Small-Crystal SSZ-81 Zeolite for Faster Mass Transfer
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Solution Overview
Problem
Conventional SSZ-81 crystals are large, leading to slower diffusion and reduced mass transfer in organic conversion reactions, which affects reaction selectivity and conversion efficiency.
Innovation Solution
Synthesis of small crystal SSZ-81 zeolite using alumina-coated silica sols and structure directing agents like 1,5-bis(N-methylpiperidinium)pentane dications and 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications under controlled crystallization conditions to achieve a d50 crystal size of 250 nanometers or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional crystallization is used to prepare SSZ-81, then the crystal structure is well-formed, but the crystal size becomes large (about 500 nanometers), leading to slower diffusion and reduced mass transfer
Solution Approach 1:
The patent changes the chemical composition parameters of the reaction mixture by incorporating alumina-coated silica sol and adjusting the ratio of structure directing agents (1,5-bis(N-methylpiperidinium)pentane and 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane). These parameter changes result in the formation of small crystal SSZ-81 with d50 size of 250 nanometers or less, thereby improving diffusion rate while maintaining crystal structure stability
Solution Approach 2:
The patent uses a composite approach by combining alumina-coated silica sol with specific structure directing agents in the reaction mixture. This composite material system enables controlled crystallization that produces smaller crystals with improved mass transfer properties while preserving the distinctive X-ray diffraction pattern of SSZ-81
2Stability of the object's composition
If conventional crystallization is used to prepare SSZ-81, then the crystal structure is well-formed, but the mass transfer is reduced, affecting reaction selectivity and conversion
Solution Approach 1:
By modifying the reaction mixture composition with alumina-coated silica sol and optimizing structure directing agent ratios, the patent achieves smaller crystal size (d50 ≤ 250 nm) that enhances mass transfer and improves reaction conversion efficiency while maintaining the stable SSZ-81 crystal structure
Solution Approach 2:
The patent effectively segments the crystal growth process by controlling nucleation and growth conditions to produce numerous small crystals instead of fewer large crystals. This segmentation increases the total surface area and reduces diffusion paths, thereby improving mass transfer and reaction productivity
3Speed
If crystal size is reduced to enhance mass transfer, then diffusion improves, but the crystallization process becomes more difficult to control
Solution Approach 1:
The patent uses alumina-coated silica sol as an intermediary material that mediates the crystallization process. This intermediary provides a controlled environment for crystal growth, enabling the formation of small uniform crystals with d50 ≤ 250 nm while maintaining ease of manufacturing through standard crystallization procedures
Solution Approach 2:
The reaction mixture composition is designed to self-regulate the crystallization process, where the alumina-coated silica sol and structure directing agents work together to automatically control nucleation and growth rates, producing small crystals without requiring complex external control mechanisms
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 small crystal size enhances mass transfer and improves reaction pathways, increasing selectivity and conversion efficiency in organic conversion processes.
Implementation Method 1
subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the zeolite
Implementation Method 2
synthesis of small crystal SSZ-81 zeolite using alumina-coated silica sols and structure directing agents
Data Source
AI summary
A method is disclosed for producing small crystal forms of zeolite SSZ-81. The method includes forming a reaction mixture containing an alumina-coated silica sol, a source of an alkali metal, a structure directing agent containing 1,5-bis(N-methylpiperidinium)pentane dications and/or 1,5-bis(1-azonia-bicyclo[2.2.2]octane)pentane dications, a source of hydroxide ions, and water; and subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the zeolite. The compositions made according to that method, as well as the various uses of the compositions, are also disclosed.