Gradient Coating on Gasoline Particulate Filter
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Solution Overview
Problem
Current emission treatment systems for positive ignition internal combustion engines face challenges in effectively reducing particulate matter (PM) emissions while maintaining efficient conversion of NOx, CO, and HC, especially under transient engine conditions, due to the difficulty in maintaining a stoichiometric air-to-fuel ratio and the need for high backpressure control.
Innovation Solution
A catalytic wall-flow monolith filter with a porous substrate and varying platinum group metal coating thickness along the longitudinal direction, incorporating a wedge-shaped coating profile and oxygen storage components, enhances three-way catalytic activity and reduces backpressure by optimizing the distribution of catalytic material on channel wall surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform thick coating of catalytic material is applied on channel wall surfaces, then catalytic activity is improved, but backpressure increases and manufacturing complexity increases
Solution Approach 1:
The patent applies a non-uniform coating thickness distribution where the coating is thicker at the inlet end and progressively thinner toward the outlet end of the monolith. This local variation in coating quality optimizes catalytic activity in regions where it is most needed (inlet) while reducing backpressure in downstream regions, resolving the contradiction between catalytic performance and flow resistance
Solution Approach 2:
The patent changes the physical parameter of coating thickness from a uniform value to a gradient distribution along the longitudinal axis of the monolith. This parameter change allows the system to achieve high catalytic activity where exhaust gases first contact the catalyst while maintaining lower backpressure overall, as the thinner downstream coating reduces flow resistance
2Reliability
If a uniform thick coating of catalytic material is applied on channel wall surfaces, then catalytic activity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent implements local quality variation in the coating thickness, with thicker coating at the inlet and thinner coating at the outlet. This approach achieves superior catalytic activity in the high-activity inlet region while simplifying the overall coating structure compared to attempting uniform thick coverage throughout, as the gradual thinning reduces manufacturing complexity
Solution Approach 2:
The patent introduces a dynamic or gradient coating thickness profile along the monolith length rather than a static uniform thickness. This dynamic variation in coating properties allows the system to adapt catalytic activity to the local exhaust gas composition and flow conditions at different positions, optimizing performance while managing manufacturing complexity
3Reliability
If a uniform thick coating of catalytic material is applied on channel wall surfaces, then catalytic activity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a controlled gradient in coating thickness from inlet to outlet, which provides clear manufacturing guidance for achieving the desired catalytic performance. This local quality specification is more manufacturable than requiring uniform thick coating throughout, as it allows progressive variation that is easier to control and inspect, reducing the stringency of precision requirements
Solution Approach 2:
The patent transforms the coating thickness parameter from a constant uniform value to a controlled gradient distribution. This parameter change simplifies manufacturing precision requirements because the gradual variation in thickness can be achieved through controlled coating processes, avoiding the need for extremely precise uniform application across the entire monolith surface
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 solution achieves improved PM reduction efficiency, enhanced NOx conversion, and reduced backpressure, meeting stringent Euro 6 emission standards while maintaining effective catalytic activity across varying engine conditions.
Implementation Method 1
the porous substrate has a first face and a second face defining a longitudinal direction therebetween and first and second pluralities of channels extending in the longitudinal direction, wherein the first plurality of channels is open at the first face and closed at the second face
Implementation Method 2
a first on-wall coating comprising catalytic material is present on at least the channel wall surfaces of the first plurality of channels, wherein the catalytic material on channel wall surfaces of the first plurality of channels comprises one or more platinum group metal
Implementation Method 3
an amount by weight of the one or more platinum group metal, per unit volume of the on-wall coating present on channel wall surfaces of the first plurality of channels varies continually along the longitudinal direction
Implementation Method 4
incorporating a wedge-shaped coating profile and oxygen storage components, enhances three-way catalytic activity
Data Source
AI summary
A catalytic wall-flow monolith filter having three-way catalytic activity for use in an emission treatment system of a positive ignition internal combustion engine comprising a porous filter substrate having a first face and a second face defining a longitudinal direction there between and first and second pluralities of channels extending in the longitudinal direction, wherein the first plurality of channels is open at the first face and closed at the second face and the channels of the first plurality of channels are defined in part by channel wall surfaces, wherein the second plurality of channels is open at the second face and closed at the first face and the channels of the second plurality of channels are defined in part by channel wall surfaces and wherein channel walls between the channel wall surfaces of the first plurality of channels and the channel wall surfaces of the second plurality of channels are porous, wherein a first on-wall coating comprising catalytic material having a layer thickness is present on at least the channel wall surfaces of the first plurality of channels, wherein the catalytic material on channel wall surfaces of the first plurality of channels comprises one or more platinum group metal selected from the group consisting of (i) rhodium (Rh) only; (ii) palladium (Pd) only; (iii) platinum (Pt) and rhodium (Rh); (iv) palladium (Pd) and rhodium (Rh); and (v) platinum (Pt), palladium (Pd) and rhodium (Rh) and a refractory metal oxide support, wherein: (i) an amount by weight of the one or more platinum group metal, per unit volume of the on-wall coating present on channel wall surfaces of the first plurality of channels varies continually along the longitudinal direction; and/or (ii) the layer thickness of the on-wall coating present on channel wall surfaces of the first plurality of channels varies continually along the longitudinal direction.