Layered Catalyst Oxygen Storage Distribution
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Solution Overview
Problem
Existing three-way catalysts face challenges in maintaining catalytic activity under high exhaust gas temperatures due to thermal degradation of alumina supports, leading to reduced surface area and efficiency in oxidizing hydrocarbons and reducing nitrogen oxides, especially during cold start and rich transient conditions.
Innovation Solution
A layered catalyst system with varying configurations of catalytic materials, including inner, middle, and outer layers with specific compositions and oxygen storage components, is deployed on a carrier to optimize oxygen storage and precious metal distribution, enhancing catalytic activity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If activated alumina support is used to provide high surface area, then catalytic activity is improved, but thermal stability deteriorates at elevated temperatures
Solution Approach 1:
The catalyst is divided into multiple functional layers with distinct compositions and roles. The washcoat layer contains the precious metal catalyst on a high-surface-area support, while the stabilizer layer provides thermal stability. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The catalyst uses composite material structures including alumina-zirconia mixed oxides and alumina-ceria mixed oxides as supports. These composite materials combine the high surface area properties of alumina with the thermal stability of zirconia and ceria, creating a support that simultaneously provides both catalytic activity and resistance to thermal degradation.
2Productivity
If multiple layers with oxygen storage components are added to improve catalytic performance, then conversion efficiency is improved, but device complexity increases
Solution Approach 1:
The oxygen storage component performs multiple functions: it stores oxygen during lean conditions and releases it during rich conditions, maintaining three-way conversion efficiency across varying exhaust compositions. This multi-functionality improves catalytic performance without requiring separate components for each function.
Solution Approach 2:
Different layers are assigned specific compositions and properties optimized for their local function. The washcoat layer is designed for maximum catalytic activity with precious metals on high-surface-area support, while the stabilizer layer is designed for thermal stability. This local optimization allows each layer to excel at its specific task.
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 layered catalyst system demonstrates improved conversions of hydrocarbons, carbon monoxide, and nitrogen oxides, maintaining performance across temperature variations and transient conditions, with specific configurations showing enhanced stability and efficiency compared to traditional two-layer systems.
Implementation Method 1
Such catalysts promote the oxidation by oxygen in the exhaust gas stream of unburned hydrocarbons and carbon monoxide
Implementation Method 2
as well as the reduction of nitrogen oxides to nitrogen
Implementation Method 3
The washcoat layer comprises a support and an oxygen storage component
Data Source
AI summary
A layered three-way conversion catalyst having the capability of simultaneously catalyzing the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides is disclosed. Engine exhaust treatment system and methods of using the same are also provided. The catalytic material can be provided in layers such that a larger amount of oxygen storage component is provided in a downstream zone as compared to an upstream zone. For example, the upstream zone can be configured to have one, two, or three layers, and the downstream zone can be independently configured to have one, two, or three layers. In one or more embodiments, the catalyst supported on a carrier has three layers, where at least two of the layers are zoned to have an oxygen storage component being present in an upstream zone in an amount that is less than the oxygen storage component present in the downstream zone.