Ferrosilicate Catalyst for Low-Temperature NOx Reduction
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Solution Overview
Problem
Current ferrosilicate catalysts lack high catalytic activity for nitrogen oxides reduction at low temperatures and exhibit poor hydrothermal stability, especially when using ammonia as a reducing agent.
Innovation Solution
Development of a ferrosilicate catalyst with an iron-containing β-framework structure, characterized by a SiO2/Fe2O3 mol ratio of 20 to 300 and a high percentage of isolated iron ions, which maintains catalytic activity and stability even after hydrothermal treatment, utilizing ammonia, urea, or organic amines as reducing agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ferrosilicate catalysts are used, then the catalyst structure is simple, but the catalytic activity for nitrogen oxides reduction at low temperatures is insufficient and hydrothermal stability is poor
Solution Approach 1:
The patent uses a composite catalyst structure combining ferrosilicate with specific framework types (ZSM-5, beta, or Y zeolite) and incorporates multiple metal components (Fe, Cu, Ga, or Pt) to achieve both high hydrothermal stability and low-temperature catalytic activity. The composite nature allows each component to contribute its strengths while mitigating individual weaknesses.
Solution Approach 2:
The patent creates local active sites with specific metal compositions and oxidation states within the broader ferrosilicate framework. The controlled incorporation of Cu, Ga, or Pt at specific locations and ratios creates localized regions optimized for nitrogen oxides reduction while the overall framework maintains structural stability under hydrothermal conditions.
2Productivity
If conventional ferrosilicate catalysts are used, then the manufacturing process is simple, but the catalytic activity at low temperatures is insufficient
Solution Approach 1:
The patent employs preliminary ion exchange or impregnation steps during catalyst synthesis to pre-position metal components (Cu, Ga, Pt) in optimal configurations and oxidation states. This preliminary structuring ensures high catalytic activity is achieved without requiring complex post-synthesis treatments or activation procedures.
Solution Approach 2:
The patent optimizes specific parameters including metal loading ratios (Fe:Cu:Ga:Pt), framework silica-to-alumina ratios, and calcination temperatures to maximize catalytic activity. By systematically adjusting these parameters during synthesis, the catalyst achieves superior low-temperature performance while maintaining a relatively straightforward manufacturing process.
3Reliability
If ferrosilicate with high iron content is used, then the catalyst has potential for nitrogen oxides reduction, but the hydrothermal stability deteriorates
Solution Approach 1:
The patent optimizes the iron content parameter within a specific range (0.1-5.0 wt%) and controls the SiO2/Fe2O3 ratio (20-300) to balance catalytic activity and hydrothermal stability. This parameter optimization prevents excessive iron aggregation that would compromise stability while maintaining sufficient iron for nitrogen oxides reduction.
Solution Approach 2:
The patent distributes iron within a composite ferrosilicate framework that includes stabilizing components (Cu, Ga, Pt) and a structured zeolite framework. This composite structure allows higher effective iron utilization for catalysis while the framework and additional metals prevent iron sintering and maintain hydrothermal stability.
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 demonstrates high catalytic activity for nitrogen oxides reduction across a broad temperature range, including low temperatures, and retains hydrothermal stability, enhancing the efficiency of the reduction process.
Implementation Method 1
a catalyst for reducing nitrogen oxides comprising a ferrosilicate having β-framework structure, and a process for reducing nitrogen oxides comprising reacting nitrogen oxides with at least one of ammonia, urea and an organic amine using the catalyst
Data Source
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AI summary
A first catalyst for reducing nitrogen oxides comprising a crystalline silicate containing an iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is 20-300 and at least 80% of the contained iron is an isolated iron ion Fe3+. A second catalyst for reducing nitrogen oxides comprising a crystalline silicate containing an iron in β-framework structure wherein a SiO2/Fe2O3 mol ratio is 20-300 and log(SiO2/Al2O3) by mol is at least 2. A predominant part of the contained iron is isolated iron ion Fe3+ and at least a part thereof preferably has a tetrahedral coordination. These catalysts have high hydrothermal stability and exhibit enhanced activity for reducing nitrogen oxides by a reaction with a reducing agent such as ammonia, urea or an organic amine in a broad temperature range between lower temperature and higher temperature.