Small-Crystal SSZ-41 Synthesis with Zinc for Phase Purity
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Solution Overview
Problem
Existing synthesis methods for SSZ-41 molecular sieves face challenges in producing low silica-to-alumina molar ratio materials without significant impurity phases, particularly MTW framework type materials, which affect catalyst activity and selectivity.
Innovation Solution
A method for synthesizing zincoaluminosilicate molecular sieve SSZ-41 with a low silica-to-alumina molar ratio and small crystal size using a reaction mixture comprising FAU framework type zeolite, zinc, 1,1'-(1,4-butanediyl)bis[4-aza-1-azoniabicyclo[2.2.2]octane] dications, lithium, hydroxide ions, seeds, and water, while being free or essentially free of sodium, to achieve high phase purity and improved catalytic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional synthesis methods are used to produce low silica-to-alumina molar ratio SSZ-41, then catalyst activity and selectivity are improved, but significant impurity phases (particularly MTW framework type materials) are produced
Solution Approach 1:
The invention changes the chemical composition parameters of the reaction mixture by introducing zinc ions and using sodium-free conditions. This parameter change shifts the crystallization pathway to favor pure SSZ-41 phase formation while suppressing impurity phase formation, resolving the contradiction between achieving low silica-to-alumina ratio for catalytic activity and maintaining phase purity
Solution Approach 2:
Zinc ions act as an intermediary substance in the synthesis process. The zinc-containing reaction mixture mediates the crystallization process, enabling the formation of low silica-to-alumina ratio SSZ-41 with high phase purity by preventing the formation of MTW framework impurities while maintaining the desired catalytic properties
2Reliability
If aluminum concentration is increased to improve catalytic performance, then catalyst activity is enhanced, but crystallization is inhibited and impurity phases are formed
Solution Approach 1:
The invention changes the chemical environment parameters by adding zinc ions and eliminating sodium, which fundamentally alters the crystallization behavior. This allows high aluminum concentrations to be used without inhibition, as the zinc-modified system prevents the formation of impurity phases that would otherwise form at high aluminum levels
Solution Approach 2:
Zinc ions serve as a mediating agent that facilitates crystallization in high-aluminum systems. The zinc acts as a bridge that enables the crystallization process to proceed successfully even at high aluminum concentrations, preventing crystallization inhibition while maintaining ease of manufacture
3Reliability
If small crystal size is achieved to improve mass transfer and catalytic activity, then catalyst performance is enhanced, but synthesis control becomes more difficult
Solution Approach 1:
The invention uses parameter changes in the chemical composition (zinc addition, sodium removal) to control nucleation and crystal growth rates. This enables precise control over crystal size, producing uniformly small crystals with improved mass transfer properties while maintaining easy synthesis control through compositional adjustment
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 produces SSZ-41 with high phase purity and small crystal size, enhancing its activity and selectivity as an isomerization catalyst, achieving improved conversion and selectivity in organic compound reactions.
Implementation Method 1
subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the zincoaluminosilicate molecular sieve
Data Source
Figure 1
Figure 2(A)~2(B)
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AI summary
A method is disclosed for producing small crystal, high aluminum content zincoaluminosilicate crystalline materials having the SSZ-41 framework structure. The compositions made according to that method, as well as uses of the same, are also disclosed.