Zone-Coated Catalyst Layer for Oxygen Storage and NOx Purification
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Solution Overview
Problem
Existing three-way catalysts face a trade-off between oxygen storage capacity (OSC) and NOx purification performance, with noble metal catalysts like Rh exhibiting high OSC but poor NOx purification when cerium oxide content is increased, and reducing noble metal quantities compromises catalyst activity and durability.
Innovation Solution
A catalytic converter design featuring a zone-coated catalyst layer with a ceria-containing first upper catalyst layer (30-70% of the base material length) and a ceria-free second upper catalyst layer, utilizing palladium and rhodium supported on different oxide carriers to optimize OSC and NOx purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the quantity of noble metal catalysts in a three-way catalyst is greatly reduced, then cost is reduced, but catalyst activity and purification performance significantly deteriorate
Solution Approach 1:
The patent applies local quality by creating zone-coated catalyst layers with different compositions and functions at different locations along the base material. The upstream catalyst layer contains cerium oxide for oxygen storage, while the downstream layer is cerium-free for optimal NOx purification, allowing each region to be optimized for its specific function while using reduced overall noble metal quantities
Solution Approach 2:
The patent segments the catalyst layer into distinct upstream and downstream portions with different compositions. The upstream catalyst layer is designed with cerium oxide to provide oxygen storage capacity, while the downstream catalyst layer is designed without cerium oxide to maximize NOx purification efficiency, allowing independent optimization of each segment's properties
2Quantity of substance
If the quantity of cerium oxide in a carrier is increased, then oxygen storage capacity (OSC) is improved, but NOx purification performance of Rh deteriorates
Solution Approach 1:
The patent segments the catalyst layer into upstream and downstream portions, placing cerium oxide-containing material only in the upstream layer where it provides oxygen storage capacity without interfering with NOx purification. The downstream layer is kept cerium-free to ensure optimal NOx purification performance
Solution Approach 2:
The patent applies local quality by providing different chemical environments at different locations: the upstream region contains cerium oxide for oxygen storage functions, while the downstream region is free of cerium oxide to provide optimal conditions for NOx purification by rhodium
3Quantity of substance
If the length of the first upper catalyst layer is increased, then oxygen storage capacity is improved, but the length available for the second upper catalyst layer decreases
Solution Approach 1:
The patent divides the upper catalyst layer into two distinct segments: a first upper catalyst layer containing cerium oxide for oxygen storage, and a second upper catalyst layer free of cerium oxide for NOx purification. This segmentation allows independent optimization of each layer's length and composition
Solution Approach 2:
The patent optimizes the length ratio between the first and second upper catalyst layers as a critical parameter, setting the first layer length to 30-70% of the total base material length to achieve the optimal balance between oxygen storage capacity and NOx purification 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
The design achieves excellent oxygen storage capacity and NOx purification performance, balancing conflicting requirements by optimizing the length of each catalyst layer, resulting in improved catalytic converter efficiency.
Implementation Method 1
CeO2 present in a co-catalyst achieves the function of absorbing and releasing oxygen so as to compensate for an excess or deficiency of electrical charge and the function of storing oxygen (oxygen storage capacity (OSC))
Implementation Method 2
The component that realizes the catalytic activity in these exhaust gas control catalysts is a noble metal catalyst such as platinum (Pt), palladium (Pd) or rhodium (Rh)
Data Source
AI summary
A catalytic converter (10) includes a base material and a catalyst layer (3). The catalyst layer has a lower catalyst layer (4) and an upper catalyst layer (5). The upper catalyst layer is constituted by a first upper catalyst layer (6) and a second upper catalyst layer (7). The first upper catalyst layer is formed of a first carrier, which is formed of a ceria-containing oxide, and rhodium supported on the first carrier. The second upper catalyst layer is formed of a second carrier and rhodium supported on the second carrier. The second carrier does not contain ceria and is formed of one oxide selected from among zirconia and alumina. A length of the first upper catalyst layer is X % (30 to 70%) of an overall length of the base material. A length of the second upper catalyst layer is 100−X % of the overall length of the base material.