Gas Separation Membrane Using Copolymer for CO2 Selectivity
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Solution Overview
Problem
Existing gas separation membranes face challenges in achieving high carbon dioxide selectivity and permeability, particularly when compared to methane, due to limitations in polymer materials used in the active layer.
Innovation Solution
A method for preparing a gas separation membrane involving a porous layer coated with a hydrophilic polymer solution and an active layer formed using a specific polymer represented by Chemical Formula 1, where the polymer is included in 1% to 5% by weight, enhancing carbon dioxide selectivity and permeability by optimizing viscosity and layer thickness through the use of nitromethane as a solvent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing polymer materials are used in the active layer, then the membrane structure is simple and easy to manufacture, but carbon dioxide selectivity and permeability are insufficient
Solution Approach 1:
The patent uses a composite polymer material comprising cellulose acetate and a specific copolymer (polymer represented by Chemical Formula 1). This composite approach combines the advantages of both materials: cellulose acetate provides good membrane formation and the copolymer enhances carbon dioxide selectivity and permeability. The copolymer content is optimized at 1-5% by weight to achieve the desired performance while maintaining manufacturability.
Solution Approach 2:
The patent optimizes the molecular weight of the copolymer (n=500-3,000 repeating units) and its content in the active layer (1-5% by weight). These parameter changes are critical to achieving high carbon dioxide selectivity (5-30 based on methane) and permeability. The specific parameter ranges were determined through systematic experimentation to balance performance and manufacturing feasibility.
2Reliability
If the active layer thickness is increased to improve selectivity, then carbon dioxide selectivity improves, but permeability decreases
Solution Approach 1:
The patent optimizes the active layer thickness to a specific range (0.5-5 μm) to balance selectivity and permeability. Within this thickness range, the membrane achieves carbon dioxide selectivity of 5-30 based on methane while maintaining permeability of 10-150 GPU. The optimized thickness ensures sufficient selectivity without excessive resistance to gas transport.
Solution Approach 2:
The composite polymer material enables high performance at reduced thickness. The copolymer component (1-5% by weight) enhances the gas separation properties, allowing the membrane to achieve high selectivity and permeability even at thin active layer thicknesses of 0.5-5 μm, thus resolving the trade-off between selectivity and permeability.
3Reliability
If polymer content in the active layer is increased to improve performance, then gas separation performance improves, but viscosity increases and coating becomes difficult
Solution Approach 1:
The patent optimizes the copolymer content to 1-5% by weight in the active layer, which provides sufficient gas separation performance without causing excessive viscosity increase. This optimized concentration range ensures the coating solution remains processable while achieving the desired performance enhancement.
Solution Approach 2:
The patent uses nitromethane as a solvent in the coating composition. Nitromethane serves as an intermediary that dissolves the polymer materials and adjusts the viscosity of the coating solution, making it suitable for coating processes. The solvent allows proper coating application while the polymer content remains within the optimal 1-5% range for performance.
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 carbon dioxide selectivity and permeability compared to existing membranes, particularly with acetylated methyl cellulose, achieving selectivity of 10 to 30 based on methane and permeability of 10 to 150 GPU, while maintaining durability and controlling active layer thickness effectively.
Implementation Method 1
a gas separation membrane, and is a membrane separating gases selectively from a gas mixture using a pore size and structural properties of the active layer
Implementation Method 2
forming a porous layer by coating a hydrophilic polymer solution on a porous substrate
Implementation Method 3
forming an active layer by coating a composition for forming an active layer including a polymer represented by the following Chemical Formula 1 on the porous layer
Data Source
Figure 1~2
AI summary
The present specification provides a method for preparing a gas separation membrane including forming a porous layer by coating a hydrophilic polymer solution on a porous substrate; and forming an active layer by coating a composition for forming an active layer including a polymer represented by Chemical Formula 1 on the porous layer, wherein the polymer represented by Chemical Formula 1 is included in 1% by weight to 5% by weight based on the composition for forming an active layer, and a gas separation membrane prepared using the same.