Method for preparing iron-based Fischer-Tropsch synthesis catalyst with low CO2 selectivity, catalyst and application

Abstract

The invention provides a method for preparing an iron-based Fischer-Tropsch synthesis catalyst with low CO2 selectivity, the iron-based Fischer-Tropsch synthesis catalyst prepared by the method, and application of the iron-based Fischer-Tropsch synthesis catalyst in reduction of CO2 selectivity in a Fischer-Tropsch synthesis reaction. According to the iron-based Fischer-Tropsch synthesis catalyst, the CO2 selectivity in Fischer-Tropsch synthesis reaction is reduced, and meanwhile, high Fischer-Tropsch synthesis reaction activity and low CH4 selectivity are maintained.

Description

Technical Field

[0001] The present invention belongs to the field of Fischer-Tropsch synthesis catalysts, and more particularly, relates to a method for preparing an iron-based Fischer-Tropsch synthesis catalyst with low CO 2 selectivity, a catalyst prepared thereby, and its use. Background Art

[0002] The Fischer-Tropsch synthesis (FTS) reaction can convert carbon-containing resources such as coal into clean fuels and high-value-added chemicals, which is an important way to alleviate the shortage of oil products in China, ensure national energy strategic security, and realize the efficient utilization of coal resources. The key to Fischer-Tropsch synthesis technology is the development of efficient catalysts. Currently, the main active metals of Fischer-Tropsch synthesis catalysts can be divided into Fe, Co, Ru, etc. Among them, Fe-based catalysts are widely used due to their low price, adjustable product distribution, relatively high toxicity resistance, and other characteristics.

[0003] CO 2 As one of the main by-products of Fe-based Fischer-Tropsch synthesis catalysts, its formation not only reduces the utilization efficiency of syngas, but also increases the load of the tail gas decarbonization device and the recycle compressor, increases energy consumption, and reduces the overall energy conversion efficiency. To solve the problem of high CO 2 selectivity of Fe-based Fischer-Tropsch synthesis catalysts, researchers have proposed various solutions. For example, Patent Application CN202110536316.2 uses a MOF material as a precursor to construct an iron-based catalyst with a carbon hydrophobic layer, and reduces the formation of CO 2 by reducing the contact between water and the active phase. Patent Application CN202310117945.0 performs fluorosilane hydrophobic modification on the carrier SiO 2 of the supported iron-based catalyst to inhibit the adsorption of H 2 O on the catalyst surface and reduce the occurrence of the WGS (water-gas shift) reaction. Patent Application CN202010081671.0 reports a catalyst composed of graphene, additives, and iron oxide microspheres obtained by a hydrothermal method, and reduces the CO 5 C 2 content during the reaction process and increases the Fe 2.2 C content to reduce CO 2 selectivity. In the above methods, the preparation process of the related catalysts is complex, the reagents used are expensive, not suitable for industrial scale-up, and there is a problem that the degree of CO 2 selectivity reduction is limited (20-25 mol%), and in addition, when the CO 2 selectivity is reduced, there is also a problem of a decrease in catalyst activity.

[0004] Therefore, there is still a need in the art to improve iron-based Fischer-Tropsch synthesis catalysts to reduce CO 2 selectivity while maintaining the activity of the catalyst. SUMMARY OF THE INVENTION

[0005] To solve the above problems of the prior art, the inventors found through theoretical analysis and a large number of experiments that by means of a hydrothermal reaction during the preparation of an iron-based Fischer-Tropsch synthesis catalyst and adding specific doping elements, the crystal structure of the active phase Fe 3 O 4 in the WGS reaction can be regulated, and a significant reduction in CO 2 selectivity can be achieved while maintaining the high activity of the iron-based Fischer-Tropsch synthesis catalyst.

[0006] Based on the above research, the inventors provided an iron-based catalyst capable of reducing CO 2 selectivity in the Fischer-Tropsch synthesis reaction and a preparation method thereof. Compared with the prior art, the catalyst prepared by the method of the present invention can fundamentally and significantly reduce CO 3 O 4 selectivity while maintaining high activity in the Fischer-Tropsch synthesis reaction due to the change in the structure of the active phase - Fe 2 in the WGS reaction. In addition, the catalyst preparation method provided by the present invention is simple and easy to scale up for industrial production.

[0007] The first aspect of the present invention provides a method for preparing an iron-based Fischer-Tropsch synthesis catalyst with low CO 2 selectivity, comprising:

[0008] (1) Mixing a soluble iron salt solution with a precursor solution of a structure promoter A and optionally a precursor solution of a support promoter B to obtain a mixed solution;

[0009] (2) Mixing the mixed solution obtained in step (1) with a precipitant, and subjecting the resulting reaction system to a precipitation reaction under stirring to obtain a precipitate slurry I;

[0010] (3) Adding a precursor solution of a doping element C to the slurry I obtained in step (2) under stirring to obtain a mixed slurry II, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr, and B;

[0011] (4) Transferring the slurry II obtained in step (3) into a hydrothermal reaction kettle, and carrying out a hydrothermal reaction at 100°C to 250°C for 5 h to 30 h under stirring and in a closed state, and cooling to room temperature to obtain a precipitate slurry III;

[0012] (5) Washing and pressure-filtering the slurry III obtained in step (4) to obtain a filter cake;

[0013] (6) Add water to the filter cake and stir into a paste, and then carry out emulsification. During the emulsification process, add the precursor solution of electronic additive D and continue emulsification to obtain a catalyst precursor;

[0014] (7) Spray-dry the catalyst precursor to obtain a microsphere-shaped fresh catalyst;

[0015] (8) Calcinate the microsphere-shaped fresh catalyst to obtain an iron-based Fischer-Tropsch synthesis catalyst in an oxidized state.

[0016] The second aspect of the present invention provides a low CO 2 selectivity iron-based Fischer-Tropsch synthesis catalyst prepared by the above method, which contains main active element Fe, structural promoter A, support promoter B, electronic additive D and doping element C. Among them, the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr and B. By mass ratio, Fe:A:B:C:D = 100:(1-50):(0-30):(0.1-10):(0.5-15), where A and B are not both 0 at the same time.

[0017] The third aspect of the present invention provides the use of the above iron-based Fischer-Tropsch synthesis catalyst in reducing the CO 2 selectivity in the Fischer-Tropsch synthesis reaction.

[0018] The inventor of the present invention found that during the preparation process of the iron-based Fischer-Tropsch synthesis catalyst, through the hydrothermal reaction of slurry II, the synergistic effect of the hydrothermal reaction and the addition of doping elements can make the obtained catalyst have an obvious change in the structure of Fe 3 O 4 in the catalyst after reduction pretreatment when it is subsequently used in the Fischer-Tropsch synthesis reaction (the octahedral site Fe decreases, while the tetrahedral site Fe increases), thereby reducing the CO 2 selectivity in the Fischer-Tropsch synthesis reaction catalyzed by this catalyst.

[0019] The iron-based Fischer-Tropsch synthesis catalyst and its preparation method provided by the present invention have the following advantages, but are not limited to this:

[0020] (1) Different from the prior art, the catalyst preparation method of the present invention combines the hydrothermal reaction and the operation of introducing doping elements, which can make the microstructure of Fe 3 O 4 in the catalyst after pretreatment activation change when the obtained catalyst is subsequently used in the Fischer-Tropsch synthesis reaction, so that the tetrahedral site (A site) Fe increases and the octahedral site Fe (B site) decreases, thereby inhibiting the WGS reaction activity and reducing the CO 2Selectivity.

[0021] (2) The catalyst of the present invention can have high Fischer-Tropsch synthesis activity and low CH 2 selectivity while reducing CO 4 selectivity.

[0022] (3) The materials used in the preparation method of the present invention are easy to obtain, the preparation method is simple and the conditions are mild, which is suitable for large-scale industrial catalyst preparation. Detailed Embodiments

[0023] Next, the present invention will be described in detail through the following embodiments. However, the protection scope of the present invention is not limited thereto, but is defined by the appended claims and their equivalents.

[0024] Unless otherwise specified, the term "room temperature" used herein refers to a temperature in the range of 18 °C to 40 °C.

[0025] In some embodiments, the present invention provides a method for preparing an iron-based Fischer-Tropsch synthesis catalyst with low CO 2 selectivity, comprising:

[0026] (1) Mixing a soluble salt solution of iron with a precursor solution of a structural promoter A and an optional precursor solution of a support promoter B to obtain a mixed solution;

[0027] (2) Mixing the mixed solution obtained in step (1) with a precipitant, and causing the resulting reaction system to undergo a precipitation reaction under stirring to obtain a precipitate slurry I;

[0028] (3) Adding a precursor solution of a doping element C to the slurry I obtained in step (2) under stirring to obtain a mixed slurry II, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr, and B;

[0029] (4) Transferring the slurry II obtained in step (3) into a hydrothermal reaction kettle, and carrying out hydrothermal reaction at 100 °C to 250 °C for 5 h to 30 h under stirring and closed state, and cooling to room temperature to obtain a precipitate slurry III;

[0030] (5) Washing and pressure filtering the slurry III obtained in step (4) to obtain a filter cake;

[0031] (6) Adding water to the filter cake and stirring into a paste, and then emulsifying, adding a precursor solution of an electronic promoter D during the emulsification process, and continuing to emulsify to obtain a catalyst precursor;

[0032] (7) Spray drying the catalyst precursor to obtain a microsphere-shaped fresh catalyst;

[0033] (8) Calcinate the microsphere fresh catalyst to obtain an iron-based Fischer-Tropsch synthesis catalyst in an oxidized state.

[0034] In some embodiments, in step (1) of the above method, the soluble salt of iron is iron nitrate, specifically, it can be Fe(NO 3 ) 3 ·9H 2 O.

[0035] In some embodiments, in step (1) of the above method, the concentration of the iron nitrate solution can be 10wt% to 45wt%, preferably 10wt% to 40wt%, for example 15wt% to 40wt%.

[0036] In some embodiments, in step (1) of the above method, the structural promoter A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce, and Mo; preferably, the structural promoter A is at least one selected from Mn, La, Cr, Zr, and Cu. In some preferred embodiments, the precursor aqueous solution of the promoter A is a nitrate aqueous solution; preferably, the precursor aqueous solution of the structural promoter A is at least one selected from Mn(NO 3 ) 2 aqueous solution, La(NO 3 ) 3 aqueous solution, Cr(NO 3 ) 3 aqueous solution, ZrO(NO 3 ) 2 aqueous solution, Cu(NO 3 ) 2 aqueous solution. In some preferred embodiments, the mass concentration of the precursor solution of the structural promoter A is 10% to 60%, preferably 10% to 50%.

[0037] In some embodiments, in step (1) of the above method, the support promoter B is Si. Preferably, the precursor solution of the support promoter B is at least one selected from silica sol and water glass. In some preferred embodiments, the mass concentration of the precursor solution of the support promoter B is 10% to 50%, preferably 15% to 45%, for example 20% to 40%.

[0038] In some embodiments, in step (1) of the above method, the mass ratio of iron to each promoter is Fe:A:B = 100:(1 to 50):(0 to 30), where A and B are not both 0 at the same time. Preferably, the mass ratio of iron to each promoter is Fe:A:B = 100:(5 to 40):(0 to 20), preferably 100:(5 to 35):(0 to 15), where A and B are not both 0 at the same time.

[0039] In some embodiments, in the step (2), the precipitant is an aqueous ammonia solution, and the mass concentration of the solution is 5% to 30%, preferably 15% to 25%, such as 20%.

[0040] In some embodiments, in the step (2), the precipitation reaction is carried out under the following conditions: the pH value of the reaction system is controlled to be 7 to 11, preferably 7.5 to 10 (such as 8 to 10, 8 to 9.5, 8.5 to 9.0); the temperature is 40°C to 95°C, preferably 50°C to 90°C (such as 55°C to 85°C).

[0041] In some embodiments, in the step (3), the precursor solution of the doping element C is at least one selected from aqueous nitrate solutions or aqueous acetate solutions of samarium (Sm), scandium (Sc), gallium (Ga), yttrium (Y), zinc (Zn), magnesium (Mg), beryllium (Be), barium (Ba), strontium (Sr), and boron (B). Preferably, the doping element C is one or more selected from Ga, Sr, Zn, and Sm. In some preferred embodiments, the precursor solution of the doping element C is at least one selected from an aqueous gallium nitrate solution, an aqueous strontium nitrate solution, an aqueous zinc nitrate solution, and an aqueous samarium nitrate solution.

[0042] In some embodiments, the mass concentration of the precursor solution of the doping element C is 1% to 50%, preferably 10% to 30%, such as 20% to 30%.

[0043] In some embodiments, in the step (3), after adding the precursor solution of the doping element C, stirring is continued for 20 min to 2 h, preferably 20 min to 1.5 h, 20 min to 1 h.

[0044] In some embodiments, in the step (4), the temperature of the hydrothermal reaction is 120°C to 200°C, preferably 160°C to 180°C, and the time is 5 h to 25 h, preferably 10 h to 20 h.

[0045] In this article, in the step (5), the washing and pressure filtration are conventional means in the art and are carried out according to the conventional conditions and methods in the art.

[0046] In some embodiments, in step (6), the water is deionized water, purified water, distilled water, double-distilled water, ultrapure water, etc. In some embodiments, in step (6), deionized water is added to the filter cake and stirred into a paste. In some embodiments, in step (6), the emulsification is carried out at a rotation speed of 1000 r / min to 3500 r / min, preferably 1000 r / min to 3000 r / min, for example 1000 r / min to 2500 r / min. In some embodiments, in step (6), the continuous emulsification is carried out for 10 min to 120 min, preferably 15 min to 60 min, for example 15 min to 30 min, 15 min to 25 min.

[0047] In some embodiments, in step (6), the electronic auxiliary agent D is at least one selected from lithium, sodium, potassium, rubidium, and cesium; preferably potassium. In some embodiments, the precursor solution of the electronic auxiliary agent D is at least one selected from aqueous solutions of soluble salts (such as nitrates, carbonates, or bicarbonates) of lithium, sodium, potassium, rubidium, and cesium; preferably an aqueous potassium carbonate solution, an aqueous potassium nitrate solution, or an aqueous potassium bicarbonate solution. In some preferred embodiments, the mass concentration of the precursor solution of the electronic auxiliary agent D is 10% to 50%, preferably 20% to 45%, for example 20% to 40%.

[0048] In some embodiments, in step (7), the spray drying is carried out in a spray dryer. In some embodiments, in step (7), the conditions for the spray drying are: the inlet air temperature is 200°C to 400°C (preferably 220°C to 350°C, 230°C to 330°C), and the outlet temperature is 90°C to 180°C (preferably 90°C to 120°C, for example 95°C to 115°C).

[0049] In some embodiments, in step (8), the temperature of the roasting is 300°C to 800°C, and the time is 2 h to 12 h; preferably, the temperature of the roasting is 500°C to 700°C, and the time is 3 h to 10 h (for example 4 h to 10 h).

[0050] In some embodiments, in the step (8), for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(1-50):(0-30):(0.1-10):(0.5-15), and A and B are not both 0 at the same time. Preferably, for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(5-40):(0-20):(3-10):(1-10), preferably 100:(5-35):(0-15):(5-8):(3-7.5), wherein A and B are not both 0 at the same time.

[0051] In some embodiments, the present invention provides a low CO 2 selectivity iron-based Fischer-Tropsch synthesis catalyst prepared by the above method, comprising a main active element Fe, a structural promoter A, a support promoter B, an electronic promoter D and a doping element C, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr and B, and by mass ratio, Fe:A:B:C:D = 100:(1-50):(0-30):(0.1-10):(0.5-15), wherein A and B are not both 0 at the same time.

[0052] In some embodiments, the structural promoter A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce and Mo. Preferably, the structural promoter A is at least one selected from Mn, La, Cr, Zr and Cu.

[0053] In some embodiments, the support promoter B is Si.

[0054] In some embodiments, the doping element C is one or more selected from Ga, Sr, Zn and Sm.

[0055] In some embodiments, the electronic promoter D is at least one selected from lithium, sodium, potassium, rubidium and cesium; preferably potassium.

[0056] In some embodiments, by mass ratio, Fe:A:B:C:D = 100:(5-40):(0-20):(3-10):(1-10), preferably 100:(5-35):(0-15):(5-8):(3-7.5), wherein A and B are not both 0 at the same time.

[0057] In some embodiments, the present invention provides the use of the above iron-based Fischer-Tropsch synthesis catalyst in reducing CO in the Fischer-Tropsch synthesis reaction 2 selectivity.

[0058] In some embodiments, before the iron-based Fischer-Tropsch synthesis catalyst is used in the Fischer-Tropsch synthesis reaction, it is reduced for 10 h to 35 h (preferably 15 h to 30 h) under the following conditions: H 2 / CO = 1 to 100 (preferably 2 to 90), 250 °C to 350 °C (preferably 275 °C to 300 °C), and the space velocity is 3000 h -1 to 25000 h -1 (preferably 5000 h -1 to 20000 h -1 ), and the pressure is 0.05 Mpa to 5.0 Mpa (preferably 0.1 Mpa to 3.0 Mpa).

[0059] In some embodiments, the Fischer-Tropsch synthesis reaction is carried out in a slurry bed reactor.

[0060] In some embodiments, the Fischer-Tropsch synthesis reaction is carried out under the conditions of a temperature of 250 °C to 350 °C (preferably 270 °C to 285 °C), a space velocity of 5000 h -1 to 12000 h -1 (preferably 7000 h -1 to 10000 h -1 ), a pressure of 1.0 Mpa to 5.0 Mpa (preferably 2.0 Mpa to 3.0 Mpa), an H 2 / CO ratio of 1 to 3 (preferably 2 to 3), and a recycle ratio of 1 to 2.5 (preferably 1.5 to 2.0).

[0061] Next, the technical solution of the present invention will be exemplarily described by the content in the following numbered paragraphs:

[0062] 1. A method for preparing an iron-based Fischer-Tropsch synthesis catalyst with low CO 2 selectivity, comprising:

[0063] (1) Mixing a soluble salt solution of iron with a precursor solution of a structural aid A and an optional precursor solution of a support aid B to obtain a mixed solution;

[0064] (2) Mixing the mixed solution obtained in step (1) with a precipitant, and causing the resulting reaction system to undergo a precipitation reaction under stirring to obtain a precipitate slurry I;

[0065] (3) Adding a precursor solution of a doping element C to the slurry I obtained in step (2) under stirring to obtain a mixed slurry II, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr, and B;

[0066] (4) Transfer the slurry II obtained in step (3) into a hydrothermal reactor, and carry out hydrothermal reaction at 100°C to 250°C for 5 h to 30 h under stirring and closed conditions. After cooling to room temperature, precipitate slurry III is obtained;

[0067] (5) Wash and filter press the slurry III obtained in step (4) to obtain a filter cake;

[0068] (6) Add water to the filter cake and stir to form a paste, and then carry out emulsification. During the emulsification process, add the precursor solution of electronic additive D, and continue emulsification to obtain a catalyst precursor;

[0069] (7) Spray-dry the catalyst precursor to obtain a microsphere-shaped fresh catalyst;

[0070] (8) Calcinate the microsphere-shaped fresh catalyst to obtain an iron-based Fischer-Tropsch synthesis catalyst in an oxidized state.

[0071] 2. The method according to paragraph 1, wherein, in step (1), the soluble salt of iron is iron nitrate.

[0072] 3. The method according to paragraph 2, wherein the concentration of the iron nitrate solution is 10 wt% to 45 wt%.

[0073] 4. The method according to any one of paragraphs 1-3, wherein, in step (1), the structural promoter A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce and Mo.

[0074] 5. The method according to any one of paragraphs 1-4, wherein, in step (1), the precursor aqueous solution of the structural promoter A is an aqueous nitrate solution.

[0075] 6. The method according to any one of paragraphs 1-5, wherein the mass concentration of the precursor solution of the structural promoter A is 10% to 60%.

[0076] 7. The method according to any one of paragraphs 1-6, wherein, in step (1), the support promoter B is Si.

[0077] 8. The method according to any one of paragraphs 1-7, wherein, in step (1), the precursor solution of the support promoter B is at least one selected from silica sol and water glass.

[0078] 9. The method according to any one of paragraphs 1-8, wherein, in step (1), the mass concentration of the precursor solution of the support promoter B is 10% to 50%.

[0079] 10. The method as described in any one of paragraphs 1 - 9, wherein in step (1), the mass ratio of iron to each promoter is Fe:A:B = 100:(1 - 50):(0 - 30), where A and B are not both 0.

[0080] 11. The method as described in paragraph 10, wherein the mass ratio of iron to each promoter is Fe:A:B = 100:(5 - 40):(0 - 20), where A and B are not both 0.

[0081] 12. The method as described in any one of paragraphs 1 - 11, wherein in step (2), the precipitating agent is an ammonia water solution, and the mass concentration of the ammonia water solution is 5% - 30%.

[0082] 13. The method as described in any one of paragraphs 1 - 12, wherein in step (2), the precipitation reaction is carried out under the following conditions: controlling the pH value of the reaction system to be 7 - 11; the temperature is 40°C - 95°C.

[0083] 14. The method as described in any one of paragraphs 1 - 13, wherein in step (3), the precursor solution of the doping element C is at least one selected from aqueous nitrate solutions or aqueous acetate solutions of Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Sr, B.

[0084] 15. The method as described in any one of paragraphs 1 - 14, wherein in step (3), the doping element C is one or more selected from Ga, Sr, Zn, and Sm.

[0085] 16. The method as described in any one of paragraphs 1 - 15, wherein in step (3), the mass concentration of the precursor solution of the doping element C is 1% - 50%.

[0086] 17. The method as described in any one of paragraphs 1 - 16, wherein in step (3), after adding the precursor solution of the doping element C, stirring continues for 20 min - 2 h.

[0087] 18. The method as described in any one of paragraphs 1 - 17, wherein in step (4), the temperature of the hydrothermal reaction is 120°C - 200°C, and the time is 5 h - 25 h.

[0088] 19. The method as described in any one of paragraphs 1 - 18, wherein in step (6), the water is deionized water, purified water, distilled water, double distilled water, or ultrapure water.

[0089] 20. The method as described in any one of paragraphs 1 - 19, wherein in step (6), the emulsification is carried out at a rotation speed of 1000 r / min - 3500 r / min.

[0090] 21. The method as described in any one of paragraphs 1-20, wherein in step (6), the continuous emulsification is carried out for 10 min to 120 min.

[0091] 22. The method as described in any one of paragraphs 1-21, wherein in step (6), the electronic auxiliary agent D is at least one selected from lithium, sodium, potassium, rubidium, and cesium.

[0092] 23. The method as described in any one of paragraphs 1-22, wherein in step (6), the precursor solution of the electronic auxiliary agent D is at least one selected from nitrate, carbonate, or bicarbonate aqueous solutions of lithium, sodium, potassium, rubidium, and cesium.

[0093] 24. The method as described in any one of paragraphs 1-23, wherein in step (6), the mass concentration of the precursor solution of the electronic auxiliary agent D is 10% to 50%.

[0094] 25. The method as described in any one of paragraphs 1-24, wherein in step (7), the conditions for spray drying are: the inlet air temperature is 200°C to 400°C, and the outlet temperature is 90°C to 180°C.

[0095] 26. The method as described in any one of paragraphs 1-25, wherein in step (8), the calcination temperature is 300°C to 800°C, and the time is 2 h to 12 h.

[0096] 27. The method as described in any one of paragraphs 1-26, wherein in step (8), for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(1-50):(0-30):(0.1-10):(0.5-15), and A and B are not both 0.

[0097] 28. The method as described in paragraph 27, wherein for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(5-40):(0-20):(3-10):(1-10), wherein A and B are not both 0.

[0098] 29. A low-CO prepared by the method as described in any one of paragraphs 1-28 2Selective iron-based Fischer-Tropsch synthesis catalyst, comprising a main active element Fe, a structural promoter A, a support promoter B, an electronic promoter D and a doping element C, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr and B, and by mass ratio, Fe:A:B:C:D = 100:(1-50):(0-30):(0.1-10):(0.5-15), wherein A and B are not both 0.

[0099] 30. The iron-based Fischer-Tropsch synthesis catalyst according to paragraph 29, wherein the structural promoter A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce and Mo; and the support promoter B is Si.

[0100] 31. The iron-based Fischer-Tropsch synthesis catalyst according to paragraph 29 or 30, wherein the doping element C is one or more selected from Ga, Sr, Zn and Sm.

[0101] 32. The iron-based Fischer-Tropsch synthesis catalyst according to any one of paragraphs 29-31, wherein the electronic promoter D is at least one selected from lithium, sodium, potassium, rubidium and cesium.

[0102] 33. The iron-based Fischer-Tropsch synthesis catalyst according to any one of paragraphs 29-32, wherein by mass ratio, Fe:A:B:C:D = 100:(5-40):(0-20):(3-10):(1-10), wherein A and B are not both 0.

[0103] 34. Use of the iron-based Fischer-Tropsch synthesis catalyst according to any one of paragraphs 29-33 in reducing the CO 2 selectivity in the Fischer-Tropsch synthesis reaction.

[0104] 35. The use according to paragraph 34, wherein before using the iron-based Fischer-Tropsch synthesis catalyst in the Fischer-Tropsch synthesis reaction, it is reduced for 10 h to 35 h under the following conditions: H 2 / CO = 1-100, 250 °C to 350 °C, space velocity of 3000 h -1 to 25000 h -1 and pressure of 0.05 Mpa to 5.0 Mpa.

[0105] 36. The use according to paragraph 34 or 35, wherein the Fischer-Tropsch synthesis reaction is carried out in a slurry bed reactor.

[0106] 37. The use according to any one of paragraphs 34-36, wherein at a temperature of 250 °C to 350 °C and a space velocity of 5000 h -1 to 12000 h -1, under the conditions of a pressure of 1.0 Mpa to 5.0 Mpa, an H 2 / CO ratio of 1 to 3, and a circulation ratio of 1 to 2.5, the Fischer-Tropsch synthesis reaction is carried out.

[0107] The iron-based Fischer-Tropsch synthesis catalyst prepared by the above method of the present invention, due to the combination of hydrothermal reaction and the addition of doped elements during the preparation process, when used in the Fischer-Tropsch synthesis reaction after preparation, helps to cause a change in the microstructure of Fe 3 O 4 in the catalyst during the pre-treatment of the catalyst before the reaction, so that the tetrahedral site (A-site) Fe increases and the octahedral site Fe (B-site) decreases, thereby reducing the CO 2 selectivity in the subsequent Fischer-Tropsch synthesis reaction.

[0108] Examples

[0109] Unless otherwise specified, the various reagents, materials and equipment used in the following examples are conventional reagents, materials and equipment known in the art, which can be commercially available or prepared or provided by those skilled in the art through conventional methods.

[0110] Comparative Example 1

[0111] Take 7.3 Kg of Fe(NO 3 ) 3 ·9H 2 O, add deionized water to prepare a ferric nitrate solution with a concentration of 35%. Take 380.9 g of Cu(NO 3 ) 2 ·3H 2 O and 1.16 Kg of Cr(NO 3 ) 3 ·9H 2 O, add deionized water to prepare a mixed solution with a mass concentration of 20%. Add the mixed solution and 566 g of silica sol with a mass concentration of 30% to the ferric nitrate solution in sequence, stir and mix evenly, and adjust the temperature of the mixed solution to 60 °C. Prepare an ammonia water solution with a mass concentration of 20%, and adjust the temperature of the ammonia water solution to 40 °C. Turn on the stirring device of the synthesis reactor, add the mixed solution and the ammonia water solution into the synthesis reactor in parallel, and adjust the pH value of the precipitation slurry to 8.5 and the temperature to 70 °C.

[0112] After the precipitation is completed, add 925 g of gallium nitrate aqueous solution with a mass concentration of 20% to the slurry under stirring, and continue to stir and age for 1 h.

[0113] After washing the obtained slurry with deionized water, it was pressure-filtered to obtain a filter cake. Then, deionized water was added to the filter cake and stirred until it became pasty. Under the condition that the rotation speed of the emulsifier was 2000 r / min, 268 g of an aqueous potassium carbonate solution with a mass concentration of 20% was added, and emulsification was continued for 15 min to obtain a pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer. Among them, the inlet air temperature was controlled at 300 °C and the outlet temperature was 95 °C to obtain a microsphere-shaped fresh catalyst; the microsphere-shaped fresh catalyst was calcined at 600 °C for 5 h to obtain a Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of the catalyst in this comparative example was Fe:Cr:Cu:Si:Ga:K = 100:15:10:8:5:3.

[0114] The catalyst was reduced at H 2 / CO = 10, 280 °C, a space velocity of 6000 h -1 , and a pressure of 0.2 Mpa for 20 h to obtain a reduced catalyst; then at a temperature of 270 °C, a space velocity of 9000 h -1 , a pressure of 2.0 Mpa, and an H 2 / CO ratio of 2, and a recycle ratio of 1.5, the Fischer-Tropsch synthesis reaction was carried out in a slurry bed reactor, and the results are shown in Table 1.

[0115] Comparative Example 2

[0116] 7.3 Kg of Fe(NO 3 ) 3 ·9H 2 O was taken and dissolved in deionized water to prepare a ferric nitrate solution with a concentration of 35%. 380.9 g of Cu(NO 3 ) 2 ·3H 2 O and 1.16 Kg of Cr(NO 3 ) 3 ·9H 2 O were taken and dissolved in deionized water to prepare a mixed solution with a mass concentration of 20%. The mixed solution and 566 g of a silica sol with a mass concentration of 30% were successively added to the ferric nitrate solution, stirred and mixed evenly, and the temperature of the mixed solution was adjusted to 60 °C. An aqueous ammonia solution with a mass concentration of 20% was prepared, and the temperature of the aqueous ammonia solution was adjusted to 40 °C. The stirring device of the synthesis reactor was started, and the mixed solution and the alkaline solution (aqueous ammonia solution) were added to the synthesis reactor in a co-current manner, and the pH value of the precipitation slurry was adjusted to 8.5 and the temperature was adjusted to 70 °C.

[0117] Subsequently, the above slurry was transferred to a hydrothermal reaction kettle, and a hydrothermal reaction was carried out at 180 °C for 10 h under stirring, and then it was naturally cooled to room temperature.

[0118] After washing the obtained slurry with deionized water, it was pressure-filtered to obtain a filter cake. Then, deionized water was added to the filter cake and stirred until it became paste-like. Under the condition that the rotation speed of the emulsifier was 2000 r / min, 268 g of an aqueous potassium carbonate solution with a mass concentration of 20% was added, and emulsification was continued for 15 min to obtain the pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer, where the inlet air temperature was controlled at 300 °C and the outlet temperature was 95 °C to obtain spherical fresh catalysts; the spherical fresh catalysts were calcined at 600 °C for 5 h to obtain the Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of the catalyst in this comparative example was Fe:Cr:Cu:Si:K = 100:15:10:8:3.

[0119] The catalyst was reduced under the conditions of H 2 / CO = 10, 280 °C, a space velocity of 6000 h -1 , and a pressure of 0.2 Mpa for 20 h to obtain the reduced catalyst; then, at a temperature of 270 °C, a space velocity of 9000 h -1 , a pressure of 2.0 Mpa, and an H 2 / CO ratio of 2, and a recycle ratio of 1.5, the Fischer-Tropsch synthesis reaction was carried out in a slurry bed reactor, and the results are shown in Table 1.

[0120] Example 1

[0121] 7.3 Kg of Fe(NO 3 ) 3 ·9H 2 O was taken and dissolved in deionized water to prepare an iron nitrate solution with a concentration of 15%. 380.9 g of Cu(NO 3 ) 2 ·3H 2 O and 1.16 Kg of Cr(NO 3 ) 3 ·9H 2 O were taken and dissolved in deionized water to prepare a mixed solution with a mass concentration of 20%. The mixed solution and 566 g of a silica sol with a mass concentration of 30% were successively added to the iron nitrate solution, stirred and mixed evenly, and the temperature of the mixed solution was adjusted to 60 °C. An aqueous ammonia solution with a mass concentration of 20% was prepared, and the temperature of the aqueous ammonia solution was adjusted to 40 °C. The stirring device of the synthesis reactor was started, and the mixed solution and the ammonia water solution were added to the synthesis reactor in a parallel flow manner, and the pH value of the precipitated slurry was adjusted to 8.5 and the temperature was adjusted to 70 °C.

[0122] After precipitation, 925 g of an aqueous gallium nitrate solution with a mass concentration of 20% was added to the slurry under stirring, and stirring was continued for 1 h. Subsequently, the slurry was transferred to a hydrothermal reaction kettle, and a hydrothermal reaction was carried out at 180 °C for 10 h under stirring, and then it was naturally cooled to room temperature.

[0123] After washing the hydrothermal slurry with deionized water, it was pressure-filtered to obtain a filter cake. Then, deionized water was added to the filter cake and stirred until it became paste-like. Under the condition that the rotation speed of the emulsifier was 2000 r / min, 268 g of an aqueous potassium carbonate solution with a mass concentration of 20% was added, and emulsification was continued for 15 min to obtain the pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer. Among them, the inlet air temperature was controlled at 300 °C and the outlet temperature was 95 °C to obtain spherical fresh catalysts; the spherical fresh catalysts were calcined at 600 °C for 5 h to obtain Fischer-Tropsch synthesis iron-based catalysts. The weight composition ratio of the catalysts in this example was Fe:Cr:Cu:Si:Ga:K = 100:15:10:8:5:3, denoted as Cat1.

[0124] The catalyst Cat1 of this example was reduced in H 2 / CO = 10, 280 °C, with a space velocity of 6000 h -1 for 20 h to obtain the reduced catalyst; then the reduced catalyst was used at a temperature of 270 °C, a space velocity of 9000 h -1 , a pressure of 2.0 Mpa, and an H 2 / CO ratio of 2 and a recycle ratio of 1.5 in a slurry bed reactor for Fischer-Tropsch synthesis reaction, and the results are shown in Table 1.

[0125] Example 2

[0126] 6.0 Kg of Fe(NO 3 ) 3 ·9H 2 O was taken and dissolved in deionized water to prepare an iron nitrate solution with a mass concentration of 40%. 157.0 g of Cu(NO 3 ) 2 ·3H 2 O was taken and dissolved in deionized water to prepare a solution with a mass concentration of 10%. The prepared Cu(NO 3 ) 2 solution and 656 g of a 40% silica sol were successively added to the iron nitrate solution, stirred and mixed evenly, and the temperature of the mixed solution was adjusted to 60 °C. An ammonia water solution with a mass concentration of 20% was prepared, and the temperature of the ammonia water solution was adjusted to 40 °C. The stirring device of the synthesis reactor was started, and the mixed solution and the ammonia water solution were added to the synthesis reactor in parallel flow, and the pH value of the precipitation slurry was adjusted to 8.0 and the temperature was 75 °C.

[0127] After precipitation, 508.6 g of an aqueous gallium nitrate solution with a mass concentration of 30% was added to the slurry under stirring, and stirring was continued for 30 min. Then, 301.3 g of an aqueous strontium nitrate solution with a mass concentration of 20% was added, and stirring was continued for 20 min. Then, it was transferred to a hydrothermal reaction kettle, and hydrothermal reaction was carried out at 160 °C for 10 h under stirring, and finally it was naturally cooled to room temperature.

[0128] The hydrothermally treated slurry was washed with deionized water and pressure-filtered to obtain a filter cake. Deionized water was added to the filter cake and stirred until it became paste-like. Under the condition that the rotation speed of the emulsifier was 2500 r / min, 269.8 g of an aqueous potassium carbonate solution with a mass concentration of 30% was added, and emulsification was continued for 15 min to obtain a pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer. Among them, the inlet air temperature was controlled at 230 °C and the outlet temperature was 100 °C to obtain a microsphere-shaped fresh catalyst 2; the microsphere-shaped fresh catalyst 2 was calcined at 550 °C for 8 h to obtain a Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of this catalyst was Fe:Cu:Si:Ga:Sr:K = 100:5:15:5:3:5.5, denoted as Cat2.

[0129] The catalyst Cat2 of this example was reduced at H 2 / CO = 20, 285 °C, and a space velocity of 7000 h -1 for 24 h to obtain a reduced catalyst; then the reduced catalyst was used at a temperature of 280 °C, a space velocity of 9000 h -1 , a pressure of 3.0 Mpa, and an H 2 / CO ratio of 2 and a recycle ratio of 2.0 in a slurry bed reactor for Fischer-Tropsch synthesis reaction. The results are shown in Table 1.

[0130] Example 3

[0131] Take 5 kg of Fe(NO 3 ) 3 ·9H 2 O, and add deionized water to prepare an aqueous ferric nitrate solution with a mass concentration of 20%. Take 533.1 g of Cr(NO 3 ) 3 ·9H 2 O, and add deionized water to prepare a solution with a mass concentration of 30%. Mix the Cr(NO 3 ) 3 solution, 226 g of an aqueous Mn(NO 3 ) 2An aqueous solution and 1.46 Kg of silica sol with a mass concentration of 40% were successively added to the iron nitrate solution, stirred and mixed evenly, and the temperature of the mixed solution was adjusted to 60 °C. An aqueous ammonia solution with a mass concentration of 20% was prepared, and the temperature of the aqueous ammonia solution was adjusted to 40 °C. The stirring device of the synthesis reactor was started, the ammonia water was added to the mixed iron nitrate solution, and the pH value of the precipitation slurry was adjusted to 9.0 and the temperature was 60 °C.

[0132] After the precipitation was completed, 1.02 Kg of an aqueous gallium nitrate solution with a mass concentration of 20% was added to the slurry under stirring, and stirring was continued for 30 min, then it was transferred to a hydrothermal reaction kettle, and hydrothermal reaction was carried out at 180 °C for 10 h under stirring, and finally it was naturally cooled to room temperature.

[0133] The hydrothermally treated slurry was washed with deionized water and pressure-filtered to obtain a filter cake. Deionized water was added to the filter cake and stirred until it became pasty. Under the condition that the rotation speed of the emulsifier was 1500 r / min, 291.7 g of an aqueous potassium nitrate solution with a mass concentration of 40% was added, and emulsification was continued for 25 min to obtain the pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer. Among them, the inlet air temperature was controlled at 270 °C and the outlet temperature was 95 °C to obtain a microsphere-shaped fresh catalyst; the microsphere-shaped fresh catalyst was calcined at 620 °C for 5 h to obtain a Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of this catalyst was Fe:Mn:Cr:Si:Ga:K = 100:5:10:10:8:6.5, denoted as Cat3.

[0134] The catalyst Cat3 of this example was reduced in H 2 / CO = 2, 275 °C, space velocity of 5000 h -1 , and pressure of 0.1 Mpa for 30 h to obtain a reduced catalyst; then the reduced catalyst was used at a temperature of 275 °C, a space velocity of 10000 h -1 , a pressure of 2.5 Mpa, H 2 / CO ratio of 2.5, and a recycle ratio of 1.5 in a slurry bed reactor for Fischer-Tropsch synthesis reaction. The results are shown in Table 1.

[0135] Example 4

[0136] Take 3.0 Kg of Fe(NO 3 ) 3 ·9H 2 O, and add deionized water to prepare an iron nitrate solution with a mass concentration of 35%. Take 325 g of Cu(NO 3 ) 2 ·3H 2 O and 194.4 g of La(NO 3 ) 3 ·6H 2O, add deionized water to prepare a mixed solution with a mass concentration of 30%. Add the mixed solution and 437 g of silica sol with a mass concentration of 20% to the iron nitrate solution successively, stir and mix evenly, and adjust the temperature of the mixed solution to 60 °C. Prepare an ammonia water solution with a mass concentration of 20%, and adjust the temperature of the ammonia water solution to 40 °C. Turn on the stirring device of the synthesis reactor, add the mixed solution and the ammonia water solution into the synthesis reactor in parallel flow, adjust the pH value of the precipitate slurry to 9.0, and the temperature to 55 °C.

[0137] After precipitation, add 484 g of zinc nitrate aqueous solution with a mass concentration of 20% to the slurry under stirring, continue to stir for 20 min, then transfer it to a hydrothermal reaction kettle, and carry out hydrothermal reaction at 160 °C for 20 h under stirring, and then naturally cool to room temperature.

[0138] Wash the hydrothermal slurry with deionized water and filter it under pressure to obtain a filter cake. Add deionized water to the filter cake and stir until it becomes paste-like. Under the condition that the emulsifier rotation speed is 2500 r / min, add 323 g of KNO aqueous solution with a mass concentration of 25% 3 and continue to emulsify for 20 min to obtain the pre-spray slurry. Spray-dry the pre-spray slurry in a spray dryer. Among them, control the inlet air temperature to be 300 °C and the outlet temperature to be 115 °C to obtain a microsphere-shaped fresh catalyst; calcine the microsphere-shaped fresh catalyst at 500 °C for 10 h to obtain a Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of this catalyst is Fe:La:Cu:Si:Zn:K = 100:15:8:10:8:7.5, denoted as Cat4.

[0139] Reduce the catalyst Cat4 of this example in H 2 / CO = 90, 290 °C, space velocity of 20000 h -1 , and pressure of 3.0 Mpa for 15 h to obtain a reduced catalyst; then use the reduced catalyst at a temperature of 285 °C, space velocity of 8000 h -1 , pressure of 2.5 Mpa, H 2 / CO ratio of 2, and circulation ratio of 1.5 to carry out Fischer-Tropsch synthesis reaction in a slurry bed reactor. The results are shown in Table 1.

[0140] Example 5

[0141] Take 4.5 Kg of Fe(NO 3 ) 3 ·9H 2 O, add deionized water to prepare an iron nitrate solution with a mass concentration of 30%. Take 611 g of Cu(NO 3 ) 2 ·3H 2 O and 292 g of La(NO3 ) 3 ·6H 2 O, deionized water was added to prepare a mixed solution with a mass concentration of 30%. The mixed solution and 792 g of a 20% mass concentration of ZrO(NO 3 ) 2 were successively added to the iron nitrate solution, stirred and mixed evenly, and the temperature of the mixed solution was adjusted to 65 °C. An ammonia water solution with a mass concentration of 20% was prepared, and the temperature of the ammonia water solution was adjusted to 40 °C. The stirring device of the synthesis reactor was started, and the mixed solution and the ammonia water solution were added to the synthesis reactor in parallel flow, and the pH value of the precipitated slurry was adjusted to 9.0 and the temperature was 85 °C.

[0142] After precipitation, 558 g of a 20% mass concentration of samarium nitrate aqueous solution was added to the slurry under stirring, and stirring was continued for 30 min, and then it was transferred to a hydrothermal reaction kettle and hydrothermally reacted at 170 °C for 20 h under stirring, and then naturally cooled to room temperature.

[0143] The hydrothermally treated slurry was washed with deionized water and filtered under pressure to obtain a filter cake. Deionized water was added to the filter cake and stirred until it became paste-like. Under the condition that the rotation speed of the emulsifier was 1000 r / min, 328 g of a 30% mass concentration of KHCO 3 aqueous solution was added, and emulsification was continued for 20 min to obtain a pre-spray slurry. The pre-spray slurry was spray-dried in a spray dryer. Among them, the inlet air temperature was controlled to be 330 °C and the outlet temperature was 105 °C to obtain a microsphere-shaped fresh catalyst; the microsphere-shaped fresh catalyst was calcined at 700 °C for 4 h to obtain a Fischer-Tropsch synthesis iron-based catalyst. The weight composition ratio of this catalyst was Fe:La:Zr:Cu:Sm:K = 100:15:10:10:8:7, denoted as Cat5.

[0144] The catalyst Cat5 of this example was reduced under the conditions of H 2 / CO = 15, 300 °C, a space velocity of 10000 h -1 , and a pressure of 2.0 Mpa for 20 h to obtain a reduced catalyst; then the reduced catalyst was used at a temperature of 285 °C, a space velocity of 700 Qh -1 , a pressure of 3.0 Mpa, an H 2 / CO ratio of 3, and a recycle ratio of 1.5 in a slurry bed reactor for Fischer-Tropsch synthesis reaction. The results are shown in Table 1.

[0145] Table 1 Fischer-Tropsch synthesis reaction conditions and results of catalysts prepared in each example and comparative example

[0146]

[0147]

[0148] a: The recycle ratio refers to the molar ratio of recycle gas to feed gas

[0149] b: In the pretreated catalyst, Fe 3 O 4 The ratio of the octahedral site (B-site) to the tetrahedral site (A-site) in the structure is determined by spectral determination

[0150] As can be seen from Table 1, if no hydrothermal reaction is carried out (Comparative Example 1) or no doping element is added (Comparative Example 2) during the preparation of the catalyst, when the catalyst is used in the Fischer-Tropsch synthesis reaction, the ratio of B-site to A-site in the Fe 3 O 4 crystal structure of the pretreated catalyst is close to the theoretical ratio of 2.0. When the preparation method provided by the present invention (adding a doping element and carrying out a hydrothermal reaction) is used to prepare the catalyst, the ratio of B-site to A-site in the Fe 3 O 4 crystal structure of the obtained catalyst after pretreatment is significantly reduced, thereby destroying the structure of the WGS reaction active phase, and thus significantly reducing the CO 2 selectivity of the Fischer-Tropsch synthesis reaction. In addition, the catalyst prepared by the method of the present invention also has the characteristics of high reaction activity and low CH 4 selectivity.

Claims

1. A method for preparing a low CO 2 selectivity iron-based Fischer-Tropsch synthesis catalyst Comprising: (1) Mixing a soluble iron salt solution with a precursor solution of structural promoter A and optionally a precursor solution of support promoter B to obtain a mixed solution; (2) Mixing the mixed solution obtained in step (1) with a precipitant, and causing the resulting reaction system to undergo a precipitation reaction under stirring to obtain precipitate slurry I; (3) Adding a precursor solution of doping element C to the slurry I obtained in step (2) under stirring to obtain mixed slurry II, wherein the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr, and B; (4) Transferring the slurry II obtained in step (3) into a hydrothermal reaction kettle, and carrying out hydrothermal reaction at 100 °C to 250 °C for 5 h to 30 h under stirring and sealed conditions, and cooling to room temperature to obtain precipitate slurry III; (5) Washing and pressure filtering the slurry III obtained in step (4) to obtain a filter cake; (6) Adding water to the filter cake and stirring into a paste, and then carrying out emulsification. During the emulsification process, adding a precursor solution of electronic promoter D, and continuing emulsification to obtain a catalyst precursor; (7) Spray drying the catalyst precursor to obtain a microsphere-shaped fresh catalyst; (8) Calcining the microsphere-shaped fresh catalyst to obtain an iron-based Fischer-Tropsch synthesis catalyst in an oxidized state.

2. The method according to claim 1, wherein, in step (1), the soluble iron salt is iron nitrate; Preferably, the concentration of the iron nitrate solution is 10 wt% to 45 wt%; Preferably, in step (1), the structural promoter A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce, and Mo; Preferably, in step (1), the precursor aqueous solution of the structural promoter A is a nitrate aqueous solution; Preferably, the mass concentration of the precursor solution of the structural promoter A is 10% to 60%; Preferably, in step (1), the support promoter B is Si; Preferably, in step (1), the precursor solution of the support promoter B is at least one selected from silica sol and water glass; Preferably, in step (1), the mass concentration of the precursor solution of the support promoter B is 10% to 50%; Preferably, in step (1), the mass ratio of iron to each promoter is Fe:A:B = 100:(1 to 50):(0 to 30), wherein A and B are not both 0; Preferably, the mass ratio of iron to each promoter is Fe:A:B = 100:(5 to 40):(0 to 20), wherein A and B are not both 0.

3. The method according to claim 1 or 2, wherein, in step (2), the precipitant is an ammonia aqueous solution, and the mass concentration of the ammonia aqueous solution is 5% to 30%; Preferably, in step (2), the precipitation reaction is carried out under the following conditions: controlling the pH value of the reaction system to be 7 to 11; the temperature is 40 °C to 95 °C.

4. The method according to any one of claims 1 - 3, wherein, In step (3), the precursor solution of the doping element C is at least one selected from aqueous nitrate solutions or aqueous acetate solutions of Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Sr, and B; Preferably, in step (3), the doping element C is one or more selected from Ga, Sr, Zn, and Sm; Preferably, in step (3), the mass concentration of the precursor solution of the doping element C is 1% - 50%; Preferably, in step (3), after adding the precursor solution of the doping element C, stirring continues for 20 min - 2 h; Preferably, in step (4), the temperature of the hydrothermal reaction is 120°C - 200°C, and the time is 5 h - 25 h.

5. The method according to any one of claims 1 - 4, wherein, in step (6), the water is deionized water, pure water, distilled water, double-distilled water, or ultrapure water; Preferably, in step (6), the emulsification is carried out at a rotation speed of 1000 r / min - 3500 r / min; Preferably, in step (6), the continued emulsification is carried out for 10 min - 120 min; Preferably, in step (6), the electronic auxiliary agent D is at least one selected from lithium, sodium, potassium, rubidium, and cesium; Preferably, in step (6), the precursor solution of the electronic auxiliary agent D is at least one selected from nitrate, carbonate, or bicarbonate aqueous solutions of lithium, sodium, potassium, rubidium, and cesium; Preferably, in step (6), the mass concentration of the precursor solution of the electronic auxiliary agent D is 10% - 50%.

6. The method according to any one of claims 1 - 5, wherein, in step (7), the conditions for spray drying are: the inlet air temperature is 200°C - 400°C, and the outlet temperature is 90°C - 180°C; Preferably, in step (8), the temperature for roasting is 300°C - 800°C, and the time is 2 h - 12 h; Preferably, for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(1 - 50):(0 - 30):(0.1 - 10):(0.5 - 15), and A and B are not both 0; Preferably, for the iron-based Fischer-Tropsch synthesis catalyst in the oxidized state, by mass ratio, Fe:A:B:C:D = 100:(5 - 40):(0 - 20):(3 - 10):(1 - 10), where A and B are not both 0.

7. A low CO 2 selectivity iron-based Fischer-Tropsch synthesis catalyst prepared by the method according to any one of claims 1-6, comprising a main active element Fe, a structural promoter A, a support promoter B, an electronic promoter D, and a doping element C wherein, the doping element C is one or more selected from Sm, Sc, Ga, Y, Zn, Mg, Be, Ba, Ca, Sr, and B, and by mass ratio, Fe:A:B:C:D = 100:(1 - 50):(0 - 30):(0.1 - 10):(0.5 - 15), where A and B are not both 0.

8. The iron-based Fischer-Tropsch synthesis catalyst according to claim 7, wherein, the structural auxiliary agent A is at least one selected from Mn, La, Zn, Cr, Ni, Co, Y, Sm, Zr, Cu, Ce, and Mo; the carrier auxiliary agent B is Si; Preferably, the doping element C is one or more selected from Ga, Sr, Zn, and Sm; Preferably, the electronic promoter D is at least one selected from lithium, sodium, potassium, rubidium, and cesium; Preferably, by mass ratio, Fe:A:B:C:D = 100:(5 - 40):(0 - 20):(3 - 10):(1 - 10), wherein A and B are not both 0.

9. Use of the iron-based Fischer-Tropsch synthesis catalyst according to claim 7 or 8 in reducing the CO 2 selectivity in the Fischer-Tropsch synthesis reaction.

10. The use according to claim 9, wherein, Before using the iron-based Fischer-Tropsch synthesis catalyst in the Fischer-Tropsch synthesis reaction, it is reduced for 10 h to 35 h under the following conditions: H 2 / CO = 1 to 100, 250 °C to 350 °C, and the space velocity is 3000 h -1 to 25000 h -1 , and the pressure is 0.05 Mpa to 5.0 Mpa; Preferably, the Fischer - Tropsch synthesis reaction is carried out in a slurry bed reactor; Preferably, the Fischer-Tropsch synthesis reaction is carried out under the conditions of a temperature of 250 °C to 350 °C, a space velocity of 5000 h -1 to 12000 h -1 , a pressure of 1.0 Mpa to 5.0 Mpa, an H 2 / CO ratio of 1 to 3, and a recycle ratio of 1 to 2.5.

Images