Al-Ce-Zr Inorganic Oxide for High-Temperature Catalyst Stability
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Solution Overview
Problem
Three-way catalysts face performance degradation due to low heat resistance of Al—Ce—Zr oxide, leading to sintering and agglomeration of catalyst metal during high-temperature exhaust gas purification.
Innovation Solution
A powder inorganic oxide with specific composition and processing conditions, including uniaxial molding and calcination, to achieve superior heat resistance and density, ensuring minimal shrinkage and optimal Al, Ce, and Zr content for supporting catalyst metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Al—Ce—Zr oxide is used as catalyst-supporting layer, then oxygen storage capacity is improved, but heat resistance deteriorates leading to sintering at high temperature
Solution Approach 1:
The invention changes the chemical composition parameters of the inorganic oxide by incorporating specific amounts of Ba (0.1-5 wt%), Sr (0.1-5 wt%), or Ca (0.1-5 wt%) in addition to Al, Ce, and Zr. This compositional modification adjusts the thermal stability and oxygen storage capacity to achieve both high heat resistance and adequate oxygen storage function.
Solution Approach 2:
The invention creates a composite inorganic oxide material combining multiple metal oxides (Al2O3, CeO2, ZrO2, and at least one of BaO, SrO, or CaO). This composite structure synergistically combines the high-temperature stability of alumina with the oxygen storage capacity of ceria-zirconia, while the added alkaline earth metal oxides further enhance thermal resistance.
2Quantity of substance
If Al—Ce—Zr oxide has low heat resistance, then oxygen storage capacity is maintained, but catalyst metal moves and agglomerates causing performance degradation
Solution Approach 1:
The invention modifies the compositional parameters by adding alkaline earth metal oxides (BaO, SrO, or CaO) to stabilize the crystal structure at high temperatures. This prevents sintering of the support oxide and consequently prevents migration and agglomeration of supported catalyst metal particles, maintaining catalytic performance stability.
Solution Approach 2:
The composite inorganic oxide material provides a thermally stable matrix that anchors catalyst metal particles, preventing their movement and agglomeration during high-temperature operation while maintaining adequate oxygen storage capacity through the Ce-Zr component.
3Strength
If inorganic oxide density is increased to 1.0-1.3 g/ml, then mechanical strength is improved, but shrinkage during calcination increases
Solution Approach 1:
The invention optimizes the density parameter of the inorganic oxide to a specific range (1.0-1.3 g/ml) that balances mechanical strength and shrinkage behavior. This density range ensures adequate structural integrity while limiting shrinkage during calcination to maintain dimensional stability and manufacturing precision.
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 resulting catalyst maintains performance even at high temperatures, suppressing degradation and ensuring effective exhaust gas purification.
Implementation Method 1
inorganic oxide containing Al, Ce and Zr as constituent elements and having oxygen storage capacity (OSC) that stores oxygen under an oxidizing atmosphere and releases oxygen under a reducing atmosphere
Implementation Method 2
when the heat resistance of Al—Ce—Zr oxide forming the catalyst-supporting layer is low, the oxide is sintered during the exhaust gas purification
Data Source
AI summary
Provided is a powder inorganic oxide containing Al, Ce and Zr as constituent elements, that affords a molded product with a density of 1.0 to 1.3 g/ml by placing 4.0 g of the inorganic oxide in a cylindrical container having diameter 20 mm and performing uniaxial molding under conditions of room temperature and pressure of 29.4 MPa for 30 sec., and achieves an average shrinkage percentage of not more than 14.0% as calculated by the following formula: average shrinkage percentage (%)=100×{(1−(c)/(a))+(1−(d)/(b))}/2 wherein each symbol is as defined in the DESCRIPTION.