NOx Storage Catalyst Thermal Aging Stability
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Solution Overview
Problem
Nitrogen oxide storage catalysts used in close-coupled positions for gasoline engines with direct gasoline injection, operated predominantly with a lean air/fuel mixture, suffer from thermal aging issues, leading to reduced performance and increased platinum content requirements, which are costly and inefficient.
Innovation Solution
A nitrogen oxide storage catalyst composition utilizing a homogeneous magnesium-aluminum mixed oxide with a molar ratio of MgO:Al2O3 at 1.1:1 as a support material, combined with a reduced platinum content and a three-way catalytic converter coating, enhances thermal aging stability and reduces platinum usage by 20-80% without compromising denoxing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitrogen oxide storage catalysts are used in close-coupled positions, then they can store nitrogen oxides under lean operating conditions, but they suffer from thermal aging issues that reduce performance and require increased platinum content
Solution Approach 1:
The patent changes the chemical composition parameters of the support material by using a homogeneous magnesium-aluminum mixed oxide with a specific molar ratio (MgO:Al2O3 = 1.1:1). This parameter change in the support material's stoichiometry improves thermal aging stability and allows for reduced platinum content while maintaining catalytic performance.
Solution Approach 2:
The patent employs a composite material system consisting of a homogeneous magnesium-aluminum mixed oxide support combined with nitrogen oxide storage components (such as barium, strontium, or calcium compounds) and reduced platinum content. This composite structure provides both thermal stability and catalytic activity without requiring high platinum loads.
2Quantity of substance
If the platinum content is reduced to lower costs, then noble metal costs decrease, but the thermal aging stability and denoxing efficiency may be compromised
Solution Approach 1:
The patent optimizes the platinum content parameter to a reduced range (0.8-1.2 g/l) while compensating for the lower noble metal quantity by optimizing the support material composition (magnesium-aluminum mixed oxide with MgO:Al2O3 ratio of 1.1:1) and nitrogen oxide storage component loading, thereby maintaining denoxing efficiency at lower costs.
3Temperature
If high exhaust gas temperatures are encountered, then the close-coupled position provides good access to exhaust heat, but thermal aging accelerates and reduces catalyst performance
Solution Approach 1:
The patent changes the thermal stability parameters of the catalyst by selecting a magnesium-aluminum mixed oxide support with a specific molar ratio (1.1:1) that exhibits enhanced resistance to thermal aging. This parameter optimization allows the catalyst to withstand high exhaust gas temperatures in the close-coupled position without significant performance degradation.
Solution Approach 2:
The patent creates a thermally stable composite material system where the magnesium-aluminum mixed oxide support provides thermal stability, the nitrogen oxide storage components (barium, strontium, or calcium compounds) maintain storage capacity, and the reduced platinum content provides catalytic activity. This composite structure resists thermal aging even at high exhaust temperatures.
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 catalyst exhibits improved thermal aging stability and reduced noble metal costs, maintaining effective nitrogen oxide storage capacity and denoxing performance, even under high exhaust gas temperatures, while minimizing platinum content and avoiding adverse effects from sulfur oxides and oxygen storage materials.
Implementation Method 1
The catalyst exhibits improved thermal aging stability... even under high exhaust gas temperatures
Implementation Method 2
the nitrogen oxides are stored predominantly in the form of nitrates by the storage material of the storage catalyst
Implementation Method 3
the nitrogen oxides are stored predominantly in the form of nitrates by the storage material of the storage catalyst
Implementation Method 4
oxidize nitrogen oxides to NO2, and CO and HC to CO2, under lean conditions
Implementation Method 5
reduce NO2 released to nitrogen
Implementation Method 6
The task of these catalytically active components is firstly to oxidize nitrogen oxides to NO2, and CO and HC to CO2
Data Source
AI summary
A nitrogen oxide storage catalyst is provided, which has two catalytically active coatings on a support body. The lower coating applied directly to the support body has a nitrogen oxide storage function and includes platinum as a catalytically active component applied to a homogeneous magnesium-aluminum mixed oxide in combination with a nitrogen oxide storage material, in which a nitrogen oxide storage component is likewise present and applied to a homogeneous magnesium-aluminum mixed oxide. The second layer is notable for three-way catalytic activity, and includes palladium applied to aluminum oxide and barium oxide or strontium oxide, but no platinum.