Ce-Zr Solid Solution for Stable Oxygen Storage
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Solution Overview
Problem
Cerium-zirconium solid solutions used in catalytic applications face instability due to the dynamic equilibrium of trivalent and tetravalent cerium ions, leading to lattice changes that affect catalyst life and catalytic activity, particularly in varying oxygen conditions.
Innovation Solution
A cerium-zirconium solid solution with a specific ratio of trivalent to tetravalent cerium ions (Ce3+/Ce4+ molar ratio of 0.05-0.8:1) is developed, combined with rare earth elements, which maintains a stable structure and high oxygen storage and release capacity, and is prepared through a simple and controlled method involving hydrothermal reactions and calcination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trivalent cerium and tetravalent cerium freely convert under certain conditions to enable oxygen storage and release, then oxygen storage and release performance is improved, but lattice stability deteriorates leading to structure instability
Solution Approach 1:
The patent changes the chemical composition parameters by introducing rare earth elements (La, Nd, Pr) and adjusting the Ce/Zr molar ratio to specifically control the Ce3+/Ce4+ ratio. This parameter optimization enables the material to maintain both high oxygen storage capacity and structural stability by preventing excessive lattice shrinkage or expansion during cerium valence transitions.
Solution Approach 2:
The patent creates a composite material system combining cerium oxide, zirconium oxide, and multiple rare earth element oxides. This composite structure synergistically combines the oxygen storage capacity of cerium with the structural stability of zirconium and the stabilizing effects of rare earth elements, resolving the contradiction between reactivity and stability.
2Productivity
If lattice shrinkage and expansion occur during cerium valence conversion, then oxygen storage and release function is enhanced, but catalyst life and activity deteriorate due to structure instability
Solution Approach 1:
The patent applies beforehand cushioning by introducing rare earth elements that act as structural buffers. These elements preemptively compensate for the lattice stress caused by cerium valence transitions, preventing pore channel collapse and maintaining structural integrity throughout the catalyst's service life, thus cushioning against degradation before it occurs.
3Adaptability or versatility
If cerium-zirconium composite oxide is used to achieve high oxygen storage capacity, then catalytic performance under varying air-fuel ratios is improved, but structural stability deteriorates affecting catalyst longevity
Solution Approach 1:
The patent applies local quality by creating regions with different compositions and Ce3+/Ce4+ ratios within the catalyst structure. The rare earth elements are distributed to provide localized structural support in regions prone to lattice instability, while maintaining high oxygen storage capacity in other regions, thus achieving both adaptability and stability.
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 provides a stable catalyst with high oxygen storage and release rates, maintaining catalytic performance across different air-fuel ratios and extending catalyst life, thus reducing costs.
Implementation Method 1
When there is too much air in the exhaust gas, trivalent cerium absorbs oxygen and stores it, and at the same time converts into tetravalent cerium
Implementation Method 2
when there is a lack of oxygen in the tail gas, tetravalent cerium will release oxygen to ensure the full oxidation of hydrocarbons and carbon monoxide
Implementation Method 3
The preparation method for the cerium-zirconium solid solution involves hydrothermal reactions and calcination
Implementation Method 4
The preparation method for the cerium-zirconium solid solution involves hydrothermal reactions and calcination
Data Source
AI summary
Disclosed are a cerium-zirconium solid solution and a preparation method therefor and an application thereof, which belong to the field of adsorbing catalyst materials. The cerium-zirconium solid solution includes a cerium-zirconium solid solution phase with a Ce3+/Ce4+ molar ratio of 0.05-0.8:1. The cerium-zirconium solid solution phase in the cerium-zirconium solid solution of the present application includes trivalent cerium ions and tetravalent cerium ions in a specific ratio. The cerium-zirconium solid solution has a high oxygen storage and release rate, a high oxygen storage and release capacity, and the cerium-zirconium solid solution during the storage and release of oxygen has a stable structure and good catalytic performance; and the catalyst containing the cerium-zirconium solid solution has good catalytic performance under different fuel ratios.