Core-shell structure three-way catalyst for reducing automobile exhaust emissions and preparation method thereof

Abstract

The present invention belongs to the technical field of automobile exhaust purification catalysts, and in particular to a core-shell structure three-way catalyst and a preparation method thereof for reducing automobile exhaust emissions. The core-shell structure three-way catalyst of the present invention includes a carrier, and a catalytic coating is coated on the wall of the carrier, and the catalytic coating includes a core-shell structure material, and the core-shell structure material is a yttrium zirconium aluminum composite oxide as a core, and the surface of the yttrium zirconium aluminum composite oxide is loaded with a noble metal active component, and the core outer layer is coated with a cerium iron zirconium composite oxide to form a shell; the weight of the yttrium zirconium aluminum composite oxide in the catalytic coating accounts for 5wt%-20wt%, and the weight of the cerium iron zirconium composite oxide in the catalytic coating accounts for 77wt%-94wt%, and the noble metal active component includes one or more of platinum Pt, palladium Pd, rhodium Rh, iridium Ir and ruthenium Ru. The core-shell structure three-way catalyst of the present invention has the characteristics of high oxygen storage, high conversion efficiency and long life.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile exhaust purification catalysts, and in particular relates to a core-shell structure three-way catalyst for reducing automobile exhaust emissions and a preparation method thereof. Background Art

[0002] With the development of society, the number of motor vehicles has continued to increase, and automobile exhaust pollution has become one of the main sources of urban air pollution, which not only endangers human health, but also has great damage to the ecological environment. Many studies have shown that various hydrocarbons in automobile exhaust are very harmful to the human body. Some of the organic components (such as polycyclic aromatic hydrocarbons such as benzene) are carcinogens and have a long-term accumulation effect in the human body. Unburned hydrocarbons can also directly stimulate people's visual and olfactory organs, causing functional impairment. In addition, hydrocarbons and nitrogen oxides will further undergo photochemical reactions under strong light to form toxic photochemical smog.

[0003] At present, all countries are formulating increasingly stringent automobile exhaust emission regulations to limit the emission of gaseous pollutants. Gasoline vehicle three-way catalyst refers to a vehicle catalyst that converts carbon monoxide (CO), hydrocarbons (THC) and nitrogen oxides (NOx) in automobile exhaust into harmless carbon dioxide (CO2), water (H2O) and nitrogen (N2) through catalytic reactions. Conventional catalysts have a short lifespan and their performance drops significantly after long-term use. Therefore, improving catalyst performance and extending service life are key issues in the current research and development of automotive exhaust purification catalysts.

[0004] Some researchers used the uniform precipitation method to load platinum in patent CN109012665B. The dispersion of platinum was improved and the catalytic activity was enhanced. However, the smaller precious metal particles tended to aggregate under high temperature conditions, shortening the service life. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a core-shell three-way catalyst for reducing automobile exhaust emissions and a preparation method thereof. The present invention forms a shell by coating a cerium-iron-zirconium composite oxide on the surface of a yttrium-zirconium-aluminum composite oxide with highly dispersed precious metals. The precious metals under the shell are prevented from being poisoned by direct contact with the exhaust gas. The thermal protection of the shell can also inhibit the aggregation and growth of the precious metals under high temperature conditions, thereby extending the service life. At the same time, the catalytic performance can be further improved by utilizing the interface interaction between the core-precious metal-shell. In addition, the interaction between iron and cerium improves the oxygen storage and release capacity of the catalyst, thereby enhancing the exhaust gas purification performance.

[0006] In order to solve the deficiencies of the prior art, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier and a catalytic coating coated on the wall surface of the carrier, wherein the catalytic coating comprises a core-shell structure material, wherein the core-shell structure material has a yttrium zirconium aluminum composite oxide as a core, wherein the surface of the yttrium zirconium aluminum composite oxide is loaded with a noble metal active component, and a cerium-iron-zirconium composite oxide is coated on the outer layer of the core to form a shell;

[0008] The weight proportion of the yttrium-zirconium-aluminum composite oxide in the catalytic coating is 5wt%-20wt%, the weight proportion of the cerium-iron-zirconium composite oxide in the catalytic coating is 77wt%-94wt%, and the precious metal active components include one or more of platinum Pt, palladium Pd, rhodium Rh, iridium Ir and ruthenium Ru.

[0009] Furthermore, the yttrium-zirconium-aluminum composite oxide includes 1wt%-10wt% of Y2O3, 5wt%-20wt% of ZrO2 and 70wt%-94wt% of Al2O3.

[0010] Furthermore, the cerium-iron-zirconium composite oxide includes 20wt%-50wt% of CeO2, 1wt%-10wt% of Fe2O3 and 40wt%-79wt% of ZrO2.

[0011] In a second aspect, the present invention provides a method for preparing a core-shell structured three-way catalyst for reducing automobile exhaust emissions, comprising the following steps:

[0012] (1) Dispersing yttrium zirconium aluminum composite oxide in water, dropping one or more of platinum dispersion, palladium solution, rhodium solution, iridium solution and ruthenium solution, stirring evenly, dropping alkaline reagent, controlling the pH to 4-6.5, drying at 80-150°C for 8-12 hours, and then calcining at 300-550°C for 1-3 hours;

[0013] (2) dispersing the yttrium zirconium aluminum composite oxide containing precious metal active components obtained in step (1) in water, ball-milling to a particle size of 0.2-2 μm, adding cerium salt, iron salt, zirconium salt and tartaric acid, stirring and dissolving, and then heating to form a sol;

[0014] (3) The sol is sprayed onto the surface of the carrier by a rotary spraying technique, aged for 0.5 hours, dried at 40-80°C for 8-12 hours, and calcined at 400-600°C for 2-4 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0015] Furthermore, in step (1), the alkaline reagent is one or more of ammonia water, ethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, monoethanolamine and triethanolamine.

[0016] Furthermore, in step (2), the cerium salt is one or more of cerium acetate, cerium carbonate, cerium sulfate, cerium ammonium nitrate, cerous carbonate dihydrate, cerous oxalate nonahydrate, cerous nitrate hexahydrate and cerous nitrate;

[0017] The iron salt is one or more of ferric chloride, ferric nitrate, ferric bromide, ferric perchlorate and ferric dihydrogen phosphate;

[0018] The zirconium salt is one or more of zirconium carbonate, zirconium citrate, zirconium isooctanoate, zirconium propionate, zirconium methacrylate, zirconium oxychloride and zirconium oxynitrate.

[0019] Furthermore, in step (2), the weight ratio of the tartaric acid to the yttrium zirconium aluminum oxide containing the precious metal active component is (0.1-1):1.

[0020] Furthermore, the method for preparing the platinum dispersion in step (1) comprises the following steps: adding a dispersant into deionized water to form a dispersant solution, and then mixing the platinum solution and the dispersant solution in a weight ratio of 1:1-1:5 and stirring the mixture to obtain a platinum dispersion.

[0021] Furthermore, in step (1), the dispersant is one or more of acetic acid, citric acid, succinic acid, lactic acid, cellulose acetate, ethyl cellulose, cellulose nitrate, cellulose acetate butyrate, hydroxypropyl cellulose, hydroxyethyl cellulose, cellulose acetate phthalate, glucose, fructose, sucrose, maltose, mannose, rhamnose, sorbitol and trehalose;

[0022] The weight ratio of the dispersant to deionized water in the dispersant solution is 1:3-3:2.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The core-shell three-way catalyst for reducing automobile exhaust emissions of the present invention uses yttrium zirconium aluminum composite oxide as the core, loads precious metal active components on the surface, and then coats the cerium iron zirconium composite oxide to the outer layer of the core to form a shell through a sol-gel method, which is then coated on a honeycomb carrier to prepare a catalyst. The obtained catalyst has the characteristics of high oxygen storage, high conversion efficiency, long service life, etc. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0026] The following examples and comparative examples all use a honeycomb straight-through cordierite carrier with a specification of Φ132.1 mm×70 mm, a pore density of 600 cpsi, a pore wall thickness of 2 mil, and a volume of 0.959 L.

[0027] Example 1

[0028] A core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier, a catalytic coating coated on the wall surface of the carrier, the catalytic coating comprising a core-shell structure material, the core-shell structure material having a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide being loaded with a noble metal active component Pt, and a cerium-iron-zirconium composite oxide being coated on the outer layer of the core to form a shell;

[0029] The coating amount of the catalytic coating is 150 g / L, the weight proportion of the yttrium zirconium aluminum composite oxide in the catalytic coating is 6 wt%, and the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3;

[0030] The weight proportion of cerium-iron-zirconium composite oxide in the catalytic coating is 93.13wt%, and the components of cerium-iron-zirconium composite oxide are 25wt% CeO2, 3wt% Fe2O3 and 72wt% ZrO2; the loading amount of the precious metal active component Pt is 36.9g / ft 3 .

[0031] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0032] (1) Preparation of platinum dispersion: 15 g of acetic acid was added to 30 g of deionized water to form a dispersant solution, and then platinum nitrate solution (containing 3 g of Pt) was added and stirred thoroughly to obtain a platinum dispersion;

[0033] (2) Disperse 20g of yttrium zirconium aluminum composite oxide (composition: 5wt% Y2O3, 10wt% ZrO2 and 85wt% Al2O3) in water, drop into platinum dispersion containing 3g Pt, stir evenly and then drop into ammonia water, control the pH to 5, dry at 100℃ for 10 hours, and then calcine at 400℃ for 2 hours;

[0034] (3) dispersing the platinum-containing yttrium-zirconium-aluminum composite oxide prepared in step (2) in water, ball-milling the mixture to a D90 particle size of 1 μm, adding 204.8 g of cerium nitrate, 30.5 g of ferric nitrate, 645.4 g of zirconium nitrate and 2 g of tartaric acid, stirring and dissolving the mixture, and heating the mixture in an electric furnace to form a sol;

[0035] (4) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0036] Example 2

[0037] A core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier, a wall surface of the carrier coated with a catalytic coating, the catalytic coating comprising a core-shell structure material, the core-shell structure material having a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide being loaded with a noble metal active component Pt, and a cerium-iron-zirconium composite oxide being coated on the outer layer of the core to form a shell;

[0038] The coating amount of the catalytic coating is 150 g / L, the weight proportion of the yttrium zirconium aluminum composite oxide in the catalytic coating is 12 wt%, and the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3;

[0039] The weight proportion of cerium-iron-zirconium composite oxide in the catalytic coating is 87.13wt%, and the components of cerium-iron-zirconium composite oxide are 25wt% CeO2, 3wt% Fe2O3 and 72wt% ZrO2; the loading amount of the precious metal active component Pt is 36.9g / ft 3 .

[0040] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0041] (1) Preparation of platinum dispersion: 21 g of cellulose acetate was added to 42 g of deionized water to form a dispersant solution, and then a platinum nitrate solution (containing 3 g of Pt) was added and stirred to obtain a platinum dispersion;

[0042] (2) Disperse 40g of yttrium zirconium aluminum composite oxide (composition: 5wt% Y2O3, 10wt% ZrO2 and 85wt% Al2O3) in water, drop into platinum dispersion containing 3g Pt, stir evenly, drop into ammonia water, control the pH to 6, dry at 100℃ for 8 hours, and then calcine at 400℃ for 2 hours;

[0043] (3) dispersing the platinum-containing yttrium-zirconium-aluminum composite oxide prepared in step (2) in water, ball-milling to a D90 particle size of 1 μm, adding 192.2 g of cerium nitrate, 28.7 g of ferric nitrate, 605.7 g of zirconium nitrate and 8 g of tartaric acid, stirring to dissolve, and then heating in an electric furnace to form a sol;

[0044] (4) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0045] Example 3

[0046] A core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier, a catalytic coating coated on the wall surface of the carrier, the catalytic coating comprising a core-shell structure material, the core-shell structure material having a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide being loaded with a noble metal active component Pd, and a cerium-iron-zirconium composite oxide being coated on the outer layer of the core to form a shell;

[0047] The coating amount of the catalytic coating is 150 g / L, and the weight proportion of the yttrium zirconium aluminum composite oxide in the catalytic coating is 12 wt%; the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3;

[0048] The weight proportion of cerium-iron-zirconium composite oxide in the catalytic coating is 87.13wt%, and the components of cerium-iron-zirconium composite oxide are 35wt% CeO2, 7wt% Fe2O3 and 58wt% ZrO2; the loading amount of the precious metal active component Pd is 36.9g / ft 3 .

[0049] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0050] (1) Disperse 40g of yttrium zirconium aluminum composite oxide (components are 5wt% Y2O3, 10wt% ZrO2 and 85wt% Al2O3) in water, drop into palladium nitrate solution containing 3g Pd, stir evenly and then drop into ammonia water, control the pH to 5.5, dry at 100℃ for 10 hours, and then calcine at 500℃ for 2 hours;

[0051] (2) dispersing the palladium-containing yttrium-zirconium-aluminum composite oxide prepared in step (1) in water, ball-milling to a D90 particle size of 2 μm, adding 270.4 g of cerium nitrate, 60.5 g of ferric nitrate, 491.7 g of zirconium nitrate and 8 g of tartaric acid, stirring to dissolve, and then heating in an electric furnace to form a sol;

[0052] (3) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0053] Example 4

[0054] A core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier, a catalytic coating coated on the wall surface of the carrier, the catalytic coating comprising a core-shell structure material, the core-shell structure material having a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide being loaded with a noble metal active component Pd, and a cerium-iron-zirconium composite oxide being coated on the outer layer of the core to form a shell;

[0055] The coating amount of the catalytic coating is 150 g / L, the weight proportion of the yttrium zirconium aluminum composite oxide in the catalytic coating is 17 wt%, and the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3;

[0056] The weight proportion of the cerium-iron-zirconium composite oxide in the catalytic coating is 82.13wt%, and the components of the cerium-iron-zirconium composite oxide are 45wt% CeO2, 7wt% Fe2O3 and 48wt% ZrO2; the Pd loading is 36.9g / ft 3 .

[0057] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0058] (1) 60g of yttrium zirconium aluminum composite oxide (composition: 5wt% Y2O3, 10wt% ZrO2 and 85wt% Al2O3) was dispersed in water, and a palladium nitrate solution containing 3g Pd was added dropwise. After stirring evenly, ammonia water was added dropwise. The pH was controlled to 6, and the mixture was dried at 100℃ for 10 hours, and then calcined at 500℃ for 2 hours.

[0059] (2) dispersing the palladium-containing yttrium-zirconium-aluminum composite oxide prepared in (2) in water, ball-milling to a D90 particle size of 1.5 μm, adding 325.4 g of cerium nitrate, 58.1 g of iron nitrate, 378.6 g of zirconium nitrate and 20 g of tartaric acid, stirring to dissolve, and then heating in an electric furnace to form a sol;

[0060] (3) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0061] Comparative Example 1

[0062] A core-shell structure three-way catalyst for reducing automobile exhaust emissions, comprising a carrier, a catalytic coating coated on the wall surface of the carrier, the catalytic coating comprising a core-shell structure material, the core-shell structure material having a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide being loaded with a noble metal active component Pt, and a cerium zirconium composite oxide being coated on the outer layer of the core to form a shell;

[0063] The coating amount of the catalytic coating is 150 g / L, the weight proportion of the yttrium zirconium aluminum composite oxide in the catalytic coating is 6 wt%, and the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3;

[0064] The weight proportion of the cerium-zirconium composite oxide in the catalytic coating is 93.13wt%, and the components of the cerium-zirconium composite oxide are 25wt% CeO2 and 75wt% ZrO2; the Pt loading is 36.9 g / ft 3 .

[0065] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0066] (1) Preparation of platinum dispersion: 15 g of acetic acid was added to 30 g of deionized water to form a dispersant solution, and then a platinum solution (containing 3 g of Pt) was added and stirred thoroughly to obtain a platinum dispersion;

[0067] (2) Disperse 20g of yttrium zirconium aluminum composite oxide (composition: 5wt% Y2O3, 10wt% ZrO2 and 85wt% Al2O3) in water, drop into platinum dispersion containing 3g Pt, stir evenly, drop into ammonia water, control the pH to 5, dry at 100℃ for 8 hours, and then calcine at 400℃ for 2 hours;

[0068] (3) dispersing the platinum-containing yttrium-zirconium-aluminum composite oxide prepared in step (2) in water, ball-milling to a D90 particle size of 1 μm, adding 204.8 g of cerium nitrate, 673.2 g of zirconium nitrate and 2 g of tartaric acid, stirring to dissolve, and then heating in an electric furnace to form a sol;

[0069] (4) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0070] Comparative Example 2

[0071] A core-shell three-way catalyst for reducing automobile exhaust emissions, wherein the coating amount of the catalytic coating is 150 g / L; the components of the yttrium zirconium aluminum composite oxide are 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3, accounting for 12 wt% of the weight in the catalytic coating;

[0072] The weight proportion of the cerium-iron-zirconium composite oxide in the catalytic coating is 87.13wt%, and the components of the cerium-iron-zirconium composite oxide are 25wt% CeO2, 3wt% Fe2O3 and 72wt% ZrO2; the Pt loading is 36.9g / ft 3 .

[0073] The preparation method of the core-shell structure three-way catalyst adopts the following process steps:

[0074] (1) 40 g of yttrium-zirconium-aluminum composite oxide (composition: 5 wt% Y2O3, 10 wt% ZrO2 and 85 wt% Al2O3) was dispersed in water, a platinum nitrate solution containing 3 g Pt was added dropwise, and then 192.2 g of cerium nitrate, 28.7 g of iron nitrate, 605.7 g of zirconium nitrate and 4.5 g of tartaric acid were added, stirred and dissolved, and then heated in an electric furnace to form a sol;

[0075] (2) The sol was sprayed onto the surface of a honeycomb carrier by a rotary spraying technique at a coating amount of 150 g / L. After aging for 0.5 hours, the sol was dried at 80°C for 12 hours and calcined at 500°C for 2 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

[0076] A method for testing a core-shell three-way catalyst for reducing automobile exhaust emissions comprises the following steps: aging the catalyst samples obtained in Examples 1-4 and Comparative Examples 1-2 in a high-temperature tube furnace at 1050° C. for 20 h under the same conditions, then encapsulating them into a purifier, and conducting a vehicle emission test according to the WLTC Type I test, wherein the engine of the test vehicle is 1.4 T, and the emission test results are shown in Table 1.

[0077] Table 1 Comparison of vehicle emissions of catalysts in Examples 1-4 and Comparative Examples 1-2

[0078] ,

[0079] Note: THC in Table 1 is the abbreviation for the total amount of hydrocarbons contained in the gas.

[0080] As shown in Table 1, the catalyst performance evaluation results show that compared with Comparative Example 1, the shell layer of Example 1 contains iron element, and the interaction between iron and cerium improves the oxygen storage and release capacity of the catalyst, and the emissions of various gaseous pollutants in the WLTC test are significantly reduced.

[0081] Compared with Comparative Example 2, the precious metal platinum of Example 2 is first precipitated with ammonia water, then further fixed by drying and calcining, and then coated with cerium-iron-zirconium composite oxide to form a shell, and the precious metal platinum under the shell avoids direct contact with the tail gas to cause poisoning. The thermal protection of the shell can also inhibit the aggregation and growth of the precious metal platinum under high temperature conditions, thereby extending the service life. At the same time, the interface interaction between the core-precious metal platinum-shell is used to further improve the catalytic performance, and the emission of various gaseous pollutants in the WLTC test is significantly reduced. In summary, compared with Comparative Examples 1-2, the three-way catalyst prepared by Examples 1-4 of the present invention has excellent tail gas purification ability in the WLTC type I test.

[0082] The core-shell three-way catalyst for reducing automobile exhaust emissions of the present invention uses yttrium zirconium aluminum composite oxide as the core, loads precious metal active components on the surface, and then coats the cerium iron zirconium composite oxide to the outer layer of the core to form a shell by a sol method, which is then coated on a honeycomb carrier to prepare a catalyst. The obtained catalyst has the characteristics of high oxygen storage, high conversion efficiency, long service life, etc.

[0083] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A core-shell three-way catalyst for reducing automobile exhaust emissions, characterized in that: The invention comprises a carrier and a catalytic coating coated on the wall surface of the carrier, wherein the catalytic coating comprises a core-shell structure material, wherein the core-shell structure material has a yttrium zirconium aluminum composite oxide as a core, the surface of the yttrium zirconium aluminum composite oxide is loaded with a noble metal active component, and a cerium-iron-zirconium composite oxide is coated on the outer layer of the core to form a shell; The weight proportion of the yttrium-zirconium-aluminum composite oxide in the catalytic coating is 5wt%-20wt%, the weight proportion of the cerium-iron-zirconium composite oxide in the catalytic coating is 77wt%-94wt%, and the precious metal active components include one or more of platinum Pt, palladium Pd, rhodium Rh, iridium Ir and ruthenium Ru.

2. The core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 1, characterized in that: The yttrium-zirconium-aluminum composite oxide includes 1wt%-10wt% of Y2O3, 5wt%-20wt% of ZrO2 and 70wt%-94wt% of Al2O3.

3. The core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 1, characterized in that: The cerium-iron-zirconium composite oxide includes 20 wt % to 50 wt % of CeO 2 , 1 wt % to 10 wt % of Fe 2 O 3 , and 40 wt % to 79 wt % of ZrO 2 .

4. The method for preparing the core-shell three-way catalyst for reducing automobile exhaust emissions according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Dispersing yttrium zirconium aluminum composite oxide in water, dropping one or more of platinum dispersion, palladium solution, rhodium solution, iridium solution and ruthenium solution, stirring evenly, dropping alkaline reagent, controlling the pH to 4-6.5, drying at 80-150°C for 8-12 hours, and then calcining at 300-550°C for 1-3 hours; (2) dispersing the yttrium zirconium aluminum composite oxide containing precious metal active components obtained in step (1) in water, ball-milling to a particle size of 0.2-2 μm, adding cerium salt, iron salt, zirconium salt and tartaric acid, stirring and dissolving, and then heating to form a sol; (3) The sol is sprayed onto the surface of the carrier by a rotary spraying technique, aged for 0.5 hours, dried at 40-80°C for 8-12 hours, and calcined at 400-600°C for 2-4 hours to obtain a honeycomb carrier core-shell structure three-way catalyst.

5. The method for preparing a core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 4, characterized in that: In step (1), the alkaline reagent is one or more of ammonia water, ethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, monoethanolamine and triethanolamine.

6. The method for preparing a core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 4, characterized in that: In step (2), the cerium salt is one or more of cerium acetate, cerium carbonate, cerium sulfate, cerium ammonium nitrate, cerous carbonate dihydrate, cerous oxalate nonahydrate, cerous nitrate hexahydrate and cerous nitrate; The iron salt is one or more of ferric chloride, ferric nitrate, ferric bromide, ferric perchlorate and ferric dihydrogen phosphate; The zirconium salt is one or more of zirconium carbonate, zirconium citrate, zirconium isooctanoate, zirconium propionate, zirconium methacrylate, zirconium oxychloride and zirconium oxynitrate.

7. The method for preparing a core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 4, characterized in that: In step (2), the weight ratio of the tartaric acid to the yttrium zirconium aluminum oxide containing the precious metal active component is (0.1-1):

1.

8. The method for preparing a core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 4, characterized in that: The method for preparing the platinum dispersion in step (1) comprises the following steps: adding a dispersant into deionized water to form a dispersant solution, and then mixing the platinum solution and the dispersant solution in a weight ratio of 1:1-1:5 and stirring the mixture to obtain a platinum dispersion.

9. The method for preparing a core-shell three-way catalyst for reducing automobile exhaust emissions according to claim 8, characterized in that: In step (1), the dispersant is one or more of acetic acid, citric acid, succinic acid, lactic acid, cellulose acetate, ethyl cellulose, cellulose nitrate, cellulose acetate butyrate, hydroxypropyl cellulose, hydroxyethyl cellulose, cellulose acetate phthalate, glucose, fructose, sucrose, maltose, mannose, rhamnose, sorbitol and trehalose; The weight ratio of the dispersant to deionized water in the dispersant solution is 1:3-3:2.