Exhaust Gas-Purifying Catalyst Composite Oxide Support Sintering
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Solution Overview
Problem
Exhaust gas-purifying catalysts with precious metals tend to suffer from sintering issues when exposed to high-temperature, fuel-rich conditions, leading to performance deterioration.
Innovation Solution
A catalyst system featuring a composite oxide support with a perovskite structure, represented by the general formula ABαCβO3, where A includes lanthanum, neodymium, or yttrium, B comprises iron or iron-aluminum, and C consists of iridium, ruthenium, tantalum, niobium, molybdenum, or tungsten, with α and β values within specific ranges, which enhances the suppression of precious metal sintering by allowing oxygen vacancies and controlled valence changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precious metal catalyst is used for exhaust gas purification, then catalytic activity is improved, but sintering occurs at high temperatures leading to performance deterioration
Solution Approach 1:
A composite oxide support comprising Ce, Zr, and La is introduced as an intermediary between the precious metal catalyst and the high-temperature exhaust gas environment. This support material with specific atomic ratios (Ce: 40-70 at%, Zr: 20-50 at%, La: 5-20 at%) acts as a mediator that stabilizes the precious metal particles, preventing their direct exposure to conditions that cause sintering, thereby maintaining both catalytic activity and particle size stability
Solution Approach 2:
The patent employs a composite oxide support material combining multiple metal oxides (ceria, zirconia, and lanthana) in specific proportions. This composite structure leverages the synergistic effects of each component: ceria for oxygen storage capacity, zirconia for thermal stability and grain growth suppression, and lanthana for enhancing overall heat resistance. The composite nature of the support prevents precious metal sintering while maintaining catalytic function
2Productivity
If the exhaust gas temperature is increased to improve reaction efficiency, then purification performance is enhanced, but sintering of precious metal accelerates
Solution Approach 1:
The patent modifies the chemical and physical parameters of the support material by controlling the atomic ratios of Ce, Zr, and La within specific ranges. This parameter optimization creates a support structure with enhanced thermal stability and oxygen storage capacity that can withstand high exhaust gas temperatures. The specific composition parameters enable the support to maintain structural integrity at elevated temperatures, allowing the catalyst to operate efficiently without sintering
Solution Approach 2:
The composite oxide support provides locally optimized properties at the interface with precious metal particles. The specific combination of Ce, Zr, and La creates localized regions with high oxygen storage capacity and thermal stability directly where the precious metal particles are dispersed. This local quality enhancement ensures that the immediate environment of each catalyst particle resists sintering even under high-temperature conditions
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
This configuration effectively prevents sintering of precious metals, maintaining catalyst performance over time by promoting solid-solution formation and alloying with the support, thereby enhancing thermal stability and purification efficiency.
Implementation Method 1
enhances the suppression of precious metal sintering by allowing oxygen vacancies and controlled valence changes
Implementation Method 2
enhances the suppression of precious metal sintering by allowing oxygen vacancies and controlled valence changes
Implementation Method 3
effectively prevents sintering of precious metals, maintaining catalyst performance over time
Implementation Method 4
maintaining catalyst performance over time by promoting solid-solution formation and alloying with the support
Data Source
AI summary
An exhaust gas-purifying catalyst includes a support and a catalytic metal as one or more precious metals supported by the support. The support includes a composite oxide having a composition represented by a general formula ABαCβO3, wherein A represents one or more elements selected from the group consisting of lanthanum, neodymium, and yttrium, B represents iron or a combination of iron and aluminum, C represents one or more elements selected from the group consisting of iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, α and β each represents a numerical value within a range of more than 0 and less than 1, and α and β satisfy relational formulae of β>α and α+β≦1.