Understanding electrochemically induced olefin complexation: towards electrochemical olefin-paraffin separations

Olefin-paraffin separation is a critical yet energy-intensive process in the chemical industry, accounting for over 250 trillion BTU per year of global energy consumption. This work explores the use of a redox-active nickel maleonitriledithiolate complex for olefin-paraffin separations. Key performance factors, namely the electrochemical oxidation of the complex and olefin capture utilization fraction, were systematically quantified. Electrochemical studies revealed near-complete oxidation of Ni(ii) to Ni(iv) species, suggesting that the electrochemical oxidation step is not a limiting factor in olefin capture. The utilization fraction was found to be strongly dependent on the complexation equilibrium behavior between olefin-bound and unbound states of the complex. Time-resolved kinetic measurements unveiled a sluggish complexation rate, requiring over 36 hours to approach equilibrium. These insights highlight the importance of driving the complexation equilibrium and improving the kinetics to enhance the performance of Ni-based electrochemical swing absorbers for energy-efficient olefin-paraffin separations. The findings lay the groundwork for future optimization strategies and industrial implementation of this sustainable separation technology.