Aging-Resistant Catalyst Article with Palladium and Ceria-Free Storage
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Solution Overview
Problem
Current three-way catalysts used in internal combustion engines face significant deactivation under high temperature rich aging conditions, particularly when exposed to steam/air and high temperature rich aging protocols, leading to a need for improved stability and performance with reduced platinum and rhodium content.
Innovation Solution
A high-palladium catalyst article is developed with a first catalytic layer comprising palladium on a ceria-free oxygen storage component and platinum on a refractory metal oxide support, and a second layer with rhodium on a zirconia-coated support, enhancing durability and performance under lean and rich operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ceria-based oxygen storage component is used in TWC catalyst, then oxygen storage capacity is improved, but surface area is lost when exposed to high temperatures (800°C or above)
Solution Approach 1:
The patent uses ceria-zirconia mixed oxides as a composite material that combines the high oxygen storage capacity of ceria with the thermal stability of zirconia. This composite structure prevents the surface area loss that occurs with pure ceria at high temperatures while maintaining effective oxygen storage and release functionality for three-way catalysis.
Solution Approach 2:
The patent modifies the chemical composition parameters of the oxygen storage component by creating a mixed oxide system with specific ratios of ceria and zirconia. This parameter change transforms the material properties to achieve both high oxygen storage capacity and resistance to surface area degradation at elevated temperatures.
2Adaptability or versatility
If TWC catalyst is designed for both lean and rich operating conditions, then versatility is improved, but performance under rich aging conditions deteriorates
Solution Approach 1:
The patent creates distinct functional zones within the catalyst structure by formulating separate washcoat compositions with specific PGM distributions and oxygen storage component ratios optimized for different operating conditions. This local differentiation allows the catalyst to maintain high performance and stability specifically under rich aging conditions while still functioning across the full lean-to-rich operating range.
3Productivity
If platinum group metals are used in TWC catalyst, then catalytic activity is improved, but cost increases
Solution Approach 1:
The patent optimizes the concentration parameters of platinum group metals by reducing their overall content while adjusting the distribution and formulation ratios. This parameter optimization maintains sufficient catalytic activity for CO oxidation, HC oxidation, and NOx reduction while significantly lowering the quantity of expensive precious metals required in the catalyst formulation.
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 article exhibits improved durability and performance, particularly under rich operating conditions, with significant reduction in NOx emissions and improved hydrocarbon and carbon monoxide conversion, outperforming conventional catalysts in both fresh and aged states.
Implementation Method 1
The TWC is the most commonly used catalyst and it provides the three functions of oxidation of CO, oxidation of unburned hydrocarbons (HC's) and reduction of NOx to N2
Implementation Method 2
TWC's have been developed to incorporate a component which stores oxygen during lean portions of the operating cycle and releases oxygen during rich portions of the operating cycle
Implementation Method 3
when ceria is doped with precious metal catalysts such as Pd it tends to lose surface area when exposed to high temperatures, e.g. 800° C. or above
Data Source
AI summary
Catalyst articles comprising palladium and related methods of preparation and use are disclosed. Disclosed is a catalyst article comprising a first catalytic layer formed on a substrate, wherein the first catalytic layer comprises palladium impregnated on a ceria-free oxygen storage component and platinum impregnated on a refractory metal oxide, and a second catalytic layer formed on the first catalytic layer comprising platinum impregnated on an oxygen storage component and rhodium impregnated on a zirconia-coated or yttria-coated alumina. The palladium component of the catalyst article is present in a higher proportion relative to the other platinum group metal components. The catalyst articles provide improved reductions in NOx in exhaust gases, particularly after lean-rich aging.