Layered Exhaust Gas Catalyst for Variable Engine Operation
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Solution Overview
Problem
Exhaust gas purification catalysts designed for specific operation states of internal combustion engines fail to maintain effective purification performance when the engine's operation conditions change, leading to increased emissions of harmful components.
Innovation Solution
The catalyst features a stacked structure with four distinct catalyst layers, each optimized for different operation states, utilizing varying concentrations of CeO2 and catalytic metals like Pd and Rh, and a support material with controlled particle diameters to adapt to varying exhaust gas conditions, ensuring consistent purification performance across different engine operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst is designed with a focus on a specific operation state (e.g., warm-up operation), then the purification performance for that specific state is improved, but the purification performance deteriorates when the operation state changes
Solution Approach 1:
The catalyst layer is divided into multiple segments along the exhaust flow direction, with each segment containing catalyst particles of different average diameters. The upstream segment has smaller average diameter for efficient cold-start purification, while downstream segments have progressively larger average diameters for stable performance during normal operation. This segmentation allows the catalyst to handle different operation states effectively without compromising overall purification performance.
Solution Approach 2:
Different regions of the catalyst layer are given different local properties by controlling the spatial distribution of catalyst particle sizes. The upstream region (closer to engine) contains finer particles optimized for cold-start conditions, while downstream regions contain coarser particles for normal operation stability. This local quality variation resolves the contradiction between optimized specific-state performance and adaptability to state changes.
2Reliability
If smaller catalyst particles are used, then the purification ability during warm-up operation is improved, but the purification stability during normal operation deteriorates
Solution Approach 1:
The catalyst layer is segmented into multiple zones with different particle size characteristics. The upstream zone contains smaller particles (0.5-5 μm) that provide high surface area and excellent cold-start purification ability. The downstream zones contain progressively larger particles (5-20 μm) that provide structural stability and consistent performance during normal operation. This segmentation resolves the trade-off between warm-up efficiency and normal operation stability.
Solution Approach 2:
The average particle diameter parameter is varied spatially across the catalyst layer thickness. By changing this critical parameter from small (upstream) to large (downstream), the catalyst achieves both high reactivity for cold-start and stable performance for normal operation, resolving the contradiction between these two operational requirements.
3Stability of the object's composition
If larger catalyst particles are used, then the purification stability during normal operation is improved, but the purification ability during warm-up operation deteriorates
Solution Approach 1:
Rather than using uniformly large particles throughout, the catalyst layer is segmented with large particles concentrated in downstream regions and small particles in upstream regions. This spatial segmentation allows large particles to provide stability during normal operation where they are most needed, while small particles in the upstream zone ensure effective warm-up purification.
Solution Approach 2:
The catalyst layer exhibits local quality variation in particle size distribution. Downstream regions have larger particle sizes optimized for stable normal operation, while upstream regions have smaller particle sizes optimized for warm-up purification. This local differentiation resolves the contradiction between stability and warm-up ability.
4Productivity
If the catalyst layer is made denser, then the purification efficiency is improved, but the exhaust gas flow resistance increases
Solution Approach 1:
The catalyst layer uses a controlled gradient in particle size distribution, with smaller particles upstream and progressively larger particles downstream. This parameter variation optimizes the balance between density (for efficiency) and porosity (for flow resistance). The smaller upstream particles provide high surface area for efficient purification, while larger downstream particles maintain adequate porosity to limit pressure drop, resolving the contradiction between efficiency and flow resistance.
Solution Approach 2:
The catalyst layer is designed as a porous structure with controlled void spaces between particles. The gradual increase in particle size from upstream to downstream creates an optimized pore size distribution that maintains sufficient porosity for gas flow while providing adequate surface area for purification reactions, thus resolving the efficiency-flow resistance trade-off.
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 effectively reduces emissions of harmful components by optimizing catalyst layers for warm-up, high-velocity, and fluctuating air-fuel ratio conditions, enhancing recovery and purification efficiency.
Implementation Method 1
CeO2 stores oxygen while exhaust gas in a lean state (excessive oxygen) is being supplied, and releases oxygen when exhaust gas in a rich state (insufficient oxygen) is being supplied
Implementation Method 2
The catalytic metal is a precious metal material that promotes the oxidation (or reduction) of the harmful components
Implementation Method 3
a support material that supports the catalytic material... The support material contained in the upper catalyst layer has a volume-based average particle diameter D50CD of 2 μm or more and 5 μm or less
Data Source
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AI summary
An exhaust gas purification catalyst disclosed herein includes: a substrate 10 that has a plurality of cells 12 and a partition wall 14 separating the plurality of cells 12; and a catalyst layer 20 provided on the surface of the partition wall 14. The catalyst layer 20 includes a lower catalyst layer 22 and an upper catalyst layer 24. A lower-layer front portion A containing Pd is provided on the upstream side of the lower catalyst layer 22, and a lower-layer rear portion B containing at least one among Pd and Pt is provided on the downstream side. Further, an upper-layer front portion C containing Rh is provided on the upstream side of the upper catalyst layer 24, and an upper-layer rear portion D containing Rh is provided on the downstream side. The lower-layer front portion A, the lower-layer rear portion B, the upper-layer front portion C, and the upper-layer rear portion D each have CeO2 content individually set. As a result, it is possible to provide an exhaust gas purification catalyst that can exhibit adequate purification performance according to an operation state of an internal combustion engine.