Wall Flow Catalyst Layer Porosity and OSC Capacity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust gas purification devices with high proportions of OSC materials in catalyst layers face issues with peeling, leading to unstable purification performance and increased pressure loss, particularly in wall flow-type particulate filters used in internal combustion engines.
Innovation Solution
A wall flow structure exhaust gas purification device with a catalyst layer having a porosity of 25% or higher in inlet regions and an average occupation ratio of 75% or lower, utilizing an alumina-free catalyst layer with a high proportion of OSC materials like CeO2 or CeO2-ZrO2 complex oxides, which reduces peeling and maintains high OSC capacity over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the proportion of OSC material in the catalyst layer is increased to realize higher OSC capacity, then the purification performance is improved, but the catalyst layer peels readily off the filter
Solution Approach 1:
The invention changes the porosity parameter of the catalyst layer to 25% or higher, which modifies the physical structure to reduce internal stress and improve adhesion. This parameter change allows the catalyst layer to maintain high OSC capacity while preventing peeling by creating a more open, flexible structure that can accommodate thermal and mechanical stresses during operation.
Solution Approach 2:
The invention uses a composite catalyst layer structure combining OSC material with other materials in a specific porosity configuration. This composite approach allows the layer to maintain high OSC capacity for purification while the overall composite structure provides improved mechanical adhesion to the filter substrate, preventing peeling.
2Reliability
If the catalyst layer occupation ratio is increased to improve purification performance, then the OSC capacity is enhanced, but the pressure loss increases
Solution Approach 1:
The invention optimizes the catalyst layer occupation ratio parameter to 75% or lower, which balances purification performance with pressure loss. This parameter setting ensures sufficient catalyst material for effective OSC capacity and purification, while maintaining enough porosity to allow exhaust gas flow with minimal pressure loss.
Solution Approach 2:
The invention applies local quality by creating a catalyst layer with specific porosity distribution, where the occupation ratio is controlled at 75% or lower. This local optimization ensures that catalyst material is distributed effectively to provide purification performance where needed, while maintaining open channels for gas flow to minimize pressure 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
The solution enhances the durability and purification performance of the exhaust gas purification device by preventing catalyst layer peeling and reducing pressure loss, while maintaining high OSC capacity and effective particulate matter trapping.
Implementation Method 1
a carrier made up of an OSC material having oxygen storage capacity
Implementation Method 2
a noble metal supported on the carrier
Implementation Method 3
exhaust gas that flows in through cell inlets passes through a demarcated porous cell partition wall, and is discharged out through the cell outlets. As the exhaust gas passes through the porous cell partition wall, the particulate matter is trapped within the pores inside the partition wall.
Data Source
AI summary
The exhaust gas purification device according to the present invention includes a substrate of wall flow structure having a porous partition wall 16, and a catalyst layer held in internal pores of the partition wall 16. The catalyst layer contains, as a carrier, an OSC material having oxygen storage capacity. In the thickness direction of the partition wall 16, the porosity of the internal pores in inlet regions 16a is 25% or higher, and an average occupation ratio of the catalyst layer held in the internal pores is 75% or lower.