Exhaust Gas Catalyst Layered Rhodium Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Exhaust gas-purifying catalysts that effectively reduce nitrogen oxides often emit hydrogen sulfide, leading to odor issues and environmental concerns due to the use of nickel, which is regulated in many areas.
Innovation Solution
A catalyst design with a layered structure of platinum/palladium and rhodium layers, where the second section has a lower oxygen storage material content and a higher rhodium content, reducing hydrogen sulfide emission by minimizing sulfur constituent adsorption and desorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If exhaust gas-purifying catalysts use nickel to reduce hydrogen sulfide emission, then H2S emission is reduced, but environmental compliance deteriorates due to nickel being designated as an environmental load substance
Solution Approach 1:
The patent extracts nickel from the catalyst composition entirely, replacing it with a layered structure of platinum group metals (Pt, Pd, Rh) supported on cerium oxide. This removal of the harmful substance (nickel) while maintaining H2S reduction functionality through alternative catalytic materials directly resolves the contradiction between reducing H2S emission and maintaining environmental compliance.
Solution Approach 2:
The patent employs a composite catalytic system consisting of multiple precious metals (Pt, Pd, Rh) distributed in a layered structure on cerium oxide support. This composite material approach achieves the H2S reduction function previously attributed to nickel, while using environmentally compliant materials that are not designated as environmental load substances.
2Device complexity
If exhaust gas-purifying catalysts use a single-layer structure, then device complexity is reduced, but purification performance deteriorates due to inability to simultaneously optimize NOx reduction and H2S suppression
Solution Approach 1:
The patent divides the catalyst into multiple functional layers: a first layer containing Pt and Pd for NOx reduction, and a second layer containing Rh for H2S suppression. This segmentation allows each layer to be optimized for its specific function, achieving simultaneous NOx purification and H2S emission control that would be difficult in a single-layer structure.
Solution Approach 2:
The patent applies local quality by distributing different precious metals in specific layers: Pt and Pd are concentrated in the first layer for NOx reduction activity, while Rh is concentrated in the second layer for H2S suppression. This localized distribution of catalytic functions optimizes performance for each target pollutant while maintaining overall catalyst reliability.
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 efficient NOx purification with reduced hydrogen sulfide emission, maintaining performance while minimizing nickel usage and adhering to environmental regulations.
Implementation Method 1
a catalytic layer supported by the support and containing an oxygen storage material... a first catalytic layer containing platinum and/or palladium and a second catalytic layer containing rhodium
Implementation Method 2
Cerium oxide has a high oxygen storage capacity and is known as a component effective in improving the performance of the exhaust gas-purifying catalyst
Data Source
AI summary
An exhaust gas-purifying catalyst includes a support provided with one or more through-holes through which exhaust gas flows, and a catalytic layer supported by the support and containing an oxygen storage material. The exhaust gas-purifying catalyst includes a first section to which the exhaust gas is supplied, and a second section to which the exhaust gas having passed through the first section is supplied. The catalytic layer includes a layered structure of a first catalytic layer containing platinum and/or palladium and a second catalytic layer containing rhodium in the first catalytic section and further includes a third layer containing rhodium in the second section. The second section is smaller in oxygen storage material content per unit volumetric capacity than the first section.