Nitrophobic Polymer Membranes for Air Separation

Lott, Amber L.A.; Machado, Craig A.; Trujillo, Matthias A.; Ziegler, Kirk J.; Savin, Daniel A.*

Department of Chemistry, University of Florida
Department of Chemical Engineering, University of Florida

The industrial process of converting coal to energy requires extracting a large volume of oxygen from air by cryogenic distillation, which is very costly and energy inefficient.  To overcome this challenge, a polymer membrane able to produce a large volume of O₂ by selectively allowing O₂ to pass through the membrane from air would be ideal to replace the cryogenic distillation process. The use of a polymer membrane to produce large volumes of O₂ gas would decrease the greenhouse gas footprint. Currently, there are few membranes available that have good permeability and high selectivity of O₂ gas from a N₂/O₂ gas mixture.  Our approach is to develop a nitrophobic polymer membrane by incorporating azo linkages between aromatic and aliphatic regions of the polymer backbone. Azo linkages should be able to increase O₂ selectivity by repelling N₂ from entering the membrane. We synthesized azo-linked polymers by a one-step synthesis utilizing varying nitroaromatics and aliphatic amines. Characterization of azo polymers was done with thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and fourier transform infrared spectroscopy (FTIR).  The azo polymers made from different varying nitroaromatics and aliphatic amines contain good thermal stability. Some azo polymers were stable up to 375°C.