Electrochemically modulated separation of olefin-paraffin gas mixtures in membrane electrode assemblies

Olefin-paraffin separations are large-volume energy-intensive processes for preparing purified monomers such as ethylene and propylene. Currently, these separations are performed using cryogenic distillations, accounting for approximately 250 trillion BTU per year of industrial energy consumption. This work demonstrates 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 potentials (from 1 to 3 V) and a reductive potential of -2 V demonstrated the operational robustness of the MEA over multiple capture-and-release cycles. This proof-of-concept demonstration represents a new non-thermal route for purifying the large olefin commodities in the chemical industry. Electrochemical flow cell demonstrates near-100% chemisorbing selectivity in separating propylene-propane gas mixtures, paving the way towards a sustainable olefin purifying process.