CMS Membranes via Nanoparticle-Stabilized Pyrolysis
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Solution Overview
Problem
Existing methods for producing carbon molecular sieve (CMS) membranes suffer from substructure collapse during pyrolysis, leading to reduced permeance and selectivity, and require additional post-treatment steps that increase cost and complexity.
Innovation Solution
A dual-layer hollow fiber precursor fiber membrane with a nano-particle-filler containing core layer and a sheath layer is extruded and pyrolysed, eliminating the need for post-treatment steps like VTMS soaking and simplifying the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pyrolysis is performed at temperatures above the polymer glass transition temperature to form CMS membranes, then carbon formation is achieved, but substructure collapse occurs leading to reduced permeance and productivity
Solution Approach 1:
The patent applies preliminary action by incorporating nanoparticle fillers into the precursor fiber membrane before pyrolysis. These fillers are pre-positioned in the porous core layer to act as structural supports during the subsequent high-temperature pyrolysis process, preventing substructure collapse and maintaining permeance without requiring post-treatment steps
Solution Approach 2:
The patent uses composite materials by combining nanoparticle fillers with the polymer precursor matrix. This composite structure provides both the functional properties of the polymer and the structural stability of the nanoparticle framework, preventing collapse during pyrolysis while maintaining the asymmetric fiber architecture needed for high productivity
2Reliability
If chemical modifying agents like VTMS are used to stabilize precursor fibers before pyrolysis, then substructure collapse is prevented, but manufacturing complexity and cost increase due to additional post-treatment steps
Solution Approach 1:
The patent extracts and eliminates the need for chemical modifying agents like VTMS by incorporating nanoparticle fillers directly into the precursor fiber membrane during the spinning process. This removes the complex post-treatment stabilization step while achieving the same substructure stability through the physical presence of nanoparticle supports
Solution Approach 2:
The nanoparticle fillers provide self-service structural support during pyrolysis without requiring external chemical stabilizing agents. The nanoparticle framework automatically maintains substructure integrity during the thermal process, eliminating the need for additional stabilizing treatments and simplifying the overall fabrication process
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 method effectively suppresses substructure collapse, resulting in CMS membranes with improved permeance and selectivity, such as CO2/CH4 selectivity of 134.2 and CO2 permeance of 71.1 GPU at 35°C, while reducing manufacturing complexity and cost.
Implementation Method 1
Pyrolysis of appropriate precursor fibers at temperatures above the glass transition temperature (Tg) of the polymer creates a CMS fiber
Implementation Method 2
The chemical modifying agent stabilizes the precursor fiber prior to pyrolysis to prevent collapse of the substructure morphology between the polymer Tg and the point of actual carbon formation
Implementation Method 3
Permeance measures the pressure-normalized flux of a given penetrant and provides a measure of membrane productivity. Selectivity measures the comparative ability of different gases to permeate through a membrane
Data Source
AI summary
In a method of fabricating high performance CMS membranes, in which a dual-layer hollow fiber precursor fiber membrane that contains a nano-particle-filler containing core layer is extruded, a sheath layer is co-extruded with the core layer so that at least a portion of the core layer is surrounded by the sheath layer. The nano-particle filler is defect sealed. The dual-layer hollow fiber precursor fiber and the sheath layer are pyrolysed. A CMS membrane includes a core layer, a sheath layer surrounding at least a portion of the core layer and a plurality of nanoparticles disposed in the core layer.