Wall Flow Filter with Outlet SCR Catalyst Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current diesel engine exhaust treatment systems face challenges in managing backpressure and maintaining catalytic activity over varying temperatures, particularly with SCR catalysts used in wall flow filters, which affects NOx reduction and particulate matter filtration efficiency.
Innovation Solution
A catalytic article with a wall flow filter design where the SCR catalyst is predominantly distributed in the outlet portion of the porous walls, allowing NO2 to react with soot in the inlet portion and reducing backpressure, while maintaining high NOx conversion efficiency even at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SCR catalyst is loaded uniformly throughout the porous walls of the wall flow filter, then NOx conversion efficiency is improved, but backpressure increases and catalyst volume/weight increases
Solution Approach 1:
The patent applies local quality by concentrating the SCR catalyst in the outlet portion of the porous walls rather than distributing it uniformly throughout. This creates a non-uniform catalyst distribution where the outlet portion (within 60% of cross-sectional thickness from the outlet) contains substantially all the catalyst, while the inlet portion remains substantially free of catalyst. This resolves the contradiction by maintaining high NOx conversion efficiency in the region where it is most needed (outlet side) while minimizing catalyst volume and reducing backpressure.
2Reliability
If SCR catalyst loading is increased to maintain catalytic activity over time, then NOx reduction efficiency is improved, but backpressure increases
Solution Approach 1:
The patent resolves this contradiction by concentrating the catalyst in the outlet portion where it provides maximum effectiveness for NOx reduction, while minimizing the overall catalyst volume needed. The localized high-concentration distribution in the outlet portion ensures sufficient catalytic activity and durability without requiring excessive catalyst loading that would increase backpressure.
3Stress or pressure
If catalyst volume is reduced to decrease backpressure, then backpressure is reduced, but NOx conversion efficiency decreases
Solution Approach 1:
The patent resolves this contradiction by strategically concentrating the catalyst in the outlet portion of the porous walls where it is most effective for NOx conversion. This localized distribution maximizes the utility of each unit of catalyst volume, achieving high NOx conversion efficiency with minimal catalyst quantity, thereby reducing backpressure without sacrificing performance.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a uniform three-dimensional distribution of catalyst throughout the wall thickness to a concentrated distribution in a specific region (outlet portion within 60% of cross-sectional thickness). This spatial reorganization in the wall thickness dimension allows the system to achieve the same or better NOx conversion efficiency with reduced total catalyst volume.
4Reliability
If catalyst is distributed throughout the entire wall thickness, then catalytic activity is maintained across the entire filter, but the inlet portion catalyst reduces soot combustion efficiency
Solution Approach 1:
The patent resolves this contradiction by creating distinct functional zones: the inlet portion is substantially free of catalyst to allow efficient soot combustion and accumulation, while the outlet portion contains substantially all the SCR catalyst for effective NOx conversion. This local quality differentiation ensures that each region performs its intended function optimally without interference from catalyst presence in inappropriate locations.
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 effectively minimizes backpressure and achieves high NOx conversion and particulate matter filtration, ensuring efficient diesel engine exhaust treatment with reduced catalyst volume and weight, while maintaining catalytic activity over a wide temperature range.
Implementation Method 1
an SCR catalyst composition disposed on the wall flow filter such that substantially all of the catalyst is distributed in the outlet portion of the porous walls
Implementation Method 2
a plurality of longitudinally extending passages formed by longitudinally extending porous walls having substantially uniform porosity in cross-section
Implementation Method 3
oxidation catalysts that contain platinum group metals, base metals and combinations thereof are known to facilitate the treatment of diesel engine exhaust by promoting the conversion of both HC and CO gaseous pollutants and some proportion of the particulate matter through oxidation of these pollutants to carbon dioxide and water
Data Source
AI summary
Provided are selective catalytic reduction catalytic articles, emission treatment systems and methods for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The catalytic articles have a Selective Catalytic Reduction (SCR) catalyst uniformly coated over the outlet portion of wall flow filter walls resulting in reduction of NO2 and combustion of the soot without substantially increasing the system backpressure.