Binary Catalyst Selective Catalytic Reduction Filter
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Solution Overview
Problem
Conventional diesel particulate filters with selective catalytic reduction capabilities are not suitable for heavy-duty diesel truck applications due to high pressure drop, reduced fuel economy, increased soot lightoff temperature, and frequent active regenerations, as they struggle to balance soot filtration, oxidation, and NOx reduction efficiently.
Innovation Solution
A catalytic core with a binary catalyst composition is used in a wall-flow filter, featuring a first catalyst for in-situ nitrogen dioxide production without significant ammonia oxidation and a second catalyst for NOx reduction, allowing both soot oxidation and NOx reduction to occur within the same filter, reducing the need for a separate selective catalytic reduction unit and minimizing platinum group metal usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional selective catalytic reduction filter is used to combine soot filtration and NOx reduction in a single unit, then the device complexity is reduced, but the pressure drop increases and fuel economy deteriorates
Solution Approach 1:
The filter wall is segmented into multiple layers with distinct catalyst distributions: a first catalyst layer optimized for soot oxidation and a second catalyst layer optimized for NOx reduction. This segmentation allows each layer to perform its specific function efficiently, reducing overall pressure drop while maintaining combined functionality.
Solution Approach 2:
Different regions of the filter have different catalyst compositions and loadings. The inlet portion has higher soot oxidation catalyst loading to handle fresh soot, while the outlet portion has higher NOx reduction catalyst loading. This local optimization reduces the overall catalyst loading required, decreasing pressure drop and improving fuel economy.
2Device complexity
If a conventional selective catalytic reduction filter is used to combine soot oxidation and NOx reduction, then the device complexity is reduced, but the soot lightoff temperature increases
Solution Approach 1:
The catalyst system is segmented into a first catalyst (e.g., Pt, Pd, or Rh) specialized for soot oxidation and a second catalyst (e.g., Cu-zeolite or Fe-zeolite) specialized for NOx reduction. The first catalyst is positioned and dosed to ensure soot oxidation occurs at lower temperatures, preventing soot accumulation before it can increase pressure drop.
Solution Approach 2:
The patent modifies catalyst parameters including composition, loading, and distribution to optimize lightoff temperature. By using a first catalyst with high soot oxidation activity and positioning it in the inlet portion, the system achieves lower soot lightoff temperature despite the presence of the second NOx reduction catalyst.
3Device complexity
If a conventional selective catalytic reduction filter is used, then the device complexity is reduced, but active regenerations become more frequent
Solution Approach 1:
The filter incorporates a first catalyst layer optimized for soot oxidation that is distributed to ensure continuous soot combustion. This segmentation prevents soot accumulation that would otherwise require frequent active regenerations, while the second catalyst layer handles NOx reduction without interfering with soot oxidation.
Solution Approach 2:
The first catalyst is dosed and distributed to maintain continuous soot oxidation activity throughout the filter. This continuous action ensures soot is converted to CO2 as it deposits, preventing the buildup that would trigger active regeneration events, thereby improving productivity by reducing regeneration frequency.
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
This solution achieves efficient soot filtration, oxidation, and NOx reduction with lower pressure drop, reduced fuel consumption, and lower soot lightoff temperatures, enhancing the overall performance and reducing the frequency of active regenerations in heavy-duty diesel applications.
Implementation Method 1
a first catalyst for in-situ nitrogen dioxide production without significant ammonia oxidation
Implementation Method 2
a second catalyst for NOx reduction
Implementation Method 3
the walls comprise pores creating passages extending across a width of the walls from the inlet channels to the outlet channels
Implementation Method 4
passages extending across a width of the walls from the inlet channels to the outlet channels
Implementation Method 5
the filter 108 can undergo regeneration to convert the soot into carbon dioxide through chemical oxidation with an oxidant species
Data Source
AI summary
Catalytic cores for a wall-flow filter include juxtaposed channels extending longitudinally between an inlet side and an outlet side of the core, wherein the inlet channels are plugged at the outlet side and outlet channels are plugged at the inlet side. Longitudinal walls forming the inlet and outlet channels separate the inlet channels from the outlet channels. The walls include pores that create passages extending across a width of the walls from the inlet channels to the outlet channels. Catalysts are distributed across the width and length of the walls within internal surfaces of the pores in a manner such that the loading of each catalyst across the width varies by less than 50% from an average loading across the width.