Segmented Pd-Pt-Rh Catalyst Layer for Cold Start Methane Removal
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Solution Overview
Problem
Existing exhaust gas purification catalysts struggle to effectively remove methane from exhaust gases at cold start conditions of internal combustion engines, particularly in vehicles using natural gas as fuel, due to methane's chemical stability and the catalyst's temperature-dependent activation.
Innovation Solution
The development of an exhaust gas purification catalyst with a substrate divided into cells and a catalyst layer comprising separate layers of palladium (Pd), platinum (Pt), and rhodium (Rh), where the Pd layer is positioned at the inflow end, the Pt layer at the outflow end, and the Rh layer laminated between them, enhancing methane removal performance across varying exhaust gas conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional catalyst layer is used, then the catalyst can be activated at high temperatures, but methane removal performance deteriorates at low temperatures due to methane's chemical stability
Solution Approach 1:
The catalyst layer is segmented into three distinct layers (Pd layer, Pt layer, Rh layer) with different catalytic properties. The Pd layer is positioned at the upstream side to handle low-temperature methane oxidation, the Pt layer at the downstream side for high-temperature performance, and the Rh layer in the middle for NOx reduction, allowing each layer to optimize for specific temperature ranges and污染物 types
Solution Approach 2:
Different regions of the catalyst layer are assigned different material compositions and functions. The upstream region uses Pd which has high activity at low temperatures for methane oxidation, while the downstream region uses Pt which maintains activity at high temperatures, creating local optimization for different thermal conditions along the exhaust flow path
2Device complexity
If the catalyst layer uses a single material, then the structure is simple, but the ability to remove both methane and NOx across varying exhaust conditions deteriorates
Solution Approach 1:
The catalyst layer is designed as a multi-functional system where the Pd layer primarily removes methane and hydrocarbons, the Pt layer handles methane oxidation and CO conversion, and the Rh layer primarily reduces NOx. This multi-functional design allows a single catalyst assembly to address multiple pollutants under varying exhaust conditions without requiring separate catalyst units
Solution Approach 2:
The catalyst layer employs a composite structure combining three different precious metal materials (Pd, Pt, Rh) in distinct layers. Each material contributes its unique catalytic properties, creating a composite catalyst system that leverages the strengths of each individual material to achieve broad-spectrum exhaust gas purification across different temperature and composition conditions
3Loss of energy
If Fuel Cut or Idling Stop control is performed to reduce CO2 emissions, then fuel consumption decreases, but exhaust gas temperature drops making catalyst activation difficult
Solution Approach 1:
The Pd layer is specifically designed to be highly active at low temperatures, enabling it to perform methane oxidation before the exhaust gas temperature rises to levels where conventional catalysts would activate. This preliminary action ensures methane removal occurs even during cold start conditions following Fuel Cut or Idling Stop events, maintaining purification effectiveness when temperature is lowest
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 achieves a high methane removal rate even at low temperatures, effectively reducing methane emissions from internal combustion engines, particularly those using natural gas, while also improving NOx removal performance.
Implementation Method 1
The catalyst layer includes a palladium (Pd) layer, a platinum (Pt) layer, and a rhodium (Rh) layer... purify an exhaust gas discharged from the internal combustion engine
Implementation Method 2
improving NOx removal performance
Data Source
AI summary
An exhaust gas purification catalyst provides excellent removal performance of methane, which is chemically stable. Exhaust gas purification catalyst includes a substrate that divides cells through which an exhaust gas flows and a catalyst layer that is provided on a surface of the substrate. The catalyst layer includes a palladium layer containing palladium that extends from a first end part which is an end part on the side into which an exhaust gas in the cells flows to a second end part which is an end part on the side from which an exhaust gas flows out, a platinum layer containing platinum that extends from the second end part to the first end part, and a rhodium layer containing rhodium that is laminated with both the palladium layer and the platinum layer.