Inorganic Membrane Pore Size Modification via Low-Temperature CVI
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Solution Overview
Problem
Current methods face challenges in producing large areas of defect-free microporous inorganic membranes with pore sizes less than 2 nm, essential for industrial gas separation applications, due to high defect formation during preparation and the inability to operate at low temperatures, which affects selectivity and performance.
Innovation Solution
A low-temperature Chemical Vapor Infiltration (CVI) method using tetramethyl orthosilicate and oxygen, or air, to reduce pore size and repair defects in microporous membranes, allowing for the adjustment of process parameters on the feed side, enabling effective sealing and in situ repair without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sol-gel method is used to prepare microporous membranes, then the process is simple and easy to manufacture, but defect formation probability increases and pore size control below 2 nm becomes difficult
Solution Approach 1:
The patent changes the fundamental preparation parameter from sol-gel chemistry to chemical vapor deposition (CVD) physics-chemistry process. This enables precise pore size control below 2 nm through controlled vapor-phase reactions, eliminating the defect formation issues inherent in sol-gel methods while maintaining manufacturing feasibility through a systematic process approach.
Solution Approach 2:
The patent replaces the chemical sol-gel system with a vapor-phase deposition system. By using CVD technology, the process transitions from liquid-phase chemical reactions to gas-phase deposition, enabling better control over pore structure and eliminating defects associated with the sol-gel method.
2Temperature
If high temperatures are used for membrane operation, then thermal stability is improved, but polymeric membranes cannot be used and selectivity decreases
Solution Approach 1:
The patent creates a composite membrane structure combining a macroporous support (providing mechanical strength and thermal stability for high-temperature operation) with a microporous top layer (providing selective separation). This composite approach allows the membrane to operate at high temperatures while maintaining the selectivity of the microporous layer.
3Area of stationary object
If large membrane areas are produced, then industrial scale applications are enabled, but defect formation increases
Solution Approach 1:
The patent employs a two-layer membrane structure that segments the functional requirements: the macroporous support layer provides mechanical strength and enables large-area fabrication, while the microporous top layer provides selective separation. This segmentation allows large membrane areas to be produced without compromising the defect-free nature of the selective layer, as the top layer can be applied uniformly over the entire support area through CVD.
4Manufacturing precision
If pore size is reduced below 2 nm for hydrogen separation, then selectivity improves, but defect formation probability increases and consistent production becomes difficult
Solution Approach 1:
The patent replaces the sol-gel chemical system with a vapor-phase deposition system to achieve precise pore size control below 2 nm. The CVD process enables atomic-level control over the microporous layer formation, ensuring consistent pore size and eliminating defects that plague sol-gel methods at this scale.
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 achieves significant pore size reduction and defect repair, enhancing membrane selectivity and performance, with permeance increasing exponentially with temperature and selectivity improvement, demonstrating dominant activated diffusion, and maintaining stability in water vapors, achieving high purity gas separation and recovery.
Implementation Method 1
A low-temperature Chemical Vapor Infiltration (CVI) method using tetramethyl orthosilicate and oxygen, or air, to reduce pore size and repair defects in microporous membranes
Implementation Method 2
permeance increasing exponentially with temperature and selectivity improvement, demonstrating dominant activated diffusion
Data Source
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AI summary
The invention refers to a method which can be used for pore size reduction, defect repair and in general for improving of the separation properties of microporous and nanoporous membranes. The present chemical vapor infiltration method can be applied at relatively low temperatures (200-300 °C), where it is feasible to use current available sealing technologies. By using this method a microporous membrane, which contains defects and, therefore, it has a low selectivity, can be modified in a controllable way turn to a purely microporous and/or nanoporous membrane of high selectivity. The microporous and nanoporous membranes without defects and with pore sizes less than 1 nm can find important industrial applications, as it is described in the present patent application. These include many gas separation processes, eg H2 recovery and gas pollutant cleaning, pervaporation and nanofiltration processes, as well as in membrane reactors for conversion enhancement in thermodynamically limited reactions with simultaneous separation of a reaction product.