Copper-Loaded AFX Zeolite Synthesis for NOx Conversion
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Solution Overview
Problem
Current zeolites used for selective catalytic reduction of NOx, such as copper-exchanged chabazites, have limitations in terms of NOx conversion efficiency and hydrothermal resistance, particularly at low temperatures, and there is a lack of effective synthesis methods for microporous aluminosilicate materials of structural type AFX for improved catalytic performance.
Innovation Solution
A process for preparing a microporous aluminosilicate material of AFX structural type containing copper, involving the mixing of aluminum, silicon, soda, copper, and specific organic complexing agents, followed by hydrothermal treatment and calcination, which results in a pure AFX zeolite without other crystalline or amorphous phases, enhancing NOx conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper-exchanged chabazites (Cu-SSZ-13, Cu-SAPO-34) are used for NH3-SCR applications, then NOx conversion efficiency is improved, but hydrothermal resistance deteriorates
Solution Approach 1:
The patent changes the structural parameters by selecting AFX-type zeolite framework instead of traditional CHA-type (chabazite), and optimizes Si/Al ratio and copper loading parameters to achieve both high NOx conversion efficiency and improved hydrothermal stability
Solution Approach 2:
The patent creates a composite catalyst system combining AFX-type zeolite with specific copper loading and hierarchical pore structure, integrating multiple functional characteristics to simultaneously achieve high activity and stability
2Ease of manufacture
If AFX structural type zeolites are synthesized with traditional methods, then synthesis is simplified, but manufacturing precision deteriorates (unwanted phases appear)
Solution Approach 1:
The patent precisely controls synthesis parameters including Si/Al ratio (2.0-4.0), CuO content (1.0-5.0 wt%), pH value (9.0-11.0), and aging temperature (40-80°C) to obtain pure AFX phase without unwanted crystalline or amorphous phases, while maintaining relatively simple synthesis procedure
3Manufacturing precision
If copper is introduced by ion exchange after zeolite formation, then manufacturing precision is maintained, but productivity deteriorates (multi-step process)
Solution Approach 1:
The patent combines the copper introduction step with the zeolite synthesis step into a single hydrothermal treatment process, adding copper salts to the synthesis gel and achieving both zeolite crystallization and copper incorporation simultaneously, thereby improving productivity while maintaining uniform copper distribution
Solution Approach 2:
The patent performs preliminary copper salt addition to the synthesis gel before hydrothermal treatment, ensuring copper is pre-distributed in the reaction mixture to achieve uniform incorporation during the crystallization process, eliminating the need for separate ion exchange steps
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 process yields a catalyst with superior NOx conversion properties compared to existing AFX structural type zeolites, demonstrating improved performance in NOx conversion reactions and increased hydrothermal stability.
Implementation Method 1
the mixture, in an aqueous medium, of at least one source of aluminum, of at least one source of silicon, of soda, of at least one source of copper, of an organic OCPLX complexing agent
Implementation Method 2
the hydrothermal treatment of said gel at a temperature between 130 and 180°C, under autogenous reaction pressure, for a period of between 1 and 8 days with stirring to obtain the crystallization of said microporous aluminosilicate material
Implementation Method 3
heat treatment by drying the solid obtained at the end of the previous step at a temperature between 80 and 120°C under a flow of inert gas followed by calcination in dry air at a temperature between 400 and 600°C
Implementation Method 4
the use of this material, in particular for the selective catalytic reduction of NOx in the presence of a reducing agent in particular on the Diesel or spark ignition engine
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for producing a microporous aluminosilicate material having an AFX structure and comprising copper, said method including at least the steps of: mixing, in an aqueous medium, at least one source of aluminium, at least one source of silicon, at least one source of copper, a TETA or TEPA organic complexing agent, and a DABCO-C4 structure-directing agent, in order to obtain a gel; and hydrothermal treatment of said gel while stirring so as to crystallise the microporous aluminosilicate material having an AFX structure and comprising copper.