Cyclic Oxidation Reducing Ceramic Catalysts
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Solution Overview
Problem
Conventional catalytic monoliths in high temperature environments face challenges in maintaining catalytic activity due to the tendency of dopant metal particles to coalesce and deactivate under reducing conditions, and require washcoats that reduce available surface area and increase pressure drop.
Innovation Solution
A ceramic composition comprising dopant metal oxides with a higher Gibbs free energy of formation than structural oxides, sintered and exposed to cyclic reducing and oxidizing environments to form dopant metal particles supported on structural oxides, which maintains catalytic activity and increases heat capacity without the need for washcoats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant metal particles are used in conventional catalytic monoliths, then catalytic activity is provided, but the particles coalesce and deactivate under reducing conditions at high temperatures
Solution Approach 1:
The patent uses an oxide layer as an intermediary substance that forms between the dopant metal particles and the reducing environment. This oxide layer acts as a protective barrier that prevents direct contact between the reducing conditions and the metal particles, thereby preventing coalescence and deactivation while allowing catalytic activity to persist.
Solution Approach 2:
The patent changes the chemical state parameter of the dopant metal by maintaining it in an oxidized form rather than metallic form. By controlling the oxidation state through the oxide layer, the material achieves both stability against coalescence and catalytic activity, resolving the contradiction between particle stability and catalytic function.
2Reliability
If washcoats are added to monoliths to provide catalytic activity, then catalytic function is achieved, but available surface area is reduced and pressure drop increases
Solution Approach 1:
The patent merges the structural monolith material with catalytic functionality by incorporating dopant metal particles directly into the monolith structure. This integration eliminates the need for separate washcoats, allowing the entire monolith surface to remain available for both structural support and catalytic reactions, thereby resolving the contradiction between catalytic activity and surface area availability.
Solution Approach 2:
The monolith structure is designed to serve multiple functions simultaneously: it provides structural support, maintains high surface area availability, and delivers catalytic activity through integrated dopant particles. This multi-functionality eliminates the need for additional washcoat layers that would compromise surface area and increase pressure drop.
3Area of stationary object
If monolith cell density is increased to provide more catalytic surface area, then available surface area increases, but flow conditions deteriorate
Solution Approach 1:
The patent applies dopant metal particles selectively at the local level on the monolith surface rather than requiring increased cell density. By enhancing the catalytic quality of the existing surface through particle incorporation, the design maintains optimal flow conditions while providing sufficient catalytic surface area through improved local activity rather than increased density.
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 ceramic composition achieves ongoing catalytic activity and increased heat capacity, allowing for higher cell densities and smaller cell sizes while maintaining desirable flow conditions, and can be used in various reaction environments involving both reducing and oxidizing conditions.
Implementation Method 1
The initial composition can then be sintered at a temperature of 1200° C. to 1700° C. to form a sintered composition comprising at least the one or more structural metal oxides. The sintered composition can then be exposed to a reducing environment comprising a temperature of 500° C. to 1400° C. or more to form a catalytic composition comprising dopant metal particles supported on the one or more structural oxides.
Implementation Method 2
The catalytic composition can then be exposed to an oxidizing environment comprising a temperature of 500° C. or more to form an activated catalytic composition.
Implementation Method 3
The ceramic composition achieves ongoing catalytic activity and increased heat capacity, allowing for higher cell densities and smaller cell sizes while maintaining desirable flow conditions
Data Source
AI summary
Ceramic compositions with catalytic activity are provided, along with methods for using such catalytic ceramic compositions. The ceramic compositions correspond to compositions that can acquire increased catalytic activity by cyclic exposure of the ceramic composition to reducing and oxidizing environments at a sufficiently elevated temperature. The ceramic compositions can be beneficial for use as catalysts in reaction environments involving swings of temperature and/or pressure conditions, such as a reverse flow reaction environment. Based on cyclic exposure to oxidizing and reducing conditions, the surface of the ceramic composition can be converted from a substantially fully oxidized state to various states including at least some dopant metal particles supported on a structural oxide surface.