Wall-Flow Catalyst Layer Positioning for Lower Exhaust Pressure Loss
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Solution Overview
Problem
Existing methods for producing exhaust gas purifying catalysts do not adequately address the biasing of catalyst layers towards the inflow-side or outflow-side cells in the thickness direction of a partition wall, leading to increased pressure loss and reduced exhaust gas purifying performance.
Innovation Solution
A method involving a drying step where gas is introduced from the exhaust gas inflow-side or outflow-side ends, or alternately from both ends, to bias the catalyst slurry location towards the respective cells, forming a catalyst layer that is unevenly distributed in the thickness direction of the partition wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst layer is provided in a particulate filter with narrow exhaust gas passage, then exhaust gas purifying performance is improved, but pressure loss increases and engine output decreases
Solution Approach 1:
The catalyst layer is selectively formed only in the inlet-side cell partition walls rather than uniformly across all partition walls. This local quality approach concentrates the purifying function where it is most needed (at the inlet side where exhaust gas first enters) while leaving other areas without catalyst coating, thereby reducing overall pressure loss while maintaining effective purification performance.
2Reliability
If the exhaust gas passage is narrowed to improve purifying performance, then harmful component removal is enhanced, but pressure loss increases
Solution Approach 1:
The catalyst layer is selectively applied to partition walls in the inlet-side cell, creating a localized purification zone. This allows harmful components to be effectively removed at the point of entry without requiring a uniformly narrow exhaust passage throughout, thereby reducing the overall pressure loss impact while maintaining effective harmful component removal.
3Reliability
If catalyst layers are extensively formed over the entire partition wall, then purifying performance is maximized, but pressure loss increases
Solution Approach 1:
Instead of extensively forming catalyst layers over the entire partition wall, the invention selectively forms catalyst layers only in the inlet-side cell partition walls. This local quality approach maintains effective purifying performance by concentrating catalytic activity where exhaust gas first contacts the filter structure, while reducing the total catalyst coverage to minimize pressure loss.
Solution Approach 2:
The partition walls are segmented into inlet-side cells and outlet-side cells, with catalyst layers formed only in the inlet-side cell partition walls. This segmentation allows the purifying function to be concentrated in specific segments (inlet-side) while other segments (outlet-side) remain without catalyst coating, optimizing the balance between purification performance and 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
This method enables the production of an exhaust gas purifying catalyst with improved performance by reducing pressure loss and enhancing the catalyst layer's effectiveness in purifying exhaust gases, applicable to both gasoline and diesel particulate filters.
Implementation Method 1
a drying step of introducing gas into the wall flow type substrate to dry the coated catalyst slurry
Implementation Method 2
a wall flow type substrate in which an inflow-side cell having an open exhaust gas inflow-side end, and an outflow-side cell adjacent to the inflow-side cell and having an open exhaust gas outflow-side end are separated by a porous partition wall
Data Source
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AI summary
A method for producing an exhaust gas purifying catalyst for purifying exhaust gas discharged from an internal combustion engine, the method includes: a step of preparing a wall flow type substrate in which an inflow-side cell having an open exhaust gas inflow-side end, and an outflow-side cell adjacent to the inflow-side cell and having an open exhaust gas outflow-side end are separated by a porous partition wall; a coating step of coating a catalyst slurry containing a catalytic metal on the partition wall; a drying step of introducing gas into the wall flow type substrate to dry the coated catalyst slurry; and a firing step of firing the dried catalyst slurry to form a catalyst layer. By introducing the gas from the exhaust gas inflow-side end or the exhaust gas outflow-side end, or alternately from both the exhaust gas inflow-side end and the exhaust gas outflow-side end in the drying step, the dried catalyst slurry is biasedly located toward a side of the inflow-side cell or the outflow-side cell into which the gas has been introduced, in a thickness direction of the partition wall.