SSZ-98 Molecular Sieve Synthesis via Dication Templating
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Solution Overview
Problem
Current methods for synthesizing ERI framework type molecular sieves lack control over silica-to-alumina ratio and crystal morphology, which are crucial for their applications in catalysis and gas separations.
Innovation Solution
A method involving a N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane dication as a structure directing agent, along with optional 18-crown-6, is used to prepare crystalline molecular sieve SSZ-98, allowing for controlled silica-to-alumina ratios and specific crystal morphologies, such as rod-like or plate-like, through precise crystallization conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to synthesize ERI framework type molecular sieves, then synthesis can be achieved, but control over silica-to-alumina ratio and crystal morphology is lacking
Solution Approach 1:
The patent applies parameter changes by systematically varying the silica-to-alumina ratio, temperature, and crystallization time to achieve precise control over molecular sieve composition and crystal morphology. Different ratios (e.g., 2.5:1, 5:1, 10:1) produce distinct rod-like or plate-like structures, demonstrating how parameter optimization resolves the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The patent uses an organic structure-directing agent (OSDA), specifically tetrapropylammonium hydroxide, as an intermediary to guide crystal formation. This mediator enables precise control over crystal morphology and silica-to-alumina ratio without requiring complex synthesis equipment, thus achieving high manufacturing precision while maintaining relatively simple synthesis procedures.
2Reliability
If ERI framework type molecular sieves are synthesized, then catalytic activity is achieved, but intergrowth with OFF framework type reduces performance
Solution Approach 1:
The patent achieves local quality by creating homogeneous ERI framework regions through optimized synthesis conditions, eliminating the heterogeneous intergrowth with OFF framework type that plagues conventional methods. The use of specific silica-to-alumina ratios and structure-directing agents ensures uniform crystal structure throughout, enhancing catalytic reliability by removing the harmful intergrowth effect.
3Reliability
If higher silica-to-alumina ratio is achieved, then catalytic selectivity improves, but synthesis control becomes more difficult
Solution Approach 1:
The patent employs an organic structure-directing agent as an intermediary to facilitate the synthesis of high silica-to-alumina ratio molecular sieves. This mediator stabilizes the formation process, making it possible to achieve high ratios (up to 10:1 or higher) while maintaining precise synthesis control, thus resolving the contradiction between improved catalytic selectivity and synthesis difficulty.
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 method enables the production of SSZ-98 with consistent X-ray diffraction patterns and controlled morphology, enhancing its performance as an adsorbent and catalyst for applications like methanol-to-olefins conversion and nitrogen oxides reduction.
Implementation Method 1
A method involving a N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane dication as a structure directing agent, along with optional 18-crown-6, is used to prepare crystalline molecular sieve SSZ-98, allowing for controlled silica-to-alumina ratios and specific crystal morphologies
Implementation Method 2
Molecular sieves are a commercially important class of crystalline materials. They have distinct crystal structures with ordered pore structures which are demonstrated by distinct X-ray diffraction patterns. The crystal structure defines cavities and pores which are characteristic of the different species.
Data Source
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AI summary
A new crystalline molecular sieve designated SSZ-98 is disclosed. SSZ-98 has the ERI framework type and is synthesized using a N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane dication as a structure directing agent.