This NSF Accelerating Innovation Research (AIR) project will translate and further develop a new generation of crosslinked aromatic polymer membranes for removing carbon dioxide from natural gas, separating oxygen (O2) and (N2) from air, and for hydrogen (H2) purification. The technology is based on the discovery that select examples of these membranes have unprecedented combinations of permeation, gas selectivity and resistance to performance degradation, particularly during separations of condensable gases such as carbon dioxide. Existing membranes are largely amorphous, glassy engineering thermoplastics that lack durability to organic contaminants in the gas streams. The AIR innovation provides a means to fabricate membranes into hollow fiber platforms in solution, but also the membranes can be post-modified to develop both the needed durability as well as very good transport and mechanical properties.
The economical separation of air into O2 and N2 will enable inert N2 atmospheres to transport food globally and also will be applied to aircraft fuel tanks to minimize fires/explosions. Economical generation of purified H2 will play a critical role in developing a hydrogen economy for fuel cell systems for transportation, stationary (home) power, and portable electronics.
Judy Riffle, PI, Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA and Benny D. Freeman, Dept of Chemical Engineering, the University of Texas Austin, Austin, TX Intellectual Merit: The major goals of this AIR project have been to design and develop mechanically-robust, polymeric, gas separation membranes superior to the state-of-the-art for a variety of separations including air into oxygen and nitrogen, natural gas into the carbon dioxide impurity and methane, ethane, and higher hydrocarbon molecules. Finally, the separation of hydrogen from several components including carbon dioxide, carbon monoxide, and the major natural gas component methane is a goal. A series of ductile polymers were designed and developed and it was discovered that, with key substituents on the aromatic rings, they could be crosslinked in the solid state after thin-film membranes had been fabricated. The crosslinked membranes have improved gas selectivities relative to current membranes that have been commercialized with little loss in permeability (flux). The extent of crosslinking was controlled through systematic variations in chemical structure and the conditions used in the "post-membrane" crosslinking process. We have worked closely with our third party investors to delineate relationships among structure, crosslinking conditions, and mechanical and transport properties. This concept of crosslinking the materials in the solid state, thin-film forms has now been demonstrated on many related polymers and copolymers. Our third party investor is exploring scalable economic manufacturing processes to utilize this achievement. The membranes will also necessarily require successful fabrication into asymmetric films and/or hollow fibers. Broader Impacts: A provisional patent has been filed and we anticipate filing of the major U.S. patent application soon. Polymeric membranes are well known to provide an energy-saving processing advantage for selective gas separations as compared to thermal distillation. Over the short term, in collaboration with our third party investor, we are exploring applications for these materials that include air separations to provide an inert nitrogen blanket for "on-board" aircraft engines, inert blanketing of large cargo compartments on transportation vehicles that carry flammable liquids, and for storage of foods in nitrogen-enriched atmosphere to lengthen their usable lifetime. The relatively recent technology to recover natural gas in the United States has opened up new types of gas and liquid separations that are critically needed and that would benefit the U.S. economy. Thus, new technologies related to processing of polymeric membranes could find use in oil and natural gas recovery and in processing of oils in refineries. This could significantly impact manufacturing processes in the U.S. chemical process industry. By creating an interdisciplinary and industrially relevant program, we have been able to educate students in their fundamental polymer science field, and also in communication and collaboration skills. Chemistry students (Virginia Tech) and Chemical Engineering students (University of Texas) have been able to broaden their field of technical expertise through this collaboration. They have worked together as a team and also worked with our third party industrial investors. We believe that they will be able to carry these teaming and communication skills into future careers to benefit their companies and our economy.
