Exhaust Gas Purification Catalyst with ZrO2 Composite Oxide
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Solution Overview
Problem
Existing exhaust gas purification catalysts face challenges in maintaining catalytic activity and oxygen storage capacity (OSC) performance, especially at low temperatures, due to the proximity of noble metals like Rh to OSC materials, which can lead to deterioration and reduced NOx conversion efficiency.
Innovation Solution
The catalyst design includes a substrate with a first catalyst coating layer containing Pd and/or Pt upstream and a second catalyst coating layer with Rh supported on ZrO2-containing composite oxides, with specific weight ratios and particle sizes, allowing for efficient NOx conversion and OSC performance even at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Rh is placed close to OSC material to enhance low-temperature catalytic activity, then catalytic activity is improved, but Rh aggregation occurs and NOx conversion efficiency deteriorates
Solution Approach 1:
The patent introduces a ZrO2-containing composite oxide as an intermediary material positioned between the Rh catalyst and the OSC material. This intermediary prevents direct contact and aggregation between Rh and OSC material while still allowing oxygen transfer, thus maintaining catalytic activity at low temperatures without compromising NOx conversion efficiency. The ZrO2 composite oxide acts as a buffer that meditates the interaction between the two functional materials.
Solution Approach 2:
The patent creates distinct functional zones within the catalyst coating layer. The Rh catalyst is localized in specific regions where it can maintain high dispersion and activity, while the OSC material is positioned in other regions to provide oxygen storage capacity. The ZrO2-containing composite oxide forms a transition zone that ensures proper oxygen transfer while preventing unwanted interactions, thus optimizing both catalytic activity and NOx conversion efficiency in different local areas.
2Loss of substance
If noble metal amount is reduced to address resource risk, then resource efficiency is improved, but catalytic activity decreases
Solution Approach 1:
The patent changes the physical and chemical parameters of the catalyst support system by introducing ZrO2-containing composite oxides with specific properties (particle size, surface area, oxygen mobility). These parameter changes enhance the dispersion and stability of Rh particles, allowing lower Rh loading while maintaining or even improving catalytic activity. The optimized support structure provides better anchoring sites and oxygen transfer pathways.
Solution Approach 2:
The patent employs a composite material system consisting of Rh catalyst, ZrO2-containing composite oxide, and OSC material. This composite structure synergistically combines the functions of different materials to achieve high catalytic activity with reduced noble metal content. The ZrO2 composite oxide enhances the overall system performance by improving Rh dispersion and facilitating oxygen transfer, thereby reducing the required Rh amount while maintaining activity.
3Adaptability or versatility
If OSC material is added to maintain oxygen concentration during air-fuel ratio variations, then purification performance is maintained, but low-temperature OSC performance and Rh catalyst performance mutually interfere
Solution Approach 1:
The ZrO2-containing composite oxide serves as an intermediary that facilitates controlled oxygen transfer between the OSC material and the exhaust gas. At low temperatures, this intermediary regulates the oxygen mobility to prevent excessive oxygen consumption by the OSC material, thereby preserving catalytic activity. The intermediary structure allows the system to adapt to air-fuel ratio variations while maintaining low-temperature performance.
Solution Approach 2:
The patent creates a dynamic oxygen transfer system where the ZrO2-containing composite oxide modulates oxygen mobility based on operating conditions. At low temperatures, the oxygen transfer is controlled to maintain Rh catalyst activity, while at higher temperatures or during air-fuel ratio variations, the OSC material can actively regulate oxygen concentration. This dynamic behavior allows the system to optimize performance across different operating conditions without mutual interference.
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
This configuration balances catalytic activity and OSC performance, ensuring effective exhaust gas purification at low temperatures and in rich atmospheres, while preventing Rh aggregation and maintaining high NOx conversion rates.
Implementation Method 1
The catalyst coating layer includes a second catalyst coating layer containing Rh as a catalyst metal, in which Rh is supported on a ZrO2-containing composite oxide
Implementation Method 2
Rh is supported on a ZrO2-containing composite oxide selected from zirconia, an alumina-zirconia-based composite oxide (AZ), and an alumina-zirconia-titanium-based composite oxide (AZT)
Implementation Method 3
The OSC material is a material that can absorb and release oxygen. The OSC material allows keeping an oxygen concentration constant to maintain a purification performance (catalyst performance) of the exhaust gas purification catalyst even when an air-fuel ratio varies.
Implementation Method 4
reduces NO2 into nitrogen (N2) in a stoichiometric atmosphere and a rich atmosphere
Implementation Method 5
a catalyst coating layer coated over the substrate
Data Source
AI summary
Provided is an exhaust gas purification catalyst providing a catalyst performance and an OSC performance at the same time even at low temperature. The present disclosure relates to an exhaust gas purification catalyst including a substrate and a catalyst coating layer coated on the substrate. The catalyst coating layer includes a first catalyst coating layer containing Pd and/or Pt and a second catalyst coating layer containing Rh. The first catalyst coating layer is formed from an end portion in an upstream side with respect to an exhaust gas flow direction in the exhaust gas purification catalyst. The second catalyst coating layer includes an upstream coating layer and a downstream coating layer. Rh in the upstream coating layer and the downstream coating layer are supported on specific carrier particles. Further, a particle diameter of Rh is controlled.