Segmented Washcoat Filter for Exhaust Poison Trapping
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Solution Overview
Problem
Positive ignition engines face challenges in maintaining stoichiometric exhaust gas composition for efficient three-way catalyst operation, leading to reduced NOx conversion efficiency and increased backpressure due to catalyst poisoning by fuel and lubricant-derived contaminants.
Innovation Solution
A high washcoat loading with a high specific surface area is applied to the inlet zone of a filter to trap incoming oil and residues, minimizing poison buildup and maintaining catalyst activity while reducing backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a three-way catalyst is used to convert NOx, CO and HC, then emission conversion efficiency is improved, but catalyst activity is reduced over time due to poisoning by fuel and lubricant contaminants
Solution Approach 1:
The washcoat is divided into multiple zones with different functions: an inlet zone with higher washcoat loading to trap poisons, and a catalytic zone with three-way catalyst composition for emission conversion. This segmentation allows the inlet zone to protect the catalytic zone from poisoning while maintaining conversion efficiency.
Solution Approach 2:
The inlet zone with higher washcoat loading performs preliminary trapping of catalyst poisons (oil and residues) before they reach the three-way catalyst. This preliminary action prevents the poisons from deactivating the catalyst sites, thereby maintaining long-term catalyst activity.
2Reliability
If washcoat loading is increased to trap catalyst poisons, then catalyst activity is maintained, but backpressure increases
Solution Approach 1:
Different zones of the washcoat have different properties: the inlet zone has higher washcoat loading for poison trapping, while the catalytic zone has optimized catalyst composition. This local differentiation allows high poison capacity without uniformly increasing backpressure across the entire filter.
Solution Approach 2:
By segmenting the washcoat into inlet and catalytic zones with different loadings, the design concentrates poison trapping capacity where it is most needed (at the inlet), preventing poisons from reaching and deactivating the catalyst while minimizing overall backpressure compared to uniform high loading.
3Productivity
If the filter is designed for high filtration efficiency, then particulate matter removal is improved, but backpressure increases
Solution Approach 1:
The substrate and washcoat utilize porous structures with optimized pore size distributions to enable efficient particulate filtration. The porous morphology allows high surface area for filtration while maintaining adequate flow channels to control backpressure.
Solution Approach 2:
The design addresses backpressure by optimizing the three-dimensional structure and pore distribution throughout the washcoat and substrate, creating efficient flow paths that reduce resistance while maintaining filtration efficiency through volumetric porosity rather than just surface area.
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 maintains catalyst activity and reduces backpressure by preferentially trapping poisons at the inlet, ensuring efficient particulate matter filtration and meeting emission standards.
Implementation Method 1
A high washcoat loading with a high specific surface area is applied to the inlet zone of a filter to trap incoming oil and residues
Implementation Method 2
TWCs are intended to catalyse three simultaneous reactions: (i) oxidation of carbon monoxide to carbon dioxide
Implementation Method 3
oxidation of unburned hydrocarbons to carbon dioxide and water
Implementation Method 4
reduction of nitrogen oxides to nitrogen and oxygen
Implementation Method 5
an oxygen storage component... The oxygen storage component that liberates or absorbs oxygen during the perturbations
Data Source
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AI summary
A catalysed filter for filtering particulate matter from exhaust gas comprising one or more catalyst poisons and emitted from a positive ignition internal combustion engine, which filter comprising a porous substrate having a total substrate length and having inlet surfaces and outlet surfaces, wherein the inlet surfaces are separated from the outlet surfaces by a porous structure containing pores of a first mean pore size, wherein the porous substrate is coated with a washcoat comprising a plurality of solid particles, wherein the porous structure of the washcoated porous substrate contains pores of a second mean pore size, wherein the second mean pore size is less than the first mean pore size, which washcoat being axially arranged on the porous substrate as a first zone comprising the inlet surfaces of a first substrate length less than the total substrate length and a second zone comprising the outlet surfaces of a second substrate length less than the total substrate length, wherein the sum of the substrate length in the first zone and the substrate length in the second zone ≥ 100%, wherein the washcoat of at least the second zone is a three-way catalyst washcoat comprising one or more precious metal supported on a high surface area base metal oxide, and an oxygen storage component, wherein: (i) a specific surface area of washcoat in the first zone > second zone; or (ii) both a washcoat loading and a specific surface area of washcoat in the first zone > second zone, and wherein (a) the washcoat of the first zone is also a three-way catalyst washcoat; or (b) the washcoat of the first zone is substantially precious metal free.