SSZ-75 Molecular Sieve Synthesis via Organic Structure Directing Agent
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Solution Overview
Problem
There is a need for new crystalline molecular sieves with desirable properties for gas separation, hydrocarbon, and chemical conversions, as existing molecular sieves do not offer enhanced selectivities in these processes due to limited silica/alumina mole ratios and unique internal pore architectures.
Innovation Solution
A crystalline molecular sieve, SSZ-75, is developed with a framework topology of STI, utilizing a tetramethylene-1,4-bis-(N-methylpyrrolidinium) dication as a structure directing agent, achieving a silica/alumina mole ratio of at least 15, and a method for its preparation involving sources of silicon oxide, aluminum oxide, and fluoride ions under crystallization conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing molecular sieves with limited silica/alumina mole ratios are used, then manufacturing is simpler, but selectivity and catalytic properties are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters by achieving a silica alumina ratio of at least 15:1 (significantly higher than conventional molecular sieves), which fundamentally alters the material properties to provide enhanced selectivity and catalytic performance while maintaining structural stability
Solution Approach 2:
The patent introduces a specific organic structure directing agent (OSA) as an intermediary substance that mediates the formation of the high-silica molecular sieve structure, enabling the achievement of silica alumina ratios ≥15:1 by controlling the crystallization process and stabilizing the desired framework topology
2Productivity
If conventional molecular sieves are used, then the process is simpler, but gas separation and hydrocarbon conversion performance is limited
Solution Approach 1:
The patent creates local quality differences within the molecular sieve structure by forming specific pore architectures with distinct silica-rich regions that provide localized hydrophobicity and selective adsorption sites, enhancing gas separation performance for applications like isobutane/n-butane separation
Solution Approach 2:
The patent creates a composite structure combining inorganic silica-alumina framework with organic structure directing agent residues or modifications, resulting in a hybrid material that exhibits both the structural stability of inorganic zeolites and the tunable selectivity of organic components
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
SSZ-75 exhibits unique X-ray diffraction patterns and enhanced properties, such as high n-hexane adsorption capacity and hydrophobicity, making it suitable for gas separations, catalytic conversions, and pollution control, while maintaining diffusion control and high pore volume.
Implementation Method 1
contacting under crystallization conditions a source(s) of (1) silicon oxide, (2) a source(s) of aluminum oxide
Implementation Method 2
utilizing a tetramethylene-1,4-bis-(N-methylpyrrolidinium) dication as a structure directing agent
Implementation Method 3
high n-hexane adsorption capacity
Implementation Method 4
enhanced properties, such as high n-hexane adsorption capacity and hydrophobicity
Implementation Method 5
exhibits unique X-ray diffraction patterns
Implementation Method 6
the SSZ-75 molecular sieve has, after calcination, the X-ray diffraction lines of Table II
Data Source
AI summary
The present invention relates to new crystalline molecular sieve SSZ-75 having STI topology prepared using a tetramethylene-1,4-bis-(N-methylpyrrolidinium) dication as a structure-directing agent, and methods for synthesizing SSZ-75.