Crosslinked Polyimide Gas Separation Membrane
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Solution Overview
Problem
Existing gas separation composite membranes face challenges in achieving sufficient gas permeability, separation selectivity, and mechanical strength, especially under high pressure and in the presence of plasticizing impurities, due to issues with membrane plasticization and poor solubility of multibranched polyimide structures.
Innovation Solution
A gas separation composite membrane is developed with a crosslinked polyimide resin structure, where 2 to 4 polyimide molecules are coordinated with a divalent to tetravalent central metal via an oxygen or sulfur atom, and the membrane is applied as a thin layer on a gas permeable porous support to enhance gas permeability and mechanical strength, while suppressing ligand exchange and gelling during the coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the membrane is made thinner to enhance gas permeability, then gas permeability is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs a composite membrane structure consisting of a porous support layer and a thin polyimide coating layer. The porous support provides mechanical strength while the thin polyimide layer provides gas separation functionality. This composite structure resolves the contradiction by allowing the membrane to be thin for high permeability while the support layer maintains mechanical integrity.
Solution Approach 2:
Different regions of the membrane have different properties: the porous support layer provides mechanical strength and structural integrity, while the thin polyimide coating layer provides gas separation selectivity and high permeability. This local differentiation of properties allows the membrane to simultaneously achieve high gas permeability and sufficient mechanical strength.
2Strength
If a crosslinked structure is introduced to suppress membrane plasticization and enhance mechanical strength, then mechanical strength and plasticization resistance are improved, but gas permeability deteriorates
Solution Approach 1:
The patent carefully controls the crosslinking degree and uses specific crosslinking agents to achieve optimal balance. By adjusting crosslinking parameters and selecting appropriate crosslinking density, the membrane maintains sufficient mechanical strength and plasticization resistance while preserving adequate gas permeability through the thin layer effect.
Solution Approach 2:
The crosslinked structure is introduced locally in the polyimide coating layer to provide plasticization resistance and mechanical strength, while the overall thin layer structure maintains high gas permeability. The crosslinking is confined to the separation layer rather than the entire membrane structure.
3Strength
If a thick gas separating layer is used to ensure mechanical strength, then mechanical strength is improved, but gas permeability deteriorates
Solution Approach 1:
The membrane uses a composite structure where a thick porous support layer provides mechanical strength and structural integrity, while a thin polyimide coating layer (micrometer or sub-micrometer scale) provides gas separation functionality. This allows the overall membrane to have sufficient mechanical strength while the thin separation layer ensures high gas permeability.
Solution Approach 2:
The membrane is segmented into two functional layers: the porous support layer that provides mechanical strength and the thin polyimide coating layer that provides gas separation. This segmentation allows each layer to optimize its specific function without compromising the other.
4Strength
If multibranched polyimide structures are used to enhance mechanical strength and plasticization resistance, then mechanical strength is improved, but solubility and processability deteriorate
Solution Approach 1:
The patent modifies the polyimide molecular structure by introducing multibranched structures with controlled branching degrees and uses specific solvents or solvent blends to achieve adequate solubility. By adjusting molecular weight, branching density, and solvent composition, the patent maintains mechanical strength while enabling processability for membrane fabrication.
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 exhibits excellent gas permeability, high separation selectivity, and resistance to plasticization, with a thin and uniform gas separating layer that maintains performance under high pressure and in the presence of impurities, achieving enhanced mechanical strength and durability.
Implementation Method 1
applying a solution containing a polyimide compound having an active hydrogen-containing group and a metal complex, thereby performing ligand exchange between the polyimide compound and the metal complex
Implementation Method 2
2 to 4 molecules of a polyimide compound is coordinated with a divalent to tetravalent central metal via an oxygen atom or a sulfur atom
Implementation Method 3
a desired gas component can be separated by allowing selective permeation, by means of a membrane constituted of a specific polymer compound
Implementation Method 4
applying the solution containing the polyimide compound and the metal complex, thereby performing ligand exchange between the polyimide compound and the metal complex, and forming the gas separating layer
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 above the gas permeable supporting layer, in which the crosslinked polyimide resin has a structure in which 2 to 4 molecules of a polyimide compound is coordinated with a divalent to tetravalent central metal via an oxygen atom or a sulfur atom, and when the crosslinked polyimide resin has plural central metals, the plural central metals are linked via the polyimide chain of the polyimide compound; and a gas separating module, a gas separation apparatus and a gas separation method utilizing this gas separation composite membrane.