Low-Temperature AFX Zeolite Synthesis via Quaternary Ammonium Template
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Solution Overview
Problem
Current methods for synthesizing zeolites of structural type AFX require high temperatures and long crystallization times, making them inefficient and resource-intensive, and often necessitate high-pressure reactors.
Innovation Solution
A process involving the mixing of silicon, aluminum, and 1,6-bis(methylpiperidinium)hexane dihydroxide with alkali metals in specific molar ratios, followed by hydrothermal treatment at temperatures between 75°C and 95°C under atmospheric pressure for 40 to 100 hours, to produce a zeolite with high purity and controlled SiO2/Al2O3 ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional synthesis methods are used, then zeolite AFX can be obtained, but high temperature and long crystallization time are required
Solution Approach 1:
The patent changes the chemical parameters of the synthesis system by introducing a specific quaternary ammonium salt (1,4-diazabicyclo[2.2.2]octane dibromide) as structure-directing agent and adjusting the molar ratios of reactants (SiO2/Al2O3=8-40, R/SiO2=0.05-0.50). These parameter changes enable the synthesis to proceed at lower temperatures (75-95°C) while maintaining high productivity through optimized reaction conditions.
Solution Approach 2:
The quaternary ammonium salt acts as an intermediary substance that mediates the formation of zeolite AFX structure. It directs the assembly of silicon and aluminum species into the desired crystal structure, enabling low-temperature synthesis by providing a template that reduces the activation energy required for crystallization.
2Loss of time
If conventional synthesis methods are used, then zeolite AFX can be obtained, but crystallization time is extended
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: uses quaternary ammonium salt as structure-directing agent, controls SiO2/Al2O3 ratio between 8-40, maintains R/SiO2 ratio between 0.05-0.50, and sets water content at 40-100 wt%. This coordinated parameter optimization reduces crystallization time to 1-10 days while maintaining high synthesis efficiency and product purity.
Solution Approach 2:
The quaternary ammonium salt performs preliminary structural organization by forming a template structure that pre-arranges the silicon and aluminum species in the correct configuration for AFX zeolite formation. This preliminary action accelerates the crystallization process by eliminating the need for extensive random nucleation and growth phases.
3Stress or pressure
If conventional synthesis methods are used, then zeolite AFX can be obtained, but high pressure reactors are required
Solution Approach 1:
The patent changes the pressure parameter by conducting synthesis at atmospheric pressure instead of high pressure. This is achieved by using a quaternary ammonium salt-based system with specific molar ratios that enable low-pressure crystallization, thereby simplifying the reactor design and eliminating the need for high-pressure equipment.
Solution Approach 2:
The patent replaces the mechanical high-pressure system with a chemical approach using quaternary ammonium salts as structure-directing agents. The chemical template directs crystallization at atmospheric pressure, substituting the need for high-pressure mechanical containment with a chemically-driven low-pressure process.
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
This method allows for the efficient synthesis of high-purity AFX zeolites at lower temperatures and pressures, reducing production time and energy costs while maintaining the desired structural properties, enabling their use as catalysts, adsorbents, or separation agents.
Implementation Method 1
the hydrothermal treatment under atmospheric pressure of said precursor gel obtained at the end of step i) at a temperature between 75°C and 95°C, limits included, for a period of between 40 and 100 hours, limits included, to obtain a crystallized solid phase of AFX structural type
Implementation Method 2
to obtain a crystallized solid phase of AFX structural type, called AFX zeolite
Data Source
Figure 1~2
AI summary
The invention relates to a process for synthesising a high-purity AFX zeolite, comprising at least the following steps: i) mixing, in an aqueous medium, at least one source of silicon (Si) in the oxide form SiO2, at least one source of aluminium (Al) in the oxide form Al2O3, a nitrogenous organic compound of the 1,6-bis(methylpiperidinium)hexane dihydroxide type, at least one source of at least one alkali metal selected from lithium, potassium or sodium, and mixing at least two of these metals until a homogeneous precursor gel is obtained, ii) hydothermally processing the precursor gel obtained a the end of step i) at a temperature between 75°C and 95°C, the limit values being included, for a time between 40 and 100 hours, the limit values being included, in order to obtain a crystallised solid phase of the AFX structural type, referred to as AFX zeolite. The invention also relates to the high-purity AFX zeolite obtained.