Exhaust Gas Catalyst Pd Gradient for Low-Temp Warm-Up
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Solution Overview
Problem
Exhaust gas cleaning catalysts exhibit deteriorated performance at low temperatures during engine start-up and generate nitrous oxide (N2O), a greenhouse gas, which is a concern for emissions regulations.
Innovation Solution
A multilayer catalyst structure with a Pd-containing lower layer and a Pd-free upper layer, where the Pd concentration gradient decreases from the inlet to the outlet, enhancing warm-up performance and suppressing N2O generation by distributing Pd unevenly to improve catalyst activation and reduce N2O production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform Pd-containing catalyst layer is used, then CO and HC elimination performance is improved, but warm-up performance deteriorates at low temperatures
Solution Approach 1:
The catalyst layer is designed with non-uniform Pd distribution, creating different local compositions: a first catalyst layer with higher Pd content for CO/HC elimination and a second catalyst layer with lower Pd content for warm-up performance. This local quality differentiation resolves the contradiction between elimination performance and warm-up capability.
Solution Approach 2:
The catalyst layer is segmented into multiple layers with distinct Pd concentrations. The first catalyst layer (higher Pd) and second catalyst layer (lower Pd) are separated into different spatial zones, allowing each segment to perform its specific function optimally without interfering with the other.
2Reliability
If Pd is uniformly distributed in the catalyst layer, then catalytic activity is maintained, but N2O generation increases
Solution Approach 1:
Different local regions of the catalyst layer have different Pd concentrations tailored to specific functions. The first catalyst layer with higher Pd content maintains catalytic activity for CO/HC elimination, while the second catalyst layer with lower Pd content suppresses N2O generation, thus resolving the contradiction between activity and harmful emissions.
3Ease of manufacture
If a single-layer catalyst structure is used, then manufacturing simplicity is maintained, but cleaning performance at low temperature deteriorates
Solution Approach 1:
The catalyst layer is divided into multiple layers with different Pd concentrations to improve low-temperature cleaning performance. Despite the increased structural complexity, the manufacturing process remains relatively simple through sequential coating or extrusion methods, balancing performance improvement with ease of manufacture.
4Reliability
If Pd content is increased throughout the catalyst layer, then CO and HC elimination performance is improved, but N2O generation increases and cost increases
Solution Approach 1:
Instead of uniformly increasing Pd content throughout the catalyst layer, the invention applies higher Pd content locally in the first catalyst layer where it is most needed for CO/HC elimination, while maintaining lower Pd content in the second catalyst layer to suppress N2O generation. This localized approach achieves high elimination performance without the penalties of increased N2O generation and excessive cost.
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 catalyst achieves rapid temperature increase and improved performance at low temperatures, effectively eliminating harmful components while minimizing N2O generation, thus meeting the requirements for efficient exhaust gas cleaning and emissions control.
Implementation Method 1
imparting a Pd concentration gradient from the exhaust gas inlet side end towards the exhaust gas outlet side of an exhaust gas cleaning catalyst
Implementation Method 2
a catalyst coat layer formed on a surface of the substrate... Pd being supported on one layer and Rh being separately supported on another layer
Data Source
AI summary
The exhaust gas cleaning catalyst according is provided with a substrate and a catalyst coat layer formed on a surface of the substrate. The catalyst coat layer is formed as a laminate structure having an upper layer and a lower layer. The upper layer is a Pd-free layer that does not contain Pd, and the lower layer is a Pd-containing layer. In addition, when a region of the lower layer that corresponds to 20% of the length of the exhaust gas cleaning catalyst from the exhaust gas inlet side end towards the exhaust gas outlet side of the exhaust gas cleaning catalyst is divided into four equal regions to be each 5% of the length, the relationship A>B>C is satisfied, where A, B, and C represents the Pd content in the first, second, and third region respectively.