CIT-14 Germanosilicate via Fluoride-Free Inverse Sigma Transformation
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Solution Overview
Problem
Existing methods for synthesizing new zeolite frameworks face challenges in predicting outcomes due to the complexity of hydrothermal synthesis processes, and there is a need for larger pore structures capable of handling larger feed molecules in industrial applications.
Innovation Solution
A fluoride-free hydroxide route is used to synthesize CIT-13 germanosilicates, which undergo an inverse sigma transformation to form CIT-14, a mesopore-free material with 8- and 12-membered ring channels, characterized by specific XRD patterns and Si:Ge ratios, allowing for faster transformation and unique germanium siting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional hydrothermal synthesis methods are used to prepare new zeolite frameworks, then new crystalline phases can be discovered, but the complexity of the synthesis process makes it difficult to predict outcomes
Solution Approach 1:
The patent applies preliminary action by using pre-formed germanium-containing building units (d4r units) as templates or seeds that direct the formation of the CIT-14 framework. The germanium sites are pre-positioned in specific configurations that guide the assembly of silicate layers and determine the final crystal structure, thereby simplifying the prediction and control of synthesis outcomes.
Solution Approach 2:
The patent uses germanium-containing intermediate structures (such as d4r units with specific Ge-O-Ge connectivities) as intermediaries that facilitate the formation of the final CIT-14 framework. These intermediaries act as mediators between the starting materials and the target structure, enabling controlled transformation through defined chemical steps rather than complex hydrothermal processes.
2Productivity
If fluoride-based methods are used to synthesize germanosilicates, then certain structural transformations can be achieved, but the transformation process is slower and less efficient
Solution Approach 1:
The patent applies parameter changes by modifying the chemical environment from fluoride-based to hydroxide-based conditions, and by adjusting the pH, temperature, and composition ratios. These parameter changes enable faster and more efficient transformations, as demonstrated by the accelerated formation of CIT-14 from CIT-13/OH under optimized hydrothermal conditions compared to conventional fluoride methods.
Solution Approach 2:
The patent utilizes phase transitions in the hydrothermal system, where the transformation from CIT-13/OH to CIT-14 occurs through controlled structural reorganization and phase changes. The hydrothermal conditions promote rapid nucleation and growth of the new phase, enhancing the transformation rate and synthesis efficiency.
3Speed
If inverse sigma transformation is applied to convert CIT-13/OH to CIT-14, then faster conversion is achieved, but complete delamination may be impeded by Si-O-Si connectivity
Solution Approach 1:
The patent applies the taking out principle by selectively removing or breaking the Si-O-Si connectivity that impedes delamination. Through controlled acid treatment or other selective etching methods, the Si-O-Si bonds are targeted and removed, enabling complete delamination of the cfi-type layers and formation of the desired CIT-14 structure with high precision.
Solution Approach 2:
The patent uses an intermediary substance (such as acid or a chemical modifier) that facilitates the breaking of Si-O-Si bonds during the inverse sigma transformation. This intermediary acts as a mediator that enables complete delamination by temporarily weakening or breaking the problematic connectivity, allowing the transformation to proceed to completion.
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 CIT-14/IST germanosilicates with distinct structural and catalytic properties, enabling faster conversion and enhanced catalytic performance compared to fluoride-containing methods, suitable for industrial applications.
Implementation Method 1
Synthetic molecular sieves are typically prepared using hydrothermal synthesis that involves the use of inorganic (Na+, K+, etc.) and organic structure-directing agents (OSDAs), mineralizing agents (OH− or F−), heteroatoms (in addition to Si element such as Al, B, Ge, Ti, Sn, etc.), etc.
Implementation Method 2
The present work is aimed at addressing the deficiencies in the art in this area. The present inventors previously reported the similarity between *CTH and UTL, and disclosed two novel frameworks, CIT-14 and CIT-15, having 2D 12/8MR and 1D 10MR channel system, respectively, prepared based on the ADOR transformation.
Implementation Method 3
These transformations are schematically illustrated in FIGS. 1(A) and 1(B), respectively. CIT-13 is composed of Si-rich cfi-layers bridged by two-dimensional arrays of Ge-rich d4r units.
Implementation Method 4
One goal toward finding new materials has been the hope that increasingly large pores that retain some catalytic properties in their interior surfaces can be capable of handling larger feed molecules in the oil upgrade arena.
Data Source
AI summary
The present disclosure is directed to large-pore germanosilicate compositions designated CIT-13/OH and CIT-14/IST, the two large-pore germanosilicate each having a three-dimensional framework with 10- and 14-membered ring channels and 8- and 12-membered ring channels, respectively. The disclosure also sets forth methods for converting the former to the latter under conditions consistent with an inverse sigma transformation. Uses of the large-pore germanosilicate compositions are also disclosed.