Catalytic Wall-Flow Filter with Dual TWC Coatings for Emission Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gasoline particulate filters (GPFs) face challenges in maintaining efficient conversion of CO, NOx, and HC emissions due to transient air-to-fuel ratio fluctuations in gasoline engines, leading to inefficiencies in three-way catalyst (TWC) performance and increased back-pressure, while also requiring a cost-effective balance of performance and cost.
Innovation Solution
A catalytic wall-flow filter with dual TWC coatings, comprising different platinum group metals (PGMs) and oxygen storage capacity (OSC) materials on opposing faces, optimized for stoichiometric exhaust gas composition management, is employed to enhance emission treatment efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single TWC coating is used in a GPF, then the structure is simpler and cost is lower, but the conversion efficiency of CO, NOx and HC is insufficient under transient air-to-fuel ratio conditions
Solution Approach 1:
The single TWC coating is segmented into two distinct coatings with different PGM compositions and OSC materials, positioned in different zones of the filter. This segmentation allows each coating to specialize in specific emission conversion tasks, improving overall reliability under transient conditions while maintaining a manageable structural complexity through zoned functionality.
Solution Approach 2:
Different regions of the filter are assigned different coating qualities - the first TWC coating contains specific PGM ratios optimized for certain emissions, while the second coating contains different PGM ratios optimized for other emissions. This local quality differentiation ensures that each region contributes optimally to the overall conversion efficiency under varying air-to-fuel ratio conditions.
2Reliability
If the air-to-fuel ratio is controlled to maintain stoichiometric composition, then TWC conversion efficiency is maximized, but the system becomes sensitive to transient load changes and requires complex control
Solution Approach 1:
The dual TWC coating system introduces dynamic adaptability by having different PGM compositions and OSC materials that respond differently to transient air-to-fuel ratio changes. When the ratio fluctuates, one coating may maintain optimal performance while the other compensates, allowing the system to adapt to transient load conditions without requiring complex control mechanisms.
Solution Approach 2:
The system changes the chemical parameters of the catalyst coatings by using different PGM ratios and OSC materials in each coating. This parameter differentiation allows the catalyst system to maintain effective conversion across a broader range of air-to-fuel ratio conditions, reducing sensitivity to transient changes while maintaining high conversion efficiency.
3Reliability
If a TWC coating is applied on a filter body, then emission conversion is improved, but back-pressure increases unduly
Solution Approach 1:
The TWC coating is segmented into two separate coatings applied in different zones of the filter body. This segmentation distributes the catalytic activity more evenly, preventing excessive back-pressure buildup in any single region while maintaining effective emission conversion across the entire filter.
Solution Approach 2:
Different local regions of the filter are assigned different coating properties and thicknesses optimized for their specific flow conditions. This local quality approach ensures that emission conversion is maximized where needed while minimizing back-pressure increases in regions where flow resistance would be most problematic.
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 dual-coated catalytic wall-flow filter effectively reduces HC, CO, and particulate emissions by stabilizing exhaust gas composition, improving conversion efficiency and reducing back-pressure, while maintaining cost-effectiveness.
Implementation Method 1
a first TWC coating in a first plurality of channels, the first TWC coating comprising a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support; a second TWC coating in a second plurality of channels, the second TWC coating comprising a second PGM composition, a second OSC material, and a second inorganic support
Implementation Method 2
oxidation of carbon monoxide to carbon dioxide, oxidation of unburned hydrocarbons to carbon dioxide and water
Implementation Method 3
reduction of nitrogen oxides to nitrogen and oxygen
Implementation Method 4
an oxygen storage capacity (OSC) material
Implementation Method 5
a first oxygen storage capacity (OSC) material, and a second oxygen storage capacity (OSC) material
Data Source
AI summary
A catalytic wall-flow filter for exhaust gas from a gasoline engine is disclosed. The catalytic wall-flow filter comprises a wall-flow filter substrate having porous walls and a first face and a second face defining a longitudinal direction therebetween and first and second pluralities of channels extending in the longitudinal direction. The first plurality of channels is open at the first face and closed at the second face, and the second plurality of channels is open at the second face and closed at the first face. The filter comprises a first TWC coating comprising a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support; and a second TWC coating comprising a second PGM composition, a second OSC material, and a second inorganic support.