Manganese Diesel Oxidation Catalyst for Sulfur-Tolerant NO2 Control
Solution Overview
Problem
Existing diesel oxidation catalysts face challenges in efficiently removing carbon monoxide, hydrocarbons, and nitrogen oxides from diesel engine exhaust gases while maintaining insensitivity to sulfur compounds and ensuring a favorable NO to NO2 ratio for downstream SCR catalysts, particularly in the presence of high oxygen content and particulate emissions.
Innovation Solution
A diesel oxidation catalyst comprising a support body with a catalytically active material zone containing palladium and platinum supported on a manganese-containing support oxide, where the manganese-containing support oxide is doped with lanthanum, and a secondary material zone with platinum and palladium on various oxides, excluding zeolites, to enhance oxidation efficiency and NO to NO2 conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional oxidation catalysts with precious metals are used, then oxidation efficiency is improved, but sensitivity to sulfur compounds increases
Solution Approach 1:
The patent employs a composite material system consisting of a cordierite substrate coated with multiple layers: a washcoat layer containing aluminum oxide, manganese oxide, and precious metals (platinum and palladium), and an overcoat layer containing manganese oxide and precious metals. This composite structure combines the high oxidation efficiency of precious metals with the sulfur resistance of manganese oxide, resolving the contradiction between productivity and reliability.
Solution Approach 2:
Manganese oxide serves as an intermediary substance between the precious metals and the sulfur-containing exhaust gases. It acts as a protective barrier that reduces sulfur exposure to the precious metals while maintaining their oxidation activity, thus improving sulfur resistance without sacrificing oxidation efficiency.
2Productivity
If oxidation catalysts are used to remove CO and HC, then emission cleanup is improved, but the NO to NO2 ratio becomes unfavorable for downstream SCR catalysts
Solution Approach 1:
The catalyst composition is specifically designed with controlled ratios of precious metals (Pt and Pd) and manganese oxide to adjust the oxidation parameters. By optimizing the metal loading and oxide composition, the catalyst achieves balanced oxidation activity that converts CO and HC while maintaining a favorable NO to NO2 ratio (typically NO2/NOx < 0.5) for downstream SCR operation.
Solution Approach 2:
The catalyst structure creates different functional zones: the washcoat layer primarily handles CO and HC oxidation, while the overcoat layer with manganese oxide and precious metals provides selective oxidation activity for NO to NO2 conversion control. This spatial differentiation of functions allows simultaneous optimization of emission cleanup and SCR compatibility.
3Productivity
If catalyst layers are added to improve functionality, then oxidation performance is improved, but device complexity increases
Solution Approach 1:
The catalyst is segmented into two distinct functional layers: a washcoat layer (5-20 µm thick) containing aluminum oxide, manganese oxide, and precious metals for CO and HC oxidation, and an overcoat layer (2-10 µm thick) containing manganese oxide and precious metals for NOx management. This segmentation allows each layer to be optimized for its specific function while maintaining overall system simplicity.
Solution Approach 2:
The manganese oxide component serves multiple functions simultaneously: it acts as a sulfur trap to protect precious metals, provides oxygen storage capacity to maintain oxidation activity under varying conditions, and contributes to NOx oxidation control. This multi-functionality reduces the need for additional separate components, thereby managing device complexity.
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 effectively oxidizes carbon monoxide and hydrocarbons, converts nitrogen monoxide to nitrogen dioxide, and establishes an optimal NO to NO2 ratio, improving the performance of downstream SCR catalysts and maintaining catalyst longevity despite high oxygen and sulfur resistance.
Implementation Method 1
carbon monoxide and hydrocarbons are rendered harmless by oxidation using a suitable oxidation catalyst
Implementation Method 2
oxidation catalysts often serve to establish an optimal NO to NOz ratio for an downstream SCR catalyst
Implementation Method 3
a catalytically active material zone (A) arranged on the support body, wherein the material zone (A) contains palladium and platinum supported on a manganese-containing support oxide
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a diesel oxidation catalyst, which comprises a carrier body having a length L extending between a first end face a and a second end face b and a catalytically active material zone A arranged on the carrier body, wherein the material zone A contains palladium and platinum on a manganese-containing carrier oxide, wherein the carrier oxide consists of a carrier oxide component A and a carrier oxide component B and the carrier oxide component B consists of manganese and/or a manganese compound and is present in an amount of 5 to 15 wt.%, calculated as MnO2 and based on the total weight of the manganese-containing carrier oxide.