ATO Molecular Sieve Synthesis via Microwave Hydrothermal Heating
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Solution Overview
Problem
Conventional hydrothermal synthesis methods for crystallizing SAPO-31 and AlPO-31 molecular sieves are energy intensive and often result in impure phases, particularly the AEL framework, requiring seeding with AlPO-31 crystals and prolonged crystallization times, which limits the production of substantially pure ATO frameworks.
Innovation Solution
A microwave-hydrothermal synthesis process using a specific long chain quaternary salt of organic moity, such as Diquat-hydroxide, as a structure directing agent, which allows for crystallization at pH below 4.5 without mineral acids, reducing crystallization time and eliminating AEL framework impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional hydrothermal synthesis method is used, then crystallization of molecular sieves can be achieved, but prolonged crystallization time is required and AEL framework impurity forms
Solution Approach 1:
The invention changes the pH parameter of the reaction medium to below 4.5 (using organic acid instead of mineral acid) and uses microwave heating instead of conventional hydrothermal heating. These parameter changes enable rapid crystallization of pure ATO framework within 0.5-2 hours without forming AEL framework impurity, resolving the contradiction between purity and time.
Solution Approach 2:
The invention replaces conventional hydrothermal heating with microwave-assisted heating. This substitution provides rapid and uniform heating that accelerates the crystallization process significantly, enabling pure ATO framework to form within 0.5-2 hours instead of requiring prolonged heating time, thus resolving the time-purity contradiction.
2Manufacturing precision
If conventional hydrothermal approach is used, then molecular sieve crystallization can occur, but energy intensive conditions are required
Solution Approach 1:
The invention replaces conventional hydrothermal heating with microwave-assisted heating. Microwave heating provides rapid and efficient energy transfer that reduces the total energy consumption while maintaining high phase purity. The microwave method achieves pure ATO framework crystallization in 0.5-2 hours compared to prolonged conventional heating, resolving the energy-purity contradiction.
3Manufacturing precision
If seeding with AlPO-31 crystals is performed, then pure SAPO-31 can be obtained, but significant amounts of seed crystals must be added
Solution Approach 1:
The invention changes the reaction conditions by using organic acid to maintain pH below 4.5 and applying microwave heating. These parameter changes enable direct crystallization of pure ATO framework without requiring any seed crystals. The process produces pure phase within 0.5-2 hours, eliminating the need for seeding and resolving the purity-quantity contradiction.
4Manufacturing precision
If lower pH is used to prevent AEL framework formation, then impure phases still form due to metastable nature of zeolitic framework
Solution Approach 1:
The invention replaces conventional hydrothermal heating with microwave-assisted heating. The microwave energy provides rapid and uniform heating that overcomes the metastable nature of the zeolitic framework, enabling reliable crystallization of pure ATO phase even at low pH (<4.5). This resolves the contradiction between purity and crystallization reliability.
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 approach enables rapid and efficient synthesis of pure, highly crystalline ATO frameworks without the need for seeding, achieving faster crystallization and eliminating AEL framework impurities, thus improving the purity and efficiency of the molecular sieve production.
Implementation Method 1
a microwave-hydrothermal synthesis process
Implementation Method 2
crystallization of ATO framework
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a process for the synthesis of ATO molecular sieve framework comprising forming a reaction medium comprising of reactive sources Al2O3, P2O5 and /or silica and a templating agent and subjecting the reaction medium to microwave hydrothermal heating until crystals of ATO framework are formed. The templating agent used in the reaction medium is a long chain quaternary ammonium dihydroxide organic moiety having C5-C10 linear chain alkane, alkene or alkyl. The crystalline ATO type molecular sieve framework obtained by the process of the present invention is pure and completely free from commonly observed major impurity phase, namely AEL framework.