Asymmetric Wall-Flow Filter Washcoat Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current catalytic filtration systems for vehicular exhaust gases face challenges in achieving efficient NOx and soot removal due to the competition between reactions and high energy consumption in multi-step coating processes, which result in increased backpressure and resource utilization.
Innovation Solution
A catalysed wall-flow filter design with asymmetric honeycomb substrates, where the catalytic washcoat is applied differently to channels based on hydraulic diameter, allowing for selective coating on either channel walls or within the channels, and using a low-temperature setting cement for end-plugging to reduce process steps and energy requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-step coating processes are used to apply catalytic washcoat, then catalytic activity is improved, but process complexity and energy consumption increase
Solution Approach 1:
The patent combines multiple coating steps into a single washcoat application step. By formulating the washcoat slurry to contain catalyst precursors that are deposited simultaneously with the washcoat material, the process integrates what would traditionally require separate coating and catalyst impregnation steps, thereby reducing process complexity while maintaining catalytic activity
Solution Approach 2:
The washcoat slurry serves multiple functions simultaneously: it provides the structural washcoat layer, delivers catalyst precursors to the substrate, and creates the catalytic active sites. This multi-functional approach eliminates the need for separate coating and catalyst application processes, reducing both process complexity and energy consumption
2Reliability
If multi-step coating processes are used to apply catalytic washcoat, then catalytic activity is improved, but energy consumption increases
Solution Approach 1:
The patent combines multiple coating steps into a single washcoat application step. By formulating the washcoat slurry to contain catalyst precursors that are deposited simultaneously with the washcoat material, the process integrates what would traditionally require separate coating and catalyst impregnation steps, thereby reducing process complexity while maintaining catalytic activity
Solution Approach 2:
The catalyst precursors are pre-incorporated into the washcoat slurry before application. This preliminary incorporation ensures that the catalyst material is already positioned on the substrate when the washcoat is applied, eliminating the need for subsequent high-temperature calcination or catalyst activation steps that would consume additional energy
3Manufacturing precision
If asymmetric honeycomb substrates with different channel hydraulic diameters are used, then washcoat distribution is optimized, but manufacturing complexity increases
Solution Approach 1:
The patent employs an asymmetric honeycomb substrate design where inlet channels and outlet channels have different hydraulic diameters. This asymmetry creates differential capillary pressures during washcoat application, causing the washcoat slurry to be preferentially drawn into channels with larger hydraulic diameters. The result is optimized washcoat distribution that concentrates catalytic material where it is most needed, while the asymmetric geometry itself is a straightforward structural feature that does not significantly complicate manufacturing
4Reliability
If washcoat is applied to all channels, then catalytic activity is maximized, but backpressure increases
Solution Approach 1:
The patent applies washcoat preferentially to outlet channels rather than uniformly to all channels. The asymmetric honeycomb substrate design with larger outlet channel hydraulic diameters creates capillary forces that draw the washcoat slurry primarily into outlet channels during the coating process. This local concentration of catalytic material maximizes catalytic activity in the regions where it is most needed for exhaust gas treatment, while leaving inlet channels with minimal or no washcoat coating, thereby reducing overall backpressure across the filter
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 design enhances NOx and soot removal efficiency while reducing backpressure and resource utilization by optimizing washcoat distribution and simplifying the coating process, allowing for improved performance with less energy and equipment usage.
Implementation Method 1
the liquid catalytic washcoat remains on a surface of the porous channel walls of the first channels or both remains on the surface of the porous channel walls and permeates the porous channel walls of the first channels
Implementation Method 2
a catalytic selective catalytic reduction (SCR) catalyst coating is disposed within a porous channel wall of the wall-flow filter and only on the outlet-wall because this design maximises both NO x removal and NO 2 -soot removal
Data Source
Figure 1A~2B
Figure 3~4
Figure 5~6
AI summary
A catalysed honeycomb wall-flow filter for treating exhaust gas comprising particulate matter emitted from an internal combustion engine, which filter comprising a honeycomb substrate having a first end and a second end and comprising an array of interconnecting porous walls defining an array of longitudinally extending first channels and second channels, wherein the first channels are bordered on their sides by the second channels and have a larger hydraulic diameter than the second channels, wherein the first channels are end-plugged at a first end of the honeycomb substrate and the second channels are end-plugged at a second end of the honeycomb substrate, wherein channel wall surfaces of the first channels comprise an on-wall-type catalytic washcoat. The invention also relates to an exhaust system comprising the catalysed filter and to methods of making it.