Nd-Zirconia Supported Pd Catalyst for Exhaust Purification
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Solution Overview
Problem
Existing exhaust gas purification catalysts for gasoline engines face challenges with heat resistance and productivity, as they require high-temperature treatments and have insufficient palladium surface area, leading to decreased catalytic performance.
Innovation Solution
A three-way catalyst with Pd catalyst particles supported on Nd- or La-solid dissolved zirconia-based complex oxides, which enhances heat resistance and palladium surface area, allowing for efficient NOx, CO, and HC purification, and is easier to produce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If catalyst metal particles are supported on conventional supports to decrease PGM usage, then the amount of expensive PGM is reduced, but the particles sinter together at high temperature and catalytic activity decreases significantly
Solution Approach 1:
The invention uses a composite support material consisting of Al2O3 particles combined with a predetermined metal oxide (such as TiO2, SiO2, ZrO2, CeO2, or their mixtures) in specific weight ratios. This composite structure prevents sintering of Pd particles at high temperatures while maintaining high catalytic activity, resolving the contradiction between reducing PGM quantity and maintaining reliability.
2Reliability
If Al2O3-based supports are used to suppress sintering through particle interposition, then grain growth is suppressed and surface area is retained, but heat resistance is insufficient for gasoline engines and catalytic performance decreases rapidly
Solution Approach 1:
The invention combines Al2O3 particles with high-melting-point metal oxides (TiO2, SiO2, ZrO2, CeO2) to create a composite support that maintains both sintering suppression capability and high-temperature stability. The predetermined metal oxide components provide thermal stability for gasoline engine applications while Al2O3 particles continue to suppress Pd grain growth through physical interposition.
3Reliability
If high-temperature heat treatment is applied to improve catalyst structure, then catalytic performance can be enhanced, but productivity decreases due to lengthy treatment times of several tens of hours
Solution Approach 1:
The invention optimizes the composition ratios of Al2O3 to predetermined metal oxide (specific weight ratios defined in the patent) to achieve the desired catalyst structure without requiring extensive high-temperature treatment. By carefully controlling the support material composition parameters, the catalyst achieves optimal performance with reduced heat treatment time, thereby improving productivity.
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 excellent heat resistance and three-way purification performance while being cost-effective and easy to produce, making it suitable for gasoline engines with improved catalytic activity.
Implementation Method 1
a three-way catalyst with Pd catalyst particles supported on Nd- or La-solid dissolved zirconia-based complex oxides, which enhances heat resistance and palladium surface area, allowing for efficient NOx, CO, and HC purification
Data Source
AI summary
An exhaust gas-purifying three-way catalyst containing: (i) base material particles of a Nd-solid dissolved zirconia-based complex oxide comprising Nd and Zr as constituent metal elements in the following mass proportions:ZrO250 to 75% by mass; andNd2O3 25 to 50% by mass,in terms of oxides; and (ii) Pd catalyst particles supported on the base material particles, wherein the Nd-solid dissolved zirconia-based complex oxide further contains at least one or more rare earth elements selected from the group consisting of yttrium, scandium, lanthanum, and praseodymium, as a constituent metal element, in an amount of a total of more than 0% by mass to 20% by mass or less in terms of an oxide.