Catalyzed Particulate Filter with Internal Support for Exhaust Purification
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Solution Overview
Problem
Existing exhaust gas purification systems, particularly lean NOx trap (LNT) catalysts and catalyzed particulate filters (CPF), face inefficiencies at high temperature or high load conditions, leading to increased nitrogen oxide emissions and reduced catalytic performance due to insufficient catalyst coating and increased back pressure.
Innovation Solution
The apparatus includes a lean NOx trap device coated with LNT catalysts and a catalyzed particulate filter with additional catalyst coating on supports within the CPF, utilizing ceria, platinum, and barium, and optionally an SCR device downstream to enhance nitrogen oxide removal and minimize back pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thick catalyst coating is applied on the porous wall in CPF, then the catalytic reaction efficiency is improved, but the back pressure increases due to blocked micropores
Solution Approach 1:
The invention introduces a support structure (honeycomb monolith) as a third dimension within the exhaust flow path. The catalyst is coated on this support rather than directly on the porous wall, creating a layered architecture where the support provides the primary catalytic surface area while the porous wall maintains its filtering function with open micropores, thus resolving the conflict between catalytic efficiency and back pressure
Solution Approach 2:
The support structure with catalyst coating is nested within the exhaust channels of the CPF. The support fits inside the channels formed by the porous wall structure, creating a nested configuration where the inner support handles catalysis while the outer porous wall structure maintains structural integrity and filtering capability without blocking micropores
2Productivity
If the cell density of inlet and outlet channels is increased to increase catalyst coating surface area, then the catalytic function is enhanced, but the wall thickness is reduced which deteriorates filter performance
Solution Approach 1:
Instead of increasing cell density in the planar dimension, the invention adds a third dimension by introducing a support structure that extends through the channel length. This allows catalyst coating surface area to increase volumetrically rather than areally, enabling sufficient catalytic function without requiring higher cell density that would reduce wall thickness
Solution Approach 2:
The catalytic function is segmented between two components: the porous wall structure that provides structural support and filtering, and the separate support with catalyst coating that provides the catalytic surface. This segmentation allows each component to be optimized independently - the porous wall can maintain adequate thickness for filtering while the support provides the necessary catalyst surface area
3Productivity
If the LNT catalyst is disposed closely to the engine, then the nitrogen oxide absorption is improved under normal conditions, but the purification performance deteriorates at high temperature or high load conditions
Solution Approach 1:
The invention creates a composite exhaust treatment system combining LNT catalyst and SCR catalyst in a single CPF structure. The LNT portion handles nitrogen oxide absorption under normal conditions, while the SCR portion activates at higher temperatures to reduce nitrogen oxide through chemical reduction, providing reliable performance across the full temperature and load range
Solution Approach 2:
The system utilizes temperature as a parameter change to switch between different catalytic mechanisms. At lower temperatures, the LNT catalyst absorbs nitrogen oxide effectively. As temperature increases under high load conditions, the SCR catalyst becomes active and chemically reduces nitrogen oxide, maintaining purification performance across varying thermal conditions
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 configuration improves nitrogen oxide purification efficiency, enhances catalytic function, and maintains filtering efficiency while meeting stringent exhaust gas regulations by optimizing catalyst distribution and loading within the CPF.
Implementation Method 1
The LNT catalyst absorbs the NOx contained in the exhaust gas when the air/fuel ratio is lean
Implementation Method 2
the catalyst is coated on the porous wall that separates the inlet channel and the outlet channel from each other, and the fluid passes through the porous wall and comes into contact with the catalyst coating
Implementation Method 3
the NOx contained in the exhaust gas is reduced in the DeNOx catalyst through oxidation-reduction reaction with the reducing agents
Data Source
AI summary
An apparatus includes a catalytic converter on an exhaust pipe and provided with a lean NOx trap (LNT) device coated with an LNT catalyst, and a catalyzed particulate filter (CPF) coated with a catalyst. The LNT device and CPF are sequentially disposed in the catalytic converter. The CPF includes at least one inlet channel, extending in a longitudinal direction, having a first end into which fluid flows and a blocked second end; at least one outlet channel, extending in the longitudinal direction, having a blocked first end and a second end through which the fluid flows out; at least one porous wall defining a boundary between neighboring inlet and outlet channels and that extends in the longitudinal direction; and a support coated with the catalyst and located within at least one among the at least one inlet channel and the at least one outlet channel.