Exhaust Gas Purification Catalyst With Segmented Pore Volumes
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Solution Overview
Problem
Conventional exhaust gas purification catalysts face issues with sintering of catalytically active components at high temperatures in gasoline direct injection engines, leading to poor CO adsorption and oxygen storage performance, and insufficient exhaust gas purification when different components are used in upstream and downstream catalyst layers, especially at high space velocities.
Innovation Solution
A wall flow structure exhaust gas purification catalyst with a first catalyst layer and a second catalyst layer containing different catalytically active components, where the first catalyst layer extends from the upstream end and the second from the downstream end, and the pore volumes are optimized to ensure efficient exhaust gas flow and contact with catalytically active components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plurality of catalytically active components are used in a single catalyst layer, then exhaust gas purification performance is improved, but sintering occurs at high temperatures causing poor CO adsorption and oxygen storage performance
Solution Approach 1:
The catalyst is divided into two separate catalyst layers: a first catalyst layer containing a first catalytically active component and a second catalyst layer containing a second catalytically active component. This segmentation prevents sintering by isolating different components while maintaining their individual functions, thereby preserving CO adsorption and oxygen storage performance even at high temperatures.
Solution Approach 2:
Different regions of the catalyst substrate are assigned different catalytic functions. The first catalyst layer is positioned to handle specific exhaust components while the second catalyst layer handles others, with each layer optimized for its local function. This local differentiation allows each component to operate at optimal dispersion without interfering with the other.
2Stability of the object's composition
If different catalytically active components are used in upstream and downstream catalyst layers, then thermal endurance is improved, but exhaust gas purification performance becomes insufficient at high space velocities
Solution Approach 1:
The pore volume of the catalyst substrate is optimized to 0.4 cm³/cm³ or more, creating sufficient void space that allows exhaust gas to flow freely at high space velocities while still maintaining effective contact with both catalytically active components. This parameter optimization ensures that thermal endurance and high-speed purification performance are both achieved.
3Reliability
If catalyst layers are positioned to maximize contact with exhaust gas, then purification performance is improved, but pressure loss increases
Solution Approach 1:
The catalyst substrate utilizes a porous structure with optimized pore volume (0.4 cm³/cm³ or more) that provides extensive surface area for catalytic reactions while maintaining low flow resistance. This porous architecture allows exhaust gas to penetrate deeply into the catalyst layers for maximum contact without creating excessive pressure drop across the system.
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 configuration achieves excellent CO adsorption and oxygen storage performance after thermal endurance and maintains good exhaust gas purification performance even under high space velocity conditions during high-speed driving.
Implementation Method 1
CO adsorption performance... oxygen storage performance (OSC) after thermal endurance
Implementation Method 2
catalytically active components... efficiently removed by using a plurality of catalytically active components... purifies nitrogen oxide (NOx), carbon monoxide (CO), hydrocarbon (HC)
Data Source
Figure 1
Figure 2~3
AI summary
A substrate (11) includes an inflow-side cell (21), an outflow-side cell (22), and a porous, gas-permeable partition wall (23) that separates the inflow-side cell (21) and the outflow-side cell (22) from each other, and also includes a first catalyst portion (14) that is provided on a side of the partition wall (23) that faces the inflow-side cell (21) at least at a portion in upstream side in an exhaust gas flow direction, and a second catalyst portion (15) that is provided on a side of the partition wall that faces the outflow-side cell at least at a portion in downstream side.With respect to a pore volume of pores with a pore size of 10 to 18 µm, when a measured value of the pore volume in the first catalyst portion (14) and the partition wall (23) within a region where the first catalyst portion (14) is provided is defined as a first pore volume, and a measured value of the pore volume in the second catalyst portion (15) and the partition wall (23) within a region where the second catalyst portion (15) is provided is defined as a second pore volume, the first pore volume is greater than the second pore volume.A catalytically active component contained in the first catalyst portion (14) and a catalytically active component contained in the second catalyst portion (15) are of different types.