A natural gas exhaust catalyst for vehicles, a preparation method and application thereof

Abstract

The application provides a natural gas exhaust catalyst for vehicles, a preparation method and application thereof, and belongs to the field of catalysts for vehicle exhausts. The natural gas exhaust catalyst comprises a carrier and a lower catalytic coating loaded on the carrier, and further comprises an upper catalytic coating loaded on the lower catalytic coating. The lower catalytic coating comprises a Pt-Pd-based mixture, and the Pt-Pd-based mixture comprises Pt, Pd, a cerium-zirconium-praseodymium-containing solid solution, a metal additive, and Ba, Mn, and Mg modified alumina. The upper catalytic coating comprises a Rh-based mixture or a Pt-Rh-based mixture. The Rh-based mixture comprises Rh, Ba modified alumina, and a cerium-zirconium-neodymium-containing solid solution, and the Pt-Rh-based mixture comprises Pt, Rh, a cerium-zirconium-neodymium-containing solid solution, and Ba modified alumina. The catalyst of the application can effectively eliminate CO, NO X , and CH4 in the exhaust of a natural gas engine, and simultaneously reduce the generation amount of byproduct NH3.

Description

Technical Field

[0001] This invention relates to the field of catalysts for automotive exhaust, and in particular to a natural gas exhaust catalyst for vehicles, its preparation method, and its application. Background Technology

[0002] The main components of natural gas engine exhaust are carbon monoxide (CO) and nitrogen oxides (NOx). X The exhaust system of an engine typically contains NH3, an incompletely combusted form of methane (CH4). To meet emission regulations, a three-way catalytic converter is usually installed in the engine's exhaust system to remove these pollutants. However, the three-way catalytic converter inevitably produces the byproduct NH3 during its use.

[0003] According to the latest regulations on emission limits and measurement methods for pollutants from heavy-duty diesel vehicles (China Stage VI), the emission limit for NH3 is required to be below 10 ppm. To meet this requirement, current practices involve adding an ASC catalyst to the existing aftertreatment system to eliminate generated NH3 or adding other precious metals to reduce NH3 formation, as described in patent CN 113578307 A. However, this undoubtedly increases the technological cost. Therefore, a method is needed to simultaneously meet the requirements for carbon monoxide (CO) and nitrogen oxides (NOx). X Catalysts that can reduce the emission of byproduct NH3 below the limits for both the incomplete combustion of methane (CH4) and emissions of incompletely combusted methane (CH4). Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a low-NH3 generation natural gas exhaust catalyst for vehicles and its preparation method. The catalyst of this application can effectively eliminate CO and NO in natural gas engine exhaust. X It reacts with CH4 and simultaneously reduces the amount of NH3 produced as a byproduct.

[0005] To achieve the above and other related objectives, the first aspect of this application provides a natural gas exhaust catalyst for vehicles, the catalyst comprising a support and a lower catalytic coating supported on the support, and further comprising an upper catalytic coating supported on the lower catalytic coating;

[0006] The lower catalytic coating comprises a Pt-Pd based mixture, which includes Pt, Pd, a cerium-zirconium-praseodymium solid solution, metal additives, and Ba, Mn, and Mg modified alumina.

[0007] The upper catalytic coating comprises an Rh-based mixture or a Pt-Rh-based mixture; wherein the Rh-based mixture comprises Rh, Ba-modified alumina, and a cerium-zirconium-neodymium solid solution; and the Pt-Rh-based mixture comprises Pt, Rh, a cerium-zirconium-neodymium solid solution, and Ba-modified alumina.

[0008] In one embodiment of the first aspect, the catalyst support is selected from at least one of ceramics (cordierite ceramics), metals, or silicon carbide.

[0009] In a preferred embodiment, the catalyst support structure is a straight-through honeycomb type, and the particle size of the catalyst support is 300-700 mesh; preferably, the wall thickness of the straight-through honeycomb type catalyst support is 3-4 mils;

[0010] In a preferred embodiment, the metal additive is a Mg additive and / or a Ba additive.

[0011] In a preferred embodiment, the Mg additive is a nitrate or hydroxide of Mg; the Ba additive is a sulfate or hydroxide of Ba.

[0012] In one embodiment of the first aspect, the Pt-Pd based mixture contains the following components: Pt 0.1-1 wt.%; Pd 0.1-1 wt.%; Ba, Mn, and Mg modified alumina 10-45 wt.%; cerium-zirconium-praseodymium solid solution 40-75 wt.%; and metal additives 1-15 wt.%.

[0013] As a preferred embodiment, the contents of each component in the cerium-zirconium-praseodymium solid solution are as follows: CeO2 content is 70-90 wt.%, ZrO2 content is 3-10 wt.%, Pr2O3 content is 3-10 wt.%, La2O3 content is 0-5 wt.%, and Y2O3 content is 0-5 wt.%.

[0014] As a preferred embodiment, the contents of each component in the cerium-zirconium-praseodymium solid solution are as follows: CeO2 content is 75-85 wt.%, ZrO2 content is 4-6 wt.%, Pr2O3 content is 3-8 wt.%, La2O3 content is 3-6 wt.%, and Y2O3 content is 3-8 wt.%.

[0015] In a preferred embodiment, Pt is derived from the hydrochloride or nitrate of Pt; Pd is derived from the hydrochloride or nitrate of Pd.

[0016] In a preferred embodiment, the Pt-Pd based mixture contains the following components: Pt 0.1-0.5 wt.%; Pd 0.1-0.5 wt.%; Ba, Mn, and Mg modified alumina 30-45 wt.%; cerium-zirconium-praseodymium solid solution 45-60 wt.%; and metal additives 5-10 wt.%.

[0017] In one embodiment of the first aspect, the Rh-based mixture comprises the following components: Rh 0.1-1 wt.%, Ba-modified alumina 8-25 wt.%, and cerium-zirconium-neodymium solid solution 70-90 wt.%.

[0018] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 70-90 wt.%, ZrO2 content 3-10 wt.%, Nd2O3 content 3-10 wt.%, La2O3 content 0-10 wt.%, and Y2O3 content 0-10 wt.%.

[0019] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 75-85 wt.%, ZrO2 content 3-6 wt.%, Nd2O3 content 3-6 wt.%, La2O3 content 3-8 wt.%, and Y2O3 content 3-8 wt.%.

[0020] As a preferred embodiment, the Rh-based mixture contains the following components: Rh 0.1-0.5 wt.%, Ba-modified alumina 8-15 wt.%, and cerium-zirconium-neodymium solid solution 80-90 wt.%.

[0021] In a preferred embodiment, Rh is derived from the hydrochloride or nitrate of Rh.

[0022] In one embodiment of the first aspect, the Pt-Rh based mixture comprises the following components: Pt 0.1-1 wt.%, Rh 0.1-1 wt.%, Ba-modified alumina 8-25 wt.%, and cerium-zirconium-neodymium solid solution 70-90 wt.%.

[0023] As a preferred embodiment, the Pt-Rh based mixture contains the following components: Pt 0.1-0.5 wt.%, Rh 0.1-0.5 wt.%, Ba-modified alumina 8-15 wt.%, and cerium-zirconium-neodymium solid solution 80-90 wt.%.

[0024] In a preferred embodiment, Rh is derived from the hydrochloride or nitrate of Rh; Pt is derived from the hydrochloride or nitrate of Pt.

[0025] In one embodiment of the first aspect, the catalyst has the following loadings: Pt loading is 0.1–5 g / L, Rh loading is 0.1–1 g / L, and Pd loading is 0.1–2.5 g / L.

[0026] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 70-90 wt.%, ZrO2 content 3-10 wt.%, Nd2O3 content 3-10 wt.%, La2O3 content 0-10 wt.%, and Y2O3 content 0-10 wt.%.

[0027] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 75-85 wt.%, ZrO2 content 3-6 wt.%, Nd2O3 content 3-6 wt.%, La2O3 content 3-8 wt.%, and Y2O3 content 3-8 wt.%.

[0028] The second aspect of this application provides a method for preparing the above-mentioned vehicle natural gas exhaust catalyst, comprising the following steps:

[0029] Preparation of the lower catalytic coating of the catalyst;

[0030] 1) Preparation of Pd-based slurry: Add cerium-zirconium-praseodymium solid solution to water to make slurry, add metal additives and then add metal Pd solution dropwise, stir for 30-60 min;

[0031] As a preferred technical solution, the particle size of the cerium-zirconium-praseodymium solid solution is D90 = 12-14 μm; the metal Pd solution is a Pd hydrochloride, nitrate, or sulfate.

[0032] 2) Preparation of Pt-based slurry: The surface of Ba-modified alumina is pre-impregnated with Mg and Mn solutions, calcined and ground, then metal additives are added and metal Pt solution is added dropwise, and stirred for 30-60 min.

[0033] As a preferred technical solution, the Mg solution is Mg hydrochloride, nitrate or sulfate; the Mn solution is Mn hydrochloride, nitrate or sulfate; in step 2), the calcination temperature is 550-600℃ and the calcination time is 1-2h; and the material is ground to D90 = 12-14μm.

[0034] 3) After mixing Pd-based slurry and Pt-based slurry, adjust the pH of the mixture to 5-6, the viscosity to 500-1000 cp, and the solid content to 30-40 wt%. Coat the mixture onto a support and calcine to obtain a catalyst with a lower catalytic coating. The upper catalytic coating of the catalyst can be prepared using Rh-based slurry or Pt-Rh-based slurry.

[0035] As a preferred technical solution, the pH adjuster for adjusting the mixture is selected from at least one of ammonia or tetramethylamine; the viscosity adjuster for adjusting the mixture is selected from at least one of boehmite or carboxymethyl cellulose; deionized water is used to adjust the solid content of the mixture; in step 3), the calcination temperature is 500-800℃ and the calcination time is 1-3h.

[0036] 4) If the catalytic coating is made of Rh-based slurry, the preparation of Rh-based slurry is as follows: Ba-modified alumina and cerium-zirconium-neodymium solid solution are added to water to make slurry, metal Rh solution is added, and the mixture is stirred for 30-60 min.

[0037] As a preferred technical solution, the particle size of the cerium-zirconium-neodymium solid solution is D90 = 12-14 μm; the metal Rh solution is the hydrochloride, nitrate or sulfate of Rh.

[0038] 5) If the catalytic coating is selected from Pt-Rh based slurry, the preparation of Pt-Rh based slurry is as follows: add Ba modified alumina and cerium-zirconium-neodymium solid solution to water to make slurry, add metal Rh solution and metal Pt solution, and stir for 30-60 min.

[0039] As a preferred technical solution, the particle size of the cerium-zirconium-neodymium solid solution is D90 = 12-14 μm; the metal Rh solution is the hydrochloride, nitrate or sulfate of Rh; and the metal Pt solution is the hydrochloride, nitrate or sulfate of Pt.

[0040] 6) Using either slurry 4) or slurry 5), the following method is used: adjust the pH of the slurry system to 4-5, adjust the viscosity of the mixture system to 500-1000cp, adjust the solid content of the mixture system to 30-40wt%, coat the mixture system onto the carrier, and calcine to obtain the vehicle natural gas exhaust catalyst.

[0041] As a preferred technical solution, the pH adjuster for adjusting the slurry system is selected from at least one of acetic acid, citric acid or oxalic acid; the viscosity adjuster for adjusting the slurry system is selected from at least one of boehmite or carboxymethyl cellulose; deionized water is used to adjust the solid content of the mixture; in step 6), the calcination temperature is 500-800℃ and the calcination time is 1-3h.

[0042] The third aspect of this application provides a catalyst prepared by the above-described method for preparing a natural gas exhaust catalyst for vehicles.

[0043] The fourth aspect of this application provides the use of a catalyst in exhaust gas treatment, for example, the catalyst may be installed downstream of an engine, used alone or in combination with other catalysts as part of the engine exhaust pipe.

[0044] As described above, the catalyst of the present invention and its application have at least the following beneficial effects: 1) The noble metal Pt supported on Ba, Mg and Mn modified alumina can quickly convert CO and some hydrocarbons into CO2 and H2O. The presence of Ba and / or Mn promoters is beneficial to the conversion of hydrocarbons and nitrogen oxides at low temperatures. CeO2 has a fast oxygen storage and release rate and can better cope with the changes in air-fuel ratio during pollutant conversion.

[0045] 2) The noble metal Pd supported on the cerium-zirconium-lanthanum-yttrium-praseodymium solid solution can effectively promote the vapor reforming reaction of the remaining hydrocarbons (CH4) to CO and H2, while some of the generated H2 will also be converted into H2O by Pt.

[0046] 3) Rh loaded on cerium-zirconium-lanthanum-yttrium-neodymium solid solution can effectively promote the reduction reaction of NOx with H2 and CO to generate N2 and reduce the generation of NH3.

[0047] 4) The three-way catalyst structure of this application does not require the use of an additional ammonia oxidation catalyst, which is low in cost and easy to manufacture. It effectively reduces pollution and greatly reduces the amount of ammonia generated. Compared with catalysts that place platinum and palladium in the outlet section and rhodium in the inlet section, or catalysts that place platinum, palladium and rhodium in the same layer without segmentation, the tail gas treatment effect is better and the amount of ammonia generated is the lowest. Attached Figure Description

[0048] Figure 1 This is a graph showing the change of NH3 concentration with temperature during the catalytic reaction process of the catalysts in Comparative Example 1 and various embodiments of the present invention.

[0049] Figure 2 This is a graph showing the CH4 conversion rate of the catalysts in Comparative Example 1 and various embodiments of the present invention as a function of temperature during the catalytic reaction process.

[0050] Figure 3 This is a graph showing the NO conversion rate as a function of temperature during the catalytic reaction process of the catalysts in Comparative Example 1 and various embodiments of the present invention.

[0051] Figure 4 This is a graph showing the CO conversion rate as a function of temperature during the catalytic reaction process of the catalysts in Comparative Example 1 and various embodiments of the present invention. Detailed Implementation

[0052] The inventors of this application aim to develop a solution that satisfies both carbon monoxide (CO) and nitrogen oxides (NO) X To address the emission limits for incomplete combustion of methane (CH4) and to reduce the emission of the byproduct NH3 below the limits, a catalyst was developed. Research revealed that by using a Pt-Pd-based mixture as the lower catalytic coating and an Rh-based or Pt-Rh-based mixture as the upper catalytic coating, an ammonia oxidation catalyst could be produced without the need for an additional catalyst. This approach is cost-effective, easy to manufacture, and significantly reduces pollution while drastically decreasing ammonia generation. This invention was developed based on these findings.

[0053] The first aspect of the present invention provides a natural gas exhaust catalyst for vehicles, the catalyst comprising a support and a lower catalytic coating supported on the support, and an upper catalytic coating supported on the lower catalytic coating;

[0054] The lower catalytic coating comprises a Pt-Pd based mixture, which includes Pt, Pd, a cerium-zirconium-praseodymium solid solution, metal additives, and Ba, Mn, and Mg modified alumina.

[0055] The upper catalytic coating comprises an Rh-based mixture or a Pt-Rh-based mixture; wherein the Rh-based mixture comprises Rh, Ba-modified alumina, and a cerium-zirconium-neodymium solid solution; and the Pt-Rh-based mixture comprises Pt, Rh, a cerium-zirconium-neodymium solid solution, and Ba-modified alumina. That is, the upper catalytic coating has two options: a coating prepared from an Rh-based mixture or a coating prepared from a Pt-Rh-based mixture.

[0056] In one embodiment of the first aspect, the catalyst support is selected from at least one of ceramics (cordierite ceramics), metals, or silicon carbide. The support, serving as the carrier for the catalytic coating, is selected according to the actual application requirements; in this application, a cordierite ceramic support is preferred.

[0057] In a preferred embodiment, the catalyst support structure is a straight-through honeycomb type, and the particle size of the catalyst support is 300-700 mesh, for example, 300-400 mesh, 400-500 mesh, 500-600 mesh, or 600-700 mesh. Preferably, the wall thickness of the straight-through honeycomb catalyst support is 3-4 mils. A reasonable honeycomb wall thickness is beneficial for balancing the loading of the catalyst coating and the catalyst performance, that is, maximizing the loading of the catalyst coating while ensuring the catalyst performance.

[0058] In a preferred embodiment, the metal additive is a Mg additive and / or a Ba additive. Experimental studies have shown that the presence of Ba and / or Mn additives is beneficial for the conversion of hydrocarbons and nitrogen oxides at low temperatures. In a preferred embodiment, the Mg additive is a nitrate or hydroxide of Mg, such as magnesium nitrate or magnesium hydroxide. The Ba additive is a sulfate or hydroxide of Ba, such as barium sulfate or barium hydroxide.

[0059] In one embodiment of the first aspect, the Pt-Pd based mixture comprises the following components: Pt 0.1-1 wt.%; Pd 0.1-1 wt.%; Ba, Mn, and Mg modified alumina 10-45 wt.%; cerium-zirconium-praseodymium solid solution 40-75 wt.%; and metal additives 1-15 wt.%. The content of each component in the Pt-Pd based mixture can also be as follows: Pt can be selected as 0.1-0.3 wt.%, 0.3-0.5 wt.%, 0.5-0.8 wt.%, or 0.8-1 wt.%; Pd can be selected as 0.1-0.3 wt.%, 0.3-0.5 wt.%, 0.5-0.8 wt.%, or 0.8-1 wt.%; Ba, Mn, and Mg modified alumina can be selected as 10-15 wt.%, 15-30 wt.%, or 30-45 wt.%; Cerium-zirconium-praseodymium solid solution can be 40-50 wt.%, 50-60 wt.%, or 60-75 wt.%; Metal additives can be 1-3 wt.%, 3-5 wt.%, 5-10 wt.%, or 10-15 wt.%. The noble metal Pd supported on the cerium-zirconium-lanthanum-yttrium-praseodymium solid solution can effectively promote the vapor reforming reaction of the remaining hydrocarbons (CH4) into CO and H2, while some of the generated H2 will also be converted into H2O by Pt.

[0060] As a preferred embodiment, the contents of each component in the cerium-zirconium-praseodymium solid solution are as follows: CeO2 content is 70-90 wt.%, ZrO2 content is 3-10 wt.%, Pr2O3 content is 3-10 wt.%, La2O3 content is 0-5 wt.%, and Y2O3 content is 0-5 wt.%.

[0061] In a preferred embodiment, the contents of each component in the cerium-zirconium-praseodymium solid solution are as follows: CeO2 content 75-85 wt.%, ZrO2 content 4-6 wt.%, Pr2O3 content 3-8 wt.%, La2O3 content 3-6 wt.%, and Y2O3 content 3-8 wt.%. The CeO2 in the cerium-zirconium-praseodymium solid solution has a rapid oxygen storage and release rate, which can better cope with changes in the air-fuel ratio during pollutant conversion.

[0062] In a preferred embodiment, Pt is derived from the hydrochloride or nitrate of Pt, and Pd is derived from the hydrochloride or nitrate of Pd.

[0063] In a preferred embodiment, the Pt-Pd based mixture contains the following components: Pt 0.1-0.5 wt.%; Pd 0.1-0.5 wt.%; Ba, Mn, and Mg modified alumina 30-45 wt.%; cerium-zirconium-praseodymium solid solution 45-60 wt.%; and metal additives 5-10 wt.%.

[0064] In a preferred embodiment, the content of each component in the Pt-Pd based mixture is as follows: Pt can be 0.1-0.2 wt.%, 0.2-0.3 wt.%, or 0.3-0.5 wt.%; Pd can be 0.1-0.2 wt.%, 0.2-0.3 wt.%, or 0.3-0.5 wt.%; Ba, Mn, and Mg modified alumina can be 30-35 wt.%, 35-40 wt.%, or 40-45 wt.%; cerium-zirconium-praseodymium solid solution can be 45-50 wt.%, 50-55 wt.%, or 55-60 wt.%; and metal additives can be 5-8 wt.% or 8-10 wt.%.

[0065] In one embodiment of the first aspect, the Rh-based mixture comprises the following components: Rh 0.1-1 wt.%, Ba-modified alumina 8-25 wt.%, and cerium-zirconium-neodymium solid solution 70-90 wt.%.

[0066] In a preferred embodiment, the content of each component in the Rh-based mixture is as follows: Rh can be 0.1-0.3 wt.%, 0.3-0.5 wt.%, 0.5-0.8 wt.%, or 0.8-1 wt.%; Ba-modified alumina can be 8-12 wt.%, 12-15 wt.%, 15-20 wt.%, or 20-25 wt.%; and the cerium-zirconium-neodymium solid solution can be 70-80 wt.% or 80-90 wt.%. Rh supported on the cerium-zirconium-lanthanum-yttrium-neodymium solid solution can effectively promote the reduction reaction of NOx with H2 and CO to generate N2, and reduce the generation of NH3.

[0067] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 70-90 wt.%, ZrO2 content 3-10 wt.%, Nd2O3 content 3-10 wt.%, La2O3 content 0-10 wt.%, and Y2O3 content 0-10 wt.%.

[0068] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 75-85 wt.%, ZrO2 content 3-6 wt.%, Nd2O3 content 3-6 wt.%, La2O3 content 3-8 wt.%, and Y2O3 content 3-8 wt.%.

[0069] As a preferred embodiment, the Rh-based mixture contains the following components: Rh 0.1-0.5 wt.%, Ba-modified alumina 8-15 wt.%, and cerium-zirconium-neodymium solid solution 80-90 wt.%.

[0070] In a preferred embodiment, the content of each component in the Rh-based mixture is as follows: Rh can be 0.1-0.3 wt.% or 0.3-0.5 wt.%, Ba-modified alumina can be 8-10 wt.% or 10-15 wt.%, and the cerium-zirconium-neodymium solid solution can be 80-85 wt.% or 85-90 wt.%.

[0071] In a preferred embodiment, Rh is derived from the hydrochloride or nitrate of Rh.

[0072] In one embodiment of the first aspect, the Pt-Rh based mixture comprises the following components: Pt 0.1-1 wt.%, Rh 0.1-1 wt.%, Ba-modified alumina 8-25 wt.%, and cerium-zirconium-neodymium solid solution 70-90 wt.%.

[0073] In a preferred embodiment, the content of each component in the Pt-Rh based mixture is as follows: Pt can be 0.1-0.3 wt.%, 0.3-0.5 wt.%, 0.5-0.8 wt.%, or 0.8-1 wt.%; Ba-modified alumina can be 8-12 wt.%, 12-15 wt.%, 15-20 wt.%, or 20-25 wt.%; and the cerium-zirconium-neodymium solid solution can be 70-80 wt.% or 80-90 wt.%.

[0074] As a preferred embodiment, the Pt-Rh based mixture contains the following components: Pt 0.1-0.5 wt.%, Rh 0.1-0.5 wt.%, Ba-modified alumina 8-15 wt.%, and cerium-zirconium-neodymium solid solution 80-90 wt.%.

[0075] In a preferred embodiment, the content of each component in the Pt-Rh based mixture is as follows: Pt can be 0.1-0.3 wt.% or 0.3-0.5 wt.%, Rh can be 0.1-0.3 wt.% or 0.3-0.5 wt.%, Ba-modified alumina can be 8-12 wt.% or 12-15 wt.%, and the cerium-zirconium-neodymium solid solution can be 80-85 wt.% or 85-90 wt.%.

[0076] In a preferred embodiment, Rh is derived from the hydrochloride or nitrate of Rh; Pt is derived from the hydrochloride or nitrate of Pt.

[0077] In one embodiment of the first aspect, the catalyst contains: Pt loading of 0.1–5 g / L, Rh loading of 0.1–1 g / L, and Pd loading of 0.1–2.5 g / L. As a preferred embodiment, the catalyst contains: Pt loading of 0.1–0.5 g / L, 0.5–1 g / L, 1–2 g / L, 2–3 g / L, 3–4 g / L, or 4–5 g / L; Rh loading of 0.1–0.3 g / L, 0.3–0.5 g / L, or 0.5–1 g / L; and Pd loading of 0.1–0.5 g / L, 0.5–1 g / L, 1–1.5 g / L, 1.5–2 g / L, or 2–2.5 g / L.

[0078] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 70-90 wt.%, ZrO2 content 3-10 wt.%, Nd2O3 content 3-10 wt.%, La2O3 content 0-10 wt.%, and Y2O3 content 0-10 wt.%.

[0079] As a preferred embodiment, the contents of each component in the cerium-zirconium-neodymium solid solution are as follows: CeO2 content 75-85 wt.%, ZrO2 content 3-6 wt.%, Nd2O3 content 3-6 wt.%, La2O3 content 3-8 wt.%, and Y2O3 content 3-8 wt.%.

[0080] The second aspect of this application provides a method for preparing the above-mentioned vehicle natural gas exhaust catalyst, comprising the following steps:

[0081] Preparation of the lower catalytic coating of the catalyst;

[0082] 1) Preparation of Pd-based slurry: Add cerium-zirconium-praseodymium solid solution to water to make slurry, add metal additives and then add metal Pd solution dropwise, stir for 30-60 min;

[0083] As a preferred technical solution, the particle size of the cerium-zirconium-praseodymium solid solution is D90 = 12-14 μm; the metal Pd solution is a Pd hydrochloride, nitrate, or sulfate.

[0084] 2) Preparation of Pt-based slurry: The surface of Ba-modified alumina is pre-impregnated with Mg and Mn solutions, calcined and ground, then metal additives are added and metal Pt solution is added dropwise, and stirred for 30-60 min.

[0085] As a preferred technical solution, the Mg solution is Mg hydrochloride, nitrate or sulfate; the Mn solution is Mn hydrochloride, nitrate or sulfate; in step 2), the calcination temperature is 550-600℃ and the calcination time is 1-2h; and the material is ground to D90 = 12-14μm.

[0086] 3) After mixing Pd-based and Pt-based slurries, adjust the pH of the mixture to 5-6, the viscosity to 500-1000 cp, and the solid content to 30-40 wt%. Coat the mixture onto a support and calcine to obtain a catalyst with a lower catalytic coating. The upper catalytic coating can be prepared using Rh-based or Pt-Rh-based slurries. The pH of the mixture can be adjusted to 5-5.5 or 5.5-6, the viscosity to 500-800 cp or 800-1000 cp, and the solid content to 30-35 wt% or 35-40 wt%.

[0087] As a preferred technical solution, the pH adjuster for adjusting the mixture is selected from at least one of ammonia or tetramethylamine; the viscosity adjuster for adjusting the mixture is selected from at least one of boehmite or carboxymethyl cellulose; deionized water is used to adjust the solid content of the mixture; in step 3), the calcination temperature is 500–800℃, and the calcination time is 1–3 h. The calcination temperature can be 500–600℃, 600–700℃, or 700–800℃, and the calcination time can be 1–2 h or 2–3 h.

[0088] 4) If the catalytic coating is made of Rh-based slurry, the preparation of Rh-based slurry is as follows: Ba-modified alumina and cerium-zirconium-neodymium solid solution are added to water to make slurry, metal Rh solution is added, and the mixture is stirred for 30-60 min.

[0089] As a preferred technical solution, the particle size of the cerium-zirconium-neodymium solid solution is D90 = 12-14 μm; the metal Rh solution is the hydrochloride, nitrate or sulfate of Rh.

[0090] 5) If the catalytic coating is selected from Pt-Rh based slurry, the preparation of Pt-Rh based slurry is as follows: add Ba modified alumina and cerium-zirconium-neodymium solid solution to water to make slurry, add metal Rh solution and metal Pt solution, and stir for 30-60 min.

[0091] As a preferred technical solution, the particle size of the cerium-zirconium-neodymium solid solution is D90 = 12-14 μm; the metal Rh solution is the hydrochloride, nitrate or sulfate of Rh; and the metal Pt solution is the hydrochloride, nitrate or sulfate of Pt.

[0092] 6) Using either slurry 4) or 5), the following method is employed: adjust the pH of the slurry system to 4-5, adjust the viscosity of the mixture to 500-1000 cp, and adjust the solid content of the mixture to 30-40 wt%. Then, coat the mixture onto a carrier and calcine to obtain the vehicle natural gas exhaust catalyst. Specifically, the pH of the slurry system can be adjusted to 5-5.5 or 5.5-6, the viscosity of the mixture can be adjusted to 500-800 cp or 800-1000 cp, and the solid content of the mixture can be adjusted to 30-35 wt% or 35-40 wt%.

[0093] As a preferred technical solution, the pH adjuster for the slurry system is selected from at least one of acetic acid, citric acid, or oxalic acid; the viscosity adjuster for the slurry system is selected from at least one of boehmite or carboxymethyl cellulose; deionized water is used to adjust the solid content of the mixture; in step 6), the calcination temperature is 500–800℃, and the calcination time is 1–3 h. The calcination temperature can be 500–600℃, 600–700℃, or 700–800℃, and the calcination time can be 1–2 h or 2–3 h.

[0094] The third aspect of this application provides a catalyst prepared by the above-described method for preparing a natural gas exhaust catalyst for vehicles.

[0095] The fourth aspect of this application provides the use of a catalyst in exhaust gas treatment, for example, the catalyst may be installed downstream of an engine, used alone or in combination with other catalysts as part of the engine exhaust pipe.

[0096] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0097] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0098] Example 1

[0099] The preparation of the lower catalytic coating of the catalyst, specifically the material composition and coating method, are as follows:

[0100] 1) Weigh 123g of a cerium-zirconium-lanthanum-yttrium-praseodymium solid solution with a D90 of 12-14μm (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Pr2O3 content 5wt.%) and add it to deionized water to make a slurry. Add 14g of barium hydroxide octahydrate and stir for 30min. While stirring, add 6g of 10wt.% palladium nitrate solution dropwise and stir for 30min to obtain a Pd-based slurry.

[0101] 2) 80g of Ba-modified alumina (with BaO content of 10wt.%) was pre-impregnated with 10g of magnesium nitrate and 15g of manganese nitrate solution. After calcination at 600℃, it was ground to D90 = 12-14μm. 14g of barium hydroxide octahydrate was added and stirred for 30min. While stirring, 7g of 10wt.% platinum nitrate solution was added dropwise and stirred for 30min to obtain Pt-based slurry.

[0102] 3) After mixing Pd-based slurry and Pt-based slurry, tetramethylamine was added to adjust the pH to 5.5, boehmite and carboxymethyl cellulose were added to adjust the viscosity to 600 cp, and deionized water was added to adjust the solid content to 32 wt.%. The resulting slurry was quantitatively coated onto a 1*3in, 600 / 3 specification straight-through honeycomb cordierite honeycomb ceramic catalyst carrier on a special sample coating machine, and calcined in air at 550℃ for 2 hours to obtain a catalyst with a lower catalytic coating.

[0103] The preparation of the upper catalytic coating of the catalyst, wherein the upper catalytic coating is a Pt-Rh based slurry, and the specific material composition and coating method are as follows:

[0104] 5) Weigh 25g of Ba-modified alumina (BaO content 10wt.%) with D90 = 12-14μm and 190g of cerium-zirconium-lanthanum-neodymium solid solution (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Nd2O3 content 5wt.%) with D90 = 12-14μm and add it to deionized water to make a slurry. Add 14g of 10wt.% platinum nitrate aqueous solution and 1.4g of... A 10 wt.% rhodium nitrate aqueous solution was stirred for 30 min, and the pH was adjusted to 4.5 with citric acid. Boehmite and carboxymethyl cellulose were added to adjust the viscosity to 600 cp, and deionized water was added to adjust the solid content to 31%. The mixture was stirred for 1 h to obtain a catalyst PtRh coating slurry. This slurry was then coated onto the catalyst with the lower catalytic coating prepared above using a sample coating machine. The catalyst was then calcined in air at 550 °C for 2 h to obtain the finished catalyst, which is referred to as Example 1.

[0105] Example 2

[0106] The preparation of the lower catalytic coating of the catalyst, specifically the material composition and coating method, are as follows:

[0107] 1) Weigh 123g of a cerium-zirconium-lanthanum-yttrium-praseodymium solid solution with a D90 of 12-14μm (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Pr2O3 content 5wt.%) and add it to deionized water to make a slurry. Add 14g of barium hydroxide octahydrate and stir for 30min. While stirring, add 6g of 10wt.% palladium nitrate solution dropwise and stir for 30min to obtain a Pd-based slurry.

[0108] 2) 80g of Ba-modified alumina (with BaO content of 10wt.%, commercially available product AB10) was pre-impregnated with 10g of magnesium nitrate and 15g of manganese nitrate solution. After calcination at 600℃, it was ground to D90 = 12-14um. 14g of barium hydroxide octahydrate was added and stirred for 30min. While stirring, 14g of 10wt.% platinum nitrate solution was added dropwise and stirred for 30min to obtain Pt-based slurry.

[0109] 3) After mixing Pd-based and Pt-based slurries, tetramethylamine was added to adjust the pH to 5.5, boehmite and carboxymethyl cellulose were added to adjust the viscosity to 600 cp, and deionized water was added to adjust the solid content to 32%. The resulting slurry was quantitatively coated onto a 1*3in, 600 / 3 specification straight-through honeycomb cordierite honeycomb ceramic catalyst carrier on a special sample coating machine, and calcined in air at 550℃ for 2 hours to obtain a catalyst with a lower catalytic coating.

[0110] The preparation of the upper catalytic coating of the catalyst, wherein the upper catalytic coating is a Pt-Rh based slurry, and the specific material composition and coating method are as follows:

[0111] 5) Weigh 25g of Ba-modified alumina (BaO content 10wt.%) with a D90 of 12-14μm and 190g of cerium-zirconium-lanthanum-neodymium solid solution (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Nd2O3 content 5wt.%) with a D90 of 12-14μm and add it to deionized water to make a slurry. Add 7g of 10wt.% platinum nitrate aqueous solution and 1.4g of... A 10 wt.% rhodium nitrate aqueous solution was stirred for 30 min, and the pH was adjusted to 4.5 with citric acid. Boehmite and carboxymethyl cellulose were added to adjust the viscosity to 600 cp, and deionized water was added to adjust the solid content to 31%. The mixture was stirred for 1 h to obtain a Pt-Rh catalyst coating slurry. This slurry was then coated onto the catalyst with the lower catalytic coating prepared above using a sample coating machine. The catalyst was then calcined in air at 550 °C for 2 h to obtain the finished catalyst, which is recorded as Example 2.

[0112] Example 3

[0113] The preparation of the lower catalytic coating of the catalyst, specifically the material composition and coating method, are as follows:

[0114] 1) Weigh 123g of a cerium-zirconium-lanthanum-yttrium-praseodymium solid solution with a D90 of 12-14μm (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Pr2O3 content 5wt.%) and add it to deionized water to make a slurry. Add 14g of barium hydroxide octahydrate and stir for 30min. While stirring, add 6g of 10wt.% palladium nitrate solution dropwise and stir for 30min to obtain a Pd-based slurry.

[0115] 2) 80g of Ba-modified alumina (BaO content 10%, commercially available product AB10) was pre-impregnated with 10g of magnesium nitrate and 15g of manganese nitrate solution. After calcination at 600℃, it was ground to D90 = 12-14μm. 14g of barium hydroxide octahydrate was added and stirred for 30min. While stirring, 21g of 10wt.% platinum nitrate solution was added dropwise and stirred for 30min to obtain Pt-based slurry.

[0116] 3) After mixing Pd-based and Pt-based slurries, tetramethylamine was added to adjust the pH to 5.5, boehmite and carboxymethyl cellulose were added to adjust the viscosity to 600 cp, and deionized water was added to adjust the solid content to 32%. The resulting slurry was quantitatively coated onto a 1*3in, 600 / 3 specification straight-through honeycomb cordierite honeycomb ceramic catalyst carrier on a special sample coating machine, and calcined in air at 550℃ for 2 hours to obtain a catalyst with a lower catalytic coating.

[0117] The preparation of the upper catalytic coating of the catalyst, wherein the upper catalytic coating is made of Rh-based slurry, and the specific material composition and coating method are as follows:

[0118] 4) Weigh 25g of Ba-modified alumina (BaO content 10wt.%) with D90 = 12-14μm and 190g of cerium-zirconium-lanthanum-neodymium solid solution (CeO2 content 80wt.%, ZrO2 content 5wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Nd2O3 content 5wt.%) with D90 = 12-14μm and add it to deionized water to make a slurry. Add 1.4g of 10wt.% rhodium nitrate aqueous solution dropwise and stir for 30min. Adjust the pH to 4.5 with citric acid. Add boehmite and carboxymethyl cellulose to adjust the viscosity to 600cp. Add deionized water to adjust the solid content to 31%. Stir for 1h to obtain the catalyst Pt-Rh coating slurry. Apply it to the catalyst with the lower catalytic coating obtained above on a sample coating machine. Calcine in air at 550℃ for 2h to obtain the finished catalyst, which is recorded as Example 3.

[0119] Comparative Example 1

[0120] 1) Preparation and coating of Pd-based coating slurry: Weigh 124g of La-modified alumina (La2O3 content 5wt.%, commercially available A4) with D90 = 12-14μm and 90g of cerium-zirconium-lanthanum-yttrium-praseodymium solid solution (CeO2 content 40wt.%, ZrO2 content 45wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Pr2O3 content 5wt.%) with D90 = 12-14μm and add it to deionized water to make a slurry. Add 6g dropwise. A 10wt.% nitric acid Pd aqueous solution was stirred for 30 min, the pH was adjusted to 4.5 with acetic acid, 7.5 g of aluminum sol and hydroxyethyl cellulose were added to adjust the viscosity to 600 cp, deionized water was added to adjust the solid content to 32%, and the mixture was stirred for 1 h to obtain a Pd-based catalyst coating slurry. The obtained slurry was quantitatively coated onto a 1*3in, 600 / 3 specification straight-through honeycomb cordierite honeycomb ceramic catalyst carrier on a special sample coating machine to obtain a semi-finished catalyst.

[0121] 2) A mixture of Rh-based and Pt-based catalytic active materials is used as the top coating. The specific material composition and coating method are as follows:

[0122] Weigh 37g of La-modified alumina (La2O3 content 5wt.%, commercially available A4) with D90 = 12-14um and 182g of cerium-zirconium-lanthanum-yttrium-neodymium solid solution (CeO2 content 40wt.%, ZrO2 content 45wt.%, La2O3 content 5wt.%, Y2O3 content 5wt.%, Nd2O3 content 5wt.%) with D90 = 12-14um and add it to deionized water to make a slurry. Add 21g of 10wt.% platinum nitrate aqueous solution and 1.4g of 10wt.% rhodium nitrate aqueous solution dropwise and stir for 30min. Adjust the pH to 5.5 with ammonia water, add 7.5g of aluminum sol and hydroxyethyl cellulose to adjust the viscosity to 600cp, add deionized water to adjust the solid content to 31%, and stir for 1h to obtain a Pt-Rh mixed coating slurry for the catalyst. Apply the obtained slurry quantitatively to the semi-finished catalyst in step 1 on a special sample coating machine to obtain the finished catalyst, which is referred to as Comparative Example 1.

[0123] The catalysts obtained in Examples 1-3: Examples 1, 2, and 3, and the catalyst obtained in Comparative Example 1 were evaluated for their effectiveness.

[0124] The catalysts prepared in Comparative Example 1 and Examples 1 to 3 were evaluated for catalyst activity using a simulated atmosphere evaluation system. The simulated atmosphere consisted of 1000 ppm CH4, 5000 ppm CO, 1500 ppm NO, 10 vol.% H2O, and 8 vol.% CO2, with N2 as the balance gas and a space velocity of 60000 h⁻¹. -1 The air-fuel ratio Lambda was controlled by adjusting the O2 concentration, and the Lambda was kept stable at 0.992 during the test.

[0125] like Figure 1 The graph shows the NH3 concentration versus temperature curves of the catalysts in Comparative Example 1 and various embodiments of the present invention during the catalytic reaction. It can be seen from the graph that the NH3 formation concentrations in Examples 1, 2, and 3 are much lower than those in Comparative Example 1. Specifically, the NH3 formation concentrations in Examples 2 and 3 are less than 10 ppm, and in particular, the NH3 formation concentration in Example 3 is almost 0 ppm. This indicates that the improved catalyst significantly reduces NH3 formation.

[0126] like Figure 2 As shown in the figure, the CH4 conversion rate of the catalysts in Comparative Example 1 and various embodiments of the present invention changes with temperature during the catalytic reaction process. The highest CH4 conversion rate of the comparative example is about 95%, while the highest conversion rate of Examples 1, 2 and 3 is 100%. This shows that the improved catalyst has significantly improved the CH4 conversion rate while ensuring a low NH3 generation.

[0127] like Figure 3As shown in the figure, the NO conversion rate of the catalysts in Comparative Example 1 and various embodiments of the present invention changes with temperature during the catalytic reaction process. The ignition temperature of Embodiments 1, 2 and 3 is significantly lower than that of Comparative Example 1. Among them, the ignition temperature of Embodiment 3, which has the best performance, is reduced by about 50°C. While reducing the amount of NH3 generated, it improves the NO conversion efficiency.

[0128] like Figure 4 As shown in the figure, the CO conversion rate of the catalysts in Comparative Example 1 and various embodiments of the present invention changes with temperature during the catalytic reaction process. The ignition temperature of Embodiments 1, 2 and 3 is significantly lower than that of Comparative Example 1. Among them, Embodiment 3, which has the best performance, has a CO conversion rate of 100% at 100°C, indicating that Embodiment 3 greatly improves the CO conversion efficiency while ensuring a low NH3 generation.

Claims

1. A natural gas exhaust catalyst for vehicles, characterized in that, The catalyst includes a support and a lower catalytic coating supported on the support, and also includes an upper catalytic coating supported on the lower catalytic coating; The lower catalytic coating comprises a Pt-Pd based mixture, which includes Pt, Pd, a cerium-zirconium-praseodymium solid solution, a metal additive, and Ba, Mn, and Mg modified alumina; the content of each component in the cerium-zirconium-praseodymium solid solution is: CeO2 75~85 wt.%, ZrO2 4~6 wt.%, Pr2O3 3~8 wt.%, La2O3 3~6 wt.%, and Y2O3 3~8 wt.%; the metal additive is a Mg additive and / or a Ba additive; The upper catalytic coating comprises an Rh-based mixture or a Pt-Rh-based mixture; wherein the Rh-based mixture comprises Rh, Ba-modified alumina, and a cerium-zirconium-neodymium solid solution; the Pt-Rh-based mixture comprises Pt, Rh, a cerium-zirconium-neodymium solid solution, and Ba-modified alumina; the content of each component in the cerium-zirconium-neodymium solid solution is: CeO2 75~85 wt.%, ZrO2 3~6 wt.%, Nd2O3 3~6 wt.%, La2O3 3~8 wt.%, and Y2O3 3~8 wt.%.

2. The vehicle natural gas exhaust catalyst according to claim 1, characterized in that, It also includes at least one of the following technical features: a) The catalyst support is at least one of ceramic, metal or silicon carbide; b) The content of each component in the Pt-Pd based mixture is as follows: Pt 0.1-1 wt.%; Pd 0.1-1 wt.%; Ba, Mn, and Mg modified alumina 10-45 wt.%; cerium-zirconium-praseodymium solid solution 40-75 wt.%; metal additives 1-15 wt.%, and the sum of the contents of each component is 100%. c) The content of each component in the Rh-based mixture is as follows: Rh 0.1-1 wt.%, Ba-modified alumina 8-25 wt.%, cerium-zirconium-neodymium solid solution 70-90 wt.%, and the sum of the contents of each component is 100%. d) The content of each component in the Pt-Rh based mixture is as follows: Pt 0.1-1 wt.%, Rh 0.1-1 wt.%, Ba modified alumina 8-25 wt.%, cerium-zirconium-neodymium solid solution 70-90 wt.%, and the sum of the contents of each component is 100%. e) In the catalyst: the loading of Pt is 0.1~5 g / L, the loading of Rh is 0.1~1 g / L, and the loading of Pd is 0.1~2.5 g / L.

3. The vehicle natural gas exhaust catalyst according to claim 2, characterized in that, It also includes at least one of the following technical features: a1) The catalyst support structure is a straight-through honeycomb type, and the particle size of the catalyst support is 300-700 mesh; the wall thickness of the straight-through honeycomb type catalyst support is 3-4 mils; b1) The content of each component in the Pt-Pd based mixture is as follows: Pt 0.1-0.5 wt.%; Pd 0.1-0.5 wt.%; Ba, Mn, and Mg modified alumina 30-45 wt.%; cerium-zirconium-praseodymium solid solution 45-60 wt.%; and metal additives 5-10 wt.%, with the sum of the contents of each component being 100%. c1) The content of each component in the Rh-based mixture is as follows: Rh 0.1-0.5 wt.%, Ba-modified alumina 8-15 wt.%, cerium-zirconium-neodymium solid solution 80-90 wt.%, and the sum of the contents of each component is 100%. d1) The content of each component in the Pt-Rh based mixture is as follows: Pt 0.1-0.5 wt.%, Rh 0.1-0.5 wt.%, Ba modified alumina 8-15 wt.%, cerium-zirconium-neodymium solid solution 80-90 wt.%, and the sum of the contents of each component is 100%.

4. The vehicle natural gas exhaust catalyst according to claim 1, characterized in that, The Mg additive is a nitrate or hydroxide of Mg; the Ba additive is a sulfate or hydroxide of Ba.

5. The method for preparing a vehicle natural gas exhaust catalyst according to any one of claims 1 to 4, characterized in that, Includes the following steps: Preparation of the lower catalytic coating of the catalyst; 1) Preparation of Pd-based slurry: Add cerium-zirconium-praseodymium solid solution to water to make slurry, add metal additives and then add metal Pd solution dropwise, stir for 30-60 min; 2) Preparation of Pt-based slurry: The surface of Ba-modified alumina is pre-impregnated with Mg and Mn solutions, calcined and ground, then metal additives are added and metal Pt solution is added dropwise, and stirred for 30-60 min. 3) After mixing Pd-based slurry and Pt-based slurry, adjust the pH of the mixture to 5-6, adjust the viscosity of the mixture to 500-1000cp, adjust the solid content of the mixture to 30-40wt%, coat the mixture onto the support, and calcine to obtain a catalyst with a lower catalytic coating. Preparation of the upper catalytic coating on the catalyst, wherein the upper catalytic coating is an Rh-based slurry or a Pt-Rh-based slurry; 4) If the catalytic coating is made of Rh-based slurry, the preparation of Rh-based slurry is as follows: add Ba-modified alumina and cerium-zirconium-neodymium solid solution to water to make slurry, add metal Rh solution, and stir for 30-60 min; 5) If the catalytic coating is selected from Pt-Rh based slurry, the preparation of Pt-Rh based slurry is as follows: add Ba modified alumina and cerium-zirconium-neodymium solid solution to water to make slurry, add metal Rh solution and metal Pt solution, and stir for 30-60 min; 6) Using slurry 4) or slurry 5), the following method is adopted: adjust the pH of the slurry system to 4-5, adjust the viscosity of the mixture system to 500-1000cp, adjust the solid content of the mixture system to 30-40wt%, apply the mixture system onto the catalyst with the lower catalytic coating, and calcine to obtain the vehicle natural gas exhaust catalyst.

6. The method for preparing a natural gas exhaust catalyst for vehicles according to claim 5, characterized in that, It also includes at least one of the following technical features: 11) In step 1), the particle size D90 of the cerium-zirconium-praseodymium solid solution is 12-14 μm; 21) In step 2), the solution of Mg is Mg hydrochloride, nitrate or sulfate; the solution of Mn is Mn hydrochloride, nitrate or sulfate; 22) In step 2), the calcination temperature is 550~600℃ and the calcination time is 1~2h; grind to D90=12-14μm.

7. The method for preparing a natural gas exhaust catalyst for vehicles according to claim 5, characterized in that, It also includes at least one of the following technical features: 31) In step 3), the pH adjuster for the mixed system is ammonia. 32) In step 3), the modifier used to adjust the viscosity of the mixture is at least one of boehmite or carboxymethyl cellulose; 33) In step 3), deionized water is used to adjust the solid content of the mixture; 34) In step 3), the roasting temperature is 500~800℃ and the roasting time is 1~3h; 41) In step 4), the particle size D90 of the cerium-zirconium-neodymium solid solution is 12-14 μm; 51) In step 5), the particle size D90 of the cerium-zirconium-neodymium solid solution is 12-14 μm; 61) In step 6), the pH adjuster for adjusting the slurry system is at least one of acetic acid, citric acid, or oxalic acid; 62) In step 6), the modifier used to adjust the viscosity of the mixture is at least one of boehmite or carboxymethyl cellulose; 63) In step 6), deionized water is used to adjust the solid content of the mixture; 64) In step 6), the roasting temperature is 500~800℃ and the roasting time is 1~3h.

8. The application of the catalyst as described in any one of claims 1 to 4 in the treatment of natural gas exhaust gas from vehicles.

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