Layered Three-Way Catalyst for Thermal Degradation
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Solution Overview
Problem
Current three-way-conversion (TWC) catalysts face challenges in maintaining performance under high load/high speed conditions due to thermal degradation, leading to rapid loss of activity and support surface area, especially in close-coupled catalyst designs, which necessitates the development of new configurations to meet stringent emission standards and slow deactivation.
Innovation Solution
The implementation of a TWC catalyst system comprising a front single catalytic layer and a rear double layer, where the first layer of the rear zone lacks oxygen storage components (OSC), optimizing the distribution and composition of platinum group metals (PGMs) such as palladium and rhodium across layers to enhance emission control efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the catalyst is located close to the manifold (close-coupled position), then rapid heat-up and improved emission control is achieved, but thermal degradation increases leading to rapid loss of activity and support surface area
Solution Approach 1:
The catalyst system is divided into two separate converters: a close-coupled (CC) converter positioned near the manifold for rapid heat-up and initial emission control, and an underbody (UB) converter positioned downstream for sustained conversion and reduced thermal degradation. This segmentation allows each converter to be optimized for its specific function and operating conditions.
Solution Approach 2:
Each converter is designed with different characteristics suited to its location: the CC converter uses light, small-size substrates with high cell density and high PGM loading to achieve rapid heat-up, while the UB converter uses larger volume substrates with lower cell density and lower PGM loading to reduce pressure drop and withstand thermal degradation over time.
2Productivity
If high PGM loading is used in the close-coupled catalyst, then rapid heat-up and improved emission control is achieved, but cost increases and thermal degradation accelerates
Solution Approach 1:
PGM loading is segmented between the two converters: the CC converter receives high PGM loading (including Pt, Pd, Rh, Re, Ru, Ir) to enable rapid heat-up and immediate emission control, while the UB converter uses lower PGM loading since it operates at more stable temperatures and provides sustained conversion over the long term.
Solution Approach 2:
The system changes the operating parameters (temperature, pressure, gas composition) between the two converters to optimize PGM utilization: the CC converter operates in a high-temperature, high-stress environment that requires high PGM loading for rapid activation, while the UB converter operates in a more stable environment that allows lower PGM loading with sustained performance.
3Productivity
If multiple catalyst layers are used, then emission control performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The catalyst system uses two separate single-layer converters rather than one complex multi-layer converter. Each converter contains a single washcoat layer with specific PGM composition tailored to its operating conditions, simplifying manufacturing while achieving superior overall performance through the sequential action of both converters.
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 catalyst's performance by maintaining activity and reducing thermal degradation, achieving enhanced oxidation of hydrocarbons and reduction of nitrogen oxides across a wide temperature range, thereby meeting stringent emission standards.
Implementation Method 1
The catalytic material employed is effective to substantially simultaneously oxidize the carbon monoxide and the hydrocarbons and reduce the nitrogen oxides
Implementation Method 2
oxidize the carbon monoxide and the hydrocarbons
Implementation Method 3
reduce the nitrogen oxides
Data Source
Figure 1a~2
Figure 3~4
AI summary
Disclosed herein is a layered three-way catalytic system being separated in a front and a rear portion having the capability of simultaneously catalyzing the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides. Provided is a catalyst composite comprising a single front catalytic layer and two rear catalytic layers in conjunction with a substrate, where the single font layer and the rear bottom layer comprise a Pd component, the rear top layer comprises a Rh component, and the rear bottom layer is substantially free of an oxygen storage component (OSC).