CN110614099B

CN110614099B - Iron-based Fischer-Tropsch synthesis catalyst, preparation method thereof and Fischer-Tropsch synthesis method

Info

Publication number: CN110614099B
Application number: CN201810638739.3A
Authority: CN
Inventors: 张魁; 林泉; 常海; 程萌; 吕毅军; 门卓武; 缪平
Original assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2022-10-04
Anticipated expiration: 2038-06-20
Also published as: CN110614099A

Abstract

The invention relates to the field of Fischer-Tropsch synthesis iron-based catalysts, and discloses a Fischer-Tropsch synthesis iron-based catalyst, a preparation method thereof and a Fischer-Tropsch synthesis method, wherein the method comprises the following steps: (1) Etching a first mixture of an oxide containing iron and an acid solution at 20-120 ℃ for at least 2 hours to obtain a dispersion slurry; (2) Mixing the dispersion slurry, a M salt, a copper salt, a potassium salt, a silicon-containing compound, and optionally water to obtain a second mixture; (3) Adjusting the pH value of the second mixture to 4-9 to obtain a third mixture; (4) Spray drying and calcining the third mixture. The preparation method provided by the invention has the following advantages: the preparation process flow is simple; no need of washing catalyst, low water consumption; compared with a melting method, the preparation process has mild conditions and low energy consumption; the prepared catalyst has higher reaction activity, high low-carbon olefin selectivity and high added value of products.

Description

Iron-based Fischer-Tropsch synthesis catalyst, preparation method thereof and Fischer-Tropsch synthesis method

Technical Field

The invention relates to the field of Fischer-Tropsch synthesis iron-based catalysts, in particular to a Fischer-Tropsch synthesis iron-based catalyst, a preparation method thereof and a Fischer-Tropsch synthesis method.

Background

Fischer-Tropsch synthesis, originally discovered by the german chemists Fischer and Tropsch together in the 20 th century, is an important route for the conversion of coal and natural gas into liquid fuels or high value-added chemical products. In the last 50 th century, sasol company in south Africa realized the industrial production of Fischer-Tropsch synthesis, and the catalyst used was a Fischer-Tropsch iron-based catalyst.

The reactors used in the Fischer-Tropsch synthesis mainly comprise a fixed bed reactor, a fluidized bed reactor and a slurry bed reactor. The preparation method of the Fischer-Tropsch synthesis iron-based catalyst mainly comprises the following three steps: precipitation, melting and impregnation. The iron-based catalyst prepared by the precipitation method is mainly used in the middle and low temperature Fischer-Tropsch synthesis technology in industry, and the products mainly comprise gasoline, diesel oil and Fischer-Tropsch wax. The iron-based catalyst prepared by the melting method is mainly used in the high-temperature Fischer-Tropsch synthesis technology in industry, and products mainly comprise olefin, gasoline and diesel oil. The iron-based catalyst prepared by the load method has no report of industrial use at present, and is mainly found in scientific research results of various laboratories at home and abroad.

CN104624196A provides a Fischer-Tropsch synthesis catalyst with high specific surface area, a preparation method and an application thereof, and the technical points are as follows: the silicon compound is used as a binder, and different types and contents of organic matters are added at different stages of the catalyst preparation by the traditional coprecipitation method, so that the dispersion degree of the whole system is improved, the surface area of the Fischer-Tropsch synthesis iron catalyst can be obviously improved, the pores of the catalyst are developed, and the activity of the catalyst is greatly improved. However, the reported catalyst preparation process is complicated, and in addition to the coprecipitation process, 2 drying processes and 1 auxiliary impregnation process are required, and in addition, the physical pores of the catalyst are excessively developed, which generally leads to the reduction of the physical abrasion of the catalyst.

CN101391219A provides a Fischer-Tropsch synthesis fused iron catalyst, a preparation method and an application thereof, and the technical key points are as follows: the iron element is taken as a main component, and the quantitative ratio Fe of the ferric iron to the bivalent iron is doubled ³⁺ /2Fe ²⁺ 0.5-1.5, and the catalyst is prepared by taking alumina, magnesia, potassium oxide, sodium oxide, calcium oxide and silicon oxide as auxiliary components and adopting a high-temperature melting-quenching method at 1500-1700 ℃, and has the characteristics of high strength, low methane selectivity and high olefin selectivity. However, the reported catalyst preparation conditions are severe, requiring high temperatures of 1500-1700 ℃The quenching operation is needed when the reaction is carried out under the condition, and the energy consumption is larger.

CN106000404A provides a preparation method and an application of an iron-based catalyst loaded by a carbon modified silica carrier for Fischer-Tropsch synthesis, and the technical points are as follows: firstly, adopting the steps of dipping, drying and roasting to finish the modification of a carbon source on the silicon dioxide with a primary macroporous structure to form a secondary porous structure; then, adding an iron source and an auxiliary agent to the modified silicon dioxide carrier by adopting an impregnation method, drying and roasting to prepare the catalyst, wherein the catalyst has excellent mechanical strength and hydrothermal stability. However, the provided catalyst is a supported catalyst, and the catalytic activity of the catalyst is low due to the limitation of the loading amount of the iron element.

The existing Fischer-Tropsch synthesis iron-based catalyst has the disadvantages of complex preparation process, harsh preparation conditions and low activity and selectivity of the prepared catalyst.

Disclosure of Invention

The invention aims to solve the problems of complex preparation process, harsh preparation conditions and low activity and selectivity of the prepared Fischer-Tropsch synthesis iron-based catalyst in the prior art, and provides a preparation method of the Fischer-Tropsch synthesis iron-based catalyst, the Fischer-Tropsch synthesis iron-based catalyst prepared by the method and a Fischer-Tropsch synthesis method. The preparation method of the iron-based catalyst for Fischer-Tropsch synthesis provided by the invention is simple in process flow and mild in condition, and the prepared catalyst has higher reaction activity and low-carbon olefin selectivity.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing an iron-based fischer-tropsch catalyst, the method comprising:

(1) Etching the first mixture containing iron oxide and an acid solution at 20-120 ℃ for at least 2 hours to obtain a dispersion slurry;

(2) Mixing the dispersion slurry, a salt of M, a copper salt, a potassium salt, a silicon-containing compound and optionally water to obtain a second mixture, wherein M is selected from at least one of Ti, V, cr, mn, co, ni, zn, al and Nd;

(3) Adjusting the pH value of the second mixture to 4-9 to obtain a third mixture;

(4) Spray drying and calcining the third mixture.

The second aspect of the invention provides the Fischer-Tropsch synthesis iron-based catalyst prepared by the preparation method.

In a third aspect, the invention provides a fischer-tropsch synthesis process comprising:

will contain CO and H under Fischer-Tropsch synthesis conditions ₂ The synthesis gas contacts with a catalyst to carry out Fischer-Tropsch synthesis reaction, wherein the catalyst is the Fischer-Tropsch synthesis iron-based catalyst provided by the invention.

The preparation method of the iron-based catalyst for Fischer-Tropsch synthesis provided by the invention has the following advantages: (1) the preparation process flow is simple; (2) the catalyst does not need to be washed, and the water consumption is low; (3) Compared with a melting method, the preparation process has mild conditions and low energy consumption; (4) The prepared catalyst has higher reaction activity, high low-carbon olefin selectivity and high added value of products.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.

The invention provides a preparation method of an iron-based Fischer-Tropsch synthesis catalyst, which comprises the following steps:

(4) Spray drying and calcining the third mixture.

According to the present invention, the iron oxide may be at least one of ferrous oxide, ferric oxide and ferroferric oxide, and preferably, the iron oxide is ferroferric oxide.

According to a preferred embodiment of the present invention, the average particle size of the ferroferric oxide is not more than 1.5 microns, and further preferably, the average particle size of the ferroferric oxide is 0.5-1.2 microns.

In the present invention, unless otherwise specified, the average particle diameter refers to a linear average particle diameter.

In the present invention, preferably, the acid is at least one selected from the group consisting of nitric acid, hydrochloric acid and acetic acid, more preferably nitric acid and/or acetic acid, and still more preferably nitric acid and acetic acid. In the research process, the inventor finds that the coordination of nitric acid and acetic acid is more favorable for improving the activity and the selectivity of the prepared catalyst for low-carbon olefin, and is more favorable for reducing the dosage of nitric acid and pollution.

According to a preferred embodiment of the invention, the weight ratio of nitric acid to acetic acid is 1: (1-3), more preferably 1: (1.5-2.5). Further preferably, the concentration of nitric acid in the acid solution is 2.5 to 20 wt%.

According to the present invention, the solid content of the iron oxide in the first mixture may be 30 to 60% by weight.

According to the present invention, preferably the pH of the first mixture is between 0.5 and 6, further preferably the pH of the first mixture is between 0.5 and 4, and even further preferably the pH of the first mixture is between 0.5 and 2. The preferred embodiment is more beneficial to improving the activity and the selectivity of the prepared catalyst for low-carbon olefin.

The amount of the acid solution used is not particularly limited in the present invention, and a person skilled in the art can select an appropriate amount of the acid to be added by limiting the pH of the first mixture.

According to a preferred embodiment of the present invention, the first mixture is etched at 50-90 ℃ for 5-48 hours, preferably 16-40 hours in step (1). In the research process, the inventor of the invention finds that the prepared catalyst has higher activity and lower olefin selectivity by etching the oxide containing iron in the step (1).

According to the present invention, preferably, the etching in step (1) is performed under a hermetic condition.

Water can be selectively added or not added in the step (2) of the invention, and the skilled person can select the water appropriately according to the actual situation, when the water in the dispersion slurry is enough to dissolve the M salt, the copper salt, the potassium salt and the silicon-containing compound, the water does not need to be added, otherwise, the water needs to be added.

Preferably, the dispersion slurry, the M salt, the copper salt, the potassium salt, the silicon-containing compound and water are mixed in the step (2), and further preferably, the dispersion slurry, the M salt solution, the copper salt solution, the potassium salt solution and the silicon-containing compound solution (i.e., water is introduced in a manner of being prepared into a solution with the M salt, the copper salt, the potassium salt and the silicon-containing compound) are mixed in the step (2).

According to a preferred embodiment of the present invention, M is selected from at least one of Mn, co, ni and Zn, preferably Mn and/or Zn, more preferably Zn.

Preferably, the M salt of the present invention may be a nitrate and/or chloride of M, and further preferably, the M salt is a nitrate of M.

Preferably, the copper salt may be at least one of copper nitrate, a hydrate of copper nitrate, copper sulfate and a hydrate of copper sulfate, preferably copper nitrate and/or a hydrate of copper nitrate.

According to the method of the present invention, the potassium salt in step (2) may be an inorganic potassium salt or an organic potassium salt, and in the present invention, the potassium salt is preferably one or more of potassium carbonate, potassium sulfate, potassium chloride and potassium nitrate, and more preferably potassium nitrate.

According to the method of the present invention, it is preferable that in the step (2), the silicon-containing compound is at least one selected from the group consisting of potassium silicate, silica sol, potassium-containing silica sol, water-soluble silica and sodium silicate.

According to the method provided by the invention, preferably, dispersingThe dosage mass ratio of the slurry, the M salt, the copper salt, the potassium salt and the silicon-containing compound is 100: (0.1-10): (0.6-15): (0.01-10): (5-27), preferably 100: (2-9): (4-12): (3-5.5): (15-24), more preferably 100: (4.8-8.5): (5.5-11): (3.7-5.4): (16.5-24) wherein the dispersion slurry is in terms of Fe, the salt of M is in terms of M, the copper salt is in terms of Cu, the potassium salt is in terms of K, and the silicon-containing compound is in terms of SiO ₂ And (6) counting.

According to the present invention, preferably, the solids content of the second mixture is 30 to 60% by weight.

According to the present invention, in step (3), the substance to be added for adjusting the pH is not particularly limited as long as the pH of the second mixture is adjusted to 4 to 9, and preferably, in step (3), the pH is adjusted by adding at least one of aqueous ammonia, an ammonium carbonate solution and an ammonium bicarbonate solution to the second mixture. It is further preferred to adjust the pH by adding an ammonium carbonate solution. Most preferably, the concentration of the ammonium carbonate solution is 30-60% by weight.

Preferably, in step (3), the pH of the second mixture is adjusted to 5 to 8, and further preferably, the pH of the second mixture is adjusted to 6 to 7.5. By adopting the preferred embodiment, the activity of the catalyst and the selectivity of the low-carbon olefin are improved.

According to a most preferred embodiment of the present invention, the method comprises:

(1) Mixing ferroferric oxide with the average particle size of 0.5-1.2 microns and a nitric acid/acetic acid solution to obtain a first mixture, wherein the pH value of the first mixture is 0.5-2, and etching the first mixture at the temperature of 50-90 ℃ for 5-48 hours to obtain dispersed slurry;

(2) Mixing the dispersion slurry, a solution of an M salt, a solution of a copper salt, a solution of a potassium salt, a solution of a silicon-containing compound, and optionally water to obtain a second mixture, wherein M is selected from at least one of Mn, co, ni and Zn;

(3) Adding ammonium carbonate into the second mixture to adjust the pH value to 5-8 to obtain a third mixture;

(4) Spray drying and calcining the third mixture.

According to the method of the present invention, preferably in step (4), the spray-drying conditions include: the inlet air temperature is 220-300 ℃, and the outlet air temperature is 100-140 ℃.

According to the method of the present invention, in the preferable step (4), the conditions for calcination include: the roasting temperature is 280-400 ℃, the roasting time is 2-10 hours, and more preferably, the roasting temperature is 280-350 ℃, and the roasting time is 4-8 hours.

In a second aspect, the invention provides an iron-based Fischer-Tropsch synthesis catalyst prepared by the preparation method. The catalyst prepared by the method provided by the invention has the advantages of high catalytic activity and good selectivity of low-carbon olefin.

In a third aspect, the invention provides a fischer-tropsch synthesis process comprising: will contain CO and H under Fischer-Tropsch synthesis conditions ₂ The synthesis gas contacts with a catalyst to carry out Fischer-Tropsch synthesis reaction, wherein the catalyst is the Fischer-Tropsch synthesis iron-based catalyst provided by the invention.

According to the Fischer-Tropsch synthesis method provided by the invention, preferably, the Fischer-Tropsch synthesis conditions comprise: the temperature is 230 to 300 ℃ and the pressure is 0.1 to 5.5MPa, more preferably 1 to 4MPa.

According to the Fischer-Tropsch synthesis method provided by the invention, CO and H are preferable ₂ The space velocity of the feed of the synthesis gas of (2) is 1000 to 20000ml/g-cat./h, more preferably 3000 to 10000ml/g-cat./h.

According to the Fischer-Tropsch synthesis method provided by the invention, preferably, H in the synthesis gas ₂ The molar ratio of CO to CO is 1.5-2.5:1.

in the present invention, the Fischer-Tropsch synthesis can be carried out in a fixed bed reactor or a slurry bed reactor.

The present invention will be described in detail below by way of examples.

The product obtained by Fischer-Tropsch synthesis was analyzed by a gas chromatograph model 7890 from Agilent under the following conditions: at 25 deg.C and normal pressure.

CO conversion, CO ₂ The selectivity is calculated by the following formula:

CO conversion = (moles CO consumed/moles total CO fed) × 100%;

CO ₂ selectivity = (CO formation) ₂ Moles/moles of CO consumed) × 100%;

C _2- C ₄ O/P refers to the molar ratio of olefin to alkane in the products C2-C4.

The starting materials in the examples and comparative examples were all commercially available.

Example 1

(1) 100g of ferroferric oxide (average particle size of about 1 micron, specific surface area of 0.2 m) ² And/g) and a nitric acid/acetic acid mixed acid solution (the mass ratio of nitric acid to acetic acid is 1 ² /g)；

(2) To the dispersion slurry were added 37.5g of a zinc nitrate solution (12.5 g of zinc nitrate), 36.7g of a copper nitrate solution (11.7 g of copper nitrate), 35.1g of a potassium nitrate solution (10.1 g of potassium nitrate), and 61g of silica sol (the silica content was 20 wt%) in this order, followed by mixing to obtain a second mixture;

(3) Adding an ammonium carbonate solution with the concentration of 30 wt% into the second mixture, and adjusting the pH value of the second mixture to 6.5 to obtain a third mixture;

(4) Inputting the third mixture into a spray dryer, and carrying out spray drying under the conditions that the inlet air temperature is 290 ℃ and the outlet air temperature is 105 ℃; the collected microspheres were calcined at 300 ℃ for 5 hours to obtain catalyst C1, the specific surface area of which was measured to be 25.2m ² /g。

Comparative example 1

505g of ferric nitrate nonahydrate, 12.5g of zinc nitrate and 11.7g of copper nitrate were dissolved in deionized water to prepare a 2.5 liter solution, and 200g of sodium carbonate was dissolved in deionized water to prepare a 2.5 liter solution. And (3) carrying out cocurrent precipitation on the mixed solution of the ferric nitrate, the zinc nitrate and the copper nitrate and a sodium carbonate solution, wherein the precipitation temperature is 80 ℃, and the pH value is controlled to be 6.5. After the precipitation reaction, the slurry is separated by a filter and washed to remove sodium ions until the conductivity of the filtrate is less than 1000 mus/cm, and a catalyst precursor filter cake 1 is obtained. And adding 300g of deionized water into the catalyst precursor filter cake 1 for pulping, wherein the pulping temperature is 30 ℃, the stirring speed is 800rpm, and the pulping time is 30min, so as to obtain the slurry. Fully dissolving 10.1g of potassium nitrate into 25g of water, and adding the potassium nitrate into the slurry; 61g of silica sol (silica content 20 wt%) was added to the slurry, and after thorough mixing, spray-dried and calcined as described in example 1, to obtain catalyst D1.

Comparative example 2

The process of example 1 was followed except that step (1) was carried out as follows: mixing 100g of ferroferric oxide with 120g of deionized water to obtain a first mixture, putting the first mixture into a closed container, and preserving heat at 80 ℃ for 24 hours to obtain dispersed slurry.

Catalyst D2 was obtained.

Comparative example 3

The process of example 1 was followed except that the pH adjustment of step (3) was not included and the second mixture was directly fed to the spray dryer. Catalyst D3 was obtained.

Example 2

(1) 100g of ferroferric oxide (average particle size of about 1 micron, specific surface area of 0.2 m) ² /g) of a nitric acid/acetic acid mixed acid solution (mass ratio of nitric acid to acetic acid is 1.5, mass concentration of nitric acid is 18% by weight) to obtain a first mixture, adjusting the pH of the first mixture to 1, placing the first mixture in a closed container, and performing heat preservation (etching) at 50 ℃ for 40 hours to obtain a dispersion slurry;

(2) To the dispersion slurry were added 33g of a zinc nitrate solution (8 g of zinc nitrate), 33g of a copper nitrate solution (8 g of copper nitrate), 23g of a potassium nitrate solution (8 g of potassium nitrate), and 70g of silica sol (the silica content was 20% by weight) in this order, followed by mixing to obtain a second mixture;

(3) Adding an ammonium carbonate solution with the concentration of 30 wt% into the second mixture, and adjusting the pH value of the second mixture to 6 to obtain a third mixture;

(4) Inputting the third mixture into a spray dryer, and carrying out spray drying under the conditions that the inlet air temperature is 290 ℃ and the outlet air temperature is 105 ℃; the collected microspheres were calcined at 350 ℃ for 4 hours to obtain catalyst C2.

Example 3

(1) 100g of ferroferric oxide (average particle size of about 1 micron, specific surface area of 0.2 m) ² /g) of a nitric acid/acetic acid mixed acid solution (mass ratio of nitric acid to acetic acid is 1;

(2) To the dispersion slurry were added 39g of a zinc nitrate solution (14 g of zinc nitrate), 36.7g of a copper nitrate solution (6.2 g of copper nitrate), 32g of a potassium nitrate solution (7 g of potassium nitrate), and 85g of silica sol (silica content: 20% by weight) in this order, followed by mixing to obtain a second mixture;

(3) Adding an ammonium carbonate solution with the concentration of 30 wt% into the second mixture, and adjusting the pH value of the second mixture to 7.5 to obtain a third mixture;

(4) Inputting the third mixture into a spray dryer, and carrying out spray drying under the conditions that the inlet air temperature is 290 ℃ and the outlet air temperature is 105 ℃; the collected microspheres were calcined at 280 ℃ for 8 hours to obtain catalyst C3.

Example 4

The procedure of example 1 was followed except that, in the nitric acid/acetic acid mixed acid solution used in step (1), the mass concentration of nitric acid was 2.5% by weight, and the pH of the first mixture was adjusted to 4. Catalyst C4 is obtained.

Example 5

The procedure of example 1 was followed except that, in the step (1), the temperature was maintained (etching) at 40 ℃ for 24 hours. Catalyst C5 was obtained.

Example 6

The procedure of example 1 was followed except that, in the step (1), the temperature was maintained (etching) at 100 ℃ for 24 hours. Catalyst C6 was obtained.

Example 7

The procedure of example 1 was followed except that, in the step (1), the acid solution used was an acetic acid solution having a mass concentration of 20% by weight. Catalyst C7 was obtained.

Example 8

The process of example 1 was followed except that zinc nitrate was replaced with an equal amount of manganese nitrate based on the mass of the metal. Catalyst C8 was obtained.

Example 9

The process of example 1 was followed except that the pH of the second mixture was adjusted to 5. Catalyst C9 was obtained.

Example 10

The procedure of example 1 was followed except that ferroferric oxide having an average particle size of about 35 μm was used. Catalyst C10 was obtained.

Test example 1

The catalysts provided in the above examples and comparative examples are respectively used for carrying out Fischer-Tropsch synthesis reaction on a laboratory fixed bed reactor device.

The catalyst particles are 53-150 mu m, and the molar ratio of the synthetic gas is H ₂ The reaction temperature is 270 ℃, the reaction space velocity is 6000ml/g-cat./h, and the reaction pressure is 2.3MPa. The results are shown in Table 1.

TABLE 1

As can be seen from the data in the above examples and tables, the catalyst preparation method provided by the invention has simple process flow; the catalyst does not need to be washed, and the water consumption is low; compared with a melting method, the process conditions are milder, and the energy consumption is low; the prepared catalyst has higher reaction activity, higher low-carbon olefin selectivity and high added value of products.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A preparation method of an iron-based Fischer-Tropsch synthesis catalyst comprises the following steps:

(2) Mixing the dispersion slurry, a salt of M, a copper salt, a potassium salt, a silicon-containing compound and optionally water to obtain a second mixture, wherein M is selected from at least one of Ti, V, cr, mn, co, ni, zn, al and Nd; the dosage mass ratio of the dispersing slurry, the M salt, the copper salt, the potassium salt and the silicon-containing compound is 100: (2-9): (4-12): (3-5.5): (15-24) wherein the dispersion slurry is in terms of Fe, the salt of M is in terms of M, the copper salt is in terms of Cu, the potassium salt is in terms of K, and the silicon-containing compound is in terms of SiO ₂ Counting;

(4) Spray drying and calcining the third mixture.

2. The production method according to claim 1, wherein the oxide of iron is ferroferric oxide; the acid is selected from at least one of nitric acid, hydrochloric acid and acetic acid.

3. The preparation method of claim 2, wherein the average grain size of the ferroferric oxide is not more than 1.5 microns.

4. The preparation method according to claim 3, wherein the average particle size of the ferroferric oxide is 0.5-1.2 microns.

5. The production method according to claim 2, wherein the acid is nitric acid and/or acetic acid.

6. The production method according to claim 5, wherein the acid is nitric acid and acetic acid, and the weight ratio of nitric acid to acetic acid is 1: (1-3).

7. The method according to claim 5, wherein the concentration of the nitric acid in the acid solution is 2.5 to 20% by weight.

8. The production method according to any one of claims 1 to 7, wherein the pH of the first mixture is 0.5 to 6.

9. The method of claim 8, wherein the pH of the first mixture is 0.5 to 4.

10. The method of claim 9, wherein the pH of the first mixture is 0.5-2.

11. The production method according to any one of claims 1 to 7, wherein the first mixture is etched at 50 to 90 ℃ for 5 to 48 hours in step (1).

12. The method of claim 11, wherein the first mixture is etched at 50-90 ℃ for 16-40 hours in step (1).

13. The production method according to any one of claims 1 to 7, wherein M is at least one selected from Mn, co, ni and Zn.

14. The method of claim 13, wherein M is selected from Mn and/or Zn.

15. The production method according to claim 14, wherein M is Zn.

16. The production method according to any one of claims 1 to 7, wherein the silicon-containing compound is at least one selected from the group consisting of potassium silicate, silica sol, potassium-containing silica sol, water-soluble silica and sodium silicate.

17. The production method according to any one of claims 1 to 7, wherein the solid content of the second mixture is 30 to 60% by weight.

18. The production method according to any one of claims 1 to 7, wherein in step (3), the pH is adjusted by adding at least one of aqueous ammonia, an ammonium carbonate solution and an ammonium bicarbonate solution to the second mixture.

19. The production method according to claim 18, wherein in step (3), the pH is adjusted by adding an ammonium carbonate solution to the second mixture.

20. The production method according to any one of claims 1 to 7, wherein the pH of the second mixture is adjusted to 5 to 8.

21. The method of claim 20, wherein the pH of the second mixture is adjusted to 6-7.5.

22. An iron-based fischer-tropsch catalyst prepared according to the method of any one of claims 1 to 21.

23. A process for fischer-tropsch synthesis, the process comprising: under the condition of Fischer-Tropsch synthesis, the catalyst contains CO and H ₂ The synthesis gas of (a) is contacted with a catalyst to perform a fischer-tropsch synthesis reaction, wherein the catalyst is the iron-based fischer-tropsch synthesis catalyst of claim 22.

24. The process of claim 23, wherein the fischer-tropsch synthesis conditions comprise: the temperature is 230-300 ℃, and the pressure is 0.1-5.5MPa;

CO and H ₂ The feeding space velocity of the synthetic gas is 1000-20000 ml/g-cat/h;

h in synthesis gas ₂ The molar ratio of CO to CO is 1.5-2.5:1.