Layered Diesel Oxidation Catalyst for Low-Temperature NO2 Generation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing diesel oxidation catalysts struggle with low NO2 content at low temperatures, which hinders effective downstream SCR performance and require high light-off temperatures for CO and HC oxidation, especially in lean burn conditions with high sulfur levels.
Innovation Solution
A layered catalyst composite with a first washcoat layer containing platinum and palladium on a refractory metal oxide support and a second washcoat layer incorporating manganese and zeolite, enhancing NO oxidation to NO2 and reducing CO and HC emissions, particularly effective at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Pd-based catalysts are used to reduce cost compared to Pt, then cost is reduced, but light-off temperature increases and sulfur poisoning susceptibility increases
Solution Approach 1:
The patent combines Pd and Pt in a layered structure where the first layer contains Pd for cost reduction and the second layer contains Pt for low-temperature activity and sulfur resistance. This merging allows the system to benefit from both the cost advantage of Pd and the performance advantage of Pt without using either alone in full amounts.
Solution Approach 2:
The invention creates a composite catalyst structure with two distinct washcoat layers having different compositions and functions. The composite structure integrates the advantages of different metals (Pd for cost, Pt for performance) and different support materials (alumina for surface area, silica-alumina for thermal stability) to achieve overall superior performance.
2Ease of manufacture
If Pd-based catalysts are used instead of Pt, then cost is reduced, but susceptibility to sulfur poisoning increases
Solution Approach 1:
The patent combines Pd and Pt in a layered structure where the first layer contains Pd for cost reduction and the second layer contains Pt for low-temperature activity and sulfur resistance. This merging allows the system to benefit from both the cost advantage of Pd and the performance advantage of Pt without using either alone in full amounts.
Solution Approach 2:
The layered structure acts as an intermediary arrangement where the Pt-containing layer serves as a protective outer layer that is more resistant to sulfur poisoning, while the Pd-containing layer provides cost benefits underneath. The structure mediates between the conflicting requirements of cost and sulfur resistance.
3Productivity
If conventional oxidation catalysts are used, then CO and HC oxidation occurs, but NO2 content remains low at low temperatures hindering SCR performance
Solution Approach 1:
The patent applies local quality by creating distinct layers with different compositions optimized for different functions. The first layer is optimized for CO and HC oxidation, while the second layer is specifically designed to promote NO to NO2 conversion. This local optimization allows each layer to excel at its specific function rather than requiring a single uniform composition to do everything.
Solution Approach 2:
The catalyst is segmented into two separate washcoat layers, each performing a specific function. The first layer handles oxidation of CO and HC, while the second layer focuses on NO2 generation. This segmentation allows independent optimization of each function and prevents the trade-off that would exist in a single-layer system.
4Productivity
If high temperature operation is used to achieve efficient catalytic conversion, then conversion efficiency improves, but performance during cold-start period deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the catalyst by incorporating specific metal combinations (Pd and Pt) and support materials (alumina and silica-alumina) with different properties. This allows the catalyst to maintain high activity at lower temperatures through the synergistic effects of the layered structure, effectively changing the temperature-performance relationship.
Solution Approach 2:
The invention creates a composite catalyst structure with two distinct washcoat layers having different compositions and functions. The composite structure integrates the advantages of different metals (Pd for cost, Pt for performance) and different support materials (alumina for surface area, silica-alumina for thermal stability) to achieve overall superior performance across a wider temperature range.
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 composite improves NO2 content in exhaust gas, facilitating efficient SCR reactions at low temperatures and reducing light-off temperatures for CO and HC, thus enhancing overall emission abatement.
Implementation Method 1
oxidation catalyst catalytic material on the carrier substrate, the oxidation catalyst catalytic material including a first washcoat layer comprising a first refractory metal oxide support and a platinum (Pt) component and a palladium (Pd) component
Implementation Method 2
oxidation catalyst catalytic material on the carrier substrate, the oxidation catalyst catalytic material including a first washcoat layer comprising a first refractory metal oxide support and a platinum (Pt) component and a palladium (Pd) component
Implementation Method 3
a second washcoat layer comprising a second refractory metal oxide support containing Mn, a zeolite, and a Pt component
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat layer comprising a Pt component and a Pd component, and a second washcoat layer including a refractory metal oxide support containing manganese, a zeolite, and a platinum component is described.