Wall-Flow Catalyst Filter Coating for Sub-23 Nm Particle Control
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Solution Overview
Problem
Existing catalysts struggle to efficiently filter fine particulate emissions smaller than 23 nm from positive ignition engines, leading to challenges in meeting stringent emission standards while maintaining acceptable backpressure.
Innovation Solution
A catalyst article comprising a wall-flow filter with a combination of nano-sol cerium/zirconium mixed oxide and inorganic oxides, such as alumina, applied in a zoned manner to achieve effective filtration of sub-23 nm particles, using a combination of sub-micron and micron-scale particles with specific particle size distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional catalyst coating is used, then the backpressure is acceptable, but the filtration efficiency for sub-23 nm particles is insufficient
Solution Approach 1:
The patent changes the particle size parameter of the catalyst coating from conventional micron-scale to a bimodal distribution including sub-micron (0.1-1 μm) and nano-scale (10-100 nm) particles. This parameter change enables the coating to effectively capture sub-23 nm particles through diffusion and impaction mechanisms while maintaining acceptable backpressure levels.
Solution Approach 2:
The patent employs a composite catalyst coating combining two distinct particle size populations (sub-micron and nano-scale) with different functional properties. The sub-micron particles provide structural support and catalytic activity, while the nano-scale particles enhance filtration efficiency for ultrafine particles, creating a synergistic composite material system.
2Manufacturing precision
If a finer catalyst coating is used to improve sub-23 nm particle filtration, then the filtration efficiency increases, but the backpressure increases
Solution Approach 1:
The patent applies local quality by creating a bimodal particle size distribution within the catalyst coating, where different regions and particle sizes serve different functions. The sub-micron particles handle bulk catalytic conversion, while the nano-scale particles locally enhance filtration of sub-23 nm particles, optimizing performance without uniformly increasing backpressure across the entire system.
Solution Approach 2:
The patent changes the particle size parameter from a single-scale to a bimodal distribution, enabling the coating to achieve high filtration efficiency for sub-23 nm particles through the nano-scale component while the sub-micron component maintains porosity and flow characteristics that prevent excessive backpressure buildup.
3Manufacturing precision
If a single particle size distribution is used, then the manufacturing is simple, but the filtration efficiency for different particle sizes is compromised
Solution Approach 1:
The patent changes the particle size parameter from a single-value specification to a bimodal distribution with defined ranges (sub-micron: 0.1-1 μm, nano-scale: 10-100 nm). This parameter change enables the coating to address multiple particle size regimes simultaneously, achieving high filtration efficiency for sub-23 nm particles while maintaining compatibility with existing manufacturing processes.
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 significantly reduces particulate emissions below 23 nm by at least 20-40% and maintains low backpressure, addressing health risks and meeting future legislative requirements beyond Euro 6d standards.
Implementation Method 1
The catalyst article comprises a substrate which is a wall-flow filter having an inlet end and an outlet end and an axial length L therebetween, a plurality of inlet channels extending from the inlet end and a plurality of outlet channels extending from the outlet end
Implementation Method 2
The first and second catalyst compositions overlap by at most 80% of L
Implementation Method 3
The active components in a typical TWC comprise one or both of platinum and palladium in combination with rhodium, or even palladium only (no rhodium), supported on a high surface area oxide, and an oxygen storage component
Implementation Method 4
oxidation of carbon monoxide to carbon dioxide, (ii) oxidation of unburned hydrocarbons to carbon dioxide and water
Implementation Method 5
This was achieved by the development of the oxygen storage component that liberates or absorbs oxygen during the perturbations
Implementation Method 6
The most commonly used oxygen storage component (OSC) in modern TWCs is cerium oxide (CeO2) or a mixed oxide containing cerium, e.g. a Ce/Zr mixed oxide
Data Source
Figure 1~2
Figure 3
AI summary
The present invention provides a catalyst article and its use in an exhaust system for internal combustion engines. The catalyst article catalyst article comprises: • a substrate which is a wall-flow filter having an inlet end and an outlet end and an axial length L therebetween, a plurality of inlet channels extending from the inlet end and a plurality of outlet channels extending from the outlet end, • wherein the plurality of inlet channels comprise a first catalyst composition extending from the inlet or outlet end for at least 50% of L and the plurality of outlet channels comprise a second catalyst composition extending from the outlet or inlet end for at least 50% of L, wherein the first and second catalyst compositions overlap by at most 80% of L, and • wherein the first and second catalyst compositions each independently comprise a particulate oxygen storage component (OSC) having a first D90 and a particulate inorganic oxide having a second D90 and: • i) the first D90 is less than 1 micron and the second D90 is from 1 to 20 microns; or • ii) the second D90 is less than 1 micron and the first D90 is from 1 to 20 microns.