Catalytic Wall-Flow Monolith for Gasoline Emission Control
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Solution Overview
Problem
Current emission treatment systems for gasoline engines, particularly gasoline direct injection engines, face challenges in effectively reducing particulate matter (PM) emissions while meeting stringent standards for nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons, while also maintaining acceptable back pressure.
Innovation Solution
A catalytic wall-flow monolith is designed with a porous substrate coated throughout with a three-way catalyst (TWC) composition, including alumina, platinum group metals, and an oxygen storage component (OSC) in a specific ratio, which allows for varying platinum group metal distribution and coating thickness to enhance catalytic activity and reduce backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-way catalyst is coated on a wall-flow monolith to combine TWC and particulate removal functions, then particulate capture capability is improved, but back pressure increases
Solution Approach 1:
The patent applies different catalyst compositions and coating thicknesses to different regions of the monolith. The inlet side receives a coating optimized for particulate capture, while the outlet side receives a coating optimized for catalytic conversion, with varying thicknesses to balance filtration efficiency and back pressure.
Solution Approach 2:
The patent utilizes the porous structure of the wall-flow monolith substrate itself as the primary filtration mechanism, allowing exhaust gases to pass through while trapping particulates. The porous coating materials are designed with controlled porosity to maintain low back pressure while ensuring effective particulate capture.
2Productivity
If a thick catalyst coating is applied to enhance catalytic activity, then emission conversion efficiency is improved, but back pressure increases
Solution Approach 1:
The patent specifies different coating thicknesses for different locations: the inlet side is coated with a thicker layer (e.g., 5-15 μm) to maximize particulate capture, while the outlet side has a thinner coating (e.g., 1-5 μm) to minimize back pressure while maintaining catalytic conversion efficiency.
Solution Approach 2:
The patent applies catalyst coating selectively where needed most - concentrated on the inlet side for particulate capture and moderately on the outlet side for conversion, rather than uniformly throughout. This partial application optimizes performance while controlling back pressure.
3Productivity
If platinum group metal content is increased to improve catalytic performance, then emission treatment effectiveness is improved, but manufacturing cost increases
Solution Approach 1:
The patent distributes platinum group metals non-uniformly throughout the catalyst coating, with higher concentrations in regions where they are most needed (e.g., inlet side for particulate oxidation) and lower concentrations in regions where other catalysts are sufficient (e.g., outlet side for CO and HC conversion).
Solution Approach 2:
The patent uses composite catalyst formulations combining multiple platinum group metals (Pt, Pd, Rh) with base metals and support materials like alumina and ceria. This composite approach enhances catalytic activity per unit of precious metal, improving effectiveness while controlling cost.
4Reliability
If a wall-flow monolith structure is used for particulate filtration, then particulate capture is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into a single integrated device: the wall-flow monolith simultaneously provides particulate filtration, catalytic conversion of gaseous emissions, and structural support. This merging eliminates the need for separate filters and catalysts, reducing overall system complexity despite the sophisticated internal structure.
Solution Approach 2:
The wall-flow monolith is designed as a multi-functional component that performs particulate capture, gas-phase catalytic reactions, and structural duties. The same physical structure serves multiple purposes, making the device universally applicable for comprehensive emission treatment.
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 effectively captures particulates and treats gaseous emissions, improving NOx conversion and reducing backpressure, thus meeting stringent emission standards and extending regeneration frequency.
Implementation Method 1
Such catalysts promote the oxidation by oxygen and oxides of nitrogen in the exhaust gas stream of unburned hydrocarbons and carbon monoxide
Implementation Method 2
Such catalysts promote the oxidation by oxygen and oxides of nitrogen in the exhaust gas stream of unburned hydrocarbons and carbon monoxide, as well as the concomitant reduction of nitrogen oxides to nitrogen
Implementation Method 3
an oxygen storage component (OSC), wherein the OSC comprises ceria or one or more mixed oxides comprising cerium
Data Source
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Figure 2
AI summary
A catalytic wall-flow monolith for use in an emission treatment systemcomprises a porous substrate and a three-way catalyst (TWC), wherein the TWC is distributed substantially throughout the porous substrate and wherein the TWC comprises: (i) alumina; (ii) one or more platinum group metals; and (iii) an oxygen storage component (OSC), wherein the OSC comprises ceria or one or more mixed oxides comprising cerium and is present in a ratio by weight of OSC to alumina of from 65:35 to 85:15