Crystalline Aluminosilicate Synthesis via Charge Density Matching
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Solution Overview
Problem
The challenge lies in synthesizing new zeolites using commercially available organoammonium structure directing agents (SDAs) at low Si/Al ratios, where the charge density mismatch between the SDA and the aluminosilicate framework hinders crystallization, and existing methods struggle to induce crystallization effectively.
Innovation Solution
A process involving the formation of a reactive aluminosilicate reaction mixture with a charge density mismatch template, followed by the addition of a crystallization-inducing templating agent, such as organic cations or alkali/alkaline earth metals, to facilitate cooperative interaction and induce crystallization of zeolites or layered aluminosilicates at controlled temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If commercially available organoammonium SDAs are used at low Si/Al ratios, then cost is reduced and availability is improved, but charge density mismatch prevents crystallization
Solution Approach 1:
The patent introduces a second templating agent as an intermediary substance that mediates between the low charge density organoammonium SDA and the high charge density aluminosilicate framework. This second agent acts as a bridge to enable charge density matching and facilitate crystallization of the zeolite structure.
Solution Approach 2:
The patent changes the charge density parameter of the templating system by combining two different templating agents with complementary charge densities. This parameter adjustment allows the system to overcome the charge density mismatch that would otherwise prevent crystallization at low Si/Al ratios.
2Reliability
If high Si/Al ratios are used with low charge density SDAs, then charge density mismatch is reduced, but template cooperation becomes less effective
Solution Approach 1:
The patent optimizes the Si/Al ratio parameter to a specific range (4-20) that balances charge density matching with template cooperation efficiency. This parameter optimization ensures both adequate charge density matching and effective cooperative templating.
Solution Approach 2:
The patent uses two different templating agents that can be incorporated into the zeolite structure, with at least one being incorporated at significant levels. This copying approach allows multiple template structures to contribute to the final zeolite framework.
3Ease of manufacture
If multiple templates are used to form a single structure, then commercial SDA availability is utilized, but each template is present in large excess relative to framework charge
Solution Approach 1:
The patent carefully controls the Si/Al ratio parameter to ensure that the total framework charge is sufficient to balance both templating agents. By maintaining Si/Al ratios between 4-20, the system achieves adequate framework charge to accommodate multiple templates without excessive template-to-charge ratios.
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 enables the synthesis of crystalline aluminosilicate compositions, including microporous zeolites and layered aluminosilicates, by overcoming the charge density mismatch and achieving crystallization, thereby expanding the range of possible zeolite structures and improving synthesis efficiency.
Implementation Method 1
reacting the resultant mixture at a temperature and for a time to crystallize the aluminosilicate composition
Data Source
AI summary
A process for preparing crystalline alumino-silicate compositions has been developed. The process involves preparing a charge density mismatch reaction mixture comprising sources of aluminum, silicon, optionally an E metal and at least one charge density mismatch (CDM) template. The CDM template is an organic nitrogen containing template, in the hydroxide form, e.g. tetraethylammonium hydroxide and is characterized in that it is incapable of inducing crystallization. To this mixture there is added a solution comprising a second templating agent termed a crystallization template (CT). The CT can be an organic template different from the CDM template, an alkali metal, an alkaline earth metal and mixtures thereof.