A low rh type motorcycle three-way catalyst and a preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU JINSHENG MOTORCYCLE PARTS CO LTD
- Filing Date
- 2024-01-17
- Publication Date
- 2026-05-29
Smart Images
Figure CN117899925B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of motorcycle exhaust gas treatment technology, specifically a low-rhodium type three-way catalytic catalyst for motorcycles and its preparation method. Background Technology
[0002] A three-way catalytic converter is the most important external purification device installed in a motorcycle's exhaust system. It converts harmful gases such as CO, HC, and NOx emitted from motorcycle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. When the high-temperature motorcycle exhaust passes through the purification device, the precious metals platinum, palladium, and rhodium in the three-way catalytic converter enhance the activity of CO, HC, and NOx, promoting certain oxidation-reduction chemical reactions. CO is oxidized at high temperatures into colorless and non-toxic carbon dioxide; HC compounds are oxidized at high temperatures into water (H2O) and carbon dioxide; and NOx is reduced into nitrogen and oxygen. These three harmful gases are transformed into harmless gases, thus purifying the exhaust.
[0003] Due to increasingly stringent emission standards, traditional ternary catalysts inevitably require the use of more precious metals. Rhodium is indispensable due to the working principle of ternary catalysts, and its price is relatively expensive, resulting in high catalyst costs. Therefore, there is an urgent need to develop low-rhodium ternary catalysts for motorcycles.
[0004] In view of this, a low-rhodium type three-way catalytic catalyst for motorcycles and its preparation method are proposed. Summary of the Invention
[0005] The purpose of this invention is to provide a low-rhodium three-way catalytic catalyst for motorcycles and its preparation method in order to solve the problems mentioned above.
[0006] The technical solution adopted in this invention is as follows:
[0007] In a first aspect, a low-rhodium type three-way catalytic converter for motorcycles includes a coating substrate, the outer surface of which is coated sequentially in layers to form an inner coating and an outer coating; the inner coating includes a noble metal, a molecular sieve, an alumina-based material, and a modified CeO2-ZrO2 composite oxide; the outer coating includes a noble metal, an alumina-based material, and a modified CeO2-ZrO2 composite oxide; wherein the noble metal of the outer coating includes ruthenium and rhodium, and the noble metal of the inner coating includes platinum and palladium, the precursors of platinum and palladium being Pt(NO3)2 and Pd(NO3)2, respectively; and the precursors of ruthenium and rhodium being Ru(NO3)3 and Rh(NO3)3, respectively.
[0008] In a preferred embodiment, the molecular sieve is one or more of beta molecular sieve, MFI molecular sieve and SSZ molecular sieve, the silica-alumina ratio of the molecular sieve is 10-80, the molecular sieve is blank or transition metal modified molecular sieve, and the transition metal is one or more of Cu, Fe and Mn.
[0009] In a preferred embodiment, the alumina base of the inner coating is pure alumina and / or lanthanum-modified alumina, wherein the lanthanum modification amount is 1~8wt%; the alumina base of the outer coating is one or more of pure alumina, lanthanum-modified alumina, and zirconium-modified aluminum oxide, wherein the lanthanum modification amount is 1~8wt% and the zirconium modification amount is 1~20wt%.
[0010] In a preferred embodiment, the coating substrate is one of a cordierite ceramic carrier, a metal carrier, and a silicon carbide carrier.
[0011] A second aspect of the present invention provides a method for preparing a low-rhodium type three-way catalytic catalyst for motorcycles, comprising the following steps:
[0012] Step S1: Alumina-based, modified CeO2-ZrO2 composite oxide, precious metal, molecular sieve and dispersant are mixed with water in sequence to obtain inner layer slurry;
[0013] Step S2: Mix alumina-based materials, modified CeO2-ZrO2 composite oxides, precious metals, and dispersants with water to obtain an outer slurry;
[0014] Step S3: Apply the inner layer slurry to both ends of the coating substrate using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the inner coating.
[0015] Step S4: Apply the outer layer slurry to both ends of the inner coating using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the outer coating and form a low-rhodium three-way catalytic catalyst.
[0016] In a preferred embodiment, the calcining furnace is provided with four temperature ranges: 150±15℃, 310±15℃, 470±20℃, and 550-600℃, and the water is deionized water.
[0017] In a preferred embodiment, the dispersant is Natrosol and PEG.
[0018] In a preferred embodiment, the component percentages of the inner layer slurry are:
[0019] Alumina-based content is 25%-50%;
[0020] The modified CeO2-ZrO2 composite oxide content is 27%-64%;
[0021] Molecular sieve content is 5%-25%;
[0022] Platinum content is 0.01-1%;
[0023] Palladium content is 0.5%-1%.
[0024] In a preferred embodiment, the component percentages of the outer slurry are:
[0025] Alumina-based content is 25%-50%;
[0026] The modified CeO2-ZrO2 composite oxide content is 27%-63%;
[0027] Ruthenium is 0.01%-5%;
[0028] The rhodium content is 0.01%-0.5%.
[0029] In summary, due to the adoption of the above technical solutions, the beneficial effects of this invention are as follows: Through extensive experiments and tests, it was found that using ruthenium, which is cheaper than the precious metal rhodium, for partial replacement can reduce costs while still achieving the desired pollutant conversion effect; at the same time, by combining supported Pt-Pd molecular sieves and using the HC-SCR reaction pathway with oxygen content at the stoichiometric air-fuel ratio, the conversion efficiency of the catalyst is improved when the oxygen content in the exhaust gas is higher than the stoichiometric air-fuel ratio, thereby achieving the development of a low-rhodium motorcycle catalyst. Attached Figure Description
[0030] Figure 1 This is a simplified schematic diagram of the layered structure of the present invention.
[0031] In the diagram, the markings are: 101 - coating substrate, 102 - inner coating, and 103 - outer coating. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0033] Reference Figure 1A low-rhodium three-way catalytic converter for motorcycles includes a coating substrate 101. The outer surface of the coating substrate 101 is coated in layers to form an inner coating 102 and an outer coating 103. The outer coating 103 includes a noble metal, an alumina-based material, and a modified CeO2-ZrO2 composite oxide. The noble metal in the outer coating 103 includes ruthenium and rhodium, and the precursors of ruthenium and rhodium are Ru(NO3)3 and Rh(NO3)3, respectively. When the oxygen content in the exhaust gas is lower than the theoretical air-fuel ratio, the three-way catalytic converter can efficiently eliminate nitrogen oxides under the action of ruthenium and rhodium in the outer coating 103. By using ruthenium, which is cheaper than the noble metal rhodium, as a partial substitute, the conversion efficiency of pollutants can be met while also reducing costs.
[0034] In this embodiment, the inner coating 102 includes noble metals, molecular sieves, alumina-based materials, and modified CeO2-ZrO2 composite oxides. The noble metals in the inner coating 102 include platinum and palladium, with Pt(NO3)2 and Pd(NO3)2 as precursors, respectively. The molecular sieves are one or more of beta molecular sieves, MFI molecular sieves, and SSZ molecular sieves. The inner coating 102 loads platinum and palladium onto the molecular sieves, forming a supported Pt-Pd molecular sieve. Through the HC-SCR reaction pathway with oxygen content higher than the stoichiometric air-fuel ratio, the conversion efficiency of the catalyst can be improved, thereby efficiently eliminating pollutants.
[0035] Meanwhile, alumina-based and modified CeO2-ZrO2 composite oxides form a solid solution in the coating substrate 101, and CeO2 and ZrO2 undergo heterogeneous in-situ nucleation, with different grain structures encapsulating or interpenetrating each other to construct a heterogeneous phase interface. By controlling the nucleation and growth of grains and the heterogeneous interface to increase the sintering energy barrier, the thermal stability of the ternary catalyst is significantly improved.
[0036] The preferred molecular sieve is an MFI molecular sieve with a silica-to-alumina ratio of 10 to 80. The molecular sieve can be a blank or a transition metal modified molecular sieve, with the transition metal being one or more of Cu, Fe, and Mn. The preferred molecular sieve is a transition metal modified molecular sieve. When the molecular sieve is modified with a transition metal, it can ensure low, medium, and high temperature catalytic performance. After loading Pt-Pd, it can ensure the conversion effect of pollutants under different temperature conditions.
[0037] In this embodiment, the alumina-based 102 of the inner coating is pure alumina and / or lanthanum-modified alumina, with a lanthanum modification amount of 1~8wt%. Preferably, the alumina-based 102 has a lanthanum modification amount of 1~8wt%. The lanthanum-modified alumina material has a large specific surface area and pore volume, thereby improving the adsorption and catalytic effect on pollutants.
[0038] Meanwhile, the alumina base of the outer coating 103 is one or more of pure alumina, lanthanum-modified alumina, and zirconium-modified aluminum oxide, with a lanthanum modification amount of 1~8wt% and a zirconium modification amount of 1~20wt%. The alumina base of the outer coating 103 is preferably lanthanum-modified alumina.
[0039] In this embodiment, the coating substrate 101 is one of cordierite ceramic carrier, metal carrier and silicon carbide carrier, and the coating carrier 101 is preferably cordierite ceramic carrier.
[0040] This invention also provides a method for preparing a low-rhodium type three-way catalytic catalyst for motorcycles, comprising the following steps:
[0041] Step S1: Alumina-based, modified CeO2ZrO2 composite oxide, precious metal, molecular sieve and dispersant are mixed with water in sequence to obtain inner layer slurry;
[0042] Step S2: Mix alumina-based materials, modified CeO2-ZrO2 composite oxides, precious metals, and dispersants with water to obtain an outer slurry;
[0043] Step S3: Apply the inner layer slurry to both ends of the coating substrate using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the inner coating.
[0044] Step S4: Apply the outer layer slurry to both ends of the inner coating using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the outer coating and form a low-rhodium three-way catalytic catalyst.
[0045] In this embodiment, the calcination furnace is set with four temperature ranges: 150±15℃, 310±15℃, 470±20℃, and 550-600℃. Each of the four temperature ranges is calcined for 2 to 4 hours, and the temperature is gradually increased from low to high. After calcination, the carrier morphology is formed on the one hand, and an active phase with a certain crystal structure is formed on the other hand. Sometimes the active phase will also interact with the carrier, such as by covering or forming a solid solution. The resulting three-way catalytic catalyst will be more stable, ensuring the subsequent catalytic and purification effect on pollutants.
[0046] In this embodiment, the water is deionized water, which removes ionic impurities from the water, making the water purer and ensuring that the mixed slurry does not contain unwanted impurities that would affect the subsequent purification effect.
[0047] In this embodiment, the dispersants are Natrosol and PEG. The crown ether cavities formed by Natrosol and PEG can coordinate with noble metal ions, thereby improving their dispersion performance, effectively reducing the onset temperature of the three-way catalyst, and improving the catalytic effect.
[0048] In this embodiment, the coating height of both the inner and outer slurries is 50% ± 5%, and the drying temperature in the dryer is 110℃ ± 10℃.
[0049] In this embodiment, the component percentages of the inner layer slurry are as follows: alumina-based 25%-50%; modified CeO2-ZrO2 composite oxide 27%-64%; molecular sieve 5%-25%; platinum 0.01-1%; and palladium 0.5%-1%. First, deionized water is added and stirred. Then, the alumina-based and modified CeO2-ZrO2 composite oxides are added to deionized water and stirred for at least 30 minutes. Next, the precursors of platinum and palladium and the molecular sieve are added and stirred for at least 1 hour. The pH is adjusted to 3-6. Then, PEG is added and stirred for at least 30 minutes. Finally, Natrosol is added and stirred for at least 4 hours to form the slurry.
[0050] In this embodiment, the component percentages of the outer layer slurry are as follows: alumina-based 25%-50%; modified CeO2-ZrO2 composite oxide 27%-63%; ruthenium 0.01%-5%; and rhodium 0.01%-0.5%. First, deionized water is added and stirred. Then, the alumina-based slurry and modified CeO2-ZrO2 composite oxide are added to deionized water and stirred for at least 30 minutes. Next, the ruthenium precursor is added and stirred for 10 minutes, followed by the addition of rhodium and stirring for at least 1 hour, adjusting the pH to 3-6. Then, PEG is added and stirred for at least 30 minutes. Finally, Natrosol is added and stirred for at least 4 hours to form the outer layer slurry.
[0051] In summary, by using ruthenium, which is cheaper than the precious metal rhodium, as a partial substitute, and combining it with supported Pt-Pd molecular sieves, the conversion efficiency of the catalyst is improved when the oxygen content in the exhaust gas is higher than the theoretical air-fuel ratio through the HC-SCR reaction pathway with oxygen content at the theoretical air-fuel ratio. It can also meet the catalytic performance requirements at low, medium and high temperatures, thereby reducing costs while satisfying the pollutant conversion effect.
[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A low-rhodium type three-way catalytic converter for motorcycles, characterized in that, It includes a coating substrate, the outer surface of which is coated with an inner coating and an outer coating in a layered manner; The inner coating comprises noble metals, molecular sieves, alumina-based materials, and modified CeO2-ZrO2 composite oxides; The outer coating comprises noble metals, alumina-based materials, and modified CeO2-ZrO2 composite oxides; wherein the noble metals in the outer coating include ruthenium and rhodium. The noble metals in the inner coating include platinum and palladium, with the precursors of platinum and palladium being Pt(NO3)2 and Pd(NO3)2, respectively; and the precursors of ruthenium and rhodium being Ru(NO3)3 and Rh(NO3)3, respectively.
2. The low-rhodium type three-way catalytic converter for motorcycles as described in claim 1, characterized in that: The molecular sieve is one or more of beta molecular sieve, MFI molecular sieve and SSZ molecular sieve, the silica-alumina ratio of the molecular sieve is 10~80, the molecular sieve is blank or transition metal modified molecular sieve, and the transition metal is one or more of Cu, Fe and Mn.
3. The low-rhodium type three-way catalytic converter for motorcycles as described in claim 1, characterized in that: The alumina base of the inner coating is pure alumina and / or lanthanum-modified alumina, wherein the lanthanum modification amount is 1~8wt%; the alumina base of the outer coating is one or more of pure alumina, lanthanum-modified alumina and zirconium-modified aluminum oxide, wherein the lanthanum modification amount is 1~8wt% and the zirconium modification amount is 1~20wt%.
4. The low-rhodium type three-way catalytic converter for motorcycles as described in claim 1, characterized in that: The coating substrate is one of cordierite ceramic carrier, metal carrier, and silicon carbide carrier.
5. The method for preparing the low-rhodium type three-way catalytic catalyst for motorcycles according to any one of claims 1-4, characterized in that, Includes the following steps: Step S1: Alumina-based, modified CeO2-ZrO2 composite oxide, precious metal, molecular sieve and dispersant are mixed with water in sequence to obtain inner layer slurry; Step S2: Mix alumina-based materials, modified CeO2-ZrO2 composite oxides, precious metals, and dispersants with water to obtain an outer slurry; Step S3: Apply the inner layer slurry to both ends of the coating substrate using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the inner coating. Step S4: Apply the outer layer slurry to both ends of the inner coating using a coating machine, dry it using a dryer, and then calcine it at high temperature in a calcining furnace to obtain the outer coating and form a low-rhodium three-way catalytic catalyst.
6. The method for preparing a low-rhodium type three-way catalytic catalyst for motorcycles as described in claim 5, characterized in that, The calcining furnace is equipped with four temperature ranges: 150±15℃, 310±15℃, 470±20℃, and 550-600℃. The water used is deionized water.
7. The method for preparing a low-rhodium type three-way catalytic catalyst for motorcycles as described in claim 5, characterized in that, The dispersant is Natrosol and PEG.
8. The method for preparing a low-rhodium type three-way catalytic converter for motorcycles as described in claim 5, characterized in that, The component percentages of the inner layer slurry are as follows: Alumina-based content is 25%-50%; The modified CeO2-ZrO2 composite oxide content is 27%-64%; Molecular sieve content is 5%-25%; Platinum content is 0.01-1%; Palladium content is 0.5%-1%.
9. The method for preparing a low-rhodium type three-way catalytic converter for motorcycles as described in claim 5, characterized in that, The component percentages of the outer slurry are as follows: Alumina-based content is 25%-50%; The modified CeO2-ZrO2 composite oxide content is 27%-63%; Ruthenium is 0.01%-5%; The rhodium content is 0.01%-0.5%.