Iron-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, and discloses an iron-based catalyst as well as a preparation method and application thereof. The iron-based catalyst contains Fe, Y, M, B, K and SiO2, the weight ratio of Fe to Y to M to B to K to SiO2 is 100: (1-20): (0.1-8): (0.1-10): (0.5-10): (5-40), and M is selected from at least one of Zn, Cr, Mn, Zr and Cu. According to the iron-based catalyst, iron phase transformation stress is inhibited through yttrium (Y), Fe-SiO2 interface bonding is strengthened through boron (B), the CO conversion rate is kept to be larger than or equal to 95% under the condition that the abrasion rate is smaller than or equal to 5%, and the abrasion resistance and catalytic activity are synchronously improved; according to the iron-based catalyst, by optimizing the yttrium-boron ratio and controlling the surface acid-base property, the CO2 selectivity is smaller than or equal to 15%, and CH4 is smaller than or equal to 3%.

Description

Technical Field

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

[0002] Fischer-Tropsch synthesis is a process that converts syngas (mainly composed of carbon monoxide and hydrogen) into liquid fuels and chemicals. Since its discovery in the 1920s, it has been a crucial technology for synthesizing fuels and chemicals. In recent years, with the increasing demand for clean fuels and the decreasing reliance on traditional petroleum resources, Fischer-Tropsch synthesis technology has received wider attention and research. Slurry bed reactors have become the mainstream technology for industrial-scale Fischer-Tropsch synthesis due to their advantages such as high heat transfer efficiency, uniform temperature distribution, and convenient online catalyst replacement. In slurry bed Fischer-Tropsch synthesis, catalyst performance is a key factor affecting reaction efficiency and product distribution. Iron-based catalysts are widely used in Fischer-Tropsch synthesis due to their high activity, good water-gas shift capability, and low cost. However, traditional iron-based catalysts continuously endure gas-liquid-solid three-phase shear forces and particle collisions in the slurry bed, leading to wear and pulverization problems. If the resulting fine catalyst powder is introduced into downstream processes, it can cause poisoning of the hydrocracking catalyst. Therefore, improving the anti-wear performance of the catalyst is an urgent technical problem to be solved.

[0003] Existing technologies mainly improve strength by adding SiO2 binders, but increasing the amount of SiO2 will enhance surface acidity, leading to a decrease in CO conversion rate and an increase in the selectivity of CO2 and CH4. Therefore, this invention provides a wear-resistant iron-based slurry bed Fischer-Tropsch synthesis catalyst and its preparation method: adding yttrium (Y) and other auxiliary elements to the iron-based Fischer-Tropsch synthesis catalyst improves catalytic performance by optimizing the active phase structure, enhancing electron transfer efficiency, and improving anti-carbon deposition ability. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of insufficient anti-wear performance and catalytic activity of existing iron-based catalysts used in Fischer-Tropsch synthesis, and to provide an iron-based catalyst, its preparation method and application. This iron-based catalyst uses yttrium (Y) to suppress the phase transformation stress of iron and boron (B) to strengthen the Fe-SiO2 interface bonding, maintaining a CO conversion rate of ≥95% at an wear rate of ≤5%, and simultaneously improving anti-wear performance and catalytic activity. The iron-based catalyst also optimizes the yttrium-boron ratio and controls the surface acidity and alkalinity, so that the CO2 selectivity is ≤15% and CH4 is ≤3%.

[0005] To achieve the above objectives, the first aspect of the present invention provides an iron-based catalyst containing Fe, Y, M, B, K and SiO2, wherein the weight ratio of Fe:Y:M:B:K:SiO2 is 100:(1~20):(0.1~8):(0.1~10):(0.5~10):(5~40), wherein M is selected from at least one of Zn, Cr, Mn, Zr and Cu.

[0006] Preferably, in the iron-based catalyst, Fe:Y:M:B:K:SiO2 is 100:(2~15):(5~23):(0.5~8):(1~8):(8~30) by weight, and more preferably 100:(4~10):(10~20):(1~5):(2~5):(10~20).

[0007] Preferably, the weight ratio Y:B is 100:(10~50).

[0008] A second aspect of the present invention provides a method for preparing the iron-based catalyst described above, the method comprising the following steps: (1) Mix iron salt, M metal precursor and yttrium salt, then mix the resulting mixture with ammonia water and perform co-precipitation and aging in sequence, separate the solid product and slurry, then add alkaline silica sol, potassium water glass and boric acid solution to the slurry, and perform two-stage calcination after spray drying; (2) The product obtained in step (1) is subjected to hydrogen reduction and syngas activation in sequence.

[0009] Preferably, the iron salt is selected from at least one of ferric nitrate, ferric chloride, and ferric sulfate.

[0010] Preferably, the M metal precursor is selected from at least one of the nitrate, sulfate and chloride salts of copper, chromium, zinc, manganese and zirconium.

[0011] Preferably, the yttrium salt is selected from at least one of yttrium nitrate, yttrium chloride, and yttrium sulfate.

[0012] Preferably, in step (1), the co-precipitation and aging process specifically includes: adding the mixture and the ammonia water to the container in parallel flow and dropwise under the conditions of 30~90℃ and pH value of 7~11, then stirring for 0.2~2h and letting it stand for aging.

[0013] Preferably, the concentration of the mixture, calculated as anion, is 0.25~3 mol / L.

[0014] Preferably, the concentration of the ammonia water is 5wt% to 10wt%.

[0015] Preferably, the aging conditions include a temperature of 30~90℃ and a time of 0.5~10h.

[0016] Preferably, step (1) further includes: adding alkaline silica sol, potassium silicate and boric acid solution to the slurry, emulsifying and dispersing it at 50~90°C, and then adjusting the solid content of the slurry to 15wt%~50wt%.

[0017] Preferably, in the potassium silicate, the mass ratio of potassium oxide to silicon dioxide is 0.2 to 2:1.

[0018] Preferably, the concentration of the boric acid solution is 1wt% to 10wt%.

[0019] Preferably, in step (1), the inlet temperature of the spray dryer is 200~400℃ and the outlet temperature is 100~200℃.

[0020] Preferably, in step (1), the conditions for the first stage of roasting include: a temperature of 200~500℃ and a time of 1~5h.

[0021] Preferably, the conditions for the two-stage roasting include: a temperature of 500~800℃ and a time of 1~10h.

[0022] Preferably, in step (2), the conditions for hydrogen reduction include: a temperature of 200~300℃, a time of 10~24h, and a hydrogen space velocity of 1000~3000h. -1 .

[0023] Preferably, the conditions for syngas activation include: a temperature of 200-300°C, a time of 10-24 hours, and a syngas space velocity of 1000-3000 h⁻¹. -1 .

[0024] Preferably, in the synthesis gas, the volume ratio of hydrogen to carbon monoxide is 0.5 to 2:1.

[0025] A third aspect of the present invention provides the application of the iron-based catalyst described above in Fischer-Tropsch synthesis.

[0026] The iron-based catalyst, its preparation method, and its application described in this invention have at least the following advantages compared to existing technologies: 1. Simultaneously improve wear resistance and catalytic activity: By suppressing the phase transformation stress of iron through yttrium (Y) and strengthening the Fe-SiO2 interface bonding with boron (B), the CO conversion rate is maintained at ≥95% under a wear rate ≤5%.

[0027] 2. Suppress byproduct formation: Optimize the yttrium-boron ratio and control the surface acidity and alkalinity to achieve CO2 selectivity ≤15% and CH4 selectivity ≤3%.

[0028] 3. Simplify the preparation process: Develop a stepwise precipitation-in-situ emulsification method to avoid the complex process of coated catalysts and shorten the synthesis cycle to ≤24h. Attached Figure Description

[0029] Figure 1 The N2 adsorption-desorption curves and pore size distribution of the Fischer-Tropsch catalyst are shown. Detailed Implementation

[0030] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] The iron-based catalyst of the present invention contains Fe, Y, M, B, K and SiO2, and the weight ratio of Fe:Y:M:B:K:SiO2 is 100:(1~20):(0.1~8):(0.1~10):(0.5~10):(5~40), wherein M is selected from at least one of Zn, Cr, Mn, Zr and Cu. Preferably, in the iron-based catalyst, the weight ratio of Fe:Y:M:B:K:SiO2 is 100:(2~15):(5~23):(0.5~8):(1~8):(8~30), more preferably 100:(4~10):(10~20):(1~5):(2~5):(10~20). In the present invention, when the weight ratio of each component in the iron-based catalyst is within the above range (especially the preferred range), the catalytic activity of the iron-based catalyst is more excellent.

[0033] In this invention, before activation, the metal components of the iron-based catalyst exist in the form of oxides, and boron exists in the form of boric acid; after activation, the iron-based catalyst exists in the form of elemental iron and iron carbide phase, while potassium, yttrium, and M exist in the form of oxides, and boron exists in the form of boron oxide.

[0034] In this invention, Fe is the main active component, and the electronic additive yttrium (Y) enhances CO dissociation by enriching electrons into iron d orbitals. Boron (B) forms an Fe-B alloy phase, improving α-olefin selectivity. Y can form a synergistic system with B. Yttrium (Y) suppresses iron phase transformation stress, while boron (B) strengthens the Fe-SiO2 interface bonding, reducing wear rate to 5% and further reducing CH4 selectivity. CO conversion rate is ≥95%, YFeO3 promotes active phase dispersion, and B optimizes pore unobstructedness, increasing active site utilization by 30%.

[0035] Furthermore, in this invention, Y 3+ Preferentially adsorbed at lattice defect sites in Fe(OH)3, it suppresses lattice distortion during subsequent reduction, modulates the surface electronic states by changing the electron cloud density of the active sites, and simultaneously inhibits the methanation pathway while promoting carbon chain growth (increased α value). Experiments show that when Y is introduced into the catalyst, CO2 selectivity ≤15%, CH4 selectivity ≤3%, and C5 selectivity ≤15%. + Selectivity increased to 80%.

[0036] The addition of yttrium can also inhibit the sintering of active components in high-temperature reactions. In the spray drying preparation process, the yttrium-modified catalyst still maintains a high specific surface area (155–174 m² / g) after calcination at 610℃, and the pore distribution is uniform (pore size 12–16 nm), which significantly improves mechanical strength and resistance to carbon deposition.

[0037] In this invention, the weight ratio of Y:B is 100:(10~50), preferably 100:(20~40). In this invention, by optimizing the yttrium-boron ratio and controlling the surface acidity / alkalinity, CO2 selectivity ≤15% and CH4 selectivity ≤3% can be achieved.

[0038] The preparation method of the iron-based catalyst of the present invention includes the following steps: (1) Mix iron salt, M metal precursor and yttrium salt, then mix the resulting mixture with ammonia water and perform co-precipitation and aging in sequence, separate the solid product and slurry, then add alkaline silica sol, potassium water glass and boric acid solution to the slurry, and perform two-stage calcination after spray drying; (2) The product obtained in step (1) is subjected to hydrogen reduction and syngas activation in sequence.

[0039] In this invention, the iron salt can be at least one of ferric nitrate, ferric chloride, and ferric sulfate.

[0040] In this invention, the M metal precursor can be at least one of the nitrate, sulfate and chloride salts of copper, chromium, zinc, manganese and zirconium.

[0041] In this invention, the yttrium salt may be at least one of yttrium nitrate, yttrium chloride, and yttrium sulfate.

[0042] In some embodiments, the co-precipitation and aging process in step (1) may specifically include: adding the mixture and ammonia water dropwise into a container in parallel flow at 30-90°C and pH 7-11, followed by stirring for 0.2-2 hours and then allowing it to stand for aging. When performing the co-precipitation and aging according to this embodiment, the complex process of coated catalysts can be effectively avoided, the synthesis cycle can be shortened to ≤24 hours, and the highly uniform mixing and tight binding of the active metal (iron) and structural aids (yttrium, boron, etc.) at the atomic / nanoscale can be ensured, thereby constructing strongly interacting active sites, ultimately enabling the catalyst to exhibit high activity and excellent product selectivity in the Fischer-Tropsch synthesis reaction.

[0043] In a preferred embodiment, the concentration of the mixture, expressed as anion, is 0.25~3 mol / L. In this invention, when the concentration of the mixture, expressed as anion, is within the above range, the nucleation and growth rates during the precipitation process can be precisely controlled, thereby effectively regulating the particle size, morphology, and uniformity of the catalyst precursor's distribution. This avoids component segregation and particle agglomeration caused by localized supersaturation, ultimately obtaining a catalyst with high specific surface area and ideal pore structure, providing structural assurance for its high reactivity.

[0044] In a preferred embodiment, the concentration of the ammonia solution is 5 wt% to 10 wt%. In this invention, when the concentration of the ammonia solution is within the above range, precise and stable control of the pH value during the precipitation process can be achieved, ensuring that metal ions slowly and synchronously form structurally uniform hydroxide or basic salt precursors, while effectively suppressing excessive ammonia volatilization, thus guaranteeing experimental repeatability and catalyst stability.

[0045] In a preferred embodiment, the aging conditions include a temperature of 30~90℃ and a time of 0.5~10h.

[0046] In some embodiments, step (1) further includes: adding alkaline silica sol, potassium silicate, and boric acid solution to the slurry, emulsifying and dispersing it at 50-90°C, and then adjusting the solid content of the slurry to 15wt%-50wt%. When the emulsification and dispersion is carried out according to this embodiment, the complex process of coated catalysts can be effectively avoided, the synthesis cycle can be shortened to ≤24h, and the active components, structural aids, and binders (silica sol, potassium silicate) can be highly homogenized at the nanoscale, thereby forming robust, regular microsphere catalyst particles with ideal channels in the subsequent spray drying, significantly improving their mechanical strength and reaction stability.

[0047] In a preferred embodiment, the mass ratio of potassium oxide to silicon dioxide in the potassium silicate is 0.2 to 2:1.

[0048] In a preferred embodiment, the concentration of the boric acid solution is 1wt% to 10wt%.

[0049] In the method described in this invention, in step (1), the inlet temperature of the spray dryer can be 200~400℃ and the outlet temperature can be 100~200℃.

[0050] In the method described in this invention, in step (1), the conditions for the first stage of roasting include: a temperature of 200~500℃ and a time of 1~5h.

[0051] In the method described in this invention, the conditions for two-stage calcination include: a temperature of 500~800℃ and a time of 1~10h.

[0052] In the method described in this invention, the conditions for hydrogen reduction in step (2) include: a temperature of 200~300℃, a time of 10~24h, and a hydrogen space velocity of 1000~3000h. -1 .

[0053] In the method described in this invention, the conditions for syngas activation include: a temperature of 200-300°C, a time of 10-24 h, and a syngas space velocity of 1000-3000 h⁻¹. -1 .

[0054] In a preferred embodiment, the volume ratio of hydrogen to carbon monoxide in the synthesis gas is 0.5 to 2:1.

[0055] The iron-based catalyst described in this invention can be used in Fischer-Tropsch synthesis to maintain a CO conversion rate of ≥95% with a wear rate of ≤5%, and a CO2 selectivity of ≤15% and a CH4 selectivity of ≤3%.

[0056] The following examples further illustrate the iron-based catalyst, its preparation method, and its application according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0057] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods in the art.

[0058] Unless otherwise specified, all experimental materials used in the following examples are commercially available.

[0059] Example 1 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:4.16:1.07:0.56:2:16.25, and Y:B = 100:13.46. The specific preparation process is as follows: A mixed solution was prepared by mixing 40g Fe(NO3)3·9H2O, 4g Cu(NO3)2·3H2O, 1g Y(NO3)3·6H2O, and 1000mL of water. At 40℃, the metal nitrate mixture was slowly added dropwise with 7wt% ammonia solution while continuously stirring to achieve co-precipitation, maintaining pH=7 throughout the process. After co-precipitation, the temperature was kept constant and stirring continued for 0.5h, followed by aging and settling for 1h. After aging, the precipitate slurry was filtered, and the resulting filter cake was pulped. 4.16g alkaline silica sol (SiO2 content 30wt%), 3.94g potassium silicate (K2O / SiO2=0.3), and 11.42g 3wt% boric acid solution were added sequentially to the slurry, and the mixture was emulsified and dispersed at 70℃. Next, the solid content of the slurry was adjusted to 15 wt%, and spray-dried at an inlet temperature of 300℃ and an outlet temperature of 150℃. Then, it was calcined in two stages: calcined at 350℃ for 2 hours to remove the water of crystallization, and then calcined at 610℃ for 3 hours. The iron-based catalyst obtained was denoted as FT-1.

[0060] Example 2 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:6.26:1.58:1.08:2:16.25, and Y:B = 100:17.25. The specific preparation process is as follows: A mixed solution was prepared by mixing 40g Fe(NO3)3·9H2O, 6g Cu(NO3)2·3H2O, 1.5g Y(NO3)3·6H2O, and 1000mL of water. At 50℃, the metal nitrate mixture was slowly added dropwise with 7wt% ammonia solution while continuously stirring to achieve co-precipitation, maintaining the pH at 8 throughout the process. After co-precipitation, the temperature was kept constant and stirring continued for 0.5h, followed by aging and settling for 1h. After aging, the precipitate was filtered, and the resulting filter cake was pulped. 4.16g alkaline silica sol (SiO2 content 30wt%), 3.94g potassium silicate (K2O / SiO2=0.3), and 20.61g 3wt% boric acid solution were added sequentially to the pulp, and the mixture was emulsified and dispersed at 70℃. Next, the solid content of the slurry was adjusted to 15 wt%, and spray-dried at an inlet temperature of 300℃ and an outlet temperature of 150℃. Then, it was calcined in two stages: calcined at 350℃ for 2 hours to remove the water of crystallization, and then calcined at 610℃ for 3 hours. The iron-based catalyst obtained was denoted as FT-2.

[0061] Example 3 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:8.34:2.12:1.62:2:11.24, and Y:B = 100:19.42. The specific preparation process is as follows: A mixed solution was prepared by mixing 40g Fe(NO3)3·9H2O, 8g Cu(NO3)2·3H2O, 2g Y(NO3)3·6H2O, and 1000mL of water. At 60℃, the metal nitrate mixture was slowly added dropwise with 7wt% ammonia solution while continuously stirring to achieve co-precipitation, maintaining pH=8 throughout the process. After co-precipitation, the temperature was kept constant and stirring continued for 0.5h, followed by aging and settling for 1h. After aging, the precipitate was filtered, and the resulting filter cake was pulped. 4.16g alkaline silica sol (SiO2 content 30wt%), 3.94g potassium silicate (K2O / SiO2=0.2), and 30.915g 3wt% boric acid solution were added sequentially to the pulp, and the mixture was emulsified and dispersed at 70℃. Next, the solid content of the slurry was adjusted to 20 wt%, and spray-dried at an inlet temperature of 300℃ and an outlet temperature of 150℃. Then, it was calcined in two stages: calcined at 350℃ for 2 hours to remove water of crystallization, and then calcined at 610℃ for 3 hours. The iron-based catalyst obtained was denoted as FT-3.

[0062] Example 4 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:10.42:2.12:2.71:2:11.24, and the ratio of Y:B is 100:26.01. The specific preparation process is as follows: A mixed solution was prepared by mixing 40g Fe(NO3)3·9H2O, 8g Cu(NO3)2·3H2O, 2.5g Y(NO3)3·6H2O, and 1000mL of water. At 70℃, the metal nitrate mixture was slowly added dropwise with 7wt% ammonia solution while continuously stirring to achieve co-precipitation, maintaining pH=9 throughout the process. After co-precipitation, the temperature was kept constant and stirring continued for 0.5h, followed by aging and settling for 1h. After aging, the precipitate was filtered, and the resulting filter cake was pulped. 4.16g alkaline silica sol (SiO2 content 30wt%), 3.94g potassium silicate (K2O / SiO2=0.2), and 51.525g 3wt% boric acid solution were added sequentially to the pulp, and the mixture was emulsified and dispersed at 70℃. Next, the solid content of the slurry was adjusted to 20 wt%, and spray-dried at an inlet temperature of 300℃ and an outlet temperature of 150℃. Then, it was calcined in two stages: calcined at 350℃ for 2 hours to remove the water of crystallization, and then calcined at 610℃ for 3 hours. The iron-based catalyst obtained was denoted as FT-4.

[0063] Example 5 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:1:1:0.1:0.5:1.74, and Y:B = 100:10. The specific preparation process is as follows: This embodiment was carried out according to the method described in Example 1, except that the amount of Cu(NO3)2·3H2O was 0.21g, the amount of Y(NO3)3·6H2O was 0.24g, the amount of potassium silicate (K2O / SiO2=0.3) was 0.11g, the amount of 3wt% boric acid solution was 1.07g, and the amount of alkaline silica sol (SiO2 content 30wt%) was 4.16g. The final iron-based catalyst obtained is designated as FT-5.

[0064] Example 6 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:20:2.12:10:10:17.91, and Y:B = 100:50. The specific preparation process is as follows: This embodiment was carried out according to the method described in Example 1, except that the amount of Y(NO3)3·6H2O was 4.8g, the amount of potassium silicate (K2O / SiO2=0.3) was 2.24g, the amount of 3wt% boric acid solution was 106.7g, and the amount of alkaline silica sol (SiO2 content 30wt%) was 4.16g. The final iron-based catalyst obtained is designated as FT-6.

[0065] Example 7 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:1:12.12:10:2:16.25, and Y:B = 1:10. The specific preparation process is as follows: This embodiment was carried out according to the method described in Example 1, except that the amount of Y(NO3)3·6H2O used was 0.24 g, and the amount of 3wt% boric acid solution used was 106.7 g. The iron-based catalyst finally obtained is designated as FT-7.

[0066] Example 8 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:20:2.12:0.5:2:16.25, and Y:B = 100:2.5. The specific preparation process is as follows: This embodiment was carried out according to the method described in Example 1, except that the amount of Y(NO3)3·6H2O was 4.8g and the amount of 3wt% boric acid solution was 1.07g. The final iron-based catalyst obtained is designated as FT-8.

[0067] Example 9 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:4.16:0.74:0.56:2:16.25, and Y:B = 100:13.46. The specific preparation process is as follows: This embodiment was carried out according to the method described in Example 1, except that the amount of water used was 100 mL and the concentration of ammonia was 15 wt%. The final iron-based catalyst obtained was designated as FT-9.

[0068] Example 10 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:4.16:1.03:0.22:2:16.25, and Y:B = 100:5.29. The specific preparation process is as follows: This embodiment is carried out according to the method described in Example 1, except that the amount of water used is 1500 mL and the concentration of ammonia is 1 wt%. The iron-based catalyst obtained is designated as FT-10.

[0069] Example 11 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:4.16:1.07:0.56:2:16.25, and Y:B = 100:13.46. The specific preparation process is as follows: This embodiment follows the method described in Example 1, except that alkaline silica sol, potassium silicate, and boric acid solution are simultaneously added to the slurry. The resulting iron-based catalyst is designated FT-11.

[0070] Comparative Example 1 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:0.5:0.5:0.05:0.25:1, and Y:B = 100:10. The specific preparation process is as follows: This comparative example was conducted according to the method described in Comparative Example 1, except that the amounts of Cu(NO3)2·3H2O were 0.16 g, Y(NO3)3·6H2O were 0.12 g, potassium silicate (K2O / SiO2=0.3) were 0.055 g, 3wt% boric acid solution was 0.504 g, and alkaline silica sol (SiO2 content 30wt%) was 0.194 g. The resulting iron-based catalyst was designated D-FT-1.

[0071] Comparative Example 2 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Y:Cu:B:K:SiO2 is 100:25:26.49:13.39:14.06:25, and Y:B = 100:50. The specific preparation process is as follows: This comparative example was conducted according to the method described in Comparative Example 1, except that the amount of Cu(NO3)2·3H2O used was 10g, the amount of Y(NO3)3·6H2O used was 6g, the amount of potassium silicate (K2O / SiO2=0.3) used was 3g, the amount of 3wt% boric acid solution used was 150g, and the amount of alkaline silica sol (SiO2 content of 30wt%) used was 5.22g. The final iron-based catalyst obtained was designated as D-FT-2.

[0072] Comparative Example 3 In the iron-based catalyst prepared in this embodiment, the weight ratio of Fe:Cu:B:K:SiO2 is 100:1.07:0.56:2:16.25, and Y:B = 0. The specific preparation process is as follows: This comparative example was carried out according to the method described in Example 1, except that Y(NO3)3·6H2O was not added. The final iron-based catalyst was designated D-FT-3.

[0073] Test Example 1 This test example characterizes the physicochemical properties of the iron-based catalysts prepared in Examples 1-11 and Comparative Examples 1-3. The wear rate was specifically tested using a catalyst powder wear index tester from Beijing Zhongyi Lilang Technology Co., Ltd. The testing process conforms to the American ASTM D5757 standard.

[0074] Specific surface area and pore volume were obtained by nitrogen adsorption (BEL sorp-max fully automated specific surface area and pore volume analyzer). The specific test procedures were in accordance with GB / T 19587-2017 (specific surface area) and GB / T 21650.2-2008 (mesoporous analysis). The elemental composition and content (Y₂O₃) were determined using a Bruker X-ray fluorescence spectrometer (XRF) from Germany, with specific testing procedures following GB / T 30905-2014, "Determination of Elemental Content in Inorganic Chemical Products by X-ray Fluorescence Spectrometry". However, the upper limit for XRF detection is oxygen (element 8), and boron (element 5) in the catalyst exceeds the detection range. Therefore, the content of B₂O₃ was determined using inductively coupled plasma atomic emission spectrometry (ICP), with specific testing procedures following national standards GB / T 23374-2009 and GB / T 24520-2009.

[0075] The results are as follows Figure 1 As shown in Table 1.

[0076] Table 1

[0077] As shown in Table 1, by adopting the technical solution described in this invention, the iron-based catalysts prepared in Examples 1-11 all have a specific surface area of ​​over 144.6 m² / g, a pore volume of over 0.701 g / cm³, and a wear rate of less than 7.08%. Furthermore, in preferred Examples 1-4, the specific surface area of ​​the iron-based catalysts is all over 155.3 m² / g. 2 The pore volume is above / g and is generally 0.747g / cm³. 3 The wear rates of the above examples are all below 4.93%; however, the specific surface area and pore volume of comparative examples 1-3 all decreased, and the wear rates increased to some extent.

[0078] Test Example 2 This test example tests the activity of the iron-based catalysts prepared in Examples 1-11 and Comparative Examples 1-3. The specific test steps include: I. Catalyst Reduction (Activation) Iron-based Fischer-Tropsch synthesis catalysts are typically reduced in syngas (H2 + CO), and the main steps are as follows: 1. Catalyst loading Clean the inner wall of the reactor with alcohol, add 5g of catalyst, then pour in 600ml of liquid paraffin, place a graphite sealing ring on top, and seal the reactor.

[0079] 2. System replacement High-purity inert gas N2 is used to purge the reactor at a high space velocity for about 30-60 minutes to remove air (O2) and moisture from the reaction pipeline and reactor, preventing the catalyst from being accidentally oxidized or sintered during the reduction process.

[0080] 3. Nitrogen pressurization and airtightness: Nitrogen gas is used to pressurize the device in stages, with test pressure levels of 1.0 MPa, 2.0 MPa, and 3.0 MPa. Each time the system is completely filled with gas and the set pressure is reached, all valves are closed to ensure the system inlet and outlet are completely shut off. Observation and leak detection are then performed, and the pressure is maintained for 12 hours. If the pressure drop is ≤2% after 12 hours, the airtightness meets the standard. If any leaks are found, the pressure is released and tightened. Only after confirming there are no leaks can the pressure be increased to the next level.

[0081] 4. Hydrogen pressurization and airtightness Hydrogen is introduced into the system at a certain rate, and the system pressure is increased in test pressure levels of 1.0 MPa, 2.0 MPa, and 3.0 MPa. After each pressure level is reached, the pressure increase must be paused, all valves must be closed, and the system inlet and outlet must be completely closed for observation and leak detection. During the observation period, a combustible gas detector is used to check for leaks in the joints, valves, and reactor seals of the device. If any leaks are found, the pressure must be released and the leaks tightened. Only after confirming that there are no leaks can the pressure be increased to the next level.

[0082] 5. Catalyst reduction The system pressure was set to 3.0 MPa. The H2 and CO flow rates were set according to the reduction conditions. Once the feed gas flow rate and unit pressure were stable, the composition of the tail gas was analyzed using chromatography, the H2 / CO ratio was calculated, and the data was recorded. When the H2 / CO ratio of three consecutive sets of tail gases reached 50 ± 0.5, the heating system was activated to initiate the catalyst reduction reaction, and the furnace temperature was increased according to the program set in Table 2.

[0083] Table 2 Heating Procedure

[0084] When the liquid phase temperature in the reactor reaches the target temperature, it is recorded as the reduction point 0. The reduction process lasts for 24 hours. During the process, experimental data must be recorded. As required, data such as flow rate, pressure, and tail gas are recorded every two hours, and the composition of the tail gas is analyzed every two hours. After the reduction process is completed, the liquid phase temperature is manually raised to the reaction temperature of 270℃ to prepare for the reaction.

[0085] 6. Catalyst evaluation test Adjust the H2 flow rate to the required evaluation conditions, then adjust the CO flow rate to the target value in three stages, stabilizing each stage for 2 hours. Slowly control the reactor temperature and pressure to the reaction conditions required in Table 2, and record this as the reaction point 0. During the reaction, experimental data must be recorded, including flow rate, pressure, and tail gas data every two hours, and the tail gas composition analyzed every two hours. The evaluation conditions for the Fischer-Tropsch slurry bed evaluation device system are shown in Table 3 below.

[0086] Table 3 Evaluation Scheme for Slurry Bed Catalysts

[0087] The results are shown in Table 4.

[0088] Table 4

[0089] As shown in Table 4, by adopting the technical solution described in this invention, the iron-based catalysts prepared in Examples 1-11 can all achieve excellent CO conversion and C5 concentration. +Selectivity, especially in preferred embodiments 1-4, shows that the CO conversion rate all reached over 95.54%, C5 + The selectivity was higher than 78.61%, which was much better than the iron-based catalysts prepared in comparative examples 1-3.

[0090] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An iron-based catalyst, characterized in that, The iron-based catalyst contains Fe, Y, M, B, K and SiO2, and the weight ratio of Fe:Y:M:B:K:SiO2 is 100:(1~20):(0.1~8):(0.1~10):(0.5~10):(5~40), wherein M is selected from at least one of Zn, Cr, Mn, Zr and Cu.

2. The iron-based catalyst according to claim 1, characterized in that, In the iron-based catalyst, the weight ratio of Fe:Y:M:B:K:SiO2 is 100:(2~15):(5~23):(0.5~8):(1~8):(8~30), preferably 100:(4~10):(10~20):(1~5):(2~5):(10~20); Preferably, the weight ratio Y:B is 100:(10~50).

3. A method for preparing the iron-based catalyst according to claim 1 or 2, characterized in that, The method includes the following steps: (1) Mix iron salt, M metal precursor and yttrium salt, then mix the resulting mixture with ammonia water and perform co-precipitation and aging in sequence, separate the solid product and slurry, then add alkaline silica sol, potassium water glass and boric acid solution to the slurry, and perform two-stage calcination after spray drying; (2) The product obtained in step (1) is subjected to hydrogen reduction and syngas activation in sequence.

4. The method according to claim 3, characterized in that, The iron salt is selected from at least one of ferric nitrate, ferric chloride, and ferric sulfate; and / or, The M metal precursor is selected from at least one of the nitrate, sulfate, and chloride salts of copper, chromium, zinc, manganese, and zirconium; and / or, The yttrium salt is selected from at least one of yttrium nitrate and yttrium chloride.

5. The method according to claim 3 or 4, characterized in that, In step (1), the co-precipitation and aging process specifically includes: adding the mixture and the ammonia water to the container in parallel flow and dropwise under the conditions of 30~90℃ and pH value of 7~11, then stirring for 0.2~2h and letting it stand for aging; Preferably, the concentration of the mixture, calculated as anion, is 0.25~3 mol / L; Preferably, the concentration of the ammonia water is 5wt%~10wt%; Preferably, the aging conditions include a temperature of 30~90℃ and a time of 0.5~10h.

6. The method according to claim 3, characterized in that, Step (1) also includes: adding alkaline silica sol, potassium silicate and boric acid solution to the slurry, emulsifying and dispersing it at 50~90℃, and then adjusting the solid content of the slurry to 15wt%~50wt%; Preferably, in the potassium silicate, the mass ratio of potassium oxide to silicon dioxide is 0.2 to 2:1; Preferably, the concentration of the boric acid solution is 1wt% to 10wt%.

7. The method according to claim 3, characterized in that, In step (1), the inlet temperature of the spray dryer is 200~400℃ and the outlet temperature is 100~200℃.

8. The method according to claim 3, characterized in that, In step (1), the conditions for the first stage of roasting include: a temperature of 200~500℃ and a time of 1~5h; and / or, The conditions for the second-stage roasting include: a temperature of 500~800℃ and a time of 1~10h.

9. The method according to claim 3, characterized in that, In step (2), the conditions for hydrogen reduction include: a temperature of 200~300℃, a time of 10~24h, and a hydrogen space velocity of 1000~3000h. -1 ; and / or, The conditions for syngas activation include: a temperature of 200-300℃, a time of 10-24 h, and a syngas space velocity of 1000-3000 h⁻¹. -1 ; Preferably, in the synthesis gas, the volume ratio of hydrogen to carbon monoxide is 0.5 to 2:

1.

10. The use of the iron-based catalyst according to claim 1 or 2 in Fischer-Tropsch synthesis.

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