Cerium Oxide Particles for Exhaust Gas Catalysts
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Solution Overview
Problem
Current cerium oxide-based catalysts for purifying vehicle exhaust gas lack sufficient heat resistance and oxygen absorbing and desorbing capability, especially at lower temperatures, limiting their efficiency in reducing NOx emissions.
Innovation Solution
Cerium oxide particles with specific surface areas between 80-120 m2/g and total pore volumes between 0.9-1.6 ml/g are produced through a method involving a cerium salt solution with 90-100 mol % tetravalent cerium cations, heat treatment, and calcination, enhancing their heat resistance and oxygen handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cerium oxide catalysts are used, then they can perform basic catalytic function, but they lack sufficient heat resistance and oxygen absorbing/desorbing capability at lower temperatures
Solution Approach 1:
The patent applies parameter changes by precisely controlling the oxidation state distribution of cerium (90-100 mol% Ce4+ and 0-10 mol% Ce3+) and the specific surface area (80-120 m2/g) to achieve both high heat resistance and excellent oxygen absorbing/desorbing capability at lower temperatures
Solution Approach 2:
The patent creates a composite cerium oxide material with specific composition (90-100 mol% Ce4+ and 0-10 mol% Ce3+) that combines the thermal stability of Ce4+ with the oxygen storage capacity of Ce3+, achieving both heat resistance and catalytic activity
2Productivity
If cerium oxide catalysts are designed for high oxygen absorbing capability, then they can purify exhaust gas efficiently, but they lose surface area and pore volume at high temperatures
Solution Approach 1:
The patent optimizes the specific surface area parameter to 80-120 m2/g and controls the oxidation state composition (90-100 mol% Ce4+) to maintain structural stability at high temperatures while preserving oxygen absorbing capability
Solution Approach 2:
Instead of increasing oxygen absorbing capability at the expense of surface area, the patent inverts the approach by using predominantly Ce4+ (90-100 mol%) which provides thermal stability, while incorporating a small amount of Ce3+ (0-10 mol%) to provide oxygen storage capacity without compromising surface area
3Temperature
If catalysts are placed close to the engine for hot exhaust gas introduction, then activation temperature is improved, but the oxygen absorbing capability at lower temperatures remains insufficient
Solution Approach 1:
The patent changes the oxidation state parameter to include 0-10 mol% Ce3+ which enables oxygen absorbing/desorbing reactions to proceed efficiently at lower temperatures, reducing the need for high temperature activation
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 cerium oxide particles maintain high specific surface area and pore volume at high temperatures, improving NOx capture performance and reducing NOx emissions, making them suitable for stringent pollution regulations.
Implementation Method 1
cerium oxide-containing materials, which have the properties of absorbing oxygen under the oxidizing atmosphere and desorbing oxygen under the reducing atmosphere
Implementation Method 2
absorbing oxygen under the oxidizing atmosphere and desorbing oxygen under the reducing atmosphere
Implementation Method 3
maintain high specific surface area and pore volume at high temperatures
Data Source
AI summary
The present invention relates to cerium oxide particles that have excellent heat resistance especially useful for catalysts, functional ceramics, solid electrolyte for fuel cells, polishing, ultraviolet absorbers and the like, and particularly suitable for use as a catalyst or co-catalyst material, for instance in catalysis for purifying vehicle exhaust gas. The present invention also relates to a method for preparing such cerium oxide particles, and a catalyst, such as for purifying exhaust gas, utilizing these cerium oxide particles.