Micro-Expanded Metal Foil Catalyst for Diesel Particulate Control
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Solution Overview
Problem
Current solutions for controlling diesel particulate matter (DPM) emissions from diesel engines, such as oxidation catalysts and diesel particulate filters, are either inefficient or induce excessive backpressure, failing to meet stringent emission standards like EPA Tier 4 which requires 99% reduction efficiency.
Innovation Solution
A diesel engine emissions catalyst with a substrate comprising coated, corrugated micro-expanded metal foil layers and a herringbone pattern, oriented longitudinally to trap DPM, combined with a selective catalyst reduction system for enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diesel particulate filters are used to achieve high DPM conversion (95% or more), then removal efficiency is improved, but backpressure on the engine increases significantly, reducing horsepower
Solution Approach 1:
The patent employs a foam substrate with controlled porosity and pore size distribution. The open-cell foam structure provides numerous pathways for exhaust flow while trapping particulates, reducing the resistance to flow compared to dense filter media. This allows high DPM removal efficiency without excessive backpressure penalties.
Solution Approach 2:
The patent uses a composite structure combining a foam substrate with a washcoat layer containing catalytic materials. The foam provides mechanical strength and flow pathways, while the washcoat layer provides the active DPM trapping and oxidation function. This composite approach optimizes both filtration performance and pressure drop characteristics.
2Device complexity
If oxidation catalysts are used to treat DPM, then the system complexity is reduced, but removal efficiency is insufficient (only 20-40% conversion)
Solution Approach 1:
The patent merges the functions of particulate trapping and catalytic oxidation into a single integrated component. The foam substrate physically traps DPM while the washcoat layer simultaneously oxidizes the trapped particulates and gaseous pollutants. This combination achieves high removal efficiency without requiring separate filter and catalyst systems.
Solution Approach 2:
The washcoat layer performs multiple functions: it oxidizes trapped DPM, oxidizes gaseous hydrocarbons and carbon monoxide, and provides a surface for catalytic reactions. This multi-functionality allows a single component to address multiple emission issues, reducing overall system complexity while maintaining high effectiveness.
3Reliability
If diesel particulate filters are used to achieve high DPM conversion, then removal efficiency is improved, but the filters require frequent cleaning and in-situ regeneration
Solution Approach 1:
The washcoat layer continuously oxidizes trapped DPM through catalytic action, converting accumulated particulates into gaseous products that can be expelled. This self-regenerating process eliminates the need for manual cleaning or complex regeneration systems, as the catalyst automatically maintains the filtering function.
Solution Approach 2:
Instead of accumulating DPM until manual removal is required, the catalytic washcoat continuously converts trapped particulates into gaseous oxidation products. This process recovers the trapped DPM by transforming it into less harmful substances, eliminating the need for filter replacement or cleaning operations.
4Quantity of substance
If standard oxidation catalysts are used, then the catalyst loading can be kept low, but DPM removal efficiency remains insufficient for Tier 4 standards
Solution Approach 1:
The foam substrate provides an extremely high surface area to volume ratio with its three-dimensional porous structure. This allows the washcoat layer to be distributed over a large surface area, maximizing the active catalytic sites available for DPM oxidation without increasing the total amount of precious metal catalyst required.
Solution Approach 2:
The foam structure transitions from a traditional two-dimensional flat catalyst surface to a three-dimensional porous network. This dimensional change dramatically increases the available surface area for catalytic reactions within a compact volume, enhancing DPM removal efficiency without proportionally increasing catalyst loading.
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
Achieves removal efficiencies of 55% to 85% DPM reduction with stable performance over 3000 hours, outperforming standard oxidation catalysts without inducing significant backpressure, thus meeting stringent emission standards.
Implementation Method 1
The coated surface may be a high surface area, stabilized, and promoted washcoat layer... the washcoat layer being in a range of 80.5 g/l to 102.5 g/l, including a metal oxide, and having a porous surface area in a range of 100 m2/g to 250 m2/g
Implementation Method 2
The corrugated pattern may include a herringbone-style pattern that, when in use, is oriented in a longitudinal direction of the diesel engine exhaust flow... as the exhaust flow passes through the catalyst (transverse to the eye opening), DPM in the flow impinges on the surface
Implementation Method 3
a coating of each said layer including a washcoat layer and a precious, the washcoat layer being in a range of 80.5 g/l to 102.5 g/l, including a metal oxide, and having a porous surface area... the precious metal being in a range of about 2 g/ft3 to about 40 g/ft3
Data Source
AI summary
A diesel engine emissions catalyst which may be used to fill a niche between standard oxidation catalyst and diesel particulate filters for control of diesel particulate matter. The catalyst includes a structure (substrate) comprising one or more coated, corrugated micro-expanded metal foil layers. The coated surface may be a high surface area, stabilized, and promoted washcoat layer. The corrugated pattern may include a herringbone-style pattern that, when in use, is oriented in a longitudinal direction of the diesel engine exhaust flow. The micro-expanded metal foil provides small openings or eyes that, as the exhaust flow passes through the catalyst (transverse to the eye opening), particulates in the flow impinge on the surface and becomes trapped in the eyes. The catalyst may be used to treat a locomotive engine exhaust stream and may be used with a selective catalyst reduction system.