Method for preparing and using a three-way catalyst in which precious metals are supported in the form of single atoms.

Abstract

The present invention relates to a method for preparing a three-way catalyst in which the precious metal is in a single atomic state, a catalyst obtained by this method, and the use of this catalyst for purifying automobile exhaust gas. In the present invention, a nitrogen-containing compound is used to treat the precursor of the catalyst in which the precious metal is in a single atomic state, thereby preventing the precious metal atoms in the single atomic state from agglomerating into nanocrystalline particles. The catalyst obtained by the preparation method of the present invention is resistant to high temperatures, is not easily agglomerated, and is resistant to poisoning. The amount of precious metal used is reduced, while the purification efficiency of the catalyst for automobile exhaust gas is effectively improved.

Description

[Technical Field]

[0001] This invention belongs to the field of environmental catalysts, and more particularly to a three-way catalyst for purifying automobile exhaust gases, a method for preparing the same, and its use. [Background technology]

[0002] With the continued increase in the number of automobiles, carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx) are increasing. x Emissions of automobile-derived exhaust pollutants such as ) are also increasing. These pollutants adsorb onto the surface of smog particles and, when inhaled by humans, have a serious impact on human health. Furthermore, nitrogen oxides are a direct cause of acid rain, directly threatening the safety of the ecological environment.

[0003] Currently, catalytic catalytic conversion of pollutants emitted by gasoline vehicles is one of the most effective methods for controlling pollutant emissions. Using a three-way catalytic converter (TWC), pollutants (HC, CO, and NO) emitted from automobiles can be converted. x ) are catalytically converted into harmless gases such as carbon dioxide, nitrogen, and water that can be released into the environment. In order to control pollution caused by automobile exhaust, the requirements for automobile exhaust gas regulations are becoming stricter year by year, and the minimum standards for various pollutants are becoming increasingly stringent. Furthermore, there is a constant demand for improved degradation resistance characteristics of three-way catalysts. Until now, catalysts have responded to these strict emission regulations by increasing the amount of precious metals used. However, as the usage time of the catalyst increases, the catalytic performance of the exhaust gas purifier continues to decline, making it difficult to meet emission standards. Therefore, improving the utilization efficiency of precious metals and extending the service life of the catalyst have become the most important issues in the research and development of three-way catalysts.

[0004] Conventional three-way catalysts typically use precious metal salts to form active sites for catalytically active precious metal nanoparticles, with the catalyst consisting of these salts supported on a thermally stable support having a specific surface area. However, such three-way catalysts for automotive exhaust gases, composed of precious metal nanoparticles, have the following insurmountable problems: 1) Only a small portion of the catalytically active components exposed on the catalyst surface can participate in catalytic action, making it difficult to reduce costs as the amount of precious metal must be increased to meet emission standards. 2) The high-temperature resistance of precious metal nanoparticles as catalytic active components was insufficient to meet the required operating conditions. Specifically, precious metal nanoparticles easily aggregate and become larger, and under high-temperature conditions, they leach from the support, leading to a decrease in catalytic activity or inactivation of the catalyst. This directly and negatively impacts the service life of the three-way catalyst. 3) Precious metal nanoparticles as catalytic active components are easily poisoned, and especially when using oils with high sulfur content, catalytic activity decreases, and in more severe cases, inactivation occurs. This leads to a shortened service life of the catalyst. [Overview of the project]

[0005] The subject of protection of the present invention is a method for preparing a noble metal single-atomic three-way catalyst in which a noble metal is in a single-atom state. Step 1 involves treating a noble metal single-atomic catalyst precursor with a nitrogen-containing compound, The process includes step 2, in which a catalyst precursor treated with this nitrogen-containing compound is calcined to obtain a ternary catalyst in which the noble metal is in a single-atom state.

[0006] Nitrogen-containing compounds include NH3, dimethylformamide, urea, and C 1-20 Alkanamine, C 2-20 Alkenamine, C 1-20 Alkanediamine, C 1-20 Alkantriamine, C 4-20 Cycloalkaneamine, C 4-20 Cycloalkanediamine, C4-20 A nitrogen-containing heterocyclic ring or C 6-20 aromatic amine; preferably NH3, dimethylformamide, urea, C 1-6 alkaneamine, C 1-6 alkanediamine or C 6-20 aromatic amine; more preferably NH3, ethylenediamine, triethylamine, n-butylamine or dimethylformamide. If necessary, a solution of a nitrogen-containing compound can be used, and the solution is an aqueous solution, an alcohol solution (methanol or ethanol solution), etc. In the implementation of the present invention, aqueous ammonia with a concentration of 0.5 to 15 wt% or an aqueous solution of ethylenediamine with a concentration of 0.5 to 15 wt% is used. It is particularly preferable to use aqueous ammonia with a concentration of 0.5 to 5 wt% or an aqueous solution of ethylenediamine with a concentration of 0.5 to 5 wt%. By this nitrogen-containing compound, prevention of hydrolysis of the target noble metal cation and stabilization of noble metal atoms in a single state are achieved.

[0007] In this catalyst precursor, the noble metal is dispersed on the oxide support at sites in a single atomic state. This noble metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold and silver, and is one of these alone, two or a combination of more than two of them. As the noble metal, platinum, rhodium, palladium, iridium or ruthenium, or a combination thereof is preferable. The content of the noble metal is 0.01% to 5%, preferably 0.1 to 2%, based on the weight of the catalyst. The oxide support is a catalyst support generally used in the field of automotive exhaust gas purification, and is usually a metal oxide support. The metal oxide support includes any of alumina, silica-alumina, ceria-zirconia mixed oxide, molecular sieve or a mixture of two or more of these. The metal oxide support can be doped with BaO, La2O3, Y2O3 and other components. More preferably, the support component is a composite oxide of Al2O3 and oxide Zr-Ce-M-O x and (a mixed oxide of Al2O3and Zr-Ce-M-O xoxide) (where M is at least one selected from the group consisting of Ba, Sr, La, Y, Pr, and Nd), and in this composite oxide, the Al2O3 content is 15 to 80 wt%, and the Zr-Ce-M-O x content is 20 to 85 wt%.

[0008] In Step 1, the "treatment" includes immersing the catalyst precursor in a nitrogen-containing compound, washing it with a nitrogen-containing compound, and then performing solid-liquid separation to obtain a catalyst precursor treated with the nitrogen-containing compound.

[0009] Before Step 2, the catalyst precursor treated with this nitrogen-containing compound can be dried as needed. This drying can be carried out by oven heating or hot air heating, which are common drying methods.

[0010] In Step 2, the calcination is carried out at 200 to 600 °C, preferably 300 to 500 °C.

[0011] The inventors have found the following. That is, in the preparation of a catalyst precursor in which a noble metal is in a single-atom state, the anions contained in the noble metal salt bring impurity anions to the catalyst, whereby the noble metal atoms supported on the oxide support easily aggregate and become nanoparticles during the calcination process. As a result, it becomes difficult to produce (maintain) a catalyst in which the noble metal is dispersed in a single-atom state. By treating with a nitrogen-containing compound before high-temperature calcination, the content of impurity anions is significantly reduced, and finally the single-atom state of the noble metal is maintained, and the tendency of single atoms to aggregate into nanoparticles is suppressed.

[0012] The object of the present invention is a method for preparing a noble metal single-atomic supported three-way catalyst, comprising Step A of supporting a predetermined loading amount of a noble metal precursor on an oxide support to produce a catalyst precursor in which the noble metal is in a single-atom state, and Step B of treating the catalyst precursor in which the noble metal is in a single-atom state with a nitrogen-containing compound Step C of firing the catalyst precursor treated with the nitrogen-containing compound obtained in Step B to obtain a three-way catalyst in which the noble metal is supported in a single-atom state, is included.

[0013] This noble metal precursor is a soluble noble metal inorganic salt, noble metal organic salt or noble metal complex, and is preferably a nitrate, chloride, sulfate, acetate, acetylacetonato complex or chloro complex. "Soluble" means soluble in water or alcohol (methanol or ethanol).

[0014] The three-way catalyst in which the noble metal is in a single-atom state is dispersed on the oxide support at single-atom sites. In this case, the noble metal is one or a combination of two or more of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold and silver, preferably one or a combination of two or more of platinum, rhodium, palladium or iridium. The content of the noble metal is 0.01% to 5%, preferably 0.1 to 2% based on the weight of the catalyst. The oxide support is a catalyst support generally used in the field of automotive exhaust gas purification and is usually a metal oxide support. This includes alumina, silica-alumina, zirconia which may be stabilized, ceria, titania, ceria-zirconia composite oxide which may be stabilized, molecular sieve or a mixture of any two or more of these. The metal oxide support can be doped with components such as BaO, La2O3, Y2O3, etc. More preferably, the support component is a composite oxide of Al2O3 and oxide Zr-Ce-M-O x (where M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr and Nd), and in this composite oxide, the Al2O3 content is 15 to 80 wt%, and the Zr-Ce-M-O x content is 20 to 85 wt%.

[0015] In step A, any means known in the art can be used for supporting. These include impregnation, adsorption, ion exchange, incipient wetness impregnation, precipitation, and spray drying. In the present invention, the impregnation method is preferably used. In this method, a suitable mass (volume) of noble metal salt solution can be prepared according to the adsorption capacity of the support so that the mass of the solution is reliably adjusted to 1 to 50 times, preferably 2 to 30 times, and more preferably 4 to 25 times, the adsorption capacity of the support. The support is obtained by mixing with the noble metal salt solution, stirring thoroughly (preferably for 2 to 400 hours), and then separating the noble metal-supported catalyst precursor.

[0016] In step B, the “processing” includes immersing the catalyst precursor in a nitrogen-containing compound or washing it with a nitrogen-containing compound, followed by solid-liquid separation to obtain a catalyst precursor treated with a nitrogen-containing compound.

[0017] Nitrogen-containing compounds include NH3, dimethylformamide, urea, and C 1-20 Alkanamine, C 2-20 Alkenamine, C 1-20 Alkanediamine, C 1-20 Alkantriamine, C 4-20 Cycloalkaneamine, C 4-20 Cycloalkanediamine, C 4-20 Nitrogen-containing heterocycle or C 6-20 Aromatic amines; preferably NH3, dimethylformamide, urea, C 1-6 Alkanamine, C 1-6 Alkanediamine or C 6-20 Aromatic amines; more preferably NH3, ethylenediamine, triethylamine, n-butylamine, or dimethylformamide. Solutions of nitrogen-containing compounds (aqueous solutions, alcoholic solutions, etc.) can be used, and the alcoholic solutions are methanol or ethanol solutions. It is preferable to use a 0.5-15 wt% aqueous ammonia solution or a 0.5-15 wt% aqueous ethylenediamine solution, and it is particularly preferable to use a 0.5-5 wt% ammonia solution or a 0.5-5 wt% aqueous ethylenediamine solution.

[0018] Prior to step C, the catalyst precursor treated with this nitrogen-containing compound may be dried if necessary. Drying can be carried out by conventional drying methods such as oven heating, hot air heating, vacuum drying, or freeze-drying.

[0019] In step C, firing is carried out at 200-600°C, preferably 300-500°C.

[0020] When the properties of the noble metal salt solution are equivalent to the adsorption capacity of the support, that is, when the noble metal salt is supported using an equivolute impregnation method, the resulting catalyst can also achieve the objectives of the present invention. However, the properties of the noble metal solution are further set to be 2 to 30 times, preferably 4 to 25 times, and most preferably 5 to 10 times, the adsorption capacity of the support. The dispersion state of the noble metal on the support may be improved by lowering the concentration of the noble metal solution. On the other hand, when the concentration is reduced, the density of noble metal ions per unit volume can be reduced. Furthermore, by utilizing the property of noble metal cations to repel each other, it is possible to disperse the noble metal more effectively in repeated adsorption and desorption processes. This further contributes to the generation of a ternary catalyst precursor in which the noble metal is distributed in the state of single atoms.

[0021] In this precursor, noble metal atoms can be effectively dispersed, but many impurity anions may be present in the surrounding material. Therefore, agglomeration and aggregation of the noble metal are easily induced during subsequent drying and calcination stages, making nitrogen-containing compounds necessary to remove the impurity anions.

[0022] Further protection of the present invention relates to the use of catalysts on which noble metals are supported in a single-atom state in the purification of automobile exhaust gases, comprising preparing a ternary catalyst on which noble metals are supported in a single-atom state using the method described above, and using this catalyst for the purification of automobile exhaust gases, wherein the noble metals are dispersed in a single-atom state site on an oxide support, the catalyst is used alone or coated on a honeycomb carrier, the honeycomb carrier being an alloy honeycomb carrier and / or a ceramic honeycomb carrier. The definitions of “noble metal” and “oxide support” used to support the noble metal are as described above. Coating can be carried out using any known method such as spraying, dipping, or brushing. In the present invention, the catalyst is first prepared as a slurry with or without the addition of a binder, and then this slurry is coated onto a honeycomb carrier.

[0023] Further protection of the present invention relates to a ternary catalyst prepared by the method described above, in which a noble metal is in the state of a single atom, wherein the noble metal is one or more combinations selected from the group consisting of palladium, rhodium, and platinum, and the support components are Al2O3 and the oxide Zr-Ce-MO x It is a composite oxide in which M is selected from the group consisting of Ba, Sr, La, Y, Pr, and Nd, and in this composite oxide, the Al2O3 content is 15-80 wt% and Zr-Ce-MO x The content is 20-85 wt%, and the precious metals are dispersed in the oxide support at sites in the form of single atoms.

[0024] Definition and explanation: In this invention, "dispersion in a single-atomic site," "single-atomic state," "distribution of single atoms," "form of a single atom," or "separation state at the single-atomic level" refers to a state in which metal atoms (ions) are isolated from each other, active metal atoms do not form direct metal-metal bonds or metal-O-metal bonds, and are dispersed at the atomic level, or in which sites in a single-atomic state are dispersed. Metals in which sites in a single-atomic state are dispersed may exist in an atomic state or an ionic state, and are even more likely to exist between the atomic state and the ionic state (i.e., with two types of bond distances). In metal nanocrystals, metal atoms are bonded to each other within the same nanocrystal and do not belong to either the single-atomic state or the single-atom separation state as defined in this invention. In the case of oxide nanocrystals composed of metal atoms and oxygen atoms, although the metal atoms are separated by the oxygen atoms, the inherent metal atoms still have the potential to bond to each other. Furthermore, since the metallic nanocrystals described above can be formed after a reduction reaction, they do not belong to either the single-atom state sites or the single-atom separation state as defined in this invention. In the case of metals in the single-atom state sites protected by this invention, the atoms (ions) are theoretically completely independent of each other. However, due to random differences in preparation and handling conditions in different batches, it cannot be ruled out that the resulting product may contain small amounts of aggregated metal species, such as clusters containing several atoms or ions, nor can it be ruled out that some of the metal may be in a nanocrystalline state. In other words, in the catalyst of this invention, the active metal may be dispersed in single-atom state sites, while at the same time, some of the metal atoms may be in a cluster state, and / or some of the metal may be in a nanocrystalline state. Furthermore, with changes in the external environment, the single-atom state may change to a cluster state and / or a nanocrystalline state.The single-atom states protected in this application require a certain ratio of single precious metal atoms among the various precious metal forms present in the catalyst (single precious metal atoms, clusters, nanocrystals, etc.). The ratio of single precious metal atoms is greater than 10%, preferably greater than 20%, and particularly preferably greater than 50%. However, due to the limitations of current technical means, only relatively coarse statistical methods are available. For example, a number of randomly selected local areas in a catalyst test sample can be analyzed and characterized by aberration-corrected scanning transmission electron microscopy (AC-STEM), and random selections can be made for statistical analysis of various precious metal forms. Alternatively, the catalyst sample can be analyzed by X-ray absorption fine structure (EXAFS), which can characterize information about the entire sample, to obtain the ratio of metal-to-other-atom bonding signals to metal-metal bonding signals, or to determine the approximate ratio of single-atom states. In fact, even if the technology of the present invention is used to manufacture catalyst products that still have partial single-atom states, these products will also exhibit improved performance. Therefore, as long as the catalyst product is prepared according to the method of the present invention, the resulting ternary catalyst having the properties of a single atomic state is within the scope of the protection (claims) of this application.

[0025] In the present invention, the oxide Zr-Ce-MO x This should be understood as doped cerium-zirconium oxide, an oxide doped with other components (preferably rare earth components) in addition to the cerium and zirconium components, if necessary. In the present invention, the oxide Zr-Ce-MO x The main components are ZrO2 20-70 wt%, CeO2 20-60 wt%, La2O3 0.2-8 wt%, BaO 0-20%, Y2O3 0-7 wt%, Nd2O3 0-7 wt%, and Pr6O 11 Contains 0-6 wt%. x represents the coordinating oxygen, and X is determined from the actual amount and valence of the metal.

[0026] In this invention, a noble metal salt is supported on an oxide support. When the mass of the solution is equal to the adsorption capacity of the support, and the support is immersed in the solution, an equal volume of the solution is adsorbed onto the support. When the mass of the solution exceeds the adsorption capacity of the support, and the support is immersed in an excess of solution, this is called excess volume impregnation. In actual operation, the adsorption capacity of the support is often measured in advance, and the ratio of the adsorption capacity to the weight of the support is calculated. Subsequently, the amount of solution added is calculated according to the weight ratio of the solution to the support. For example, if 1 g of support absorbs 0.5 g of solution, the adsorption ratio is 0.5. Therefore, if the weight ratio of the solution to the support is 1:2, it is equivolute impregnation. If the weight ratio of the solution to the support is 10:1, and the mass of the solution is 20 times the adsorption capacity of the support, it is excess volume adsorption. Due to the difference in the adsorption capacity of the support, the amount of impregnation solution used in the examples of this invention can simply be considered as a multiple of the support mass.

[0027] Alkanamines are alkanes having one amine functional group, alkanediamines are alkanes having two amine functional groups, and alkanetriamines are alkanes having three amine functional groups. The alkanes mentioned above have one or more carbon atoms. 1-6 Alkyl, C 4-20 Cycloalkyl or C 6-20 It can be substituted with aromatic groups. The C-C bond of the above alkane can be substituted with an unsaturated alkene or alkyne to form an unsaturated carbon chain. 6-20 Aromatic cyclic amines refer to aromatic cyclic amine compounds having 6 to 20 carbon atoms, and aromatic groups include both aromatic groups and heteroaromatic groups. A heteroaromatic group is a group that has the properties of aromatic 2n+4 while also having some of the ring carbon atoms substituted with heteroatoms (O atoms, N atoms). 4-20 A nitrogen-containing heterocycle refers to a nitrogen-containing heterocycle having 4 to 20 ring carbon atoms. 4-20 A cycloalkaneamine or cycloalkanediamine refers to a group containing 4 to 20 ring carbon atoms and one or two amine functional groups. The cycloalkanes, nitrogen-containing heterocycles, and aromatic rings mentioned above are monocyclic or fused rings of multiple rings, with each ring being C 1-6 Alkanes may be substituted.

[0028] Inert gases should be understood as gases that are inert to reactants and products during the reaction stage and are commonly used as protective gases, including nitrogen (N2), helium (He), and argon (Ar).

[0029] A complex, also called a complex compound, includes complexes formed from noble metals or transition metals and ligands. Common ligands include halogens (fluorine, chlorine, bromine, and iodine), nitro, nitroso, cyano, amino, water molecules, and organic groups. Common complexes include chloro complexes, ammonia complexes, cyanide complexes, etc., and include chloroplatinic acid, chloroplatinate, and chloroplatinic acid hydrate. See "Handbook of Noble Metal Compounds and Complexes Synthesis (Refined)" (Yu Jianmin, 2009, Chemical Industry Press). [Effects of the Invention]

[0030] 1. In the three-way catalyst produced by the present invention, in which the precious metal is in a single-atom state, the amount of supported precious metal can be reduced (by 30% or more), while achieving or even exceeding the effect of a three-way catalyst with nanometer-sized particles and normal support capacity for the precious metal. Therefore, the cost of using automotive exhaust gas purification catalysts can be effectively reduced. 2. This three-way catalyst, in which the precious metals are in a single-atom state, is resistant to high temperatures and does not easily aggregate. Therefore, it provides a solution to improve the service life of automotive exhaust gas catalysts and achieve the goal of an exhaust gas three-way catalyst that does not require replacement throughout the lifespan of the vehicle. 3. This ternary catalyst, in which the precious metal is in a single-atom state, possesses high anti-poisoning activity and can effectively extend the catalyst's lifespan. [Brief explanation of the drawing]

[0031] [Figure 1]Figure 1 shows electron microscope images of the catalyst obtained in Example 11. (a) is a transmission electron microscope (TEM) image, (b) is a high-resolution transmission electron microscope (HR-TEM) image, and (c) is an aberration-corrected scanning transmission electron microscope (AC-STEM) image. In each image, bright spots represent the active metal dispersed at the single-atom level. [Figure 2] Figure 2 shows a high-resolution transmission electron microscope (HR-TEM) image of Comparative Example 2, where the bright spots represent aggregated active metals. [Figure 3] Figure 3 shows the catalytic performance of the catalysts in Example 11 and Comparative Example 1 for exhaust gas purification. (a) shows the catalytic activity curve for CO, (b) shows the catalytic activity curve for HC, and (c) shows the catalytic activity curve for NO. [Modes for carrying out the invention]

[0032] Terms used in the examples and their explanations: Concentration of precious metal precursors: Calculated from the mass of the metal element. For example, "Pd concentration in aqueous solution: 0.02 g / g" indicates that the amount of Pd element is 0.02 g per gram of solution. Microreactor device: Microreactor or miniature reactor Microreactor exhaust gas: Exhaust gas generated after a reaction in a microreactor or miniature reactor. HC: Alkanes, volatile alkanes min: minutes wt%: mass percent TEM: Transmission electron microscope HR-TEM: High-resolution transmission electron microscope AC-STEM: Aberration-corrected scanning transmission electron microscopy

[0033] Preparation Example 1: Preparation of Composite Oxide Supports Al2O3 and oxide Zr-Ce-MO x A composite oxide was prepared with the following: Here, M was one or more elements selected from the group consisting of Ba, Sr, La, Y, Pr, and Nd. Oxide Zr-Ce-MO xThe components are ZrO2 20-70 wt%, CeO2 15-60 wt%, La2O3 0.2-8 wt%, BaO 0-20%, Y2O3 0-7 wt%, Nd2O3 0-7 wt%, and Pr6O 11 It contained 0-6 wt%.

[0034] La-Al2O3 (Al2O3 is also selectable), cerium-zirconium solid solution, and additives were weighed according to their respective weight ratios. These raw materials were mixed with water, and a pH adjuster was added. This mixture was further mixed (stirred or ball-milled) and subjected to solid-liquid separation to obtain a composite oxide support. Here, the additive was selected from the group consisting of barium salts and strontium salts (e.g., one or more of the following: barium acetate, barium sulfate, barium carbonate, barium nitrate, strontium nitrate, strontium carbonate, and a mixture of strontium acetate). La-Al2O3 was lanthanum-doped alumina, with a lanthanum content of 1% to 10%. The cerium-zirconium solid solution was mainly a rare earth oxide containing CeO2 and ZrO2. This cerium-zirconium solid solution consists of the following components: ZrO2 20-70 wt%, CeO2 15-60 wt%, La2O3 0.2-8 wt%, Y2O3 0-7 wt%, Nd2O3 0-7 wt%, and Pr6O 11 It contained 0-6 wt%.

[0035] In this invention, the following three types of composite oxide supports were prepared. Cerium-zirconium alumina support A (hereinafter referred to as support A). The main components and composition were Al2O3 31 wt%, ZrO2 29 wt%, CeO2 16 wt%, BaO 15 wt%, La2O3 3.57 wt%, and Y2O3 1.27 wt%. Cerium-zirconium alumina support B (hereinafter referred to as support B). The main components and composition were Al2O3 42 wt%, ZrO2 36 wt%, CeO2 9 wt%, Y2O3 8 wt%, and La2O3 5 wt%. Cerium-zirconium alumina support C (hereinafter referred to as support C). The main components and composition were Al2O3 64 wt%, ZrO2 22 wt%, CeO2 8 wt%, Y2O3 2.4 wt%, and La2O3 0.8 wt%.

[0036] Preparation Example 2: Test Method for Exhaust Gas Purification Reactor: Microreactor (customized and manufactured by Beijing Shiao Technology) Analysis equipment: Exhaust gas analyzer (HORIBA, model MEXA-584L) Detection Method: Pure versions of each gas were mixed to create a simulated automobile exhaust gas. This simulated automobile exhaust gas consisted of the following components: 1.6 wt% CO, 7.67 wt% CO2, 0.23 wt% H2, 500 ppm HC (C3H8 / C3H6 = 2 / 1), 1000 ppm NO, 1.0 wt% O2, and 10 wt% H2O (water content was adjusted as needed), with N2 gas used as a balance gas. Before operating the apparatus, the water injection rate was adjusted and the six gas channels for CO, NO, HC, CO2, O2, and H2 were calibrated. After calibration, the N2 flow was measured using a flow meter and adjusted so that the total N2 flow rate was 1000 mL / min. 200 mg of catalyst, sieved through a 40-60 mesh sieve, was uniformly mixed with 1 g of silica sand and loaded into a reaction tube. This reaction tube was placed in the heating furnace of the microreactor. The detection process included the following: 1. The exhaust gas from the microreactor was introduced into an exhaust gas analyzer with a temperature program, and performance detection was performed under the temperature program. The microreactor device was set to automatic heating, and the exhaust gas analyzer with a computer program was set to automatic sampling. The temperature range was 100-400°C, and the heating rate was 10°C / min. The temperature was stabilized for 20 minutes in 20°C increments. Online sampling was performed continuously in real time (sampling interval of 1 minute). 2. At the end of the detection, gas data (provided by the exhaust gas analyzer) and temperature (provided by the microreactor) corresponding to each sampling point in the heating stage were obtained and used as temperature-conversion rate data in the performance analysis.

[0037] [Example 1] Palladium (0.66 wt%) catalyst supported on alumina (201008f) First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 3.96 g of this aqueous solution was taken and diluted with water to 120 g. 11.9 g of Al2O3 support was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on Al2O3.

[0038] [Example 2] Palladium (1.32 wt%) catalyst (201124a) supported on support A. First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 13.2 g of this aqueous solution was taken and diluted with water to 200 g. 19.7 g of support A was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on a composite oxide support.

[0039] [Example 3] Palladium (0.924 wt%) catalyst (201105a) supported on support A. First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 9.24 g of this aqueous solution was taken and diluted with water to 200 g. 19.8 g of support A was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on support A.

[0040] [Example 4] Palladium (0.66 wt%) catalyst supported on support A (200729c) First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 33.0 g of this aqueous solution was taken and diluted with water to 1000 g. 99.3 g of support A was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on support A.

[0041] [Example 4'] Palladium (0.66 wt%) catalyst (201212b) supported on support A. First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 6.60 g of this aqueous solution was taken and diluted with water to 50 g. 19.9 g of support A was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and then filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on support A.

[0042] [Example 4''] Palladium (0.66 wt%) catalyst supported on support A (201217b) First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 3.30 g of this aqueous solution was taken and diluted with water to 5.5 g. 9.93 g of support A was added to this solution for equivolute impregnation and left to stand overnight. The mixture was dried overnight at 120°C, the dried material was removed and cooled, and then immersed overnight in 2 wt% diluted ammonia water and centrifuged. The solid was dried at 120°C for 8 hours, and then calcined at 400°C for 1 hour to obtain a palladium exhaust gas purification catalyst supported on support A.

[0043] [Example 5] Palladium (0.396 wt%) catalyst (201124d) supported on support A. First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 3.96 g of this aqueous solution was taken and diluted with water to 200 g. 19.9 g of support A was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on support A.

[0044] [Example 6] Palladium (0.397 wt%) catalyst supported on support C (200820a) First, a 0.01 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 0.795 g of this aqueous solution was taken and diluted with water to 20 g. 2.0 g of support material C was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support material. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on support material C.

[0045] [Example 7] Silver (0.147 wt%) catalyst supported on support C (200831d) First, an aqueous solution of Ag with a concentration of 0.01 g / g was prepared using silver nitrate. 1.59 g of this aqueous solution was taken and diluted with water to 20.0 g. 1.98 g of support C was added to this solution and stirred overnight to completely adsorb the silver onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of silver supported on a support.

[0046] [Example 8] Rhodium (0.147 wt%) catalyst (200729e) supported on support B First, a 0.02 g / g Rh aqueous solution was prepared using a rhodium nitrate solution. 7.35 g of this aqueous solution was taken and diluted with water to 1000 g. 99.8 g of support B was added to this solution and stirred overnight to completely adsorb the rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and then filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a rhodium exhaust gas purification catalyst supported on a composite oxide support.

[0047] [Example 8'] Rhodium (0.147 wt%) catalyst (201212c) supported on support B First, a 0.02 g / g Rh aqueous solution was prepared using a rhodium nitrate solution. 1.47 g of this aqueous solution was taken and diluted with water to 50.0 g. 20.0 g of support B was added to this solution and stirred overnight to completely adsorb the rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a rhodium exhaust gas purification catalyst supported on a composite oxide support.

[0048] [Example 8''] Rhodium (0.147 wt%) catalyst (201217c) supported on support B. First, a 0.02 g / g Rh aqueous solution was prepared using a rhodium nitrate solution. 0.74 g of this aqueous solution was taken and diluted with water to 50 g. 9.98 g of support B was added to this solution for isovolume impregnation and left to stand overnight. The mixture was dried overnight at 120°C, the dried material was removed and cooled, and then immersed overnight in 2 wt% diluted ammonia water and centrifuged. The solid was dried at 120°C for 8 hours, and then calcined at 400°C for 1 hour to obtain a rhodium exhaust gas purification catalyst supported on support B.

[0049] [Example 9] Rhodium (0.103 wt%) catalyst (201124i) supported on support B First, a 0.02 g / g Rh aqueous solution was prepared using a rhodium nitrate solution. 1.03 g of this aqueous solution was taken and diluted with water to 200 g. 20 g of support B was added to this solution and stirred overnight to completely adsorb the rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of rhodium supported on support B.

[0050] [Example 10] Rhodium (0.074 wt%) catalyst (201124j) supported on support B. First, a 0.02 g / g Rh aqueous solution was prepared using a rhodium nitrate solution. 0.735 g of this aqueous solution was taken and diluted with water to 200 g. 20 g of support B was added to this solution and stirred overnight to completely adsorb the rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of rhodium supported on support B.

[0051] [Example 11] Palladium (0.795 wt%) + rhodium (0.132 wt%) catalyst supported on support C (200729a) First, aqueous solutions of palladium nitrate and rhodium nitrate were prepared at concentrations of 0.02 g / g each. 39.7 g of the aqueous palladium nitrate solution and 6.62 g of the aqueous rhodium nitrate solution were taken and diluted to 1000 g with water. 99.1 g of support C was added to these solutions and stirred overnight to completely adsorb the palladium and rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-rhodium exhaust gas purification catalyst supported on support C.

[0052] [Example 11'] Palladium (0.795 wt%) + rhodium (0.132 wt%) catalyst supported on support C (201212a) First, aqueous solutions of palladium nitrate and rhodium nitrate were prepared at concentrations of 0.02 g / g each. 7.95 g of the palladium nitrate solution and 1.32 g of the rhodium nitrate solution were taken and diluted to 50 g with water. 19.8 g of support C was added to these solutions and stirred overnight to completely adsorb the palladium and rhodium onto the surface of the support. Solid-liquid separation was performed by suction filtration, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and then subjected to suction filtration again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-rhodium exhaust gas purification catalyst supported on support C.

[0053] [Example 11''] Palladium (0.795 wt%) + rhodium (0.132 wt%) catalyst supported on support C (201217a) First, aqueous solutions of palladium nitrate and rhodium nitrate were prepared at concentrations of 0.02 g / g each. 3.97 g of the aqueous palladium nitrate solution and 0.66 g of the aqueous rhodium nitrate solution were taken and diluted to 50 g with water. 9.91 g of support C was added to these solutions for equivolute impregnation and allowed to stand overnight. Drying was carried out at 120°C for 8 hours. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-rhodium exhaust gas purification catalyst supported on support C.

[0054] [Example 12] Palladium (0.795 wt%) + rhodium (0.132 wt%) catalyst supported on support C (201202b) First, aqueous solutions of palladium nitrate and rhodium nitrate were prepared at concentrations of 0.02 g / g each. 39.7 g of the aqueous palladium nitrate solution and 6.62 g of the aqueous rhodium nitrate solution were taken and diluted to 1000 g with water. 99.1 g of support C was added to these solutions and stirred overnight to completely adsorb the palladium and rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in a 2 wt% diluted ethylenediamine aqueous solution, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-rhodium exhaust gas purification catalyst supported on support C.

[0055] [Example 13] Palladium (0.397 wt%) + silver (0.795 wt%) catalyst (200820d) supported on support C. First, aqueous solutions of palladium nitrate and silver nitrate were prepared at concentrations of 0.01 g / g each. 0.795 g of the aqueous palladium nitrate solution and 1.59 g of the aqueous silver nitrate solution were taken and diluted to 20 g with water. 2.0 g of support material C was added to these solutions and stirred overnight to completely adsorb the palladium and silver onto the surface of the support material. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and centrifuged again. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-silver exhaust gas purification catalyst supported on support material C.

[0056] [Example 14] Palladium (0.33 wt%) + platinum (0.33 wt%) catalyst supported on support A (200729d) First, aqueous solutions of palladium nitrate and platinum chloroplatinic acid were prepared at concentrations of 0.02 g / g each. 16.5 g of the palladium nitrate solution and 16.5 g of the platinum chloroplatinic acid solution were taken and diluted with water to 1000 g. 99.3 g of support A was added to these solutions and stirred overnight to completely adsorb palladium and platinum onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. The dried material was removed, cooled, immersed overnight in 2 wt% diluted ammonia water, and filtered by suction. After drying the solid overnight at 120°C, it was calcined at 400°C for 1 hour to obtain a palladium-platinum exhaust gas purification catalyst supported on support C.

[0057] [Comparative Example 1] Palladium (0.66 wt%) unimmersed catalyst supported on alumina (201204a) First, a 0.02 g / g aqueous solution of palladium was prepared using a palladium nitrate solution. 3.96 g of this aqueous solution was taken and diluted with water to 120 g. 11.9 g of Al2O3 support was added to this solution and stirred overnight to completely adsorb the palladium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. After removing the dried material and cooling, it was calcined at 400°C for 1 hour to obtain an exhaust gas purification catalyst of palladium supported on an Al2O3 support.

[0058] [Comparative Example 2] Palladium (0.795 wt%) + Rhodium (0.132 wt%) unimmersed catalyst supported on a support (201204a) First, aqueous solutions of palladium nitrate and rhodium nitrate were prepared at concentrations of 0.02 g / g each. 39.7 g of the aqueous palladium nitrate solution and 6.62 g of the aqueous rhodium nitrate solution were taken and diluted with water to 1000 g. 99.1 g of support C was added to these solutions and stirred overnight to completely adsorb the palladium and rhodium onto the surface of the support. Solid-liquid separation was performed by centrifugation, and the resulting solid was dried overnight at 120°C. After removing the dried material and cooling, it was calcined at 400°C for 1 hour to obtain a palladium-rhodium exhaust gas purification catalyst supported on support C.

[0059] Applied Examination (Experiment) (1) Comparative Test Analysis of the microstructures of the catalysts obtained in Example 11 and Comparative Example 2 revealed the following: In TEM and HR-TEM images of the catalyst from Example 11 immersed in ammonia water, no clear metal nanoparticles could be observed within the detection range. Furthermore, in the AC-STEM image, it was observed that the active metal was dispersed at the single-atom level (see Figure 1). In contrast, in the dark-field HR-TEM image of Comparative Example 2, numerous bright spots originating from aggregated noble metal were observed. This is because, since this catalyst has not undergone reduction, the noble metal exists as amorphous oxide particles and does not have the lattice fringes of the metallic state (see Figure 2).

[0060] The catalyst sample prepared using the method of Preparation Example 2 and the samples of Comparative Examples 1 and 2 were tested. The test results are shown in Table 1.

[0061] [Table 1]

[0062] The test results show that when immersed or washed with ammonia water or ethylenediamine aqueous solution, the resulting catalysts show better test results, regardless of the type of metal oxide support used. Compared to catalysts that were not washed, the catalyst's T 50 The combustion initiation temperature has decreased significantly. This result is also shown in Figure X.

[0063] From the analysis diagram of the exhaust gas test in Figure 3, it can be concluded that the exhaust gas purification effect of the catalyst in Example 11 is clearly improved compared to the catalyst in Comparative Example 2.

[0064] (2) Applied activity test - Performance test of newly prepared catalyst Catalyst samples prepared according to the method of Preparation Example 2 were tested. The results are shown in Table 2.

[0065] [Table 2]

[0066] (3) Applied activity test - Catalyst degradation test Each catalyst from the respective example was placed on a ceramic boat and aged in air in a muffle furnace at 1000°C for 10 hours to test the exhaust gas purification performance of each catalyst. This experiment was conducted to simulate the catalytic activity after long-term use and to understand the high-temperature resistance and degradation performance of each catalyst. This experiment accurately reflected the catalytic performance of the catalysts under actual operating conditions.

[0067] [Table 3]

[0068] The results of this test demonstrate good high-temperature resistance activity. In the degradation test of the embodiments of the present invention, when a three-way catalyst supported with palladium and rhodium (Example 11) was subjected to the purification of three types of exhaust gases after 10 hours of aging, the combustion initiation temperature (T 50 It is shown that all of the ) temperatures drop below 250°C. Compared to commercially available long-term used products supported with the same amount of precious metal, the three-way catalyst in a single-atom state supported with a single metal species showed a lower combustion initiation temperature (T) after a 10-hour degradation test. 50 This indicates that, for example, the combustion initiation temperature for NO purification is reduced by at least 20°C, and the combustion initiation temperature for CO (T 50 The temperature has dropped by more than 50°C. Catalysts supporting a 30% reduction in the amount of precious metal show a combustion initiation temperature that is slightly lower or equivalent to that of commercially available, long-term-used products supporting 100% of the precious metal.

[0069] The embodiments of the present invention described above are for illustrative purposes only and do not limit the embodiments of the present invention. A person with ordinary skill in the art may make different variations and modifications based on these descriptions. Not all embodiments are exhaustively listed, and all explicit changes and modifications based on the technical solutions of the present invention are also within the scope of protection of the present invention.

Claims

1. A method for preparing a three-way catalyst in which precious metals are supported in the form of single atoms, Step A involves supporting a predetermined amount of a noble metal precursor onto an oxide support to generate a catalyst precursor in which the noble metal is in a single-atom state, Step B involves treating the catalyst precursor, which is in the form of a single atom of the noble metal, with a nitrogen-containing compound. Step C involves calcining the catalyst precursor treated with a nitrogen-containing compound obtained in step B to obtain a ternary catalyst in which the noble metal is in a single-atom state. The aforementioned noble metal precursor is a soluble noble metal inorganic salt, noble metal organic salt, or noble metal complex, where solubility means solubility in water or alcohol, and the alcohol is methanol or ethanol. In a three-way catalyst in which the noble metal is supported in a single-atom state, the noble metal is dispersed on the oxide support at single-atom sites, and the noble metal is one or more selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold, and silver. The oxide support is alumina, silica-alumina, ceria-zirconia composite oxide, molecular sieve, or a mixture of two or more of these, Alumina, silica-alumina, ceria-zirconia composite oxide, molecular sieve, or a mixture of two or more of these, doped with one or more selected from the group consisting of BaO, La₂O₃, and Y₂O₃, or Al ２ O ３ and oxide Zr-Ce-M-O ｘ A composite oxide of (wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, and Nd), The nitrogen-containing compound is NH ３ , dimethylformamide, urea, C １－２０ alkaneamine, C ２－２０ alkeneamine, C １－２０ alkanediamine, C １－２０ alkanetriamine or C ６－２０ aromatic amine. Preparation method.

2. The aforementioned noble metal precursor is a nitrate, chloride, sulfate, acetate, acetylacetonate complex, or chloro complex. The preparation method according to claim 1.

3. The nitrogen-containing compound is NH ３ dimethylformamide, urea, C １－６ Alkanamine, C １－６ Alkanediamine or C ６－２０ It is an aromatic amine. The preparation method according to claim 1.

4. The nitrogen-containing compound is NH ３ , ethylenediamine, triethylamine, n-butylamine, or dimethylformamide, The preparation method according to claim 1.

5. The nitrogen-containing compound is contained as an aqueous solution or alcohol solution of the nitrogen-containing compound. The aforementioned alcohol solution is a methanol solution or an ethanol solution. The preparation method according to claim 1.

6. In step A, the support is mixed with a noble metal salt solution, and the resulting mixture is separated to obtain a noble metal-supported catalyst precursor. In step B, the catalyst precursor is either immersed in a nitrogen-containing compound or washed with a nitrogen-containing compound, and then subjected to solid-liquid separation to obtain a solid catalyst precursor. In step C, firing is performed at 200-600°C. The preparation method according to any one of claims 1 to 5.

7. In step C, firing is performed at 300-500°C. The preparation method according to claim 6.

8. The aforementioned noble metal salt is a noble metal nitrate, chloride, acetate, acetylacetonate complex, or chloro complex. The aforementioned precious metals are platinum, rhodium, palladium, iridium, or a combination of two or more of these. The content of the aforementioned precious metal is 0.01 wt% to 5 wt% relative to the weight of the catalyst. The preparation method according to claim 6 or 7.

9. The content of the aforementioned precious metal is 0.05 to 2 wt% relative to the weight of the catalyst. The preparation method according to claim 8.

10. The oxide support is Al ２ O ３ and oxide Zr-Ce-M-O ｘ It is a composite oxide of Al, and in the composite oxide, Al ２ O ３ The content is 15-80 wt%, Zr-Ce-M-O ｘ The content is 20-85 wt%, The nitrogen-containing compound is an aqueous ammonia solution with a concentration of 0.5 to 15 wt% or an aqueous ethylenediamine solution with a concentration of 0.5 to 15 wt%. The preparation method according to any one of claims 1 to 9.

11. The nitrogen-containing compound is an aqueous ammonia solution with a concentration of 0.5 to 5 wt% or an aqueous ethylenediamine solution with a concentration of 0.5 to 5 wt%. The preparation method according to claim 10.

12. A method for preparing a three-way catalyst in which a precious metal is in the state of single atoms, Step 1 involves treating a catalyst precursor in which the precious metal is in a single-atom state with a nitrogen-containing compound, The process includes step 2, which involves calcining the catalyst precursor treated with the nitrogen-containing compound to obtain a ternary catalyst in which the noble metal is in a single-atom state. In the catalyst precursor, the noble metal is dispersed on a support at sites in a single-atom state, and the noble metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, gold, and silver, and the noble metal is one of these alone, two or more, or a combination thereof. The support is alumina, silica-alumina, ceria-zirconia composite oxide, molecular sieve, or a mixture of two or more of these, or BaO, La ２ O ３ , Y ２ O ３ The support is either alumina doped with Al, silica-alumina, ceria-zirconia composite oxide, molecular sieve, or a mixture of two or more of these, or the support is Al ２ O ３ and oxide Zr-Ce-M-O ｘ A composite oxide of (wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr and Nd), and in the composite oxide, Al ２ O ３ The content is 15-80 wt%, Zr-Ce-M-O ｘ The content is 20-85 wt%, The nitrogen-containing compound is NH ３ dimethylformamide, urea, C １－２０ Alkanamine, C ２－２０ Alkenamine, C １－２０ Alkanediamine, C １－２０ Alkantriamine or C ６－２０ It is an aromatic amine. Preparation method.

13. The nitrogen-containing compound is NH ３ dimethylformamide, urea, C １－６ Alkanamine, C １－６ Alkanediamine or C ６－２０ It is an aromatic amine. The preparation method according to claim 12.

14. The nitrogen-containing compound is NH ３ , ethylenediamine, triethylamine, n-butylamine, or dimethylformamide, The preparation method according to claim 12.

15. In step 1, the catalyst precursor is immersed in or washed with a nitrogen-containing compound, and then subjected to solid-liquid separation to obtain a catalyst precursor treated with a nitrogen-containing compound. In step 2, firing is performed at 200-600°C. The preparation method according to any one of claims 12 to 14.

16. The content of the aforementioned precious metal is 0.01% to 5% relative to the weight of the catalyst. The aforementioned support component is Al ２ O ３ and oxide Zr-Ce-M-O ｘ A composite oxide of (wherein M is one or more selected from the group consisting of Ba, Sr, La, Y, Pr, and Nd), In the aforementioned composite oxide, Al ２ O ３ The content is 15-80 wt%, Zr-Ce-M-O ｘ The content is 20-85 wt%. The preparation method according to any one of claims 12 to 15.

17. The nitrogen-containing compound is an aqueous ammonia solution with a concentration of 0.5 to 15 wt% or an aqueous ethylenediamine solution with a concentration of 0.5 to 15 wt%. The preparation method according to any one of claims 12 to 16.

18. Use of a three-way catalyst in which a precious metal is in a single atomic state, prepared according to the method of any one of claims 1 to 17, in the purification of automobile exhaust gases, The catalyst may be used alone or coated onto a honeycomb carrier for purifying automobile exhaust gases. The aforementioned honeycomb carrier is an alloy honeycomb carrier and / or a ceramic honeycomb carrier. use.

Images