Carbon Molecular Sieve Membrane Oxygen Control
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Solution Overview
Problem
Current methods for producing carbon molecular sieve (CMS) membranes lack control over selectivity and permeability, primarily due to the unknown effects of the pyrolysis atmosphere, particularly the oxygen concentration, which hinders optimal gas separation performance.
Innovation Solution
Controlling the oxygen concentration in the pyrolysis atmosphere, with levels less than 40 ppm, to tune the gas separation properties of CMS membranes, allowing for optimized selectivity and permeability by varying the oxygen exposure during the pyrolysis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pyrolysis methods are used with uncontrolled atmosphere, then CMS membranes can be produced, but selectivity and permeability cannot be optimized
Solution Approach 1:
The patent applies parameter changes by systematically varying the oxygen concentration in the pyrolysis atmosphere (from vacuum to 21% oxygen) and pyrolysis temperature to optimize the selectivity and permeability of CMS membranes. This controlled variation of atmospheric parameters enables precise tuning of membrane properties for specific gas separation applications.
Solution Approach 2:
The patent employs inert atmosphere control during pyrolysis, using nitrogen or carbon dioxide atmospheres with controlled oxygen concentrations to prevent unwanted oxidation while enabling selective formation of carbon structures. This controlled inert environment allows precise manipulation of the pyrolysis process to achieve desired membrane performance.
2Productivity
If oxygen concentration in pyrolysis atmosphere is increased, then membrane permeability may improve, but selectivity deteriorates
Solution Approach 1:
The patent resolves this contradiction by independently optimizing both oxygen concentration and pyrolysis temperature parameters. By adjusting oxygen concentration from 0% to 21% and temperature accordingly, the patent achieves simultaneous optimization of both permeability and selectivity, demonstrating that these parameters can be tuned independently to achieve desired performance balances.
Solution Approach 2:
The patent applies dynamics by creating a dynamic optimization approach where oxygen concentration and temperature are varied systematically to achieve different performance targets. The process allows dynamic adjustment of atmospheric composition during pyrolysis to tailor membrane properties for specific separation requirements.
3Reliability
If pyrolysis temperature is increased to improve membrane stability, then separation performance may deteriorate
Solution Approach 1:
The patent resolves this contradiction by changing multiple parameters simultaneously - specifically, lowering pyrolysis temperature while adjusting oxygen concentration in the atmosphere. This combined parameter adjustment maintains membrane stability through controlled carbonization while preserving separation performance by preventing excessive graphitization that would reduce selectivity.
Solution Approach 2:
The patent applies composite material principles by creating carbon molecular sieve membranes with controlled microstructures that combine stability and separation performance. The controlled pyrolysis atmosphere creates a composite carbon structure with specific pore sizes and distributions that simultaneously provide thermal stability and high gas separation selectivity.
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 approach enables the production of CMS membranes with tailored CO2/CH4 selectivity and permeability, enhancing their separation performance for applications such as natural gas processing by reducing acid gas concentrations and improving gas separation efficiency.
Implementation Method 1
heating the precursor in a chamber to at least a temperature at which pyrolysis byproducts are evolved
Implementation Method 2
Gas transport through such membranes is commonly modeled by the sorption-diffusion mechanism. Specifically, gas molecules sorb into the membrane at the upstream, and finally desorb from the membrane at the downstream
Implementation Method 3
Gas transport through such membranes is commonly modeled by the sorption-diffusion mechanism
Data Source
AI summary
The invention concerns carbon molecular sieve membranes (“CMS membranes”), and more particularly the use of such membranes in gas separation. In particular, the present disclosure concerns an advantageous method for producing CMS membranes with desired selectivity and permeability properties. By controlling and selecting the oxygen concentration in the pyrolysis atmosphere used to produce CMS membranes, membrane selectivity and permeability can be adjusted. Additionally, oxygen concentration can be used in conjunction with pyrolysis temperature to further produce tuned or optimized CMS membranes.