Polyimide Gas Separation Membrane Resisting Plasticization
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Solution Overview
Problem
Existing gas separation membranes face challenges in achieving both high gas permeability and selectivity, particularly under high pressure conditions and in the presence of impurities like toluene, which degrades their performance.
Innovation Solution
A gas separation membrane is developed using a polyimide compound with a specific repeating unit structure, incorporating a 1,3-phenylenediamine skeleton with substituents at the 2-position and 4- to 6-positions, which enhances both gas permeability and selectivity while resisting plasticization and impurity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional polyimide compound membrane is used, then gas separation selectivity can be improved by introducing polar groups, but the membrane becomes plasticized under high pressure conditions and by impurities like toluene, leading to degradation of separation performance
Solution Approach 1:
The patent uses a composite polyimide structure combining rigid aromatic rings (for mechanical strength and stability) with flexible alkyl chains and polar groups (for gas separation performance). This composite approach allows the membrane to maintain both high selectivity and resistance to plasticization by integrating materials with complementary properties.
Solution Approach 2:
The patent modifies the polyimide compound parameters by introducing specific substituents (alkyl groups for free volume control, polar groups for selectivity enhancement) at controlled positions and ratios. By adjusting these chemical parameters in the polymer structure, the membrane achieves optimal balance between gas permeability, selectivity, and stability under operating conditions.
2Productivity
If the gas separation layer is made thinner to increase gas permeability, then productivity improves, but the mechanical strength and separation selectivity may be compromised
Solution Approach 1:
The patent divides the membrane into two functional segments: a thin dense skin layer (0.01-5 μm) for gas separation and a thicker porous support layer for mechanical strength. This segmentation allows each layer to be optimized independently - the skin layer maximizes permeability while the support layer provides structural integrity.
Solution Approach 2:
The asymmetric membrane combines a dense polymer skin layer with a porous support structure, creating a composite material system where the thin skin provides high gas permeability and selectivity, while the porous substrate supplies mechanical strength and handles.
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 excellent gas permeability and selectivity, maintaining performance under high pressure and in the presence of impurities, with a carbon dioxide permeation rate greater than 20 GPU and a CO2/CH4 selectivity ratio of 15 or higher at 40°C and 5 MPa.
Implementation Method 1
A material formed of a polymer compound has gas permeability specific to the material. Based on this property, it is possible to cause selective permeation and separation out of a target gas component using a membrane formed of a specific polymer compound.
Implementation Method 2
In order to suppress the plasticizing of the membrane, it is known that introduction of a crosslinking structure or a branched structure to a polymer compound constituting the membrane is effective.
Implementation Method 3
resistance to impurities is not sufficient. In addition, the gas separation membrane is plasticized when exposed to toluene or the like and thus the gas separation performance is likely to be degraded.
Data Source
AI summary
Provided are a gas separation membrane which includes a gas separation layer formed to include a polyimide compound and in which the polyimide compound includes a repeating unit represented by the following Formula (I), a gas separation module, a gas separation device, and a gas separation method using the same.In Formula (I), R represents a group having a specific structure. R3 represents a specific substituent group. A1 to A3 represent a hydrogen atom or a specific substituent group, but all of A1 to A3 do not represent a hydrogen atom at the same time.In this case, at least one of R3, A1, A2, and A3 represents a specific polar group.