Wall-flow Filter with Combined Soot Oxidation and NH3-SCR Catalyst
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Solution Overview
Problem
Current exhaust gas treatment technologies face challenges in effectively filtering particulate matter and converting oxides of nitrogen from internal combustion engines, particularly in reducing emissions to meet stringent regulatory standards while maintaining engine efficiency and durability.
Innovation Solution
A wall-flow filter with a catalyst comprising optionally stabilized ceria and metals like tungsten and iron, which catalyzes the selective reduction of nitrogen oxides and oxidizes carbon soot, is used to treat exhaust gases from both stationary and mobile sources, reducing the number of catalytic coatings and increasing catalyst density for improved performance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple catalytic coatings are used to treat both particulate matter and nitrogen oxides, then emission reduction effectiveness is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple catalytic functions into a single coating layer containing both soot oxidation catalyst (precious metal like Pt, Pd, or Rh) and NOx reduction catalyst (base metal oxide like Cu, Fe, or Zn). This single integrated coating performs both particulate matter oxidation and nitrogen oxide reduction simultaneously, eliminating the need for separate catalytic layers while maintaining emission reduction effectiveness
Solution Approach 2:
The catalyst coating is designed with multi-functionality to handle multiple emission components (soot and NOx) through a single layer. The coating contains metal particles that can catalyze both oxidation reactions (for soot) and reduction reactions (for NOx), making the filter system universally effective against different types of emissions without requiring separate specialized layers
2Productivity
If catalyst density is increased to improve performance, then emission conversion efficiency is improved, but backpressure increases
Solution Approach 1:
The patent optimizes catalyst particle size parameters, using metal particles in the range of 0.1-10 micrometers (preferably 0.5-5 micrometers). This specific size range provides sufficient catalytic surface area for high conversion efficiency while maintaining appropriate porosity and flow characteristics to limit backpressure increases. The particle size parameter is carefully controlled to balance activity and flow resistance
Solution Approach 2:
The catalyst coating uses composite material structure combining precious metal particles with base metal oxide supports (such as CuO, Fe2O3, ZnO). This composite approach enhances catalytic activity per unit mass, allowing effective emission conversion with lower overall catalyst loading, thereby reducing the density-related backpressure while maintaining high conversion efficiency
3Reliability
If precious metal catalyst is used for soot oxidation, then catalytic activity is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs composite catalyst materials combining precious metal particles (for soot oxidation) with base metal oxide supports (CuO, Fe2O3, ZnO). The base metal oxides provide structural support and additional catalytic functionality at lower cost, allowing reduced precious metal loading while maintaining overall catalytic activity. This composite approach reduces manufacturing cost compared to using precious metals alone
Solution Approach 2:
The base metal oxide components in the composite catalyst provide multi-functionality, contributing to both soot oxidation and NOx reduction reactions. This reduces the reliance on expensive precious metals for all catalytic functions, as the base metals contribute to overall catalytic activity, thereby lowering manufacturing cost while preserving catalytic 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 solution enhances the efficiency of exhaust gas treatment by reducing backpressure, improving catalyst performance, and meeting stringent emission standards, while also promoting the combustion of soot and reducing nitrogen oxides, thus addressing the limitations of existing technologies.
Implementation Method 1
a catalyst for catalysing the conversion of solid carbon in the particulate matter by oxygen
Implementation Method 2
a catalyst for catalysing the selective reduction of oxides of nitrogen in the exhaust gas with a nitrogenous reductant
Implementation Method 3
NH3-SCR reaction
Data Source
AI summary
A wall-flow filter for filtering particulate matter from a flowing exhaust gas comprises a catalyst for catalyzing both the conversion of solid carbon in the particulate matter by oxygen and the selective reduction of oxides of nitrogen in the exhaust gas with a nitrogenous reductant, which catalyst comprising optionally stabilized ceria and at least one metal selected from (i) tungsten and (ii) both tungsten and iron.