Iron-ruthenium synergistic catalyst as well as preparation method and application thereof

Abstract

The invention discloses an iron-ruthenium synergistic catalyst and a preparation method and application thereof.The method comprises the steps that 1, an iron salt solution, an auxiliary salt solution and a precipitant solution serve as reaction raw materials to be subjected to a co-precipitation reaction, and precipitation slurry is prepared; 2) carrying out solid-liquid separation on the precipitation slurry to obtain a filter cake, and washing, drying, roasting and crushing the filter cake to obtain a dry-based iron precursor; (3) mixing the dry-basis iron precursor with an adhesive, adding the adhesive, and molding to form a carrier; 4) drying and roasting the carrier to obtain a roasted product; and 5) dipping the roasted product in a ruthenium salt solution and a potassium salt solution, taking out the roasted product after dipping, and drying and roasting the roasted product to prepare the iron-ruthenium synergistic catalyst. The shape and the strength of the obtained catalyst are controllable, and the activity, the toxicity resistance and the mechanical strength of the catalyst can be improved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic ammonia catalysts, and particularly relates to an iron-ruthenium synergistic catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The raw material gas used in traditional synthetic ammonia is hydrogen and nitrogen. The main catalyst used is a fused iron catalyst, and the promoters used are alumina, calcium oxide, etc.; alternatively, a ruthenium-based catalyst with noble metal ruthenium as the active component, activated carbon as the carrier, and metal salts such as barium and silver as the promoters can be used.

[0003] CN104289217A discloses a ruthenium-based ammonia synthesis catalyst supported on a biomorphic composite oxide and a preparation method thereof. The ammonia synthesis catalyst uses a biomorphic composite oxide as the carrier and metal Ru as the active component. The loading amount of the active component in terms of Ru is 0.5 wt% - 12 wt% of the biomorphic composite oxide; the biomorphic composite oxide is a biomorphic composite oxide of magnesium and one or more of the following other metals prepared through a biological template: ① alkaline earth metals other than magnesium, ② alkali metals, ③ rare earth metals. The molar ratio of magnesium to the other metal is 50 - 500:1, and the biological template is Chinese fir, filter paper, absorbent cotton, amino acid, or protein; however, this supported ruthenium-based catalyst is easily affected by the carrier, and the stability of the obtained catalyst is poor.

[0004] CN106799232A discloses a nano-iron modified iron-based ammonia synthesis catalyst prepared by a room-temperature solid-phase reaction, a preparation method thereof, and an application thereof. The iron-based ammonia synthesis catalyst, an iron precursor, and a solid reagent are uniformly mixed, ground, ball-milled, or stirred, so that the iron precursor reacts with the solid reagent on the carrier of the iron-based ammonia synthesis catalyst. After the reaction, the product is filtered, washed, dried, and heat-treated under air, nitrogen, argon, or vacuum conditions to obtain the final nano-iron modified iron-based ammonia synthesis catalyst.

[0005] CN113976134A discloses a low-temperature, low-pressure, and highly active ammonia synthesis catalyst, developing more catalyst types. The ferrous oxide-based catalyst is composed of ferrous oxide and a promoter. The promoter includes alumina, potassium oxide, alkaline earth metal oxides, rare earth metal oxides, and transition metal oxides; the raw materials required for each component in the formulated amount are mixed evenly, melted into a liquid state under an atmospheric environment, and the obtained liquid slurry is quickly discharged into a cooling tank with a water jacket and cooled to below 100°C. The obtained melt block is post-treated to obtain the ferrous oxide-based catalyst.

[0006] However, the above two prior arts both belong to iron-based catalysts, and the specific surface area of existing iron-based catalysts is relatively small. During use, the active components of the catalyst will inevitably aggregate, thereby reducing the activity. In addition, during long-term use, there will also be a problem that the catalyst breaks into particles and cannot be controlled, which will also affect the catalytic activity and result in low catalyst activity. Summary of the Invention

[0007] In view of this, the main object of the present invention is to provide an iron-ruthenium synergistic catalyst, a preparation method and an application thereof. The catalyst has high activity, and its shape and strength are controllable.

[0008] To achieve the above invention object, the first aspect of the present invention provides a preparation method of an iron-ruthenium synergistic catalyst, comprising the following steps:

[0009] 1) Using an iron salt solution, an auxiliary salt solution, and a precipitant solution as reaction raw materials, performing a coprecipitation reaction to obtain a precipitate slurry;

[0010] 2) Separating the solid and liquid of the precipitate slurry obtained in step 1) to obtain a filter cake, washing, drying, roasting, and crushing the filter cake to obtain a dry-based iron precursor;

[0011] 3) Mixing the dry-based iron precursor with a binder, adding an adhesive, and forming it into a carrier;

[0012] 4) Subjecting the carrier to drying and roasting treatments to obtain a roasted product;

[0013] 5) Immersing the roasted product in a ruthenium salt solution and a potassium salt solution, taking out the product after immersion, and performing drying and roasting to obtain an iron-based catalyst;

[0014] Wherein, the auxiliary salt includes one or more of an electronic auxiliary salt and a barrier auxiliary salt.

[0015] Further, the iron salt is selected from one or more of iron nitrate, iron sulfate, and iron chloride.

[0016] Further, the electronic auxiliary salt is selected from one or more of soluble potassium salts, soluble barium salts, and soluble calcium salts, preferably one or more of soluble barium salts and soluble calcium salts.

[0017] Further, the barrier auxiliary salt is selected from one or more of soluble titanium salts, soluble zirconium salts, soluble vanadium salts, soluble chromium salts, soluble nickel salts, soluble copper salts, soluble zinc salts, and soluble cerium salts, preferably one or more of soluble copper salts and soluble zinc salts.

[0018] Further, the auxiliary salt can be a mixture of an electronic auxiliary salt and a barrier auxiliary salt.

[0019] Furthermore, the promoter salt is a mixture of a soluble copper salt and a soluble barium salt.

[0020] Furthermore, the precipitant is selected from ammonia water and / or ammonium bicarbonate.

[0021] Furthermore, the concentration of the iron salt solution is 1-50%; the concentration of the promoter salt solution is 1-50%; the concentration of the precipitant solution is 1-30%.

[0022] Furthermore, the mass ratio range of the iron salt to the electronic promoter salt is 100:(0.2-20), such as 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:2, 100:4, 100:6, 100:8, 100:10, 100:12, 100:15, 100:18 or 100:20, etc. This range is beneficial for the electronic promoter to provide electrons to the active component, and preferably 100:(0.5-10).

[0023] The mass ratio range of the iron salt to the barrier promoter salt is 100:(0.2-10), such as 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.8, 100:1, 100:2, 100:4, 100:6, 100:8 or 100:10, etc. This range is beneficial for the dispersion of the active component and reduces aggregation during long-term operation, and preferably 100:(0.5-10).

[0024] The mass ratio range of the iron salt to the binder is 100:(20-80), such as 100:20, 100:30, 100:40, 100:50, 100:60, 100:70 or 100:80, etc. This range is beneficial for improving the mechanical strength of the formed catalyst.

[0025] For the synthetic ammonia catalyst to have high activity, selectivity and long-term stability, the present invention is prepared by a co-precipitation process and a complex of multiple promoter component salts is added in the co-precipitation process. That is, in the obtained catalyst, by introducing a barrier promoter component (such as oxides of copper, titanium, zirconium, vanadium, chromium, nickel, etc.), the aggregation of the active component of the catalyst can be prevented; in order to prevent the decrease in activity caused by the aggregation of the active component, by introducing an electronic promoter component (such as oxides of potassium, sodium, calcium, magnesium, barium), the dissociation of nitrogen can be promoted and the reaction activity of ammonia synthesis can be improved; furthermore, by introducing a binder, the mechanical strength and stability of the catalyst can be improved.

[0026] Further, in step 1), the ferric salt solution, the promoter salt solution, and the precipitant solution enter the reactor in a co-current feeding manner. The advantage of this feeding method is that it can well disperse and homogenize the active components and the promoter salts.

[0027] Further, in step 1), the conditions for the coprecipitation reaction include: the pH value of the system is 3 - 10, preferably 5 - 10, and the reaction temperature is 10 - 100 °C, preferably 60 - 90 °C. For example, the pH value of the system can be adjusted by the addition amount of the precipitant or the precipitant solution.

[0028] Further, in step 1), it also includes subjecting the precipitation slurry to an aging treatment. The conditions for the aging treatment include: the aging temperature is 30 - 90 °C, and the aging time is 0 - 2 h.

[0029] Further, in step 2), the conditions for drying include: the drying temperature is 80 - 200 °C, and the drying time is 8 - 24 h; the conditions for calcination include: the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 12 h.

[0030] Further, in step 3), the binder is a silicon-containing compound and / or an aluminum-containing compound, preferably alumina or silica; further preferably, based on the amount of Fe2O3 in the dry-based iron precursor, the mass ratio of Fe2O3 to Al2O3 = 100∶20 - 90, and / or the mass ratio of Fe2O3 to SiO2 is 100:(0 - 80).

[0031] Further, in step 3), the adhesive is nitric acid; preferably, the adhesive accounts for 0.5 - 5.0 wt% of the mass of the dry-based iron precursor, such as 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%, preferably 1 - 3 wt%.

[0032] Further, in step 3), it also includes subjecting the carrier to an aging treatment. The conditions for the aging treatment include: the aging temperature is 30 - 90 °C, and the aging time is 0 - 2 h.

[0033] Further, in step 4), the conditions for drying include: the drying temperature is 80 - 200 °C, and the drying time is 8 - 24 h; the conditions for calcination include: the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 12 h.

[0034] Further, in step 5), the concentration of the ruthenium salt solution is 1-30%, such as 1%, 2%, 4%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%, etc.; the concentration of the potassium salt solution is 1-30%, such as 1%, 2%, 4%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%.

[0035] Further, the ruthenium salt is selected from one or more of ruthenium chloride and ruthenium carbonyl, and the potassium salt is selected from one or more of potassium nitrate and potassium carbonate.

[0036] Further, in step 5), the drying conditions include: the drying temperature is 80-200 °C, and the drying time is 8-24 h; the calcination conditions include: the calcination temperature is 400-600 °C, and the calcination time is 2-12 h.

[0037] In the second aspect of the present invention, there is provided an iron-ruthenium synergistic catalyst prepared by the preparation method as described above. Based on the total weight of the catalyst being 100 wt%, the components and their content ranges in the catalyst are as follows:

[0038] The content of iron oxide is 30-75%, preferably 30-60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%;

[0039] The content of ruthenium is 0.5-10%, preferably 2-5%, such as 0.5%, 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9% or 10%;

[0040] The content of potassium oxide is 0.5-20%; preferably 5-15%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 8%, 10%, 12%, 15%, 18% or 20%;

[0041] The content of alumina or silica is 20-50%, preferably 20-40%, such as 20%, 25%, 30%, 35%, 40%, 45% or 50%;

[0042] The balance is the total content of the promoter components.

[0043] In the third aspect of the present invention, there is provided an application of the iron-ruthenium synergistic catalyst prepared by the preparation method as described above or the iron-ruthenium synergistic catalyst as described above in the synthesis of ammonia reaction.

[0044] Further, the reaction conditions for the synthesis of ammonia reaction include:

[0045] The temperature is 200°C - 500°C, the pressure is 5 MPa - 15 MPa, and the space velocity is 1000 h -1 -30000 h -1 .

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] (1) In the present invention, an iron salt solution, an auxiliary salt solution, and a precipitant solution are used as raw materials for coprecipitation reaction. The auxiliary salt is introduced through coprecipitation, and the auxiliary components are more uniformly dispersed; the obtained catalyst is easier to reduce, has more active sites, and higher activity;

[0048] (2) In the preparation method of the present invention, an iron precursor is obtained through coprecipitation, which can increase the specific surface area of the obtained iron-based catalyst (for example, it can be controlled within 50 - 500 m 2 / g), the pore volume and pore diameter are controllable, and the pore volume > 0.1 cm 3 / g (for example, it is 0.1 - 0.5 cm 3 / g);

[0049] (3) In the present invention, ruthenium and potassium are impregnated by the impregnation method to obtain a catalyst with the synergy of iron and ruthenium, and the high catalytic activity of single-atom ruthenium is utilized at the same time.

[0050] In summary, when the iron-ruthenium synergy catalyst prepared by the present invention is applied to the ammonia synthesis reaction, the reaction temperature and pressure can be reduced, and the activity of the catalyst can be increased.

[0051] (4) In addition, in the present invention, the dry-based iron precursor is mixed with a binder, an adhesive is added and formed into a carrier, so that the shape, size, and strength of the catalyst are controllable and can be controlled to the required shape; and the strength of the catalyst is increased by adjusting the binder, which is more conducive to improving the anti-toxicity and mechanical strength of the catalyst.

[0052] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Specific Embodiments

[0053] The following will describe the specific embodiments of the present invention in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0054] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values and individual point values of each range, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0055] In the embodiments of the present invention, raw materials and reagents can be obtained through commercial channels without special instructions.

[0056] The analytical and testing methods adopted in the embodiments of the present invention are as follows:

[0057] (1) Test process for specific surface area, pore volume and pore diameter: It is measured by a physical adsorption method BET tester (the instrument is purchased from Micromeritics Company, USA, model ASAP).

[0058] (2) Test process for attrition rate: Under the action of the injection of high-speed air flow, the catalyst is in a fluidized state, and fine powder is generated due to friction between catalyst particles. Through screening and weighing, the attrition rate of the catalyst is calculated.

[0059] The iron-ruthenium co-catalyst of the present invention, its preparation method and application are elaborated in detail below through examples.

[0060] Example 1

[0061] Dissolve 25 kg of ferric nitrate nonahydrate, 0.4 kg of barium nitrate, and 0.3 kg of copper nitrate in deionized water to prepare a 160-liter solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80-liter solution. Pump the ferric nitrate, barium nitrate, copper nitrate solution and ammonia water solution into the reaction kettle in parallel, control the temperature in the reaction kettle at 60 °C, and control the pH value at 6. After precipitation, age at 60 °C for 30 minutes. After the filter cake is filtered, dry it at 120 °C for 12 h and calcine it at 500 °C for 5 h. Then ball-mill and crush it into powder. Mix the powder with alumina according to the dry basis m(Fe2O3)∶m(Al2O3) = 65∶35, add nitric acid as an adhesive, and the addition amount of nitric acid during extrusion accounts for 3% of the mass of the powder (dry basis), and water accounts for 70% of the mass of the powder (dry basis) to form a carrier. The carrier is aged at room temperature for 4 h, dried at 80 °C for 5 h, and calcined at 500 °C for 5 h. Use ruthenium chloride solution as the ruthenium source and potassium nitrate solution as the potassium source. Dissolve 1.45 kg of potassium nitrate and 0.6 kg of ruthenium chloride in deionized water to prepare a 17-liter solution as the impregnation solution. Impregnate the calcined product by the pore saturation impregnation method with equal volume. After impregnation, take out the product and dry it at 8 °C for 4 h and calcine it at 500 °C for 5 h to obtain the catalyst. The mass fraction of ruthenium loading in this catalyst is 4%, and the mass fraction of potassium oxide loading is 10%.

[0062] Example 2

[0063] Dissolve 25 kg of ferric nitrate nonahydrate, 0.04 kg of barium nitrate, and 0.8 kg of copper nitrate in deionized water to prepare a 160-liter solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80-liter solution. Pump the ferric nitrate, barium nitrate, copper nitrate solutions and the ammonia water solution into the reaction kettle in parallel flow, control the temperature in the reaction kettle at 90 °C, and control the pH value at 8. After precipitation, age at 90 °C for 30 minutes. After the filter cake is filtered, dry it at 120 °C for 12 h, calcine it at 500 °C for 5 h, then ball-mill and crush it into powder. Mix the powder with alumina according to the dry basis m(Fe2O3)∶m(Al2O3) = 65∶35, add nitric acid as an adhesive. When extruding, the addition amount of nitric acid accounts for 3% of the mass of the powder (dry basis), and water accounts for 70% of the mass of the powder (dry basis). The carrier is aged at room temperature for 4 h, dried at 80 °C for 5 h, and calcined at 500 °C for 5 h. Use ruthenium chloride solution as the ruthenium source and potassium nitrate solution as the potassium source. Dissolve 1.45 kg of potassium nitrate and 0.6 kg of ruthenium chloride in deionized water to prepare a 17-liter solution as the impregnation solution. Impregnate the calcined product by equal-volume impregnation using the pore saturation impregnation method. After impregnation, take out the product and dry it at 80 °C for 4 h, and calcine it at 500 °C for 5 h to obtain the catalyst. The ruthenium loading mass fraction in this catalyst is 4%, and the potassium oxide loading mass fraction is 10%.

[0064] Example 3

[0065] Dissolve 25 kg of ferric nitrate nonahydrate, 0.8 kg of barium nitrate, and 0.04 kg of copper nitrate in deionized water to prepare a 160-liter solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80-liter solution. Pump the ferric nitrate, barium nitrate, copper nitrate solutions and the ammonia water solution into the reaction kettle in parallel flow, control the temperature in the reaction kettle at 30 °C, and control the pH value at 11. After precipitation, age at 30 °C for 30 minutes. After the filter cake is filtered, dry it at 120 °C for 12 h, calcine it at 500 °C for 5 h, then ball-mill and crush it into powder. Mix the molecular sieve with alumina according to the dry basis m(Fe2O3)∶m(Al2O3) = 65∶35, add nitric acid as an adhesive. When extruding, the addition amount of acid accounts for 3% of the mass of the powder (dry basis), and water accounts for 70% of the mass of the powder (dry basis). The carrier is aged at room temperature for 4 h, dried at 80 °C for 5 h, and calcined at 500 °C for 5 h. Use ruthenium chloride solution as the ruthenium source and potassium nitrate solution as the potassium source. Dissolve 1.45 kg of potassium nitrate and 0.6 kg of ruthenium chloride in deionized water to prepare a 17-liter solution as the impregnation solution. Impregnate the calcined product by equal-volume impregnation. After impregnation, take out the product and dry it at 80 °C for 4 h, and calcine it at 500 °C for 5 h to obtain the catalyst. The ruthenium loading mass fraction in this catalyst is 4%, and the potassium oxide loading mass fraction is 10%.

[0066] Example 4

[0067] Dissolve 25 kg of ferric nitrate nonahydrate, 0.6 kg of calcium nitrate, and 0.6 kg of zinc nitrate hexahydrate in deionized water to prepare a 160 - liter solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80 - liter solution. Pump the ferric nitrate, calcium nitrate, zinc nitrate solutions and the ammonia water solution into the reactor in parallel. Control the temperature in the reactor at 60 °C and the pH value at 6. After precipitation, age the product at 60 °C for 30 minutes. After filtration of the filter cake, dry it at 120 °C for 12 h, calcine it at 500 °C for 5 h, and then ball - mill and crush it into powder. Mix the molecular sieve and silica according to the dry - basis mass ratio of m(Fe2O3)∶m(SiO2) = 65∶35, add nitric acid as an adhesive. When extruding, the addition amount of nitric acid accounts for 1% of the mass of the powder (dry - basis), and water accounts for 70% of the mass of the powder (dry - basis). The carrier is aged at room temperature for 4 h, dried at 80 °C for 5 h, and calcined at 500 °C for 5 h. Use ruthenium chloride solution as the ruthenium source and potassium nitrate solution as the potassium source. Dissolve 0.73 kg of potassium nitrate and 0.6 kg of ruthenium chloride in deionized water to prepare a 17 - liter solution as the impregnation solution. Impregnate the calcined product by the pore - saturation impregnation method with equal volume. After impregnation, take out the product and dry it at 80 °C for 4 h, and then calcine it at 500 °C for 5 h to obtain the catalyst. The mass fraction of ruthenium loading in this catalyst is 4%, and the mass fraction of potassium oxide loading is 5%.

[0068] Comparative Example 1 (without ruthenium impregnation)

[0069] The preparation method of the iron - based ammonia synthesis catalyst includes the following steps:

[0070] (1) Dissolve 25 kg of ferric nitrate nonahydrate, 0.2 kg of copper nitrate, and 0.3 kg of barium nitrate in deionized water to prepare a 160 - liter mixed - salt solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80 - liter precipitant solution;

[0071] Pump the prepared mixed - salt solution containing ferric nitrate, copper nitrate, and calcium nitrate and the precipitant solution into the reactor in parallel by a pump. Control the temperature in the reactor at 30 °C, and control the pH value of the system at 6 by the addition amount of the precipitant solution to carry out a coprecipitation reaction to obtain a precipitate slurry;

[0072] After precipitation, age the obtained product at 30 °C for 30 minutes at this temperature;

[0073] (2) Filter the obtained aged product. After washing the filter cake, dry it at 120 °C for 12 h, then calcine it at 500 °C for 5 h, and then ball - mill and crush it into powder to obtain a dry - basis iron precursor;

[0074] (3) Mix the dry-based iron precursor obtained in step (2) with alumina according to m(dry-based Fe₂O₃)∶m(Al₂O₃) = 65∶35, and add nitric acid as an adhesive thereto. After mixing, perform extrusion molding to form a carrier; wherein the addition amount of nitric acid during extrusion accounts for 3 wt% of the mass of the dry-based iron precursor powder, and water accounts for 70 wt% of the mass of the dry-based iron precursor powder;

[0075] The obtained carrier is aged at room temperature for 4 h, then dried at 80 °C for 5 h, and then calcined at 500 °C for 5 h;

[0076] (4) Dissolve 0.2 kg of potassium nitrate in deionized water to prepare a 17-liter solution; the calcined product is impregnated with the potassium salt by the pore saturation impregnation method in an equal volume, and then taken out from the impregnation solution and dried at 80 °C for 4 h, and then calcined at 500 °C for 5 h to obtain a catalyst, and the loaded mass fraction of potassium oxide in this catalyst is 2 wt%.

[0077] Comparative Example 2

[0078] Dissolve 25 kg of ferric nitrate nonahydrate, 0.04 kg of barium nitrate, and 0.8 kg of copper nitrate in deionized water to prepare a 160-liter solution. Dissolve 12.5 kg of ammonia water in deionized water to prepare an 80-liter solution. Pump the ferric nitrate, barium nitrate, copper nitrate solutions and the ammonia water solution into the reaction kettle in parallel, control the temperature in the reaction kettle at 90 °C, and control the pH value at 8. After precipitation, let it stand and age for 30 minutes. After the filter cake is filtered, it is dried at 120 °C for 12 h, calcined at 500 °C for 5 h, and then ball-milled and crushed into powder. Mix the molecular sieve with alumina according to the dry-based m(Fe₂O₃)∶m(Al₂O₃) = 65∶35, add nitric acid as an adhesive, and the addition amount of nitric acid during extrusion accounts for 3% of the mass of the powder (dry-based), and water accounts for 70% of the mass of the powder (dry-based). The carrier is aged at room temperature for 4 h, dried at 80 °C for 5 h, and calcined at 500 °C for 5 h. Use ruthenium chloride solution as the ruthenium source and potassium nitrate solution as the potassium source. Dissolve 3.63 kg of potassium nitrate and 0.1 kg of ruthenium chloride in deionized water to prepare a 17-liter solution as the impregnation solution. Impregnate the calcined product by the pore saturation impregnation method, dry at 80 °C for 4 h, and calcine at 500 °C for 5 h to obtain a catalyst, and the loaded mass fraction of ruthenium in this catalyst is 0.5%, and the loaded mass fraction of potassium oxide is 25%.

[0079] Comparative Example 3

[0080] Mix alumina, potassium oxide, calcium oxide and iron tetroxide evenly to obtain a mixture. Among them, based on the total weight of the mixture being 100 wt%, the proportion of alumina is 5 wt%, the proportion of potassium oxide is 3 wt%, the proportion of calcium oxide is 1.5 wt%, and the balance is iron tetroxide; then load the mixture into a steel furnace with a water jacket, connect two electrodes with leads to make it energized, and rely on the conductivity of the substance and its own resistance to make the mixture conduct electricity and generate heat for melting; after melting for 20 minutes, quickly pour the high-temperature molten material into a cooling tank with a water jacket to cool it to room temperature, and the obtained product is crushed and screened to the required particle size to prepare the catalyst.

[0081] Table 1 Composition of the catalysts prepared in each example and comparative example

[0082]

[0083] Table 2 Physical property parameters of the catalysts prepared in each example and comparative example

[0084] Number <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Aperture Wear rate (%) Example 1 243 0.45 9.12 5 Example 2 189 0.43 9.15 5 Example 3 219 0.42 10.05 5 Example 4 231 0.43 10.14 5 Comparative Example 1 254 0.45 9.07 5 Comparative Example 2 195 0.43 9.17 5 Comparative Example 3 10 0.02 1.02 6

[0085] Catalyst performance evaluation

[0086] Apply the catalyst prepared as above to the reaction process of ammonia synthesis and conduct performance testing on it. In the synthesis reactor, react hydrogen and nitrogen in the presence of the catalyst prepared as above. The reaction process of ammonia synthesis is: 3H2 + 2N2 = 2NH3;

[0087] Among them, the process conditions include: the temperature is 400 - 450 °C, the pressure is 5 MPa, the space velocity is 30000 h -1 , the raw material gas composition is H2 / N2 = 3:1, and measure the ammonia concentration at the outlet of the reactor where the catalysts obtained from each example and comparative example are applied for reaction respectively.

[0088] Table 3 Performance evaluation results of the catalysts prepared in each example and comparative example

[0089]

[0090] It can be seen from the data in Table 1 - Table 3 above that for the iron-ruthenium co-catalyst prepared in Examples 1 - 4 of the present invention, the process conditions for ammonia synthesis can be milder and the activity is higher. In Comparative Example 1, the catalyst is not loaded with ruthenium components. In Comparative Example 2, the ratio of each active component (iron, potassium, ruthenium, etc.) is not set within the preferred content range of the present invention. In Comparative Example 3, when using a conventional fused iron catalyst activator, the catalytic effect is worse than that of the examples of the present invention.

[0091] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation manners here. All obvious changes or modifications derived from the technical solutions of the present invention are within the spirit scope covered by the present invention.

Claims

1. A preparation method of an iron-ruthenium synergistic catalyst, characterized in that, It includes the following steps: 1) Using an iron salt solution, an auxiliary salt solution, and a precipitant solution as reaction raw materials, performing a coprecipitation reaction to obtain a precipitate slurry; the auxiliary salt includes one or more of an electronic auxiliary salt and a barrier auxiliary salt; 2) Separating the solid and liquid of the precipitate slurry obtained in step 1) to obtain a filter cake, washing, drying, roasting, and crushing the filter cake to obtain a dry-based iron precursor; 3) Mixing the dry-based iron precursor with a binder, adding an adhesive, and forming it into a carrier; 4) Subjecting the carrier obtained in step 3) to drying and roasting treatments to obtain a roasted product; 5) Immersing the roasted product in a ruthenium salt solution and a potassium salt solution, taking out the product after immersion, and performing drying and roasting to prepare an iron-ruthenium synergistic catalyst.

2. The method for preparing the catalyst according to claim 1, wherein the iron salt is selected from one or more of iron nitrate, iron sulfate, and iron chloride; the precipitant is selected from ammonia water and / or ammonium bicarbonate.

3. The method for preparing the catalyst according to claim 1 or 2, wherein the electronic auxiliary salt is selected from one or more of soluble potassium salts, soluble barium salts, and soluble calcium salts, preferably one or more of soluble barium salts and soluble calcium salts; the barrier auxiliary salt is selected from one or more of soluble titanium salts, soluble zirconium salts, soluble vanadium salts, soluble chromium salts, soluble nickel salts, soluble copper salts, soluble zinc salts, and soluble cerium salts, preferably one or more of soluble copper salts and soluble zinc salts; Preferably, the auxiliary salt is a mixture of an electronic auxiliary salt and a barrier auxiliary salt; More preferably, the auxiliary salt is a mixture of a soluble barium salt and a soluble copper salt.

4. The preparation method of the catalyst according to any one of claims 1-3, characterized in that, The concentration of the iron salt solution is 1-50%; the concentration of the auxiliary salt solution is 1-50%; the concentration of the precipitant solution is 1-30%; and / or, the mass ratio range of the iron salt to the electronic auxiliary salt is 100:(0.2-20); the mass ratio range of the iron salt to the barrier auxiliary salt is 100:(0.2-10); the mass ratio range of the iron salt to the binder is 100:(20-80).

5. The method for preparing the catalyst according to claim 1, wherein in step 1), the conditions of the coprecipitation reaction include: the pH value of the system is 3-10, preferably 5-10, the reaction temperature is 10-100°C, preferably 60-90°C. In step 1), it further includes subjecting the precipitate slurry to an aging treatment, and the conditions of the aging treatment include: the aging temperature is 30-90°C, and the aging time is 0-2h; In step 2), the conditions of the drying include: the drying temperature is 80-200°C, and the drying time is 8-24h; the conditions of the roasting include: the roasting temperature is 400-600°C, and the roasting time is 2-12h.

6. The method for preparing the catalyst according to claim 1 or 5, wherein In step 3), the binder is a silicon-containing compound and / or an aluminum-containing compound, preferably alumina or silica; further preferably, based on the amount of Fe2O3 in the dry-based iron precursor, the mass ratio of Fe2O3 to Al2O3 = 100∶20 - 90; the mass ratio of Fe2O3 to SiO2 is 100:(0 - 80). In step 3), the adhesive is nitric acid; preferably, the adhesive accounts for 0.5 - 5.0 wt% of the mass of the dry-based iron precursor; In step 3), it further includes subjecting the carrier to an aging treatment, and the conditions of the aging treatment include: the aging temperature is 30 - 90 °C, and the aging time is 0 - 2 h.

7. The method for preparing a catalyst according to any one of claims 1 - 6, wherein In step 4), the conditions for drying include: the drying temperature is 80 - 200 °C, and the drying time is 8 - 24 h; the conditions for calcination include: the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 12 h.

8. The method for preparing a catalyst according to any one of claims 1 - 7, wherein In step 5), the concentration of the ruthenium salt solution is 1 - 30%, and the concentration of the potassium salt solution is 1 - 30%. The ruthenium salt is selected from one or more of ruthenium chloride and ruthenium carbonyl, and the potassium salt is selected from one or more of potassium nitrate or potassium carbonate; In step 5), the conditions for drying include: the drying temperature is 80 - 200 °C, and the drying time is 8 - 24 h; the conditions for calcination include: the calcination temperature is 400 - 600 °C, and the calcination time is 2 - 12 h.

9. An iron-ruthenium synergistic catalyst prepared by the preparation method according to any one of claims 1-8, characterized in that, Based on the total weight of the catalyst being 100 wt%, the components and their content ranges in the catalyst are as follows: The content of iron oxide is 30 - 75%, preferably 30 - 60%; The content of ruthenium is 0.5 - 10%, preferably 2 - 5%; The content of potassium oxide is 0.5 - 20%; preferably 5 - 15%; The content of alumina or silica is 20 - 50%, preferably 20 - 40%; The balance is the total content of the promoter components.

10. The application of the iron-ruthenium synergistic catalyst prepared by the preparation method according to any one of claims 1 - 8 or the iron-ruthenium synergistic catalyst according to claim 9 in the synthesis of ammonia reaction; Preferably, the reaction conditions of the synthesis of ammonia reaction include: The temperature is 200°C - 500°C, the pressure is 5 MPa - 15 MPa, and the space velocity is 1000 h -1 -30000 h -1 .

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