Dual-Layer Rhodium Catalyst Structure for High-Temperature NOx Removal
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Solution Overview
Problem
Existing exhaust gas purification devices using noble metals like Pt, Pd, and Rh face deterioration in NOx removal performance under high temperature environments, necessitating improved oxygen storage capacity (OSC) to maintain efficiency.
Innovation Solution
A dual-layer catalyst structure with specific particle size and cerium content distribution, utilizing first and second rhodium-containing catalyst layers supported on metal oxide carriers, along with cerium-containing oxides, to enhance oxygen storage capacity and maintain catalyst performance under high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional catalyst structure with uniform cerium distribution is used, then the manufacturing process is simple, but the oxygen storage capacity deteriorates under high temperature environments
Solution Approach 1:
The patent applies local quality by creating a non-uniform cerium distribution pattern where the cerium content varies through the thickness of the catalyst layer. Specifically, the cerium content is higher in the downstream region (closer to exhaust outlet) and lower in the upstream region (closer to exhaust inlet), which optimizes oxygen storage capacity at different locations to maintain NOx removal performance under high temperature conditions while managing thermal effects locally
2Reliability
If the cerium content is increased uniformly throughout the catalyst layer, then the oxygen storage capacity is improved, but the manufacturing precision requirements increase due to the need for specific gradient distribution
Solution Approach 1:
The patent applies preliminary action by pre-establishing the cerium gradient distribution pattern during the catalyst manufacturing process. The cerium-containing oxide is incorporated with a predetermined concentration gradient before the catalyst is installed, ensuring that the optimal oxygen storage capacity is achieved without requiring complex real-time adjustments during operation. This pre-configured gradient simplifies the overall manufacturing process while meeting precision requirements
3Adaptability or versatility
If a single-layer catalyst structure is used, then the device complexity is reduced, but the ability to maintain performance under fluctuating oxygen conditions deteriorates
Solution Approach 1:
The patent applies dynamics by designing a catalyst layer with dynamic oxygen storage capacity through the cerium gradient structure. The varying cerium content across the layer thickness enables different regions to respond dynamically to changing oxygen conditions - the downstream region with higher cerium content handles oxygen excess conditions, while the upstream region with lower cerium content manages oxygen deficient conditions, allowing the catalyst to adapt to fluctuating exhaust conditions
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 dual-layer catalyst structure provides high oxygen storage capacity and efficient removal of harmful components even after exposure to high temperatures, ensuring sustained catalyst performance.
Implementation Method 1
a first catalyst layer containing a first Rh-containing catalyst. The first Rh-containing catalyst contains a first metal oxide carrier and first Rh particles supported on the first metal oxide carrier
Implementation Method 2
a material having an ability to absorb and release oxygen to reduce fluctuation of the atmosphere, i.e., an oxygen storage capacity (OSC), is used for the exhaust gas purification device
Data Source
AI summary
The exhaust gas purification device includes: a substrate including an upstream end and a downstream end; a first catalyst layer formed in a first region extending between the downstream end and a first position; and a second catalyst layer formed in a second region extending between the upstream end and a second position and contains second rhodium particles. The first catalyst layer contains a first rhodium-containing catalyst and a first cerium-containing oxide. A mean of a particle size distribution of first rhodium particles contained in the first rhodium-containing catalyst is from 2 nm to 10 nm. An amount of rhodium dissolved into the first metal oxide carrier based on a total weight of rhodium contained in the first rhodium-containing catalyst is less than 17 wt %. A cerium content (g/L) in the first catalyst layer is equal to or greater than a cerium content (g/L) in the second catalyst layer.