Exhaust Catalyst Oxygen Storage Material Composition
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Solution Overview
Problem
Existing exhaust purifying catalysts do not have a sufficient NOx purifying capacity following endurance under fluctuating air-to-fuel (A/F) ratio conditions, which accelerates catalyst deterioration and fails to meet stringent emissions standards.
Innovation Solution
An exhaust purifying catalyst design featuring a substrate with a first-stage and second-stage catalyst, both containing oxygen storage capacity materials, where a proportion of these materials without noble metals are included in a range of 0 to 50 wt%, promoting oxygen storage and release reactions to maintain high NOx purifying capacity under fluctuating A/F conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional oxygen storage materials are used in exhaust purifying catalysts, then the catalyst can operate under stoichiometric conditions, but the NOx purifying capacity deteriorates under fluctuating A/F ratio conditions
Solution Approach 1:
The patent changes the chemical composition parameters of the oxygen storage material by incorporating both cerium-based OSC material and perovskite-type oxide with specific molar ratios. This compositional parameter change enables the material to maintain high NOx purifying capacity under fluctuating A/F conditions by optimizing oxygen storage and release characteristics.
Solution Approach 2:
The patent creates a composite oxygen storage material combining cerium-based OSC material and perovskite-type oxide. This composite structure leverages the complementary properties of both materials: cerium provides rapid oxygen storage/release while perovskite contributes to structural stability and sustained oxygen capacity, resolving the contradiction between reliability and stability.
2Quantity of substance
If the oxygen storage capacity is increased to handle fluctuating A/F ratios, then the catalyst can absorb excessive changes, but the noble metal utilization decreases
Solution Approach 1:
The patent introduces perovskite-type oxide as an intermediary material that facilitates oxygen storage and release reactions. This intermediary enables enhanced oxygen storage capacity independent of noble metal content, as the perovskite structure provides oxygen buffering capability that reduces reliance on noble metals for A/F ratio management.
Solution Approach 2:
By changing the material composition to include perovskite-type oxide with specific cation ratios (0.1-0.9), the patent achieves increased oxygen storage capacity through the perovskite structure's inherent oxygen non-stoichiometry, thereby decoupling oxygen storage capacity from noble metal quantity.
3Speed
If the catalyst is optimized for rapid oxygen storage/release, then it can respond to A/F ratio changes, but the long-term oxygen storage capacity is insufficient
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different components of the oxygen storage material. The cerium-based OSC material provides rapid oxygen storage/release response, while the perovskite-type oxide provides sustained long-term oxygen capacity. This spatial/functional differentiation within the composite material resolves the contradiction between speed and duration.
Solution Approach 2:
The composite structure combines materials with complementary kinetic and storage properties. Cerium oxide provides fast response kinetics while perovskite provides bulk oxygen reservoir capacity, achieving both rapid oxygen storage/release rates and sustained long-term capacity through synergistic material combination.
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 catalyst achieves a higher NOx purification ratio compared to conventional systems, even after endurance tests under fluctuating A/F conditions, by optimizing the Ce/Zr molar ratio and specific surface area, ensuring long-term oxygen storage and release capabilities.
Implementation Method 1
promoting oxygen storage and release reactions to maintain high NOx purifying capacity under fluctuating A/F conditions
Data Source
AI summary
An exhaust purifying catalyst includes: a substrate; a first-stage catalyst that includes an oxygen storage capacity (OSC) material and that is provided on the substrate on an upstream side thereof in an exhaust gas flow direction; and a second-stage catalyst that includes an OSC material and that is provided on the substrate on a downstream side thereof in an exhaust gas flow direction. The OSC material included in the first-stage catalyst and the second-stage catalyst includes OSC material on which a noble metal is not supported. The proportion of the amount of the OSC material, on which a noble metal is not supported, and that is included in the second-stage catalyst with respect to the combined amount of the OSC material, on which a noble metal is not supported, and that is included in the first-stage catalyst and the second-stage catalyst is in a range of from 0 to 50 wt %.