Exhaust Catalyst Structure Inhibiting Foil Elongation
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Solution Overview
Problem
Existing exhaust gas purifying catalyst structures for internal combustion engines, particularly those for motorcycles, face challenges in reducing production costs and preventing foil elongation due to the diffusion of non-Ce rare earth elements into the oxide film on the metal support.
Innovation Solution
The proposed solution involves an exhaust gas purifying catalyst structure with a catalyst layer containing a noble metal, an OSC material with cerium and a non-Ce rare earth element, and alumina, where the content of the non-Ce rare earth element is between 2.52% and 4.62% by mass in terms of an oxide. This configuration inhibits the diffusion of the non-Ce rare earth element into the oxide film, reducing foil elongation and improving structural durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst layer containing non-Ce rare earth element is formed on a metal support, then the oxygen storage capacity is improved, but the metal foil undergoes volume expansion and stretching due to diffusion of the rare earth element into the oxide film
Solution Approach 1:
The patent introduces alumina as an intermediary barrier layer between the catalyst layer containing non-Ce rare earth element and the metal support. This intermediary prevents the rare earth element from diffusing into the metal oxide film, thereby eliminating the volume expansion and stretching of the metal foil while still allowing the catalyst to perform its oxygen storage function
Solution Approach 2:
The patent segments the catalyst layer into distinct functional zones: an alumina-containing layer that acts as a diffusion barrier, and a catalyst layer containing the non-Ce rare earth element for oxygen storage. This segmentation allows each layer to perform its specific function independently - the alumina layer prevents diffusion while the catalyst layer maintains oxygen storage capacity
2Ease of manufacture
If a catalyst layer containing both Pd and Rh is formed in one step, then the production cost is reduced, but the active sites decrease due to growth of noble metal particles caused by temperature fluctuations
Solution Approach 1:
The patent applies local quality by providing different support materials for different noble metals within the same catalyst layer. Pd is supported on alumina which provides stability against particle growth, while Rh is supported on the OSC material which enhances its reduction activity. This localized differentiation allows both metals to maintain their optimal properties despite being formed in a single step
Solution Approach 2:
The patent uses a composite catalyst layer structure where alumina and OSC material are combined as support materials for different noble metals. This composite approach allows the system to achieve both cost-effectiveness (single-step formation) and high catalytic activity (prevented particle growth) by leveraging the complementary properties of different materials in specific locations
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
The catalyst structure maintains effective oxygen absorption and release capabilities while preventing foil elongation and improving structural durability, thus reducing production costs and maintaining high purifying performance.
Implementation Method 1
maintains an effective oxygen absorption and release capability
Implementation Method 2
the non-Ce rare earth element contained in the catalyst layer readily diffuses into the oxide film formed on the surface of the metal foil and undergoes solid dissolution
Implementation Method 3
the oxide film undergoes volume expansion when exposed to an elevated temperature due to the fluctuation of driving conditions of an automobile
Data Source
AI summary
Provided are an exhaust gas purifying catalyst structure that inhibits foil elongation and improves structural durability and a production method therefor. The exhaust gas purifying catalyst structure has a metal support configured by using an mantle and a metal foil provided in the mantle and forming an exhaust gas flow path, and a catalyst layer provided on a surface forming the flow path of the metal foil, wherein the catalyst layer contains a noble metal, an OSC material containing cerium and a rare earth element other than cerium (non-Ce rare earth element), and alumina, and a content of the non-Ce rare earth element with respect to 100% by mass of the catalyst layer is 2.52% by mass or more and 4.62% by mass or less in terms of an oxide.