Casey O’Brien, assistant professor of chemical and biomolecular engineering at the University of Notre Dame, and his team have developed a novel method to see and measure carbon dioxide (CO2) on the molecular level, in order to provide details of how the gas moves across polymeric facilitated transport membranes (FTMs) during separation processes. Their findings could help reduce the world’s carbon footprint.
Not unlike lawyers who use eyewitness accounts to provide all the details about a specific event in order to uncover the truth, O’Brien and his team also use observation as they seek the truth about the reactions, interactions and separations related to industrial separation processes. The challenge is that the “events” chemical engineers are looking to document and understand are not visible to the human eye and not always able to be viewed in relation to the conditions of a process as it is occurring.
According to O’Brien, this is key. “It is thought that during an industrial process CO2 either ‘hops’ across FTMs from one amine group to another as carbamate species or is converted to bicarbonate species that are mobile within the polymer and then diffuse across the membrane,” he said. His team is working to better understand how that CO2 transport process is influenced by actual separation conditions, including temperature and the presence of other gases, as well as how the structure of the amines in the membrane influence its movement.
Since he has successfully employed operando spectroscopy — use of an infrared spectrometer to determine the chemical and physical properties of the materials undergoing reaction — to understand how the structure of catalytic surfaces influences their reaction mechanisms, O’Brien and his team are also using this method to monitor the reactions inside FTMs while simultaneously measuring permeation rates under realistic conditions. “We are the only university using operando spectroscopy to monitor transport mechanisms under realistic conditions,” he said. “This is critical because the CO2 transport mechanism could be different under more idealized laboratory conditions and skew our results.”
The project, funded by a grant from the American Chemical Society Petroleum Research Fund, runs through 2021. At that time, O’Brien and his team hope to use the information they have gathered to develop new membranes with greater permeability, selectivity and stability, which could allow for more robust separations to be achieved using less energy and at a lower cost than current technologies.
A faculty member since 2017, O’Brien is a participating faculty member in the Center for Nano Science and Technology and the Center for Sustainable Energy at Notre Dame.
Originally published by at conductorshare.nd.edu on October 30, 2019.