initiate the reaction. However, after cobalt is activated first, it transfers heat through the reaction atmosphere within the pores, simultaneously engaging the iron deep within the pores. Therefore, the catalyst provided by this invention does not rely on the high-temperature activation conditions of iron, and the overall catalyst activity temperature is lowered. Simultaneously, a large amount of iron serves as the main active center, enabling efficient conversion of syngas, with a single-pass CO conversion rate of 90-97% and an olefin selectivity of 60-80%, achieving the dual goals of low-temperature energy saving and high efficiency and selectivity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the process for preparing a catalyst for syngas-to-olefins provided in an embodiment of the present invention is shown. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0020] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0021] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Existing syngas-to-olefins catalysts are mainly classified into iron-based, cobalt-based, and bimetallic systems. Among them, iron-based catalysts have become a research hotspot due to their low cost, readily available raw materials, and high olefin selectivity potential. However, they suffer from high activation temperatures (typically above 350 °C), significant energy consumption, and severe internal diffusion when supported on porous supports, making it difficult for iron active sites deep within the pores to quickly contact reactants, thus limiting catalytic efficiency. Cobalt-based catalysts have low activation temperatures (250-300 °C), but are expensive, have insufficient olefin selectivity when used alone, and high loading significantly increases industrial costs. Furthermore, existing bimetallic catalysts are mostly mixed-supported, failing to resolve the contradiction between internal diffusion and high-temperature activation in iron-based catalysts. Moreover, the preparation process makes it difficult to precisely control the distribution of active components, leading to unstable catalytic performance.

[0024] Therefore, developing a catalyst that can simultaneously achieve low-temperature activation, high-efficiency conversion, high olefin selectivity, and a controllable preparation process has become a pressing technical problem in this field. In view of this, the present invention provides a catalyst for syngas-to-olefins production and a corresponding preparation method. By optimizing the catalyst's component design, structural design, and preparation process, this invention provides a catalyst for syngas-to-olefins production and a corresponding preparation method, effectively solving the aforementioned technical problems and achieving the dual goals of low-temperature energy saving and high efficiency and selectivity. Specific implementation methods are as follows: In a first aspect, the present invention provides a catalyst for the preparation of olefins from syngas, the catalyst comprising: an active metal, a promoter metal, and a porous carbon support; wherein, The active metal includes cobalt and iron; wherein the cobalt and iron are layered and loaded inside the pores of the porous carbon support, the cobalt is loaded on the side closest to the porous carbon support, and the loading of iron is greater than the loading of cobalt. The auxiliary metal is selected from at least one of potassium, sodium, magnesium, cesium, lanthanum, cerium and thorium; In the catalyst, the active metal accounts for 20-35% of the total mass.

[0025] In practical implementation, given the low activation temperature of cobalt, this invention designs cobalt and iron to be layered and loaded inside the pores of a porous carbon support, serving as initiation sites to react first and catalyze the conversion of syngas. Due to the exothermic reaction, the internal temperature of the porous carbon support rises, and iron, as a highly active main catalytic center, is activated through the reaction atmosphere and heat transfer within the pores. Thus, the disadvantage of severe internal diffusion in iron-based catalysts is transformed into the advantage of extending the contact time of reactants. The auxiliary metal is loaded on the surface to avoid clogging the pores and to precisely regulate the catalytic performance. The active metal accounts for 20-35%, ensuring sufficient active sites while avoiding component aggregation, thus balancing catalytic activity and structural stability.

[0026] In some embodiments, the porous carbon support has a particle size of 3-300 μm and a specific surface area of ​​300-2200 m². 2 / g, with micropore volume of 0.5-1.2 ml / g and mesopore volume of 0.2-0.5 ml / g.

[0027] In practical implementation, the particle size range (3-300 μm) of the porous carbon support selected in this invention can effectively meet the filling requirements of industrial reaction beds, ensuring bed permeability and uniform fluid distribution; and the high specific surface area (300-2200 m²) 2 The / g) can provide sufficient loading sites for active components and avoid the aggregation of active metals; the matching design of micropore and mesopore pore volumes not only meets the spatial requirements of cobalt and iron stratified loading, but also provides efficient diffusion channels for reactants / products, further alleviating the internal diffusion problem and improving catalytic efficiency.

[0028] In some embodiments, the catalyst contains 1-10% cobalt by mass, 5-40% iron by mass, 2-15% auxiliary metal, and the remainder is the porous carbon support.

[0029] In specific implementation, the catalyst provided by this invention preferably contains 1-10% cobalt to achieve ignition function with a small amount and low cost, avoiding waste of cobalt resources; iron, as the main active center, preferably contains 5-40% to ensure syngas conversion efficiency; the auxiliary agent contains 2-15% to regulate catalytic performance (such as inhibiting methane formation, improving olefin selectivity, and promoting the desorption of olefins) through electronic and adsorption effects, without covering the active metal sites; and the porous carbon support contains a sufficient proportion to ensure the structural strength and pore stability of the catalyst.

[0030] In some embodiments, the catalyst is reduced at 350-400 °C for 2-6 hours and then used to catalyze the conversion of syngas into olefins; wherein the reaction of catalyzing the conversion of syngas into olefins is carried out at 260-320 °C and 2-4 MPa.

[0031] In specific implementation, the catalyst provided by this invention is reduced at 350-400 °C to convert the cobalt and iron components in the catalyst into active states (elemental or low-valence oxides) and avoid sintering of active components due to high temperature. Syngas can be used as the reducing atmosphere for the reduction treatment. After the reduction is completed, the reaction temperature is set to 260-320 °C and the reaction pressure is set to 2-4 MPa. Syngas is then introduced for catalytic conversion. This reaction temperature is lower than the catalytic temperature of traditional iron-based catalysts (above 350 °C), which can effectively reduce energy consumption and match the low-temperature activation characteristics of cobalt. The reaction rate and product selectivity of the syngas conversion reaction at a pressure of 2-4 MPa are suitable, which can avoid excessive hydrogenation of olefins due to excessive pressure.

[0032] In some embodiments, the mass hourly space velocity (MSV) of the syngas provided by the present invention is 1-20 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 90-97%, and the hydrocarbon product yield is 27-32% based on syngas feedstock, meeting the capacity requirements of industrial production; among which, the olefin selectivity is 60-80%; this is sufficient to show that the catalyst provided by the present invention has the advantages of high conversion efficiency and high purity of target product.

[0033] Secondly, the present invention provides a method for preparing a catalyst for the synthesis of olefins from syngas. Figure 1 A flowchart illustrating the preparation method of the catalyst for syngas-to-olefins provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes: S1. Cobalt salt, porous carbon and deionized water are mixed to form a first dispersion, and then dried at 1.5-2 MPa and 160-190 °C. The resulting solid is further calcined at 350-500 °C in an inert atmosphere to obtain the first catalyst precursor. S2. The first catalyst precursor, iron salt and deionized water are mixed to form a second dispersion, and then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined at 400-800 °C in an inert atmosphere to obtain the second catalyst precursor. S3. The second catalyst precursor, the auxiliary metal salt, and deionized water are mixed to form a third dispersion, which is then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined in an inert atmosphere at 350-600 °C to obtain the catalyst precursor.

[0034] In practice, stepwise loading is key to achieving cobalt and iron stratification and additive surface loading. Specifically, the first step loads cobalt onto the inner pores of the porous carbon support, the second step loads iron onto the outer surface of the cobalt, and the third step loads additives onto the support surface, preventing the mixing and agglomeration of different components. Furthermore, the high-pressure drying (1.5-2 MPa) in the first two steps promotes the penetration of metal salts into the pores, ensuring that the impregnated cobalt and iron components are not carried to the outer surface of the porous carbon by capillary vapor during moisture removal, thus guaranteeing structural effectiveness and significant catalytic effect. Calcination under an inert atmosphere enables the decomposition of metal salts and stable dispersion of active components, preventing oxidation or sintering.

[0035] This invention solves the core problems of high-temperature activation and severe internal diffusion in existing iron-based catalysts by employing a bimetallic layered loading design with a small amount of cobalt and a large amount of iron, suitable porous carbon support parameters, and a stepwise preparation process. It also avoids the high cost of cobalt-based catalysts. The catalyst achieves excellent performance with a single-pass CO conversion rate of 90-97% and an olefin selectivity of 60-80% at low temperatures of 260-320 °C, possessing the triple advantages of low-temperature energy saving, high-efficiency conversion, and high selectivity, and has significant prospects for industrial application.

[0036] In some embodiments, the mass ratio of the cobalt salt to porous carbon in the first dispersion is 0.01-0.3.

[0037] In some embodiments, the viscosity of the first dispersion is less than 1.1-1.2 centipoise.

[0038] In practice, a low-viscosity (<1.1-1.2 centipoise) dispersion has good fluidity and can fully penetrate into the micropores and mesopores of porous carbon, so that cobalt is uniformly loaded on the inside of the pores, avoiding excessive local concentration that would cause cobalt particles to agglomerate, and ensuring the uniformity and effectiveness of cobalt loading in the porous carbon pores.

[0039] In some embodiments, the mass ratio of the first catalyst precursor to the iron salt in the second dispersion is 1-20.

[0040] In some embodiments, the mass ratio of the second catalyst precursor to the auxiliary metal salt in the third dispersion is 5-50.

[0041] To enable those skilled in the art to more clearly understand the present invention, the following embodiments will be used to describe in detail a catalyst for syngas-to-olefins preparation and a preparation method thereof.

[0042] Example 1 2 g of porous carbon (specific surface area of ​​300 m²) 2 / g, micropore volume is 0.5 ml / g, mesopore volume is 0.2 ml / g. (Particle size is 300 micrometers) dispersed in deionized water and stirred at 20 r / min for 3 hours at room temperature, controlling its viscosity to be less than 1.1 centipoise.

[0043] Cobalt salt (0.12 g cobalt nitrate hexahydrate) was added to 30 ml of the above solution and stirred at 120 r / min for 3 hours. Then, the water in the solution was removed by purging with nitrogen at 1.5 MPa and 160 °C. The resulting solid was calcined at 500 °C under a nitrogen atmosphere for 1 hour.

[0044] The obtained solid was added to 30 ml of ferric salt (3.62 g ferric nitrate nonahydrate) solution and stirred at 260 r / min for 1 hour. Then, the water in the solution was removed by purging with air at 2 MPa and 190 °C. The obtained solid was then calcined at 800 °C under a nitrogen atmosphere for 1 hour.

[0045] The obtained solid was added to a 0.28 mol / L solution of 20 ml of auxiliary metal salts (75% sodium carbonate, 20% thorium nitrate, 2% cerium nitrate, and 3% cesium nitrate), and stirred at 120 r / min for 3 hours. Then, water was removed from the solution by purging with nitrogen at 2 MPa and 190 °C. The obtained solid was calcined at 600 °C under a nitrogen atmosphere for 4 hours. A catalyst product was obtained (a structure in which a small amount of cobalt and a large amount of iron are encapsulated in the channels of porous carbon; cobalt is mainly embedded in micropores, and iron is mainly embedded in micropores and small mesopores).

[0046] Analysis revealed that the catalyst contained 1% cobalt by mass, 20% iron carbide by mass, 5% additive metals by mass, and the remainder was porous carbon.

[0047] Further reduction with syngas at 400 °C for 2 hours. Then, syngas was introduced again for conversion. The optimized reaction conditions were 260 °C, 4 MPa, and a mass hourly space velocity (HHSV) of 1 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 90%, the hydrocarbon product yield is 27% (based on feedstock), and the olefin selectivity is 80% (based on hydrocarbon).

[0048] Example 2 1 g of porous carbon (specific surface area 2200 m²) 2 / g, micropore volume is 1.2 ml / g, mesopore volume is 0.5 ml / g. Particle size (3-60 micrometers) is dispersed in deionized water and stirred at 60 r / min for 1 hour at room temperature, controlling its viscosity to be less than 1.2 centipoise.

[0049] Cobalt salt (0.46 g cobalt nitrate hexahydrate) was added to 20 ml of the above solution and stirred at 120 r / min for 2 hours. Then, the water in the solution was removed by purging with nitrogen or air at 1.9 MPa and 180 °C. The resulting solid was calcined at 400 °C under a nitrogen atmosphere for 2 hours.

[0050] The obtained solid was added to 20 ml of a solution of ferric salt (2.85 g ferric nitrate nonahydrate) and stirred at 200 r / min for 2 hours. Then, the water in the solution was removed by purging with nitrogen at 1.9 MPa and 170 °C. The obtained solid was then calcined at 600 °C under a nitrogen atmosphere for 3 hours.

[0051] The obtained solid was added to a 0.3 mol / L, 15 ml auxiliary metal salt solution (20% sodium carbonate, 20% potassium carbonate, 60% thorium nitrate), and stirred at 180 r / min for 2 hours. Then, water was removed from the solution by purging with nitrogen at 1.7 MPa and 175 °C. The obtained solid was calcined at 500 °C under a nitrogen atmosphere for 2.4 hours. A catalyst product was obtained (a structure in which a small amount of cobalt and a large amount of iron are encapsulated in the channels of porous carbon; cobalt is mainly embedded in micropores, and iron is mainly embedded in micropores and small mesopores).

[0052] Analysis revealed that the catalyst contained 6% cobalt by mass, 25% iron carbide by mass, 10% additive metals by mass, and the remainder was porous carbon.

[0053] Further reduction with syngas at 350 °C for 2 hours. Then, syngas was introduced again for conversion. The optimized reaction conditions were 320 °C, 2 MPa, and a mass hourly space velocity (WHSV) of 20 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 97%, the hydrocarbon product yield is 32% (based on feedstock), and the olefin selectivity is 60% (based on hydrocarbon).

[0054] Example 3 4 g of porous carbon (specific surface area of ​​1500 m²) 2 The micropore volume is 0.8 ml / g, and the mesopore volume is 0.4 ml / g. The particles (50-200 μm in size) are dispersed in deionized water and stirred at 50 r / min for 3 hours at room temperature, with the viscosity controlled to be less than 1.15 centipoise.

[0055] Cobalt salt (0.93 g cobalt nitrate hexahydrate) was added to 50 ml of the above solution and stirred at 240 r / min for 1.5 hours. Then, the water in the solution was removed by purging with nitrogen at 1.8 MPa and 175 °C. The resulting solid was calcined at 450 °C under a nitrogen atmosphere for 3.5 hours.

[0056] The obtained solid was added to a 50 ml solution of ferric salt (10.2 g ferric nitrate nonahydrate), and stirred at 120 r / min for 3 hours. Then, the water in the solution was removed by purging with nitrogen or air at 2 MPa and 200 °C. The obtained solid was then calcined at 300 °C under a nitrogen atmosphere for 2 hours.

[0057] The obtained solid was added to a 0.4 mol / L, 50 mL solution of auxiliary metal salts (90% sodium carbonate, 5% lanthanum nitrate, 5% magnesium nitrate), and stirred at 260 r / min for 1 hour. Then, water was removed from the solution by air at 1.9 MPa and 190 °C. The obtained solid was calcined at 500 °C under a nitrogen atmosphere for 3 hours. A catalyst product was obtained (a structure in which a small amount of cobalt and a large amount of iron are encapsulated in the channels of porous carbon; cobalt is mainly embedded in micropores, and iron is mainly embedded in micropores and small mesopores).

[0058] Analysis revealed that the catalyst contained 3% cobalt by mass, 30% iron carbide by mass, 9% additive metals by mass, and the remainder was porous carbon.

[0059] Further reduction with syngas at 380 °C for 3 hours. Then, syngas was introduced again for conversion. The optimized reaction conditions were 300 °C, 2.5 MPa, and a mass hourly space velocity (HHSV) of 5 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 93%, the hydrocarbon product yield is 28.2% (based on feedstock), and the olefin selectivity is 78% (based on hydrocarbon).

[0060] Example 4 3 g of porous carbon (specific surface area 1200 m²) 2 / g, micropore volume is 0.6 ml / g, mesopore volume is 0.3 ml / g. Particle size (100-300 μm) is dispersed in deionized water and stirred at 50 r / min for 3 hours at room temperature, with the viscosity controlled to be less than 1.2 centipoise.

[0061] Cobalt salt (1.04 g cobalt nitrate hexahydrate) was added to 40 ml of the above solution and stirred at 250 r / min for 2.5 hours. Then, the water in the solution was removed by purging with nitrogen at 1.75 MPa and 185 °C. The resulting solid was calcined at 420 °C under a nitrogen atmosphere for 3 hours.

[0062] The obtained solid was added to a 40 ml solution of ferric salt (6.83 g ferric nitrate nonahydrate), and stirred at 180 r / min for 1.5 hours. Then, the water in the solution was removed by air at 1.6 MPa and 170 °C. The obtained solid was then calcined at 500 °C under a nitrogen atmosphere for 1 hour.

[0063] The obtained solid was added to a 0.32 mol / L, 30 mL solution of auxiliary metal salts (30% sodium carbonate, 30% thorium nitrate, 40% lanthanum nitrate), and stirred at 220 r / min for 2 hours. Then, water was removed from the solution by purging with air at 1.8 MPa and 195 °C. The obtained solid was calcined at 450 °C under a nitrogen atmosphere for 3.4 hours. A catalyst product was obtained (a structure in which a small amount of cobalt and a large amount of iron are encapsulated in the channels of porous carbon; cobalt is mainly embedded in micropores, and iron is mainly embedded in micropores and small mesopores).

[0064] Analysis revealed that the catalyst contained 5% cobalt by mass, 22% iron carbide by mass, 8% additive metals by mass, and the remainder was porous carbon.

[0065] Further reduction with syngas at 380 °C for 4 hours. Then, syngas was introduced again for conversion. The optimized reaction conditions were 290 °C, 3 MPa, and a mass hourly space velocity (WHSV) of 15 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 95%, the hydrocarbon product yield is 31% (based on feedstock), and the olefin selectivity is 72% (based on hydrocarbon).

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0067] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0068] The catalyst for syngas-to-olefins preparation and the preparation method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A catalyst for the synthesis of olefins from syngas, characterized in that, The catalyst comprises: an active metal, an additive, and a porous carbon support; wherein, The active metal includes cobalt and iron; wherein the cobalt and iron are layered and loaded inside the pores of the porous carbon support, the cobalt is loaded on the side closest to the porous carbon support, and the loading of iron is greater than the loading of cobalt. The additive metal is selected from at least one of potassium, sodium, magnesium, cesium, lanthanum, cerium, and thorium; the additive metal is loaded on the surface of the porous carbon support; In the catalyst, the active metal accounts for 20-35% of the total mass.

2. The catalyst for syngas-to-olefins production according to claim 1, characterized in that, The porous carbon support has a particle size of 3-300 μm and a specific surface area of ​​300-2200 m². 2 / g, with micropore volume of 0.5-1.2 ml / g and mesopore volume of 0.2-0.5 ml / g.

3. The catalyst for syngas-to-olefins production according to claim 1, characterized in that, In the catalyst, the mass percentage of cobalt is 1-10%, the mass percentage of iron is 5-40%, the mass percentage of the auxiliary metal is 2-15%, and the remainder is the porous carbon support.

4. The catalyst for syngas-to-olefins production according to claim 1, characterized in that, The catalyst, after being reduced at 350-400℃ for 2-6 hours, is used to catalyze the conversion of syngas into olefins; wherein the catalytic conversion of syngas into olefins is carried out at 260-320℃ and 2-4 MPa.

5. The catalyst for syngas-to-olefins production according to claim 4, characterized in that, The mass hourly space velocity of the syngas is 1-20 h⁻¹. -1 Under these conditions, the CO single-pass conversion rate is 90-97%, and the hydrocarbon product yield is 27-32% based on syngas feedstock, of which the olefin selectivity is 60-80%.

6. A method for preparing a catalyst for syngas-to-olefins production, characterized in that, The preparation method includes: Cobalt salt, porous carbon, and deionized water are mixed to form a first dispersion, which is then dried at 1.5-2 MPa and 160-190 °C. The resulting solid is further calcined at 350-500 °C in an inert atmosphere to obtain the first catalyst precursor. The first catalyst precursor, iron salt and deionized water are mixed to form a second dispersion, which is then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined at 400-800 °C in an inert atmosphere to obtain the second catalyst precursor. The second catalyst precursor, the auxiliary metal salt, and deionized water are mixed to form a third dispersion, which is then dried at 1.5-2 MPa and 160-200 °C. The resulting solid is further calcined in an inert atmosphere at 350-600 °C to obtain the catalyst precursor.

7. The method for preparing the catalyst for syngas-to-olefins according to claim 6, characterized in that, In the first dispersion, the mass ratio of cobalt in the cobalt salt to the porous carbon is 0.01-0.

3.

8. The method for preparing the catalyst for syngas-to-olefins according to claim 6, characterized in that, The viscosity of the first dispersion is less than 1.1-1.2 centipoise.

9. The method for preparing the catalyst for syngas-to-olefins according to claim 6, characterized in that, In the second dispersion, the mass ratio of the first catalyst precursor to the iron in the iron salt is 1-20.

10. The method for preparing the catalyst for syngas-to-olefins according to claim 6, characterized in that, In the third dispersion, the mass ratio of the second catalyst precursor to the auxiliary metal in the auxiliary metal salt is 5-50.

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