Dual-Coated Wall Flow Filter for Exhaust Emission Control
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Solution Overview
Problem
Current exhaust gas cleaning technologies for stoichiometrically operated combustion engines are inadequate in effectively removing extremely fine particles, carbon monoxide, hydrocarbons, and nitrogen oxides, particularly due to the stringent EU-6c emission standards and the need for a combined particulate filter and three-way catalytic converter functionality.
Innovation Solution
A catalytically active particulate filter with a wall flow design featuring two different three-way catalytically active coatings, Y and Z, applied on the surfaces of channels E and A respectively, extending from 51 to 90% of the filter's length, utilizing precious metals like palladium and rhodium with specific weight ratios and oxygen storage components, and carrier materials like lanthanum-stabilized aluminum oxide, to enhance catalytic activity and reduce back pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wall flow filters with catalytic coatings are used to remove particles, then particle removal efficiency is improved, but the filter complexity and manufacturing difficulty increase due to the need for dual coatings with specific spatial distribution
Solution Approach 1:
The filter is divided into functionally distinct zones: channels E with coating Y for particle capture and oxidation, and channels A with coating Z for three-way catalysis. This segmentation allows each coating to be optimized for its specific function while working together to solve the particle removal problem.
Solution Approach 2:
Different catalytic coatings are applied to different locations within the filter structure. Coating Y is applied to channels E where particle oxidation is needed, while coating Z is applied to channels A for three-way catalysis, creating local functional differentiation that resolves the contradiction between effectiveness and complexity.
2Reliability
If dual catalytic coatings are applied to enhance three-way catalytic activity, then CO and NOx conversion is improved, but the manufacturing precision requirements increase due to the need for specific coating lengths and distributions
Solution Approach 1:
The coatings extend over 51-90% of the filter length rather than requiring precise full coverage. This partial action approach provides a tolerance range that simplifies manufacturing while still achieving the necessary catalytic performance for CO and NOx conversion.
Solution Approach 2:
The invention specifies a range (51-90% of filter length) for coating extension rather than a fixed value, allowing manufacturing flexibility. This parameter change from a strict specification to a range specification reduces manufacturing precision requirements while maintaining effectiveness.
3Reliability
If catalytic coatings are applied to reduce soot ignition temperature, then particle oxidation is improved, but the precious metal content and cost increase
Solution Approach 1:
The precious metal catalyst is segmented into two different coatings applied to different channels. This segmentation allows optimization of metal distribution, placing catalysts where they are most needed for particle oxidation and three-way catalysis, thereby reducing overall precious metal content while maintaining effectiveness.
Solution Approach 2:
The filter uses composite catalytic structures with different materials in different channels. Coating Y and coating Z contain different catalyst compositions optimized for their specific functions, creating a composite system that achieves superior particle oxidation and three-way catalysis with reduced total precious metal content compared to uniform coating.
4Reliability
If the filter is designed to meet future emission limits, then compliance with EU-6c standards is improved, but the device complexity increases due to the need for combined particulate filter and three-way catalytic converter functionality
Solution Approach 1:
The invention merges the particulate filter function and three-way catalytic converter function into a single integrated device. Channels E with coating Y handle particle capture and oxidation, while channels A with coating Z handle CO and NOx conversion, combining multiple emission control functions in one component to meet EU-6c standards.
Solution Approach 2:
The filter structure is designed with multi-functionality, where the same physical structure (wall flow filter) performs both particle filtration and three-way catalysis. The dual-coating system enables the device to universally address multiple pollutant types (particles, CO, NOx) simultaneously, simplifying the overall exhaust aftertreatment system while meeting future emission limits.
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 effectively removes particles, carbon monoxide, hydrocarbons, and nitrogen oxides, improving light-off behavior and dynamic CO/NOx conversion while maintaining low exhaust back pressure, thus adhering to future emission limits and optimizing filter performance.
Implementation Method 1
the wall flow filter is, for example, provided with catalytically active coatings that reduce the ignition temperature of soot
Implementation Method 2
the particles retained in this manner must then be burnt off or oxidized
Implementation Method 3
two different three-way catalytically active coatings, Y and Z... effectively removes particles, carbon monoxide, hydrocarbons, and nitrogen oxides
Implementation Method 4
capable of simultaneously converting the three major gaseous pollutants of the engine, namely hydrocarbons, carbon monoxide and nitrogen oxides, into harmless components
Implementation Method 5
exhaust gas flowing into channels A can only leave the filter via channels B, and must flow through the porous walls between channels A and B for this purpose. When the exhaust gas passes through the wall, the particles are retained
Implementation Method 6
flow through the porous walls between channels A and B
Data Source
AI summary
The present invention relates to a particulate filter which comprises a wall flow filter of length L and two different catalytically active coatings Y and Z, wherein the wall flow filter comprises channels E and A that extend in parallel between a first and a second end of the wall flow filter and are separated by porous walls which form the surfaces OE and OA, respectively, and wherein the channels E are closed at the second end and the channels A are closed at the first end. The invention is characterized in that the coating Y is located in the channels E on the surfaces OE and the coating Z is located in the channels A on the surfaces OA.