Single-Layer Catalyst Design Preventing Alloy Formation
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Solution Overview
Problem
Current 2-layer catalyst designs for exhaust emission control are complex and costly due to the separation of platinum group metals like palladium and rhodium, which inhibits alloying and reduces catalytic performance.
Innovation Solution
A 1-layer catalyst design where palladium and rhodium are deposited as separate elements in a single layer, with greater than 70 wt% of each metal remaining non-alloyed, utilizing a substrate with an aluminum oxide and oxygen storage component, and a retention material to form a subassembly within a housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 2-layer catalyst design is used to separate platinum group metals and prevent alloying, then catalytic performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The washcoat is segmented into distinct functional zones: a first washcoat layer containing palladium and aluminum oxide, and a second washcoat layer containing rhodium and oxygen storage component. This spatial segmentation prevents alloying between Pd and Rh while maintaining catalytic performance, resolving the contradiction between preventing alloying and simplifying structure.
Solution Approach 2:
Different regions of the catalyst are given different compositions and properties: the first layer is optimized for Pd-based reactions with aluminum oxide support, while the second layer is optimized for Rh-based reactions with oxygen storage capability. This local optimization allows each metal to function at its best without alloying, addressing both performance and structural concerns.
2Reliability
If a 2-layer catalyst design is used to separate platinum group metals, then alloy formation is prevented, but manufacturing cost increases
Solution Approach 1:
By segmenting the washcoat into two distinct layers with different metal compositions, the design prevents alloy formation between Pd and Rh while using a single continuous washcoat application process. This approach avoids the need for separate deposition steps for each layer, thereby preventing alloying without significantly increasing manufacturing complexity or cost.
3Device complexity
If a 1-layer catalyst design is used to simplify manufacturing, then device complexity is reduced, but alloy formation between metals occurs
Solution Approach 1:
The washcoat is segmented into functional zones within a single-layer structure. The first washcoat layer contains Pd and aluminum oxide, while the second washcoat layer contains Rh and oxygen storage component. This segmentation prevents alloying by spatially separating the metals while maintaining a relatively simple single-layer overall structure, thus resolving the contradiction between simplicity and alloy prevention.
Solution Approach 2:
Aluminum oxide and oxygen storage components act as intermediary materials that physically separate Pd and Rh, preventing direct contact and alloy formation. These intermediary substances allow the metals to be in close proximity for catalytic efficiency while maintaining chemical independence, thus achieving both simplicity and alloy prevention.
4Ease of manufacture
If platinum group metals are kept in close proximity in a single layer, then manufacturing is simplified, but alloying occurs and reduces catalytic activity
Solution Approach 1:
The washcoat is segmented into distinct functional zones: a first washcoat layer containing palladium and aluminum oxide, and a second washcoat layer containing rhodium and oxygen storage component. This spatial segmentation prevents alloying between Pd and Rh while maintaining catalytic performance, resolving the contradiction between preventing alloying and simplifying structure.
Solution Approach 2:
Aluminum oxide and oxygen storage components act as intermediary materials that physically separate Pd and Rh, preventing direct contact and alloy formation. These intermediary substances allow the metals to be in close proximity for catalytic efficiency while maintaining chemical independence, thus achieving both simplicity and alloy prevention.
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 1-layer catalyst design simplifies manufacturing, reduces costs, and maintains or exceeds the performance of 2-layer designs by preventing alloy formation between palladium and rhodium, ensuring effective reduction of exhaust components like NOx, HC, and CO, while being more cost-effective.
Implementation Method 1
greater than or equal to about 70 wt % of the first catalyst metal and the second catalyst metal is non-alloyed under alloying conditions
Implementation Method 2
catalyst layer comprising a first catalyst metal and a second catalyst metal... effective reduction of exhaust components like NOx, HC, and CO
Implementation Method 3
the aluminum oxide and the storage component have average pore diameters of about 150 angstroms to about 1,000 angstroms
Implementation Method 4
about 50% to about 80% of the pore volume, based on the total pore volume comprise pores having average pore diameters of about 180 angstroms to about 800 angstroms
Data Source
AI summary
An exhaust treatment device, comprises a substrate; a catalyst layer deposited on the substrate, the catalyst layer comprising a first catalyst metal and a second catalyst metal, wherein greater than or equal to about 70 wt % of the first catalyst metal and the second catalyst metal is non-alloyed under alloying conditions, wherein the weight percent is based on a combined weight of the first catalyst metal and the second catalyst metal. The first catalyst metal and the second catalyst metal are different and may be individually selected from the group consisting of platinum, palladium, rhodium, rhenium, iridium, ruthenium, and osmium.