Integrated DPF-SCR Catalyst Brick for Diesel Exhaust
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Solution Overview
Problem
Existing diesel engine exhaust treatment systems are bulky, costly, and generate high exhaust backpressure due to the use of multiple separate units and large diesel particulate filters with platinum group metal coatings, as well as inefficiencies in NOx conversion and ammonia slip control.
Innovation Solution
A compact diesel engine exhaust treatment system utilizing a diesel particulate filter with integrated SCR catalyst coating permeating the filter walls, an ammonia oxidation catalyst coated at the filter outlet, and a diesel oxidation catalyst positioned upstream or coated on the filter, which performs multiple catalytic functions to reduce NOx, ammonia slip, HC, and CO, minimizing backpressure and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If three separate units (DOC, SCR, DPF) are used in the exhaust treatment system, then emission conversion efficiency is improved, but system size and exhaust backpressure increase
Solution Approach 1:
The patent combines DOC, SCR, and DPF functions into a single integrated catalyst brick where the diesel oxidation catalyst and selective catalytic reduction catalyst are coated on the same porous ceramic substrate that serves as the particulate filter. This merging of multiple separate units into one compact structure reduces system size while maintaining emission conversion efficiency through coordinated catalytic reactions within the integrated device.
Solution Approach 2:
The catalyst brick performs multiple functions simultaneously: it filters particulates through the porous substrate structure, oxidizes CO and HC through the DOC coating, and reduces NOx through the SCR coating using ammonia from urea injection. This multi-functional design eliminates the need for separate dedicated units for each function, achieving space efficiency without compromising emission control performance.
2Reliability
If three separate units (DOC, SCR, DPF) are used in the exhaust treatment system, then emission conversion efficiency is improved, but exhaust backpressure increases
Solution Approach 1:
By merging DOC, SCR, and DPF into a single catalyst brick with integrated coatings on the porous substrate, the patent eliminates the cumulative pressure drops that would occur through multiple separate units. The exhaust gas passes through one consolidated structure rather than sequentially through three separate units, significantly reducing total backpressure while maintaining the catalytic conversion efficiency of all three functions within the integrated device.
3Reliability
If large sized diesel particulate filters with PGM coating are used, then particulate removal efficiency is improved, but production cost increases
Solution Approach 1:
The patent utilizes the porous structure of the ceramic catalyst brick substrate to provide high surface area for catalyst coating within a compact volume. The porous walls offer extensive internal surface area for DOC and SCR catalyst coatings without requiring a large external filter size, thereby maintaining high particulate removal efficiency through the porous structure while reducing the amount of expensive PGM coating material needed compared to large solid-wall filters.
4Reliability
If separate ammonia oxidation catalyst is positioned downstream from DPF, then ammonia slip control is improved, but system complexity and size increase
Solution Approach 1:
The patent integrates the ammonia oxidation catalyst function into the same catalyst brick structure that contains the DOC and SCR coatings. The ammonia oxidation catalyst is positioned within the porous substrate, allowing it to control ammonia slip from the SCR reaction without requiring a separate downstream catalyst unit. This integration simplifies the overall system architecture while maintaining effective ammonia slip control through the combined catalytic functions in the single integrated device.
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 achieves efficient conversion of exhaust components, reduces backpressure, and minimizes costs by using fewer catalyst bricks, maximizing catalyst utilization and allowing for a more compact design while maintaining effective emission control.
Implementation Method 1
Selective catalytic reduction catalysts (SCR) are used to convert NOx to N2 and typically comprise a base metal and utilize an ammonia reductant
Implementation Method 2
ammonia oxidation catalyst, or ammonia slip catalyst, to control ammonia emissions resulting from excess ammonia used in the conversion of NOx
Implementation Method 3
These catalysts promote the conversion of CO and HC emissions to carbon dioxide and water
Implementation Method 4
A diesel particulate filter (DPF) collects soot or particulate matter from engine exhaust
Data Source
AI summary
A diesel engine exhaust treatment system and method is provided which utilizes a diesel particulate filter positioned in the exhaust gas stream of a vehicle which includes an SCR catalyst, an ammonia oxidation catalyst, and/or a diesel oxidation catalyst. The system is capable of performing multiple functions including converting NOx to N2, converting HC and CO to H2O and CO2, trapping particulates, and minimizing ammonia emissions. The system is more compact and efficient than prior systems utilizing separate catalyst units, and minimizes backpressure while maximizing catalyst performance.