Honeycomb Structure Catalyst for NO Oxidation
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Solution Overview
Problem
Current exhaust-gas purifying systems face inefficiencies in NOx reduction due to imbalanced NO and NO2 ratios, with existing catalysts being costly, unstable at varying temperatures, and prone to sintering or high pressure loss.
Innovation Solution
A honeycomb structure with a porous partition wall loaded with a transition metal oxide catalyst containing Fe and Mn, which oxidizes NO to NO2, maintaining a balanced NO and NO2 ratio for efficient SCR catalyst converter operation, featuring a specific mole ratio and loading amount to ensure stability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a noble metal catalyst is used to oxidize NO into NO2, then the NO to NO2 conversion is effective, but the cost increases significantly
Solution Approach 1:
The patent replaces expensive noble metal catalysts with a cheaper transition metal oxide catalyst system. The catalyst uses Fe, Mn, and Co oxides which are significantly less costly than noble metals like Pt, while still achieving the required NO oxidation function in the exhaust gas treatment system.
Solution Approach 2:
The patent optimizes the compositional parameters of the catalyst by specifying precise ratios of Fe, Mn, and Co oxides. The catalyst contains Fe oxide (40-70 wt%), Mn oxide (10-30 wt%), and Co oxide (5-20 wt%), with controlled particle size distribution (0.1-10 μm) to achieve optimal catalytic activity for NO oxidation without requiring noble metals.
2Productivity
If the catalyst particle size is reduced to increase surface area, then the catalytic activity improves, but sintering occurs more quickly reducing durability
Solution Approach 1:
The patent specifies an optimal particle size range of 0.1-10 μm for the transition metal oxide catalyst particles. This controlled particle size provides sufficient surface area for catalytic activity while being large enough to resist rapid sintering, thus balancing activity and durability. The multi-component oxide system also provides structural stability against sintering.
Solution Approach 2:
The patent uses a composite catalyst system combining Fe oxide, Mn oxide, and Co oxide in specific ratios. This composite structure provides synergistic effects where the multiple oxide components work together to maintain catalytic activity while improving resistance to sintering and thermal degradation compared to single-component catalysts.
3Loss of energy
If high porosity is used to reduce pressure loss, then fluid flow improves, but the structural strength decreases
Solution Approach 1:
The patent optimizes the porosity parameter of the honeycomb structure to balance pressure loss and strength. By controlling the pore size, pore distribution, and wall thickness parameters, the structure achieves sufficient permeability for low pressure loss while maintaining the mechanical strength required to withstand exhaust gas conditions and thermal cycling.
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 honeycomb structure achieves a balanced NO and NO2 ratio, enhancing NOx purification efficiency while being cost-effective and stable across a wide temperature range, with improved durability and reduced pressure loss.
Implementation Method 1
an oxidation catalyst made of a transition metal oxide at least including Fe and Mn to oxidize NO gas
Data Source
AI summary
A honeycomb structure includes: a honeycomb structure body including a plurality of cells defined by a partition wall and serving as a through channel of fluid; and a plugging portion to alternately plug open end parts of the plurality of cells on one side as an inflow side of the exhaust gas and open end parts on the other side as an outflow side of the exhaust gas. The partition wall is loaded, on the side of the outflow cells, with an oxidation catalyst made of a transition metal oxide at least including Fe and Mn to oxidize NO gas or an oxidation catalyst made of a transition metal oxide loaded at CeO2 and at least including Fe and Mn to oxidize NO gas. The loading amount of the oxidation catalyst is 5.0 g/L or more and 50 g/L or less.