Exhaust Gas Catalyst with Porous Separator Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Exhaust gas purifying catalysts face a reduction in purification efficiency due to oxidation and coagulation of noble metal particles at high temperatures, leading to a decrease in surface area and subsequent reduction in the rate of toxic substance removal.
Innovation Solution
A catalyst system with a catalyst layer formed on a substrate, comprising noble metal particles carried by a first compound and separated by a second compound, with fine pores of specific diameters to maintain surface area and prevent coagulation, enhancing gas diffusivity and catalyst performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If noble metal particles are reduced in diameter to increase surface area, then purifying capability is improved, but particles oxidize and coagulate at high temperatures causing surface area to decrease
Solution Approach 1:
The patent introduces a porous coating layer as an intermediary substance between the noble metal particles and the oxidative environment. This coating layer physically separates the noble metal particles from direct contact with oxygen while still allowing reactant gases to diffuse through to reach the catalyst surface, thereby preventing oxidation and coagulation without blocking catalytic activity
Solution Approach 2:
The patent employs a porous coating layer with specifically controlled pore structure (pore diameter and porosity) to allow gas diffusion while providing physical protection. The porous structure enables oxygen and other exhaust gases to penetrate through the coating to reach the noble metal particles, maintaining catalytic function while preventing direct oxidation that would cause particle coagulation
2Productivity
If noble metal particles are dispersed to increase surface area, then catalytic activity is improved, but particles coagulate and fuse at high temperatures reducing effectiveness
Solution Approach 1:
The porous coating layer acts as a stabilizing intermediary matrix that holds noble metal particles in dispersed positions. The coating material forms a physical barrier between adjacent particles, preventing them from migrating and coagulating during high-temperature operation while still allowing catalytic reactions to proceed
Solution Approach 2:
The coating layer is applied to the substrate before the noble metal particles are introduced, creating a pre-formed porous matrix structure. This preliminary action establishes a stable framework that guides particle dispersion and prevents coagulation before thermal stress occurs
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 system maintains high purification efficiency by preventing coagulation of noble metal particles and ensuring sufficient gas diffusivity, thereby improving the removal of toxic substances from exhaust gases.
Implementation Method 1
noble metal particles carried on the surfaces of metal oxide particles to convert toxic components (e.g., unburned hydrocarbon (HC) or carbon monoxide (CO)) contained in an exhaust gas into nontoxic components such as water, carbon dioxide (CO2) and the like through oxidation with the noble metal particles
Implementation Method 2
convert toxic components (e.g., unburned hydrocarbon (HC) or carbon monoxide (CO)) contained in an exhaust gas into nontoxic components such as water, carbon dioxide (CO2) and the like through oxidation with the noble metal particles
Implementation Method 3
The catalyst layer or layers has fine pores with a pore diameter of greater than 0.1 μm and less than or equal to 1 μm and fine pores with a pore diameter of 0.1 μm or less. The pore volume of the fine pores with the pore diameter of greater than 0.1 μm and less than or equal to 1 μm is equal to 10% to 60% of a fine pore volume of the fine pores with the pore diameter of 1.0 μm or less
Data Source
AI summary
Disclosed is an exhaust gas purifying catalyst exhibiting excellent purification performance for a long period of time by suppressing coagulation of a noble metal. A catalyst powder comprises a noble metal and first and second compounds. In the catalyst powder, the first compound carries the noble metal and is separated from another first compound carrying a noble metal by the second compound. At least one catalyst layer comprising the catalyst powder is formed on an inner surface of a substrate. The catalyst layer has fine pores. A fine pore volume of fine pores having a fine pore diameter of greater than 0.1 μm to less than or equal to 1 μm is 10% to 60% of the fine pore volume of fine pores having a pore diameter of 1.0 μm or less.