Segmented Diesel Oxidation Catalyst Layers
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Solution Overview
Problem
The existing oxidation catalysts for diesel engines require complex and costly production processes due to the need for adjusting the amounts of Pt and Pd catalysts based on exhaust gas characteristics, increasing production costs without a proportional improvement in performance.
Innovation Solution
A substrate with a hexagonal section is designed to have multiple passages for exhaust gas flow, featuring an upstream-side catalyst layer with Pt and Pd, a downstream-side inner catalyst layer with reduced Pt, and a downstream-side outer catalyst layer with intensive Pt arrangement, allowing for uniform application and reduced production costs while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different materials are arranged in upstream and downstream sides of the substrate with adjusted amounts of Pt and Pd corresponding to exhaust gas characteristics, then the oxidation catalyst performance is improved, but the production cost is increased due to complex blending processes
Solution Approach 1:
The catalyst layer is divided into three distinct layers (upstream-side, downstream-side inner, and downstream-side outer) with different catalyst compositions. The upstream-side layer contains Pt and Pd for oxidizing HC and CO, while the downstream-side layers contain Pt for oxidizing NO. This segmentation allows each layer to perform specific functions with optimized catalyst amounts, improving overall performance while enabling standardized production of each layer type.
Solution Approach 2:
Different catalyst compositions are applied to different regions of the substrate. The upstream-side catalyst layer has a composition optimized for HC and CO oxidation, while the downstream-side inner and outer layers have compositions optimized for NO oxidation. This local quality approach ensures that each region of the catalyst has the appropriate catalyst amounts and types for its specific function, improving performance without requiring complex blending of multiple catalyst types throughout the entire substrate.
2Reliability
If multiple catalysts are blended and arranged in predetermined positions corresponding to exhaust gas characteristics, then the oxidation efficiency is improved, but the device complexity is increased
Solution Approach 1:
The catalyst system is segmented into three distinct layers with clearly defined compositions and functions. The upstream-side catalyst layer contains Pt and Pd, while the downstream-side inner and outer layers contain Pt. This segmentation simplifies the arrangement process by defining specific zones for different catalyst types, reducing the complexity of blending and positioning multiple catalysts throughout the substrate.
Solution Approach 2:
The upstream-side catalyst layer with Pt and Pd serves multiple functions by oxidizing both HC and CO, while the downstream-side layers with Pt serve the universal function of oxidizing NO. This multi-functionality approach reduces the need for multiple specialized catalysts in different positions, simplifying the overall catalyst arrangement while maintaining high oxidation efficiency for multiple exhaust components.
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 maintains oxidation efficiency and reduces production costs by allowing for a fixed amount of Pt and Pd in the upstream-side and downstream-side inner catalyst layers, with adjustable Pt in the downstream-side outer catalyst layer, ensuring equivalent performance to conventional catalysts with fewer resources.
Implementation Method 1
HC and CO are removed by oxidation promotion effect of Pt and Pd included in the upstream-side catalyst layer
Implementation Method 2
Pt is arranged intensively in the fixed range of the downstream-side outer catalyst layer so as to improve the oxidation efficiency
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3~4
AI summary
Provided is an oxidation catalyst for diesel engines, which enables reduction of the production cost, while maintaining the performance of an oxidation catalyst. An oxidation catalyst for diesel engines, which is configured of a plurality of catalyst layers containing Pt and/or Pd. This oxidation catalyst for diesel engines is composed of an upstream-side catalyst layer 5, a downstream-side inner catalyst layer 6 in the flow direction of the exhaust gas, and a downstream-side outer catalyst layer 7 is additionally formed so as to cover the surface of the downstream-side inner catalyst layer 6. The upstream-side catalyst layer 5 and the downstream-side inner catalyst layer 6 contain Pd, and the downstream-side outer catalyst layer 7 contains Pt. The amounts of Pt and Pd contained in the upstream-side catalyst layer 5 and the amounts of Pt and Pd contained in the downstream-side inner catalyst layer 6 are constantly set to certain values, while the amount of Pt contained in the downstream-side outer catalyst layer 7 is set to a value which enables the oxidation efficiency to be at a predetermined value or higher.