Multi-layer Washcoat Structure for Catalytic Converters
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Solution Overview
Problem
Commercially available catalytic converters have high light-off temperatures, leading to increased emissions during cold starts and reduced effectiveness over time, due to the aging of platinum group metal catalysts, which results in higher pollutant release and increased costs.
Innovation Solution
The development of catalytic converters with a multi-layer washcoat structure, where zeolites are separated from catalytically active particles, using composite nano-particles bonded to micron-sized carrier particles, reducing the amount of platinum group metal required and maintaining performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If platinum group metal catalysts are deposited on substrates by wet chemistry methods, then catalytic activity is achieved, but light-off temperature becomes high and aging occurs over time
Solution Approach 1:
The washcoat is divided into multiple layers: a first layer containing zeolite particles for pollutant storage during cold-start, and a second layer containing catalytically active particles for decomposition. This segmentation allows each layer to perform its specific function optimally, with the catalytic layer being exposed to pollutants after light-off without being contaminated by zeolites that would require higher temperatures to release stored pollutants.
Solution Approach 2:
Different regions of the washcoat are given different compositions and functions. The first layer near the substrate has high zeolite concentration for maximum storage capacity during cold-start, while the second layer has high catalytic activity for efficient pollutant decomposition. This local differentiation optimizes both cold-start performance and hot-operation efficiency.
2Object-generated harmful factors
If high concentration of zeolites is used for pollutant storage during cold-start, then cold-start emissions are reduced, but light-off temperature increases
Solution Approach 1:
The washcoat is segmented into layers with the zeolite-rich first layer separated from the catalytic second layer. This allows the zeolite layer to store pollutants during cold-start without requiring the catalytic layer to operate at high temperatures, thus reducing light-off temperature while maintaining cold-start emission control.
Solution Approach 2:
The first zeolite layer acts as an intermediary that temporarily stores pollutants during cold-start, then releases them to the catalytic second layer at lower temperatures. This mediator function allows decoupling of the high-temperature storage function from the low-temperature catalytic function.
3Reliability
If platinum group metals are used in catalytic converters, then catalytic activity is achieved, but cost increases significantly
Solution Approach 1:
The invention changes the physical and chemical parameters of the catalytic particles by using composite nano-particles with core-shell structures. The core provides structural stability while the shell provides catalytic activity, allowing reduced PGM loading while maintaining or enhancing catalytic performance. The nano-scale dimensions increase surface area to volume ratio, further improving efficiency.
Solution Approach 2:
Composite nano-particles are used where a core material (such as metal oxide) is combined with a catalytic shell (containing platinum group metals). This composite structure maximizes the utilization of expensive PGMs by confining them to the outer shell where they contact pollutants, while the core provides structural support and stability, reducing overall PGM content while maintaining activity.
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 approach lowers the light-off temperature, reduces emissions, and prolongs the effectiveness of catalytic converters while minimizing the use of platinum group metals, thereby improving emission control and reducing costs.
Implementation Method 1
zeolites act as a temporary storage area for the pollutants carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) during the cold-start period
Implementation Method 2
the stored gases are released and subsequently decomposed by the catalytically active material on the substrate
Implementation Method 3
composite nano-particles bonded to micron-sized carrier particles
Data Source
AI summary
Disclosed are, inter alia, methods of forming coated substrates for use in catalytic converters, as well as washcoat compositions and methods suitable for using in preparation of the coated substrates, and the coated substrates formed thereby. The catalytic material is prepared by a plasma-based method, yielding catalytic material with a lower tendency to migrate on support at high temperatures, and thus less prone to catalyst aging after prolonged use. Also disclosed are catalytic converters using the coated substrates, which have favorable properties as compared to catalytic converters using catalysts deposited on substrates using solution chemistry. Also disclosed are exhaust treatment systems, and vehicles, such as diesel vehicles, particularly light-duty diesel vehicles, using catalytic converters and exhaust treatment systems using the coated substrates.