Exhaust Gas Purifying Catalyst Partition Layer Configuration
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Solution Overview
Problem
Conventional exhaust gas purifying catalysts with a wall-flow structure face challenges in achieving both reduced pressure drop and enhanced purification performance, as the placement of catalyst layers inside the partition can lead to increased pressure loss and inefficient use of catalysts.
Innovation Solution
The exhaust gas purifying catalyst features a wall-flow structure with a first catalyst layer inside the partition, extending from the inflow end, and a second catalyst layer extending from the outflow end, where the first catalyst layer occupies 40-60% of the partition's thickness and the second catalyst layer covers the entire thickness, with specific length ranges and overlapping configurations to optimize contact with exhaust gas and reduce pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Rh layer is stacked on the surface of the partition to enhance purification performance, then the purification performance is improved, but the flow passage resistance increases resulting in increased pressure loss
Solution Approach 1:
The patent transitions from placing catalyst layers only on the outer surface of the partition to positioning them inside the partition wall thickness. The first catalyst layer is placed at the inlet side within the partition thickness, and the second catalyst layer is placed at the outlet side within the partition thickness, utilizing the internal dimension of the partition structure to reduce flow resistance while maintaining catalytic functionality.
Solution Approach 2:
Different catalyst layers are strategically positioned at different locations within the partition structure. The first catalyst layer (containing Pt and Rh) is positioned at the inlet side inside the partition, while the second catalyst layer (containing Pd and Rh) is positioned at the outlet side inside the partition. This localized placement optimizes the purification function at different stages of gas flow while minimizing overall pressure loss.
2Stress or pressure
If catalyst layers are disposed inside the partition to reduce pressure drop, then the pressure drop is reduced, but the efficiency of use of the catalyst may be reduced
Solution Approach 1:
The patent applies different catalyst compositions and positions them at specific locations within the partition to optimize both pressure drop and catalyst efficiency. The first catalyst layer containing Pt and Rh is positioned at the inlet side, while the second catalyst layer containing Pd and Rh is positioned at the outlet side, ensuring efficient catalyst utilization throughout the gas flow path.
Solution Approach 2:
The patent uses composite catalyst layers combining different precious metals (Pt, Pd, Rh) with support materials such as alumina and ceria. These composite materials enhance catalyst efficiency by improving dispersion, stability, and catalytic activity, ensuring high purification performance even when catalysts are positioned inside the partition to minimize pressure drop.
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 reduces pressure drop while enhancing purification performance by ensuring a high frequency of catalyst contact with exhaust gas and minimizing flow path narrowing, resulting in improved NOx purification and reduced pressure loss.
Implementation Method 1
a first catalyst layer formed in a region inside the partition and in contact with at least the inlet cell such that the first catalyst layer extends in a direction of extension of the partition from the exhaust gas inflow end; and a second catalyst layer formed in a region inside the partition and in contact with at least the outlet cell
Data Source
AI summary
An exhaust gas purifying catalyst includes: a wall-flow structure substrate including an inlet cell, an outlet cell, and a porous partition; a first catalyst layer formed inside the partition such that a thickness of the first catalyst layer is between 40% and 60%, inclusive, of an overall thickness Tw of the partition; and a second catalyst layer formed inside the partition such that the second catalyst layer extends across an entire region of the partition in a thickness direction thereof.