Exhaust Gas Catalyst Pyrochlore Oxygen Storage
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Solution Overview
Problem
Existing exhaust gas purifying catalysts face challenges in maintaining high NOX purification performance after endurance due to fluctuations in air-fuel ratios and sulfur component presence, which accelerates catalyst deterioration and reduces noble metal efficiency.
Innovation Solution
An exhaust gas purifying catalyst is developed with a first oxygen storage material having a pyrochlore phase type regular array structure without noble metals, combined with a second oxygen storage material having a higher oxygen storage rate and lower capacity, where a platinum group noble metal is supported on the second material, optimizing the Ce/Zr molar ratio and specific surface area to enhance NOX conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single oxygen storage material is used to maintain high OSC capacity, then the catalyst shows good NOX purification performance initially, but the performance deteriorates rapidly under sulfur-rich conditions and A/F fluctuations
Solution Approach 1:
The patent uses a composite oxygen storage material system combining ceria-based material (high OSC capacity) and zirconia-based material (high thermal stability and sulfur resistance). This composite structure allows the catalyst to maintain high NOX purification performance while resisting deterioration under sulfur-rich conditions and A/F fluctuations, thereby extending catalyst endurance.
Solution Approach 2:
The patent applies different oxygen storage materials with specific properties to different functional requirements: ceria-based material provides high OSC capacity for rapid A/F compensation, while zirconia-based material provides thermal stability and sulfur resistance. This local differentiation of material properties optimizes overall catalyst performance and durability.
2Reliability
If noble metal loading is increased to improve catalytic activity, then NOX purification performance improves, but cost increases and noble metal efficiency decreases under fluctuating conditions
Solution Approach 1:
The patent optimizes the OSC capacity parameter of the oxygen storage material to enhance the oscillation of oxygen storage and release. This parameter change allows the catalyst to maintain high NOX purification performance with reduced noble metal loading by improving the efficiency of oxygen transfer between the oxygen storage material and noble metal sites.
Solution Approach 2:
The oxygen storage material serves itself by autonomously oscillating between oxygen storage and release states in response to A/F fluctuations. This self-service mechanism reduces the burden on noble metals, allowing lower noble metal loading while maintaining catalytic activity and NOX purification performance.
3Speed
If the oxygen storage rate is increased to respond quickly to A/F fluctuations, then the catalyst can compensate for transient conditions better, but the overall oxygen storage capacity decreases
Solution Approach 1:
The patent segments the oxygen storage function into two complementary materials: ceria-based material that provides rapid oxygen storage and release (high OSC rate) and zirconia-based material that provides bulk oxygen storage capacity. This segmentation allows the system to achieve both fast response to A/F fluctuations and high overall oxygen storage capacity.
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 higher NOX conversion efficiency and longer endurance by stabilizing oxygen storage capacity, reducing emission deterioration, and maintaining performance even in sulfur-rich conditions, while minimizing noble metal usage.
Implementation Method 1
an oxygen storage material which has a pyrochlore phase type regular array structure... a higher oxygen storage rate and a lower oxygen storage capacity than the first oxygen storage material
Implementation Method 2
a three-way catalyst that is composed of a porous oxide carrier such as alumina (Al2O3), silica (SiO2), zirconia (ZrO2) or titania (TiO2), and a noble metal, such as platinum (Pt), rhodium (Rh) or palladium (Pd), that is supported on the carrier... purify HC and CO in the exhaust gas by oxidation and also purify NOX by reduction
Implementation Method 3
an oxygen occluding material that is obtained by mixing first cerium-based oxygen occluding material particles (A) which have a first number average particle size and second cerium-based oxygen occluding material particles (B) which have the same composition as the particles (A) and a second number average particle size which is greater than the first number average particle size
Data Source
AI summary
An exhaust gas purifying catalyst that contains a first oxygen storage material on which no noble metal is supported and which has a pyrochlore phase type regular array structure, and a second oxygen storage material which has a higher oxygen storage rate and a lower oxygen storage capacity than the first oxygen storage material and on which a platinum group noble metal is supported.