Catalyst-Carrying Filter With Localized Pore Size Gradient
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Solution Overview
Problem
Catalyst-carrying filters used in internal combustion engines face challenges in effectively collecting and oxidizing particulate matter due to uneven pore sizes in the ceramic partition walls, leading to inefficient catalyst utilization and increased pressure loss, especially when installed under a vehicle floor where soot aggregates, causing clogging and incomplete combustion.
Innovation Solution
A catalyst-carrying filter design with a PM removal catalyst layer on the gas-inflow-side and a gas purification catalyst layer on the gas-outflow-side, featuring different average pore sizes and catalyst amounts to enhance particulate matter collection and oxidation, while preventing clogging and controlling regeneration temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the average pore size of the partition wall is small to ensure reliable collection of particulate matter, then particulate matter collection efficiency is improved, but most particulate matter is deposited on the surface of the partition wall and does not reach the inside of the pores, causing oxidizing catalyst underutilization and increased pressure loss
Solution Approach 1:
The partition wall is designed with different average pore sizes at different locations: the gas-inflow-side layer has a larger average pore size (5-20 μm) to facilitate particulate matter entry and catalyst contact, while the gas-outflow-side layer has a smaller average pore size (2-10 μm) to ensure reliable collection and prevent emission. This local differentiation resolves the contradiction by allowing efficient catalyst utilization at the inflow side while maintaining collection reliability at the outflow side.
2Quantity of substance
If the average pore size of the partition wall is large to allow particulate matter to reach the inside of the pores, then oxidizing catalyst utilization is improved, but particulate matter collection efficiency deteriorates and uncollected particulate matter is discharged to the atmosphere
Solution Approach 1:
The partition wall employs spatially varying pore sizes where the gas-inflow-side layer has larger pores (5-20 μm) to enable particulate matter penetration and catalyst contact, improving oxidizing catalyst utilization. The gas-outflow-side layer has smaller pores (2-10 μm) to act as a fine filter that captures remaining particulate matter before discharge, preventing harmful emissions. This local quality differentiation simultaneously achieves both objectives.
3Productivity
If the catalyst amount is increased to promote oxidation of particulate matter, then oxidation efficiency is improved, but regeneration temperature increases and catalyst cost increases
Solution Approach 1:
The oxidizing catalyst is distributed non-uniformly across the partition wall: the gas-inflow-side layer contains a higher catalyst amount (0.5-2.0 g/L) to promote oxidation reactions where particulate matter first contacts the catalyst, improving oxidation efficiency. The gas-outflow-side layer contains a lower catalyst amount (0.1-0.5 g/L) since particulate matter has already been largely collected. This local differentiation maintains high oxidation efficiency while reducing overall catalyst quantity and regeneration temperature requirements.
Solution Approach 2:
The catalyst amount is optimized within specific ranges (0.5-2.0 g/L for gas-inflow-side, 0.1-0.5 g/L for gas-outflow-side) to achieve effective oxidation without excessive temperature rise. These parameter specifications ensure sufficient oxidation activity while controlling regeneration temperature and cost.
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 filter achieves improved catalyst purification performance, reduced pressure loss, and enhanced emission control by ensuring efficient particulate matter removal and oxidation, even when installed under a vehicle floor, with a synergistic effect between the two catalyst layers.
Implementation Method 1
an oxidizing catalyst is supported on the surface of the partition wall of the honeycomb filter and the inner surface of the pores formed in the partition wall
Implementation Method 2
particulate matter contained in exhaust gas is collected by the partition wall when the exhaust gas passes through the partition wall
Data Source
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AI summary
A catalyst-carrying filter has a partition wall that includes a gas-inflow-side layer and a gas-outflow-side layer. One open end and the other open end of a plurality of cells are alternately plugged by plugging sections. The gas-inflow-side layer of the partition wall includes a PM removal catalyst layer that supports or is coated with an oxidizing catalyst for promoting oxidation of particulate matter contained in exhaust gas. The gas-outflow-side layer of the partition wall includes a PM collection layer that has a small average pore size so as to collect particulate matter, and a gas purification catalyst layer that supports or is coated with a gas purification catalyst that promotes oxidation of unburnt gas.