Hollow Fiber CMS Membrane Tensile Force Pyrolysis
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Solution Overview
Problem
Current methods for producing hollow fiber carbon molecular sieve (CMS) membranes do not effectively separate gas molecules with similar sizes, such as propylene from propane, due to limitations in selectivity and permeance characteristics.
Innovation Solution
Applying a tensile force along the length of a hollow polymer fiber during pyrolysis to form a hollow fiber CMS membrane, using polymers like cellulosic, polyvinylidene chloride, or polyimides, improves the separation performance by enhancing the selectivity and permeance of the membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pyrolysis methods are used without applied tensile force, then the manufacturing process is simple, but the selectivity for separating similar-sized gas molecules is insufficient
Solution Approach 1:
A tensile force is applied to the hollow polymer fiber during pyrolysis before and during the formation of the CMS membrane structure. This preliminary mechanical action modifies the pore structure development during carbonization, creating more uniform and controllable pore sizes that enhance selectivity for separating similar-sized gas molecules like propylene and propane.
Solution Approach 2:
The application of tensile force during pyrolysis changes the physical parameters of the fiber (stress state, dimensional stability) which in turn affects the chemical transformation process. This parameter change leads to improved selectivity by controlling the pore size distribution and membrane density during the phase transition from polymer to carbon structure.
2Productivity
If conventional pyrolysis methods are used without applied tensile force, then the manufacturing process is simple, but the permeance characteristics are insufficient
Solution Approach 1:
The tensile force applied during pyrolysis preliminarily structures the forming CMS membrane, creating optimized pore pathways that enhance gas permeance. This mechanical pre-structuring during synthesis ensures better mass transport characteristics without requiring additional post-processing steps.
Solution Approach 2:
By changing the stress state parameter during pyrolysis through applied tensile force, the membrane's permeance is improved. The mechanical stress influences the pore formation and connectivity during carbonization, resulting in enhanced gas transport properties while maintaining selectivity.
3Manufacturing precision
If higher pyrolysis temperature is used to improve separation performance, then the selectivity may improve, but the membrane structure stability and hollow fiber integrity deteriorate
Solution Approach 1:
The applied tensile force acts as a counterbalancing mechanical constraint that opposes the thermal shrinkage and structural collapse tendencies during high-temperature pyrolysis. This mechanical support stabilizes the hollow fiber structure and membrane morphology, preventing degradation while allowing the temperature to be raised for improved separation performance.
Solution Approach 2:
The tensile force modifies the thermal-mechanical parameters during pyrolysis, creating a stable stress state that allows higher temperatures to be used without compromising structural integrity. This parameter control enables improved separation performance while maintaining membrane stability through coupled thermo-mechanical processing.
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 significantly improves the ability to separate difficult-to-separate gas molecules by increasing the selectivity and permeance of the CMS membrane, making it suitable for separating gases like propylene from propane and other similar molecular size pairs.
Implementation Method 1
heating the hollow polymer fiber to a carbonization temperature in an atmosphere that is non-oxidizing to form a hollow fiber carbon molecular sieve
Implementation Method 2
Gas transport through such membranes is commonly modeled by the sorption-diffusion mechanism
Implementation Method 3
hollow fiber carbon molecular sieve (CMS) membrane for use in gas separation
Data Source
AI summary
A method of making a hollow fiber carbon molecular sieve is comprised of heating a hollow polymer fiber to a carbonization temperature in an atmosphere that is non-oxidizing to form a hollow fiber carbon molecular sieve, wherein during at least a portion of the heating a tensile force is applied to the hollow polymer fiber. The method may improve the separation of gases similar in size such a propylene from propane.