Crosslinked Polyimide Asymmetric Membrane for CO2 Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current gas separation membranes, such as those made from cellulose esters and polyimides, face challenges with poor processability, irreversible CO2 selectivity reduction under high pressure, and limited product life due to plasticization, which affects their efficiency and longevity in CO2 separation applications.
Innovation Solution
An asymmetric membrane is developed using a crosslinked polyimide resin with specific structural units derived from tetracarboxylic dianhydride and diamine compounds, crosslinked with a compound having multiple functional groups, which enhances CO2 permeability and selectivity while maintaining high recovery rates and resistance to plasticization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cellulose ester is used as the membrane material, then gas separation performance is achieved, but processability deteriorates due to poor solubility in solvents
Solution Approach 1:
The invention uses a composite structure consisting of a porous support layer and a dense separation layer made from polyimide resin. This composite approach allows the porous support to provide mechanical strength and structural integrity, while the dense separation layer performs the gas separation function, thereby achieving both good processability and excellent gas separation performance.
Solution Approach 2:
The invention employs a porous support layer as the base structure, which provides mechanical strength and facilitates handling during processing. The porous structure also allows for efficient gas transport, while the additional dense separation layer ensures high selectivity for CO2 separation.
2Productivity
If high pressure is applied during gas separation, then separation efficiency is improved, but CO2 selectivity deteriorates due to plasticization of the polymeric membrane
Solution Approach 1:
The invention modifies the physical and chemical parameters of the membrane material by using crosslinked polyimide resin with specific structural units. The crosslinking increases the glass transition temperature and reduces free volume, allowing the membrane to maintain its selective properties at high operating pressures without undergoing plasticization.
Solution Approach 2:
The invention creates a dense separation layer with specifically controlled local structure and composition. This layer has tailored free volume distribution and chain packing density that resist plasticization, allowing high pressure operation while maintaining CO2 selectivity. The local quality of this layer is optimized independently from the bulk support structure.
3Reliability
If crosslinking is performed to improve plasticization resistance, then CO2 selectivity recovery is improved, but manufacturing complexity increases
Solution Approach 1:
The crosslinking is performed during the membrane fabrication process itself, before the membrane is put into service. The crosslinked structure is pre-formed in the dense separation layer, ensuring plasticization resistance and CO2 selectivity recovery from the outset, rather than requiring post-processing or recovery treatments.
4Productivity
If CO2 permeability is increased to improve separation efficiency, then productivity is improved, but CO2 selectivity deteriorates
Solution Approach 1:
The composite structure with porous support and dense separation layer allows independent optimization of permeability and selectivity. The porous support provides high permeability pathways, while the dense separation layer with crosslinked polyimide resin provides high CO2 selectivity, achieving both goals simultaneously.
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 asymmetric membrane achieves excellent CO2 permeability and selectivity, maintains high CO2 selectivity recovery rates, and extends product life, making it suitable for industrial gas separation and exhaust gas treatment applications.
Implementation Method 1
a gas separation membrane that selectively separates a target gas from a gas mixture is known
Implementation Method 2
the crosslinking agent being a compound having not less than two functional groups that bond with carboxy groups
Data Source
AI summary
An asymmetric membrane including a crosslinked polyimide resin, the crosslinked polyimide resin being formed by crosslinking a polyimide resin by a crosslinking agent; the polyimide resin including a structural unit (A) derived from tetracarboxylic dianhydride and a structural unit (B) derived from diamine; the structural unit (A) including a structural unit (A-1) derived from a compound represented by Formula (a-1); the structural unit (B) including a structural unit (B-1) derived from Formula (b-1), and a proportion of the structural unit (B-1) per 100 mol % of the structural unit (B) being from 0.1 to 50 mol %; and the crosslinking agent being a compound having not less than two functional groups that bond with carboxy groups.In Formula (b-1), Q1 and Q2 are each independently a group including an aromatic group, an aliphatic hydrocarbon group, and/or an alicyclic hydrocarbon group; X is a single bond or a particular group.