Exhaust Gas Purification Device With Pore Connectivity Control
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Solution Overview
Problem
Current exhaust gas purification devices face challenges in further reducing nitrogen oxide (NOx) and total hydrocarbon (THC) emission amounts, despite the use of noble metals like platinum, palladium, and rhodium as catalysts.
Innovation Solution
The exhaust gas purification device incorporates multiple catalyst layers with specific pore connectivity and structure, including a first catalyst layer for oxidizing HC and a second catalyst layer with high pore connectivity for reducing NOx and THC emissions, optimized by controlling the pore connectivity and thickness of the catalyst layers to enhance gas diffusibility and catalyst activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst layer is made thicker to increase catalyst activity, then the purification performance improves, but the gas diffusibility deteriorates
Solution Approach 1:
The patent applies porous materials by forming a catalyst layer with controlled pore structure (porosity of 30-70% and specific pore size distribution) to enable efficient gas diffusion while maintaining high catalyst activity. The porous structure allows exhaust gas to penetrate deep into the catalyst layer, increasing contact with catalyst particles without requiring excessive thickness.
Solution Approach 2:
The patent applies local quality by creating a non-uniform pore size distribution within the catalyst layer, with larger pores (0.5-5 μm) in the inner region for gas penetration and smaller pores (0.1-1 μm) in the outer region for enhanced catalytic reaction. This spatial variation in pore quality optimizes both diffusion and reaction efficiency throughout the layer thickness.
2Reliability
If noble metals are used as catalysts to reduce harmful emissions, then the purification effectiveness improves, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the pore size distribution and porosity parameters of the catalyst layer to enhance the effectiveness of noble metal catalysts. By controlling pore sizes (0.1-5 μm) and porosity (30-70%), the patent maximizes catalyst activity and gas-catalyst contact efficiency, thereby reducing harmful emissions with improved purification effectiveness.
3Productivity
If the pore connectivity is increased to improve gas diffusibility, then the gas passage efficiency improves, but the catalyst activity decreases
Solution Approach 1:
The patent applies local quality by creating distinct pore size zones: larger pores (0.5-5 μm) in the inner region for efficient gas penetration and smaller pores (0.1-1 μm) in the outer region for enhanced catalytic interaction. This spatial differentiation maintains high gas passage efficiency while preserving catalyst activity through optimized local pore structures.
Solution Approach 2:
The patent applies porous materials with controlled porosity (30-70%) and specific pore size distribution to achieve both high gas diffusibility and catalyst activity. The porous structure facilitates gas penetration while the controlled pore dimensions ensure adequate catalyst-c gas contact for effective purification.
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 significantly reduces NOx and THC emission amounts by improving gas diffusibility and catalyst activity, with the second catalyst layer's high pore connectivity allowing efficient exhaust gas passage and increased contact with catalyst particles, leading to enhanced purification performance.
Implementation Method 1
the second catalyst layer is provided with pores, and wherein a pore connectivity of the second catalyst layer expressed by formula (1) below is 5% to 35%
Implementation Method 2
a first catalyst layer containing first catalyst particles, the first catalyst layer lying on the substrate across a first region
Data Source
AI summary
The exhaust gas purification device includes a substrate, a first catalyst layer, and a second catalyst layer. The substrate includes an upstream end and a downstream end. The first catalyst layer contains first catalyst particles and lies on the substrate across a first region extending between the upstream end and a first position. The first position is at a first distance from the upstream end toward the downstream end. The second catalyst layer contains second catalyst particles and lies on the first catalyst layer across the first region. The second catalyst layer is provided with pores. Pore connectivity of the second catalyst layer is 5% to 35%. A mean value of areas of the pores of the second catalyst layer in a cross-sectional backscattered electron image of the second catalyst layer may be 0.7 μm2 to 9.0 μm2.