Glassy Polymer Coated Polyamide Membrane for Gas Separation
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Solution Overview
Problem
Commercially available reverse osmosis and nanofiltration membranes are unsuitable for separating hydrogen and helium from gas mixtures containing carbon dioxide due to defects or pores that allow gas flow via Knudsen diffusion, making them ineffective for selective separation.
Innovation Solution
A multilayer gas separation membrane is developed, comprising a porous support layer, an aromatic polyamide layer formed via interfacial polymerization, and a glassy polymer coating with a glass transition temperature greater than 50°C, which is applied using methods like slot die coating or spin coating to plug pores and enhance selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If commercially available reverse osmosis and nanofiltration membranes are used, then membrane filtration capability is provided, but gas separation selectivity deteriorates due to defects and pores allowing Knudsen diffusion
Solution Approach 1:
The membrane is divided into multiple functional layers: a porous support layer providing mechanical strength and filtration, an aromatic polyamide layer formed by interfacial polymerization providing selective barrier properties, and a glassy polymer coating providing additional selectivity for gas separation. Each layer performs a specific function, collectively resolving the contradiction between filtration capability and gas separation selectivity.
Solution Approach 2:
The invention uses a composite membrane structure combining different materials: porous support (polymer or ceramic), aromatic polyamide (formed by interfacial polymerization of diamine and acyl chloride), and glassy polymer coating (such as polysulfone, polyimide, or polyether sulfone). This composite structure integrates the advantages of each material to achieve both filtration and high-selectivity gas separation.
2Manufacturing precision
If a dense aromatic polyamide layer is formed to block pores, then gas separation selectivity improves, but permeance deteriorates
Solution Approach 1:
The glass transition temperature (Tg) of the polymer coating is optimized to be greater than 50°C, preferably greater than 80°C, to ensure the polymer remains in a glassy state during operation. This parameter control maintains chain rigidity and free volume, achieving high selectivity while preserving adequate permeance. The thickness of the selective layer is also optimized to balance selectivity and permeance.
Solution Approach 2:
Different regions of the membrane have different properties: the porous support provides mechanical strength with high porosity, the aromatic polyamide layer provides intermediate selectivity, and the glassy polymer coating provides high gas separation selectivity. This local differentiation allows each layer to optimize its function without compromising overall 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 membrane achieves high selectivity and purity in separating helium and hydrogen from carbon dioxide, with helium/carbon dioxide ideal selectivity ranging from 20 to 70 and helium permeance between 5 and 150 GPU, reducing power consumption and improving recovery efficiency.
Implementation Method 1
defects or pores through which gas flow occurs via Knudsen diffusion
Implementation Method 2
an aromatic polyamide layer formed on the porous support layer via interfacial polymerization
Implementation Method 3
drying the solution to form a coating of the glassy polymer on the aromatic polyamide layer
Data Source
AI summary
A gas separation membrane for selective separation of hydrogen and helium from gas mixtures containing carbon dioxide includes a porous support layer, an aromatic polyamide layer on the porous support layer, and a coating including a glassy polymer formed on the aromatic polyamide layer. A glass transition temperature of the glassy polymer is greater than 50° C. The gas separation membrane may be formed by contacting a solution including the glassy polymer with an aromatic polyamide layer of a composite membrane and drying the solution to form a coating of the glassy polymer on the aromatic polyamide layer. Separating hydrogen or helium from a gas stream including carbon dioxide includes contacting a gas feed stream including carbon dioxide with the gas separation membrane to yield a permeate stream having a concentration of helium or hydrogen that exceeds the concentration of helium or hydrogen, respectively, in the gas feed stream.