A platinum palladium cerium zirconium aluminum catalyst with yttrium oxide loaded on the surface, and its preparation method and application

Abstract

The invention discloses a platinum palladium cerium zirconium aluminum catalyst with yttrium oxide loaded on the surface and a preparation method thereof, comprising platinum palladium cerium zirconium aluminum particles and yttrium oxide loaded on the outside of the platinum palladium cerium zirconium aluminum particles. The invention has the beneficial effects of wrapping a layer of yttrium oxide on the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles to form a hydrothermal protective layer structure, which is conducive to preventing water from entering the interior at high temperature and affecting the stability of the platinum palladium cerium zirconium aluminum, so that the material has high resistance to high hydrothermal aging, avoids contact between water and precious metals in gaseous pollution, stabilizes the state of precious metal platinum palladium, improves the active sites of precious metals in the catalyst material, ensures the high activity and high hydrothermal aging resistance of the catalyst, improves the durability of the catalyst, and has better purification of carbon monoxide (CO) and nitrogen oxides (NO x ), hydrocarbon (HC) purification capabilities, especially the ability to purify methane (CH4).

Description

Technical Field

[0001] The invention relates to the field of natural gas fuel engine tail gas purification, in particular to a platinum palladium cerium zirconium aluminum catalyst with yttrium oxide loaded on its surface. Background Art

[0002] In the exhaust gas emitted by internal combustion engines (engines) using gasoline and diesel as fuel, in addition to hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NO x In addition to harmful gases such as carbon monoxide (CO₂), exhaust gases also produce large amounts of fine particulate matter, which pose a significant threat to humans and the environment. Global regulations governing these harmful gases and particulate matter emissions are tightening year by year, along with carbon emissions controls. Consequently, engineers in the internal combustion engine industry are developing new technologies to reduce engine pollutant emissions. Natural gas, due to its high fuel efficiency and low CO₂ emissions per unit mass, has recently attracted attention for vehicles and ships using internal combustion engines fueled by natural gas (such as CNG vehicles and methane-fueled ships). However, methane (CH₄) accounts for 90% to 95% of the hydrocarbons (HC) by volume in the exhaust of natural gas-fueled internal combustion engines. The thermal conductivity of methane (CH₄) is 25 times that of carbon dioxide (CO₂), so methane treatment is necessary to reduce its environmental impact.

[0003] The average bond dissociation energy in a methane molecule (CH4) is 415.3 kJ / mol, and that in a gasoline molecule (C4~C 12 ) requires more than 20% more energy to crack the C-C bond (bond energy 345.6 kJ / mol) in natural gas. Secondly, CH4 is the most difficult hydrocarbon to oxidize, with a higher ignition temperature than other alkanes and unsaturated hydrocarbons. The ignition temperature of natural gas is 537°C, while that of gasoline is only 390-420°C. Therefore, oxidation reactions are more difficult to occur. Thirdly, the coupling reaction of CH4 and NO is also much more difficult than the coupling reaction of HC and NO, making the conversion of NO more difficult. Therefore, the performance of purification catalysts used for natural gas engine exhaust treatment must be significantly higher than that of gasoline engine exhaust purification catalysts to meet the requirements of the National VI emission standards. At the same time, the water content in the exhaust of internal combustion engines fueled by natural gas is as high as 20%. This water in the exhaust will adsorb on the catalyst surface, causing its oxidation ability for CH4 to drop sharply.

[0004] With the implementation of my country's "Emission Limits and Measurement Methods for Exhaust Pollutants from Marine Engines (China Phase I and II)" and "Emission Limits and Measurement Methods for Pollutants from Heavy-Duty Diesel Vehicles (China Phase VI)," stricter limits for CH4 in exhaust from natural gas-fueled engines are being implemented. This places higher demands on catalysts for low-temperature activity, water resistance, and durability. Currently, precious metals platinum and palladium, due to their excellent methane oxidation properties, are widely used in exhaust purification catalysts for natural gas-fueled internal combustion engines. However, palladium-based precious metal catalysts face the significant challenge of water poisoning in practical applications. Furthermore, palladium-based precious metals are expensive, and research has shown that introducing platinum into palladium-based catalysts can actually inhibit the activity of palladium, compromising the catalyst's performance.

[0005] CN114950422A discloses a catalyst, its preparation method, and application. The catalyst comprises an Al2O3 carrier, a catalytically active component, and a catalytic promoter. The catalytically active component comprises Pt-doped PdO nanocrystals, and the catalytic promoter comprises any one or a combination of at least two of La, Pr, Y, or Nd. The catalyst addresses the issues of insufficient activity, long-term stability, and poor hydrothermal stability of typical PdO / Al2O3 catalysts. However, the catalyst described in this patent was only tested for stability at 450°C for 100 hours in the presence of water. CN103191733B discloses a low-concentration methane combustion catalyst and its preparation method. At approximately 550°C in the presence of water, the methane conversion rate is 90%, indicating that the catalyst has very low methane activity in the presence of water. CN113145163A discloses a palladium-supported all-silicon molecular sieve catalyst and its preparation method. The catalyst uses an all-silicon ZSM 5 molecular sieve as a carrier, uniformly loaded with nanoparticles of palladium oxide as the active component. The active component accounts for 1% of the catalyst by mass. However, the catalyst prepared in this patent was only tested for methane conversion efficiency under anhydrous conditions. CN114258322A discloses a sulfur-resistant, highly active catalyst for removing methane from a gas stream with a certain methane concentration by oxidizing it, but does not describe the catalyst's hydrothermal stability. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a platinum palladium cerium zirconium aluminum catalyst with yttrium oxide loaded on the surface, as well as a preparation method and application thereof.

[0007] The purpose of the present invention is achieved through the following technical solutions: a catalyst comprising platinum palladium cerium zirconium aluminum particles and yttrium oxide supported on the outside of the platinum palladium cerium zirconium aluminum particles; in this embodiment, a hydrothermal protective layer is wrapped around the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles to form a hydrothermal protective layer structure, thereby preparing a platinum palladium cerium zirconium aluminum catalyst material with a surface-loaded protective layer, which is beneficial for preventing water from entering the interior at high temperature and affecting the stability of the platinum palladium cerium zirconium aluminum, so that the material has high resistance to high hydrothermal aging, avoids direct contact between water and precious metals in gaseous pollution, stabilizes the state of precious metal platinum palladium, improves the active sites of precious metals in the catalyst material, ensures the high activity and resistance to high hydrothermal aging of the catalyst, improves the durability of the catalyst, and has better purification of carbon monoxide (CO) and nitrogen oxides (NO x ), hydrocarbon (HC) purification capacity, especially the ability to purify methane (CH4);

[0008] Furthermore, according to the weight ratio, it includes 5 to 10 parts of yttrium oxide and 90 to 95 parts of platinum palladium cerium zirconium aluminum particles; in this embodiment, the preferred hydrothermal protective layer is yttrium oxide, and the precursor of yttrium oxide is a soluble nitrate aqueous solution, and is loaded on the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles by impregnation. Since yttrium nitrate has good solubility, impregnation is conducive to uniform distribution on the outer surface of the platinum palladium cerium zirconium aluminum particles, which is beneficial to isolating high-pressure catalysts compared to other barrier materials. Water contacts the platinum, palladium, cerium, zirconium, and aluminum at room temperature without affecting the diffusion of methane; the catalyst comprises 5 to 10 parts of yttrium oxide and 90 to 95 parts of platinum, palladium, cerium, zirconium, and aluminum particles in parts by weight. If the weight of yttrium oxide is higher than 5 to 10 parts, the adsorption and diffusion of methane on the catalyst surface will be hindered; if the weight of yttrium oxide is lower than 5 to 10 parts, yttrium oxide cannot form an effective protective layer structure on the surface of the platinum, palladium, cerium, zirconium, and aluminum particles, and cannot effectively prevent water from entering and contacting the platinum, palladium, cerium, zirconium, and aluminum particles at high temperatures.

[0009] Furthermore, in the platinum-palladium-cerium-zirconium-aluminum particles, the weight percentage of platinum is 0.45% to 3.60%, and the weight percentage of palladium is 0.05% to 0.40%; and the weight percentage of platinum is greater than the weight percentage of palladium; in this embodiment, in the platinum-palladium-cerium-zirconium-aluminum particles, the weight percentage of platinum is 0.45% to 3.60%, and the weight percentage of palladium is 0.05% to 0.40%; the precious metals platinum and palladium have a good oxidation effect on methane, but through research, it is found that when the precious metals platinum and palladium are present at the same time, especially when the content of palladium is higher than the content of platinum, the catalytic activity of palladium is inhibited, and the content of palladium in the platinum-palladium-cerium-zirconium-aluminum of the present invention is lower than the content of platinum, that is, the cost of precious metal palladium can be reduced, and at the same time, platinum and palladium produce a synergistic effect to provide more reaction active sites;

[0010] Furthermore, the platinum palladium cerium zirconium aluminum particles also include cerium zirconium aluminum material; the cerium zirconium aluminum material includes aluminum oxide, lanthanum oxide, cerium oxide, and zirconium oxide; in this embodiment, aluminum oxide provides a higher specific surface area and supporting strength, and lanthanum oxide, cerium oxide, and zirconium oxide can stabilize platinum and palladium precious metals in the catalyst, which is beneficial to improving catalytic activity.

[0011] Furthermore, the cerium-zirconium-aluminum material includes 20 to 40 parts of γ-Al2O3, 5 to 15 parts of La2O3, 40 to 60 parts of CeO2 and 5 to 15 parts of ZrO2;

[0012] Furthermore, the catalyst is prepared by the following steps:

[0013] 1) impregnating the outer surface of the platinum-palladium-cerium-zirconium-aluminum particles with a layer of soluble yttrium nitrate aqueous solution by an equal volume impregnation method, and aging to obtain an intermediate sample;

[0014] 2) drying and then calcining the intermediate sample prepared in step 1);

[0015] In step 1), the aging time is 10 to 15 hours; in step 2), the drying temperature is 100 to 150° C. and the drying time is 10 to 15 hours; in step 2), the calcination temperature is 600 to 700° C. and the calcination time is 2 to 4 hours;

[0016] The yttrium nitrate aqueous solution is a Y(NO3)3 aqueous solution with a mass concentration of 10.68% to 22.55%; in this embodiment, the immersion method is conducive to the uniform coating of the yttrium nitrate aqueous solution on the surface of the platinum palladium cerium zirconium aluminum particles, which is conducive to the formation of a uniform protective layer, thereby preventing water from entering and contacting the platinum palladium cerium zirconium aluminum particles at high temperatures.

[0017] The platinum-palladium-cerium-zirconium-aluminum particles are prepared by impregnating platinum nitrate and palladium nitrate solutions onto a cerium-zirconium-aluminum material, followed by drying at 100-150°C. The catalytically active platinum and palladium are loaded onto the cerium-zirconium-aluminum material through impregnation, creating a synergistic effect between the platinum and palladium, providing more reactive sites.

[0018] The present invention has the following advantages:

[0019] 1. The present invention forms a hydrothermal protective layer structure by wrapping a hydrothermal protective layer on the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles, and utilizes the hydrophobicity of the thin layer of nanoparticle yttrium oxide to prevent water molecules from entering the platinum palladium cerium zirconium aluminum catalyst particles and combining with the precious metal at high temperature, thereby stabilizing the valence state of the precious metal platinum palladium, improving the active sites of the precious metal in the catalyst material, and ensuring the high activity and high hydrothermal aging resistance of the catalyst. At the same time, it also blocks water molecules from entering the tiny pores of cerium zirconium aluminum and forming a hydroxide intermediate state with aluminum, thus avoiding the desorption of water at high temperature, which causes the pores of cerium zirconium aluminum to collapse and bury the precious metal, thereby improving the durability of the catalyst and having better purification of carbon monoxide (CO) and nitrogen oxides (NO x ), hydrocarbon (HC) purification capacity, especially the ability to purify methane (CH4);

[0020] 2. The preferred hydrothermal protective layer of the present invention is yttrium oxide, and the precursor of yttrium oxide is a soluble nitrate aqueous solution, and is loaded on the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles by impregnation. Since yttrium nitrate has good solubility, impregnation facilitates its uniform distribution on the outer surface of the platinum palladium cerium zirconium aluminum particles. Compared with other barrier materials, it can help isolate water from contact with the platinum palladium cerium zirconium aluminum material at high temperatures, while not affecting the diffusion of gas into it.

[0021] 3. In the preferred platinum-palladium-cerium-zirconium-aluminum material of the present invention, the weight percentage of platinum is 0.45-3.60%, and the weight percentage of palladium is 0.05-0.40%; the precious metals platinum and palladium have good oxidation effects on methane, but studies have found that when the precious metals platinum and palladium exist at the same time, especially when the palladium content is higher than the platinum content, the catalytic activity of palladium is inhibited, and the palladium content in the platinum-palladium-cerium-zirconium-aluminum of the present invention is lower than the platinum content, which can reduce the cost of precious metal palladium, and at the same time, platinum and palladium produce a synergistic effect to provide more reaction active sites. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0023] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0024] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0025] Example 1: A catalyst comprising platinum palladium cerium zirconium aluminum particles and yttrium oxide supported on the outside of the platinum palladium cerium zirconium aluminum particles; in this embodiment, a hydrothermal protective layer is wrapped around the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles to form a hydrothermal protective layer structure, thereby preparing a platinum palladium cerium zirconium aluminum catalyst material with a surface-loaded protective layer, which is beneficial for preventing water from entering the interior at high temperature and affecting the stability of the platinum palladium cerium zirconium aluminum, so that the material has high resistance to high hydrothermal aging, avoids direct contact between water in gaseous pollution and precious metals, stabilizes the state of precious metal platinum palladium, improves the active sites of precious metals in the catalyst material, ensures the high activity and resistance to high hydrothermal aging of the catalyst, improves the durability of the catalyst, and has better purification of carbon monoxide (CO) and nitrogen oxides (NO x ), hydrocarbon (HC) purification capacity, especially the ability to purify methane (CH4);

[0026] Furthermore, according to weight fraction, it includes 5 to 10 parts of yttrium oxide and 90 to 95 parts of platinum palladium cerium zirconium aluminum particles; in this embodiment, the preferred hydrothermal protective layer is yttrium oxide, and the precursor of yttrium oxide is a soluble nitrate aqueous solution, and is loaded on the outer layer of the platinum palladium cerium zirconium aluminum catalyst particles by impregnation. Since yttrium nitrate has good solubility, impregnation is conducive to its uniform distribution on the outer surface of the platinum palladium cerium zirconium aluminum particles. Compared with other barrier materials, it can be beneficial to isolate high-temperature water from contact with platinum palladium cerium zirconium aluminum, and at the same time does not affect the diffusion of methane; according to weight fraction, it includes 5 to 10 parts of yttrium oxide and 90 to 95 parts of platinum palladium cerium zirconium aluminum particles. If the weight fraction of yttrium oxide is higher than 5 to 10 parts, it will hinder the adsorption and diffusion of methane on the catalyst surface; if the weight fraction of yttrium oxide is less than 5 to 10 parts, yttrium oxide cannot form an effective protective layer structure on the surface of the platinum palladium cerium zirconium aluminum particles, and cannot effectively prevent water from entering and contacting the platinum palladium cerium zirconium aluminum particles at high temperature.

[0027] Furthermore, in the platinum-palladium-cerium-zirconium-aluminum material, the weight percentage of platinum is 0.45% to 3.60%, and the weight percentage of palladium is 0.05% to 0.40%; and the weight percentage of platinum is greater than the weight percentage of palladium; in this embodiment, in the platinum-palladium-cerium-zirconium-aluminum particles, the weight percentage of platinum is 0.45% to 3.60%, and the weight percentage of palladium is 0.05% to 0.40%; the precious metals platinum and palladium have a good oxidation effect on methane, but through research, it is found that when the precious metals platinum and palladium are present at the same time, especially when the content of palladium is higher than the content of platinum, the catalytic activity of palladium is inhibited, and the content of palladium in the platinum-palladium-cerium-zirconium-aluminum of the present invention is lower than the content of platinum, that is, the cost of precious metal palladium can be reduced, and at the same time, platinum and palladium produce a synergistic effect to provide more reaction active sites;

[0028] Furthermore, the cerium-zirconium-aluminum material includes aluminum oxide, lanthanum oxide, cerium oxide, and zirconium oxide. In this embodiment, aluminum oxide provides a higher specific surface area and supporting strength, and lanthanum oxide, cerium oxide, and zirconium oxide can stabilize platinum and palladium precious metals in the catalyst, which is beneficial to improving catalytic activity.

[0029] Furthermore, the cerium-zirconium-aluminum material includes 20 to 40 parts of γ-Al2O3, 5 to 15 parts of La2O3, 40 to 60 parts of CeO2 and 5 to 15 parts of ZrO2.

[0030] Example 2: Based on Example 1, the catalyst was prepared using the following steps:

[0031] 1) impregnating the outer surface of the platinum-palladium-cerium-zirconium-aluminum particles with a layer of soluble yttrium nitrate aqueous solution by an equal volume impregnation method, and aging to obtain an intermediate sample;

[0032] 2) drying and then calcining the intermediate sample prepared in step 1);

[0033] In step 1), the aging time is 10 to 15 hours; in step 2), the drying temperature is 100 to 150° C. and the drying time is 10 to 15 hours; in step 2), the calcination temperature is 600 to 700° C. and the calcination time is 2 to 4 hours;

[0034] The yttrium nitrate aqueous solution is a Y(NO3)3 aqueous solution with a mass concentration of 10.68% to 22.55%; in this embodiment, the immersion method is conducive to the uniform coating of the yttrium nitrate aqueous solution on the surface of the platinum palladium cerium zirconium aluminum particles, which is conducive to the formation of a uniform protective layer, thereby preventing water from entering and contacting the platinum palladium cerium zirconium aluminum particles at high temperatures.

[0035] The platinum-palladium-cerium-zirconium-aluminum particles are prepared by impregnating platinum nitrate and palladium nitrate solutions onto a cerium-zirconium-aluminum material, followed by drying at 100-150°C. The catalytically active platinum and palladium are loaded onto the cerium-zirconium-aluminum material through impregnation, creating a synergistic effect between the platinum and palladium, providing more reactive sites.

[0036] The platinum-palladium-cerium-zirconium-aluminum particles are prepared by impregnating platinum nitrate and palladium nitrate solutions onto a cerium-zirconium-aluminum material, followed by drying at 100-150°C. The catalytically active platinum and palladium are loaded onto the cerium-zirconium-aluminum material through impregnation, creating a synergistic effect between the platinum and palladium, providing more reactive sites.

[0037] Example 3: Based on Example 1, the catalyst includes 5 parts of yttrium oxide and 90 parts of platinum palladium cerium zirconium aluminum particles; in the platinum palladium cerium zirconium aluminum material, the weight percentage of platinum is 0.45%, and the weight percentage of palladium is 0.05%; the cerium zirconium aluminum material includes 20 parts of γ-Al2O3, 5 parts of La2O3, 40 parts of CeO2 and 5 parts of ZrO2.

[0038] Example 4: Based on Example 1, the catalyst includes 10 parts of yttrium oxide and 95 parts of platinum palladium cerium zirconium aluminum particles; in the platinum palladium cerium zirconium aluminum material, the weight percentage of platinum is 3.60%, and the weight percentage of palladium is 0.40%; the cerium zirconium aluminum material includes 40 parts of γ-Al2O3, 15 parts of La2O3, 60 parts of CeO2 and 15 parts of ZrO2.

[0039] Example 5: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 3.641 g of 18.54% platinum nitrate and 0.372 g of 20.16% palladium nitrate solution are impregnated onto 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C and then used for standby use; 180 g of mass A Y(NO3)3 aqueous solution with a concentration of 10.68% was impregnated on the above-mentioned dried powder material and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 157.895g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours for use.

[0040] Example 6: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 13.538 g of 18.54% platinum nitrate and 1.389 g of 20.16% palladium nitrate solution are respectively impregnated on 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C and then used for standby use; 180 g of mass A Y(NO3)3 aqueous solution with a concentration of 10.68% was impregnated on the above-mentioned dried powder material and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 157.895g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours for use.

[0041] Example 7: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 29.126 g of 18.54% platinum nitrate and 2.976 g of 20.16% palladium nitrate solution are respectively impregnated on 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C and then used for standby; 180 g of mass A Y(NO3)3 aqueous solution with a concentration of 10.68% was impregnated on the above-mentioned dried powder material and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 157.895g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours for use.

[0042] Example 8: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic carrier and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 29.126 g of 18.54% platinum nitrate and 2.976 g of 20.16% palladium nitrate solution are respectively impregnated on 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C and then used for standby use; 180 g of the mass The dried powder material was impregnated with a Y(NO3)3 aqueous solution with a concentration of 22.55%, and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 166.67g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% moisture and 80% air for 25 hours for use.

[0043] Comparative Example 1: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum-palladium-cerium-zirconium-aluminum catalyst coated thereon; the preparation process is as follows: 3.641 g of 18.54% platinum nitrate and 0.372 g of 20.16% palladium nitrate solution are respectively impregnated onto 149.25 g of a cerium-zirconium-aluminum material, wherein the main components of the cerium-zirconium-aluminum material are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO 2. 10 wt% ZrO2 was dried at 130°C and mixed with 250 g of water to form a slurry. The slurry was coated onto a honeycomb ceramic carrier with a diameter of 25.7 mm and a length of 70 mm at a coating loading of 150 g / L. The catalyst was dried at 130°C and calcined at 500°C for 2 hours to prepare a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours before use.

[0044] Comparative Example 2: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum-palladium-cerium-zirconium-aluminum catalyst coated thereon; the preparation process is as follows: 13.538 g of 18.54% platinum nitrate and 1.389 g of 20.16% palladium nitrate solution are respectively impregnated onto 149.25 g of cerium-zirconium-aluminum material, wherein the main components of the cerium-zirconium-aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO 2. 10 wt% ZrO2 was dried at 130°C and mixed with 250 g of water to form a slurry. The slurry was coated onto a honeycomb ceramic carrier with a diameter of 25.7 mm and a length of 70 mm at a coating loading of 150 g / L. The catalyst was dried at 130°C and calcined at 500°C for 2 hours to prepare a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours before use.

[0045] Comparative Example 3: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic carrier and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 0.405 g of 18.54% platinum nitrate and 3.348 g of 20.16% palladium nitrate solution are respectively impregnated on 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C for later use; 180 g of mass A Y(NO3)3 aqueous solution with a concentration of 10.68% was impregnated on the above-mentioned dried powder material and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 157.895g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours for use.

[0046] Comparative Example 4: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic carrier and a platinum palladium cerium zirconium aluminum catalyst coated thereon and loaded with yttrium oxide. The preparation process is as follows: 3.236 g of 18.54% platinum nitrate and 26.814 g of 20.16% palladium nitrate solution are respectively impregnated on 149.25 g of cerium zirconium aluminum material, wherein the main components of cerium zirconium aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO2, and 10 wt% ZrO2. The prepared powder material is dried at 130°C for later use; 180 g of mass A Y(NO3)3 aqueous solution with a concentration of 10.68% was impregnated on the above-mentioned dried powder material and dried at 130°C for 12 hours. The dried sample was then calcined at 650°C for 3 hours and mixed with 263g of water to prepare a slurry. The slurry was coated on a honeycomb ceramic carrier with a diameter of 25.7mm and a length of 70mm according to a coating loading of 157.895g / L. After drying at 130°C and calcining at 500°C for 2 hours, a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd was prepared. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours for use.

[0047] Comparative Example 5: Preparation of a catalyst for treating exhaust gas from a natural gas fueled engine, specifically comprising a honeycomb ceramic support and a platinum-palladium-cerium-zirconium-aluminum catalyst coated thereon. The preparation process is as follows: 3.236 g of 18.54% platinum nitrate and 26.814 g of 20.16% palladium nitrate solution are respectively impregnated onto 149.25 g of cerium-zirconium-aluminum material. The main components of cerium-zirconium-aluminum are: 30 wt% γ-Al2O3, 10 wt% La2O3, 50 wt% CeO 2. 10 wt% ZrO2 was dried at 130°C and mixed with 250 g of water to form a slurry. The slurry was coated onto a honeycomb ceramic carrier with a diameter of 25.7 mm and a length of 70 mm at a coating loading of 150 g / L. The catalyst was dried at 130°C and calcined at 500°C for 2 hours to prepare a cerium-zirconium-aluminum catalyst loaded with precious metals Pt and Pd. The prepared sample was aged at 850°C, 20% water vapor and 80% air for 25 hours before use.

[0048] The hydrothermal aging samples of the catalysts prepared in Examples 5-8 and Comparative Examples 1-5 were evaluated in a fixed bed self-heating reactor under the following conditions: 60,000 h-1 air velocity, 0.10% NO, 0.10% CO, 0.15% CH4, 0.65% O2, 5% CO2, 10% H2O, and N2 as protective gases. xThe temperature corresponding to when the conversion rate reaches 50% is used as an indicator to evaluate the catalyst ignition activity, that is, the catalyst ignition temperature T50; T50 is mainly used to compare the ignition activity of different catalysts. The test results are shown in Table 1 below.

[0049] Table 1 Hydrothermal aging test results of Examples 5-8 and Comparative Examples 1-5

[0050]

[0051] As can be seen from Table 1, the palladium content in Examples 5-7 is lower than that in platinum, which can reduce the cost of precious metal palladium and produce a synergistic effect between platinum and palladium. Furthermore, in Examples 5-7, a layer of yttrium oxide is loaded on the surface of the platinum-palladium-cerium-zirconium-aluminum catalyst to prevent water in gaseous pollution from contacting the precious metal, stabilize the valence state of the precious metal platinum-palladium, increase the active sites of the precious metal in the catalyst material, ensure the high activity and resistance to high hydrothermal aging of the catalyst, improve the durability of the catalyst, and have better purification of nitrogen oxides (NO x ) and methane (CH4) capacity. Comparing Comparative Example 1 with Example 5, and Comparative Example 2 with Example 6, by loading a layer of yttrium oxide material on the outer layer of the platinum palladium cerium zirconium aluminum particles, the hydrothermal aging resistance of the catalyst can be significantly improved. It can be seen that the yttrium oxide protective layer can prevent the water in the gaseous pollution from directly contacting the precious metals; Comparing Comparative Example 3 with Example 5, and Comparative Example 4 with Example 7, it can be found that in the platinum palladium cerium zirconium aluminum catalyst with yttrium oxide loaded on the surface, when the amount of palladium is higher than the amount of platinum, the hydrothermal aging resistance of the catalyst is worse and the activity is worse, while when the amount of platinum is higher than the amount of palladium, it is found that platinum and palladium can produce a synergistic effect in the catalytic reaction process, which can not only reduce the cost of precious metal palladium, but also increase the active sites of the precious metal in the catalyst material, thereby improving the activity of the catalyst.

[0052] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A platinum-palladium-cerium-zirconium-aluminum catalyst with yttrium oxide supported on its surface, characterized in that: A layer of yttrium oxide is loaded on the outer surface of the platinum palladium cerium zirconium aluminum particles; In parts by weight, it comprises 5 to 10 parts of yttrium oxide and 90 to 95 parts of platinum palladium cerium zirconium aluminum particles; In the platinum-palladium-cerium-zirconium-aluminum particles, the weight percentage of platinum is 0.45% to 3.60%, the weight percentage of palladium is 0.05% to 0.40%, and the weight percentage of platinum is greater than the weight percentage of palladium.

2. The catalyst according to claim 1, characterized in that: The platinum palladium cerium zirconium aluminum particles also include cerium zirconium aluminum material, and the cerium zirconium aluminum material includes aluminum oxide, lanthanum oxide, cerium oxide, and zirconium oxide.

3. The catalyst according to claim 2, characterized in that: The cerium-zirconium-aluminum material includes 20 to 40 parts of γ-Al2O3, 5 to 15 parts of La2O3, 40 to 60 parts of CeO2 and 5 to 15 parts of ZrO2.

4. A method for preparing the catalyst according to any one of claims 1 to 3, characterized in that: The steps include: 1) impregnating the outer surface of the platinum-palladium-cerium-zirconium-aluminum particles with a layer of soluble yttrium nitrate aqueous solution by an equal volume impregnation method, and aging to obtain an intermediate sample; 2) Drying and then calcining the intermediate sample prepared in step 1); obtaining the product.

5. The method for preparing the catalyst according to claim 4, wherein: In step 1), the aging time is 10 to 15 hours; in step 2), the drying temperature is 100 to 150° C. and the drying time is 10 to 15 hours; in step 2), the roasting temperature is 600 to 700° C. and the roasting time is 2 to 4 hours.

6. The method for preparing the catalyst according to claim 4, wherein: The yttrium nitrate aqueous solution is a Y(NO3)3 aqueous solution with a mass concentration of 10.68% to 22.55%.

7. The method for preparing the catalyst according to claim 4, wherein: The preparation method of the platinum-palladium-cerium-zirconium-aluminum particles is as follows: platinum nitrate and palladium nitrate solutions are respectively impregnated on cerium-zirconium-aluminum materials, and then dried at 100-150°C.

8. Use of the catalyst according to any one of claims 1 to 3, characterized in that: The catalyst is used for purifying methane and nitrogen oxides in tail gas of natural gas engines.

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