Exhaust Gas Catalyst Alkaline-Earth Sulfate Particle Control
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Solution Overview
Problem
Existing exhaust gas-purifying catalysts face inefficiencies in NOx purification due to poisoning by hydrocarbons, particularly under rich atmospheres, and require improvement in overall exhaust gas purification performance.
Innovation Solution
An exhaust gas-purifying catalyst comprising a substrate with a catalytic layer containing a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal with a controlled average particle diameter of 0.01 to 0.70 μm, which enhances the suppression of hydrocarbon poisoning and improves NOx purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a salt of an alkaline-earth metal element is added to suppress poisoning by HC, then the NOx purification efficiency is improved to some extent, but the exhaust gas purification performance still has room for further improvement
Solution Approach 1:
The invention changes the particle diameter parameter of the alkaline-earth metal salt to a specific range (0.01 to 0.70 μm) to optimize its effectiveness. This parameter change enhances the suppression of HC poisoning while improving overall exhaust gas purification performance, resolving the contradiction between partial improvement and overall performance limitations.
Solution Approach 2:
The invention creates a composite catalytic layer containing precious metal, alumina, oxygen storage material, and alkaline-earth metal salt in specific combinations. This composite structure synergistically improves both NOx purification efficiency and overall exhaust gas purification performance, overcoming the limitation of using alkaline-earth metal salt alone.
2Productivity
If precious metals are used as catalytic metals, then oxidation reactions of HC and CO and reduction reactions of NOx are promoted, but the precious metals are susceptible to poisoning by HC in the exhaust gas
Solution Approach 1:
The alkaline-earth metal salt acts as an intermediary substance between HC and precious metals. It suppresses the direct interaction between HC and precious metals, preventing poisoning while allowing the precious metals to maintain their catalytic promotion of oxidation and reduction reactions.
Solution Approach 2:
The invention applies alkaline-earth metal salt specifically in the catalytic layer where precious metals are located, creating a localized protective environment. This local application suppresses HC poisoning at the critical interface while preserving the catalytic activity of precious metals.
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 achieves improved NOx purification performance and overall exhaust gas purification by ensuring effective contact between the alkaline-earth metal and precious metal, maintaining high uniformity and proximity, thereby optimizing the catalytic reaction.
Implementation Method 1
the alkaline-earth metal element acts to suppress the poisoning of the precious metals by HC
Implementation Method 2
an oxygen storage material
Implementation Method 3
The precious metals play a role in promoting oxidation reactions of HC and CO
Implementation Method 4
reduction reactions of NOx
Data Source
AI summary
An exhaust gas-purifying catalyst includes a substrate, and a catalytic layer facing the substrate and including a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope. Another exhaust gas-purifying catalyst includes a substrate, and a catalytic layer formed on the substrate using slurry containing a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope.