Gasoline Particulate Filter Washcoat for Low Back-Pressure
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Solution Overview
Problem
Existing gasoline particulate filters (GPFs) face issues with undue back-pressure and inadequate conversion of CO, NOx, and HC due to catalyst coatings, and there is a need for improved manufacturing methods that enhance catalytic activity and reduce back-pressure.
Innovation Solution
A method for manufacturing a GPF involving the formation of a washcoat slurry with platinum group metals, oxygen storage capacity materials, and C2-C6 aliphatic amino acids, followed by coating and calcining a wall-flow filter substrate, which includes spraying or dipping to ensure deep penetration of the slurry into the substrate pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst coating is applied to the GPF to improve CO, NOx and HC conversion properties, then catalytic activity is enhanced, but back-pressure increases unduly
Solution Approach 1:
The patent employs a porous washcoat material (e.g., alumina, silica, or mixed oxides) as the catalyst support. The porous structure provides high surface area for catalytic activity while maintaining open pathways for exhaust flow, thus achieving both high conversion efficiency and low back-pressure. The pore size and distribution are optimized to balance catalytic performance with flow resistance.
Solution Approach 2:
The catalyst coating is formulated as a composite material comprising active catalytic components (precious metals like Pt, Pd, Rh), support material (washcoat), and promotional additives (e.g., oxygen storage components like ceria). This composite structure synergistically enhances catalytic activity while the support matrix maintains structural integrity and minimizes flow resistance.
2Reliability
If the catalyst coating is made thicker to improve conversion properties, then CO, NOx and HC conversion is enhanced, but back-pressure increases
Solution Approach 1:
The catalyst coating is applied with non-uniform thickness distribution optimized for different functional requirements. The washcoat layer is thicker at the inlet end where catalytic conversion is most needed, and gradually thinner toward the outlet end where flow resistance would otherwise become excessive. This gradient structure achieves high conversion efficiency while minimizing back-pressure.
Solution Approach 2:
The use of highly porous washcoat materials allows for adequate catalytic active sites within a thinner effective layer, reducing the need for thick coatings that would increase back-pressure. The high porosity provides large surface area-to-volume ratio, enabling effective catalysis with minimal material thickness.
3Strength
If standard washcoat materials are used to ensure structural integrity, then filter strength is maintained, but catalytic activity and slurry penetration are insufficient
Solution Approach 1:
The washcoat is formulated as a composite containing structural support materials (e.g., gamma-alumina, silica) combined with catalytically active components and promotional additives. This composite structure provides both mechanical strength for filter integrity and high catalytic activity through the incorporated metal particles and oxygen storage components.
Solution Approach 2:
The physical and chemical parameters of the washcoat material are optimized to balance strength and catalytic performance. Particle size distribution, surface area, pore size, and chemical composition are carefully controlled to achieve adequate mechanical strength while maximizing catalytic activity and slurry penetration characteristics.
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 method reduces back-pressure and enhances catalytic performance, achieving significant reductions in NOx and improved CO and THC light-off temperatures.
Implementation Method 1
coating a wall-flow filter substrate with the washcoat slurry to form a washcoated substrate
Implementation Method 2
calcining the washcoated substrate to form a GPF
Data Source
AI summary
A method for the manufacture of a gasoline particulate filter (GPF) for the treatment of an exhaust gas is disclosed. The method comprises (i) forming a washcoat slurry; (ii) coating a wall-flow filter substrate with the washcoat slurry to form a washcoated substrate; and (iii) calcining the washcoated substrate to form a gasoline particulate filter. The washcoat slurry comprises (a) a platinum group metal selected from the group consisting of Pt, Pd, Rh and mixtures thereof; (b) an oxygen storage capacity (OSC) material; and (c) a C2-C6 aliphatic amino acid.