Exhaust Catalyst Rh Particle Size Control Durability
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Solution Overview
Problem
Conventional exhaust gas purification catalysts using Rh fine particles with controlled sizes face durability issues due to aggregation during catalytic reactions, and the optimal placement of these particles for maximum effect has not been adequately examined.
Innovation Solution
An exhaust gas purification catalyst with a two-layer structure, where Rh fine particles with controlled average particle sizes (1.0 nm to 2.0 nm) and low standard deviation (0.8 nm or less) are used in the downstream portion, and Pt is used in the upstream portion, with an OSC material added to enhance durability and NOx conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Rh fine particles with controlled particle sizes are used, then catalytic activity is improved, but particle aggregation occurs during catalytic reaction leading to reduced durability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size parameters of Rh fine particles (average particle size of 0.5 nm to 2.0 nm with standard deviation of 0.7 nm or less) and the composition parameters of the carrier (specific ratios of Ce, Zr, La, and Al oxides). These parameter optimizations prevent particle aggregation during catalytic reactions while maintaining high catalytic activity, thereby resolving the contradiction between improving catalytic performance and ensuring long-term durability.
Solution Approach 2:
The patent employs composite materials by creating a complex oxide carrier system comprising Ce-Zr-La-Al composite oxide with specific compositional ratios. This composite structure provides enhanced stability and dispersion for Rh fine particles, preventing their aggregation during catalytic operation. The synergistic interaction among different oxide components maintains both the small particle size and high catalytic activity of Rh, thus resolving the durability issue.
2Quantity of substance
If the amount of noble metal is reduced, then resource efficiency is improved, but catalytic activity may be insufficient to meet emission regulations
Solution Approach 1:
The patent utilizes parameter changes by optimizing the particle size distribution of Rh to an average of 0.5 nm to 2.0 nm with a standard deviation of 0.7 nm or less. This precise parameter control maximizes the specific surface area and catalytic efficiency per unit mass of Rh, enabling reduced noble metal loading while maintaining sufficient catalytic activity to meet emission regulations.
Solution Approach 2:
The patent applies local quality by creating highly active catalytic sites through uniformly dispersed ultra-fine Rh particles (0.5-2.0 nm) on the composite oxide carrier. This localized optimization of particle size and distribution ensures that each Rh atom contributes maximally to catalytic activity, allowing reduced overall Rh content while achieving the required emission control performance.
3Productivity
If Rh fine particles are placed in the upstream portion, then catalytic effect is maximized, but particle aggregation occurs reducing durability
Solution Approach 1:
The patent applies parameter changes by optimizing both the physical parameters (particle size of 0.5-2.0 nm with standard deviation ≤0.7 nm) and chemical parameters (carrier composition ratios) of Rh fine particles. These optimized parameters enable the particles to maintain high catalytic activity when placed in the upstream portion while resisting aggregation, thus simultaneously achieving maximum catalytic effect and durability.
Solution Approach 2:
The patent employs composite materials by using a Ce-Zr-La-Al composite oxide carrier with specific compositional ratios to support Rh fine particles in the upstream portion. This composite carrier structure provides enhanced stability and dispersion, preventing particle aggregation even under the harsh conditions of the upstream catalytic environment, thereby maintaining both high productivity and durability.
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 solution significantly improves the durability and NOx purification ability of the catalyst, reducing Rh usage while maintaining high catalytic activity by suppressing particle aggregation and optimizing the distribution of Rh fine particles.
Implementation Method 1
the downstream portion contains Rh fine particles, and the Rh fine particles have an average particle size measured by a transmission electron microscope observation of 1.0 nm or more to 2.0 nm or less, and a standard deviation σ of the particle size of 0.8 nm or less
Implementation Method 2
a three-way catalyst that simultaneously performs oxidation of CO and HC and reduction of NOx is used as the exhaust gas purification catalyst
Implementation Method 3
the upstream portion is formed on a part of the downstream portion, wherein the downstream portion contains Rh fine particles
Implementation Method 4
the downstream portion further contains an OSC material that has an oxygen storage capacity
Data Source
AI summary
The present disclosure provides an exhaust gas purification catalyst having improved durability, which comprises a substrate and a catalyst coat layer formed on the substrate, the catalyst coat layer having a two-layer structure, wherein the catalyst coat layer includes an upstream portion on an upstream side and a downstream portion on a downstream side in an exhaust gas flow direction, and a part or all of the upstream portion is formed on a part of the downstream portion, wherein the downstream portion contains Rh fine particles, and wherein the Rh fine particles have an average particle size measured by a transmission electron microscope observation of 1.0 nm or more to 2.0 nm or less, and a standard deviation σ of the particle size of 0.8 nm or less.