Zoned Three-Way Catalyst Reducing Platinum Poisoning
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Solution Overview
Problem
Three-way catalysts for combustion engines face challenges due to high costs of platinum group metals and poisoning mechanisms that deplete active components, particularly at the inlet region of monoliths, leading to reduced performance and increased emissions as engines become more efficient and operate under stricter fuel economy standards.
Innovation Solution
A catalyst design with two washcoat zones on the carrier substrate, where the first platinum group metal is distributed uniformly across the full length and the second platinum group metal is concentrated in a shorter zone located away from the inlet, reducing poisoning effects while maintaining improved light-off performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum group metals are concentrated in the inlet region of the monolith to improve light-off performance, then cold start performance is improved, but the catalyst becomes more susceptible to poisoning by contaminants that deposit preferentially at the inlet
Solution Approach 1:
The patent applies local quality by creating distinct zones with different platinum group metal concentrations at different positions along the monolith. The inlet region has lower PGM concentration to reduce poisoning susceptibility, while downstream regions have higher concentrations to maintain catalytic activity where exhaust gases are cleaner.
Solution Approach 2:
The catalyst monolith is segmented into multiple zones along its length, with each zone having different PGM concentrations. This segmentation allows the inlet zone to be protected from poisoning while downstream zones handle the main catalytic conversion functions.
2Reliability
If platinum group metals are distributed uniformly throughout the monolith to ensure consistent catalytic activity, then catalytic performance is maintained, but the cost of the catalyst increases significantly
Solution Approach 1:
Instead of uniform distribution, the patent implements local quality variations where PGM concentrations are tailored to specific zones. High PGM concentrations are placed only where needed for catalytic activity (downstream regions), while low concentrations are used in regions susceptible to poisoning (inlet region), thereby reducing total PGM content while maintaining performance.
Solution Approach 2:
The patent changes the concentration parameter of platinum group metals along the length of the monolith, creating a gradient or zoned distribution rather than uniform concentration. This parameter variation optimizes both performance and cost by placing expensive materials only where necessary.
3Temperature
If the monolith size is reduced and cell density is increased to place the catalyst closer to the engine manifold, then light-off temperature is reduced and cold start performance is improved, but the catalyst is more exposed to poisoning contaminants
Solution Approach 1:
The patent compensates for the increased contaminant exposure in close-coupled applications by creating a protected inlet zone with lower PGM concentration. This local quality adjustment allows the monolith to be positioned close to the manifold (benefiting from high temperature) while the zoned structure protects against the concomitant increase in poisoning risk.
4Temperature
If high concentrations of platinum group metals are used to achieve significant performance improvements, then light-off performance is improved by 100°C, but the cost of the catalyst increases dramatically
Solution Approach 1:
The patent optimizes the PGM concentration parameter by creating zones of different concentrations rather than using uniformly high concentrations throughout. This allows achieving adequate light-off performance with lower total PGM content by strategically placing higher concentrations only in downstream zones where they are most effective.
Solution Approach 2:
High PGM concentrations are applied locally in downstream regions where catalytic activity is most needed, rather than uniformly throughout the entire monolith. This local quality approach achieves performance improvements while minimizing the total quantity of expensive PGMs required.
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 design enhances catalyst performance by minimizing poisoning and maintaining efficient emissions control, even under conditions of increased engine efficiency and stricter emissions regulations, by strategically placing platinum group metals to avoid deactivation mechanisms.
Implementation Method 1
such catalysts comprise as catalytically active material one or more platinum group metals, in particular platinum, palladium and/or rhodium
Implementation Method 2
mainly NOx is reduced to nitrogen using e.g. CO as a reducing agent
Implementation Method 3
oxygen storage component (OSCs) in the form of cerium-zirconium mixed oxides were included in its formulation
Data Source
AI summary
The present invention relates to a catalyst comprising a carrier substrate of the length L extending between substrate ends a and b and two washcoat zones A and B, wherein washcoat zone A comprises a first platinum group metal and extends starting from substrate end a over a part of the length L, and washcoat zone B comprises the same components as washcoat zone A and in addition a second platinum group metal and extends from substrate end b over a part of the length L, wherein L=LA+LB, wherein LA is the length of washcoat zone A and LB is the length of substrate length B.