Composite Catalyst for NOx Reduction and Soot Oxidation
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Solution Overview
Problem
Current catalysts for selective reduction of nitrogen oxides (NOx) in off-gases from lean combustion engines are ineffective at temperatures between 150 and 550°C and do not simultaneously address the reduction of hydrocarbons and soot particles.
Innovation Solution
A catalyst composition comprising acidic zeolite or zeotype components physically admixed with redox active metal compounds, such as CeO2-ZrO2, Cu/Al2O3, and Mn/Al2O3, which exhibit a synergistic effect in enhancing NOx reduction and soot oxidation activities, allowing for reduced zeolite content without sacrificing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional catalysts are used for NOx reduction, then NOx reduction activity is achieved, but the catalysts are ineffective at temperatures between 150 and 550°C
Solution Approach 1:
The patent employs composite catalyst materials combining zeolite support with transition metal compounds (Cu, Fe, Mn) and metal oxides (CeO2-ZrO2). This composite structure enables the catalyst to achieve effective NOx reduction across the extended temperature range of 150-550°C by leveraging the synergistic properties of different materials: zeolite provides structural stability and acid sites, transition metals facilitate NOx reduction, and CeO2-ZrO2 enhances redox activity and temperature adaptability.
2Adaptability or versatility
If catalysts are designed for NOx reduction, then DeNOx activity is improved, but soot and hydrocarbon oxidation activity is not simultaneously addressed
Solution Approach 1:
The catalyst composition is designed to perform multiple functions simultaneously: NOx reduction, soot oxidation, and hydrocarbon oxidation. The transition metal compounds (Cu, Fe, Mn) and metal oxide (CeO2-ZrO2) components provide redox activity that facilitates both NOx reduction and soot/HC oxidation, while the zeolite support provides acid sites for hydrocarbon conversion. This multi-functional design eliminates the need for separate catalysts for different functions.
Solution Approach 2:
The composite structure combines materials with complementary functions: zeolite for acid-catalyzed hydrocarbon conversion, transition metals for NOx reduction, and CeO2-ZrO2 for soot oxidation and redox activity. The synergistic interaction between these components enables simultaneous DeNOx, DeSoot, and hydrocarbon oxidation activities in a single catalyst system.
3Quantity of substance
If zeolite content is reduced to lower cost, then manufacturing cost decreases, but catalyst performance may be compromised
Solution Approach 1:
The patent optimizes the compositional parameters of the catalyst by replacing a portion of the zeolite support with CeO2-ZrO2 metal oxide. This parameter change maintains catalyst performance while reducing zeolite content. The CeO2-ZrO2 component compensates for the reduced zeolite by providing additional redox activity and surface area for catalytic reactions, thereby maintaining NOx reduction, soot oxidation, and hydrocarbon conversion activities.
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 composite catalysts demonstrate significantly improved NOx reduction and soot oxidation activities across the desired temperature range, with reduced zeolite content and lower ammonium slip at high temperatures, making them suitable for integrated DeNOx-DeSoot systems.
Implementation Method 1
redox active metal compounds which reversibly can be oxidized and reduced in terms of changes in oxidation number, or oxidation state, of the metal atom or compound
Implementation Method 2
hydrocarbons, CO and soot particles which can be reduced or removed by catalytic oxidation
Implementation Method 3
catalyst composition comprising one or more acidic zeolite or zeotype components physically admixed with one ore more redox active metal compounds shown an improved activity in the selective reduction of nitrogen oxides
Data Source
AI summary
Catalyst composition for selective reduction of nitrogen oxides and soot oxidation comprising a physical mixture of one or more acidic zeolite or zeotype components with one ore more redox active metal compounds and a method for selective reduction of nitrogen oxides and soot oxidation by use of the catalyst composition.