Asymmetric Catalyst Coating for Diesel Particulate Filter Backpressure
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Solution Overview
Problem
Diesel particulate filters (DPFs) coated with high-performance catalysts like SCR catalysts experience increased backpressure, which negatively impacts engine performance and fuel economy, due to the coating's thickness and distribution, particularly when trying to reduce soot and NOx emissions in lean-burn combustion exhaust gases.
Innovation Solution
Coating the diesel particulate filter's inlet side with a catalyst washcoat having a d50 particle size distribution less than the mean pore size divided by 4.9, while keeping the outlet side substantially free of catalyst coating, to minimize backpressure and maintain effective soot and NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-performance catalyst washcoat is applied to a wall-flow filter substrate to reduce soot and NOx emissions, then emission reduction effectiveness is improved, but backpressure across the filter increases
Solution Approach 1:
The patent applies catalyst washcoat only to the inlet side of the wall-flow filter substrate, creating a non-uniform distribution where the inlet side has catalytic activity and the outlet side remains substantially free of catalyst coating. This local quality approach maintains emission reduction effectiveness at the inlet while minimizing backpressure buildup that would occur with full-surface coating.
Solution Approach 2:
The patent creates an asymmetric catalyst distribution by coating only the inlet side of the filter substrate. This asymmetric approach allows the catalyst to be positioned where it is most needed (inlet side for soot and NOx reduction) while avoiding the penalty of coating the entire surface, thereby reducing backpressure compared to symmetric full-surface coating.
2Reliability
If the catalyst washcoat particle size is reduced to improve catalytic activity, then emission reduction effectiveness is improved, but the coating occupies more pore space increasing backpressure
Solution Approach 1:
The patent specifies a particular particle size parameter for the catalyst washcoat with d50 less than the mean pore size divided by 4.9. This precise parameter control optimizes the balance between catalytic activity (sufficiently small particles) and backpressure minimization (particles small enough to not excessively block pores).
3Reliability
If the catalyst coating thickness is increased to improve emission reduction, then catalytic performance is improved, but backpressure increases and engine performance decreases
Solution Approach 1:
The patent applies catalyst coating only to the inlet side of the filter substrate, creating a localized catalytic zone. This provides sufficient catalytic performance for emission reduction while limiting the total coating thickness and volume, thereby minimizing the impact on exhaust flow and engine performance.
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 significantly reduces soot-loaded backpressure across the filter compared to even or outlet-side-only coatings, enhancing engine performance and fuel efficiency while maintaining effective emission reduction.
Implementation Method 1
a catalyst composition coated from the inlet side of the substrate, wherein the catalyst composition has a d50 particle size distribution, wherein said d50 particle size distribution is less than the mean pore size divided by 4.9 ± 0.1
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Provided is a diesel particulate filter capable of removing soot from an exhaust gas while operating at low backpressure, the filter comprising (a) a wall-flow filter substrate having a mean pore size, an inlet side, an outlet side, and a porous interior between the inlet and outlet sides; and (b) a catalyst composition coated from the inlet side of the substrate, wherein the catalyst composition has a d50 particle size distribution, wherein the d50 particle size distribution is less than the mean pore size divided by 4.9, and wherein the outlet side is substantially free of a catalyst coating.