Layered Automotive Catalyst Composites Alloy Prevention
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Solution Overview
Problem
Current three-way conversion (TWC) catalysts face challenges in efficiently utilizing platinum group metals (PGMs) like palladium and rhodium to meet stringent emission standards for hydrocarbons, carbon monoxide, and nitrogen oxides, as these metals can form less catalytically active alloys when separated.
Innovation Solution
The development of automotive catalyst composites with a two-metal layer structure, where palladium and rhodium are supported on different refractory metal oxides and oxygen storage components, forming a homogeneous mixture to enhance catalytic activity and prevent alloy formation, with specific weight ratios and support materials optimized for improved accessibility and activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If palladium and rhodium are separated into different layers, then alloy formation is prevented and catalytic activity is maintained, but device complexity increases due to multiple coating steps
Solution Approach 1:
The catalyst is divided into two functional layers: a first layer containing palladium on refractory metal oxide for oxidation reactions, and a second layer containing rhodium on oxygen storage component for reduction reactions. This segmentation prevents alloy formation while maintaining distinct catalytic functions for each metal.
Solution Approach 2:
The patent uses composite material structures where palladium is supported on refractory metal oxide in the first layer, and rhodium is supported on oxygen storage component in the second layer. These composite structures optimize the interaction between metals and supports to enhance catalytic performance while preventing unwanted alloying.
2Reliability
If multiple separate washcoats are applied, then platinum group metals are separated to prevent alloying, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into two sequential washcoat applications: first applying a palladium-containing washcoat, then applying a rhodium-containing washcoat. This segmentation ensures physical separation of the metals during deposition, preventing alloy formation while maintaining a systematic manufacturing approach.
Solution Approach 2:
The first layer containing palladium is applied in advance before the second layer containing rhodium is applied. This preliminary action establishes a foundation layer that prevents alloying while optimizing the catalytic structure for subsequent rhodium deposition.
3Device complexity
If palladium and rhodium are mixed in the same layer, then device complexity is reduced, but catalytic activity decreases due to alloy formation
Solution Approach 1:
Instead of mixing palladium and rhodium in a single layer, the invention segments them into two distinct layers with different compositions and functions. The first layer contains palladium on refractory metal oxide, while the second layer contains rhodium on oxygen storage component, preventing alloy formation and maintaining high catalytic activity.
Solution Approach 2:
Each layer is designed with local quality optimized for its specific function: the first layer has palladium on refractory metal oxide optimized for oxidation reactions, while the second layer has rhodium on oxygen storage component optimized for reduction reactions. This local optimization maintains high catalytic activity without requiring metal mixing.
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 improves the catalytic activity for hydrocarbon and nitrogen oxide conversion, enhancing NOx reduction and hydrocarbon light-off temperatures, while maintaining the longevity and efficiency of the catalysts.
Implementation Method 1
catalysts promote the oxidation by oxygen in the exhaust gas stream of unburned hydrocarbons (HC) and carbon monoxide (CO) as well as the reduction of nitrogen oxides (NOx) to nitrogen
Implementation Method 2
palladium and rhodium can form an alloy, which is known to be less catalytically active
Data Source
AI summary
Provided are automotive catalyst composites having a catalytic material on a carrier, wherein the catalytic material comprises at least two layers. The first layer is deposited directly on the carrier and comprises a first palladium component supported on a first refractory metal oxide component, a first oxygen storage component, or a combination thereof. The second layer is deposited on top of the first layer and comprises a rhodium component supported on a second refractory metal oxide component and a second palladium component supported on a second oxygen storage component, a third refractory metal oxide component or a combination thereof. Generally these catalyst composites are used as three-way conversion (TWC) catalysts. Methods of making and using the same are also provided.