Wall-Flow Filter Coating for Soot Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing particulate filters face challenges in optimizing both catalytic activity and filtration efficiency while minimizing exhaust-gas back pressure and improving soot combustion properties.
Innovation Solution
A wall-flow filter with a coating comprising a particulate metal compound that catalyzes soot oxidation, applied in the porous walls and/or on the surfaces of the filter, but not on the outlet channels, to enhance filtration efficiency and catalytic activity without significantly increasing back pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalytically active coating is applied to the channel walls of a wall-flow filter, then catalytic effectiveness is improved, but exhaust-gas back pressure increases
Solution Approach 1:
The patent applies catalytically active material selectively in specific locations: within the porous walls and on inlet channel surfaces, but deliberately excludes outlet channels. This localized application provides catalytic functionality where needed (for soot oxidation during filtration) while avoiding back pressure increases that would result from coating outlet channels where exhaust gas flows most rapidly.
Solution Approach 2:
The patent transitions from traditional on-wall coating (two-dimensional surface application) to in-wall coating (three-dimensional incorporation within porous structure). By embedding catalytic material within the porous walls, the patent achieves catalytic activity throughout the filtration path without creating a continuous surface layer that would impede gas flow and increase back pressure.
2Stress or pressure
If the amount of oxidic support materials for catalytic noble metals is reduced in a filter, then exhaust-gas back pressure is minimized, but catalytic effectiveness deteriorates
Solution Approach 1:
The patent utilizes the porous structure of the wall-flow filter substrate as the primary carrier for catalytic material. The porous walls provide extensive internal surface area and volume for catalytic activity without requiring additional oxidic support materials that would increase back pressure. The pore structure naturally accommodates catalytic particles while maintaining gas flow pathways.
Solution Approach 2:
The patent creates a composite structure by combining the porous ceramic wall material with dispersed catalytically active particles. This composite approach integrates structural and catalytic functions within the same component, eliminating the need for separate oxidic support layers and reducing overall material quantity while maintaining or enhancing catalytic effectiveness.
3Stress or pressure
If catalytically active material is dispersed within the porous walls instead of coated on surface, then exhaust-gas back pressure is reduced, but the amount of catalytic substance is limited by absorption capacity
Solution Approach 1:
The patent makes the porous walls serve dual functions: as the structural filtration medium and as the carrier for catalytic material. The same porous structure that enables particle filtration also provides the matrix for catalytic particle dispersion, eliminating the need for separate support materials and maximizing the utilization of available pore volume for catalytic purposes.
Solution Approach 2:
The patent changes the physical state and distribution parameters of catalytic material from surface-coated layers to internally dispersed particles within the porous matrix. This parameter change from two-dimensional surface coverage to three-dimensional volumetric distribution increases the effective capacity for catalytic substance while maintaining pore openness and minimizing back pressure.
4Reliability
If a filtration layer is created on the inlet channel walls, then filtration efficiency is improved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The patent merges the filtration function and catalytic function into a single integrated structure. The porous walls perform both physical filtration of particles and catalytic oxidation of soot, while the inlet channel surfaces provide both flow distribution and additional catalytic activity. This consolidation eliminates the need for separate filtration layers and reduces overall system complexity.
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 solution achieves improved filtration efficiency and catalytic activity for soot combustion, with a moderate increase in exhaust-gas back pressure, thereby addressing the limitations of existing filters.
Implementation Method 1
the coating F being located in the porous walls and/or on the surfaces OE, but not on the surfaces OA, and comprising a particulate metal compound and no noble metal, characterized in that the particulate metal compound catalyzes the oxidation of soot
Implementation Method 2
a wall-flow filter for removing particles from the exhaust gas of combustion engines, comprising a wall-flow filter substrate of length L and a coating F, the wall-flow filter substrate having channels E and A, which extend in parallel between a first and a second end of the wall-flow filter substrate, are separated by porous walls
Data Source
AI summary
The invention relates to a wall flow filter for removing particulate matter from the exhaust of internal combustion engines, comprising a wall flow filter substrate having a length L, and a coating F, the wall flow filter substrate being provided with channels E and A which run parallel between a first end and a second end of the wall flow filter substrate, separated by porous walls, and forming surfaces OE and OA. Channels OE are closed at the second end and channels A are closed at the first end. Coating F is disposed in the porous walls and/or on surfaces OE, but not on surfaces OA, and comprises a particulate metal compound and no precious metal, characterised in that the particulate metal compound catalyses the oxidation of soot.