High-Performance Membranes for Gas Separation


Polymeric Membranes for the Separation of Natural Gas Components

High-Performance Gas Separation Membranes from Hydroxyl-Functionalized Microporous Polyimides

High-performance polymeric gas separation membranes have important applications natural gas industry. Ideal membranes should be both highly permeable and selective. However, there is an inherent trade-off between permeability and selectivity, as illustrated by the so-called Robeson upper-bound (see the below figures) that is plotted and updated according to the performance of the state-of-the-art membranes. It is of great significance but very challenging to develop new membranes with gas separation performance surpassing the upper bound. Rational molecular design of the polymeric materials is the key point to creating new membranes with superior gas separation abilities. To enhance gas permeability, an effective strategy is to introduce micropores into glassy polymers that would increase gas solubility and facilitate gas diffusion by decreasing the diffusion activation energy. ​On the other side, we note that another class of polymer, polyimides (PIs), can be easily functionalized to adjust their affinities to different gases, which allows the design of membranes for the highly selective separation of specific gas pairs.​ In this way, we invent PIs with spiro-centers and microporosities that attain excellent performance in the separating the CO2/CH4 gas pair.

Predicting the Microporosity (Accessible Free Volume)​ of Polymers Using Molecular Dynamics (MD) Methods

  • ​Xiaohua Ma, Yihan Zhu, Yu Han*, Ingo Pinnau*(2011, under preparation) ​