Exhaust Catalyst Layer Pore Volume for Phosphorus Poisoning
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Solution Overview
Problem
Existing exhaust gas purification catalysts face challenges in maintaining high Pd catalytic activity during warm-up and high-speed engine operations due to phosphorus poisoning, which impairs the purification performance when Rh catalyst layers are added on the surface, increasing heat capacity and reducing low-temperature activity utilization.
Innovation Solution
A catalyst layer structure with a Pd catalyst layer on the upstream side and a Rh catalyst layer on the surface, optimized with a specific wash coat amount and pore volume proportion, ensures effective phosphorus poisoning suppression and maintains high Pd catalytic activity by controlling the wash coat amount and pore volume in the catalyst layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Rh catalyst layer is provided on the surface of the Pd catalyst layer to suppress phosphorus poisoning, then the Pd catalytic activity is protected, but the heat capacity increases and temperature rise performance is impaired
Solution Approach 1:
The patent applies porous materials by controlling the pore volume proportion of the catalyst layer to be 10% or more. The porous structure reduces the heat capacity of the catalyst layer while maintaining the protective function against phosphorus poisoning. The pores allow for faster heat transfer and temperature rise, resolving the contradiction between protecting Pd catalytic activity and maintaining temperature rise performance.
Solution Approach 2:
The patent changes physical parameters by optimizing the pore volume proportion to 10% or more and controlling the thickness of the Rh catalyst layer. These parameter changes enable the catalyst layer to achieve both phosphorus poisoning suppression and improved temperature rise performance, resolving the technical contradiction between reliability and temperature characteristics.
2Reliability
If the catalyst layer is made multi-layered to protect Pd from phosphorus poisoning, then the purification performance is improved, but the heat capacity increases
Solution Approach 1:
The patent utilizes porous materials with a pore volume proportion of 10% or more to reduce the overall quantity of substance in the catalyst layer. The porous structure provides the necessary catalytic function while minimizing heat capacity, allowing multi-layered protection without excessive heat storage that would impair temperature rise performance.
Solution Approach 2:
The patent applies local quality by strategically placing the Rh catalyst layer and controlling its thickness and distribution. Rather than uniformly thickening the entire catalyst layer, the Rh is concentrated where needed for phosphorus poisoning protection, while maintaining low overall heat capacity through optimized local composition and porosity.
3Reliability
If the Rh catalyst layer is added to protect Pd from phosphorus poisoning, then the catalytic activity is maintained, but the low-temperature activity utilization is reduced
Solution Approach 1:
The patent employs porous materials with optimized pore volume proportion to enhance low-temperature activity utilization. The porous structure facilitates better gas diffusion and contact at lower temperatures, allowing the Rh catalyst layer to effectively protect Pd while maintaining high productivity during warm-up and low-temperature operation.
Solution Approach 2:
The patent optimizes parameters including pore volume proportion (10% or more) and Rh layer thickness to maximize low-temperature activity utilization. These parameter changes ensure that the protective Rh layer does not hinder low-temperature catalytic performance, maintaining high productivity during warm-up operations while protecting Pd from phosphorus poisoning.
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 enhances exhaust gas purification performance during warm-up and high-speed operations without increasing heat capacity, ensuring efficient NOx, HC, and CO purification while maintaining Pd catalytic activity.
Implementation Method 1
a first catalyst layer comprising palladium and a second catalyst layer comprising rhodium and covering the first catalyst layer
Implementation Method 2
a pore volume proportion, which is a proportion of a total volume of the pores existing in the substrate and the catalyst layer in the first section to the volume of the entire first section is 10% or more and less than 20%
Data Source
AI summary
An exhaust gas purification catalyst comprises a substrate and a catalyst layer on the substrate, and has a first section upstream along a flow direction of the exhaust gas and a second section downstream from the first section. The catalyst layer in the first section comprises a first catalyst layer comprising palladium and a second catalyst layer comprising rhodium and covering the first catalyst layer. A pore volume proportion, which is a proportion of a total volume of the pores having a pore diameter of 0.06-30.0 μm as measured by mercury press-in method and existing in the substrate and the catalyst layer in the first section to a volume of a entire first section, is 12-18%. A wash coat amount, which is a mass per unit volume of the catalyst layer in the first section to the volume of the substrate existing in the first section, is 100-190 g/L.