Two-Layer Catalyst Structure for Exhaust Purification
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Solution Overview
Problem
Conventional exhaust gas purification systems for straddled vehicles face challenges in achieving both high peel resistance and purification performance, especially under severe vibratory conditions due to differences in thermal expansion coefficients between metallic supports and catalyst layers.
Innovation Solution
The implementation of a stainless steel support with a high ceria content layer and a low ceria content layer, where the high ceria content layer is between the low ceria content layer and the stainless steel support, enhancing adhesiveness and containing noble metals for balanced oxidation and reduction reactions, and a ceria-zirconia solid solution doped with rare earth elements to improve adhesion and prevent sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallic support with a catalyst layer is used, then purification performance is achieved, but the catalyst layer is likely to be peeled off due to thermal expansion differences
Solution Approach 1:
The catalyst layer is divided into two distinct layers: a first catalyst layer containing a three-way catalyst and a second catalyst layer containing a noble metal catalyst. This segmentation allows each layer to perform specific functions while improving overall adhesion to the metallic support, thereby resolving the contradiction between purification performance and peel resistance.
Solution Approach 2:
The invention uses a composite structure combining two different catalyst layers with distinct compositions and functions. The first layer uses a three-way catalyst for comprehensive purification, while the second layer uses a noble metal catalyst for enhanced adhesion and specific catalytic activities, achieving both high peel resistance and purification performance through material composition optimization.
2Reliability
If the catalyst layer is made thick to improve purification performance, then purification efficiency increases, but peel resistance decreases due to thermal expansion stress
Solution Approach 1:
Instead of using a single thick catalyst layer, the invention segments the catalytic function into two thinner layers. The first layer provides the primary purification function, while the second layer enhances adhesion. This segmentation reduces thermal expansion stress within each layer while maintaining overall purification efficiency, resolving the contradiction between purification performance and peel resistance.
3Device complexity
If a single catalyst layer is used to simplify the structure, then device complexity is reduced, but both peel resistance and purification performance cannot be achieved at a high level
Solution Approach 1:
The invention applies local quality by giving each catalyst layer distinct compositions and functions tailored to specific requirements. The first layer is optimized for comprehensive pollutant purification using a three-way catalyst, while the second layer is optimized for adhesion and specific catalytic activities using a noble metal catalyst. This localized optimization allows both peel resistance and purification performance to be achieved at high levels without excessive complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly enhances both peel resistance and purification performance by promoting balanced reactions and improving adhesiveness, thereby preventing catalyst peeling and ensuring effective exhaust gas purification.
Implementation Method 1
a first ceria content layer containing ceria and at least one type of noble metal selected from the group consisting of Pt, Pd, Ir, Ru, and Os; and a second layer containing at least one type of noble metal selected from the group consisting of Rh, Ir, Ru, Pt, Pd, Au, Ag, and Os, the second layer having a ceria content lower than a ceria content in the high ceria content layer or having a ceria content of 0 wt%, the first ceria content layer being provided between the second layer and the stainless steel support so as to be in contact with the second layer and the stainless steel support
Implementation Method 2
a ceria-zirconia solid solution doped with rare earth elements to improve adhesion and prevent sintering
Implementation Method 3
a first ceria content layer containing ceria and at least one type of noble metal selected from the group consisting of Pt, Pd, Ir, Ru, and Os
Implementation Method 4
a second layer containing at least one type of noble metal selected from the group consisting of Rh, Ir, Ru, Pt, Pd, Au, Ag, and Os
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3
AI summary
An object of the present teaching is to achieve both a peel resistance and purification performance at a higher level. An exhaust gas purification system of a gasoline-fueled engine includes: a stainless steel support made of stainless steel; a high ceria content layer containing ceria and at least one type of noble metal selected from the group consisting of Pt, Pd, Ir, Ru, and Os; and a low ceria content layer containing ceria and at least one type of noble metal selected from the group consisting of Rh, Ir, Ru, Pt, Pd, Au, Ag, and Os, the low ceria content layer having a ceria content lower than a ceria content in the high ceria content layer, the high ceria content layer being provided between the low ceria content layer and the stainless steel support so as to be in contact with the low ceria content layer and the stainless steel support.