Isomorphous Zeolite Catalyst for SCR
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Solution Overview
Problem
Current SCR catalysts face challenges in maintaining catalytic activity at both low and high temperatures, particularly under hydrothermal conditions, and have limitations in nitrogen oxide conversion efficiency and durability.
Innovation Solution
A zeolitic framework of silicon and aluminum atoms with a fraction of silicon atoms isomorphously substituted with tetravalent metals like Ti, Cu, Fe, and Co, promoting the catalyst with metals such as Cu, Fe, and Co, and optimizing the silica to alumina ratio and metal to alumina ratios for enhanced performance across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal-promoted zeolite catalysts are used for SCR, then catalytic activity is improved, but hydrothermal stability deteriorates under harsh conditions
Solution Approach 1:
The patent combines metal-promoted zeolite catalyst with a silica-alumina washcoat layer to create a composite catalyst structure. The washcoat layer protects the zeolite from hydrothermal degradation while maintaining catalytic activity, resolving the contradiction between productivity and reliability under harsh conditions.
Solution Approach 2:
The patent optimizes the silica-to-alumina ratio in the washcoat layer and controls the metal loading amount on the zeolite to achieve optimal balance between catalytic activity and hydrothermal stability. By adjusting these parameters, the catalyst maintains high activity while resisting dealumination under hydrothermal conditions.
2Reliability
If high silica to alumina ratio is used in zeolite, then hydrothermal stability is improved, but low temperature conversion efficiency deteriorates
Solution Approach 1:
The patent creates different functional zones: the high silica-to-alumina ratio zeolite core provides hydrothermal stability, while the metal promotion and surface modification create active sites optimized for low temperature conversion. This local differentiation resolves the contradiction between stability and activity.
Solution Approach 2:
The combination of high silica-to-alumina ratio zeolite with metal promoters and silica-alumina washcoat creates a composite structure where each component contributes specific properties: the zeolite provides structural stability, while metal sites provide low-temperature catalytic activity.
3Productivity
If metal loading amount is increased, then catalytic activity is improved, but cost and complexity increase
Solution Approach 1:
The patent optimizes the metal loading amount within specific ranges (0.1-10 wt% for Cu, 0.1-5 wt% for Fe, 0.1-3 wt% for Co) to achieve sufficient catalytic activity while avoiding excessive complexity and cost. This parameter optimization resolves the contradiction between productivity and device complexity.
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 modified catalyst achieves balanced performance for both low and high temperatures, maintaining high nitrogen oxide conversion efficiency and durability, effectively meeting stringent NOx regulations like Euro 6, with improved NO+ formation and hydrothermal stability.
Implementation Method 1
a fraction of the silicon atoms are isomorphously substituted with a tetravalent metal
Implementation Method 2
The SCR process uses catalytic reduction of nitrogen oxides with ammonia in the presence of atmospheric oxygen with the formation predominantly of nitrogen and steam
Implementation Method 3
Molecular sieves such as zeolites have been used in the selective catalytic reduction (SCR) of nitrogen oxides
Data Source
AI summary
Described is a selective catalytic reduction catalyst comprising a zeolitic framework material of silicon and aluminum atoms, wherein a fraction of the silicon atoms are isomorphously substituted with a tetravalent metal. The catalyst can include a promoter metal such that the catalyst effectively promotes the reaction of ammonia with nitrogen oxides to form nitrogen and H2O selectively over a temperature range of 150 to 650° C. A method for selectively reducing nitrogen oxides and an exhaust gas treatment system are also described.