Segmented Catalyst Coatings for NOx Reduction and N2O Suppression
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Solution Overview
Problem
Current catalyst systems face challenges in reducing nitrous oxide (N2O) formation while achieving effective NOx reduction, ammonia oxidation, and hydrocarbon oxidation, particularly under high engine-out NOx conditions, which are critical for meeting stringent emission regulations.
Innovation Solution
A catalyst system comprising a flow-through substrate with specific coatings: a first coating of vanadium oxide and zeolitic material with copper and iron, a second coating of platinum group metals supported on non-zeolitic oxidic materials, and optionally a third coating, optimized to enhance NOx conversion and reduce N2O formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Vanadium-SCR catalyst is used for fuel burn DOC and upstream SCR, then NOx reduction is improved, but N2O formation increases due to unselective DeNOx
Solution Approach 1:
The catalyst is divided into multiple functional zones along the flow path: a first zone with Vanadium-SCR catalyst for selective DeNOx, followed by a second zone with Platinum group metal catalyst for selective NH3 oxidation. This segmentation allows each zone to perform its specific function optimally, preventing N2O formation while maintaining NOx reduction efficiency.
Solution Approach 2:
Different catalyst materials are applied in different spatial locations within the catalyst structure. The Vanadium-SCR catalyst is placed in the first zone where NH3 is still available for selective DeNOx reactions, while the Platinum group metal catalyst is placed in the second zone where NH3 oxidation occurs. This local differentiation of material properties enables selective reactions at different locations.
2Device complexity
If SCR and oxidation functionality are mixed in a single catalyst, then device complexity is reduced, but N2O selectivity increases due to unselective oxidation of NH3
Solution Approach 1:
The catalyst is segmented into distinct functional zones: a first zone containing Vanadium-SCR catalyst material and a second zone containing Platinum group metal catalyst material. This segmentation maintains functional separation while keeping the overall catalyst as a single integrated component, balancing simplicity with selectivity.
Solution Approach 2:
The Vanadium-SCR catalyst zone is positioned upstream to perform selective DeNOx reactions before the exhaust gas reaches the Platinum group metal zone. This preliminary action ensures that NH3 oxidation occurs in a controlled manner in the second zone, preventing unselective oxidation and N2O formation.
3Loss of energy
If a standard EU VI/EPA13 system is used, then CO2 emissions are reduced, but engine-out NOx emissions increase beyond regulatory limits
Solution Approach 1:
The catalyst combines SCR (selective catalytic reduction) and DOC (diesel oxidation catalyst) functionalities in a single integrated component. The Vanadium-SCR catalyst provides DeNOx activity while the Platinum group metal catalyst provides oxidation capability, merging multiple emission control functions into one device to simultaneously address NOx and CO2 emission challenges.
Solution Approach 2:
The catalyst performs multiple functions: selective DeNOx reactions, NH3 oxidation, NO oxidation, and HC oxidation. This multi-functionality allows a single catalyst component to address multiple emission pollutants, making the system compatible with fuel economy improvements while meeting stringent NOx emission regulations.
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 catalyst system demonstrates improved catalytic activity for NOx, ammonia, and hydrocarbon oxidation while significantly reducing N2O formation, effectively addressing the limitations of existing systems in meeting stringent emission standards.
Implementation Method 1
a first coating comprising one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron
Implementation Method 2
the selective catalytic reduction of NOx
Implementation Method 3
a second coating comprising a first platinum group metal component supported on a non-zeolitic first oxidic material
Implementation Method 4
the oxidation of ammonia
Implementation Method 5
the oxidation of HC
Implementation Method 6
Vanadium-SCR catalysts have relatively good properties in the catalytic combustion of diesel fuel
Implementation Method 7
catalytic burn diesel fuel
Data Source
AI summary
The present invention relates to a catalyst for the oxidation of NO, for the oxidation of ammonia, for the oxidation of HC and for the selective catalytic reduction of NOx, comprising a flow through substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough; a first coating comprising one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron; a second coating comprising a first platinum group metal component supported on a non-zeolitic first oxidic material and further comprising one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron; optionally a third coating comprising a second platinum group metal component supported on a second oxidic material; wherein the third coating is disposed on the surface of the internal walls and under the second coating over z % of the axial length of the substrate from the outlet end to the inlet end, with z being in the range of from 0 to 100; wherein the second coating extends over y % of the axial length of the substrate from the inlet end to the outlet end and is disposed either on the surface of the internal walls, or on the surface of the internal walls and the third coating, or on the third coating, with y being in the range of from 95 to 100; wherein the first coating extends over x % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the second coating, with x being in the range of from 20 to y.