In-wall Catalyst Filter with Low Void Occupancy
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Solution Overview
Problem
The existing wall-flow filters with on-wall catalyst coating methods experience reduced PM trapping efficiency and oxidation efficiency due to excessive catalytic substance coating, leading to decreased porosity and clogging issues, while in-wall type filters have low PM trapping efficiency without catalyst support.
Innovation Solution
A filter design with a base material and catalytic substance where the catalytic substance's void occupancy is 10% or less within the partition walls' pores, and the mean particle size is 1/10 of the pore size, with a concentration ratio of 10/90 to 90/10 between the gas inflow and outflow ends, and a porosity of 40% to 70%, incorporating Pt and Pd in a 1:1 to 10:1 ratio, and optionally including oxygen storage materials or perovskite materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excessive amount of catalytic substance is coated in in-wall type filter, then catalyst treatment efficiency is improved, but porosity of partition walls decreases and PM trapping efficiency is reduced
Solution Approach 1:
The patent specifies precise parameter ranges: void occupancy of catalytic substance is 10% or less, mean particle size D50 of catalyst is 1/10 or less of mean pore size D50 of partition walls, and porosity of base material is 40% to 70%. These parameter controls ensure both catalyst efficiency and porosity maintenance
Solution Approach 2:
The patent uses porous base material with controlled porosity (40%-70%) and specifies that catalytic substance should occupy 10% or less of the void space within pores. This maintains the porous structure necessary for PM trapping while providing sufficient catalyst for treatment
2Reliability
If catalytic substance is coated on partition walls, then catalyst treatment efficiency is improved, but PM trapping efficiency is reduced due to porosity decrease
Solution Approach 1:
The patent establishes critical parameter thresholds: void occupancy ≤10% and particle size ratio (catalyst/pore) ≤1/10. These parameters ensure catalyst coating does not significantly reduce porosity, maintaining both treatment efficiency and PM trapping efficiency
Solution Approach 2:
The patent specifies base material porosity should be 40%-70% and catalytic substance void occupancy 10% or less. This preserves the porous structure needed for PM trapping while enabling catalyst function
3Productivity
If wall-flow filter structure with alternately closed cell ends is used, then PM trapping efficiency is improved, but forced regeneration control becomes necessary due to clogging
Solution Approach 1:
The patent applies different properties to different locations: catalytic substance concentration ratio between inflow and outflow ends is controlled between 10/90 and 90/10, creating local optimization that prevents complete clogging while maintaining PM trapping efficiency
Solution Approach 2:
The patent specifies that end portions of at least some cells should be closed off (wall-flow structure) but controls catalytic substance distribution to prevent complete blockage, eliminating need for forced regeneration
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 maintains high PM trapping efficiency and catalyst treatment efficiency without pressure loss, preventing clogging and ensuring effective PM oxidation.
Implementation Method 1
a catalytic substance provided within the base material... maintain high treatment efficiency afforded by the catalyst... ensuring effective PM oxidation
Implementation Method 2
there is also a reduction in PM oxidation efficiency afforded by the catalyst... ensuring effective PM oxidation
Data Source
AI summary
The present invention provides a filter comprising a base material and a catalytic substance provided within the base material, wherein the base material comprises a plurality of cells forming gas flow paths and having a gas inflow-side end portion and outflow-side end portion, and a plurality of porous partition walls defining said cells, the end portions of at least some of the cells being closed off, and the void occupancy of the catalytic substance within the pores of the partition walls is 10% or less.