Electro-Epoxidation of Propylene in the Gas Phase with Solid-Polymer-Electrolyte Water Electrolysis.

The development of a reaction system for direct epoxidation of propylene is an essential topic. Gas-phase electro-epoxidation of propylene to propylene oxide (PO) with water as the oxidant was successfully accomplished by using solid-polymer-electrolyte (SPE) electrolysis without solvents. The oxidized surface of the PtOx anode was essential for propylene epoxidation and oxidation. It was revealed that PO was sequentially oxidized and accumulated on the anode by the interval electrolysis experiment. The formation rate and Faraday efficiency (FE) to PO were improved by applying mild hot-press conditions for the SPE unit because the active phase of the oxide surface of PtOx was maintained and diffusibility of water in the SPE (Nafion) membrane was improved. The FEs to PO are low in this work, but this system is halogen-free.