Axially Varying Precious Metal Catalyst for Thermal Stress
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Solution Overview
Problem
Exhaust gas cleaning catalysts face challenges with thermal damage and poisoning, particularly at the upstream end due to high temperatures and exposure to sulfur, lead, and phosphorous, leading to premature degradation.
Innovation Solution
A catalyst with a varying concentration profile of catalytically active components along the honeycomb carrier, where the upstream region has a low concentration of precious metals, peaking in the intermediate region and decreasing downstream, enhancing resistance to thermal stress and poisoning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the catalyst is placed nearer to the engine outlet to achieve early light-off, then the light-off temperature is improved, but thermal damage to the catalyst increases
Solution Approach 1:
The patent applies local quality by creating an axially varying precious metal concentration profile within the catalyst. The upstream region (exposed to highest temperatures) contains lower precious metal concentration while downstream regions contain higher concentrations. This spatial differentiation of material properties allows the catalyst to withstand thermal stress at the upstream end while maintaining high catalytic activity in downstream regions, thus resolving the contradiction between early light-off and thermal resistance.
2Productivity
If the upstream end of the catalyst is exposed to high temperatures and poisoning components, then catalytic activity is maintained, but poisoning resistance decreases
Solution Approach 1:
The patent implements local quality by varying the precious metal concentration along the catalyst axis. The upstream region, which experiences the highest exposure to poisoning components like sulfur, lead, and phosphorous, is designed with lower precious metal concentration to reduce susceptibility to poisoning. Downstream regions with lower temperature exposure contain higher precious metal concentrations to maintain catalytic activity. This spatial distribution resolves the contradiction between maintaining catalytic activity and resisting poisoning.
3Ease of manufacture
If uniform precious metal concentration is used throughout the catalyst, then manufacturing is simplified, but thermal damage and poisoning occur more severely at the upstream end
Solution Approach 1:
The patent applies parameter changes by systematically varying the precious metal concentration parameter along the axial direction of the catalyst. Instead of using a uniform concentration, the design implements a gradient where concentration increases from the upstream end to the downstream end. This parameter variation optimizes both thermal resistance at the upstream end and catalytic activity in downstream regions, resolving the contradiction between manufacturing simplicity and performance reliability.
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 improves the catalyst's resistance to thermal aging and poisoning, maintaining catalytic activity over a longer lifespan and reducing the impact of high temperatures and poisoning components, making it suitable for close-coupled applications near the engine outlet.
Implementation Method 1
Three-way catalysts are primarily used to convert the pollutants carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) contained in the exhaust gas of internal combustion engines into harmless substances
Data Source
AI summary
The present invention relates to an exhaust gas cleaning catalyst comprising on a honeycomb carrier a catalytic coating. Said honeycomb carrier has an upstream end and a downstream end and a plurality of flow channels are running from the upstream end to the downstream end. The catalytic coating comprises catalytically active precious metal components of which at least one component exhibits a concentration profile along the honeycomb carrier starting with a low concentration at the upstream end which increases along the flow channels up to a maximum value and then decreases again to the downstream end.