Layered Catalyst for Small Engine Exhaust Durability
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Solution Overview
Problem
Small internal combustion engines pose a harsh environment for catalytic exhaust treatment due to high vibration and temperature, leading to catalyst degradation and reduced durability, especially for palladium-only catalysts which are prone to poisoning and less effective in converting short-chain hydrocarbons.
Innovation Solution
A catalyst article with a first layer comprising palladium as the primary catalytic component, optionally with platinum and rhodium, and a second layer containing rhodium supported on a thermostable oxygen storage component, both coated on a carrier with a uniform undercoat layer to enhance adherence and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-layer palladium catalyst is used, then the catalyst cost is reduced, but the durability and conversion efficiency deteriorate under high vibration and temperature conditions
Solution Approach 1:
The catalyst is divided into two distinct layers: a first layer containing palladium as the primary catalytic component, and a second layer containing rhodium and platinum group metals. This segmentation allows each layer to perform specific functions, with the second layer protecting the first layer from degradation under high vibration and temperature conditions, thereby improving durability while maintaining reduced overall platinum group metal content
Solution Approach 2:
The invention uses a composite catalyst structure combining different platinum group metals (palladium, rhodium, platinum) in distinct layers. The composite nature of the catalyst allows optimization of each layer's composition and function, achieving both cost reduction through lower overall precious metal content and improved durability through the protective effect of the second layer
2Device complexity
If a single-layer catalyst is used, then the device complexity is reduced, but the conversion efficiency of short-chain hydrocarbons and durability worsen
Solution Approach 1:
The catalyst is divided into two distinct layers: a first layer containing palladium as the primary catalytic component, and a second layer containing rhodium and platinum group metals. This segmentation allows each layer to perform specific functions, with the second layer protecting the first layer from degradation under high vibration and temperature conditions, thereby improving durability while maintaining reduced overall platinum group metal content
Solution Approach 2:
Different regions of the catalyst (first layer vs. second layer) have different compositions and properties optimized for specific functions. The first layer is optimized for cost-effectiveness with palladium as primary component, while the second layer is optimized for durability and catalytic activity with rhodium and platinum group metals, creating local quality variations that enhance overall performance
3Strength
If ceramic carriers are used, then the catalyst strength is improved, but the catalyst reliability worsens due to cracking and pulverization from vibration
Solution Approach 1:
The invention employs a composite carrier structure combining ceramic material with metal components. The ceramic portion provides high-temperature stability and structural strength, while the metal portion (such as stainless steel or other vibration-resistant metals) provides resistance to cracking and pulverization from vibration. This composite approach allows the carrier to withstand both the thermal and mechanical stresses of small engine operation, improving reliability while maintaining the necessary strength
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 article exhibits improved durability and performance, reducing carbon monoxide, hydrocarbon, and nitrogen oxide light-off temperatures, and maintaining high conversion efficiency even after aging at high temperatures, while using less platinum group metal, thus meeting emission standards effectively.
Implementation Method 1
A catalyst article with a first layer comprising palladium as the primary catalytic component, optionally with platinum and rhodium, and a second layer containing rhodium supported on a thermostable oxygen storage component
Implementation Method 2
a second layer containing rhodium supported on a thermostable oxygen storage component
Data Source
AI summary
Catalyst articles comprising substantially only a palladium precious metal component in a first catalytic layer and a rhodium component in a second catalytic layer and related methods of preparation and use are disclosed. Also disclosed is a catalyst article comprising a first layer formed on a carrier substrate, wherein the first layer comprises a refractory metal oxide and has a surface that is substantially uniform; a second layer formed on the first layer, wherein the second layer comprises i) an oxygen storage component that is about 50-90% by weight of the second layer and ii) a palladium component in an amount of about 2-5% by weight of the second layer, wherein the palladium component is substantially the only platinum group metal component, and a palladium-free third layer comprising a rhodium component supported on a thermostable oxygen storage component which is about 80-99% by weight of the second layer. One or more improved properties are exhibited by the catalyst article.