Dual-Layer Rhodium Catalyst for High-Temperature NOx Reduction
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Solution Overview
Problem
Existing exhaust gas purification devices using noble metals as catalysts experience a decrease in NOx reducing performance when exposed to high temperature exhaust gases.
Innovation Solution
The device employs a dual-layer catalyst system with specific particle size and distribution of rhodium-containing catalysts, supported on metal oxide carriers, and a cerium-containing oxide to maintain catalyst efficiency under high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional catalyst with noble metals is used, then initial NOx reducing performance is achieved, but performance decreases after exposure to high temperature exhaust gases
Solution Approach 1:
The invention changes the particle size parameter of rhodium from conventional larger sizes to specifically 2-10 nm, and controls the dissolution parameter to be less than 17 wt%. These parameter changes enable the catalyst to maintain high NOx reducing performance after exposure to high temperature exhaust gases, resolving the contradiction between initial performance and temperature resistance.
Solution Approach 2:
The invention uses a composite structure where rhodium particles are supported on metal oxide carriers with specific surface areas (10-100 m²/g). This composite material approach, combining rhodium with carefully selected metal oxide supports, creates a catalyst that maintains stability and performance under high temperature conditions, addressing the reliability-temperature resistance contradiction.
2Productivity
If rhodium particle size is reduced to increase surface area, then catalytic activity increases, but particle coarsening occurs at high temperature
Solution Approach 1:
The invention optimizes the particle size parameter to 2-10 nm, which is large enough to resist coarsening at high temperatures yet small enough to maintain high surface area and catalytic activity. This precise parameter control resolves the contradiction between productivity and compositional stability.
Solution Approach 2:
The invention employs metal oxide carriers with specific surface areas of 10-100 m²/g, creating a porous support structure that disperses rhodium particles effectively. This porous material approach prevents particle aggregation and coarsening while maintaining high catalytic activity, addressing the productivity-stability contradiction.
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 system effectively reduces NOx with high efficiency even after exposure to high temperature exhaust gases, maintaining catalyst performance by controlling rhodium particle coarsening and optimizing oxygen storage capacity.
Implementation Method 1
a first catalyst layer containing a first rhodium-containing catalyst and a first cerium-containing oxide, the first rhodium-containing catalyst containing a first metal oxide carrier and first rhodium particles supported on the first metal oxide carrier
Implementation Method 2
a first catalyst layer containing a first rhodium-containing catalyst and a first cerium-containing oxide
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 throughout a first region extending between the upstream end and a first position; and a second catalyst layer that is formed throughout a second region extending between the downstream 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 to form a solid solution based on a total weight of rhodium contained in the first rhodium-containing catalyst is less than 17 wt %.