Solvent-mediated electrochemical acetylene semihydrogenation for continuous production of polymer-grade ethylene

The purification of crude ethylene is an energy-intensive process facing the challenges of high temperature, poor stability, and low ethylene selectivity. Here, we report a solvent-mediated electrochemical acetylene semihydrogenation approach that operates under mild conditions by exploiting differences in solvent absorption between acetylene and ethylene without solvent loss. This strategy significantly enhances the selective dissolution and diffusion of acetylene impurities to the cathode surface and drives their rapid hydrogenation to ethylene at the electron- and proton-rich liquid-solid interface. Over a 200-h continuous-flow stability test, the conversion of acetylene to ethylene remained at ∼100% with an ethylene selectivity of >99% and residual acetylene of <5 ppm under a crude ethylene stream. Theoretical, physical, and operando spectroscopic investigations revealed that solvent-mediated electrochemical acetylene semihydrogenation is thermodynamically favorable and follows a proton-coupled electron-transfer mechanism with water as the hydrogen source and that the solvent regulates catalytic activity and the hydrogenation mechanism.