Electrochemically Modulated Separation of Olefin-Paraffin Gas Mixtures in Membrane Electrode Assemblies

Olefin-Paraffin separations are large-volume energy-intensive processes used in preparing purified monomers such as ethylene and propylene. Currently, these separations are performed using distillations which account for 90-95 % of the energy utilization in the chemical and petroleum refining industries. In this work, we demonstrate an alternative olefin-paraffin separation method based on an electrochemically modulated swing absorption system. Nickel maleonitriledithiolate, an electrochemically-active organometallic complex, is dispersed in the ionogel binder of a membrane electrode assembly (MEA). When exposed to propylene-propane gas mixtures, propylene is selectively captured during the oxidation of the complex and is then released when the complex is reduced. Our results suggest that transport limitations of olefins to electrochemical active sites play an important role in determining separation efficacy. Experiments conducted under varying oxidative (from 1 to 3 V) and a reductive potential of -2 V demonstrated operational robustness of the MEA over multiple capture-and-release cycles. This proof-of-concept demonstration represents a new non-thermal route for the production of some of the largest organic chemical commodities in industry.