Zirconium Cerium Oxide Catalyst Composition
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Solution Overview
Problem
Current catalysts for treating exhaust gases from internal combustion engines lack a high specific surface area and low maximum reduction temperature, which are essential for effective oxidation and reduction of carbon monoxide, hydrocarbons, and nitrogen oxides.
Innovation Solution
A mixed oxide composition comprising zirconium oxide, cerium oxide, lanthanum oxide, yttrium and/or gadolinium oxide, and tin oxide, with specific weight percentages, obtained through precipitation and calcination, exhibiting high specific surface area and low maximum reduction temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional catalyst compositions are used, then the catalyst structure is simple, but the specific surface area after calcination is low and the maximum reduction temperature is high
Solution Approach 1:
The patent uses a composite oxide material comprising zirconium oxide, cerium oxide, lanthanum oxide, yttrium oxide, and tin oxide in specific proportions. This composite structure combines the advantages of each component: zirconium oxide provides thermal stability, cerium oxide contributes to oxygen storage capacity, lanthanum oxide enhances surface area, yttrium oxide improves reducibility, and tin oxide promotes catalytic activity. The synergistic effect of these components achieves low maximum reduction temperature while maintaining a defined composition structure.
Solution Approach 2:
The patent optimizes the weight percentages of each oxide component within specific ranges: zirconium oxide (40-70%), cerium oxide (20-40%), lanthanum oxide (0.1-10%), yttrium oxide (3-20%), and tin oxide (1-15%). By precisely controlling these compositional parameters, the catalyst achieves optimal balance between reduction temperature and structural stability, demonstrating parameter optimization to resolve the contradiction.
2Area of stationary object
If conventional catalyst compositions are used, then the manufacturing process is simple, but the specific surface area after calcination at high temperatures is low
Solution Approach 1:
The patent employs a precipitation process where metal salts are first dissolved in water, then precipitated as hydroxides or carbonates before calcination. This preliminary formation of precursor compounds ensures uniform distribution of all oxide components and creates a structured precursor that, upon calcination, yields high specific surface area. The precipitation step pre-organizes the material structure to facilitate subsequent high-temperature treatment while maintaining surface area.
Solution Approach 2:
The catalyst composition is designed to form a porous structure after calcination, with lanthanum oxide and yttrium oxide specifically contributing to pore formation and maintenance. The controlled precipitation and calcination process creates a hierarchical porous structure that preserves high specific surface area even after calcination at temperatures of 800-1000°C, resolving the contradiction between thermal stability and surface area retention.
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 composition achieves a high specific surface area after calcination at high temperatures and a low maximum reduction temperature, enhancing catalytic properties for efficient treatment of exhaust gases.
Implementation Method 1
The compositions of the present invention are obtained by precipitation and calcination
Implementation Method 2
a BET specific surface area, after calcination at 1000°C for 6 hours, of at least 45 m2/g
Implementation Method 3
This reducibility can be measured, for example, by a consumption of hydrogen within a given temperature range. It is due to the cerium, which has the property of being reduced or of being oxidized
Implementation Method 4
The term 'multifunctional' is understood to mean catalysts capable of carrying out not only oxidation, in particular of carbon monoxide and hydrocarbons present in exhaust gases
Implementation Method 5
but also reduction, in particular of nitrogen oxides also present in these gases
Data Source
AI summary
The present invention relates to compositions based on zirconium oxide and cerium oxide that exhibit a sufficiently high specific surface area after calcination and a low maximum reduction temperature of the oxide after calcination. Compositions of the present invention may be notably used in various catalytic systems, such as for the treatment of exhaust gases from internal combustion engines.