Wall-Flow Catalyst Coating Structure for Pressure Loss and NOx Purification
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Solution Overview
Problem
Conventional wall-flow-type exhaust gas purification catalysts face challenges in balancing pressure loss reduction with enhanced purification performance, particularly due to the distribution and density of catalytic layers affecting exhaust gas contact and accumulation of particulate matter.
Innovation Solution
The catalyst design incorporates two catalytic layers within the partition wall, with specific density distributions and substrate-exposing segments to optimize exhaust gas flow, reducing pressure loss while enhancing purification performance, especially for NOx.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coating densities of the catalytic layers are increased to enhance exhaust gas purification performance, then the purification performance is improved, but the pressure loss increases
Solution Approach 1:
The patent applies local quality by creating non-uniform catalytic layer distribution within the partition wall. The first catalytic layer is positioned closer to the exhaust inlet side while the second catalytic layer is positioned closer to the exhaust outlet side, with their coating densities varying at different locations along the flow direction. This localized differentiation allows optimal contact between exhaust gas and catalytic metals at different stages of the purification process, enhancing overall purification performance while managing pressure loss through strategic placement rather than uniform high-density coating throughout.
2Reliability
If the catalytic layers are placed to cover the entire surface of the partition wall to maximize contact with exhaust gas, then the purification performance is enhanced, but the pressure loss increases and combustion engine power is reduced
Solution Approach 1:
The patent segments the catalytic layer into two distinct layers positioned at different locations within the partition wall thickness. The first catalytic layer is formed in the interior of the partition wall closer to the exhaust inlet side, while the second catalytic layer is formed closer to the exhaust outlet side. This segmentation allows each layer to handle different aspects of exhaust gas purification at appropriate stages, reducing the need for complete surface coverage and thereby minimizing pressure loss while maintaining effective purification performance.
3Duration of action of stationary object
If the catalytic layers are positioned to inhibit sintering of catalytic metals, then the durability is improved, but the pressure loss increases
Solution Approach 1:
The patent employs a nested structure where two catalytic layers are positioned within the interior of the partition wall at different depths. The first catalytic layer is nested closer to the exhaust inlet side and the second catalytic layer is nested closer to the exhaust outlet side, both within the partition wall thickness. This nested arrangement protects the catalytic metals from direct exposure to harsh exhaust conditions that cause sintering, improving durability, while the strategic positioning within the wall structure minimizes the impact on exhaust gas flow and 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
This design effectively reduces pressure loss and improves purification performance, particularly for NOx, by ensuring adequate contact of exhaust gases with catalytic layers and minimizing particulate matter accumulation, suitable for use in eco-friendly vehicles with varying exhaust temperatures.
Implementation Method 1
upon contact between the exhaust gas and the catalytic layer (catalytic metal), the exhaust gas components are purified (detoxified)
Data Source
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AI summary
Provided is an exhaust gas purification catalyst that combines reduction of pressure loss and enhancement of purification performance. This invention provides an exhaust gas purification catalyst 10 comprising a wall-flow-type substrate and first and second catalytic layers 261 and 262. The first catalytic layer 261 is provided to the interior of a partition wall 26, in contact with an entrance cell 24, from an exhaust inlet-side end 24a in the running direction, having a length L1 less than Lw. The second catalytic layer 262 is provided to the interior of a partition wall 26, in contact with an exit cell 25, from an exhaust outlet-side end 25a in the running direction, having a length L2 less than Lw. An internal portion of partition wall 26 in contact with entrance cell 24 has a substrate-exposing segment 26N1 near the exhaust outlet-side end 25a.