Hybrid Polyimide-POSS Membranes for High-Temperature Gas Separation
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Solution Overview
Problem
Existing gas separation membranes fail to maintain high permselectivity and selectivity at elevated temperatures and pressures due to swelling and softening, limiting their effectiveness in severe operational conditions.
Innovation Solution
Development of hybrid organic-inorganic polyimide membranes with uniformly distributed polyhedral oligomeric silsesquioxane (POSS) units, which form a homogeneous network structure, enhancing the membranes' stability and gas separation properties under extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimide membranes are used for gas separation at elevated temperatures, then gas separation function is provided, but permselectivity decreases due to swelling and chain mobility
Solution Approach 1:
The patent creates a hybrid organic-inorganic membrane by integrating POSS (polyhedral oligomeric silsesquoxane) units into the polyimide matrix. This composite structure combines the flexibility and processability of organic polymers with the thermal stability and rigidity of inorganic POSS cages, preventing chain mobility and swelling at elevated temperatures while maintaining gas separation functionality.
Solution Approach 2:
The POSS units are distributed throughout the polymer network at specific locations, creating localized rigid regions that restrict chain mobility. These locally reinforced zones prevent bulk swelling and maintain permselectivity without compromising the overall membrane flexibility and gas transport pathways.
2Stability of the object's composition
If ceramic membranes are used for high-temperature gas separation, then permselectivity and thermal stability are improved, but large-scale processing and defect-free thin film formation become difficult
Solution Approach 1:
The patent changes the material state from purely inorganic ceramic to a hybrid organic-inorganic system. This parameter change enables the membrane to be processed using solution-based techniques at lower temperatures, allowing easy formation of defect-free thin films, while the inorganic POSS units provide the thermal stability characteristic of ceramic membranes.
3Stability of the object's composition
If polyimide membranes are crosslinked to reduce chain mobility, then selectivity is improved, but membrane formation complexity and processing difficulty increase
Solution Approach 1:
The POSS units with reactive amino groups are pre-incorporated into the polyimide network during membrane formation. This preliminary inclusion of crosslinking functionality allows the crosslinking reaction to occur in-situ during or after membrane fabrication, eliminating the need for separate complex crosslinking process steps and simplifying overall manufacturing.
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 membranes exhibit ultrathin structures with effective gas separating properties at temperatures up to 300°C and pressures up to 100 bar, maintaining high selectivity and integrity through exceptional crosslinking, surpassing the performance of traditional polyimide membranes.
Implementation Method 1
Highly crosslinked hybrid polyimide-silsesquioxane membranes
Implementation Method 2
show excellent gas separation properties at elevated temperatures based on molecular size exclusion
Data Source
Figure 1a~1d
AI summary
Gaseous molecules, such as H2, CO2and CH4,can be separated using a hybrid organic-inorganic polyimide network membrane, wherein the polyimide contains bis-imide units of formula 1 (formula 1), wherein A represents an organic moiety having 2-22 carbon atoms; or corresponding tris-imide groups, wherein a nitrogen atom of two or more of said bis-imide units is linked to a group Q of a polyhedral oligomeric silsesquioxane (POSS) group of formula 3 QmR(2n-m)Si2nO3n.x H2O 3 wherein Q is CpHq bound to a silicon atom, R is hydrogen, hydroxy or C1-C4 alkyl, alkoxy, hydroxyalkyl,aminoalkyl or ammonioalkyl, bound to a silicon atom, m is from 2 up to 2n, n is from 2 up to 6, p = 1 to 6; q = 2(p –r) with r = 0, 1, 2 < p; and x is from 0 to 2n-1.