Plasma-Deposited Composite Catalysts for Low Light-Off Temperature
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Solution Overview
Problem
Commercially available catalytic converters have high light-off temperatures, leading to increased emissions during short vehicular trips and catalyst degradation over time, necessitating reduced platinum group metal usage and improved performance.
Innovation Solution
The development of composite nanoparticle catalysts produced by plasma-based methods, which form nano-on-nano composite nanoparticles bonded to micron-sized carrier particles, reducing platinum group metal requirements and enhancing catalytic performance by maintaining a larger surface area over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If platinum group metal catalysts are deposited on substrates by wet chemistry methods, then catalytic activity is achieved, but light-off temperature remains high and catalyst degrades over time
Solution Approach 1:
The patent uses composite nanoparticle catalysts consisting of platinum group metals supported on metal oxide nanoparticles (1-100 nm), which are further supported on ceramic substrates. This multi-level composite structure provides high catalytic activity at lower temperatures while maintaining durability through the stable metal oxide support that prevents PGM migration and agglomeration.
Solution Approach 2:
The patent changes the physical and chemical parameters of the catalyst by using plasma-based synthesis methods to create nanoparticles with controlled size distribution (1-100 nm) and specific surface area. These parameter changes result in lower light-off temperatures and improved catalyst stability compared to conventional wet chemistry deposits.
2Reliability
If more platinum group metal catalysts are used, then catalytic performance improves, but manufacturing cost increases
Solution Approach 1:
The patent employs porous metal oxide nanoparticle supports with high surface area that can disperse and stabilize a high concentration of platinum group metal nanoparticles. This porous structure maximizes the utilization of PGM by providing numerous active sites per unit mass of catalyst, thereby reducing the total quantity of expensive PGM required while maintaining or improving catalytic performance.
Solution Approach 2:
The patent applies platinum group metals locally on the metal oxide nanoparticle surfaces rather than as bulk deposits. This localized distribution concentrates the catalytic activity where it is most needed at the gas-solid interface, improving efficiency and reducing the overall amount of PGM required.
3Area of stationary object
If conventional washcoat materials are used, then substrate coating is achieved, but catalyst surface area decreases over time due to aging
Solution Approach 1:
The patent extracts the catalyst from conventional washcoat matrices and places it on stable metal oxide nanoparticle supports. This separation allows the catalyst to maintain its nanoparticle morphology and high surface area without being constrained by the thermal and mechanical properties of traditional washcoat materials, thereby preserving surface area over the catalyst lifetime.
Solution Approach 2:
Instead of embedding catalyst particles in a washcoat matrix (conventional approach), the patent inverts the structure by using stable metal oxide nanoparticles as the primary support and applying thin washcoat layers only for mechanical anchoring. This inversion prioritizes catalyst surface area preservation and resistance to aging.
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 approach results in catalytic converters with lower light-off temperatures, reduced emissions, and prolonged efficacy by inhibiting platinum group metal migration and agglomeration, thus improving initial performance and longevity.
Implementation Method 1
composite nanoparticle catalysts produced by plasma-based methods, which form nano-on-nano composite nanoparticles bonded to micron-sized carrier particles
Implementation Method 2
washcoats that contain zeolites can be used to coat the substrate used in the catalytic converter... These zeolites act as a temporary storage area for the pollutants carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx)
Implementation Method 3
After the catalytic converter heats up to its operating temperature, known as the light-off temperature, the stored gases are released and subsequently decomposed by the catalytically active material on the substrate
Data Source
Figure 1~1A
Figure 2~3C
Figure 4
AI summary
Disclosed are, inter alia, methods of forming coated substrates for use in catalytic converters, as well as washcoat compositions and methods suitable for using in preparation of the coated substrates, and the coated substrates formed thereby, which in some cases use iron-exchanged zeolite particles that provide enhanced performance such as lower light-off temperatures and lower pollutant levels in exhaust gases. The catalytic material is prepared by a plasma-based method, yielding catalytic material with a lower tendency to migrate on support at high temperatures, and thus less prone to catalyst aging after prolonged use. Also disclosed are catalytic converters using the coated substrates, which have favorable properties as compared to catalytic converters using catalysts deposited on substrates using solution chemistry. Also disclosed are exhaust treatment systems, and vehicles, such as diesel vehicles, particularly light-duty diesel vehicles, using catalytic converters and exhaust treatment systems using the coated substrates.