DPF Catalyst Coating for NOx Purification
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Solution Overview
Problem
Current exhaust systems for diesel engines face challenges in efficiently purifying nitrogen oxides at high temperatures and loads, as nitrogen oxide storage catalysts (LNT) have low purification efficiency and increase back pressure when enhanced for particulate matter filtration.
Innovation Solution
An exhaust system incorporating a diesel particulate filter (DPF) with additional support and catalyst coating, combining the functions of LNT and selective catalytic reduction (SCR) catalysts, optimized with ion substituent zeolite catalysts and specific platinum amounts, to enhance nitrogen oxide purification and maintain particulate matter filtering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the LNT catalyst is enhanced with more catalyst coating to improve nitrogen oxide purification efficiency, then nitrogen oxide purification rate is improved, but back pressure increases and particulate matter filtering efficiency deteriorates
Solution Approach 1:
The DPF channels are divided into multiple sections with different catalyst coating densities. The first channel has higher catalyst coating for NOx purification, while the second channel has lower catalyst coating to maintain airflow and reduce back pressure. This segmentation allows different regions to perform different functions optimally.
Solution Approach 2:
Different catalyst coating amounts are applied to different locations within the DPF. The first channel receives enhanced catalyst coating in specific regions to maximize NOx purification, while the second channel maintains lighter coating to preserve channel permeability and minimize back pressure effects.
2Productivity
If the catalyst coating amount is increased to improve nitrogen oxide purification, then purification performance is improved, but the DPF channels become more restricted and back pressure increases
Solution Approach 1:
The DPF is segmented into multiple channels with differentiated catalyst loading. This allows the system to distribute the purification function across multiple pathways rather than over-loading a single channel, maintaining overall flow capacity while achieving high purification efficiency.
Solution Approach 2:
The first channel receives excessive catalyst coating relative to the second channel, creating a deliberate imbalance. This partial excessive action in the first channel ensures high NOx purification capacity there, while the second channel's lighter coating prevents excessive restriction and maintains system-level airflow.
3Productivity
If SCR catalyst is added to the DPF to improve nitrogen oxide purification, then NOx purification rate is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The SCR catalyst is merged with the LNT catalyst within the same DPF structure, creating a combined catalyst system. This merging allows the DPF to perform both particulate filtration and nitrogen oxide purification functions simultaneously, improving overall productivity without requiring a completely separate SCR system.
Solution Approach 2:
The DPF is designed with multi-functionality, serving both as a particulate matter filter and as a nitrogen oxide purification device. By incorporating both LNT and SCR catalysts, the single DPF component achieves multiple functions that would traditionally require separate systems, thereby improving productivity while managing complexity through integration.
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 system improves nitrogen oxide purification rates and maintains particulate matter filtering efficiency by increasing catalyst contact time and response, while minimizing back pressure and preventing catalyst degradation during regeneration.
Implementation Method 1
at least one catalyst is coated on one of the inner wall of the inflow channel, the inner wall of the outflow channel, and the support
Implementation Method 2
nitrogen oxide storage catalyst (LNT catalytic) device
Implementation Method 3
a support disposed inside of at least one of the inflow channel and the outflow channel, and at least one catalyst is coated on one of the inner wall of the inflow channel, the inner wall of the outflow channel, and the support
Implementation Method 4
the DPF filters and burns particulate matter (PM)
Implementation Method 5
The SCR catalyst may be ion substituent zeolite catalyst, especially Cu-CHA catalyst
Implementation Method 6
control method of nitrogen oxide desorption
Data Source
AI summary
An exhaust system may include first purification device disposed at a rear end portion of exhaust manifold and including Lean NOx Trap (LNT); second purification device disposed at rear end portion of the first purification device and including a diesel particulate filter (DPF); and a third purification device disposed at a rear end portion of the second purification device and including a selective catalytic reduction (SCR), wherein the DPF of the second purification device includes at least one inflow channel, at least one outflow channel, at least one wall disposed between the inflow channel and the outflow channel and extended in a longitudinal direction, and a support disposed inside of at least one of the inflow channel and the outflow channel, and at least one catalyst is coated on one of the inner wall of the inflow channel, the inner wall of the outflow channel, and the support.