Double-Layer Three-Way Catalyst for GPF Cold-Start Light-Off
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Solution Overview
Problem
Current three-way catalyst systems for gasoline engines face challenges in maintaining optimal HC, CO, and NOx conversion under oscillating lean and rich conditions, and exhibit poor HC light-off performance during cold starts, especially when used in conjunction with gasoline particulate filters.
Innovation Solution
A double-layer three-way catalyst system is developed, featuring a first layer with active alumina, cerium/zirconium mixed oxide, and palladium, and a second layer with active alumina and rhodium, where the second layer is free of cerium and contains a neodymium/zirconium mixed oxide, optimized with specific noble metal loadings and deposition methods on an inert catalyst support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a gasoline particulate filter is used as a stand-alone catalyst, then PM emissions are reduced, but HC light-off performance deteriorates
Solution Approach 1:
The catalyst system is divided into two separate functional components: a GPF for PM filtration and a TWC upstream for HC/CO/NOx conversion. This segmentation allows each component to optimize its specific function without compromising the other, resolving the contradiction between PM reduction and HC light-off performance.
Solution Approach 2:
A three-way catalyst is introduced as an intermediary component upstream of the GPF. This intermediary TWC handles the HC, CO, and NOx conversion before gases reach the GPF, enabling the GPF to focus solely on PM filtration while maintaining excellent HC light-off performance through the upstream TWC.
2Adaptability or versatility
If oxygen storage material is included in TWC formulation, then operation under oscillating conditions is broadened, but PM filtration performance deteriorates
Solution Approach 1:
The system separates the TWC function (with OSM for oscillating condition adaptability) from the GPF function (for PM filtration). By placing the TWC upstream with adequate OSM content, the system achieves both broad adaptability to oscillating conditions and effective PM filtration in the downstream GPF without interference.
Solution Approach 2:
The TWC upstream is specifically formulated with oxygen storage material to handle oscillating lean-rich conditions, while the GPF downstream is optimized for PM filtration. Each component has localized quality tailored to its specific function, resolving the contradiction between adaptability and PM filtration performance.
3Object-generated harmful factors
If TWC is placed upstream of GPF, then HC, CO, and NOx conversion is maintained, but system complexity increases
Solution Approach 1:
The upstream TWC performs multiple functions simultaneously: HC oxidation, CO oxidation, and NOx reduction under oscillating conditions. This multi-functionality consolidates several pollutant control tasks into a single component, managing system complexity while maintaining comprehensive conversion performance.
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 light-off performance for HC, CO, and NOx pollutants, reducing emissions during cold starts and maintaining effective pollutant conversion across varying engine conditions.
Implementation Method 1
oxygen storage material (OSM) in the form of Ce-mixed oxides were included in the formulation of the TWC
Implementation Method 2
a first layer on the inert catalyst support, comprising active alumina, a cerium/zirconium mixed oxide and palladium as a catalytically active noble metal and a second layer applied to the first layer and in direct contact with the exhaust gas to be purified, comprising active alumina and rhodium as a catalytically active noble metal
Implementation Method 3
comprising active alumina, a cerium/zirconium mixed oxide and palladium as a catalytically active noble metal
Data Source
AI summary
The present invention describes a double-layer three-way catalyst on an inert catalyst support comprising a first layer in direct contact with the inert catalyst support, comprising active alumina, a cerium/zirconium mixed oxide and palladium and a second layer applied to the first layer and in direct contact with the exhaust gas to be purified, comprising active alumina and rhodium, characterized in that the second layer is free of cerium and cerium containing materials, the use of such catalyst for cleaning the exhaust gases of a motor vehicle equipped with a gasoline engine and an exhaust gas treatment system comprising such catalyst upstream of a gasoline particulate filter (GPF).