Exhaust Catalyst Layered Coating for Rh Poisoning
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Solution Overview
Problem
Existing exhaust gas purification catalysts face challenges in maintaining catalytic activity, particularly under air-fuel ratio rich conditions where hydrocarbon poisoning of precious metals like rhodium (Rh) occurs, leading to decreased NOx conversion performance.
Innovation Solution
An exhaust gas purification catalyst with a substrate and a catalyst coating layer featuring an upstream coat layer and a downstream coat layer, where the downstream coat layer includes Rh, alumina-ceria-zirconia complex oxide, and alkaline earth metals like barium or strontium, which suppresses Rh poisoning while maintaining oxygen storage capacity (OSC).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional catalyst coating layer with Rh is used, then NOx conversion is achieved under stoichiometric conditions, but Rh poisoning by HC occurs under rich air-fuel ratio conditions, leading to decreased catalytic activity
Solution Approach 1:
An OSC material layer is introduced as an intermediary between the HC-rich exhaust gas and the Rh catalyst. This layer absorbs excess HC and manages oxygen release, protecting the Rh from direct contact with poisoning HC species while maintaining NOx reduction function
Solution Approach 2:
The catalyst coating layer is segmented into multiple functional layers: an OSC material layer (containing Ba and Al2O3) positioned to face the exhaust gas flow, and a Rh-containing catalytic layer positioned downstream. This segmentation allows each layer to perform its specific function independently, with the OSC layer protecting the Rh layer
2Quantity of substance
If the amount of precious metal is reduced, then resource efficiency improves, but catalytic activity decreases
Solution Approach 1:
The OSC material (Ba-Al2O3) provides self-service by automatically absorbing HC and releasing oxygen as needed during catalyst operation. This self-regulating mechanism protects the Rh catalyst and maintains activity without requiring additional precious metals or complex control systems
Solution Approach 2:
A composite catalyst structure is created combining OSC material (Ba-Al2O3) with Rh catalyst in a layered configuration. This composite structure provides both HC purification function and NOx reduction function while protecting the Rh from poisoning, allowing reduced Rh content without activity loss
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 enhances catalyst performance by preventing Rh poisoning and maintaining NOx conversion efficiency even in rich atmospheres, where HC poisoning is likely, thereby improving overall exhaust gas purification efficiency.
Implementation Method 1
The OSC material is a material that can absorb and release oxygen. The OSC material allows keeping an oxygen concentration constant to maintain a purification performance of the exhaust gas purification catalyst even when an air-fuel ratio varies.
Implementation Method 2
the harmful components are made almost detoxified by an exhaust gas purification catalyst disposed in the exhaust gas purification device
Data Source
AI summary
Provided is an exhaust gas purification catalyst having an improved catalyst performance while securing an OSC in an air-fuel ratio (A/F) rich atmosphere where HC poisoning is likely to occur. The present disclosure relates to an exhaust gas purification catalyst including a substrate and a catalyst coating layer coated on the substrate. The catalyst coating layer has an upstream coat layer formed from an end portion in an upstream side with respect to an exhaust gas flow direction in the exhaust gas purification catalyst and a downstream coat layer formed from an end portion in a downstream side with respect to the exhaust gas flow direction in the exhaust gas purification catalyst. The downstream coat layer includes Rh as a catalytic metal, alumina-ceria-zirconia complex oxide, and alkaline earth metal.