Two-Layer Three-Way Catalyst for Stable CO Conversion
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Solution Overview
Problem
Existing three-way catalysts struggle to maintain effective conversion of CO and NOx under dynamic driving conditions, particularly in the stringent CN6b emissions regulations, requiring further catalyst development to improve performance and stability.
Innovation Solution
A two-layer catalyst structure with specific compositions in each layer, including cerium/zirconium/lanthanum/yttrium mixed oxides and platinum group metals, optimized with a mass ratio of mixed oxide to alumina, enhances the catalyst efficacy and stability, and specific platinum group metals distribution, achieving improved CO conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single coating layer is used for three-way catalyst, then the structure is simple and easy to manufacture, but the catalytic processes for different components cannot be optimally coordinated
Solution Approach 1:
The catalyst is divided into two separate coating layers: a first coating layer containing platinum group metals for hydrocarbon oxidation and a second coating layer containing platinum group metals for nitrogen oxide reduction. This segmentation allows each layer to be optimized for its specific catalytic function, improving overall conversion performance while maintaining manufacturing simplicity through sequential coating application.
2Reliability
If double-layer catalysts are used to separate catalytic processes, then optimal coordination of catalytic effects is achieved, but the structure becomes more complex
Solution Approach 1:
The catalyst is divided into two separate coating layers: a first coating layer containing platinum group metals for hydrocarbon oxidation and a second coating layer containing platinum group metals for nitrogen oxide reduction. This segmentation allows each layer to be optimized for its specific catalytic function, improving overall conversion performance while maintaining manufacturing simplicity through sequential coating application.
Solution Approach 2:
Different platinum group metal compositions are applied to different layers: the first coating layer contains platinum and palladium optimized for hydrocarbon oxidation, while the second coating layer contains platinum and rhodium optimized for nitrogen oxide reduction. This local quality differentiation ensures each region of the catalyst performs its specific function optimally.
3Productivity
If catalysts are designed for high CO conversion under dynamic conditions, then emissions compliance is improved, but the catalyst stability under high exhaust temperatures may be compromised
Solution Approach 1:
The catalyst uses cerium/zirconium mixed oxides with specific compositional parameters (zirconium content between 20-80 mol%) that modify the thermal stability and oxygen storage capacity. This parameter optimization allows the catalyst to maintain high CO conversion performance while resisting degradation under high exhaust temperature conditions.
Solution Approach 2:
The catalyst employs composite materials combining platinum group metals with cerium/zirconium mixed oxides as the carrier. This composite structure leverages the high surface area and catalytic activity of the metal particles supported on the thermally stable ceramic oxide, achieving both high CO conversion and temperature stability.
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 achieves significantly enhanced CO conversion under dynamic conditions, maintaining low emissions and stability, even under high exhaust temperatures, surpassing prior art performance.
Implementation Method 1
As catalytically active materials, platinum group metals, in particular platinum, palladium and rhodium, which are, for example, present on γ alumina as the carrier material, are generally used. Three-way catalysts at approximately λ=1 are capable of simultaneously converting hydrocarbons, carbon monoxide, and nitrogen oxides into harmless components.
Implementation Method 2
Oxygen storage materials are activated by applying catalytically active materials such as platinum group metals and thus also serve as a carrier material for the platinum group metals.
Implementation Method 3
Three-way catalysts at approximately λ=1 are capable of simultaneously converting hydrocarbons, carbon monoxide, and nitrogen oxides into harmless components.
Data Source
AI summary
The present invention relates to a catalyst comprising two layers on an inert catalyst carrier. Layer A contains at least palladium as a platinum group metal, alumina, and a first cerium/zirconium/lanthanum/yttrium mixed oxide. A layer B applied to layer A contains at least rhodium as a platinum group metal, alumina, and a second cerium/zirconium/lanthanum/yttrium mixed oxide.