Dual-Pore Catalyst Composition for Exhaust Gas Diffusion
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Solution Overview
Problem
Current multifunctional catalysts for processing exhaust gases from internal combustion engines face challenges in achieving a balance between high surface area and gas diffusion, requiring a composition with both large and small pores to effectively oxidize carbon monoxide, hydrocarbons, and reduce nitrogen oxides.
Innovation Solution
A composition containing zirconium oxide, cerium oxide, and at least one oxide of a rare earth, such as yttrium oxide, with specific porosity characteristics, including two populations of pores centered around 20-40 nm and 80-200 nm diameters, which provides a high pore volume and specific surface area, enhancing thermal stability and gas diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the catalyst has small pores to provide high surface area, then the specific surface area is sufficiently high for catalysis, but the gas diffusion is poor
Solution Approach 1:
The catalyst structure is segmented into two distinct pore populations: small pores (20-40 nm) that provide high surface area for catalytic reactions, and large pores (80-200 nm) that facilitate gas diffusion. This segmentation allows each pore type to fulfill its specific function without compromising the other.
Solution Approach 2:
The invention uses a porous ceramic material with controlled pore structure containing zirconium oxide, cerium oxide, and rare earth oxides. The porous structure is engineered to have dual pore populations, creating a hierarchical pore system that simultaneously achieves high surface area and effective gas transport.
2Productivity
If the catalyst has large pores to improve gas diffusion, then the pore volume is sufficiently high, but the specific surface area is reduced
Solution Approach 1:
The invention transitions from a single-scale pore system to a hierarchical dual-scale pore system, adding another dimension to the pore structure. This hierarchical arrangement in the pore size dimension allows the catalyst to access both high surface area (through small pores) and effective gas diffusion (through large pores) simultaneously.
Solution Approach 2:
The catalyst comprises a composite material system with multiple oxide components (zirconium oxide, cerium oxide, and rare earth oxides) that work together to create and maintain the dual pore population structure, combining the beneficial properties of different materials to achieve both high surface area and good gas diffusion.
3Adaptability or versatility
If the catalyst uses zirconium oxide and cerium oxide for catalytic activity, then the oxidation and reduction functions are achieved, but the thermal stability and porosity balance is difficult to maintain
Solution Approach 1:
The catalyst uses a composite material system combining zirconium oxide, cerium oxide, and rare earth oxides. This composite structure provides thermal stability through the refractory nature of these oxides while maintaining catalytic functionality. The rare earth oxides specifically contribute to thermal stability and help preserve the pore structure at elevated temperatures.
Solution Approach 2:
The invention optimizes the composition parameters (ratios of zirconium oxide, cerium oxide, and rare earth oxides) and processing parameters (calcination temperature and time) to achieve the desired balance between thermal stability and porosity. By controlling these parameters, the catalyst maintains its structural integrity and pore characteristics under thermal conditions.
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 composition achieves a good balance between gas diffusion and surface area, improving oxygen storage and release capacity, and demonstrating enhanced catalytic performance in reducing nitrogen oxides and oxidizing hydrocarbons.
Implementation Method 1
pores of sufficiently large size to allow good diffusion of the gases
Implementation Method 2
these pores which contribute to giving the products a specific surface area that is sufficiently high for them to be usable in catalysis
Data Source
AI summary
A composition is described that includes zirconium oxide, cerium oxide and yttrium oxide, or zirconium oxide, cerium oxide and at least two oxides of two rare earths different from cerium in a mass proportion of at least 20% of zirconium oxide and of at most 70% of cerium oxide, wherein the composition further includes, after calcination at 900° C. for 4 hours, two populations of pores having respective diameters centered, for the first population, about a value of 20 nm to 40 nm and, for the second, about a value of 80 nm to 200 nm. The composition can be used for processing exhaust gases of internal combustion engines.