Asymmetric Polyphenylene Ether Membrane for Gas Separation
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Solution Overview
Problem
Existing gas separation membranes face challenges in achieving high selectivity without increasing skin thickness, while also maintaining high permeation flux and long service life, especially under harsh conditions such as high temperatures and corrosive gases.
Innovation Solution
The development of asymmetric membranes with a substantially non-porous surface layer using a poly(phenylene ether) copolymer, dissolved in a solvent mixture comprising a water-miscible polar aprotic solvent and a polar solvent with two to eight carbon atoms, which is phase-inverted to form a selectively semi-permeable skin without increasing skin thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If skin thickness is increased to improve selectivity, then separation factor improves, but permeation flux decreases
Solution Approach 1:
The membrane structure is designed with different properties in different regions: the skin layer has high density and low porosity for selectivity, while the support layer has high porosity for flux. This local differentiation allows the skin to be thin (maintaining flux) while still providing high selectivity through its optimized molecular structure and composition rather than thickness.
Solution Approach 2:
The invention uses composite polymer materials with specific compositions (e.g., polyethersulfone, polysulfone, polyphenylene ether combined with specific monomers) that inherently provide high selectivity through their molecular structure and gas transport properties, rather than relying on increased thickness. The composite structure enables achieving both high selectivity and high flux simultaneously.
2Manufacturing precision
If skin thickness is increased to improve selectivity, then separation factor improves, but membrane area required increases
Solution Approach 1:
The skin layer is designed with optimized local properties including specific polymer composition, crosslinking density, and free volume distribution that enable high selectivity at thin thickness. This local optimization allows achieving the required separation performance with minimal skin thickness, thereby reducing the total membrane area needed.
Solution Approach 2:
The invention changes key parameters of the skin layer such as polymer composition ratios, molecular weight distribution, crosslinking density, and operating temperature/pressure conditions to achieve high selectivity at thin thickness. By optimizing these parameters rather than increasing thickness, the membrane area requirement is minimized.
3Adaptability or versatility
If membrane is used under harsh conditions (high temperature, corrosive gases), then operational flexibility improves, but service life decreases
Solution Approach 1:
The invention employs composite polymer materials with enhanced chemical resistance and thermal stability, such as polyethersulfone and polysulfone combinations, that maintain structural integrity and separation performance under harsh conditions including high temperatures and exposure to corrosive gases like H2S and CO2, thereby extending service life.
Solution Approach 2:
The membrane structure is optimized with controlled crosslinking density, specific polymer composition ratios, and molecular weight distribution that enhance mechanical strength and chemical resistance at elevated temperatures. These parameter optimizations allow the membrane to maintain its separation properties and structural integrity under harsh operational conditions, extending its service life.
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 enhances gas separation efficiency by maintaining high selectivity and permeation flux while extending the membrane's service life under harsh conditions, reducing replacement costs and improving membrane durability.
Implementation Method 1
phase-inverting the membrane forming composition in a first non-solvent to form the membrane comprising a substantially non-porous surface layer
Implementation Method 2
a thin, dense, selectively semi-permeable surface 'skin' and a less dense void-containing, non-selective support region
Data Source
AI summary
An asymmetric membrane having a substantially non-porous surface layer is made by a method including: dissolving a poly(phenylene ether) copolymer in a solvent mixture including a first solvent and a second solvent to provide a membrane-forming composition; and phase-inverting the membrane forming composition in a first non-solvent to form the membrane comprising a substantially non-porous surface layer. The first solvent is a water-miscible polar aprotic solvent, and the second solvent is a polar solvent having two to eight carbon atoms.