Cerium-Aluminum Composite Exhaust Catalyst for Low-Temperature NO Oxidation
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Solution Overview
Problem
Existing catalysts for diesel engine exhaust gas purification, such as those described in JP2002-211908A (US2002/0090512A1), are inadequate in oxidizing nitrogen oxides (NOx) due to insufficient oxidation performance, particularly at low exhaust gas temperatures.
Innovation Solution
A catalyst layer containing platinum, palladium, and a cerium-aluminum composite oxide (CexAlyOz) with specific stoichiometric ratios (x>y, x+y=1, 1.95≤z≤2.05) is formed on a three-dimensional structure, leveraging lattice defects to enhance NO oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-way catalyst with precious metal supported on composite oxide is used, then durability is improved, but oxidation performance (particularly NO oxidation performance) is insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the support material by introducing a specific cerium-aluminum composite oxide with controlled Ce/Al ratio (x/y=2-10) and oxygen content (1.95≤z≤2.05 in CexAlyOz). This parameter optimization enhances the oxidation performance, particularly for NO oxidation, while preserving the durability provided by the composite oxide structure.
Solution Approach 2:
The invention uses a composite material approach by combining cerium oxide and aluminum oxide in specific proportions to create a cerium-aluminum composite oxide. This composite support material provides both the durability of the oxide structure and the enhanced oxidation performance, particularly for NO oxidation, resolving the contradiction between durability and oxidation performance.
2Productivity
If oxidation catalyst is used to supply NO2 for SCR reaction, then exhaust gas purification is improved, but at low temperatures the oxidation reaction from NO to NO2 is insufficient
Solution Approach 1:
The invention optimizes the oxygen content parameter of the cerium-aluminum composite oxide (controlling z value between 1.95 and 2.05 in CexAlyOz) to enhance the catalyst's ability to supply lattice oxygen. This parameter control enables efficient NO oxidation to NO2 even at low temperatures, improving exhaust gas purification efficiency without requiring high temperatures.
Solution Approach 2:
The cerium-aluminum composite oxide acts as an intermediary that facilitates the oxidation of NO to NO2 at low temperatures by providing lattice oxygen from its controlled oxygen content. This intermediary mechanism enables the oxidation reaction to proceed efficiently at temperatures where conventional catalysts fail, thereby improving overall exhaust gas purification efficiency.
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 effectively oxidizes CO, HC, and NO, especially NO, in diesel engine exhaust gases, even at low temperatures, improving exhaust gas purification efficiency.
Implementation Method 1
a catalyst layer containing platinum, palladium, a cerium-aluminum composite oxide or an aluminum oxide and a cerium-aluminum composite oxide is formed on a three-dimensional structure, and the cerium-aluminum composite oxide contains CexAlyOz (where x>y, x+y=1, and 1.95≤z≤2.05)
Implementation Method 2
a catalyst layer containing platinum, palladium, and a cerium-aluminum composite oxide or a cerium-aluminum composite oxide and an aluminum oxide, formed on a three-dimensional structure
Data Source
AI summary
The invention provides a catalyst capable of effectively oxidizing an exhaust gas (particularly NO). The invention relates to an oxidation catalyst for exhaust gas purification including a catalyst layer containing platinum, palladium, and a cerium-aluminum composite oxide or a cerium-aluminum composite oxide and an aluminum oxide, formed on a three-dimensional structure, in which the cerium-aluminum composite oxide contains CexAlyOz (where x>Y, x+y=1, and 1.95≤z≤2.05).