Multi-layer Three-way Catalyst for Thermal Stability
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Solution Overview
Problem
Current three-way-conversion (TWC) catalysts face challenges in maintaining performance and reducing thermal degradation, especially under high load/high speed conditions, leading to rapid loss of activity and increased thermal degradation, which affects their ability to efficiently oxidize hydrocarbons and reduce nitrogen oxides.
Innovation Solution
The implementation of a TWC catalyst system with a front and rear brick or zone configuration, where the rear brick has a catalytic layer with less than 1% oxygen storage component (OSC) by weight, and both bricks have specific PGM distributions, including palladium in the front layers and rhodium in the rear layers, optimized for maximum performance and reduced thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high PGM loading is used to improve emission reduction performance, then catalytic activity is improved, but thermal degradation and sintering occur more rapidly under high load/high speed conditions
Solution Approach 1:
The catalyst is divided into multiple washcoat layers with different PGM compositions and functions. The first washcoat layer contains Pd and Rh for oxidation, while the second washcoat layer contains Rh for reduction. This segmentation allows each layer to be optimized for its specific function, reducing the need for high overall PGM loading while maintaining performance and thermal stability.
Solution Approach 2:
Different regions of the catalyst have different PGM compositions tailored to their specific functions. The first washcoat layer near the inlet has higher Pd and Rh loading optimized for oxidation of CO and HC, while the second washcoat layer has higher Rh loading optimized for NOx reduction. This local optimization ensures high performance without requiring uniformly high PGM loading throughout, thereby reducing thermal degradation.
2Loss of time
If catalysts are located close to the manifold in CC position to reduce heating time, then rapid heat up is achieved, but thermal degradation and loss of activity increase under high load/high speed conditions
Solution Approach 1:
The catalyst structure is segmented into multiple washcoat layers with different thermal stabilities and PGM compositions. The first washcoat layer uses Pd and Rh which are more resistant to thermal degradation, while the second layer uses Rh which is optimized for NOx reduction. This segmentation allows the catalyst to maintain high activity close to the manifold while the specific layer composition reduces thermal degradation rates.
Solution Approach 2:
The catalyst composition parameters are changed by using specific PGM combinations (Pd and Rh in the first layer, Rh in the second layer) and controlling their distributions. This parameter optimization allows the catalyst to achieve rapid heat up due to its location close to the manifold while the specific compositional parameters reduce thermal degradation and maintain activity under high load/high speed conditions.
3Device complexity
If single-layer catalyst configuration is used to simplify design, then manufacturing is easier, but emission reduction performance across all pollutants is insufficient
Solution Approach 1:
The catalyst is segmented into two distinct washcoat layers: a first washcoat layer containing Pd and Rh for oxidation functions, and a second washcoat layer containing Rh for reduction functions. This segmentation enables the catalyst to simultaneously address multiple emission pollutants (CO, HC oxidation and NOx reduction) with higher effectiveness than a single-layer design, while maintaining reasonable manufacturing complexity through a systematic layering approach.
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 the catalyst's performance in oxidizing hydrocarbons and reducing nitrogen oxides, providing unexpected performance benefits and slowing down deactivation, even at high temperatures, thus meeting stringent emission standards with reduced PGM loading.
Implementation Method 1
catalytic layers relative to each other and their use in emission control systems... oxidize the carbon monoxide and the hydrocarbons
Implementation Method 2
reduce the nitrogen oxides
Data Source
Figure 1a~1d
Figure 1e~2b
Figure 3~4b
AI summary
Disclosed herein is a layered, three-way conversion catalyst having the capability of simultaneously catalyzing the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides being separated in a front and rear portion is disclosed. Provided is a catalytic material of at least two front and two rear layers in conjunction with a substrate, where each of the layers includes a support, all layers comprise a platinum group metal component, and the rear bottom layer is substantially free of a ceria-containing oxygen storage component (OSC).