Supported Oxide Catalysts for High-Temperature Stability
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Solution Overview
Problem
Catalysts face challenges in maintaining the finely divided state of active phases, such as zirconium oxide and titanium oxide, at high temperatures without sintering, which affects their catalytic efficiency.
Innovation Solution
A composition of zirconium oxide, titanium oxide, or mixed oxides of zirconium and titanium supported on alumina or aluminum oxyhydroxide, with particle sizes of 10 nm or less after calcination at 900°C, ensuring stability and preventing sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If catalysts are exposed to high temperatures, then catalytic activity is maintained, but particle sintering occurs reducing effectiveness
Solution Approach 1:
The patent introduces alumina as an intermediary support material that mediates between the active phase particles and the high-temperature environment. The alumina support provides a stable matrix that prevents direct particle-to-particle contact and sintering, while allowing the catalyst to function at elevated temperatures. This is evident in the supported oxide structure where active phase particles are dispersed on alumina carriers.
Solution Approach 2:
The patent employs parameter changes by controlling particle size to the nanometric range (1-100 nm) and maintaining specific surface area above 100 m²/g. These parameter changes create a size effect where smaller particles have higher surface energy and are more resistant to sintering. The calcination temperature is also optimized at 900°C for 4 hours to achieve the desired particle size and stability balance.
2Area of stationary object
If active phase particles are made finer to increase surface area, then catalytic activity improves, but particles aggregate and sinter at high temperatures
Solution Approach 1:
The patent utilizes the porous structure of alumina support materials to maintain particle dispersion. The porous matrix provides numerous anchoring sites for active phase particles, preventing aggregation while maintaining high surface area. The pore structure physically separates particles and prevents sintering even at high temperatures, as evidenced by the maintained specific surface area after calcination.
Solution Approach 2:
The patent creates composite material systems combining active phase oxides (zirconium oxide, titanium oxide, or mixed oxides) with alumina support. This composite structure leverages the complementary properties of both materials: the active phase provides catalytic activity while the alumina support provides structural stability and particle dispersion. The composite nature prevents sintering by distributing active phase particles throughout the support matrix.
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 maintains the catalytically active particles in a finely divided state even at high temperatures, enhancing catalytic performance and preventing sintering, thus improving the catalyst's effectiveness.
Implementation Method 1
the supported oxide is in the form of particles, deposited on said support
Data Source
Figure 1
AI summary
The composition of the invention comprises at least one supported oxide chosen from zirconium oxide, titanium oxide or a mixed zirconium titanium oxide on an alumina-based or aluminium-oxyhydroxide-based support and is characterized in that, after calcination for 4 hours at 900°C, the supported oxide is in the form of particles deposited on said support, the size of said particles being at most 10 nm when the supported oxide is zirconium oxide and being at most 15 nm when the supported oxide is titanium oxide or a mixed zirconium titanium oxide. The composition of the invention may be used as catalyst, especially for the selective reduction of NOx.