Exhaust Gas Purification Catalyst with High-Aspect-Ratio Pores
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Solution Overview
Problem
Exhaust gas purification catalysts with noble metals like Pt and Rh face reduced activity due to solid solution formation, leading to decreased purification efficiency, especially under high intake air mass conditions, and existing methods to enhance gas diffusivity are insufficient.
Innovation Solution
A catalyst coating layer with a high-aspect-ratio pore structure is created using an organic fiber as a pore-forming material, differing in composition between upstream and downstream regions, to enhance gas diffusivity and purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a void is provided in a catalyst coating layer to enhance gas diffusivity, then gas diffusivity is improved, but the thickness of the catalyst layer is increased leading to increased pressure loss
Solution Approach 1:
The patent introduces a porous structure with voids in the catalyst coating layer to enhance gas diffusivity. The voids create additional pathways for gas transport through the coating, reducing diffusion resistance without requiring a thicker catalyst layer, thereby avoiding increased pressure loss.
Solution Approach 2:
The patent uses a composite structure combining catalyst particles with pore-forming materials (such as organic fibers or inorganic particles) to create a multi-phase coating layer. This composite approach allows the formation of interconnected voids that improve gas diffusivity while maintaining a thin overall coating thickness to minimize pressure loss.
2Speed
If a void is provided in a catalyst coating layer, then gas diffusivity is enhanced, but the strength of the catalyst layer is decreased
Solution Approach 1:
The patent employs porous materials with controlled void structures that provide gas diffusion pathways while maintaining mechanical integrity. The porous framework is designed to preserve the structural strength of the catalyst layer by using materials and configurations that prevent excessive weakening.
Solution Approach 2:
The patent applies void formation locally within specific regions of the catalyst coating layer rather than uniformly throughout. This localized approach creates gas diffusion channels where needed while preserving the structural integrity and strength of other regions of the coating layer.
3Stability of the object's composition
If the composition of the downstream region is different from the upstream region in a zone catalyst, then noble metal solid solution formation is reduced, but purification efficiency is lowered under high intake air mass conditions
Solution Approach 1:
The patent creates a zone catalyst with spatially varying composition, where the upstream region contains one noble metal and the downstream region contains another noble metal. This local differentiation prevents solid solution formation and maintains composition stability while addressing the purification efficiency issue through structural modification.
Solution Approach 2:
The patent introduces a porous structure with voids in the downstream region of the zone catalyst to enhance gas diffusivity. This compensates for the reduced purification efficiency caused by the compositional differentiation, ensuring that exhaust gas can efficiently reach the catalyst sites even under high intake air mass conditions.
4Productivity
If the thickness of the catalyst layer is increased to ensure conversion efficiency, then purification performance is improved, but pressure loss is increased
Solution Approach 1:
The patent introduces a porous structure with controlled voids in the catalyst coating layer to enhance gas diffusivity. This allows the gas to penetrate deeper into the catalyst layer more efficiently, improving conversion efficiency without requiring an increased catalyst layer thickness, thereby avoiding excessive pressure loss.
Solution Approach 2:
The patent uses a composite structure combining catalyst particles with pore-forming materials to create a multi-phase coating layer. This composite approach improves mass transfer efficiency within the catalyst layer, enabling effective purification performance with a thinner overall coating to minimize pressure loss.
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 catalyst exhibits improved gas diffusivity and purification performance even under high intake air mass conditions, maintaining efficiency and reducing pressure loss.
Implementation Method 1
a catalyst coating layer formed on the substrate, wherein the catalyst coating layer comprises catalyst particles, the catalyst coating layer having an upstream region extending by 40 to 60% of the entire length of the substrate from an upstream end of the catalyst in an exhaust gas flow direction and a downstream region corresponding to the remainder portion of the catalyst coating layer
Implementation Method 2
a catalyst coating layer formed thereon by wash coating of a slurry including a noble metal particle having catalyst activity and an auxiliary catalyst having oxygen storage capacity
Implementation Method 3
an auxiliary catalyst having oxygen storage capacity (OSC)
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3
AI summary
An object of the present invention is to provide an exhaust gas purification catalyst which can exhibit sufficient purification performance even under a high Ga condition. The present invention relates to an exhaust gas purification catalyst comprising a substrate and a catalyst coating layer formed on the substrate, wherein the catalyst coating layer comprises catalyst particles, the catalyst coating layer having an upstream region extending by 40 to 60% of the entire length of the substrate from an upstream end of the catalyst in the direction of an exhaust gas flow and a downstream region corresponding to the remainder portion of the catalyst coating layer, the composition of the catalyst particle of the upstream region being different from that of the downstream region. The downstream region in the direction of an exhaust gas flow has a structure where a void is included in a large number, and furthermore high-aspect-ratio pores having an aspect ratio of 5 or more account for a certain percentage or more of the whole volume of voids. Thus, the exhaust gas purification catalyst exhibits enhanced purification performance.