Porous ammonia synthesis catalyst, method for producing the same, and use

Abstract

The present invention discloses a porous ammonia synthesis catalyst suitable for catalyzing an ammonia synthesis reaction using nitrogen gas and hydrogen gas as raw materials, its preparation method, and use. The porous ammonia synthesis catalyst is a novel ammonia synthesis catalyst material prepared by using a metal coordination compound as a template, uniformly dispersing the metal coordination compound in silica gel by a sol-gel method, then performing hydrothermal aging, and finally controlling the calcination conditions. Compared with conventional synthetic ammonia catalysts, the porous ammonia synthesis catalyst of the present invention has a uniform pore distribution, easy to adjust the pore size, large specific surface area, and easy to adjust the degree of aggregation of metal active centers, particle size, distribution, structure, and composition. The ammonia synthesis catalyst is highly efficient, can catalyze ammonia synthesis under mild reaction conditions, has high stability, and has low catalyst production costs, and can completely replace conventional industrial catalysts for ammonia synthesis.

Description

[Technical Field]

[0001] This invention relates to the technology for manufacturing ammonia synthesis catalysts, and more specifically to porous ammonia synthesis catalysts, methods for manufacturing the same, and uses thereof. [Background technology]

[0002] Ammonia is one of the most important raw materials for synthesizing chemical products and fertilizers, and in recent years, its potential for application in the field of hydrogen storage has been anticipated. In 1904, Haber first prepared ammonia using an iron-based catalyst under high temperature and high pressure conditions, using hydrogen and nitrogen as raw materials, and Bosch achieved industrialization of ammonia in 1913. Since then, research on ammonia synthesis has attracted attention and developed rapidly. Almquist et al. investigated the relationship between the activity of pure iron catalysts and iron components of different valencies, and confirmed that Fe3O4-based catalysts were the most active. Bridger et al. discovered that the introduction of both Al2O3-K2O auxiliary agents greatly increased the catalytic activity of iron-based catalysts. In 1979, the Imperial Chemical Corporation of the UK further enhanced catalytic activity by developing the Fe2Co catalyst using cobalt oxide as an auxiliary agent. In 1985, Liu Huazhang et al. developed an Fe catalyst with a wustite structure. 1-x The discovery that O-based catalysts have higher ammonia synthesis catalytic activity led to their industrialization. In 1992, BP and Kellogg Company jointly developed the thenium-based catalyst and its process flow (KAAP), which is recognized as a second-generation ammonia synthesis catalyst.

[0003] Iron-based catalysts used in industrial ammonia synthesis are prepared by melting Fe3O4 with different types of accelerators (such as Al2O3, CaO, and K2O) at a temperature of approximately 2000K. Moreover, the ammonia synthesis process requires high temperatures (400-600°C) and high pressures (10-30 MPa), resulting in high energy consumption (accounting for 1-2% of the world's annual energy consumption) and the emission of large amounts of greenhouse gases (such as CO2). Severe reaction conditions can also lead to serious catalyst sintering and loss of active sites. Ruthenium-based catalysts have poor stability (they tend to sinter and aggregate under high-temperature conditions and are prone to hydrogen poisoning) and are more expensive to manufacture than inexpensive transition metals. Therefore, the development of new catalysts that are inexpensive, environmentally friendly, energy-efficient, more stable, and can achieve ammonia synthesis under mild conditions is a crucial research topic in today's era. [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a porous ammonia synthesis catalyst, a method for producing it, and a method for using it, which can efficiently catalytically synthesize ammonia under low temperature and low pressure conditions, addressing the problems present in conventional ammonia synthesis catalysts, and which is expected to be used as a substitute for conventional industrial ammonia synthesis catalysts. [Means for solving the problem]

[0005] A porous ammonia synthesis catalyst is produced by a sol-gel method using a metal complex as a template agent and a silicon source as a raw material, wherein the metal complex is a compound formed by a coordination bond between a metal ion and an organic ligand, the metal ion being a mixture of one or more of the following in proportion to the metal ions: boron, aluminum, zirconium, nickel, titanium, cobalt, manganese, vanadium, chromium, iron, copper, zinc, tungsten, platinum, ruthenium, rhodium, palladium, lanthanum, cerium, praseodymium, samarium, neodymium, dysprosium, cesium, sodium, potassium, magnesium, calcium, and barium ions, and the organic ligand is an organic compound being a mixture of two or more elements from nitrogen, phosphorus, and oxygen atoms in proportion to the organic ligand.

[0006] Furthermore, the organic ligand is preferably a carboxylic acid ligand, and the carboxylic acid ligand is preferably one or more of benzoic acid, pyridinecarboxylic acid, terephthalic acid, formic acid, acetic acid, propionic acid, 1-naphthoic acid, and 2-naphthoic acid.

[0007] Furthermore, the silicon source is preferably a silicate ester or sodium metasilicate, and the silicate ester is preferably one or more of methyl orthosilicate, tetraethyl orthosilicate, tetrabutyl orthosilicate, and tetraisopropyl orthosilicate.

[0008] Furthermore, the porous ammonia synthesis catalyst is a silicate catalyst material containing metal active centers, wherein the molar ratio of silicon to metal active centers is 2 to 100:1.

[0009] Furthermore, the porous ammonia synthesis catalyst has a specific surface area of ​​50 to 800 m². 2 The pore size is 1-10 nm, and the density is per g.

[0010] Furthermore, the porous ammonia synthesis catalyst is an iron-based catalyst, and the metal ions are a mixture of iron ions and other co-catalyst element ions in a specific ratio. The other co-catalyst element ions are one or more of the following: boron, sodium, potassium, magnesium, calcium, barium, cesium, aluminum, zirconium, nickel, titanium, cobalt, manganese, vanadium, chromium, copper, zinc, tungsten, platinum, ruthenium, rhodium, palladium, lanthanum, cerium, praseodymium, samarium, neodymium, and dysprosium ions. By introducing an iron active center in situ into a porous metal silicate material and doping it with various co-catalyst elements, the catalytic efficiency of the catalyst is significantly improved.

[0011] A method for producing the porous ammonia synthesis catalyst, comprising the steps of producing it by a sol-gel method, adding a silicon source to a metal carboxylate solution, stirring until sufficiently dissolved, placing it in a hydrothermal reaction vessel, placing the hydrothermal reaction vessel in an oven to carry out a hydrothermal reaction to form a gel, drying the gel and transferring it to a muffle furnace, performing programmed heating to 100-1000°C in an air atmosphere, and calcining at a constant temperature for 1-24 hours, or placing the gel in a tubular furnace, heating to 100-1000°C in an inert atmosphere, and calcining at a constant temperature for 1-24 hours to obtain a porous ammonia synthesis catalyst.

[0012] Furthermore, the metal carboxylate solution is prepared by dissolving a carboxylic acid ligand and a metal salt in a solvent in a molar ratio of 0.5 to 10:1, wherein the metal ions in the metal salt are a mixture of one or more of the following ions in a specific ratio: boron, sodium, potassium, magnesium, calcium, barium, cesium, aluminum, zirconium, nickel, titanium, cobalt, manganese, vanadium, chromium, iron, copper, zinc, tungsten, platinum, ruthenium, rhodium, palladium, lanthanum, cerium, praseodymium, samarium, neodymium, and dysprosium, and the solvent is a mixture of one or more of the following in any ratio: water, methanol, ethanol, N,N-dimethylformamide, acetonitrile, and acetone.

[0013] Furthermore, the metal carboxylate salt is preferably a benzoate, and the metal salt is dissolved in the solvent in a molar ratio of 1-5:0.5-1.

[0014] Furthermore, the concentration of metal ions in the metal carboxylate solution is 0.1 to 1 mmol / L.

[0015] Furthermore, metal salts are substances that dissolve in solvents such as chlorides, nitrates, acetates, and sulfates.

[0016] Furthermore, the hydrothermal reaction conditions are 80°C to 200°C and 6 to 48 hours.

[0017] Use of the porous ammonia synthesis catalyst in the ammonia synthesis reaction.

[0018] Furthermore, the specific procedure is as follows: A porous ammonia synthesis catalyst and quartz sand are mixed and packed into the reactor; the reaction gas is a nitrogen-hydrogen mixed gas with a nitrogen-hydrogen ratio of 0.1 to 10:1; the reaction conditions are 0.1 to 15 MPa, the reaction temperature is 150 to 450°C, and the reaction space velocity is 1 to 72 L·g. -1 ·h -1 Let's assume that. [Effects of the Invention]

[0019] Compared to conventional technology, the present invention has the following advantages. 1. The porous ammonia synthesis catalyst of the present invention has low preparation costs, a simple process, and is pollution-free. 2. The pore size of the porous ammonia synthesis catalyst can be adjusted by controlling the mixing ratio of silicon and metal ions, the composition of the metal ions, etc., resulting in a large specific surface area and a uniform pore distribution. 3. The active metal components, structure, particle size, and distribution of porous ammonia synthesis catalysts can be easily adjusted by controlling the mixing ratio of silicon and metal ions, which in turn makes it easier to control the degree of aggregation of metal active centers and thus improves catalytic efficiency. 4. When a porous ammonia synthesis catalyst is used in a catalytic ammonia synthesis reaction, the reaction temperature and pressure are lowered, the energy consumption is low, the catalyst efficiency is high, the stability is high, it is environmentally friendly, and it can solve the problems of high energy consumption and pollution existing in conventional industrial catalysts, and the future of industrial application is expected.

Brief Description of the Drawings

[0020] [Figure 1] It is a performance diagram of the ammonia synthesis catalytic action of PMS-100, PMS-100-a, and DNCA-type ammonia synthesis catalysts at a pressure of 2 MPa and various temperature conditions.

Modes for Carrying Out the Invention

[0021] The present invention discloses a porous ammonia synthesis catalyst, a manufacturing method, and uses. This porous ammonia synthesis catalyst has a porous metal silicate as a skeleton and consists of one or more metals constituting catalytic active centers at a predetermined ratio. It has a low raw material cost, is easy to manufacture the catalyst, and has low energy consumption. When this porous ammonia synthesis catalyst is used as a catalyst for ammonia synthesis, the reaction pressure and temperature are lowered, the catalyst efficiency is high, there is no pollution, and it has high activity and can be used for a long time. The following examples are for understanding the present invention, but the scope of the claims of the present invention is not limited thereto. Example 1

[0022] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), cesium chloride (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120 °C for 3 hours, cooled to room temperature, and then left overnight while stirring. The mixed solution was put into a hydrothermal reaction kettle, aged at 160 °C for 24 h to gel, the dried solid was transferred to a muffler furnace, and calcined in an air atmosphere at 600 °C for 5 hours to obtain a solid material, named PMS-100. This porous ammonia synthesis catalyst has a specific surface area of 427 m2 The pore size was uniform, with a density of 0.96 nm per gram. Example 2

[0023] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C for 5 hours in an air atmosphere to obtain a solid material, which was named PMS-100-a. This porous ammonia synthesis catalyst has a specific surface area of ​​475 m². 2 The pore size was uniform, with a density of 0.83 nm per gram. Example 3

[0024] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), calcium chloride (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C in an air atmosphere to obtain a solid material, which was named PMS-100-b. This porous ammonia synthesis catalyst has a specific surface area of ​​456 m². 2 The pore size was uniform, the pore distribution was uniform, and the average pore size was 0.90 nm. Example 4

[0025] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), boric acid (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reaction vessel and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C in an air atmosphere to obtain a solid material, which was named PMS-100-c. This porous ammonia synthesis catalyst had a uniform pore distribution, and its specific surface area and average pore size were similar to those of the material in the above example. Example 5

[0026] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), aluminum chloride (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reaction vessel and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C in an air atmosphere to obtain a solid material, which was named PMS-100-d. This porous ammonia synthesis catalyst had a uniform pore distribution, and its specific surface area and average pore size were similar to those of the material in the above example. Example 6

[0027] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), aluminum chloride (0.112 mmol), potassium nitrate (0.224 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reaction vessel and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C in an air atmosphere to obtain a solid material, which was named PMS-100-e. This porous ammonia synthesis catalyst had a uniform pore distribution, and its specific surface area and average pore size were similar to those of the material in the above example. Example 7

[0028] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), chromium nitrate (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were added to a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reaction vessel and aged at 160°C for 24 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C in an air atmosphere to obtain a solid material, which was named PMS-100-f. This porous ammonia synthesis catalyst had a uniform pore distribution, and its specific surface area and average pore size were similar to those of the material in the above example. Example 8

[0029] Benzoic acid (13.44 mmol), iron nitrate (2.24 mmol), cerium chloride (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were added to a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120 °C for 3 hours, cooled to room temperature, and then left overnight with stirring. The mixed solution was put into a hydrothermal reaction kettle, aged at 160 °C for 24 h to gel, and the dried solid was transferred to a muffler furnace and calcined at 600 °C in an air atmosphere to obtain a solid material, named PMS-100-g. The porous ammonia synthesis catalyst had a uniform pore distribution and a specific surface area and average pore diameter similar to those of the materials in the above examples. Example 9

[0030] The activity evaluation of the catalyst was carried out in a high-pressure activity test device with an inner diameter of 8 mm of the reactor. The catalyst prepared from Examples 1 to 8 or a commercially available catalyst (see Table 1 for specific usage amounts) was mixed with a predetermined amount of quartz sand and filled into a stainless steel reactor. The reaction gas was a nitrogen-hydrogen mixed gas with a nitrogen-hydrogen ratio of 1:3, a reaction pressure of 2 MPa, a reaction temperature of 350 °C, and a reaction space velocity of 9 L·g -1 ·h -1 −1·h−1, and the reaction gas was absorbed with a dilute sulfuric acid aqueous solution, and the ammonium ion concentration in the absorption solution was measured by ion chromatography. From the results shown in Table 1, when the catalyst of the present invention was used as a catalyst for ammonia synthesis, the catalyst efficiency was much higher than that of the DNCA-type industrial ammonia synthesis catalyst and the commercial ruthenium-carbon catalyst, indicating that the present invention has excellent potential for industrial application in the future. (Table 1) Comparison table of test results of synthetic ammonia performance of Examples 1 to 10, Comparative Example 1 and Comparative Example 2 TIFF0007847384000001.tif130161 Example 10

[0031] 0.2 g of PMS-100 / PMS-100-a / DNCA was respectively mixed with a predetermined amount of quartz sand, filled into a stainless steel reactor, the reaction gas was a nitrogen-hydrogen mixed gas with a nitrogen-hydrogen ratio of 1:3, a reaction pressure of 2 MPa, and the reaction temperature was raised from 250 °C to 400 °C at a rate of 25 °C, and the reaction space velocity was 9 L·g-1 ·h -1 The reaction gas was absorbed with a dilute sulfuric acid aqueous solution at each temperature, and the ammonium ion concentration in the absorption solution was measured by ion chromatography. As can be seen from the results shown in Figure 1, the efficiency of the catalyst of the present invention is far higher than that of the DNCA type industrial ammonia synthesis catalyst. Example 11

[0032] Benzoic acid (26.88 mmol), iron nitrate (4.48 mmol), cobalt nitrate (0.112 mmol), and tetraethyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 100°C for 12 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 400°C for 8 hours in an air atmosphere to obtain a solid material. This porous ammonia synthesis catalyst has a uniform pore distribution, and its specific surface area and average pore size are similar to those of the material in the above example, resulting in good ammonia synthesis catalytic efficiency. Example 12

[0033] Formic acid (13.44 mmol), platinum nitrate (1.344 mmol), and methyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 120°C for 16 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 100°C for 24 hours in an air atmosphere to obtain a solid material. This porous ammonia synthesis catalyst has a uniform pore distribution, and its specific surface area and average pore diameter are similar to those of the material in the above example, resulting in good ammonia synthesis catalytic efficiency. Example 13

[0034] Acetic acid (1.12 mmol), cobalt nitrate (2.24 mmol), and sodium metasilicate (6.72 mmol) were added to 4 mL of water and stirred at 100°C for 4 hours. After cooling to room temperature, the mixture was left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 200°C for 20 hours to gel. The dried solid was transferred to a tubular furnace and calcined at 600°C for 1 hour in a nitrogen gas atmosphere to obtain a solid material. This porous ammonia synthesis catalyst has a uniform pore distribution, and its specific surface area and average pore diameter are similar to those of the material in the above example, resulting in good ammonia synthesis catalytic efficiency. Example 14

[0035] Terephthalic acid (13.44 mmol), rhodium chloride (2.24 mmol), cesium chloride (0.112 mmol), and chlorosilane (235.2 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 160°C for 36 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C for 4.5 hours in an air atmosphere to obtain a solid material. This porous ammonia synthesis catalyst has a uniform pore distribution, and its specific surface area and average pore diameter are similar to those of the material in the above example, resulting in good ammonia synthesis catalytic efficiency. Example 15

[0036] 1-Naphthoic acid (13.44 mmol), iron nitrate (2.24 mmol), cerium chloride (0.112 mmol), and tetraisopropyl orthosilicate (6.72 mmol) were placed in a mixed solvent of 4 mL of N,N-dimethylformamide and 0.5 mL of water, stirred at 120°C for 3 hours, cooled to room temperature, and left overnight with stirring. The mixture was placed in a hydrothermal reactor and aged at 200°C for 48 hours to gel. After drying, the solid was transferred to a muffle furnace and calcined at 600°C for 5 hours in an air atmosphere to obtain a solid material. This porous ammonia synthesis catalyst has a uniform pore distribution, and its specific surface area and average pore diameter are similar to those of the material in the above example, resulting in good ammonia synthesis catalytic efficiency.

[0037] The above are merely some examples of the present invention, and any equivalent changes and modifications made in accordance with the patent scope of the present invention application are all included within the scope of the present invention.

Claims

1. A method for producing a porous ammonia synthesis catalyst by the sol-gel method using a metal complex as a template agent and a silicon source as a raw material, The aforementioned metal complex is a compound formed via a coordination bond using a metal ion and an organic ligand. The aforementioned metal ions are a mixture of iron ions and other co-catalyst element ions in a specified ratio, and the other co-catalyst element ions are one or more of the following: boron, sodium, potassium, magnesium, calcium, barium, cesium, aluminum, zirconium, nickel, titanium, cobalt, manganese, vanadium, chromium, copper, zinc, tungsten, platinum, ruthenium, rhodium, palladium, lanthanum, cerium, praseodymium, samarium, neodymium, and dysprosium ions. The organic ligand is a carboxylic acid ligand, and the carboxylic acid ligand is one or more of the following: benzoic acid, pyridinecarboxylic acid, terephthalic acid, formic acid, acetic acid, propionic acid, 1-naphthoic acid, and 2-naphthoic acid. A method for producing a porous ammonia synthesis catalyst, characterized by the above.

2. The method for producing a porous ammonia synthesis catalyst according to claim 1, characterized in that the silicon source is a silicate ester, sodium metasilicate, or chlorosilane, and the silicate ester is one or more of methyl orthosilicate, tetraethyl orthosilicate, tetrabutyl orthosilicate, and tetraisopropyl orthosilicate.

3. The method for producing a porous ammonia synthesis catalyst according to claim 1, characterized in that the porous ammonia synthesis catalyst is a silicate catalyst material containing a metal active center, wherein the molar ratio of silicon to metal active center is 2:1 to 100:

1.

4. Specific surface area of ​​50-800 m² ２ A method for producing a porous ammonia synthesis catalyst according to claim 1, characterized in that the amount is / g and the pore size is 1 to 10 nm.

5. A method for producing a porous ammonia synthesis catalyst according to claim 1, characterized by comprising the steps of: adding the silicon source to a metal carboxylate solution, dissolving it completely, placing the solution in a hydrothermal reaction vessel, placing the hydrothermal reaction vessel in an oven to carry out a hydrothermal reaction to form a gel, drying the gel and transferring it to a muffle furnace, performing programmed heating to 100 to 1000°C in an air atmosphere, maintaining the temperature for 1 to 24 hours for calcination, or drying the gel and placing it in a tubular furnace, heating it to 100 to 1000°C in an inert atmosphere, maintaining the temperature for 1 to 24 hours for calcination, thereby obtaining the porous ammonia synthesis catalyst.

6. The method for producing a porous ammonia synthesis catalyst according to claim 5, characterized in that the metal carboxylate solution is prepared by dissolving a carboxylic acid ligand and a metal salt in a solvent in a molar ratio of 0.5 to 10:1, and the solvent is a mixture of one or more of water, methanol, ethanol, N,N-dimethylformamide, acetonitrile, and acetone in any proportion.

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