Poison-Resistant Exhaust Catalyst Overcoat Layer
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Solution Overview
Problem
Automotive exhaust catalysts face durability issues due to poisoning from oil and fuel additives like phosphorus, zinc, and manganese, which reduce their effectiveness and longevity, necessitating increased precious metal loading to maintain performance under stringent emissions regulations.
Innovation Solution
A catalytic system with a substrate coated with washcoat layers containing precious metal components and an overcoat layer of porous refractory oxide, such as alumina, that captures and traps incoming poisons like phosphorus, zinc, and manganese, preventing fouling and enhancing catalytic activity and durability without requiring higher precious metal loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If increased precious metal loading is used to maintain catalyst performance under stringent emissions regulations, then emissions control effectiveness is improved, but catalyst cost increases
Solution Approach 1:
A sulfur trap layer comprising metal oxides (such as zinc oxide, calcium oxide, magnesium oxide, or barium oxide) is introduced as an intermediary between the exhaust stream and the precious metal catalyst components. This trap layer selectively captures sulfur compounds and other poisons from the exhaust gas, preventing them from reaching and deactivating the precious metal catalyst. The trap layer acts as a protective mediator that allows the use of lower precious metal loadings while maintaining catalyst effectiveness and longevity.
2Quantity of substance
If traditional catalyst layers are used without protection, then catalyst cost is reduced, but catalyst durability decreases due to poisoning from oil and fuel additives
Solution Approach 1:
The sulfur trap layer is applied in advance over the precious metal catalyst components before the exhaust gas contacts the catalyst. This preliminary protective coating prevents poison accumulation on the catalyst surface during operation. By establishing this protective barrier beforehand, the catalyst maintains its activity and durability over extended periods without requiring high precious metal loadings, thus resolving the contradiction between cost and durability.
3Duration of action of stationary object
If sulfur trap layer is added to protect catalyst from poisoning, then catalyst durability is improved, but device complexity increases
Solution Approach 1:
The sulfur trap layer and the catalyst support structure are merged into a single integrated component. The metal oxide-based sulfur trap is applied directly onto the catalyst support, creating a unified structure where the trap layer and catalyst function together as one device. This integration minimizes additional complexity while providing effective poison protection and extending catalyst durability.
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 system effectively mitigates poisoning, maintaining catalytic activity and durability, allowing for reduced precious metal usage and extended catalyst lifespan, thus meeting stringent emissions standards while minimizing costs.
Implementation Method 1
an overcoat layer, which captures, traps, reacts, and/or holds incoming catalyst poisons
Implementation Method 2
an overcoat layer comprising a porous refractory oxide
Data Source
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AI summary
The present invention provides for novel poisoning-resistant catalysts used for automobile exhaust gas treatment systems. To alleviate the detrimental affects of engine oil and/or fuel additive poisoning the present invention provides for an overcoat layer comprising a porous refractory oxide and one or more base metal oxides, which is coated over one or more precious metal containing washcoat layers. The overcoat of the present invention prevents phosphorous as well as other poisoning deposits, from fouling and/or negatively interacting with the underlying precious metal containing washcoats. In an alternative embodiment, the present invention provides for the coating of the upstream end of a catalytic member by the overcoat layer, thereby creating an upstream poison capture zone. A method for treating automobile exhaust gas using the poisoning-resistant catalysts is also provided.