Zone-Coated Catalytic Converter Reducing Noble Metal Usage
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Solution Overview
Problem
Existing catalytic converters face a trade-off between noble metal catalyst loading and NOx purification performance, where reducing the amount of noble metals like Rh decreases catalytic activity and purification efficiency, particularly at high temperatures.
Innovation Solution
A catalytic converter design with a substrate having a cell structure, where the first catalyst layer with Rh covers 80-100% of the substrate's length on the upstream side and the second catalyst layer with Pd or Pt covers 20-50% on the downstream side, optimizing NOx purification performance while minimizing noble metal usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of noble metal catalyst is significantly decreased to reduce cost and material risk, then cost competitiveness is improved, but catalytic activity and purification performance are significantly decreased
Solution Approach 1:
The patent applies local quality by creating zone-coated catalysts with different noble metal compositions in different regions of the substrate. The upstream side contains Rh-based catalyst for high-temperature NOx purification, while the downstream side contains Pd or Pt-based catalyst for low-temperature activity. This spatial differentiation allows each region to perform its specific function optimally, maintaining high purification performance while reducing overall noble metal usage.
Solution Approach 2:
The patent segments the catalyst layer into multiple zones along the exhaust gas flow direction. By dividing the substrate into upstream and downstream regions with different catalyst compositions, the system optimizes performance for different temperature conditions without requiring high amounts of expensive Rh throughout the entire catalyst structure.
2Quantity of substance
If the amount of cerium oxide in the co-catalyst is increased to improve OSC, then oxygen storage capacity is improved, but NOx purification performance of Rh is decreased
Solution Approach 1:
The patent applies local quality by controlling the distribution of cerium oxide in the support material. The upstream catalyst layer containing Rh has a support with lower cerium oxide content (0-10 mass%) to maintain high NOx purification performance, while the downstream catalyst layer containing Pd or Pt has a support with higher cerium oxide content (10-30 mass%) to provide sufficient OSC. This spatial differentiation resolves the trade-off between OSC and NOx purification performance.
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 achieves superior NOx purification performance while reducing the amount of noble metal catalysts, particularly Rh, by strategically positioning Rh on the upstream side for high-temperature resistance and Pd or Pt on the downstream side for improved low-temperature performance, suppressing alloying and maintaining high purification efficiency.
Implementation Method 1
the first catalyst layer is formed of a support and Rh which is a noble metal catalyst supported on the support
Implementation Method 2
the second catalyst layer is formed of a support and Pd or Pt which is a noble metal catalyst supported on the support
Implementation Method 3
CeO2 has a function of adsorbing and desorbing oxygen and a function of storing oxygen (OSC: Oxygen Storage Capacity)
Data Source
AI summary
Provided is a catalytic converter capable of obtaining superior NOx purification performance while reducing the amount of a noble metal catalyst. A catalytic converter 10 includes: a substrate 1 having a cell structure in which exhaust gas flows; and catalyst layers 3 that are formed on cell wall surfaces 2 of the substrate 1. The catalyst layers 3 include a first catalyst layer 4 disposed on an upstream side of the substrate 1 in an exhaust gas flow direction and a second catalyst layer 5 disposed on a downstream side of the substrate in the exhaust gas flow direction. The first catalyst layer 4 is formed of a support and rhodium which is a noble metal catalyst supported on the support. The second catalyst layer 5 is formed of a support and palladium or platinum which is a noble metal catalyst supported on the support. The first catalyst layer 4 is formed in a range of 80% to 100% of a total length of the substrate 1 starting from an end of the substrate on the upstream side, and the second catalyst layer 15 5 is formed in a range of 20% to 50% of the total length of the substrate 1 starting from an end of the substrate on the downstream side.