Wall-flow Catalyst Layer Segmentation for Exhaust Purification
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Solution Overview
Problem
Conventional exhaust gas purification catalysts face challenges in maintaining high purification performance at low temperatures and suffer from pressure loss due to sintering of noble metals and inefficient catalyst distribution within particulate filters.
Innovation Solution
A wall-flow type exhaust gas purification device with an upstream catalyst layer containing Pd and/or Pt and a downstream catalyst layer containing Rh, both supported on carriers and disposed inside the partition wall, to prevent sintering and reduce pressure loss while enhancing purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Pt and Rh are supported in the same manner from inlet to outlet side inside the partition wall, then the catalyst structure is simple, but sintering of Pt and Rh occurs at high temperature causing purification performance to drop
Solution Approach 1:
The catalyst is divided into two distinct layers: an upstream catalyst layer containing Pt and/or Pd, and a downstream catalyst layer containing Rh. This segmentation prevents sintering between Pt/Rh by spatially separating them, while maintaining catalytic functionality through coordinated action of the separated layers
Solution Approach 2:
Different noble metals are localized in different regions of the partition wall thickness. The upstream catalyst layer with Pt/Pd is positioned in the upstream portion, while the downstream catalyst layer with Rh is positioned in the downstream portion, creating local quality differences that prevent sintering while optimizing purification performance at various stages of exhaust gas flow
2Reliability
If Rh layer is disposed outside the partition wall to prevent sintering, then sintering between Pd and Rh is suppressed, but pressure loss increases due to restricted exhaust gas flow
Solution Approach 1:
Both the upstream catalyst layer and downstream catalyst layer are nested inside the partition wall structure. This nesting arrangement prevents sintering through spatial separation while maintaining smooth exhaust gas flow paths, avoiding the pressure loss that would result from external catalyst layer placement
3Device complexity
If conventional catalyst configuration is used, then the structure is simple, but purification performance at low temperature is insufficient especially for HC removal
Solution Approach 1:
The upstream catalyst layer is specifically designed to contain Pt and/or Pd, which have superior low-temperature catalytic activity for HC oxidation. This local quality assignment ensures effective HC purification during cold start conditions, while the downstream Rh layer handles other exhaust components
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 configuration significantly enhances purification performance, particularly at low temperatures, while minimizing pressure loss by effectively supporting noble metals inside the partition wall, preventing sintering, and optimizing catalyst distribution.
Implementation Method 1
an upstream catalyst layer which is disposed in an upstream portion of the substrate in the direction of exhaust gas flow, the upstream portion including the exhaust gas inflow end section
Implementation Method 2
exhaust gas at low temperature contains a large amount of HC being unburned substances of fuel
Implementation Method 3
a downstream catalyst layer which is disposed in a downstream portion of the substrate in the direction of exhaust gas flow, the downstream portion including the exhaust gas outflow end section. The downstream catalyst layer contains a carrier, and Rh supported on the carrier
Implementation Method 4
regulations on harmful components in exhaust gas such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx)
Implementation Method 5
a substrate of wall-flow structure having an inlet cell in which only an exhaust gas inflow end section is open, an outlet cell which is adjacent to the inlet cell and in which only an exhaust gas outflow end section is open, and a porous partition wall that partitions the inlet cell and the outlet cell from each other. As the exhaust gas passes through the porous cell partition wall, the particulate matter becomes trapped within the pores inside the partition wall
Implementation Method 6
The upstream catalyst layer contains a carrier, and Pd and/or Pt supported on the carrier. The downstream catalyst layer contains a carrier, and Rh supported on the carrier
Data Source
AI summary
An exhaust gas purification device includes: a substrate of wall-flow structure having an inlet cell, an outlet cell and a porous partition wall; an upstream catalyst layer provided inside the partition wall and disposed in an upstream portion, including an exhaust gas inflow end section, of the substrate; and a downstream catalyst layer provided inside the partition wall and disposed in a downstream portion, including an exhaust gas outflow end section, of the substrate. The downstream catalyst layer contains a carrier, and Rh supported on the carrier. The upstream catalyst layer contains a carrier, and Pd and/or Pt supported on the carrier.