Layered Exhaust Gas Catalyst Layout for Multi-State Purification
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Solution Overview
Problem
Existing exhaust gas purification catalysts struggle to maintain high purification performance across various operation states of internal combustion engines, such as warm-up, high-speed, and normal operations, leading to increased emissions of harmful components when engine conditions change.
Innovation Solution
The catalyst features a cylindrical substrate with a stacked structure of catalyst layers, including lower and upper layers with specific compositions and positions of catalytic metals (Pd, Pt, Rh) and an OSC material (CeO2) to optimize purification performance in different engine states, preventing cell clogging and enhancing catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single catalyst layer composition is used, then the device complexity is reduced, but the purification performance cannot be maintained across various operation states
Solution Approach 1:
The catalyst layer is segmented into multiple sub-layers (first through fourth catalyst layers) with different compositions and functions. Each layer targets specific operation states: the first layer handles warm-up operation, the second layer handles high-speed operation, and the third and fourth layers handle normal operation. This segmentation allows the catalyst to adapt to various operation states without requiring a completely complex multi-component system.
Solution Approach 2:
Different regions of the catalyst layer are assigned different compositions and functions tailored to local requirements. The first catalyst layer contains Pd for warm-up operation, the second layer contains Pt for high-speed operation, while the third and fourth layers contain Rh for normal operation. This local differentiation of quality enables high purification performance across all operation states while maintaining a manageable overall structure.
2Reliability
If catalyst layers are stacked with overlapping lap portions, then the catalytic activity is enhanced, but cell clogging occurs and flow resistance increases
Solution Approach 1:
The lap portions of adjacent catalyst layers are positioned at different axial locations along the substrate. The first catalyst layer's lap portion is positioned at a first axial location, while the second catalyst layer's lap portion is positioned at a second axial location that does not overlap with the first. This spatial arrangement in the axial dimension maintains high catalytic activity through overlapping structures while preventing cell clogging by distributing the lap portions across different locations.
3Productivity
If the catalyst layer is designed for specific operation states, then the purification performance is optimized for those states, but the emission increases when engine operation changes
Solution Approach 1:
The catalyst layer structure is designed to perform multiple functions simultaneously by incorporating four distinct catalyst layers, each optimized for specific operation states. The first layer (Pd) handles warm-up, the second layer (Pt) handles high-speed operation, the third layer (Rh) and fourth layer (Rh) handle normal operation. This multi-functional design enables the catalyst to maintain high purification performance across all operation states without increasing emissions when engine conditions change.
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 achieves improved purification performance across varying engine conditions by utilizing Pd for warm-up, Rh for NOX purification, and CeO2 for oxygen storage, reducing emissions and maintaining stability despite fluctuations in air-fuel ratio and temperature.
Implementation Method 1
The catalytic metal is a precious metal material that promotes the oxidation (or reduction) of the harmful components
Implementation Method 2
The catalytic metal is a precious metal material that promotes the oxidation (or reduction) of the harmful components
Implementation Method 3
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 4
the water-gas shift reaction shown in formula (1) occurs and hydrogen gas (H2) is generated. This hydrogen gas is then used as a reducing agent in the NOx purification reaction
Data Source
Figure 1~2
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AI summary
An exhaust gas purification catalyst disclosed herein includes a catalyst layer 20 including a lower catalyst layer 22 and an upper catalyst layer 24. A lower-layer front portion A is provided on the upstream side of the lower catalyst layer 22, and a lower-layer rear portion B is provided on the downstream side of the lower catalyst layer 22. Further, an upper-layer front portion C is provided on the upstream side of the upper catalyst layer 24, and an upper-layer rear portion D is provided on the downstream side of the upper catalyst layer 24. 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 individually set types of catalyst metal. As a result, it is possible to exhibit adequate purification performance according to an operation state of an internal combustion engine. Furthermore, from the viewpoint of achieving both exhaust gas purification performance and suppression of pressure loss, a lower-layer lap portion 25 and an upper-layer lap portion 27 are formed so as not to overlap in the cylinder axis direction X. This makes it possible to provide an exhaust gas purification catalyst that can exhibit adequate purification performance according to an operation state of the internal combustion engine.