Crosslinked Polyimide Composite Membrane for Gas Separation
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Solution Overview
Problem
Existing gas separation membranes face challenges in achieving high gas permeability, separation selectivity, and mechanical strength while maintaining stability over time, especially under conditions with high carbon dioxide concentration and presence of impurities like water, hydrogen sulfide, and aromatic compounds.
Innovation Solution
A composite membrane is developed with a gas-permeable supporting layer and a gas separating layer containing crosslinked polyimide resin, featuring specific polar groups that enhance crosslinking under mild conditions, improving stability and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single raw material is processed into a thin asymmetric membrane layer, then gas permeability is improved, but it is difficult to simultaneously achieve high separation selectivity and mechanical strength
Solution Approach 1:
The membrane is divided into two functional layers: a porous supporting layer that provides mechanical strength and a thin gas-separating layer that provides separation functionality. This segmentation allows each layer to be optimized independently for its specific function.
Solution Approach 2:
The invention uses a composite membrane structure combining a porous supporting layer (made of polymers like polyethylene, polypropylene, or polyester) with a gas-separating layer (made of cellulose or polyimide). This composite structure integrates the advantages of both materials: mechanical strength from the support and separation performance from the functional layer.
2Manufacturing precision
If cellulose or polyimide membranes are used for natural gas purification, then separation capability is improved, but the membrane undergoes plasticization under high pressure and high carbon dioxide concentration, causing decrease in separation selectivity
Solution Approach 1:
The invention changes the physical and chemical parameters of the membrane by controlling the thickness of the gas-separating layer to 0.1-5 μm and optimizing the porosity and pore size distribution of the supporting layer. These parameter changes enhance separation performance while reducing plasticization effects.
Solution Approach 2:
The gas-separating layer is designed with specific local properties (thickness, polymer composition, crystallinity) optimized for separation, while the supporting layer has different local properties (porosity, mechanical strength) optimized for structural support and stability. This local quality differentiation allows the membrane to maintain separation selectivity under high pressure conditions.
3Productivity
If the membrane operates continuously for extended periods, then productivity is improved, but impurities such as water, hydrogen sulfide, long-chain hydrocarbons, and aromatic compounds stagnate in the membrane module, potentially damaging the membrane material
Solution Approach 1:
The porous supporting layer with controlled porosity (30-80%) and pore size (0.01-10 μm) allows for better flow distribution and reduces stagnation of impurities. The porous structure prevents concentration polarization and facilitates continuous removal of permeated gases, reducing the buildup of damaging substances.
Solution Approach 2:
The membrane is pre-designed with optimized thickness and porosity parameters that prevent impurity accumulation before it causes damage. The thin gas-separating layer (0.1-5 μm) minimizes the path for impurity diffusion, while the porous support structure facilitates continuous flushing of accumulated substances.
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 composite membrane achieves excellent gas permeability and separation selectivity, along with enhanced mechanical strength and durability, effectively handling impurities and maintaining performance over time.
Implementation Method 1
a gas separating layer containing a crosslinked polyimide resin over the gas-permeable supporting layer, wherein the crosslinked polyimide resin has structure in which a polyimide compound is crosslinked and linked
Implementation Method 2
A raw material comprising a polymer compound has characteristic gas permeability for each raw material. Capability of separation of a desired gas component is known, based on properties thereof, by a membrane constituted of a specific polymer raw material
Implementation Method 3
Study has been made so far for a membrane separation method as a means for removing an impurity such as carbon dioxide therein
Data Source
AI summary
A gas separation composite membrane, containing a gas-permeable supporting layer and a gas separating layer containing a crosslinked polyimide resin over the gas-permeable supporting layer, in which the crosslinked polyimide resin has structure in which a polyimide compound is crosslinked and linked, and the polyimide compound is a copolymer having at least an imide group-containing monomer component and a monomer component having a specific polar group; and a module, a gas separation apparatus and a gas separation method using the same.