Preparation method of iron-based catalyst, iron-based catalyst and application thereof

Abstract

The present application relates to a kind of preparation method of iron-based catalyst, iron-based catalyst and its application, the catalyst is to Fe salt, the salt of auxiliary A is mixed and grinded, then the solution of the salt of auxiliary B is added, and hydrothermal treatment is carried out, and precursor is obtained by washing, drying;Auxiliary C is loaded on the above-mentioned precursor, and iron-based catalyst is obtained by drying, calcining.The catalyst is applied to water vapor shift reaction, is suitable for the condition of low water-gas ratio, can improve the hydrogen yield of water vapor shift, and reduces the methane selectivity, while the heat-resistant activity of catalyst is good, and the specific surface area and activity are maintained well after high-temperature treatment.

Description

Technical Field

[0001] This invention relates to iron-based catalysts for water-gas shift reactions, specifically, a method for preparing an iron-based catalyst, the resulting iron-based catalyst, and its applications. Background Technology

[0002] Against the backdrop of carbon neutrality, hydrogen energy has garnered significant attention as a potential alternative to traditional fossil fuels. Over the past decade, the hydrogen economy has developed rapidly. Hydrogen fuel has a gross calorific value (GCADE) of 141.8 MJ / kg, more than twice that of natural gas (54.0 MJ / kg), making it economically viable. While hydrogen resources are abundant, such as water and biomass, most hydrogen today is extracted from traditional fossil fuels, such as crude oil and natural gas. Currently, steam reforming (SRM) of methane is the main mature industrial hydrogen production technology. To improve hydrogen yield, a water-gas shift reaction (WGS) is required after the reforming process to react excess CO and further increase the H2 content in the atmosphere, thereby increasing hydrogen production. In recent years, another important application of WGS has been in the field of new energy vehicles. The electrode materials of fuel cells are mainly composed of Pt, which is easily deactivated in the presence of carbon monoxide. Therefore, placing a WGS reactor before the fuel cell converts carbon monoxide into hydrogen and CO2. Thus, the water-gas shift reaction (WGS) plays a crucial industrial role in regulating and increasing H2 concentration.

[0003] Commercial iron oxide catalysts using chromium oxide as a structural aid have been used for over 60 years. Besides preventing the sintering of iron oxide crystals, Cr2O3 / CrO3 can also enhance the inherent catalytic activity of Fe2O3. Under the high-temperature hydrothermal conditions during the reaction, Cr2O3 inhibits iron oxide grain growth and avoids a significant reduction in the catalyst's specific surface area. Although chromium oxides have proven to be excellent aids, hexavalent chromium is a heavy metal toxic to humans, organisms, and cells, and a serious environmental pollutant. Its water solubility allows it to leach from the catalyst via condensed steam or cold water, resulting in high costs for the disposal of both fresh and spent commercial high-temperature conversion Fe-Cr catalysts. Due to the toxicity and environmental impact of hexavalent chromium (Cr6+), there is a need to develop a highly stable and highly active chromium-free catalyst for HT-WGSR.

[0004] CN107649142B discloses a low-density iron-chromium CO conversion catalyst, which uses Mn, Mg, and Cr as promoters to improve the high-temperature stability of the Fe-based catalyst. The catalyst is composed of Fe₂O₃, Cr₂O₃, CuO, and Mn. x O YThe mixture, by weight percentage, has the following main components: Fe2O3 70%–92%, Cr2O3 4%–15%, CuO 0.5%–10%, M x O Y 4% to 15%, where M is one or more of Ti, Mg, Mn, Al, Ca, and Si.

[0005] CN103272600B discloses a supported copper-iron-water gas shift catalyst, which uses modified bauxite as a support and Cu and Fe as active components. The content of copper oxide is 10-15 wt% and the content of iron oxide is 5-30 wt% by mass percentage of oxides. The supported copper-iron-water gas shift catalyst is prepared by co-current co-precipitation method.

[0006] CN104014345B discloses a CuO-CeO2 catalyst for water-gas shift reaction. The obtained CuO-CeO2 catalyst is composed of active components CuO and CeO2 support, wherein the CuO content is 5-30 wt%; it is prepared by complex deposition precipitation method.

[0007] Problems reported in literature and patents regarding water-gas shift reactions include severe methanation side reactions, low space-time yield, high catalyst cost, and serious chromium contamination. Therefore, developing chromium-free, highly selective catalysts with simple preparation processes while ensuring hydrothermal stability is both a challenge and a direction for achieving the industrial application of green shift catalysts. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing an iron-based catalyst, the resulting iron-based catalyst, and its application, based on existing technologies, in order to solve the problem of high cost in the preparation process of iron-based catalysts in existing technologies.

[0009] The first aspect of this invention provides a method for preparing an iron-based catalyst, comprising the following steps:

[0010] (1) Mix and grind Fe salt and auxiliary agent A salt to obtain mixture I;

[0011] Additive A is selected from one or more of Mn, Mo, Co, Al, Ce, La, V, Ni, Mg, and Ca, and the elemental molar ratio of Fe to additive A is 2:1-30:1;

[0012] (2) After mixing the precipitant with the mixture I obtained in step (1), continue grinding for a certain period of time to obtain mixture II;

[0013] (3) Provide a solution containing auxiliary agent B salt, and add it to the mixture II obtained in step (2), and continue to grind and mix for a certain period of time to obtain mixture III;

[0014] Additive B is selected from one or more of Cu, Ni, Pt, and Pd, and the elemental molar ratio of Fe to additive B is 10:1-200:1;

[0015] (4) The mixture III obtained in step (3) is sent to a hydrothermal reactor for hydrothermal treatment, and then washed and dried to obtain the precursor;

[0016] (5) The promoter C is loaded onto the above precursor, dried and calcined to obtain an iron-based catalyst. The promoter C is selected from at least one of the alkali metals Na, K and Cs.

[0017] In one embodiment of the present invention, a ball mill is used for grinding in step (1), and the grinding time is 2 min to 60 min;

[0018] In step (2), a ball mill is used for grinding, and the grinding time is 2 min to 60 min;

[0019] In step (3), a ball mill is used for grinding, and the grinding time is 2 min to 60 min.

[0020] In one embodiment of the present invention, the auxiliary agent A is selected from one or more of Mn, Al, Ni, and Ce;

[0021] The Fe salt and the auxiliary agent A salt are each independently selected from at least one of the following: nitrate, sulfate, formate, acetate, and halide of Fe and auxiliary agent A.

[0022] In one embodiment of the present invention, in step (2), the precipitant is selected from one or more of ammonium carbonate, urea, sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, and ammonium hydroxide;

[0023] The molar amount of precipitant is 1-5 times the theoretical stoichiometric ratio of the total number of metal atoms of Fe, additive A, and additive B.

[0024] In one embodiment of the present invention, in step (3), the auxiliary agent B salt is dissolved in deionized water to obtain a solution containing the auxiliary agent B salt, wherein the auxiliary agent B salt is selected from at least one of the following: nitrate, sulfate, formate, acetate, and halide of the auxiliary agent B;

[0025] In the solution containing salt of additive B, the concentration of additive B element is 10-100 mol / L, preferably 20-50 mol / L;

[0026] The molar ratio of Fe to auxiliary agent B is 10:1 to 100:1, based on elemental composition.

[0027] In a preferred embodiment, the additive B is selected from at least one of Cu and Ni.

[0028] In one embodiment of the present invention, in step (4), the reaction temperature of the hydrothermal treatment is 80-250°C and the reaction time is 1-72h.

[0029] In a preferred embodiment of the present invention, in step (4), the hydrothermal treatment is microwave-assisted hydrothermal treatment, and the conditions for microwave-assisted hydrothermal treatment are: reaction temperature 100-250℃, microwave output power 500-1500W, and reaction time 1-8h.

[0030] In one embodiment of the present invention, in step (4), the drying temperature is 60-150℃ and the drying time is 0.5-8h.

[0031] Preferably, the drying temperature is 80-120℃ and the drying time is 1-4h.

[0032] In one embodiment of the present invention, the amount of additive C added in step (5) is 0.1-10% by mass fraction of the iron-based catalyst, based on oxides.

[0033] In one embodiment of the present invention, the method of loading the additive C onto the precursor is as follows: mechanically mixing at least one of the oxide, inorganic salt, and organometallic compound of the additive C with the precursor.

[0034] In another embodiment of the present invention, the method of loading the auxiliary agent C onto the precursor is to impregnate the precursor with a solution containing at least one inorganic salt or organometallic compound of the auxiliary agent C.

[0035] In one embodiment of the present invention, in step (5), the drying temperature is 60-150℃, the drying time is 0.5h-8h, the calcination temperature is 200-600℃, and the calcination time is 1-10h.

[0036] Preferably, the drying temperature is 80-120℃, and the drying time is 1-4 hours.

[0037] Preferably, the roasting temperature is 300-550℃ and the roasting time is 1-8h.

[0038] In one embodiment of the present invention, when the precursor is impregnated with a solution containing at least one inorganic salt or organometallic compound containing auxiliary agent C, rotary evaporation drying is preferably performed before drying. The rotary evaporation drying temperature is 30-80°C, the vacuum degree is 0.1 MPa, and the rotary evaporation drying time is 0.2-2 h.

[0039] Using the preparation method of this invention, the auxiliary agent A forms a solid solution with the Fe-based catalyst, thereby promoting the Fe... 2+ with Fe 3+The redox conversion is achieved. Furthermore, additive A acts as a physical separator for the active phase, preventing catalyst sintering and improving stability. Further, additive C is used in this invention for surface modification, adjusting the surface acidity and alkalinity of the iron-based catalyst to promote the water-gas shift reaction.

[0040] The second aspect of the present invention provides an iron-based catalyst obtained by the above preparation method, wherein, based on the iron-based catalyst as a whole, the Fe content is 70-95% based on oxides, the content of promoter A is 1-20%, the content of promoter B is 0.1-10%, and the content of promoter C is 0.1-10%; promoter A is selected from one or more of Mn, Mo, Co, Al, Ce, La, V, Ni, Mg, and Ca, promoter B is selected from one or more of Cu, Ni, Pt, and Pd, and promoter C is selected from at least one of alkali metals Na, K, and Cs.

[0041] A third aspect of this invention provides a method for applying the iron-based catalyst obtained by the above preparation method. The iron-based catalyst is packed in a fixed-bed reactor for a water-gas shift reaction, and the reaction conditions are: pressure 0.1-5 MPa, temperature 300-500 °C, and volume hourly space velocity 2000-100000 h⁻¹. -1 The ratio of nH2O to nCO in the raw material gas is 2.4-4.

[0042] In one embodiment of the present invention, the iron-based catalyst is subjected to a reduction pretreatment before use. The pretreatment atmosphere is H2 / CO / H2O or H2 / CO / H2O / CO2, the pretreatment temperature is 200-600℃, the pretreatment time is 1-12h, the pretreatment pressure is 0.1-1MPa, and the pretreatment volume hourly space velocity is 500-20000h⁻¹. -1 .

[0043] Features of this invention:

[0044] (1) This invention utilizes a mechanical solid-phase reaction with few solvents, that is, it adopts a simple and efficient preparation method with few solvents. On the one hand, it omits the neutralization and aging steps of iron-based catalyst precipitation in the prior art, shortening the preparation time. On the other hand, it reduces the solvent cost in the preparation process and reduces the wastewater treatment cost.

[0045] (2) The hydrothermal treatment process of the present invention has a fast nucleation rate, uniform dispersion, high nucleation rate, low energy consumption, and short time consumption.

[0046] (3) The present invention uses surface modification to obtain a medium-alkaline active phase with suitable adsorption effect, which exhibits excellent performance of high activity and high stability in the field of water vapor conversion.

[0047] (3) The Fe-based catalyst of the present invention is inexpensive and suitable for low water-to-gas ratio conditions. It can improve the hydrogen yield of water-to-gas shift and reduce methane selectivity. At the same time, the catalyst has good heat resistance and its specific surface area and activity remain good after high-temperature treatment. Detailed Implementation

[0048] The following embodiments will further illustrate the present invention. However, the present invention is not limited thereto.

[0049] BET specific surface area and pore volume tests were performed on the catalysts in the examples and comparative examples:

[0050] The specific surface area and pore volume of the catalyst were analyzed using low-temperature N2 isothermal adsorption-desorption and conventional BET calculations. Before analysis, the sample was dried at 120℃ for 2 hours, followed by vacuum treatment at 300℃. High-purity nitrogen was used as the adsorption medium. Adsorption / desorption experiments were conducted under liquid nitrogen cooling conditions (-196℃).

[0051] Example 1

[0052] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0053] (1) Mix 20g of ferric nitrate nonhydrate and 1.86g of aluminum nitrate nonhydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0054] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0055] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 15 minutes.

[0056] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0057] (5) Dissolve 0.11 g of cesium carbonate in 20 mL of deionized water to obtain a cesium carbonate solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, first dry it by rotary evaporation at 55 °C and 0.1 MPa for 1 h. Then dry the sample at 120 °C for 2 h and calcine it at 500 °C for 2 h to obtain catalyst C-1. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0058] Example 2

[0059] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0060] (1) Mix 20g of ferric nitrate nonahydrate and 1.42g of manganese nitrate hexahydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0061] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0062] (3) Dissolve 0.7g of nickel nitrate hexahydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 5 minutes.

[0063] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0064] (5) Dissolve 0.12 g of potassium hydroxide in 20 mL of deionized water to obtain a potassium hydroxide solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, first dry it by rotary evaporation at 50 °C and 0.1 MPa for 1 h. Then dry the sample at 120 °C for 2 h and calcine it at 500 °C for 2 h to obtain catalyst C-2. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0065] Example 3

[0066] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0067] (1) Mix 20g of ferric nitrate nonahydrate and 1.44g of nickel nitrate hexahydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0068] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0069] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 5 minutes.

[0070] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0071] (5) Dissolve 0.14 g of potassium carbonate in 20 mL of deionized water to obtain a potassium carbonate solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, dry it by rotary evaporation for 4 h at a temperature of 55 °C and a vacuum of 0.1 MPa. The obtained sample is then dried at 120 °C for 2 h and calcined at 500 °C for 2 h to obtain catalyst C-3. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0072] Example 4

[0073] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0074] (1) Mix 20g of ferric nitrate nonahydrate and 0.72g of nickel nitrate hexahydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0075] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0076] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 15 minutes.

[0077] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0078] (5) Dissolve 0.11 g of cesium carbonate in 20 mL of deionized water to obtain a cesium carbonate solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, first dry it by rotary evaporation at 45 °C and 0.1 MPa for 1 h. Then dry the sample at 120 °C for 2 h and calcine it at 500 °C for 2 h to obtain catalyst C-4. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0079] Example 5

[0080] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0081] (1) Mix 20g of ferric nitrate nonahydrate and 0.72g of nickel nitrate hexahydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0082] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0083] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 5 minutes.

[0084] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0085] (5) Dissolve 0.14 g of potassium carbonate in 20 mL of deionized water to obtain a potassium carbonate solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, first dry it by rotary evaporation at 55 °C and 0.1 MPa for 1 h. Then dry the sample at 120 °C for 2 h and calcine it at 500 °C for 2 h to obtain catalyst C-5. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0086] Example 6

[0087] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0088] (1) Mix 20g of ferric nitrate nonahydrate, 1.1g of cerium nitrate hexahydrate, and 0.72g of nickel nitrate hexahydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0089] (2) Add 15g NaOH and 15g Na2CO3 to the powder obtained in step (1) and continue grinding for 15 minutes.

[0090] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 5 minutes.

[0091] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it 10 times with 500 ml of deionized water each time, and dry it at 120°C for 4 hours to obtain the precursor.

[0092] (5) Dissolve 0.14 g of potassium carbonate in 20 mL of deionized water to obtain a potassium carbonate solution. Impregnate the precursor obtained in step (4) with this solution. After impregnation, first dry it by rotary evaporation at 50 °C and 0.1 MPa for 1 h. Then dry the sample at 120 °C for 2 h and calcine it at 500 °C for 2 h to obtain catalyst C-6. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0093] Example 7

[0094] The preparation process of the iron-based catalyst in this embodiment is as follows:

[0095] (1) Mix 20g of ferric nitrate nonhydrate and 1.86g of aluminum nitrate nonhydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0096] (2) Add 20g of ammonium hydroxide to the powder obtained in step (1) and continue grinding for 15 minutes.

[0097] (3) Dissolve 0.40g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 15 minutes.

[0098] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0099] (5) After mixing 0.103g of cesium carbonate with the precursor obtained in step (4), the mixture was ground in a ball mill for 20 min. The resulting sample was dried at 120℃ for 2 h and then calcined at 500℃ for 2 h to obtain catalyst C-7. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0100] Comparative Example 1

[0101] This comparative example uses a precipitation method to obtain an iron-based catalyst:

[0102] Solution A was prepared by dissolving 20 g of ferric nitrate nonahydrate, 1.44 g of nickel nitrate hexahydrate, and 0.60 g of copper nitrate trihydrate in 150 mL of deionized water. Solution B was prepared by dissolving 40 g of ammonia solution (25%–28% by mass) in 70 mL of deionized water. Solution B was added to solution A using a peristaltic pump at a rate of 5 mL / min. After stirring and aging at room temperature for 2 h, the solution was washed three times with deionized water, filtered three times, and dried at 120 °C for 4 h to obtain the precursor.

[0103] 0.14 g of potassium carbonate was dissolved in 20 mL of aqueous solution to obtain a potassium carbonate solution. The previously obtained precursor was impregnated with this solution. After impregnation, the sample was first dried by rotary evaporation at 120 °C and a vacuum of 0.1 MPa for 4 h. The resulting sample was then dried at 120 °C for 2 h and then calcined at 500 °C for 2 h to obtain catalyst D-1. BET specific surface area and pore volume were measured, and the results are shown in Table 1.

[0104] Comparative Example 2

[0105] (1) Mix 20g of ferric nitrate nonhydrate and 1.86g of aluminum nitrate nonhydrate in a mortar and grind them into powder in a ball mill for 10 minutes.

[0106] (2) Add 15g KOH and 15g K2CO3 to the powder obtained in step (1) and continue grinding for 15min.

[0107] (3) Dissolve 0.60g of copper nitrate trihydrate in 5g of deionized water, and add it to the powder obtained in step (2). Continue grinding for 15 minutes.

[0108] (4) Transfer the mixture obtained in step (3) to a hydrothermal reactor, place it in a microwave synthesizer, heat it to 180°C at a frequency of 2.45 GHz, hold it at that temperature for 8 hours, then stop microwave heating, allow it to cool naturally for 2 hours, wash it three times with deionized water, and dry it at 120°C for 4 hours to obtain the precursor.

[0109] (5) The precursor powder was calcined at 500℃ for 2h to obtain catalyst D-2. BET specific surface area and pore volume were tested, and the results are shown in Table 1.

[0110] Examples 8-14, Comparative Examples 3-4

[0111] The following examples and comparative examples illustrate the application of the catalysts obtained in Examples 1-7 and Comparative Examples 1-2.

[0112] The catalyst prepared above was compressed into tablets at 15 MPa, crushed, and screened to a mesh size of 40-60. 0.5 g of the screened catalyst was then loaded into a reaction tube with an inner diameter of 8 mm to carry out a water-gas shift reaction.

[0113] Reduction preprocessing:

[0114] All catalysts underwent reduction pretreatment: the pretreatment atmosphere was CO / CO2 / H2 / N2 (volume fraction) = 24.7% / 8.3% / 49.5% / 17.5%, where N2 was an internal standard and did not participate in the reaction; the pretreatment temperature was 400℃, the pretreatment time was 2 h, the pressure was atmospheric pressure, and the pretreatment dry gas hourly space velocity was 16000 h⁻¹. -1 H2O / CO (molar ratio) = 1.6.

[0115] In the formal water-gas shift reaction, the feed gas consists of dry gas and water. The dry gas has the following composition by volume fraction: CO / CO2 / H2 / N2 = 24.7% / 8.3% / 49.5% / 17.5%, where N2 is an internal standard gas and does not participate in the reaction; the molar ratio of H2O / CO in the feed gas is 2.4.

[0116] The reaction conditions used were: 0.5 MPa and dry gas hourly space velocity (HHSV) of 16000 h⁻¹. -1 The reaction is carried out at 400℃.

[0117] After the formal reaction is completed, a heat resistance activity test is conducted. The conditions for the heat resistance activity test are as follows: the reaction pressure, feed gas, and space velocity are the same as those for the formal reaction. The reaction temperature is raised to 530℃ and held for 2 hours, then lowered to 400℃ and equilibrated for 1 hour. Samples are taken, and the carbon monoxide conversion rate is calculated after analysis as the heat resistance activity data.

[0118] The liquid products were collected in an ice-water bath, and the product composition was analyzed by gas chromatography. The specific evaluation results are shown in Table 2.

[0119] Table 1

[0120]

[0121] Table 2

[0122]

[0123] 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. A method for preparing an iron-based catalyst, comprising the following steps: (1) Mix and grind Fe salt and auxiliary agent A salt to obtain mixture I; Additive A is selected from one or more of Mn, Mo, Co, Al, Ce, La, V, Ni, Mg, and Ca, and the molar ratio of Fe to additive A is 2:1-30:

1. The mixture is ground using a ball mill for 2-60 minutes to allow additive A to form a solid solution with the Fe-based catalyst. (2) After mixing the precipitant with the mixture I obtained in step (1), continue grinding for a certain time to obtain mixture II, wherein a ball mill is used for grinding, and the grinding time is 2 min to 60 min; (3) Provide a solution containing auxiliary agent B salt and add it to the mixture II obtained in step (2), continue grinding and mixing for a certain time to obtain mixture III, wherein a ball mill is used for grinding, and the grinding time is 2 min-60 min; Additive B is selected from one or more of Cu, Ni, Pt, and Pd, and the elemental molar ratio of Fe to additive B is 10:1-200:1; (4) The mixture III obtained in step (3) is sent to a hydrothermal reactor for hydrothermal treatment, and then washed and dried to obtain the precursor; (5) The promoter C is loaded onto the above precursor, dried and calcined to obtain an iron-based catalyst. The promoter C is selected from at least one of the alkali metals Na, K and Cs. The resulting iron-based catalyst was applied in the water-gas shift reaction.

2. The preparation method according to claim 1, characterized in that, Additive A is selected from one or more of Mn, Al, Ni, and Ce; The Fe salt and the auxiliary agent A salt are each independently selected from at least one of the following: nitrate, sulfate, formate, acetate, and halide of Fe and auxiliary agent A.

3. The preparation method according to claim 1, characterized in that, In step (2), the precipitant is one or more selected from ammonium carbonate, urea, sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, and ammonium hydroxide; The molar amount of precipitant is 1-5 times the theoretical stoichiometric ratio of the total number of metal atoms of Fe, additive A, and additive B.

4. The preparation method according to claim 1, characterized in that, In step (3), the auxiliary agent B salt is dissolved in deionized water to obtain a solution containing the auxiliary agent B salt, wherein the auxiliary agent B salt is selected from at least one of the following: nitrate, sulfate, formate, acetate, and halide of the auxiliary agent B; In solutions containing salt of auxiliary agent B, the concentration of auxiliary agent B is 10-100 mol / L; The molar ratio of Fe to auxiliary agent B is 10:1 to 100:1, based on elemental composition. Additive B is selected from at least one of Cu and Ni.

5. The preparation method according to claim 4, characterized in that, In step (3), the concentration of auxiliary agent B in the solution containing auxiliary agent B salt is 20-50 mol / L.

6. The preparation method according to claim 1, characterized in that, In step (4), the hydrothermal treatment reaction temperature is 80-250℃ and the reaction time is 1-72h.

7. The preparation method according to claim 1, characterized in that, In step (4), the hydrothermal treatment is microwave-assisted hydrothermal treatment. The conditions for microwave-assisted hydrothermal treatment are: reaction temperature 100-250℃, microwave output power 500-1500W, and reaction time 1-8h.

8. The preparation method according to claim 1, characterized in that, In step (4), the drying temperature is 60-150℃ and the drying time is 0.5-8h.

9. The preparation method according to claim 1, characterized in that, In step (4), the drying temperature is 80-120℃ and the drying time is 1-4h.

10. The preparation method according to claim 1, characterized in that, In step (5), the amount of additive C added is 0.1-10% by mass fraction of the iron-based catalyst, calculated as oxide. The method of loading additive C onto the precursor is as follows: mechanically mixing at least one of the oxide, inorganic salt, and organometallic compound of additive C with the precursor; or impregnating the precursor with a solution containing at least one of the inorganic salt and organometallic compound of additive C.

11. The preparation method according to claim 1, characterized in that, In step (5), the drying temperature is 60-150℃, the drying time is 0.5h-8h, the calcination temperature is 200-600℃, and the calcination time is 1-10h.

12. The preparation method according to claim 1, characterized in that, In step (5), the drying temperature is 80-120℃, and the drying time is 1-4 hours. The roasting temperature is 300-550℃, and the roasting time is 1-8h.

13. The preparation method according to claim 11 or 12, characterized in that, When the precursor is impregnated with a solution containing at least one inorganic salt or organometallic compound of auxiliary agent C, rotary evaporation drying is performed before drying. The rotary evaporation drying temperature is 30-80℃, the vacuum degree is 0.1MPa, and the rotary evaporation drying time is 0.2-2h.

14. The iron-based catalyst obtained by any one of the preparation methods according to claims 1-13, characterized in that, Based on the overall iron-based catalyst, and calculated as oxides, the Fe content is 70-95%, the content of promoter A is 1-20%, the content of promoter B is 0.1-10%, and the content of promoter C is 0.1-10%. Additive A is selected from one or more of Mn, Mo, Co, Al, Ce, La, V, Ni, Mg, and Ca; Additive B is selected from one or more of Cu, Ni, Pt, and Pd; and Additive C is selected from at least one of the alkali metals Na, K, and Cs.

15. A method for applying the iron-based catalyst obtained by any of the preparation methods according to claims 1-13, characterized in that, The iron-based catalyst was packed in a fixed-bed reactor for a water-gas shift reaction, under the following conditions: pressure 0.1-5 MPa, temperature 300-500℃, and volumetric hourly space velocity 2000-100000 h⁻¹. -1 The ratio of nH2O to nCO in the raw material gas is 2.4-4.

16. The application method according to claim 15, characterized in that, The temperature is 350-400℃.

17. The application method according to claim 15, characterized in that, The iron-based catalyst is subjected to reduction pretreatment before use. The pretreatment atmosphere is H2 / CO / H2O or H2 / CO / H2O / CO2, the pretreatment temperature is 200-600℃, the pretreatment time is 1-12h, the pretreatment pressure is 0.1-1MPa, and the pretreatment volume hourly space velocity is 500-20000h⁻¹. -1 .

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