Biased Catalyst Layer for Exhaust Gas Purification
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Solution Overview
Problem
Existing exhaust gas purifying systems face challenges in maintaining effective purifying performance while preventing increased pressure loss due to ash deposition, particularly when catalyst layers are uniformly distributed across partition walls in internal combustion engines.
Innovation Solution
A catalyst layer containing at least two different catalyst metals is biasedly located toward the exhaust gas discharge side in the partition wall, with a higher mass distribution near the outflow-side cell to reduce pressure loss and enhance purifying performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Pt-Rh alloy catalyst is used to reduce CO and HC emissions, then the catalytic activity is improved, but the production cost increases due to high precious metal content
Solution Approach 1:
The patent applies local quality by creating a Pt-Rh alloy catalyst where platinum and rhodium are distributed in a specific atomic ratio (0.5-2.0) within the catalyst particles. This localized alloying structure optimizes the catalytic activity at active sites while reducing overall precious metal content compared to traditional Pt-Rh gauze structures.
Solution Approach 2:
The patent uses composite materials by combining Pt-Rh alloy particles with a ceramic substrate (such as cordierite or alumina). This composite structure provides both the catalytic functionality of precious metals and the structural stability and cost-effectiveness of ceramic materials, reducing reliance on high quantities of precious metals.
2Reliability
If the catalyst structure is optimized for high catalytic activity, then the exhaust gas purification efficiency is improved, but the durability under thermal shock deteriorates
Solution Approach 1:
The patent applies the nested doll principle by embedding Pt-Rh alloy particles within pores of a ceramic substrate structure. The catalyst particles are nested within the three-dimensional pore network of the ceramic, allowing the ceramic matrix to provide thermal stability and shock resistance while the nested metal particles provide catalytic activity.
Solution Approach 2:
The patent changes physical parameters by controlling the particle size of Pt-Rh alloy (0.1-10 μm) and the pore size of the ceramic substrate (3-10 μm). These parameter optimizations ensure that the catalyst maintains high surface area for catalytic activity while the ceramic structure provides thermal stability against shock from temperature fluctuations in exhaust gases.
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 configuration effectively suppresses the increase in pressure loss after ash deposition, improving the life and performance of the exhaust gas purifying system by allowing better ash penetration and burning, while maintaining high purifying efficiency for carbon monoxide, hydrocarbons, and nitrogen oxides.
Implementation Method 1
a Pt-Rh alloy catalyst having an average particle size of 0.1 to 10 μm and an atomic ratio of Pt to Rh of 0.5 to 2.0
Data Source
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AI summary
An object of the present invention is to provide an exhaust gas purifying catalyst which has good exhaust gas purifying performance and can suppress an increase in pressure loss after the deposit of ash. An exhaust gas purifying catalyst for purifying exhaust gas discharged from an internal combustion engine includes: a wall flow type substrate in which an inflow-side cell having an open at an exhaust gas inflow-side end, and an outflow-side cell adjacent to the inflow-side cell and having an open at an exhaust gas outflow-side end are separated by a porous partition wall; and a catalyst layer formed at a plurality of locations in pores of the partition wall and containing at least one catalyst metal. The catalyst layer is biasedly located toward a side of the outflow-side cell in a thickness direction of the partition wall.