Exhaust Catalyst Layer Gradients for Start-Up Purification Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust gas purifying catalysts face challenges in achieving high purification performance during engine start-up with low noble metal usage and ensuring thermal durability due to noble metal aggregation.
Innovation Solution
The catalyst is configured with a first section having a higher noble metal concentration than a downstream section, and a milder concentration gradient in the thickness direction, enhancing dispersibility and thermal durability while maintaining purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the noble metal concentration is increased on the upstream side to improve low-temperature purification performance, then the purification rate during engine start-up is improved, but the thermal durability deteriorates due to noble metal aggregation
Solution Approach 1:
The catalyst layer is designed with spatially varying noble metal concentrations and gradient characteristics. The upstream side has higher noble metal concentration with a first gradient from surface to substrate, while the downstream side has lower concentration with a second gradient. This local quality differentiation allows the upstream side to provide high activity for low-temperature purification while the downstream side maintains thermal stability, resolving the contradiction between purification performance and thermal durability.
Solution Approach 2:
The invention introduces gradient control in the thickness direction (from catalyst layer surface to substrate) as an additional dimension beyond the conventional exhaust gas flow direction. By controlling the concentration gradient from surface to substrate in each section, the patent creates a three-dimensional concentration distribution that optimizes both low-temperature activity and thermal stability, addressing the contradiction through multi-dimensional parameter control.
2Ease of manufacture
If the noble metal is dispersed uniformly to simplify the catalyst configuration, then the manufacturing process is simplified, but the low-temperature purification performance deteriorates
Solution Approach 1:
The catalyst layer is segmented into multiple sections along the exhaust gas flow direction, with each section having distinct noble metal concentration characteristics. This segmentation allows different regions to perform specialized functions: upstream sections with higher concentrations and specific gradients for low-temperature activity, and downstream sections with lower concentrations for thermal stability. The segmented structure achieves superior performance while maintaining reasonable manufacturing complexity through standardized gradient control in each segment.
3Productivity
If the noble metal concentration gradient is steep in the thickness direction to increase surface activity, then the low-temperature purification performance is improved, but the thermal durability deteriorates due to aggregation
Solution Approach 1:
Different gradient characteristics are applied locally to different sections of the catalyst layer. The upstream side employs a first concentration gradient from surface to substrate that optimizes low-temperature activity, while the downstream side employs a second gradient that prioritizes thermal stability. This local differentiation of gradient characteristics resolves the contradiction between surface activity and thermal durability by allowing each section to have optimized gradient properties for its specific function.
Solution Approach 2:
The catalyst layer functions as a composite structure with varying noble metal concentrations and gradient characteristics across different sections and depths. By creating a composite concentration distribution pattern rather than a uniform or single-gradient structure, the patent achieves both high surface activity in upstream regions and thermal stability in downstream regions, resolving the contradiction through composite material design principles.
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 catalyst achieves improved exhaust gas purification performance during engine start-up and maintains thermal durability by appropriately dispersing noble metals, preventing aggregation and enhancing CO, HC, and NOx removal at low temperatures.
Implementation Method 1
CO oxidation and HC oxidation, which are exothermic reactions, actively take place on the upstream side, and thus the temperature of the entire catalyst can be increased efficiently
Implementation Method 2
these three components are purified mainly using noble metals
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
The present invention provides an exhaust gas purifying catalyst including a first catalyst layer (12). The first catalyst layer (12) includes a first section (14) and a second section (15) in an exhaust gas flow direction, the first section (14) being located on an upstream side in the exhaust gas flow direction relative to the second section (15). The first section (14) and the second section (15) both contain a catalytically active component including a specific element. A concentration of the specific element is higher in the first section (14) than in the second section (15). A concentration gradient of the specific element contained in the first section (14) in a thickness direction of the catalyst layer (12) is milder than a concentration gradient of the specific element contained in the second section (15) in the thickness direction.