Exhaust Gas Purification Catalyst Layer Particle Size Optimization
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Solution Overview
Problem
Existing exhaust gas purification catalysts face challenges in maintaining low-temperature purification activity and ensuring sufficient oxygen storage capacity (OSC), especially at high temperatures, due to the reduced frequency of contact with the Rh-containing layer.
Innovation Solution
The catalyst comprises a substrate with a catalyst layer consisting of a lower layer with Rh and an upper layer with Pd, where the upper layer includes an upstream and downstream catalyst layer with a cumulative 50% particle size D50 of 6 μm or more and 10 μm or less, enhancing the frequency of contact with Pd and maintaining OSC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the catalyst layer includes a top layer containing Pd and a bottom layer containing Rh, then the low-temperature purification activity is improved, but the frequency of contact with the Rh-containing layer decreases, causing insufficient OSC function
Solution Approach 1:
The patent applies local quality by controlling the particle size distribution of the powder material in different regions of the catalyst layer. Specifically, the cumulative 50% particle size D50 is set to 6 μm or more and 10 μm or less in the upstream catalyst layer to optimize both Pd contact frequency for low-temperature activity and Rh contact frequency for OSC function, rather than using a uniform particle size throughout.
2Productivity
If the cumulative 50% particle size D50 of the powder material is reduced to increase Pd contact frequency, then the low-temperature purification activity is enhanced, but the OSC function may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the cumulative 50% particle size D50 of the powder material to a specific range (6 μm or more and 10 μm or less). This parameter optimization balances the frequency of contact with both Pd and Rh catalyst metals, enabling enhanced low-temperature purification activity while maintaining sufficient oxygen storage capacity.
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 improves low-temperature purification activity and ensures sufficient OSC, while also suppressing pressure loss and avoiding thermal stress issues during substrate firing.
Implementation Method 1
warming-up of a catalyst by an oxidation reaction of HC and CO in Pd
Implementation Method 2
an oxygen storage capacity (OSC) needs to be sufficiently ensured for reducing an oxygen concentration variation in the exhaust gas
Data Source
AI summary
An exhaust gas purification catalyst includes a substrate and a catalyst layer on the substrate. The catalyst layer includes lower and upper catalyst layers. The lower catalyst layer includes a powder material containing a powdered carrier, and catalyst metal particles containing Rh on the carrier. The upper catalyst layer includes an upstream catalyst layer in an upstream side in an exhaust gas flow direction, and a downstream catalyst layer in a downstream side in the exhaust gas flow direction. At least the upstream catalyst layer of the upstream and downstream catalyst layers includes a powder material containing a powdered carrier, and catalyst metal particles containing Pd on the carrier. A cumulative 50% particle size D50 in a volume-based particle size distribution of the powder material included in at least the upstream catalyst layer of the upstream and downstream catalyst layers is 6 μm or more and 10 μm or less.