Ceramic Honeycomb Structure Porous Substrate SCR Catalyst
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Solution Overview
Problem
Conventional ceramic honeycomb structures used as carriers for SCR catalysts face challenges in achieving high nitrogen-oxide-removing efficiency while maintaining low pressure loss and sufficient strength, as increasing the amount of catalytic material leads to larger exhaust-gas-flowing resistance and pressure loss.
Innovation Solution
A ceramic honeycomb structure with a three-dimensional substrate structure optimized by X-ray CT, featuring porosity between 55% and 65%, a high number of substrate branches, and a specific pore diameter distribution, which allows for a larger amount of catalytic material to be carried without increasing pressure loss, enhancing contact efficiency and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of catalytic material is increased to improve nitrogen oxide removal efficiency, then the cleaning efficiency is improved, but the pressure loss increases due to smaller opening areas in exhaust-gas-flowing paths
Solution Approach 1:
The patent applies porous materials by forming pores within the cell walls of the ceramic honeycomb structure. These pores increase the internal surface area available for catalytic material deposition without reducing the external opening area of the exhaust-gas-flowing paths. The porous structure allows catalytic material to be carried in both the cell wall pores and on the inner surfaces, significantly increasing the effective catalytic surface area while maintaining low pressure loss characteristics.
2Quantity of substance
If the cell wall thickness is reduced or cell density is increased to carry more catalytic material per unit volume, then the amount of catalytic material per unit volume is increased, but the pressure loss at the inlet increases due to small opening area
Solution Approach 1:
The patent transitions from a two-dimensional surface-based catalytic material distribution to a three-dimensional porous structure. By creating pores within the cell walls, the catalytic material can be distributed throughout the volume of the cell walls rather than only on the outer surfaces. This dimensional transformation allows significantly more catalytic material to be carried per unit volume while maintaining the same external geometry and opening areas, thus avoiding increased pressure loss.
3Productivity
If the porosity and average pore diameter of cell walls are optimized to increase catalytic material capacity, then the cleaning efficiency and reduced size are improved, but the strength of the ceramic honeycomb structure may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing specific ranges for porosity (50-80%) and average pore diameter (15 μm or more) of the cell walls. These controlled parameter changes allow the structure to achieve high catalytic material capacity while maintaining adequate mechanical strength. The specified parameter ranges represent an optimization balance where sufficient porosity provides high catalytic surface area, while the lower bound constraints ensure structural integrity is maintained.
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 optimized structure effectively increases the amount of catalytic material that can be carried, improving nitrogen oxide removal efficiency and providing a high-strength carrier for SCR catalysts, suitable for diesel and gasoline engines.
Implementation Method 1
by optimizing the porosity and average pore diameter of cell walls of a honeycomb structure as a catalyst carrier
Implementation Method 2
an urea-SCR catalyst, in which urea injected into an exhaust pipe is turned to ammonia, which is reacted with nitrogen oxide in the exhaust gas to remove oxygen therefrom, thereby reducing nitrogen oxide to nitrogen
Data Source
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AI summary
A ceramic honeycomb structure comprising porous cell walls defining large numbers of flow paths, the cell walls having (a) porosity of 55% or more and less than 65%, and (b) 35,000/mm3 or more of substrate branches, wherein the number of substrate branches is defined by the number of branch points (including connecting points of 3 or more branches and connecting points of different-width branches) per a unit volume, in a network structure obtained by the skeletonization of the three-dimensional structure of cell wall substrates determined by X-ray CT.