Exhaust Gas-Purifying Catalyst Sintering Suppression
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Solution Overview
Problem
Exhaust gas-purifying catalysts with precious metals like palladium are prone to sintering when exposed to high-temperature fuel-rich exhaust gases, leading to performance deterioration.
Innovation Solution
A composite oxide support with a specific composition represented by the formula AO.xB2-αCαO3, where A represents elements with valences of 1 or 2, B represents elements with a valence of 3, and C represents iridium, ruthenium, tantalum, niobium, molybdenum, or tungsten, is used to suppress sintering, along with precious metals like rhodium, palladium, or platinum, which are supported by this structure.
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:
The patent introduces an intermediary substance (barium sulfate particles) between the precious metal catalyst and the alumina support. This intermediary layer prevents direct contact and sintering of precious metal particles at high temperatures, while still allowing catalytic reactions to occur. The barium sulfate acts as a physical barrier that maintains particle dispersion and prevents aggregation under high-temperature conditions.
Solution Approach 2:
The patent creates a composite catalyst structure consisting of multiple components: precious metal particles, barium sulfate intermediary particles, and alumina support. This composite structure combines the advantages of each material - the catalytic activity of precious metals, the high-temperature stability of barium sulfate, and the support properties of alumina - to achieve both high activity and resistance to sintering.
2Reliability
If alumina support is used to increase surface area, then catalytic activity is improved, but reaction with nickel at high temperatures produces NiAl2O4 spinel structure deteriorating catalyst activity
Solution Approach 1:
The barium sulfate particles serve as an intermediary layer that physically separates the alumina support from the nickel component in the exhaust gas. This intermediary barrier prevents the direct chemical reaction between alumina and nickel that would form the harmful NiAl2O4 spinel structure, while still allowing the catalyst to function effectively.
3Reliability
If ceria is used for oxygen storage, then exhaust gas purification is improved, but grain growth occurs at high temperatures leading to deterioration in oxygen storage capacity
Solution Approach 1:
The barium sulfate particles act as an intermediary that physically restrains ceria particles, preventing them from migrating and coalescing into larger grains at high temperatures. This intermediary framework maintains the fine particle size and high surface area of ceria, preserving its oxygen storage capacity under high-temperature operating 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
The solution effectively reduces the sintering of precious metals, maintaining catalyst performance over time and enhancing exhaust gas purification efficiency even under high-temperature conditions.
Implementation Method 1
The inorganic oxide plays the roles in increasing the specific surface area of the precious metal and suppressing the sintering of the precious metal by dissipating heat generated by the reactions
Implementation Method 2
the precious metal plays the role in promoting the reduction of nitrogen oxides and the oxidations of carbon monoxide and hydrocarbons
Implementation Method 3
suppressing the sintering of the precious metal by dissipating heat generated by the reactions
Data Source
AI summary
An exhaust gas-purifying catalyst includes a support and a catalytic metal supported thereby. The support includes a composite oxide represented by AO.xB2-αCαO3, wherein A represents at least one of an element having a valence of 1 and an element having a valence of 2, B represents an element having a valence of 3, C represents one or more elements selected from iridium, ruthenium, tantalum, niobium, molybdenum, and tungsten, x represents a numerical value of 1 to 6, and α represents a numerical value greater than 0 and less than 2. The catalytic metal includes one or more precious metals selected from rhodium, palladium, and platinum.