Exhaust Gas Purification Catalyst Pore Volume Control
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Solution Overview
Problem
The pores of approximately 100 nm in existing exhaust gas purification catalysts can become closed during the impregnation or supporting process, leading to degradation of catalyst performance at high space velocity due to inadequate gas diffusion properties.
Innovation Solution
The catalyst's pore volume is controlled by supporting an oxide with cerium (Ce) and/or zirconium with another oxide, maintaining a pore size range of 1 nm to 260 nm and ensuring a total pore volume of at least 0.79 cm^3/g, with a specific increase ratio of the pore volume within the 100 nm to 260 nm range to enhance gas diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst is impregnated with OSC material or supported with La oxide, then the oxygen storage capacity is improved, but the pores of approximately 100 nm become closed, leading to degraded gas diffusion property
Solution Approach 1:
The invention employs a porous silica support with specifically controlled pore size distribution, where the mode pore diameter is 3 nm to 100 nm. This porous structure maintains adequate pore volume (0.79 cm³/g or more) while supporting the catalyst components, ensuring both oxygen storage capacity and gas diffusion properties are preserved simultaneously.
Solution Approach 2:
The invention changes the physical parameters of the support structure by controlling the pore size distribution (mode diameter 3-100 nm) and pore volume (0.79 cm³/g or more). By optimizing these parameters, the catalyst achieves both adequate oxygen storage capacity and good gas diffusion properties, resolving the contradiction between these two features.
2Ease of operation
If the pore volume is increased to maintain gas diffusion, then the catalyst structure becomes less dense, but the mechanical strength and stability may be compromised
Solution Approach 1:
The invention uses a porous silica support with optimized pore structure (mode diameter 3-100 nm, pore volume ≥0.79 cm³/g) that maintains both gas diffusion properties and mechanical strength. The specific pore size distribution ensures adequate gas diffusion while the overall structural integrity is preserved through the silica framework.
Solution Approach 2:
The invention creates a composite catalyst system combining porous silica support with perovskite-type composite metal oxide particles. This composite structure allows the silica component to provide mechanical strength and stable pore structure, while the metal oxide component provides catalytic activity, achieving both gas diffusion and mechanical strength requirements.
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 approach maintains and improves the catalyst's intrinsic performance, particularly at high space velocity, by ensuring effective gas diffusion and retention of hydrocarbon oxidation performance.
Implementation Method 1
pores of approximately 100 nm of the above-described La oxide, which affects the gas diffusion property
Implementation Method 2
an oxide having an oxygen storage and release capacity
Data Source
Figure 1
Figure 2
AI summary
An exhaust gas purification catalyst contains an oxide 1 and an oxide 2. The catalyst has pores P1-260 with a pore size of from 1 nm to 260 nm, that can be measured by the nitrogen absorption method, and the total sum ∑PV1-260 of the pore volume PV1-260 of the pores is equal to or greater than 0.79 cm3/g. The oxide 1 is an oxide with an oxygen release capability. The oxide 2 is represented by LaxM1-xM'O3-δ (2), where M is at least one element selected from the group consisting of Ba, Sr and Ca, M' is at least one element selected from the group consisting of Fe, Co, Ni and Mn, δ is the amount of oxygen deficiency, x satisfies 0 ≦ x ≦ 1, and δ satisfies 0 ≦ δ ≦ 1.