Exhaust Gas Catalyst Core-Shell Oxide Structure
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Solution Overview
Problem
Current exhaust gas-purifying catalysts, despite incorporating cerium oxide for enhanced oxygen storage, still fall short in achieving optimal purification performance for hydrocarbons, carbon monoxide, and nitrogen oxides, necessitating further improvements in catalyst design and composition.
Innovation Solution
The development of an exhaust gas-purifying catalyst comprising a first oxide particle with oxygen storage capacity, partially or entirely covered by smaller second oxide particles with lower oxygen storage capacity, where precious metal particles are supported on the second oxide particles, optimizing the surface coverage and particle diameters to enhance durability and catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cerium oxide is used to enhance oxygen storage capacity, then exhaust gas-purifying performance is improved, but catalyst durability and resistance to sintering deteriorate
Solution Approach 1:
The catalyst structure is segmented into two distinct oxide components: a first oxide (e.g., cerium oxide) providing oxygen storage capacity, and a second oxide covering the surface to protect precious metals. This segmentation allows each component to specialize in one function, resolving the contradiction between oxygen storage and durability.
Solution Approach 2:
The invention uses a composite oxide structure where a first oxide particle with high oxygen storage capacity is partially or entirely covered by a second oxide with lower oxygen storage capacity. This composite structure combines the oxygen storage benefit of cerium oxide with the protective effect of the second oxide, maintaining both performance and durability.
2Productivity
If precious metal particles are supported on oxide surfaces to enhance catalytic activity, then exhaust gas purification efficiency is improved, but sintering and aggregation of precious metal particles occur leading to performance degradation
Solution Approach 1:
The second oxide acts as an intermediary layer between the precious metal particles and the first oxide support. It provides a protective interface that prevents direct contact and sintering of precious metal particles while still allowing catalytic function, thus resolving the contradiction between activity and resistance to sintering.
Solution Approach 2:
The second oxide is applied locally on the surface of the first oxide particle, creating a zone of protection specifically where precious metals are supported. This local quality approach ensures catalytic activity is maintained at the interface while protecting against sintering in the supported metal regions.
3Quantity of substance
If high oxygen storage capacity materials are used, then oxygen availability for purification reactions is improved, but control over oxygen release becomes less precise
Solution Approach 1:
The catalyst structure creates local quality differentiation: the first oxide provides bulk oxygen storage capacity, while the second oxide layer on the surface provides controlled oxygen release. This allows the system to have both high oxygen availability and precise control over when and how oxygen is released to the exhaust gas.
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 improves the exhaust gas-purifying performance by maintaining catalytic activity over time, preventing sintering and aggregation of precious metal particles, and ensuring effective oxygen storage and utilization, leading to enhanced HC, CO, and NOX purification efficiency.
Implementation Method 1
a first oxide particle with an oxygen storage capacity
Implementation Method 2
one or more second oxide particles partially or entirely covering a surface of the first oxide particle
Implementation Method 3
precious metal particles supported on at least one of the second oxide particles
Data Source
Figure 1
Figure 2~3
AI summary
An exhaust gas-purifying catalyst 1 which offers high exhaust gas purification performance is achieved. The exhaust gas-purifying catalyst 1 includes a first oxide particle 10 with an oxygen storage capacity, one or more second oxide particles 20 partially or entirely covering a surface of the first oxide particle 10 and having an oxygen storage capacity lower than that of the first oxide particle 10, an average particle diameter Dav of the one or more second oxide particles 20 being smaller than that of the first oxide particle 10, and precious metal particles 30 supported on at least one of the second oxide particles 20.