CHA Molecular Sieve Synthesis Using Diazabicyclooctane Agents
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Solution Overview
Problem
The synthesis of CHA-type molecular sieves using existing structure directing agents (SDAs) is complex and costly, limiting their usefulness in commercial processes.
Innovation Solution
The use of cationic 1,4-diazabicyclo[2.2.2]octane-based structure directing agents in conjunction with cationic cyclic nitrogen-containing SDAs to prepare CHA-type molecular sieves, reducing the reliance on costly SDAs through a process involving specific oxide sources, hydroxide ions, and controlled crystallization conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex and costly structure directing agents (such as N-alkyl-3-quinuclidinol cation, N,N,N-trialkyl-1-adamantammonium cation) are used to prepare CHA-type molecular sieves, then the crystal structure and pore structure are achieved, but the synthesis cost increases significantly
Solution Approach 1:
The patent replaces expensive, complex structure directing agents with cheaper alternatives including cationic 1,4-diazabicyclo[2.2.2]octane-based SDAs, cyclic ammonium cations, and even simple inorganic cations like Na+, K+, Ca2+, and Sr2+. These cheaper SDAs effectively direct the formation of CHA-type crystal structures without requiring the complex and costly adamantane-based or quinuclidine-based agents previously necessary
Solution Approach 2:
The patent changes the chemical parameters of the structure directing agents by using cations with different structures, sizes, and charge densities. Specifically, it employs cationic 1,4-diazabicyclo[2.2.2]octane-based SDAs and cyclic ammonium cations that have different molecular geometries and electronic properties compared to traditional SDAs, yet still achieve effective crystal structure direction for CHA-type molecular sieves
2Reliability
If traditional cationic SDAs are used for CHA-type molecular sieve synthesis, then the desired pore structure is obtained, but the process complexity increases
Solution Approach 1:
The patent simplifies the synthesis process by replacing complex organic structure directing agents with simpler alternatives. The use of cationic 1,4-diazabicyclo[2.2.2]octane-based SDAs, cyclic ammonium cations, and simple inorganic cations reduces the complexity of the synthesis process while maintaining the ability to form the desired CHA-type pore structure
Solution Approach 2:
The patent changes the structural parameters of the SDAs used in synthesis. By employing cations with simpler molecular structures, smaller molecular weights, and different charge distributions, the patent reduces process complexity while still achieving effective template direction for CHA-type crystal formation
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 allows for the cost-effective synthesis of CHA-type molecular sieves with targeted compositions and structures, as demonstrated by X-ray diffraction patterns, while maintaining the integrity of the crystal lattice structure.
Implementation Method 1
maintaining the reaction mixture under conditions sufficient to form crystals of the CHA-type molecular sieve
Data Source
AI summary
The present invention is directed to a process for preparing CHA-type molecular sieves using at least one cationic 1,4-diazabicyclo[2.2.2]octane-based structure directing agent in conjunction with at least one cationic cyclic nitrogen-containing structure directing agent.