Dual-Coated Catalytic Filter for Diesel Exhaust NOx Management
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Solution Overview
Problem
Conventional exhaust gas cleaning systems for diesel engines face challenges in maintaining an optimal NO/NO2 ratio for effective denitrification due to high oxygen content and colder exhaust gas temperatures, leading to incomplete reduction of nitrogen oxides and ammonia breakthroughs, especially with smaller oxidation catalytic converters and reduced conversion efficiency of hydrocarbons and carbon monoxide.
Innovation Solution
A catalytically active particle filter with a wall-flow filter substrate and dual catalytic coatings, where the first coating contains platinum and palladium for oxidizing hydrocarbons and carbon monoxide, and the second coating with a higher platinum content for converting nitrogen monoxide to nitrogen dioxide, ensuring an optimal NO2/NOx ratio for downstream SCR catalytic converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the oxidation catalytic converter is reduced in size to compensate for colder exhaust gas temperatures, then the structural volume available for the converter is smaller, but the conversion efficiency of hydrocarbons and carbon monoxide deteriorates and the optimal NO2/NOx ratio cannot be maintained
Solution Approach 1:
The catalytic converter is divided into two distinct catalytic zones: a first catalytic coating containing platinum and palladium for oxidizing hydrocarbons and carbon monoxide, and a second catalytic coating with higher platinum content for converting nitrogen monoxide to nitrogen dioxide. This segmentation allows each zone to perform its specific function efficiently even in a compact converter design.
Solution Approach 2:
Different regions of the catalytic converter are given different catalytic properties through the two distinct coatings. The first coating region optimizes for hydrocarbon and carbon monoxide oxidation, while the second coating region optimizes for nitrogen monoxide conversion, ensuring optimal performance for each chemical transformation within the limited volume.
2Device complexity
If a conventional single-coating particle filter is used, then the device complexity is lower, but the ability to simultaneously optimize hydrocarbon oxidation and nitrogen dioxide formation deteriorates
Solution Approach 1:
The catalytic coating is segmented into two distinct layers with different compositions and functions. The first coating contains platinum and palladium for hydrocarbon oxidation, while the second coating has higher platinum content for nitrogen monoxide conversion to nitrogen dioxide, enabling simultaneous optimization of both reactions.
Solution Approach 2:
The catalytic converter uses composite catalytic coatings combining different precious metal compositions in specific sequences. The first coating combines platinum and palladium, while the second coating uses higher platinum content, creating a composite structure that performs multiple catalytic functions simultaneously.
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-coated particle filter significantly enhances the conversion of harmful gases, achieving a higher NO2 formation and improved NOx reduction, ensuring compliance with future emissions standards by optimizing the NO2/NOx ratio and reducing residual emissions of carbon monoxide, hydrocarbons, and nitrogen oxides.
Implementation Method 1
a first catalytically active coating (1) containing platinum and palladium and being in the porous walls (7) between the inflow and outflow channels, and the second catalytically active coating (2) containing palladium and platinum and being in the outflow channels located on the porous walls (7) between the inflow and outflow channels
Implementation Method 2
the second catalytically active coating (2) containing palladium and platinum and being in the outflow channels located on the porous walls (7) between the inflow and outflow channels
Implementation Method 3
a wall-flow filter substrate (3), which comprises inflow and outflow channels separated by porous walls (7)
Data Source
Figure 1
AI summary
A catalytically active particulate filter suitable for use in an exhaust gas purification system for diesel engines is presented. The particulate filter removes diesel soot particles from the exhaust gas and is also effective in oxidizing carbon monoxide and hydrocarbons and in converting at least a portion of nitrogen monoxide to nitrogen dioxide. The particulate filter comprises a filter body (3) and two catalytically active coatings (1) and (2) containing platinum and palladium, platinum, or platinum and palladium, respectively, wherein the platinum content of the second catalytically active coating (2) is higher than the platinum content of the first catalytically active coating (1).