Wall-Flow Catalyst Layer Layout for Low-Temperature Exhaust Purification
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Solution Overview
Problem
Exhaust gas purification catalysts in internal combustion engines suffer from reduced purification performance at low temperatures immediately after engine startup, necessitating improved catalyst configurations to enhance performance in low-temperature conditions.
Innovation Solution
The catalyst system comprises a first catalyst layer on the surface of the partition wall and a second catalyst layer inside the partition wall, with specific length and thickness ratios, allowing for enhanced contact between exhaust gas and catalysts, particularly in gasoline engines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single catalyst layer configuration is used, then the structure is simple, but the purification performance at low temperatures is insufficient
Solution Approach 1:
The catalyst layer is divided into two distinct layers: a first catalyst layer containing Pd and a second catalyst layer containing Rh. This segmentation allows each layer to perform specific purification functions, with the first layer providing initial purification and the second layer enhancing low-temperature performance, thereby resolving the contradiction between maintaining simple structure and improving purification reliability.
Solution Approach 2:
Different catalyst materials are distributed at different locations within the partition wall structure. The first catalyst layer is positioned in a specific region while the second catalyst layer is positioned in another region, creating local quality variations that optimize purification performance at different stages of exhaust gas flow, thus improving overall purification reliability without uniformly complicating the entire structure.
2Reliability
If the catalyst layer length is increased to improve purification performance, then the purification efficiency increases, but the pressure loss increases
Solution Approach 1:
The first catalyst layer is designed with a length that extends beyond the second catalyst layer in the exhaust gas flow direction. This partial extension allows the first catalyst layer to provide additional purification action for exhaust gas that passes through the second layer, achieving excessive action that maximizes purification performance while controlling pressure loss by not uniformly extending all layers throughout the entire partition wall length.
Solution Approach 2:
The catalyst layers are segmented into different lengths along the exhaust gas flow direction, with the first catalyst layer extending further than the second catalyst layer. This segmentation creates a staged purification approach where each layer contributes to purification at different flow stages, optimizing the balance between purification efficiency and pressure loss by avoiding unnecessary extension of all layers.
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 improves purification performance, specifically warm-up properties, while reducing pressure loss and enhancing NOx purification efficiency.
Implementation Method 1
a first catalyst layer which contains a first catalyst and is provided on a surface of the partition wall, on the side of the inlet cells, and a second catalyst layer which contains a second catalyst and is provided inside the partition wall
Implementation Method 2
exhaust gas that flows in through cell inlets passes through a porous cell partition wall that partitions the cells, and is discharged out to the cell outlets. As the exhaust gas passes through the porous cell partition wall, the particulate matter becomes trapped within the pores inside the partition wall
Data Source
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AI summary
Provided is an exhaust gas purification catalyst that allows enhancing purification performance on exhaust gas. The exhaust gas purification catalyst according to the present invention has a substrate 10 of wall flow structure having a porous partition wall 16 which partitions inlet cells 12 and outlet cells 14, a first catalyst layer 20 formed on the surface of the partition wall 16, on the side facing the inlet cells 12, and a second catalyst layer 30 formed in the interior of the partition wall 16, at least in a region facing the outlet cells 14.