Wall-Flow Catalyst Density Ratio for OSC and Pressure Loss
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Solution Overview
Problem
Conventional wall-flow-type exhaust gas purification catalysts face challenges in maintaining oxygen storage capacity (OSC) while minimizing pressure loss, often requiring increased OSC material content which increases pressure loss, and the configuration of catalytic layers can make the partition wall less permeable to exhaust gas.
Innovation Solution
A wall-flow-type exhaust gas purification catalyst with a substrate and two catalytic layers, where the first layer is internal to the entrance cell and the second layer is internal to the exit cell, both comprising oxygen storage materials, with a coating density ratio between 1.1 and 1.8, and substrate-exposing segments to adjust exhaust gas flow, ensuring increased OSC without compromising permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the OSC material content is increased to compensate for decreased oxygen storage rate, then the oxygen storage capacity (OSC) increases, but the pressure loss increases
Solution Approach 1:
The patent applies local quality by creating non-uniform catalytic layer distributions within the partition wall. The first catalytic layer is positioned in the upstream portion with higher coating density to enhance oxygen storage where exhaust gas first contacts the wall, while the downstream portion has reduced or no catalytic layer to maintain permeability and reduce pressure loss. This spatial differentiation allows the system to concentrate OSC functionality where most needed while preserving flow characteristics in downstream regions.
Solution Approach 2:
The patent segments the partition wall into multiple regions with different catalytic layer configurations. The partition wall is divided into an upstream portion containing the first catalytic layer and a downstream portion with the second catalytic layer or substrate-exposing segments. This segmentation allows independent optimization of each region - the upstream portion maximizes oxygen storage capacity while the downstream portion minimizes flow resistance, thereby resolving the contradiction between OSC and pressure loss.
2Reliability
If the catalytic layer covers the entire surface of the partition wall to maximize catalytic activity, then the purification performance improves, but the partition wall becomes less permeable to exhaust gas
Solution Approach 1:
The patent implements local quality by applying catalytic layers selectively to specific regions of the partition wall rather than uniformly across the entire surface. The first catalytic layer is applied to the upstream portion where exhaust gas initially contacts the wall, providing sufficient catalytic activity for purification. The downstream portion has reduced catalytic coverage or substrate-exposing segments that maintain high permeability. This localized approach ensures adequate purification performance while preserving exhaust gas flow through the partition wall.
Solution Approach 2:
The patent segments the partition wall surface into distinct zones with different catalytic layer configurations. The upstream portion receives the first catalytic layer for effective purification, while the downstream portion has the second catalytic layer with reduced coverage or no coverage in substrate-exposing segments. This segmentation allows the system to concentrate catalytic functionality where exhaust gas first interacts with the wall, maintaining permeability in downstream regions where full catalytic coverage is less critical.
3Ease of manufacture
If the catalytic metal content is reduced to lower manufacturing costs, then the manufacturing cost decreases, but the oxygen storage rate of the OSC material significantly decreases
Solution Approach 1:
The patent applies local quality by concentrating catalytic metal in the upstream portion of the partition wall where the first catalytic layer is positioned. This region experiences the highest concentration of exhaust gas and requires the most catalytic activity for oxygen storage. By limiting catalytic metal to this upstream zone rather than distributing it throughout the entire partition wall, the system reduces overall metal content and manufacturing cost while maintaining sufficient oxygen storage rate in the critical upstream region.
Solution Approach 2:
The patent segments the catalytic metal distribution into upstream and downstream portions. The first catalytic layer in the upstream portion contains catalytic metal at levels optimized for oxygen storage, while the downstream portion has reduced or no catalytic metal. This segmentation allows cost reduction by eliminating unnecessary catalytic metal in downstream regions where its contribution to oxygen storage is minimal, while preserving adequate oxygen storage rate in the upstream region where catalytic activity is most needed.
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 enhances oxygen storage capacity and purification performance while reducing pressure loss, allowing for effective exhaust gas purification even with reduced catalytic metal content.
Implementation Method 1
the OSC material works to store oxygen in the exhaust gas when the exhaust gas is at a lean air-fuel ratio (i.e. in an excess of oxygen) and to release oxygen when the exhaust gas is at a rich air-fuel ratio
Implementation Method 2
upon contact between the exhaust gas and the catalytic layer (catalytic metal), the toxic components are purified (detoxified)
Data Source
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AI summary
Provided is a wall-flow-type exhaust gas purification catalyst with an oxygen storage material that has an increased OSC and exhibits its OSC without a compromise. This invention provides an exhaust gas purification catalyst 10 comprising a wall-flow-type substrate, a first catalytic layer 261 and a second catalytic layer 262. The first catalytic layer 261 is provided to an internal portion of a partition wall 26 in contact with an entrance cell 24. The second catalytic layer 262 is provided to an internal portion of a partition wall 26 in contact with an exit cell 25. Each of the first and second catalytic layers 261 and 262 comprises an oxygen storage material. The ratio (D1/D2) of the coating density D1 of the first catalytic layer 261 to the coating density D2 of the second catalytic layer 262 is 1.1 to 1.8.