A supported cobalt-based catalyst for the fischer-tropsch synthesis and a method for its preparation

Abstract

This invention provides a supported cobalt-based catalyst for Fischer-Tropsch synthesis and its preparation method. The catalyst consists of cobalt tetroxide, a metal auxiliary oxide, and a support; the metal auxiliary oxide includes any one of zinc oxide, magnesium oxide, strontium oxide, barium oxide, or ferric oxide; the support is MAl2O4@Al2O3, where M is any one of Fe, Zn, Mg, Cu, Ni, or Co. The preparation method includes: quantitatively weighing the nitrate of metal M according to the catalyst composition, impregnating its aqueous solution in alumina, and subjecting it to a first drying, a first calcination, hydrothermal treatment, a second drying, and a second calcination to obtain the MAl2O4@Al2O3 support; quantitatively weighing the cobalt salt and the auxiliary metal salt according to the catalyst composition, impregnating their mixed aqueous solution onto the support, and subjecting it to a third drying and a third calcination. This invention solves the problem that the poor thermal conductivity of the support affects the catalytic performance of traditional cobalt-based catalysts in Fischer-Tropsch synthesis. It exhibits good thermal conductivity, high strength, strong industrial adaptability, and a simple method, making it easy to promote and use industrially.

Description

Technical Field

[0001] This invention belongs to the field of Fischer-Tropsch synthesis catalyst technology, and particularly relates to a supported cobalt-based catalyst for Fischer-Tropsch synthesis and its preparation method. Background Technology

[0002] In recent years, with the increasing scarcity of petroleum resources and the gradually stringent requirements for fuel, research in the field of Fischer-Tropsch synthesis has been very active, and many companies have conducted research and development in Fischer-Tropsch synthesis.

[0003] As is well known, reactors used in industrial production include slurry bed reactors, fluidized bed reactors, and fixed bed reactors. Among them, fixed bed reactors are the most commonly encountered system in the field of catalysis due to their advantages of simple design, easy operation, and easy product separation. However, in practical applications, fixed bed reactors also have shortcomings, namely, heat and mass transfer problems in the reaction process. In fixed bed reactors, for highly exothermic reactions, the poor thermal conductivity of the packed catalyst particles easily leads to local overheating of the catalyst bed, and in severe cases, even "runaway" phenomena, causing sintering of the active catalyst components and a decrease in catalytic performance. On the other hand, in industrial production, in order to reduce pressure drop, the catalyst particles packed in fixed bed reactors are usually large. At this time, the diffusion restriction within the catalytic reaction becomes very serious, greatly affecting the catalytic reaction rate and reducing product selectivity. Currently, methods to solve these problems include preparing catalysts using metal foam as a carrier and preparing eggshell-shaped catalysts.

[0004] The influence of the support on supported cobalt catalysts in the Fischer-Tropsch synthesis process is complex. To date, commonly used industrial cobalt-based Fischer-Tropsch catalyst supports still rely on traditional alumina, zirconium oxide, silicon oxide, and carbon materials, although some researchers have explored molecular sieves as supports. However, conventional oxides generally have poor thermal conductivity, making it difficult to transfer reaction heat effectively during the highly exothermic Fischer-Tropsch reaction, leading to "hot spots" and a decrease in their specific surface area, or even sintering of the supported active component. While silicon carbide has good thermal conductivity, it suffers from a low specific surface area, making it difficult to disperse metallic cobalt. Carbon materials, although having a large specific surface area, suffer from poor thermal conductivity, susceptibility to oxidation at high temperatures, and poor mechanical strength. Therefore, the development of novel cobalt-based catalyst supports is essential to advance the Fischer-Tropsch synthesis industry.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a supported cobalt-based catalyst for Fischer-Tropsch synthesis and its preparation method, so as to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A supported cobalt-based catalyst for Fischer-Tropsch synthesis, the catalyst comprising cobalt tetroxide, a metal auxiliary oxide, and a support; the metal auxiliary oxide comprising any one of zinc oxide, magnesium oxide, strontium oxide, barium oxide, or ferric oxide; the addition of the metal auxiliary oxide also acts as an electronic auxiliary agent, increasing the electron cloud density of cobalt, enhancing the ability of cobalt to activate CO, and strengthening the carbon chain growth capability.

[0009] The carrier is MAl2O4@Al2O3, where M is any one of Fe, Zn, Mg, Cu, Ni, and Co.

[0010] Preferably, the carrier MAl2O4@Al2O3 has a core-shell structure, wherein the core is MAl2O4, which has a spinel structure and has good thermal conductivity, oxidation resistance and high mechanical strength; the shell of Al2O3 provides abundant specific surface area and pores, which is beneficial to the good dispersion of metallic cobalt.

[0011] More preferably, the weight ratio of cobalt tetroxide, metal auxiliary oxide, and carrier is 12.5–25:1–10:100.

[0012] The supported cobalt-based catalyst for Fischer-Tropsch synthesis provided by this invention can be applied to the fixed-bed reaction of Fischer-Tropsch synthesis. Specific application conditions include: reduction conditions of 350–450 °C, 0.3–1.0 MPa, and GHSV = 500–1000 h⁻¹. -1 The reaction was carried out at a constant temperature for 12–24 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 25%–75% (v / v); the reaction conditions were: 200–240℃, 2.0–5.0 MPa, GHSV = 500–1500 h. -1 H2 / CO(v / v) = 2.0~2.5.

[0013] The present invention also provides a method for preparing the supported cobalt-based catalyst for Fischer-Tropsch synthesis, the method comprising the following steps:

[0014] S1: Based on the catalyst composition, a quantitative amount of nitrate of metal M is weighed, its aqueous solution is impregnated in alumina, and then it is sequentially subjected to first drying, first calcination, hydrothermal treatment, second drying and second calcination to obtain MAl2O4@Al2O3 support;

[0015] Among them, M metal includes any one of Fe, Zn, Mg, Cu, Ni, and Co;

[0016] The molar ratio of the nitrate of the metal M to the alumina is 0.1 to 0.5:1;

[0017] The molar ratio of the cobalt salt to the MAl2O4@Al2O3 support is 0.3 to 1:1;

[0018] The molar ratio of the auxiliary metal salt to the cobalt salt is 0.01 to 0.1:1;

[0019] The alumina is active alumina γ-Al2O3 or η-Al2O3;

[0020] The first drying temperature is 60–120℃, and the time is 6–12 hours; the first calcination temperature is 650–800℃, and the time is 2–8 hours; the hydrothermal treatment temperature is 120–240℃, and the time is 6–24 hours; the second drying temperature is 60–120℃, and the time is 6–12 hours; the second calcination temperature is 350–650℃, and the time is 2–8 hours.

[0021] Optionally, the temperature of the first drying can be any value between 60°C, 70°C, 80°C, 90°C, 100°C, 110°C and 120°C, and the time can be any value between 6h, 7h, 8h, 9h, 10h, 11h and 12h.

[0022] The temperature of the first roasting can be any value between 650℃, 700℃, 750℃ and 800℃, and the time can be any value between 2h, 3h, 4h, 5h, 6h, 7h and 8h.

[0023] The temperature of the hydrothermal treatment can be any value between 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃ and 240℃, and the time can be any value between 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24h.

[0024] The temperature of the second drying process can be any value between 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C, and the time can be any value between 6h, 7h, 8h, 9h, 10h, 11h, and 12h.

[0025] The second roasting temperature can be any value between 350℃, 400℃, 450℃, 500℃, 550℃, 600℃ and 650℃, and the time can be any value between 2h, 3h, 4h, 5h, 6h, 7h and 8h.

[0026] S2: According to the catalyst composition, cobalt salt and auxiliary metal salt are weighed quantitatively, and their mixed aqueous solution is impregnated onto the MAl2O4@Al2O3 support obtained in S1. Then, after a third drying and a third calcination, the supported cobalt-based catalyst for Fischer-Tropsch synthesis is obtained.

[0027] The cobalt salt includes cobalt nitrate and / or cobalt acetate; the auxiliary metal salt includes any one of zinc nitrate, magnesium nitrate, strontium nitrate, barium nitrate, or ferric nitrate.

[0028] The third drying temperature is 90–110℃, and the time is 6–14 hours; the third calcination temperature is 300–450℃, and the time is 4–8 hours. Optionally, the third drying temperature can be any value between 90℃, 95℃, 100℃, 105℃, and 110℃, and the time can be any value between 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, and 14 hours; the third calcination temperature can be any value between 300℃, 350℃, 400℃, and 450℃, and the time can be any value between 4 hours, 5 hours, 6 hours, 7 hours, and 8 hours.

[0029] Preferably, the impregnation in step S2 is a multiple impregnation; the multiple impregnation includes: impregnating the MAl2O4@Al2O3 support in batches and multiple times with the mixed aqueous solution of the cobalt salt and the auxiliary metal salt;

[0030] Alternatively, the aqueous solution of all the cobalt salt and the auxiliary metal salt can be repeatedly impregnated onto the MAl2O4@Al2O3 support;

[0031] More preferably, the multiple impregnations are 1 to 3 impregnations.

[0032] More preferably, the batch-by-batch or repeated immersion further includes: freeze-drying the product after each immersion for 10 to 30 minutes, and then raising it to room temperature before the next immersion.

[0033] Optionally, the freeze-drying time can be any value between 10 min, 15 min, 20 min, 25 min, and 30 min.

[0034] This invention utilizes an innovative preparation method to obtain a novel core-shell structured MAl2O4@Al2O3 support, which is then loaded with active components to prepare a novel cobalt-based catalyst. The core-shell support has a thermally conductive spinel MAl2O4 interior and an exterior composed of Al2O3 with well-developed pores and a large specific surface area. After a first drying and a first calcination, Al2O3@MAl2O4 with different MAl2O4 contents is obtained. These are then subjected to hydrothermal treatment to obtain MAl2O4@AlO(OH) with different AlO(OH) contents. Finally, a second drying and a second calcination process yields the MAl2O4@Al2O3 support. The content of AlO(OH) or Al(OH)3 grown on the alumina surface under hydrothermal conditions can be modulated by adjusting the hydrothermal temperature and time. The greater the amount of AlO(OH) or Al(OH)3, the thinner the thermally conductive core MAl2O4 and the thicker the Al2O3 shell of the MAl2O4@Al2O3 support. Conversely, the smaller the amount of AlO(OH) or Al(OH)3, the thicker the thermally conductive core MAl2O4 and the thinner the Al2O3 shell of the MAl2O4@Al2O3 support. By modulating the thickness of the thermally conductive core MAl2O4 and the Al2O3 shell of the MAl2O4@Al2O3 support, the synergistic regulation of the catalyst's thermal conductivity and dispersibility can be achieved.

[0035] The preparation method provided by this invention achieves precise control of the process parameters, particularly the narrow window of hydrothermal treatment temperature and time, through several key steps. This allows for precise control of the texture parameters of the catalyst, such as pore volume, pore size, and specific surface area. Furthermore, by controlling the calcination temperature and time, a composite oxide support with good thermal conductivity and a large specific surface area and appropriately sized pores and volumes is obtained. Further loading with cobalt yields a cobalt catalyst with both thermal conductivity and dispersibility, resulting in a significant improvement in catalytic performance. Calcination is carried out within a temperature range of 650–800°C, ensuring that the resulting composite support is a single crystalline phase with complete bonding, while also maintaining the strength of the support. In the process of catalyst loading, this invention uses a multiple impregnation method and a lower drying temperature to achieve catalyst loading, reduce the number of calcination times and lower the calcination temperature, further weaken the interaction between the support and cobalt, and save energy. The resulting composite support has a better pore structure with uniform pore size, interconnected pores, and a three-dimensional network structure, which is conducive to internal and external diffusion and mass transfer. At the same time, the resulting support structure is also very stable, which is conducive to improving strength and can serve as a good heat transfer medium.

[0036] The beneficial effects of this invention are:

[0037] The supported cobalt-based catalyst for Fischer-Tropsch synthesis provided by this invention solves the problem that the poor thermal conductivity of traditional cobalt-based catalyst supports affects the catalytic performance of cobalt-based catalysts in Fischer-Tropsch synthesis. Furthermore, it can adapt to a wide range of reduction and reaction conditions, has a large operating window, strong operability, and strong industrial adaptability. It also possesses outstanding advantages such as good thermal conductivity, large specific surface area, and high strength. When used in industrial Fischer-Tropsch synthesis, it offers advantages such as less bed temperature runaway, low methane selectivity, high olefin content, and concentrated product distribution. The total product contains CH4 ≤ 2.9% and C2-C4 ≥ 2.7% (of which C2... ＝ -C4 ＝ ≥2.3%, C5-C 10 ≥20.3% (of which C5) ＝ -C 10 ＝ ≥11.5%), C 11 -C 19 ≥25.3%, C 19 + ≤48.8%.

[0038] The preparation method provided by this invention is simple, easy to operate, and readily applicable to industrial production. It is particularly suitable for industrial fixed-bed reactors, effectively solving the heat transfer problem within the reactor and efficiently removing reaction heat. It can adapt to high space velocity reaction conditions, effectively improving catalytic reaction efficiency and increasing industrial production capacity. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] According to the preparation method provided by the present invention, a supported cobalt-based catalyst for Fischer-Tropsch synthesis is prepared, and its performance is tested. The specific steps are as follows:

[0042] S1: First, weigh 100g of γ-Al2O3, then weigh 19.75g of Zn(NO3)2·6H2O and prepare an aqueous solution. Impregnate the above γ-Al2O3, and then dry at 60℃ for 12h and calcine at 650℃ for 8h to obtain Al2O3@ZnAl2O4. Then, perform hydrothermal treatment at 150℃ for 18h to obtain ZnAl2O4@AlO(OH). Then, dry at 60℃ for 12h and calcine at 350℃ for 8h to obtain 108.14g of ZnAl2O4@Al2O3 support.

[0043] S2: 45.28 g of cobalt nitrate and 6.35 g of magnesium nitrate were dissolved in water to prepare a solution. An equal volume of this solution was impregnated onto 100 g of the ZnA12O4@Al2O3 support obtained in S1 above. The solution was dried at 100 °C for 10 h and calcined at 300 °C for 8 h to obtain a supported cobalt-based catalyst Co3O4-MgO / ZnA12O4@Al2O3 for Fischer-Tropsch synthesis. The weight ratio of Co3O4:MgO:ZnA12O4@Al2O3 in the obtained catalyst was 12.5:1:100.

[0044] S3: Take 5g of the supported cobalt-based catalyst obtained in S2 above and evaluate it in a fixed-bed reactor. Set the reduction conditions as follows: 350℃, 1.0MPa, GHSV = 500h. -1 The reaction was carried out at a constant temperature for 24 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 25% (v / v); the reaction conditions were: 200℃, 5.0 MPa, GHSV = 500 h. -1 H2 / CO(v / v) = 2.2.

[0045] Evaluation results: CH4 accounted for 2.9% of the total product, and C2-C4 accounted for 2.7% (of which C2... ＝ -C4 ＝ (accounting for 2.3%), C5-C 10 It accounts for 20.3% (of which C5) ＝ -C 10 ＝ (accounting for 11.5%), C 11 -C 19 25.3%, C 19 + It accounts for 48.8%.

[0046] Example 2

[0047] According to the preparation method provided by the present invention, a supported cobalt-based catalyst for Fischer-Tropsch synthesis is prepared, and its performance is tested. The specific steps are as follows:

[0048] S1: First, weigh 100g of η-Al2O3, then weigh 58.22g of Co(NO3)2·6H2O and prepare an aqueous solution. Impregnate the above η-Al2O3, and then dry at 80℃ for 10h and calcine at 700℃ for 7h to obtain Al2O3@CoAl2O4. Then, after hydrothermal treatment at 120℃ for 24h, obtain CoAl2O4@Al(OH)3. Then, after drying at 80℃ for 10h and calcining at 400℃ for 6h, obtain 115g of CoA12O4@Al2O3 support.

[0049] S2: 46.48 g of cobalt acetate and 12.13 g of zinc nitrate were dissolved in water to prepare a solution. An equal volume of this solution was impregnated onto 100 g of the CoA12O4@Al2O3 support obtained in S1 above. The solution was dried at 90 °C for 14 h and calcined at 350 °C for 6 h to obtain a supported cobalt-based catalyst, Co3O4-ZnO / CoA12O4@Al2O3, for Fischer-Tropsch synthesis. The weight ratio of Co3O4:ZnO:CoA12O4@Al2O3 in the obtained catalyst was 15:5:100.

[0050] S3: Take 5g of the supported cobalt-based catalyst obtained in S2 above and evaluate it in a fixed-bed reactor. Set the reduction conditions as follows: 380℃, 0.8MPa, GHSV = 750h. -1 The reaction was carried out at a constant temperature for 20 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 35% (v / v); the reaction conditions were: 210℃, 4.0 MPa, GHSV = 750 h. -1 H2 / CO(v / v) = 2.3.

[0051] Evaluation results: CH4 accounted for 2.9% of the total product, and C2-C4 accounted for 3.4% (of which C2... ＝ -C4 ＝ (accounting for 2.5%), C5-C 10 It accounts for 21.2% (of which C5) ＝ -C 10 ＝ (accounting for 11.7%), C 11 -C 19 27.4%, C 19 + It accounts for 45.1%.

[0052] Example 3

[0053] According to the preparation method provided by the present invention, a supported cobalt-based catalyst for Fischer-Tropsch synthesis is prepared, and its performance is tested. The specific steps are as follows:

[0054] S1: First, weigh 100g of γ-Al2O3, then weigh 72.6g of Cu(NO3)2·6H2O and prepare an aqueous solution. Impregnate the above γ-Al2O3, and then dry at 100℃ for 9h and calcine at 750℃ for 6h to obtain Al2O3@CuAl2O4. Then, after hydrothermal treatment at 180℃ for 15h, obtain CuAl2O4@AlOOH. Then, after drying at 90℃ for 9h and calcining at 450℃ for 4h, obtain 124g of CuA12O4@Al2O3 support.

[0055] S2: 63.38 g of cobalt nitrate and 4.08 g of anhydrous strontium nitrate were dissolved in water to prepare a solution. This solution was then impregnated twice with equal volumes onto 100 g of the CuA12O4@Al2O3 support obtained in S1. The solution was dried at 95 °C for 12 h and calcined at 350 °C for 6 h to obtain a supported cobalt-based catalyst Co3O4-SrO / CuA12O4@Al2O3 for Fischer-Tropsch synthesis. The weight ratio of Co3O4:SrO:CuA12O4@Al2O3 in the obtained catalyst was 20:2:100.

[0056] S3: Take 5g of the supported cobalt-based catalyst obtained in S2 above and evaluate it in a fixed-bed reactor. Set the reduction conditions as follows: 400℃, 0.7MPa, GHSV = 600h. -1 The reaction was carried out at a constant temperature for 16 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 45% (v / v); the reaction conditions were: 220℃, 3.0 MPa, GHSV = 1000 h. -1 H2 / CO(v / v) = 2.1.

[0057] Evaluation results: CH4 accounted for 3.7% of the total product, and C2-C4 accounted for 3.5% (of which C2... ＝ -C4 ＝ (accounting for 2.7%), C5-C 10 It accounts for 22.5% (of which C5) ＝ -C 10 ＝ (accounting for 12.5%), C 11 -C 19 29.7%, C 19 + It accounts for 40.6%.

[0058] Example 4

[0059] According to the preparation method provided by the present invention, a supported cobalt-based catalyst for Fischer-Tropsch synthesis is prepared, and its performance is tested. The specific steps are as follows:

[0060] S1: First, weigh 100g of η-Al2O3, then weigh 66.1g of Ni(NO3)2·6H2O and prepare an aqueous solution. Impregnate the above η-Al2O3, and then dry at 110℃ for 8h and calcine at 770℃ for 4h to obtain Al2O3@NiAl2O4. Then, perform hydrothermal treatment at 210℃ for 12h to obtain NiAl2O4@Al(OH)3. Finally, dry at 100℃ for 8h and calcine at 500℃ for 3h to obtain 129.8g of NiA12O4@Al2O3 support.

[0061] S2: 69.73 g of cobalt acetate and 5.11 g of anhydrous barium nitrate were dissolved in water to prepare a solution. This solution was then impregnated twice with equal volumes onto 100 g of the NiA12O4@Al2O3 support obtained in S1. The solution was dried at 105 °C for 8 h and calcined at 350 °C for 6 h to obtain a supported cobalt-based catalyst Co3O4-BaO / NiA12O4@Al2O3 for Fischer-Tropsch synthesis. The weight ratio of Co3O4:BaO:NiA12O4@Al2O3 in the obtained catalyst was 22.5:3:100.

[0062] S3: Take 5g of the supported cobalt-based catalyst obtained in S2 above and evaluate it in a fixed-bed reactor. Set the reduction conditions as follows: 420℃, 0.5MPa, GHSV = 800h. -1 The reaction was carried out at a constant temperature for 15 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 55% (v / v); the reaction conditions were: 230℃, 2.5 MPa, GHSV = 1250 h. -1 H2 / CO(v / v) = 2.4.

[0063] Evaluation results: CH4 accounted for 4.3% of the total product, and C2-C4 accounted for 4.1% (of which C2... ＝ -C4 ＝ (3.0%), C5-C 10 It accounts for 23.8% (of which C5) ＝ -C 10 ＝ (accounting for 11.8%), C 11 -C 19 31.4%, C 19 + It accounts for 36.4%.

[0064] Example 5

[0065] According to the preparation method provided by the present invention, a supported cobalt-based catalyst for Fischer-Tropsch synthesis is prepared, and its performance is tested. The specific steps are as follows:

[0066] S1: First, weigh 100g of γ-Al2O3, then weigh 128.0g of Mg(NO3)2·6H2O and prepare an aqueous solution. Impregnate the above γ-Al2O3, and then dry at 120℃ for 6h and calcine at 800℃ for 2h to obtain Al2O3@MgAl2O4. Then, perform hydrothermal treatment at 240℃ for 6h to obtain MgAl2O4@AlOOH. Finally, dry at 120℃ for 6h and calcine at 650℃ for 2h to obtain 120.2g of MgA12O4@Al2O3 support.

[0067] S2: 90.54 g of cobalt nitrate and 25.25 g of ferric nitrate were dissolved in water to prepare a solution. This solution was then impregnated in excess onto 100 g of the MgA12O4@Al2O3 support obtained in S1 above. The solution was dried at 110 °C for 6 h and calcined at 450 °C for 4 h to obtain a supported cobalt-based catalyst, Co3O4-Fe2O3 / MgA12O4@Al2O3, for Fischer-Tropsch synthesis. The weight ratio of Co3O4:Fe2O3:MgA12O4@Al2O3 in the obtained catalyst was 25:10:100.

[0068] S3: Take 5g of the supported cobalt-based catalyst obtained in S2 above and evaluate it in a fixed-bed reactor. Set the reduction conditions as follows: 450℃, 0.3MPa, GHSV = 1000h. -1 The reaction was carried out at a constant temperature for 12 hours, using nitrogen-containing hydrogen reducing gas with an H2 content of 75% (v / v); the reaction conditions were: 240℃, 2.0 MPa, GHSV = 1500 h. -1 H2 / CO(v / v) = 2.5.

[0069] Evaluation results: CH4 accounted for 5.5% of the total product, and C2-C4 accounted for 5.4% (of which C2... ＝ -C4 ＝ (4.1%), C5-C 10 It accounts for 24.0% (of which C5) ＝ -C 10 ＝ (accounting for 12.0%), C 11 -C 19 32.6%, C 19 + It accounts for 32.5%.

[0070] Example 6

[0071] The difference from Example 3 is that step S2 is performed by two impregnations. After the first impregnation, the impregnated product is freeze-dried for 20 minutes, then heated to room temperature, and then the second impregnation is performed.

[0072] The evaluation results of this embodiment are as follows: CH4 accounts for 3.0% of the total product, and C2-C4 accounts for 2.9% (of which C2... ＝ -C4 ＝ (accounting for 2.8%), C5-C 10 It accounts for 21.2% (of which C5) ＝ -C 10 ＝ (accounting for 13.0%), C 11 -C 19 30.8%, C 19 + It accounts for 44.2%.

[0073] Comparative Example 1

[0074] The supported catalyst was prepared according to the method provided in patent 201510167269.3 and applied to Fischer-Tropsch synthesis. The specific steps include:

[0075] S1: Catalyst Support Preparation: Based on a spinel content of 10 wt% in the modified alumina support, Co(NO3)2·6H2O, Al(NO3)3·9H2O, and citric acid were weighed and dissolved in distilled water to prepare a mixed solution. The aluminum ion concentration in the mixed solution was 0.2 mol / L, the molar ratio of aluminum ions to cobalt ions was 2.2, and the molar ratio of citric acid to aluminum ions was 6. The mixed solution was evaporated in an 80°C water bath with stirring until a minimum amount of viscous liquid was evaporated. The resulting viscous liquid was added to a catalyst support with a specific surface area of ​​152 m² / L. 2 / g of alumina powder was impregnated, with the alumina powder weighed at 89.42% of the carrier's mass fraction. The impregnation time was 20h, followed by drying at 120℃ for 12h, and then calcining at 800℃ for 5h to obtain a modified alumina carrier of 90% Al2O3-10% CoAl2O4 (mass fraction). The specific surface area of ​​the obtained modified alumina carrier was 98m². 2 / g, average pore size 10nm, pore volume 0.29cm³ 3 / g.

[0076] Catalyst preparation: Co(NO3)2·6H2O was weighed out at 15 (wt)% of the final catalyst. Distilled water was measured and prepared into a salt solution using the equal volume impregnation method. The solution was then impregnated onto the modified alumina catalyst support prepared above for 20 h. After impregnation, the solution was dried at 110 °C for 12 h and then calcined in air for 6 h at 400 °C. The resulting product is the cobalt-based Fischer-Tropsch catalyst 15% Co3O4 / 76.5% Al2O3-8.5% Co Al2O4 (mass fraction).

[0077] The catalyst was used in a fixed-bed reactor for the Fischer-Tropsch reaction. The catalyst loading was 2 ml. The reduction conditions were a hydrogen atmosphere, 0.5 MPa, and 400 °C for 6 h. The required feedstock was syngas. The reaction conditions were: H... 2 The molar ratio of CO / H2O is 2, the reaction temperature is 220℃, the reaction pressure is 2 MPa, and the volume hourly space velocity is 1000 h⁻¹. -1 The reaction results showed that the CO conversion rate was 35%, the CH4 selectivity was 9.9%, and the C conversion rate was [missing information]. 5+ Selectivity: 80.7%.

[0078] As can be seen from the examples and comparative examples, the catalyst provided by the present invention has low methane selectivity, low C2-C4 selectivity, and low C5-C4 selectivity. 10 Selectivity, lower C 11 -C19 Selectivity and higher C 19 + Selectivity, but also has a high C2 value. ＝ -C4 ＝ Selectivity, higher C5 ＝ -C 10 ＝ Selectivity. In contrast, traditional catalysts exhibit higher methane selectivity, higher C2-C4 selectivity, and higher C5-C selectivity. 10 Selectivity, higher C 11 -C 19 Selectivity and lower C 19 + Selectivity, but with a low C2 ＝ -C4 ＝ Selective, lower C5 ＝ -C 10 ＝ Selectivity. This indicates that the catalyst provided by this invention, when applied to the products of Fischer-Tropsch synthesis, results in a higher content of economically valuable low-carbon olefins and a higher content of economically valuable long-chain products suitable for use as lubricating oil base oils. Simultaneously, the catalyst provided by this invention can achieve superior C5... + The space-time yield is significantly higher than that of conventional catalysts. This indicates that the catalyst of this invention has excellent thermal conductivity, which improves the reaction rate; and that the catalyst has a large specific surface area, resulting in higher dispersion and reducibility of cobalt metal, thus leading to higher yields of the target product and overall space-time yield.

[0079] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a supported cobalt-based catalyst for Fischer-Tropsch synthesis, characterized in that, The catalyst is composed of cobalt tetroxide, metal auxiliary oxide, and a support. The metal auxiliary oxide includes any one of zinc oxide, magnesium oxide, strontium oxide, barium oxide, or ferric oxide; The support is MAl2O4@Al2O3, where M is any one of Fe, Zn, Mg, Cu, Ni, and Co; The carrier MAl2O4@Al2O3 has a core-shell structure, wherein the core is MAl2O4 and the shell is Al2O3; The MAl2O4 has a spinel structure; The weight ratio of cobalt tetroxide, metal auxiliary oxide, and carrier is 12.5~25:1~10:100; The preparation method includes the following steps: S1: Based on the catalyst composition, a quantitative amount of nitrate of metal M is weighed, its aqueous solution is impregnated in alumina, and then it is sequentially subjected to first drying, first calcination, hydrothermal treatment, second drying and second calcination to obtain MAl2O4@Al2O3 support; S2: According to the catalyst composition, cobalt salt and auxiliary metal salt are weighed quantitatively, and their mixed aqueous solution is impregnated onto the MAl2O4@Al2O3 support obtained in S1. Then, after a third drying and a third calcination, the supported cobalt-based catalyst for Fischer-Tropsch synthesis is obtained. Among them, M metal includes any one of Fe, Zn, Mg, Cu, Ni, and Co.

2. The preparation method according to claim 1, characterized in that, The alumina is active alumina γ-Al2O3 or η-Al2O3; The cobalt salt includes cobalt nitrate and / or cobalt acetate; The auxiliary metal salt includes any one of zinc nitrate, magnesium nitrate, strontium nitrate, barium nitrate, or ferric nitrate.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of the nitrate of metal M to the alumina is 0.1~0.5:1; The molar ratio of the cobalt salt to the MAl2O4@Al2O3 support is 0.3~1:1; The molar ratio of the auxiliary metal salt to the cobalt salt is 0.01 to 0.1:

1.

4. The preparation method according to claim 1, characterized in that, The first drying temperature is 60~120℃, and the time is 6~12h; The first roasting temperature is 650~800℃, and the time is 2~8h; The hydrothermal treatment is performed at a temperature of 120~240℃ for a duration of 6~24h. The second drying temperature is 60~120℃, and the time is 6~12h; The second roasting temperature is 350~650℃, and the time is 2~8h.

5. The preparation method according to claim 1 or 4, characterized in that, The third drying process is carried out at a temperature of 90~110℃ for 6~14 hours. The third roasting temperature is 300~450℃, and the time is 4~8h.

6. The preparation method according to claim 1, characterized in that, The immersion in step S2 is a multiple immersion process. The multiple impregnations include: impregnating the MAl2O4@Al2O3 support in batches and multiple times with the mixed aqueous solution of the cobalt salt and the auxiliary metal salt; Alternatively, the aqueous solution of all the cobalt salt and the auxiliary metal salt can be repeatedly impregnated onto the MAl2O4@Al2O3 support; The multiple immersions refer to 1 to 3 immersions.

7. The preparation method according to claim 6, characterized in that, The batch-by-batch or repeated immersion also includes: freeze-drying the product after each immersion for 10-30 minutes, and then raising it to room temperature before the next immersion.