NOx Trap Layered PGM Loading for Sulfur Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
NOx traps in exhaust systems for internal combustion engines are prone to deactivation due to sulfur compounds, leading to shortened lifespan and reduced effectiveness over desulfation/NOx trap regeneration cycles.
Innovation Solution
A NOx trap with a substrate and three layers: a first layer comprising a platinum group metal, a NOx storage component, and a support; a second layer with the same NOx storage component and support; and a third layer with rhodium, where the platinum group metal loading in the first layer is 1 to 40 percent of the second layer, and all layers share the same NOx storage component and support, reducing deactivation during desulfation/NOx trap regeneration cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur compounds are present in the fuel, then the NOx trap can initially store and reduce NOx effectively, but the NOx trap becomes deactivated over desulfation/regeneration cycles leading to shortened lifespan
Solution Approach 1:
The NOx trap is divided into three distinct layers: a first layer with low PGM loading (1-40% of second layer), a second layer with high PGM loading, and a third layer with rhodium. This segmentation allows each layer to perform specific functions - the first layer acts as a sacrificial buffer that resists sulfur deactivation, protecting the more valuable second and third layers while maintaining overall trap reliability over multiple regeneration cycles
Solution Approach 2:
Different platinum group metal loadings are applied to different layers to create localized functional properties. The first layer has deliberately reduced PGM loading (1-40% of the second layer) to provide sulfur resistance, while the second and third layers maintain higher loadings for catalytic activity. This local quality variation optimizes the balance between sulfur tolerance and catalytic performance throughout the trap structure
2Object-affected harmful factors
If extreme temperatures (>650°C) are used for desulfation, then sulfur compounds can be removed from the NOx trap, but the extreme conditions cause longer term deactivation and shorten trap life
Solution Approach 1:
The first layer is pre-configured with low PGM loading (1-40% of the second layer) to act as a sacrificial buffer before sulfur deactivation occurs. This preliminary structural arrangement allows the trap to undergo multiple high-temperature desulfation cycles (>650°C) without the extreme conditions causing deactivation of the critical second and third layers, thereby extending trap lifespan while maintaining sulfur removal capability
Solution Approach 2:
The reduced PGM loading in the first layer creates a protective cushion against the harmful effects of extreme desulfation temperatures. This beforehand cushioning allows the trap to withstand repeated high-temperature regeneration cycles without cumulative damage to the catalytically active layers, resolving the contradiction between effective sulfur removal and trap longevity
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 NOx trap design significantly reduces deactivation and maintains higher NOx conversion efficiency and storage capacity over multiple desulfation and sulfation cycles, extending its operational life.
Implementation Method 1
nitric oxide reacts with oxygen to produce NO2 in the presence of the oxidation catalyst
Implementation Method 2
the NO2 is adsorbed by the NOx adsorbent in the form of an inorganic nitrate
Implementation Method 3
the stored inorganic nitrates decompose to form NO or NO2 which are then reduced to form N2 by reaction with carbon monoxide, hydrogen and/or hydrocarbons in the presence of the reduction catalyst
Implementation Method 4
sulfur dioxide is oxidized to sulfur trioxide over the oxidation catalyst
Implementation Method 5
the NOx adsorbent reacts with the sulfur trioxide to produce surface sulfates
Data Source
AI summary
A NOx trap, and its use in an exhaust system for internal combustion engines, is disclosed. The NOx trap comprises a substrate and three layers on the substrate. The first layer comprises a first platinum group metal, a first NOx storage component, and a first support; the second layer comprises a second platinum group metal, a second NOx storage component, and a second support; and the third layer comprises rhodium and a third support. The platinum group metal loading in the first layer is from 1 to 40 percent of the platinum group metal loading in the second layer. In addition, the first NOx storage component and the second NOx storage component are the same, and the first support and the second support are the same. The NOx trap is less prone to deactivation over numerous desulfation/NOx trap regeneration cycles.