Synthetic ammonia catalyst as well as preparation method and application thereof

Abstract

The invention discloses a synthetic ammonia catalyst and a preparation method and application thereof, and relates to the technical field of catalysts. The method comprises the following steps: preparing a rare earth metal solid solution from a rare earth metal precursor, compounding an electronic auxiliary agent with the rare earth metal solid solution to obtain an electronic auxiliary agent promoted rare earth metal solid solution, and loading an active component on the electronic auxiliary agent promoted rare earth metal solid solution to obtain the synthetic ammonia catalyst, wherein the mass content of the rare earth metal solid solution is 60-98.5%, the mass content of the electronic auxiliary agent is 1-10%, the mass content of the active component is 0.5-30%, and the sum of the mass content of the rare earth metal solid solution, the mass content of the electronic auxiliary agent and the mass content of the active component is 100%. According to the method, the ammonia production activity of the catalyst can be improved, and ammonia can be efficiently synthesized under mild conditions (the pressure is 1t and 30bar, and the temperature is 200-400 DEG C).

Description

Technical Field

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

[0002] Ammonia (NH 3 ) is an essential chemical commodity for synthesizing chemical fertilizers, pharmaceuticals, fine chemical products, and plastics, and is the cornerstone of modern civilization. NH 3 has a rich weight hydrogen density (17.8 wt%), is easy to liquefy, and is convenient for storage and transportation, thus having great potential as a direct fuel and hydrogen carrier. Nowadays, industrial-scale NH 3 synthesis is achieved through the energy-intensive Haber-Bosch process, with an annual output of approximately 170 million tons. However, the Haber-Bosch process has high requirements for equipment conditions and requires reaction conditions of high temperature (300 - 600 °C) and high pressure (200 - 300 bar). Such high-temperature and high-pressure reaction conditions pose certain safety hazards while also causing serious energy consumption and environmental pollution. The CO 2 greenhouse gas emissions from the ammonia synthesis reaction account for 1% of the global total every year. Therefore, it is particularly important to optimize the ammonia synthesis technology to match it with China's industrial chain and energy industrial structure.

[0003] For the Haber-Bosch process, the research focus lies in the development of new low-temperature and low-pressure synthetic ammonia catalysts and their large-scale preparation to break through the current limitations of ammonia synthesis in terms of temperature and pressure. Currently, the catalysts for industrial ammonia synthesis are mainly iron-based catalysts and ruthenium-based catalysts. Among them, iron-based catalysts have relatively low catalytic activity, high energy consumption, and are prone to poisoning; although ruthenium-based catalysts have high catalytic activity, as precious metals, the high usage cost and limited lifespan of ruthenium limit their large-scale application.

[0004] Therefore, providing a catalyst capable of efficiently synthesizing ammonia under mild conditions is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0005] The present invention discloses a synthetic ammonia catalyst, a preparation method thereof, and an application thereof to solve the technical problems that the iron-based catalyst in the related art has relatively low catalytic activity, high energy consumption, and is prone to poisoning, and the ruthenium-based catalyst has high cost and limited service life.

[0006] To solve the above problems, the present invention adopts the following technical solutions: The first aspect of the present invention discloses a preparation method of a synthetic ammonia catalyst.

[0007] The preparation method of the ammonia synthesis catalyst of the present invention includes the following steps: Step 100: Prepare a rare earth metal solid solution through a rare earth metal precursor. The rare earth metal solid solution is a solid solution formed by one or two rare earth metal precursors among Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu; Step 200: Compound an electronic promoter with the rare earth metal solid solution to obtain an electronic promoter-promoted rare earth metal solid solution. The electronic promoter is one of Li, Na, K, Rb, Cs, Ca, Sr, and Ba; Step 300: Load the active component onto the electronic promoter-promoted rare earth metal solid solution to obtain an ammonia synthesis catalyst. The active component is one of Fe, Co, Ni, Mn, Cr, W, and Mo; Among them, the mass content of the rare earth metal solid solution is 60-98.5%, the mass content of the electronic promoter is 1-10%, the mass content of the active component is 0.5-30%, and the sum of the mass contents of the rare earth metal solid solution, the electronic promoter, and the active component is 100%.

[0008] According to an optional embodiment, in step 100, the preparation of the rare earth metal solid solution includes the following steps: Step 110: Dissolve the rare earth metal precursor in a first solvent to obtain a rare earth metal solution; Step 120: Adjust the pH of the rare earth metal solution to 6-9; Step 130: Hydrothermally treat the rare earth metal solution at a temperature of 100-180 °C for 12-24 h, or co-precipitate the rare earth metal solution for 12-24 h; Step 140: Centrifuge and wash the hydrothermally treated or co-precipitated rare earth metal solution until it is neutral, then dry it and calcine it at 400-700 °C for 2-5 h to obtain the rare earth metal solid solution.

[0009] According to an optional embodiment, in step 110, the first solvent is one of water, ethanol, cyclohexane, toluene, and tetrahydrofuran; In step 120, the solution used to adjust the pH of the rare earth metal solution is one of sodium hydroxide, ammonia water, sodium carbonate, and sodium bicarbonate.

[0010] According to an optional embodiment, in step 200, the electronic promoter is compounded with the rare earth metal solid solution by an impregnation method, and the compounding of the electronic promoter with the rare earth metal solid solution by the impregnation method includes the following steps: Step 210: Dissolve the electronic promoter in a second solvent to obtain an electronic promoter solution; Step 220: Immerse the electronic promoter solution and the rare earth metal solid solution at a temperature of 40 - 80 °C for 0.5 - 2 h to obtain a precursor of the rare earth metal solid solution promoted by the electronic promoter; Step 230: Calcinate the precursor of the rare earth metal solid solution promoted by the electronic promoter at 400 - 700 °C for 2 - 5 h to obtain the rare earth metal solid solution promoted by the electronic promoter.

[0011] According to an optional embodiment, in Step 210, the second solvent is one of water, ethanol, and cyclohexane.

[0012] According to an optional embodiment, in Step 300, the active component is loaded onto the rare earth metal solid solution promoted by the electronic promoter by the impregnation method, and loading the active component onto the rare earth metal solid solution promoted by the electronic promoter by the impregnation method includes the following steps: Step 310: Dissolve the active component in a third solvent to obtain an active component solution; Step 320: Immerse the active component and the rare earth metal solid solution promoted by the electronic promoter at a temperature of 40 - 80 °C for 0.5 - 2 h to obtain a precursor of the ammonia synthesis catalyst; Step 330: Dry the precursor of the ammonia synthesis catalyst, calcinate it at 400 - 700 °C for 2 - 5 h, and quickly cool the precursor of the ammonia synthesis catalyst to room temperature by means of gas purging, and the cooling rate is 20 - 50 °C / min to obtain the ammonia synthesis catalyst.

[0013] According to an optional embodiment, in Step 310, the third solvent is one of water, ethanol, and cyclohexane.

[0014] According to an optional embodiment, before using the ammonia synthesis catalyst, it further includes a step of performing activation pretreatment on the ammonia synthesis catalyst, and the ammonia synthesis catalyst is subjected to activation pretreatment in one of a vacuum atmosphere, an air atmosphere, a nitrogen atmosphere, an argon atmosphere, a hydrogen atmosphere, and an ammonia atmosphere. The activation pretreatment temperature is 300 - 500 °C, the pretreatment pressure is 1 - 30 bar, and the pretreatment time is 6 - 48 h.

[0015] The second aspect of the present invention discloses an ammonia synthesis catalyst.

[0016] The ammonia synthesis catalyst prepared by the preparation method of the ammonia synthesis catalyst according to any one of the technical solutions of the present invention includes the following components: A rare earth metal solid solution, which is a solid solution formed by one or two rare earth metal elements selected from Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu; An electronic promoter, the electronic promoter is one of Li, Na, K, Rb, Cs, Ca, Sr, Ba; An active component, the active component is one of Fe, Co, Ni, Mn, Cr, W, Mo; Wherein, the mass content of the rare earth metal solid solution is 60-98.5%, the mass content of the electronic promoter is 1-10%, the mass content of the active component is 0.5-30%, and the sum of the mass contents of the rare earth metal solid solution, the electronic promoter and the active component is 100%.

[0017] The third aspect of the present invention discloses the application of the ammonia synthesis catalyst.

[0018] The application of the ammonia synthesis catalyst described in any one of the technical solutions of the present invention in the ammonia synthesis process, the reaction temperature in the ammonia synthesis process is 200-400 °C, the reaction pressure is 1-30 bar, and the reaction space velocity is 20000-200000 mlg cat -1 h -1 。

[0019] The technical solution adopted by the present invention can achieve the following beneficial effects: First, the ammonia synthesis catalyst of the present invention includes a rare earth metal solid solution, an electronic promoter and an active component. The rare earth metal solid solution is a solid solution formed by one or two rare earth metal precursors among Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu. The electronic promoter is one of Li, Na, K, Rb, Cs, Ca, Sr, Ba, and the active component is one of Fe, Co, Ni, Mn, Cr, W, Mo; The catalyst of this system can promote the activation and reduction of N 2 molecules through the efficient electron conduction of the rare earth metal solid solution and the alkali (earth) metal promoter, thereby enhancing the ammonia production activity of the catalyst. When this catalyst is used in the ammonia synthesis process, ammonia can be efficiently synthesized under mild conditions (pressure < 30 bar, temperature 200-400 °C). Compared with the iron-based catalyst, the ammonia synthesis catalyst of the present invention has higher catalytic activity and service life, thus effectively reducing the energy consumption of the ammonia synthesis process; Compared with the ruthenium-based catalyst, the active sites of the ammonia synthesis catalyst of the present invention are provided by non-noble metals, which is beneficial to the industrial application of the catalyst.

[0020] That is, the ammonia synthesis catalyst of the present invention solves the technical problems of the iron-based catalyst in the related art, such as low catalytic activity, high energy consumption, easy poisoning, and the ruthenium-based catalyst has high cost and limited service life.

[0021] In a second aspect, the preparation method of the ammonia synthesis catalyst of the present invention makes the rare earth metal solid solution, electronic promoter and active component composite by a step-by-step composite method, which can uniformly load the electronic promoter on the rare earth metal solid solution and uniformly load the active component on the rare earth metal solid solution promoted by the electronic promoter, so as to improve the uniformity of the distribution of each element in the obtained alloy, reduce the element segregation phenomenon, and thus is beneficial to improving the uniformity of the surface activity, the surface adsorption capacity, the thermal stability and the mechanical stability of the ammonia synthesis catalyst, and further is beneficial to improving the activity and stability of the ammonia synthesis catalyst. In addition, the preparation method of the ammonia synthesis catalyst of the present invention adopts a step-by-step composite method, which is also beneficial to controlling the loading amount and distribution position of each metal and further improving the uniformity of the distribution of each element in the obtained alloy.

[0022] In a third aspect, the ammonia synthesis catalyst of the present invention is a ternary or quaternary alloy composed of a rare earth metal solid solution, an electronic promoter and an active component. Compared with a quinary or more alloy, due to the fewer types of alloys, it is easier to achieve the uniform distribution of elements during the synthesis process, so as to further reduce the element segregation phenomenon to improve the activity and stability of the ammonia synthesis catalyst; it is also beneficial to reduce the catalyst cost.

[0023] In a fourth aspect, the preparation method of the ammonia synthesis catalyst of the present invention makes the electronic promoter and the rare earth metal solid solution composite by an impregnation method and loads the active component on the rare earth metal solid solution promoted by the electronic promoter by an impregnation method, which can uniformly load the electronic promoter on the rare earth metal solid solution and also can uniformly load the active component on the rare earth metal solid solution promoted by the electronic promoter; in addition, compared with other methods (such as ball milling method), the impregnation method can also accurately adjust the loading amount and has the advantages of simple operation and low requirements for equipment.

[0024] In a fifth aspect, the preparation method of the ammonia synthesis catalyst of the present invention quickly cools the ammonia synthesis catalyst precursor to room temperature by means of gas purging. The way of rapid cooling can limit the metal elements inside the solid phase and inhibit the diffusion of elements in the solid phase, so that the metal elements can be uniformly dispersed on the carrier, and further reduce the element segregation phenomenon; and due to the strong interaction between metals, the introduced metals can be more stably loaded on the solid solution, thereby improving the mechanical properties and thermal stability of the ammonia synthesis catalyst. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0026] Figure 1 It is the SEM image of the ammonia synthesis catalyst obtained in Example 1 of this application; Figure 2 It is the detection result graph of the ammonia synthesis rate of the ammonia synthesis catalysts obtained in Examples 1-6 of this application under a mixed gas of N 2 / H 2 with a volume ratio of 1:3 varying with temperature; Figure 3 It is the detection result graph of the ammonia synthesis rate of the catalyst obtained in Example 3 varying with the reaction pressure under a mixed gas of N 2 / H 2 with a volume ratio of 1:3 at temperatures of 300°C and 400°C; Figure 4 It is the test result graph of the ammonia synthesis stability of the catalyst obtained in Example 3 under a mixed gas of N 2 / H 2 with a volume ratio of 1:3 at 30 bar, 400°C; Detailed implementation manners

[0027] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope protected by the present invention.

[0028] The terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of this application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of the same type, and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / ", generally represents an "or" relationship between the associated objects before and after.

[0029] Unless otherwise specified, all numbers appearing in the description and claims of this application, such as values of active components, temperature and time, gas conversion rate, etc., should not be understood as absolute exact values. Due to the standard deviation of the measurement technology, there will inevitably be certain experimental errors in the measured values.

[0030] Unless otherwise specified, the raw materials and reagents in the embodiments of this application can be obtained through commercial channels. In the embodiments of the present application, the ammonia synthesis reaction is carried out on a fixed-bed micro-reactor using a stainless-steel reactor. The reaction gas components are analyzed by a conductivity meter (Shanghai Leici DDS-307A conductivity meter). The reaction tail gas is introduced into a dilute sulfuric acid solution, and at the same time, the conductivity meter is used to track the change of the solution conductivity. Finally, the ammonia production rate is deduced and calculated from the change of the conductivity.

[0031] The ammonia synthesis catalyst of the present application, its preparation method and application will be described in detail below through specific embodiments.

[0032] Example 1 Preparation of rare earth metal solid solution: Dissolve La(NO 3 ) 3 ·6H 2 O (0.866 g) and Ce(NO 3 ) 3 ·6H 2 O (0.868 g) in 70 ml of water, then dissolve NaOH (19.2 g) in 10 ml of water, and then mix the two solutions and stir for 1 h. Put the mixed solution into a hydrothermal autoclave and keep it hydrothermal at 100 °C for 12 h. Centrifuge and wash the hydrothermal solution until it is neutral, dry it, and calcine it at 500 °C for 2 h to obtain (La 0.5 Ce 0.5 ) 2 O 3 support.

[0033] Loading of alkali (earth) metal onto rare earth metal solid solution: Prepare a 1 wt% aqueous solution of Ba(NO 3 ) 2 . Take 600 mg of the above rare earth metal oxide and 10.1196 g of 1 wt% Ba(NO 3 ) 2 solution (calculated according to the fraction of Ba / (Ba+(La+Ce)) being 10%), and use the impregnation method for loading with an impregnation time of 1 h. After impregnation, dry it and calcine it at 700 °C for 3 h to obtain 8.86 wt% Ba-(La 0.5 Ce 0.5 ) 2 O 3 support.

[0034] Loading of non-noble metal onto alkali (earth) metal-promoted rare earth metal solid solution: Dissolve the Co precursor Co(acac) 2 (0.176 g) in tetrahydrofuran (calculated according to the Co mass fraction being 20%). Take the above 8.86 wt% Ba-(La 0.5 Ce 0.5 ) 2 O 3The carrier is 200 mg. The impregnation method is used for loading, and the impregnation time is 0.5 h. After impregnation, it is dried and calcined in an atmosphere of 50% H in Ar at 500 °C for 3 h to obtain a 20 wt% Co / 8.86 wt% Ba-(La 2 Ce 0.5 Ce 0.5 ) 2 O 3 catalyst.

[0035] The obtained catalyst is placed in a fixed-bed reactor and heated to the activation temperature (500 °C) in an atmosphere of N 2 / H 2 (volume ratio 1:3), and activated at a pressure of 10 bar for 6 h. The activity of the activated catalyst is tested in the same device.

[0036] The catalyst is heated to 200 °C, 250 °C, 300 °C, 350 °C, 400 °C in an atmosphere of N 2 / H 2 (volume ratio 1:3), the pressure is maintained at 10 bar, and the volume space velocity is 72000 mlg cat -1 h -1 . After the catalyst activity test is stable for 1 h, a conductivity meter is used to take samples for test and analysis. The test results are as Figure 2 shown.

[0037] Example 2 Preparation of rare earth metal solid solution: Dissolve La(NO 3 ) 3 ·6H 2 O (0.866 g) and Pr(NO 3 ) 3 ·6H 2 O (0.870 g) in 70 ml of water, then dissolve NaOH (19.2 g) in 10 ml of water, and then mix the two solutions and stir for 1 h. The mixed solution is loaded into a hydrothermal autoclave and hydrothermally treated at 100 °C for 12 h. The hydrothermally treated solution is centrifuged and washed until neutral, dried, and calcined at 500 °C for 2 h to obtain (La 0.5 Pr 0.5 ) 2 O 3 carrier.

[0038] Loading of alkali (earth) metal onto rare earth metal solid solution: Prepare an aqueous solution of 1 wt% Ba(NO 3 ) 2 . Take 600 mg of the above rare earth metal oxide and take 1 wt% Ba(NO 3 ) 2Solution 10.1196 g (calculated according to the Ba / (Ba+(La+Pr)) fraction of 10%), loaded by the impregnation method, with an impregnation time of 1 h. After impregnation, it is dried and calcined at 700 °C for 3 h to obtain 8.86 wt% Ba-(La 0.5 Pr 0.5 ) 2 O 3 support.

[0039] Loading of non-noble metal onto an alkali (earth) metal-promoted rare earth metal solid solution: Dissolve the Fe precursor Fe 2 (CO) 9 (0.162 g) in tetrahydrofuran (calculated according to the Fe mass fraction of 20%). Take 200 mg of the above 8.86 wt% Ba-(La 0.5 Pr 0.5 ) 2 O 3 support. Load it by the impregnation method, with an impregnation time of 0.5 h. After impregnation, it is dried and calcined in an atmosphere of 50% H 2 in Ar at 500 °C for 3 h to obtain 20 wt% Fe / 8.86 wt% Ba-(La 0.5 Pr 0.5 ) 2 O 3 catalyst.

[0040] Place the obtained catalyst into a fixed-bed reactor, heat it up to the activation temperature (500 °C) in an atmosphere of N 2 / H 2 (volume ratio of 1:1), maintain a pressure of 10 bar for activation, and the activation time is 6 h. Test the activity of the activated catalyst in the same device.

[0041] The catalyst is heated to 200 °C, 250 °C, 300 °C, 350 °C, 400 °C in an atmosphere of N 2 / H 2 (volume ratio of 1:3), the pressure is maintained at 10 bar, and the volume space velocity is 72000 mlg cat -1 h -1 . After the catalyst activity test is stable for 1 h, sample and test it using a conductivity meter. The test results are as Figure 2 shown.

[0042] Example 3 Preparation of rare earth metal solid solution: Dissolve Ce(NO 3 ) 3 ·6H 2 O (0.868 g) and Pr(NO 3 ) 3·6H 2 O (0.870 g) was dissolved in 70 ml of water, and then NaOH (19.2 g) was dissolved in 10 ml of water. Then the two solutions were mixed and stirred for 1 h. The mixed solution was placed in a hydrothermal autoclave and hydrothermally treated at 100 °C for 12 h. The hydrothermally treated solution was centrifuged and washed until neutral, dried, and calcined at 500 °C for 2 h to obtain (Ce 0.5 Pr 0.5 ) 2 O 3 support.

[0043] Alkali (earth) metal loading onto rare earth metal solid solution: Ba(NO 3 ) 2 was prepared into a 1 wt% aqueous solution. 600 mg of the above rare earth metal oxide was taken, and 10.1196 g of 1 wt% Ba(NO 3 ) 2 solution (calculated according to the fraction of Ba / (Ba+(Ce+Pr)) being 10%) was taken and loaded using the impregnation method for 1 h. After impregnation, it was dried and calcined at 700 °C for 3 h to obtain 8.86 wt% Ba-(Ce 0.5 Pr 0.5 ) 2 O 3 support.

[0044] Non-noble metal loading onto alkali (earth) metal promoted rare earth metal solid solution: The Ni precursor Ni(acac) 2 (0.160 g) was dissolved in tetrahydrofuran (calculated according to the Ni mass fraction being 20%). 200 mg of the above 8.86 wt% Ba-(Ce 0.5 Pr 0.5 ) 2 O 3 support was taken. It was loaded using the impregnation method for 0.5 h. After impregnation, it was dried and calcined at 500 °C in an atmosphere of 50% H 2 in Ar for 3 h to obtain 20 wt% Ni / 8.86 wt% Ba-(Ce 0.5 Pr 0.5 ) 2 O 3 catalyst.

[0045] The obtained catalyst was placed in a fixed bed reactor and heated to the activation temperature (500 °C) in a pure hydrogen atmosphere, and activated at a pressure of 10 bar for 6 h. The activity of the activated catalyst was tested in the same apparatus.

[0046] The catalyst was in N 2 / H 2Heat up to 200 °C, 250 °C, 300 °C, 350 °C, 400 °C in an atmosphere with a volume ratio of 1:3, maintain the pressure at 10 bar, and the volume space velocity is 72000 mlg cat -1 h -1 , after the catalyst activity test stabilizes for 1 h, use a conductivity meter to take samples for testing and analysis. The test results are as Figure 2 shown.

[0047] Example 4 Preparation of rare earth metal solid solution: Dissolve Ce(NO 3 ) 3 ·6H 2 O (0.868 g) and Sm(NO 3 ) 3 ·6H 2 O (0.889 g) in 70 ml of water, then dissolve NaOH (19.2 g) in 10 ml of water, and then mix the two solutions and stir for 1 h. Put the mixed solution into a hydrothermal reactor and keep it at 100 °C for hydrothermal treatment for 12 h. Centrifuge and wash the hydrothermal solution until it is neutral, dry it, and calcine it at 500 °C for 2 h to obtain (Ce 0.5 Sm 0.5 ) 2 O 3 support.

[0048] Loading of alkali (earth) metal onto rare earth metal solid solution: Prepare an aqueous solution of Sr(NO 3 ) 2 with a concentration of 1 wt%. Take 600 mg of the above rare earth metal oxide and 8.5761 g of 1 wt% Sr(NO 3 ) 2 solution (calculated according to the Sr / (Sr+(Ce+Sm)) fraction of 10%), and use the impregnation method for loading with an impregnation time of 1 h. After impregnation, dry it and calcine it at 700 °C for 3 h to obtain 5.92 wt% Sr-(Ce 0.5 Sm 0.5 ) 2 O 3 support.

[0049] Loading of non-noble metal onto alkali (earth) metal-promoted rare earth metal solid solution: Dissolve the Mn precursor Mn 2 (CO) 10 (0.177 g) in tetrahydrofuran (calculated according to the Mn mass fraction of 20%). Take 5.92 wt% Sr-(Ce 0.5 Sm 0.5 ) 2 O 3The carrier is 200 mg. The impregnation method is used for loading, and the impregnation time is 0.5 h. After impregnation, it is dried and calcined in an atmosphere of 50% H in Ar at 500 °C for 3 h to obtain a 20 wt% Mn / 5.92 wt% Sr-(Ce 2 Sm 0.5 Sm 0.5 ) 2 O 3 supported catalyst.

[0050] The obtained catalyst is placed into a fixed-bed reactor and heated to the activation temperature (500 °C) in an atmosphere of N 2 / H 2 (volume ratio 1:3), and activated at a pressure of 10 bar for 6 h. The activity of the activated catalyst is tested in the same device.

[0051] The catalyst is heated to 200 °C, 250 °C, 300 °C, 350 °C, 400 °C in an atmosphere of N 2 / H 2 (volume ratio 1:3), the pressure is maintained at 10 bar, and the volume space velocity is 72000 mlg cat -1 h -1 . After the catalyst activity test is stable for 1 h, a conductivity meter is used to sample and test and analyze. The test results are as Figure 2 shown.

[0052] Example 5 Preparation of rare earth metal solid solution: Dissolve Ce(NO 3 ) 3 ·6H 2 O (0.868 g) and Nd(NO 3 ) 3 ·6H 2 O (0.877 g) in 70 ml of water, then dissolve NaOH (19.2 g) in 10 ml of ethanol, and then mix the two solutions and stir for 1 h. The mixed solution is loaded into a hydrothermal autoclave and hydrothermally treated at 100 °C for 12 h. The hydrothermally treated solution is centrifuged and washed until neutral, dried, and calcined at 500 °C for 2 h to obtain (Ce 0.5 Nd 0.5 ) 2 O 3 support.

[0053] Loading of alkali (earth) metal onto rare earth metal solid solution: Prepare a 1 wt% aqueous solution of Ca(NO 3 ) 2 ·4H 2 O. Take 600 mg of the above rare earth metal oxide and take 1 wt% Ca(NO 3 )2 9.4738 g of solution (calculated according to the fraction of Ca / (Ca+(Ce+Nd)) being 10%), loaded using the impregnation method, with an impregnation time of 1 h. After impregnation, it is dried and calcined at 700 °C for 3 h to obtain 2.68 wt% Ca-(Ce 0.5 Nd 0.5 ) 2 O 3 support.

[0054] Loading of non-noble metals onto an alkali (earth) metal-promoted rare earth metal solid solution: Dissolve the Co precursor Co 2 (CO) 8 (0.145 g) in tetrahydrofuran (calculated according to the Co mass fraction being 20%). Take 200 mg of the above-mentioned 2.68 wt% Ca-(Ce 0.5 Nd 0.5 ) 2 O 3 support. Load using the impregnation method, with an impregnation time of 0.5 h. After impregnation, it is dried and calcined in an atmosphere of 50% H 2 in Ar at 500 °C for 3 h to obtain 20 wt% Co / 2.68 wt% Ba-(Ce 0.5 Nd 0.5 ) 2 O 3 support catalyst.

[0055] Place the obtained catalyst in a fixed-bed reactor, heat it to the activation temperature (500 °C) in an atmosphere of N 2 / H 2 (volume ratio 1:3), maintain a pressure of 10 bar for activation, and the activation time is 6 h. Test the activity of the activated catalyst in the same device.

[0056] The catalyst is heated to 200 °C, 250 °C, 300 °C, 350 °C, 400 °C in an atmosphere of N 2 / H 2 (volume ratio 1:3), the pressure is maintained at 10 bar, and the volume space velocity is 72000 mlg cat -1 h -1 . After the catalyst activity test stabilizes for 1 h, sample and test it using a conductivity meter. The test results are as Figure 2 shown.

[0057] Example 6 Preparation of rare earth metal solid solution: Dissolve Ce(NO 3 ) 3 ·6H 2 O (0.868 g) and Eu(NO 3 )3 ·6H 2 O (0.892 g) was dissolved in 70 ml of water, and then NaOH (19.2 g) was dissolved in 10 ml of water. Then the two solutions were mixed and stirred for 1 h. The mixed solution was placed in a hydrothermal autoclave and hydrothermally treated at 100 °C for 12 h. The hydrothermally treated solution was centrifuged and washed until neutral, dried, and calcined at 500 °C for 2 h to obtain (Ce 0.5 Eu 0.5 ) 2 O 3 support.

[0058] Alkali (earth) metal loaded onto rare earth metal solid solution: Ba(NO 3 ) 2 was configured into a 1 wt% aqueous solution. 600 mg of the above rare earth metal oxide was taken, and 10.1196 g of 1 wt% Ba(NO 3 ) 2 solution (calculated according to the Ba / (Ba+(Ce+Eu)) fraction of 10%) was taken and loaded using the impregnation method for 1 h. After impregnation, it was dried and calcined at 700 °C for 3 h to obtain 8.86 wt% Ba-(Ce 0.5 Eu 0.5 ) 2 O 3 support.

[0059] Non-noble metal loaded onto alkali (earth) metal promoted rare earth metal solid solution: The Co precursor Co(acac) 2 (0.176 g) was dissolved in tetrahydrofuran (calculated according to the Co mass fraction of 20%). 200 mg of the above 8.86 wt% Ba-(Ce 0.5 Eu 0.5 ) 2 O 3 support was taken. It was loaded using the impregnation method for 0.5 h. After impregnation, it was dried and calcined at 500 °C in an atmosphere of 50% H 2 in Ar for 3 h to obtain 20 wt% Co / 8.86 wt% Ba-(Ce 0.5 Eu 0.5 ) 2 O 3 supported catalyst.

[0060] The obtained catalyst was placed in a fixed bed reactor and heated to the activation temperature (500 °C) in an atmosphere of N 2 , and activated at a pressure of 10 bar for 6 h. The activity of the activated catalyst was tested in the same device.

[0061] The catalyst was in N 2 / H2 The temperature was raised to 200°C, 250°C, 300°C, 350°C, and 400°C in an atmosphere of 1:3 (volume ratio), the pressure was maintained at 10 bar, and the volumetric space velocity was 72000 ml / g cat -1 h -1 After the catalyst activity test is stable for 1 hour, use the conductivity meter to take samples for testing and analysis. The test results are as follows: Figure 2 shown.

[0062] Example 7 The catalyst obtained in Example 3 was placed in a fixed bed reactor, heated to the activation temperature (500°C) in a pure hydrogen atmosphere, and activated at a pressure of 10 bar for 6 hours. The activity of the activated catalyst was tested in the same device.

[0063] Catalyst in N 2 / H 2 The temperature was raised to 300°C in an atmosphere of 1:3 (volume ratio), and the pressure was maintained at 1 bar, 2 bar, 4 bar, 6 bar, 8 bar, 10 bar, 15 bar, 20 bar, 25 bar, and 30 bar, respectively, with a volume space velocity of 72000 ml / g. cat -1 h -1 After the catalyst activity test is stable for 1 hour, use the conductivity meter to take samples for testing and analysis. The test results are as follows: Figure 3 shown.

[0064] Example 8 The catalyst obtained in Example 3 was placed in a fixed bed reactor, heated to the activation temperature (500°C) in a pure hydrogen atmosphere, and activated at a pressure of 10 bar for 6 hours. The activity of the activated catalyst was tested in the same device.

[0065] Catalyst in N 2 / H 2 The temperature was raised to 400°C in an atmosphere of 1:3 (volume ratio), and the pressure was maintained at 1 bar, 5 bar, 10 bar, 15 bar, 20 bar, 25 bar, and 30 bar, respectively, with a volumetric space velocity of 72000 ml / g. cat -1 h -1 After the catalyst activity test is stable for 1 hour, use the conductivity meter to take samples for testing and analysis. The test results are as follows: Figure 3 shown.

[0066] Example 9 The catalyst obtained in Example 3 was placed in a fixed-bed reactor and heated to the activation temperature (500 °C) in an atmosphere of pure hydrogen, and activated under a pressure of 10 bar for 6 h. The activity of the activated catalyst was tested in the same apparatus.

[0067] The catalyst was heated to 400 °C in an atmosphere of N 2 / H 2 (volume ratio 1:3), the pressure was maintained at 30 bar, and the volumetric space velocity was 72000 mlg cat -1 h -1 . After the catalyst activity test was stable for 1 h, a conductivity meter was used to take samples for test analysis. Specifically, when testing the stability of the catalyst, within the first 30 min, the catalyst activity was tested at intervals of about 5 min; from 30 min to 100 min, the catalyst activity was tested at intervals of about 10 min; after 100 min, the catalyst activity was tested at intervals of 20 min - 30 min. The test results are as Figure 4 shown.

[0068] The catalyst synthesized in Example 1 was characterized by SEM, and the results are as Figure 1 shown. From Figure 1 the first and second pictures, it can be seen that the morphology of the support is mainly nanorod morphology, and the rare earth metal nanorod solid solution has more active sites for ammonia synthesis reaction. From Figure 1 the third and fourth pictures, it can be seen that Co is uniformly distributed on the support.

[0069] From Figure 2 and Figure 3 , it can be seen that the ammonia synthesis catalyst synthesized in this application has high catalytic activity in the application of ammonia synthesis, far higher than that of the iron-based ammonia synthesis catalyst, and can efficiently synthesize ammonia at lower reaction temperatures and pressures. Figure 4 It can be seen that the ammonia synthesis catalyst loaded with non-noble metal catalyst in this application has excellent stability and good application prospects.

[0070] It should be noted that in this article, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of additional identical elements in the process, method, article or device including that element.

[0071] In addition, it should be noted that the scope of the methods and apparatuses in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, the features described with reference to certain examples may be combined in other examples.

[0072] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, and all should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a synthetic ammonia catalyst, characterized in that: The steps include: Step 100: preparing a rare earth metal solid solution by using a rare earth metal precursor, wherein the rare earth metal solid solution is a solid solution formed by one or two rare earth metal precursors of Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu; Step 200: Compounding an electronic auxiliary agent with a rare earth metal solid solution to obtain a rare earth metal solid solution promoted by the electronic auxiliary agent, wherein the electronic auxiliary agent is one of Li, Na, K, Rb, Cs, Ca, Sr, and Ba; Step 300: loading an active component on a rare earth metal solid solution promoted by an electronic auxiliary agent to obtain a synthetic ammonia catalyst, wherein the active component is one of Fe, Co, Ni, Mn, Cr, W, and Mo; Among them, the mass content of rare earth metal solid solution is 60~98.5%, the mass content of electronic auxiliary agent is 1~10%, the mass content of active component is 0.5~30%, and the sum of the mass content of rare earth metal solid solution, the mass content of electronic auxiliary agent and the mass content of active component is 100%.

2. The method for preparing ammonia synthesis catalyst according to claim 1, characterized in that: In step 100, preparing a rare earth metal solid solution comprises the following steps: Step 110: dissolving a rare earth metal precursor in a first solvent to obtain a rare earth metal solution; Step 120: adjusting the pH of the rare earth metal solution to 6-9; Step 130: hydrothermal the rare earth metal solution at a temperature of 100-180° C. for 12-24 hours, or co-precipitate the rare earth metal solution for 12-24 hours; Step 140: The rare earth metal solution after hydrothermal or co-precipitation is centrifugally washed to neutrality and then dried, and calcined at 400-700° C. for 2-5 hours to obtain a rare earth metal solid solution.

3. The method for preparing ammonia synthesis catalyst according to claim 2, characterized in that: In step 110, the first solvent is one of water, ethanol, cyclohexane, toluene, and tetrahydrofuran; In step 120, the solution used to adjust the pH of the rare earth metal solution is one of sodium hydroxide, ammonia water, sodium carbonate, and sodium bicarbonate.

4. The method for preparing ammonia synthesis catalyst according to claim 1, characterized in that: In step 200, the electronic auxiliary agent and the rare earth metal solid solution are compounded by an impregnation method, and the electronic auxiliary agent and the rare earth metal solid solution are compounded by an impregnation method, and the following steps are included: Step 210: dissolving the electronic auxiliary agent in the second solvent to obtain an electronic auxiliary agent solution; Step 220: Immersing the electronic auxiliary agent solution and the rare earth metal solid solution at a temperature of 40-80° C. for 0.5-2 h to obtain a rare earth metal solid solution precursor promoted by the electronic auxiliary agent; Step 230: calcining the electron-assisted rare earth metal solid solution precursor at 400-700° C. for 2-5 hours to obtain the electron-assisted rare earth metal solid solution.

5. The method for preparing ammonia synthesis catalyst according to claim 4, characterized in that: In step 210, the second solvent is one of water, ethanol and cyclohexane.

6. The method for preparing ammonia synthesis catalyst according to claim 1, characterized in that: In step 300, the active component is loaded on the rare earth metal solid solution promoted by the electron auxiliary agent by the impregnation method, and the active component is loaded on the rare earth metal solid solution promoted by the electron auxiliary agent by the impregnation method includes the following steps: Step 310: dissolving the active component in a third solvent to obtain an active component solution; Step 320: impregnating the active component and the rare earth metal solid solution promoted by the electronic auxiliary agent at a temperature of 40-80° C. for 0.5-2 h to obtain a synthetic ammonia catalyst precursor; Step 330: Dry the ammonia synthesis catalyst precursor, calcine it at 400-700° C. for 2-5 h, and quickly cool the ammonia synthesis catalyst precursor to room temperature by gas purging at a cooling rate of 20-50° C. / min to obtain an ammonia synthesis catalyst.

7. The method for preparing ammonia synthesis catalyst according to claim 6, characterized in that: In step 310, the third solvent is one of water, ethanol and cyclohexane.

8. The method for preparing ammonia synthesis catalyst according to any one of claims 1 to 7, characterized in that: Before using the synthetic ammonia catalyst, the method also includes the step of performing activation pretreatment on the synthetic ammonia catalyst, and performing activation pretreatment on the synthetic ammonia catalyst in one of vacuum atmosphere, air atmosphere, nitrogen atmosphere, argon atmosphere, hydrogen atmosphere and ammonia atmosphere, the activation pretreatment temperature is 300-500°C, the pretreatment pressure is 1-30bar, and the pretreatment time is 6-48h.

9. A synthetic ammonia catalyst prepared by the method for preparing a synthetic ammonia catalyst according to any one of claims 1 to 8, characterized in that: The components include: Rare earth metal solid solution, which is a solid solution formed by one or two rare earth metal elements among Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu; An electronic auxiliary agent, wherein the electronic auxiliary agent is one of Li, Na, K, Rb, Cs, Ca, Sr, and Ba; Active component, the active component is one of Fe, Co, Ni, Mn, Cr, W, and Mo; Among them, the mass content of rare earth metal solid solution is 60~98.5%, the mass content of electronic auxiliary agent is 1~10%, the mass content of active component is 0.5~30%, and the sum of the mass content of rare earth metal solid solution, the mass content of electronic auxiliary agent and the mass content of active component is 100%.

10. Use of the ammonia synthesis catalyst according to claim 9 in an ammonia synthesis process, characterized in that: The reaction temperature in the synthetic ammonia process is 200~400°C, the reaction pressure is 1~30bar, and the reaction space velocity is 20000~200000mlg cat -1 h -1 .

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