A single - coated catalyst for reducing tail gas emissions and its preparation method

Abstract

The present invention provides a single - coated catalyst for reducing tail gas emissions, which comprises a carrier and a coating coated on the carrier. The coating includes an inlet section and an outlet section. Both the inlet section and the outlet section include noble metals Pd and Rh. The noble metal Pd is supported on cobalt - modified La2O3 - Al2O3, and Rh is supported on nickel - modified cerium - zirconium solid solution. In the inlet section, the mass ratio of La2O3 - Al2O3 to cerium - zirconium solid solution is 1:1 to 4:1, and the mass ratio of noble metals Pd and Rh is 50:1 to 3:1. In the outlet section, the mass ratio of La2O3 - Al2O3 to cerium - zirconium solid solution is 1:1 to 1:5, and the mass ratio of Pd and Rh is 10:1 to 1:2. The present invention changes the surface properties by coordinating cobalt and nickel with different additives to uniformly load the materials, promotes the highly - dispersed formation of noble metals on the surface of the modified materials, forms a synergistic effect among the noble - metal - transition - metal - oxide - carrier materials to improve the catalyst performance; at the same time, optimizes the distribution ratio of Pd and Rh in the inlet section and the outlet section to improve the tail - gas treatment ability of the single - coated catalyst and enhance the purification performance of the exhaust gas emitted by the internal combustion engine.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a single - coated catalyst for reducing tail gas emissions and a preparation method thereof. Background Art

[0002] The three - way catalyst for gasoline vehicles refers to a vehicle catalyst that converts carbon monoxide (CO), hydrocarbons (tail gas), and nitrogen oxides (NOx) in the original automobile exhaust into harmless carbon dioxide (CO2), water (H2O), and nitrogen (N2) through catalytic reactions. With the development of society, the global vehicle ownership has been increasing continuously, and the pollutants in automobile exhaust have become one of the main sources of urban air pollution, which not only endangers human health but also causes great damage to the ecological environment. Many studies have shown that various pollutants in automobile exhaust emissions are very harmful to the human body. Some of the organic components, such as polycyclic aromatic hydrocarbons like benzene, are carcinogens and have a long - term accumulation effect in the human body. In addition, hydrocarbons and nitrogen oxides will further undergo photochemical reactions under strong light irradiation to form toxic photochemical smog, and unburned hydrocarbons will also directly stimulate the human visual and olfactory organs, causing functional decline.

[0003] Currently, various countries are formulating increasingly strict automobile exhaust emission regulations to limit the emissions of gaseous pollutants. In the current industry, when using a single - coated scheme for automotive three - way catalysts, the performance is usually poor and it is difficult to achieve an ideal purification effect. The present invention enhances the catalytic purification ability of tail gas by modifying and optimizing the key components of the catalyst and adjusting the component ratio. Summary of the Invention

[0004] The purpose of the present invention is to overcome and supplement the deficiencies existing in the prior art, and provide a single - coated catalyst for reducing tail gas emissions and a preparation method thereof. By coordinating different additives with cobalt and nickel to uniformly load materials, the surface properties are changed, promoting the highly dispersed formation of noble metals on the surface of the modified materials, forming a synergistic effect among noble metal - metal oxide - support materials to improve the catalyst performance. At the same time, by optimizing the distribution ratio of Pd and Rh in the intake section and the outlet section, the treatment ability of the single - coated layer for tail gas is improved, and the purification performance of the exhaust gas emitted by internal combustion engines is enhanced.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A single - coated catalyst for reducing tail gas emissions, wherein: the catalyst includes a support and a coating coated on the support. The coating includes an intake section and an outlet section. Both the intake section and the outlet section include noble metals Pd and Rh. The noble metal Pd is loaded on La2O3 - Al2O3 modified by cobalt, and Rh is loaded on a cerium - zirconium solid solution modified by nickel.

[0007] Preferably, for the single - coated catalyst for reducing tail gas emissions, wherein: in the intake section, the mass ratio of La2O3 - Al2O3 to cerium - zirconium solid solution is 1:1 to 4:1, and the mass ratio of noble metals Pd and Rh is 50:1 to 3:1; in the exhaust section, the mass ratio of La2O3 - Al2O3 to cerium - zirconium solid solution is 1:1 to 1:5, and the mass ratio of Pd and Rh is 10:1 to 1:2.

[0008] Preferably, for the single - coated catalyst for reducing tail gas emissions, wherein: the cerium - zirconium solid solution I in the intake section comprises 50 wt% - 89 wt% ZrO2, 10 wt% - 40 wt% CeO2, and 1 wt% - 10 wt% metal oxides, and the metal oxides are selected from one or more of La2O3, Y2O3, Pr6O 11 , Nd2O3.

[0009] Preferably, for the single - coated catalyst for reducing tail gas emissions, wherein: the cerium - zirconium solid solution II in the exhaust section comprises 10 wt% - 59 wt% ZrO2, 40 wt% - 80 wt% CeO2, and 1 wt% - 10 wt% metal oxides, and the metal oxides are selected from one or more of La2O3, Y2O3, Pr6O 11 , Nd2O3.

[0010] Preferably, for the single - coated catalyst for reducing tail gas emissions, wherein: the coating amount in the intake section is 50 - 150 g / L, and the coating amount in the exhaust section is 80 - 160 g / L.

[0011] Preferably, for the single - coated catalyst for reducing tail gas emissions, wherein: the cobalt content in the cobalt - modified La2O3 - Al2O3 is 0.1 - 5 g / L, and the nickel content in the nickel - modified cerium - zirconium solid solution is 0.1 - 5 g / L.

[0012] A preparation method of a single - coated catalyst for reducing tail gas emissions, which includes the following steps:

[0013] (1) Coating of the intake section: Dissolve cobalt salt and disodium EDTA in water, add La2O3 - Al2O 3,After stirring and mixing evenly, dry it, and calcine it at 300-400 °C for 2-4 h to obtain cobalt-modified La2O3-Al2O3; add the above powder into water, slowly drop Pd solution, stir evenly, add ethylenediamine, adjust the pH to 6-7, continue to stir and then dry it, and calcine it at 400-550 °C for 2-4 h to obtain Pd supported on cobalt-modified La2O3-Al2O3; dissolve nickel salt and citric acid in water, add cerium-zirconium solid solution I, stir and mix evenly and then dry it, and calcine it at 300-400 °C for 2-4 h to obtain nickel-modified cerium-zirconium solid solution I; add nickel-modified cerium-zirconium solid solution I into water, slowly drop Rh solution, stir evenly, add ethylenediamine, adjust the pH to 5-6, continue to stir and then dry it, and calcine it at 400-550 °C for 2-4 h to obtain Rh supported on nickel-modified cerium-zirconium solid solution I; add Pd supported on cobalt-modified La2O3-Al2O3 and Rh supported on nickel-modified cerium-zirconium solid solution I into water and stir for 30-60 min, then coat the intake section from the carrier intake end with a coating amount of 50-150 g / L, and dry it to obtain a semi-finished product;

[0014] (2) Coating of the outlet section: Dissolve cobalt salt and disodium EDTA in water, add La2O3-Al2O 3, After stirring and mixing evenly, dry it, and calcine it at 300-400 °C for 2-4 h to obtain cobalt-modified La2O3-Al2O3. Add the above powder into water, slowly drop Pd solution, stir evenly, add ethylenediamine, adjust the pH to 6-7, continue to stir and then dry it, and calcine it at 400-550 °C for 2-4 h to obtain Pd supported on cobalt-modified La2O3-Al2O3; dissolve nickel salt and citric acid in water, add cerium-zirconium solid solution II, stir and mix evenly and then dry it, and calcine it at 300-400 °C for 2-4 h to obtain nickel-modified cerium-zirconium solid solution II; add nickel-modified cerium-zirconium solid solution II into water, slowly drop Rh solution, stir evenly, add ethylenediamine, adjust the pH to 5-6, continue to stir and then dry it, and calcine it at 400-550 °C for 2-4 h to obtain Rh supported on nickel-modified cerium-zirconium solid solution II; add Pd supported on cobalt-modified La2O3-Al2O3 and Rh supported on nickel-modified cerium-zirconium solid solution II into water and stir for 30-60 min, coat the remaining length of the carrier from the outlet end of the semi-finished product with a coating amount of 80-160 g / L, dry it, and then heat the dried semi-finished product at a heating rate of 0.5-25 °C / min to 450-800 °C and calcine for 1-8 h to obtain the finished catalyst.

[0015] Preferably, in the preparation method of the single-coated catalyst for reducing tail gas emissions, among them: the cobalt salt is selected from one or two of cobalt nitrate, cobalt sulfate, and cobalt acetate; the nickel salt is selected from one or two of nickel nitrate, nickel sulfate, and nickel acetate.

[0016] Preferably, in the method for preparing the single-coated catalyst for reducing tail gas emissions, the mass ratio of cobalt salt to disodium EDTA is 1:1 to 1:1.5; the mass ratio of nickel salt to citric acid is 1:1 to 1:1.5.

[0017] Advantages of the present invention:

[0018] For the single-coated catalyst for reducing tail gas emissions and its preparation method of the present invention, by using different additives to coordinate cobalt and nickel on alumina and cerium-zirconium powder materials respectively in a highly uniform manner, the surface properties of the materials are changed. The specific crystal planes exposed after calcination can accelerate the reaction. Also, the additives promote the highly uniform dispersion of noble metals on the surface of the modified materials, forming a synergistic effect among the noble metal-metal oxide-support materials. This is more conducive to the rapid ignition and improved conversion rate of the catalyst with the same noble metal content, thereby improving the catalyst performance. At the same time, by optimizing the different distribution ratios of noble metals, alumina, and cerium-zirconium powder in the front and rear zones, the tail gas treatment capacity of the single coating is improved, and the purification performance of the exhaust gas from internal combustion engines is enhanced. Specific embodiments

[0019] The present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1

[0021] A method for preparing a single-coated catalyst for reducing tail gas emissions includes the following steps:

[0022] (1) Coating of the air inlet section: 63g of cobalt nitrate and 63g of disodium EDTA were dissolved in water, 500g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3; the above powder was added to water, and a palladium nitrate solution containing 8.83g of Pd was slowly dripped into the solution, the mixture was stirred and ethylenediamine was added, the pH was adjusted to 6.5, the mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3; 63g of nickel nitrate and 63g of citric acid were dissolved in water, 500g of cerium-zirconium solid solution (containing 20wt% CeO2, 5wt% Y2O3, 75wt% ZrO2), stirred and mixed, then dried, and calcined at 300°C for 2h to obtain a nickel-modified cerium-zirconium solid solution. The nickel-modified cerium-zirconium solid solution was added to water, and a rhodium nitrate solution containing 0.88g of Rh was slowly added dropwise. After stirring, ethylenediamine was added, and the pH was adjusted to 5. After continued stirring, the solution was dried and calcined at 400°C for 2h to obtain a Rh-loaded nickel-modified cerium-zirconium solid solution. 500g of Pd loaded on cobalt-modified La2O3-Al2O3 and 500g of Rh loaded on nickel-modified cerium-zirconium solid solution were added to water and stirred for 60min. Then, a coating amount of 100g / L was applied to half the length of the carrier from the air inlet end, and the product was dried to obtain a semi-finished product.

[0023] (2) Coating of the gas outlet section: 32g of cobalt nitrate and 32g of disodium EDTA were dissolved in water, 250g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3. The above powder was added to water, and a palladium nitrate solution containing 4.42g of Pd was slowly dripped into it. After stirring, ethylenediamine was added, and the pH was adjusted to 6.5. After continued stirring, the mixture was dried and calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3. 63g of nickel nitrate and 63g of citric acid were dissolved in water, 1000g of cerium-zirconium solid solution (containing 50wt% CeO2, 5wt% Y2O3, 45wt% ZrO2), stirred and dried, and calcined at 300℃ for 2h to obtain nickel-modified cerium-zirconium solid solution II; nickel-modified cerium-zirconium solid solution II was added to water, and a rhodium nitrate solution containing 2.65g of Rh was slowly dripped into it, stirred evenly, and ethylenediamine was added, and the pH was adjusted to 5. After continued stirring, it was dried and calcined at 400℃ for 2h to obtain Rh-loaded nickel-modified cerium-zirconium solid solution II; 250g Pd loaded on cobalt-modified La2O3-Al2O3 and 1000g Rh loaded on nickel-modified cerium-zirconium solid solution II were added to water and stirred for 60min, and then coated from the gas outlet end to the catalyst semi-finished product obtained in step (1) at a coating amount of 100 g / L, coated the remaining length, dried, and calcined at 500℃ for 1h to obtain the finished catalyst.

[0024] Example 2

[0025] A method for preparing a single-coated catalyst for reducing tail gas emissions comprises the following steps:

[0026] (1) Coating of the air inlet section: 31g of cobalt acetate and 31g of disodium EDTA were dissolved in water, 400g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3; the above powder was added to water, and a palladium nitrate solution containing 8.83g of Pd was slowly dripped into the solution, the mixture was stirred and ethylenediamine was added, the pH was adjusted to 6.5, the mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3; 12g of nickel acetate and 12g of citric acid were dissolved in water, 100g of cerium-zirconium solid solution (containing 10wt% CeO2, 5wt% La2O3, 85wt% ZrO2), stirred and dried, and calcined at 300°C for 2h to obtain a nickel-modified cerium-zirconium solid solution. The nickel-modified cerium-zirconium solid solution was added to water, and a rhodium nitrate solution containing 0.44g of Rh was slowly added dropwise. After stirring, ethylenediamine was added, and the pH was adjusted to 6. After continued stirring, the solution was dried and calcined at 400°C for 2h to obtain a Rh-loaded nickel-modified cerium-zirconium solid solution. 400g of Pd loaded on cobalt-modified La2O3-Al2O3 and 100g of Rh loaded on nickel-modified cerium-zirconium solid solution were added to water and stirred for 60min. Then, a coating amount of 100g / L was applied to half the length of the carrier from the air inlet end, and the product was dried to obtain a semi-finished product.

[0027] (2)Coating of the gas outlet section: Dissolve 32 g of cobalt acetate and 32 g of disodium EDTA in water, add 100 g of La2O3-Al2O3 (containing 3 wt% La2O3), stir and mix evenly, then dry and calcine at 300 °C for 2 h to obtain cobalt-modified La2O3-Al2O3; add the above powder into water, slowly drop the palladium nitrate solution containing 4.42 g of Pd element, stir evenly, add ethylenediamine, adjust the pH to 6.5, continue to stir and then dry, and calcine at 400 °C for 2 h to obtain Pd supported on cobalt-modified La2O3-Al2O3; dissolve 24 g of nickel acetate and 24 g of citric acid in water, add 500 g of cerium-zirconium solid solution II (containing 60 wt% CeO2, 5 wt% Y2O3, 35 wt% ZrO2), stir and mix evenly, then dry and calcine at 300 °C for 2 h to obtain nickel-modified cerium-zirconium solid solution II; add the nickel-modified cerium-zirconium solid solution II into water, slowly drop the rhodium nitrate solution containing 1.33 g of Rh element, stir evenly, add ethylenediamine, adjust the pH to 5, continue to stir and then dry, and calcine at 400 °C for 2 h to obtain Rh supported on nickel-modified cerium-zirconium solid solution II; add 100 g of Pd supported on cobalt-modified La2O3-Al2O3 and 500 g of Rh supported on nickel-modified cerium-zirconium solid solution II into water and stir for 60 min, then coat from the gas outlet end to the semi-finished product prepared in step (1) at a coating amount of 100 g / L, coat the remaining length, dry, and calcine at 450 °C for 1 h to obtain the finished catalyst.

[0028] Example 3

[0029] A preparation method of a single-coated catalyst for reducing tail gas emissions, comprising the following steps:

[0030] (1) Coating of the air inlet section: 32g of cobalt sulfate and 32g of disodium EDTA were dissolved in water, 400g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3; the above powder was added to water, and a palladium nitrate solution containing 4.42g of Pd was slowly dripped into it, the mixture was stirred and ethylenediamine was added, the pH was adjusted to 6.5, the mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3; 31g of nickel sulfate and 31g of citric acid were dissolved in water, 200g of cerium-zirconium solid solution (containing 30wt% CeO2, 5wt% Y2O3, 65wt% ZrO2) was added, The mixture was stirred and dried, and then calcined at 300° C. to obtain a nickel-modified cerium-zirconium solid solution. The nickel-modified cerium-zirconium solid solution was added to water, and a rhodium nitrate solution containing 0.88 g of Rh was slowly added dropwise. After stirring, ethylenediamine was added, and the pH was adjusted to 5. The mixture was further stirred and dried. The mixture was calcined at 400° C. for 2 h to obtain a Rh-loaded nickel-modified cerium-zirconium solid solution. 400 g of Pd loaded on cobalt-modified La2O3-Al2O3 and 200 g of Rh loaded on nickel-modified cerium-zirconium solid solution were added to water and stirred for 60 min. The mixture was then coated on half the length of the carrier from the air inlet end at a coating amount of 100 g / L, and dried to obtain a semi-finished product.

[0031] (2) Coating of the gas outlet section: 32g of cobalt sulfate and 32g of disodium EDTA were dissolved in water, 200g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3; the above powder was added to water, and a palladium nitrate solution containing 2.21g of Pd was slowly dripped into the solution, the mixture was stirred and ethylenediamine was added, the pH was adjusted to 6.5, the mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3; 32g of nickel sulfate and 32g of citric acid were dissolved in water, 400g of cerium-zirconium solid solution (containing 60wt% CeO2, 5wt% Y2O3, 35wt% ZrO2), stirred and dried, and calcined at 300℃ for 2h to obtain nickel-modified cerium-zirconium solid solution II; nickel-modified cerium-zirconium solid solution II was added to water, and a rhodium nitrate solution containing 0.61g of Rh was slowly dripped into it, stirred evenly, and ethylenediamine was added, and the pH was adjusted to 5. After continued stirring, it was dried and calcined at 400℃ for 2h to obtain Rh-loaded nickel-modified cerium-zirconium solid solution II; 200g Pd loaded on cobalt-modified La2O3-Al2O3 and 400g Rh loaded on nickel-modified cerium-zirconium solid solution II were added to water and stirred for 60min, and then coated from the gas outlet end to the catalyst semi-finished product obtained in step (1) at a coating amount of 150 g / L, coated the remaining length, dried, and calcined at 500℃ for 1h to obtain the finished catalyst.

[0032] Comparative Example 1

[0033] A method for preparing a single-coated catalyst for reducing tail gas emissions comprises the following steps:

[0034] (1) Coating of the air inlet section: 63g of cobalt nitrate and 63g of disodium EDTA were dissolved in water, 500g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3. The above powder was added into water, and a palladium nitrate solution containing 8.83g of Pd was slowly dripped into the solution, stirred and ethylenediamine was added, and the pH was adjusted to 6.5. The mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3. Cerium-zirconium solid solution (containing 20wt% CeO2, 5wt% A cerium-zirconium solid solution (containing 20 wt% CeO2, 5 wt% Y2O3, and 75 wt% ZrO2) was added to water, and a rhodium nitrate solution containing 0.88 g of Rh was slowly dripped into it. After stirring evenly, ethylenediamine was added, and the pH was adjusted to 5. After continued stirring, the solution was dried and calcined at 400°C for 2 h to obtain a Rh-loaded cerium-zirconium solid solution. 500 g of Pd was loaded on cobalt-modified La2O3-Al2O3 and 500 g of Rh-loaded cerium-zirconium solid solution (containing 20 wt% CeO2, 5 wt% Y2O3, and 75 wt% ZrO2) was added to water and stirred for 60 min. The solution was then coated on the air inlet section from one end of the carrier at a coating amount of 100 g / L and dried to obtain a semi-finished product.

[0035] (2) Coating of the gas outlet section: 32g of cobalt nitrate and 32g of disodium EDTA were dissolved in water, 250g of La2O3-Al2O3 (containing 3wt% La2O3) was added, the mixture was stirred and dried, and the mixture was calcined at 300℃ for 2h to obtain cobalt-modified La2O3-Al2O3; the above powder was added to water, and a palladium nitrate solution containing 4.42g of Pd was slowly dripped into it, and ethylenediamine was added after stirring, and the pH was adjusted to 6.5. The mixture was continued to be stirred and dried, and the mixture was calcined at 400℃ for 2h to obtain Pd loaded on cobalt-modified La2O3-Al2O3; cerium-zirconium solid solution II (containing 50wt% CeO2, 5wt% Y2O3, 45wt% ZrO2) was added to water, and a solution containing 2.65g of Pd was slowly dripped into it. A rhodium nitrate solution of Rh element was stirred evenly, and then ethylenediamine was added, and the pH was adjusted to 5. After continued stirring, the solution was dried and calcined at 400°C for 2h to obtain Rh-loaded cerium-zirconium solid solution II. 250g of Pd loaded on cobalt-modified La2O3-Al2O3 and 1000g of Rh-loaded cerium-zirconium solid solution II were added to water and stirred for 60min. Then, a coating amount of 100 g / L was applied from the gas outlet to the semi-finished product obtained in step (1), and the remaining length was coated. The catalyst was calcined at 500°C for 1h to obtain the finished catalyst.

[0036] Comparative Example 2

[0037] A method for preparing a single-coated catalyst for reducing tail gas emissions comprises the following steps:

[0038] (1) Coating of the air inlet section: 400g La2O3-Al2O3 (containing 3wt% La2O3) was added to water, and a palladium nitrate solution containing 8.83g Pd was slowly added dropwise. After stirring evenly, ethylenediamine was added and the pH was adjusted to 6.5. After continued stirring, the mixture was dried and calcined at 400℃ for 2h to obtain Pd-loaded cobalt-modified La2O3-Al2O3. 12g nickel acetate and 12g citric acid were added to water and dissolved, and 100g cerium-zirconium solid solution (containing 10wt% CeO2, 5wt% La2O3, 85wt% ZrO2), stirred and mixed, then dried, and calcined at 300°C for 2h to obtain a nickel-modified cerium-zirconium solid solution. The nickel-modified cerium-zirconium solid solution was added to water, and a rhodium nitrate solution containing 0.44g of Rh was slowly added dropwise. After stirring, ethylenediamine was added, and the pH was adjusted to 6. After continued stirring, the solution was dried and calcined at 400°C for 2h to obtain a Rh-loaded nickel-modified cerium-zirconium solid solution. 400g of Pd-loaded La2O3-Al2O3 and 100g of Rh-loaded nickel-modified cerium-zirconium solid solution were added to water and stirred for 60min. Then, a coating amount of 100g / L was applied to half the length of the carrier from the air inlet end, and the product was dried to obtain a semi-finished product.

[0039] (2) Coating of the gas outlet section: add 100g La2O3-Al2O3 (containing 3wt% La2O3) into water, slowly drop into palladium nitrate solution containing 4.42g Pd, stir evenly, add ethylenediamine, adjust pH to 6.5, continue stirring, dry, and calcine at 400℃ for 2h to obtain Pd-loaded La2O3-Al2O3; add 24g nickel acetate and 24g citric acid into water and dissolve, add 500g cerium-zirconium solid solution II (containing 60wt% CeO2, 5wt% Y2O3, 35wt% ZrO2), stir evenly, dry, and calcine at 300℃ for 2h to obtain nickel-modified cerium-zirconium solid solution II; add nickel-modified cerium-zirconium solid solution II into water, slowly drop into 1.33g A solution of Rh in rhodium nitrate was stirred evenly, and then ethylenediamine was added to adjust the pH to 5. After continued stirring, the solution was dried and calcined at 400°C for 2h to obtain Rh-loaded nickel-modified cerium-zirconium solid solution II. 100g of Pd-loaded La2O3-Al2O3 and 500g of Rh-loaded nickel-modified cerium-zirconium solid solution II were added to water and stirred for 60min. Then, the mixture was coated from the gas outlet end to the semi-finished product obtained in step (1) at a coating amount of 100 g / L, and the remaining length was coated. The catalyst was dried and calcined at 450°C for 1h to obtain the finished catalyst.

[0040] A method for testing a single-coat catalyst for reducing tail gas emissions comprises the following steps:

[0041] The catalyst samples obtained in Examples 1 to 3 and Comparative Examples 1-2 were aged under the same conditions for 20 h in a high-temperature tube furnace at 1050 °C, and then encapsulated into purifiers. The whole vehicle emission test was carried out according to the WLTC Ι type test. The engine displacement of the test vehicle was 1.6 L, and the emission test results are shown in Table 1.

[0042] Table 1 Comparison of catalytic performance of catalysts obtained in Examples 1-3 and Comparative Examples 1-2

[0043]

[0044] Note: THC in Table 1 is the abbreviation for the total amount of hydrocarbons contained in the gas.

[0045] As shown in Table 1, the results of the catalyst performance evaluation show that compared with Comparative Examples 1-2, the three-way catalysts prepared in Examples 1-3 of the present invention have excellent tail gas purification ability under various transient conditions, and show good catalytic performance for the main pollutants.

[0046] The single-coated catalyst for reducing tail gas emissions and its preparation method of the present invention. By coordinating different additives with cobalt and nickel, the uniform loading material changes the surface properties, promotes the highly dispersed formation of noble metals on the surface of the modified material, and forms a synergistic effect among the noble metal-metal oxide-support materials to improve the catalyst performance; at the same time, the distribution ratio of Pd and Rh in the intake section and the outlet section is optimized to improve the tail gas treatment ability of the single coating and enhance the purification performance of the exhaust gas from internal combustion engines.

[0047] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A single-coated catalyst for reducing tail gas emissions, characterized in that: The catalyst comprises a carrier and a coating coated on the carrier. The coating includes an intake section and an outlet section. Both the intake section and the outlet section include noble metals Pd and Rh. The noble metal Pd is loaded on cobalt-modified La2O3-Al2O3, and Rh is loaded on nickel-modified cerium-zirconium solid solution. In the intake section, the mass ratio of La2O3-Al2O3 to cerium-zirconium solid solution is 1:1 to 4:1, and the mass ratio of noble metals Pd and Rh is 50:1 to 3:

1. In the outlet section, the mass ratio of La2O3-Al2O3 to cerium-zirconium solid solution II is 1:1 to 1:5, and the mass ratio of Pd and Rh is 10:1 to 1:

2.

2. The single-coated catalyst for reducing tail gas emissions according to claim 1, characterized in that: The cerium-zirconium solid solution I in the intake section comprises 50 wt% - 89 wt% ZrO2, 10 wt% - 40 wt% CeO2, and 1 wt% - 10 wt% metal oxide, and the metal oxide is selected from one or more of La2O3, Y2O3, Pr6O 11 , Nd2O3.

3. The single-coated catalyst for reducing tail gas emissions according to claim 1, characterized in that: The cerium-zirconium solid solution II in the gas outlet section comprises 10 wt% to 59 wt% ZrO2, 40 wt% to 80 wt% CeO2, and 1 wt% to 10 wt% metal oxide, and the metal oxide is selected from one or more of La2O3, Y2O3, Pr6O 11 , Nd2O3.

4. The single-coated catalyst for reducing tail gas emissions according to claim 1, characterized in that: The coating amount of the intake section is 50 to 150 g / L, and the coating amount of the outlet section is 80 to 160 g / L.

5. The single-coated catalyst for reducing tail gas emissions according to claim 1, wherein: The cobalt content in the cobalt-modified La2O3-Al2O3 is 0.1 to 5 g / L, and the nickel content in the nickel-modified cerium-zirconium solid solution is 0.1 to 5 g / L.

6. The preparation method of the single - coated catalyst for reducing tail gas emissions according to any one of claims 1 - 5, characterized in that: It includes the following steps: (1) Coating of the intake section: Dissolve cobalt salt and disodium EDTA in water, add La2O3 - Al2O 3, Stir and mix evenly, then dry and calcine at 300 - 400 °C to obtain cobalt - modified La2O3 - Al2O3. Add the above powder into water, slowly drop Pd solution, stir evenly, add ethylenediamine, adjust the pH to 6 - 7, continue stirring and then dry. Calcine at 400 - 550 °C to obtain Pd supported on cobalt - modified La2O3 - Al2O3; Dissolve nickel salt and citric acid in water, add cerium - zirconium solid solution I, stir and mix evenly, then dry and calcine at 300 - 400 °C for 2 - 4 h to obtain nickel - modified cerium - zirconium solid solution I; Add nickel - modified cerium - zirconium solid solution I into water, slowly drop Rh solution, stir evenly, add ethylenediamine, adjust the pH to 5 - 6, continue stirring and then dry. Calcine at 400 - 550 °C for 2 - 4 h to obtain Rh supported on nickel - modified cerium - zirconium solid solution I; Add Pd supported on cobalt - modified La2O3 - Al2O3 and Rh supported on nickel - modified cerium - zirconium solid solution I into water and stir for 30 - 60 min, then coat the intake section from the intake end of the carrier at a coating amount of 50 - 150 g / L, and dry to obtain a semi - finished product; (2) Coating of the gas outlet section: Dissolve cobalt salt and disodium EDTA in water, add La2O3 - Al2O 3, Stir and mix evenly, then dry, and calcine at 300 - 400 °C for 2 - 4 h to obtain cobalt - modified La2O3 - Al2O3. Add the above powder into water, slowly drop Pd solution, stir evenly, add ethylenediamine, adjust the pH to 6 - 7, continue stirring and then dry, and calcine at 400 - 550 °C for 2 - 4 h to obtain Pd supported on cobalt - modified La2O3 - Al2O3; Dissolve nickel salt and citric acid in water, add cerium - zirconium solid solution II, stir and mix evenly, then dry, and calcine at 300 - 400 °C for 2 - 4 h to obtain nickel - modified cerium - zirconium solid solution II; Add nickel - modified cerium - zirconium solid solution II into water, slowly drop Rh solution, stir evenly, add ethylenediamine, adjust the pH to 5 - 6, continue stirring and then dry, and calcine at 400 - 550 °C for 2 - 4 h to obtain Rh supported on nickel - modified cerium - zirconium solid solution II; Add Pd supported on cobalt - modified La2O3 - Al2O3 and Rh supported on nickel - modified cerium - zirconium solid solution II into water and stir for 30 - 60 min. Coat the remaining length of the carrier from the gas outlet end of the semi - finished product with the slurry at a coating amount of 80 - 160 g / L, dry, and then heat the dried semi - finished product at a heating rate of 0.5 - 25 °C / min by programmed heating to 450 - 800 °C and calcine for 1 - 8 h to obtain the finished catalyst.

7. The preparation method of the single - coated catalyst for reducing tail gas emissions according to claim 6, characterized in that: The cobalt salt is selected from one or two of cobalt nitrate, cobalt sulfate, and cobalt acetate; the nickel salt is selected from one or two of nickel nitrate, nickel sulfate, and nickel acetate.

8. The preparation method of the single-coated catalyst for reducing tail gas emissions according to claim 6, characterized in that: The mass ratio of the cobalt salt to disodium EDTA is 1:1 to 1:1.5; the mass ratio of the nickel salt to citric acid is 1:1 to 1:1.5.

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