Fischer-Tropsch catalyst with porous structure as well as preparation method and application of Fischer-Tropsch catalyst

Abstract

The invention provides a Fischer-Tropsch catalyst with a porous structure as well as a preparation method and application of the Fischer-Tropsch catalyst. The preparation method comprises the following steps: S1, uniformly mixing TiO2 carrier powder with a pore-forming agent, kneading, carrying out extrusion molding, drying and roasting to obtain a porous carrier framework; s2, the porous carrier framework is placed in a precursor solution containing active metal to be subjected to equivalent-volume impregnation, drying and roasting, the Fischer-Tropsch catalyst is obtained, and the active metal is selected from at least one of iron, cobalt and copper. The specific pore-forming agent is introduced, the pore size distribution and the pore volume are regulated and controlled, a multistage pore channel structure from the nanoscale to the micron scale is constructed in the TiO2 carrier, then the active metal is loaded, the diffusion resistance of reactants and products in the pore channels is reduced through large pore channels, the anchoring sites of the active metal are improved through small pore channels, the utilization rate of the active sites is increased, and the catalytic activity of the catalyst is improved. And the generation of byproducts such as methane is reduced.

Description

Technical Field

[0001] This invention relates to the field of Fischer-Tropsch catalyst pore-forming and preparation technology, specifically to a Fischer-Tropsch catalyst with a porous structure, its preparation method, and its application. Background Technology

[0002] Fischer-Tropsch synthesis (FTS), a long-established catalytic conversion technology, efficiently converts non-petroleum-based carbon resources (such as coal, natural gas, biomass, and even CO2 from industrial waste gases) into high-value-added clean liquid fuels (such as gasoline, diesel, or jet fuel) and key chemical feedstocks (such as olefins or Fischer-Tropsch waxes). Fischer-Tropsch synthesis reactions typically employ iron-based, cobalt-based, or ruthenium-based catalysts, and the activity of the catalyst directly affects the selectivity of the target product and the long-term stability of the catalyst in the Fischer-Tropsch synthesis process.

[0003] The Fischer-Tropsch reaction process is complex, involving multiple steps including the diffusion of gaseous reactants into the active sites within the catalyst, adsorption and activation at these sites, surface catalytic reactions, and the desorption and diffusion of liquid hydrocarbon products from the active sites outwards from the catalyst pores. During this process, diffusion limitation significantly and adversely affects reaction performance. Due to mass transfer resistance within the narrow pores of the catalyst, the actual concentration of reactants at the active sites is much lower than the bulk concentration, leading to a reduced apparent reaction rate and limiting overall conversion efficiency. More critically, diffusion limitation exacerbates the concentration gradient distribution within the pores, altering the probability of chain propagation reactions and the extent of secondary reactions, resulting in decreased selectivity for the target product and increased byproducts such as methane. Furthermore, diffusion limitation prevents the full utilization of active sites deep within the catalyst particle pores, significantly reducing the catalyst's effective utilization rate.

[0004] Under conditions of limited mass transfer, intermediate products or heavy hydrocarbons tend to have prolonged residence time within the pores and accumulate near the active sites. This not only hinders effective contact between reactants and active sites but also significantly promotes polymer coking and carbon deposition, accelerating catalyst activity and selectivity degradation and leading to catalyst deactivation. Simultaneously, diffusion restriction can also impede heat transfer within the catalyst particles, creating localized temperature gradients that further affect reaction control precision and catalyst lifetime.

[0005] Since diffusion effects severely restrict the efficiency and economy of the overall Fischer-Tropsch synthesis process, there is an urgent need to develop a Fischer-Tropsch synthesis catalyst with an ideal porous structure to improve the catalyst's activity, selectivity, and stability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a Fischer-Tropsch catalyst with a porous structure, its preparation method, and its application, thus solving the problems mentioned in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a method for preparing a Fischer-Tropsch catalyst having a porous structure is provided, comprising the following steps: S1. Mix TiO2 carrier powder with pore-forming agent evenly, knead, extrude, dry, and calcine to obtain a porous carrier skeleton. S2. The porous support framework is placed in a precursor solution containing an active metal for equal-volume impregnation, dried, and calcined to obtain the Fischer-Tropsch catalyst, wherein the active metal is selected from at least one of iron, cobalt, and copper.

[0008] Preferably, in step S1, the pore-forming agent is selected from at least one of microcrystalline cellulose, polyvinyl alcohol, urea, polymethyl methacrylate, and hydroxypropyl methylcellulose, wherein the mass ratio of the pore-forming agent to the TiO2 carrier powder is 1:2~10.

[0009] Preferably, the precursor solution further includes an auxiliary metal, wherein the auxiliary metal is selected from at least one of manganese, zirconium, nickel, ruthenium, and potassium.

[0010] Preferably, the mass ratio of the active metal to the porous carrier skeleton is 5~30:100; The mass ratio of the auxiliary metal to the porous carrier skeleton is 1~4:100.

[0011] Preferably, in step S1, the amount of water used during the kneading process is 10-70% of the mixed powder; The perforated plate particle size in the extrusion molding process is 0.6~3mm; The roasting temperature is 300~700℃ and the time is 3~4h.

[0012] Preferably, in step S2, the calcination temperature is 200~600℃ and the time is 3~4h.

[0013] According to a second aspect of the present invention, a Fischer-Tropsch catalyst with a porous structure obtained according to the above preparation method is provided, comprising a TiO2 support and an active metal uniformly supported on the TiO2 support, wherein the TiO2 support has a mesoporous structure and the active metal is selected from at least one of iron, cobalt, and copper.

[0014] Preferably, the loading of the active metal is 10-30%.

[0015] Preferably, the TiO2 support is further loaded with an auxiliary metal, which is selected from at least one of manganese, zirconium, nickel, ruthenium, and potassium, and the loading amount of the auxiliary metal is 1 to 2%.

[0016] According to a third aspect of the present invention, the application of the above-described Fischer-Tropsch catalyst with a porous structure in the Fischer-Tropsch synthesis reaction is provided. Beneficial effects

[0017] This invention provides a Fischer-Tropsch catalyst with a porous structure, its preparation method, and its application. It offers the following advantages: 1. This scheme provides a method for preparing a Fischer-Tropsch catalyst with a porous structure. By introducing a specific pore-forming agent and controlling the pore size distribution and pore volume, a multi-level pore structure from nanoscale to microscale is constructed in a TiO2 support. Then, an active metal is loaded. The large pores reduce the diffusion resistance of reactants and products in the pores, while the small pores enhance the anchoring sites of the active metal, improve the utilization rate of active sites, and reduce the generation of by-products such as methane.

[0018] 2. This solution provides a method for preparing a Fischer-Tropsch catalyst with a porous structure. By using a specific water-to-powder ratio, the mechanical strength can be increased while preparing a support framework with the target pore structure, thus meeting the requirements of different reaction conditions for catalyst strength.

[0019] 3. The present solution provides a method for preparing a Fischer-Tropsch catalyst with a porous structure. By selecting an appropriate pore-forming agent, a porous support framework can be obtained simply by adding the pore-forming agent and water for calcination. Combined with an impregnation process, a catalyst with excellent stability and selectivity can be obtained. The preparation process is simple.

[0020] 4. The Fischer-Tropsch catalyst with a porous structure provided in this scheme can improve the selectivity of low-carbon olefins and long-chain hydrocarbons, significantly reduce the selectivity of methane, enhance the formation of target products, and suppress the generation of side reactions by setting a porous structure with a gradient during the Fischer-Tropsch synthesis reaction. Attached Figure Description

[0021] Figure 1 This is a graph showing the mercury intrusion data of the Fischer-Tropsch catalyst support prepared in Example 1 of the present invention; Figure 2 The XRD pattern of the Fischer-Tropsch catalyst with a porous structure prepared in Example 1 of this invention; Figure 3 This is a TEM image of the Fischer-Tropsch catalyst with a porous structure prepared in Example 1 of the present invention; Figure 4 This is a graph showing the mercury intrusion data of the Fischer-Tropsch catalyst support prepared in Example 2 of the present invention; Figure 5 This is a mercury intrusion porosimetry data diagram of the Fischer-Tropsch catalyst support prepared in Example 3 of the present invention; Figure 6 This is a graph showing the mercury intrusion data of the Fischer-Tropsch catalyst support prepared in Example 4 of the present invention; Figure 7 This diagram illustrates the CO conversion rate and CH4 selectivity of the Fischer-Tropsch catalysts prepared in Example 1 and Comparative Example 1 during the Fischer-Tropsch synthesis reaction. Detailed Implementation

[0022] To better illustrate the content of this invention, the following description is provided in conjunction with specific embodiments.

[0023] This invention provides a method for preparing a Fischer-Tropsch catalyst with a porous structure, the specific preparation method of which is as follows: Step 1: Dry mix TiO2 carrier powder and pore-forming agent powder for 1-2 hours until uniform. Then add water to the mixed powder and knead it. Extrude it into strip-shaped preforms using an extruder. After extrusion, dry the preforms in an oven at 100°C for 2 hours. After cooling, place the sample in a muffle furnace and calcine it in an air atmosphere at 300-700°C to obtain a porous carrier skeleton. Step 2: Impregnate the porous support framework with a precursor solution containing active metal in an equal volume, so that the active component is loaded into the pores of the porous support framework. Dry at room temperature for 24 hours, and then place in a muffle furnace and calcine in air at 200~600℃ to obtain a Fischer-Tropsch catalyst with a porous structure.

[0024] The pore-forming agent in this invention has the function of regulating pore structure. Specifically, it is selected from at least one of microcrystalline cellulose, polyvinyl alcohol, urea, polymethyl methacrylate, and hydroxypropyl methylcellulose. The mass ratio of the pore-forming agent to the TiO2 carrier powder is 1:2 to 10.

[0025] The precursor solution containing the active metal in this invention is selected from the nitrate solution, sulfate solution or chloride solution corresponding to the active metal.

[0026] In addition to the active metal, the precursor solution of the present invention also includes an auxiliary metal, wherein the auxiliary metal is selected from at least one of manganese, zirconium, nickel, ruthenium, and potassium.

[0027] In this invention, the mass ratio of the active metal to the porous carrier skeleton is 5~30:100; The mass ratio of the auxiliary metal to the porous carrier skeleton is 1~4:100.

[0028] In this invention, the amount of water added during the kneading process is 10-70% of the mixed powder. By adjusting the amount of water added, the strength of the porous carrier skeleton can be adjusted. By adjusting the amount of pore-forming agent and water, the porous structure and strength of the porous carrier skeleton can be optimized.

[0029] The following detailed description, in conjunction with specific embodiments, illustrates a Fischer-Tropsch catalyst with a porous structure, its preparation method, and its applications.

[0030] Example 1 Step 1: P25 TiO2 carrier powder and microcrystalline cellulose are dry-mixed at a mass ratio of 5:1 to obtain a mixed powder. Then, deionized water is added at a water-to-powder ratio of 4:7 and kneaded until the powder becomes dough-like. Then, the preform strips with a diameter of 0.8 mm are extruded using an extruder. The preform strips are then transferred to an oven at 100°C and dried for 2 hours. They are then calcined in an air atmosphere at 350°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt nitrate and zirconium nitrate, wherein the mass ratio of cobalt ions in cobalt nitrate to porous support framework is 10:100, and the mass ratio of zirconium ions in zirconium nitrate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in a muffle furnace at 250°C for 3 hours in air atmosphere to obtain a Fischer-Tropsch catalyst with a porous structure.

[0031] The performance of the Fischer-Tropsch catalyst prepared in Example 1 was tested, according to... Figure 1 It can be seen that the peak with a pore size of 40 nm is the inherent pore peak between TiO2 crystals, accounting for 81.67%. The two peaks with larger pore sizes are pore peaks generated by microcrystalline cellulose pore formation, with pore sizes of 340 nm and 2950 nm, respectively. Among them, the pore size of 2950 nm accounts for about 6.55%, and the pore size of 340 nm accounts for 11.78%. according to Figure 2 It can be clearly seen that the diffraction peaks of TiO2 crystals correspond to 25.313°, 36.966°, 37.837°, 38.593°, 48.066°, 53.906°, 55.098°, 62.711°, 68.9°, 70.324°, and 75.118°, respectively. In addition, there are obvious diffraction peaks of Co3O4, corresponding to 19.066°, 31.154°, 36.849°, 38.569°, 44.724°, 59.34°, and 65.239°, respectively. Random samples were taken from the same batch of Fischer-Tropsch catalyst prepared in this example, and the sample data are shown in Table 1.

[0032] Table 1

[0033] according to Figure 3 It is clear that the active metal elements and auxiliary metal elements are uniformly loaded onto the surface of the TiO2 support.

[0034] Example 2 Step 1: P25 TiO2 carrier powder and polymethyl methacrylate are dry-mixed at a mass ratio of 10:1 to obtain a mixed powder. Then, deionized water is added at a water-to-powder ratio of 1:2 and kneaded until the powder becomes dough-like. Then, a preform strip with a diameter of 0.8 mm is extruded using an extruder. The preform strip is then transferred to an oven at 100°C and dried for 3 hours. It is then calcined in an air atmosphere at 400°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt nitrate and nickel nitrate, wherein the mass ratio of cobalt ions in cobalt nitrate to porous support framework is 20:100, and the mass ratio of nickel ions in nickel nitrate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in an air atmosphere at 300°C for 3 hours to obtain a Fischer-Tropsch catalyst with a porous structure.

[0035] according to Figure 4 The mercury intrusion porosimetry data shows that the peak with a pore size of 50 nm is the inherent pore peak between TiO2 crystals, accounting for 37.84%, while the peak with a larger pore size is the pore peak generated by polymethyl methacrylate pore formation, with a pore size of 100 μm, accounting for about 62.16%.

[0036] Example 3 Step 1: P25 TiO2 carrier powder, polymethyl methacrylate, and hydroxypropyl methylcellulose are dry-mixed in a mass ratio of 10:2:1 to obtain a mixed powder. Then, deionized water is added in a water-to-powder ratio of 1:3 and kneaded until the powder becomes dough-like. Then, a preform strip with a diameter of 0.8 mm is extruded using an extruder. The preform strip is then transferred to an oven at 100°C and dried for 3 hours. Finally, it is calcined in an air atmosphere at 500°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt nitrate and nickel nitrate, wherein the mass ratio of cobalt ions in cobalt nitrate to porous support framework is 30:100, and the mass ratio of nickel ions in nickel nitrate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in an air atmosphere at 300°C for 3 hours to obtain a Fischer-Tropsch catalyst with a porous structure.

[0037] according to Figure 5The mercury intrusion porosimetry data show that the peak with a pore size of 25 nm is an inherent pore peak between TiO2 crystals, accounting for 63.22%. The two larger pore peaks are pore peaks generated by polymethyl methacrylate (PMMA), with pore sizes of 2800 nm and 8700 nm, accounting for 34.31% and 2.47%, respectively. In this embodiment, hydroxypropyl methylcellulose is added as a pore-forming agent, which improves the strength of the porous carrier skeleton while creating pores.

[0038] Example 4 Step 1: P25 TiO2 carrier powder and polyvinyl alcohol are dry-mixed at a mass ratio of 10:3 to obtain a mixed powder. Then, deionized water is added at a water-to-powder ratio of 3:7 and kneaded until the powder becomes dough-like. Then, a preform strip with a diameter of 1.5 mm is extruded using an extruder. The preform strip is then transferred to an oven at 100°C and dried for 3 hours. It is then calcined in an air atmosphere at 450°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt sulfate and manganese sulfate, wherein the mass ratio of cobalt ions in cobalt sulfate to porous support framework is 20:100, and the mass ratio of manganese ions in manganese sulfate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in an air atmosphere at 300°C for 3 hours to obtain a Fischer-Tropsch catalyst with a porous structure.

[0039] Example 5 Step 1: P25 TiO2 carrier powder and polyvinyl alcohol are dry-mixed at a mass ratio of 10:3 to obtain a mixed powder. Then, deionized water is added at a water-to-powder ratio of 2:7 and kneaded until the powder becomes dough-like. Then, a preform strip with a diameter of 1.5 mm is extruded using an extruder. The preform strip is then transferred to an oven at 100°C and dried for 3 hours. It is then calcined in an air atmosphere at 450°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt sulfate and manganese sulfate, wherein the mass ratio of cobalt ions in cobalt sulfate to porous support framework is 20:100, and the mass ratio of manganese ions in manganese sulfate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in an air atmosphere at 300°C for 3 hours to obtain a Fischer-Tropsch catalyst with a porous structure.

[0040] Example 6 Step 1: P25 TiO2 carrier powder and polyvinyl alcohol are dry-mixed at a mass ratio of 10:3 to obtain a mixed powder. Then, deionized water is added at a water-to-powder ratio of 1:7 and kneaded until the powder becomes dough-like. Then, a preform strip with a diameter of 1.5 mm is extruded using an extruder. The preform strip is then transferred to an oven at 100°C and dried for 3 hours. It is then calcined in an air atmosphere at 450°C for 3 hours to obtain a porous carrier skeleton. Step 2: Using an equal-volume impregnation method, the obtained porous support framework is impregnated in a precursor solution containing cobalt sulfate and manganese sulfate, wherein the mass ratio of cobalt ions in cobalt sulfate to porous support framework is 20:100, and the mass ratio of manganese ions in manganese sulfate to porous support framework is 2:100. After impregnation for 8 hours, it is dried at room temperature for 24 hours, and finally calcined in an air atmosphere at 300°C for 3 hours to obtain a Fischer-Tropsch catalyst with a porous structure.

[0041] The aperture ratio of Examples 4-6 Figure 6 As shown, in Example 4, when the water-to-powder ratio was 3:7, the pore size of the inherent pores between TiO2 crystals was 26 nm, accounting for 79.31%. The double peaks with larger pore sizes were pore peaks generated by polyvinyl alcohol pore formation, with pore sizes of 3100 nm and 8500 nm, accounting for 11.50% and 9.19%, respectively. In Example 5, when the water-to-powder ratio was 2:7, the pore size of the inherent pores between TiO2 crystals was 26 nm, accounting for 89.56%. The double peaks with larger pore sizes were generated by polyvinyl alcohol pore formation, with pore sizes of 3100 nm and 8500 nm, accounting for 5.52% and 4.91%, respectively. In Example 6, when the water-to-powder ratio was 1:7, the pore size of the inherent pores between TiO2 crystals was 26 nm, accounting for 94.47%. The double peaks with larger pore sizes were pore peaks generated by polyvinyl alcohol pore formation, with pore sizes of 3100 nm and 8500 nm, accounting for 3.33% and 2.21%, respectively.

[0042] The particle strengths of the Fischer-Tropsch catalysts prepared in Examples 1-6 are shown in Table 2.

[0043] Table 2

[0044] Comparative Example 1 The preparation method of Comparative Example 1 is the same as that of Example 1, except that microcrystalline cellulose is not added during the preparation of the porous support framework, and a non-porous support catalyst is prepared, wherein the support framework contains only pore peaks with an inherent pore size of 40 nm between TiO2 crystals.

[0045] The overall performance of the catalysts prepared in Example 1 and Comparative Example 1 in the Fischer-Tropsch reaction is as follows: Figure 7 As shown, in the temperature range of 180~210℃, the CO conversion rate of the porous catalyst and the non-porous catalyst is basically the same, but the selectivity of methane is significantly reduced. This proves that the prepared porous catalyst effectively increases the mass transfer efficiency in the reaction process, optimizes the diffusion path of reactants and products, and inhibits the generation of methane byproducts.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Fischer-Tropsch catalyst with a porous structure, characterized in that: Includes the following steps: S1. Mix TiO2 carrier powder with pore-forming agent evenly, knead, extrude, dry, and calcine to obtain a porous carrier skeleton. S2. The porous support framework is placed in a precursor solution containing an active metal for equal-volume impregnation, dried, and calcined to obtain the Fischer-Tropsch catalyst, wherein the active metal is selected from at least one of iron, cobalt, and copper.

2. The method for preparing a Fischer-Tropsch catalyst with a porous structure according to claim 1, characterized in that: In step S1, the pore-forming agent is selected from at least one of microcrystalline cellulose, polyvinyl alcohol, urea, polymethyl methacrylate, and hydroxypropyl methylcellulose, wherein the mass ratio of the pore-forming agent to the TiO2 carrier powder is 1:2~10.

3. The method for preparing a Fischer-Tropsch catalyst with a porous structure according to claim 1, characterized in that: The precursor solution also includes an auxiliary metal, wherein the auxiliary metal is selected from at least one of manganese, zirconium, nickel, ruthenium, and potassium.

4. The method for preparing a Fischer-Tropsch catalyst with a porous structure according to claim 3, characterized in that: The mass ratio of the active metal to the porous carrier skeleton is 5~30:100; The mass ratio of the auxiliary metal to the porous carrier skeleton is 1~4:

100.

5. The method for preparing a Fischer-Tropsch catalyst with a porous structure according to claim 1, characterized in that: In step S1, the amount of water used in the kneading process is 10-70% of the mixed powder; The perforated plate particle size in the extrusion molding process is 0.6~3mm; The roasting temperature is 300~700℃ and the time is 3~4h.

6. The method for preparing a Fischer-Tropsch catalyst with a porous structure according to claim 1, characterized in that: The roasting temperature in step S2 is 200~600℃, and the time is 3~4h.

7. A Fischer-Tropsch catalyst with a porous structure obtained by the preparation method according to any one of claims 1 to 6, characterized in that: It includes a TiO2 support and an active metal uniformly loaded on the TiO2 support, wherein the TiO2 support has a mesoporous structure and the active metal is selected from at least one of iron, cobalt, and copper.

8. A Fischer-Tropsch catalyst with a porous structure according to claim 7, characterized in that: The loading of the active metal is 10-30%.

9. A Fischer-Tropsch catalyst with a porous structure according to claim 7, characterized in that: The TiO2 support is further loaded with an auxiliary metal, which is selected from at least one of manganese, zirconium, nickel, ruthenium, and potassium, and the loading amount of the auxiliary metal is 1-2%.

10. The use of a Fischer-Tropsch catalyst with a porous structure obtained by any one of claims 1 to 6, or a Fischer-Tropsch catalyst with a porous structure according to any one of claims 7 to 9, in a Fischer-Tropsch synthesis reaction.

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