Dual-Coating Diesel Oxidation Catalyst for NOx and Heat-Up
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Solution Overview
Problem
Conventional oxidation catalysts fail to meet the requirements for use in combination systems with particle filters and SCR catalytic converters, particularly for heavy-duty diesel engines, due to insufficient NO oxidation activity, heat-up performance, and stability, leading to incomplete exhaust gas purification and potential non-compliance with emissions regulations.
Innovation Solution
A catalytic converter with two distinct catalytically active coatings on a ceramic or metallic honeycomb body, where the coating in direct contact with the exhaust gas has a higher platinum content for enhanced NO2 formation and oxidation activity, and the coating not in direct contact uses zeolites for improved heat-up performance and HC storage and conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single uniform catalytic coating is used, then the device complexity is reduced, but the NO oxidation activity and heat-up performance are insufficient
Solution Approach 1:
The patent applies a dual-layer coating structure where the first layer (exhaust gas side) contains platinum group metals for high NO oxidation activity, while the second layer (substrate side) contains zeolite for heat-up performance and HC storage. Each layer has locally optimized composition to perform its specific function, resolving the contradiction between uniform simplicity and functional performance.
Solution Approach 2:
The patent combines different material systems (platinum group metals and zeolite) in a composite coating structure. This allows the catalyst to leverage the oxidation activity of noble metals and the heat-up performance of zeolite, achieving superior overall performance compared to single-material coatings.
2Reliability
If the exhaust gas side coating has high Pt content for enhanced NO2 formation, then the oxidation activity is improved, but the cost and precious metal usage increase
Solution Approach 1:
The patent concentrates platinum group metals in the first layer where they are most needed for NO oxidation, while using zeolite in the second layer for heat-up functions. This localized distribution optimizes precious metal usage by placing them only where required for their specific chemical function.
Solution Approach 2:
The patent adjusts the composition parameters of each layer to achieve optimal performance. The exhaust gas side layer has high Pt content for oxidation activity, while the substrate side layer has zeolite for heat-up, creating a gradient composition that balances performance with precious metal consumption.
3Reliability
If the coating not in direct contact uses zeolites for heat-up performance, then the HC conversion is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent divides the coating into two distinct layers with different compositions and functions. The first layer handles oxidation and the second layer handles heat-up and HC storage. This segmentation allows each layer to be optimized for its specific manufacturing requirements and functional performance.
Solution Approach 2:
The patent assigns different material properties to different spatial locations within the coating. The exhaust gas-facing layer has properties optimized for oxidation catalysis, while the inner layer has properties optimized for heat-up performance and HC storage, allowing localized optimization without requiring complex overall manufacturing processes.
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 dual-coating design achieves high NO2 formation rates, complete HC conversion, and efficient heat-up performance, maintaining activity across varying operating conditions, reducing the need for frequent particle filter regeneration and ensuring compliance with emissions standards.
Implementation Method 1
The harmful gases carbon monoxide and hydrocarbons can easily be rendered harmless by oxidation on a suitable oxidation catalyst
Implementation Method 2
The harmful gases carbon monoxide and hydrocarbons can easily be rendered harmless by oxidation on a suitable oxidation catalyst
Implementation Method 3
The reduction of nitrogen oxides to nitrogen ('denitrogenation' of the exhaust gas) is difficult because of the high oxygen content. A well-known process is the selective catalytic reduction (Selective Catalytic Reduction SCR) of nitrogen oxides on a suitable catalyst
Implementation Method 4
The ammonia that may be generated in situ from the precursor compound reacts on the SCR catalytic converter with the nitrogen oxides from the exhaust gas in a comproportionation reaction to form nitrogen and water
Implementation Method 5
the oxidation of soot with NO 2 predominantly produces NO in addition to CO and CO 2
Implementation Method 6
the particle filter is heated to a higher temperature level in order to exceed the soot ignition temperature, which may have been catalytically lowered, and to burn the soot separated in the filter with oxygen to form CO 2
Data Source
Figure 1a~1c
Figure 2~3
Figure 4~5
AI summary
The invention relates to a catalytic converter for purifying the exhaust gases of diesel engines, in particular an oxidation catalytic converter, which is particularly effective for the purification of the exhaust gases of heavy goods vehicles if further exhaust-gas purification units such as for example a particle filter and/or a nitrogen oxide reduction catalytic converter are connected downstream thereof. The catalytic converter contains two catalytically active coatings which differ in terms of their composition and of which only one is in direct contact with the outflowing exhaust gas. The coating (1) which is in direct contact with the outflowing exhaust gas is platinum-rich and, overall, contains more high-grade metal (platinum and palladium) than the coating (2) which is not in direct contact with the outflowing exhaust gas. The platinum-rich coating (1) exhibits a markedly intense oxidation action in particular with regard to NO oxidation, while the coating (2) which is not in direct contact with the outflowing exhaust gas serves to ensure good heat-up performance of the catalytic converter.