A spatially integrated electrochemical-thermal tandem reaction for continuous mild synthesis of propylene oxide

An electrochemical-thermal tandem reaction system was designed in this work and enabled the highly efficient synthesis of propylene oxide (PO) at 1 atm without the use of H₂O₂. The electrochemical part produced OOH⁻ through a 2e⁻ oxygen reduction reaction, which migrated and distributed in the full space of a chamber filled with a mixture of solid electrolyte particles and modified TS-1 (m-TS-1) catalysts. Mediated by the relay of OOH⁻ and protic solvent methanol, full space tandem reactions were achieved with a high PO selectivity of 95.2% and a productivity of 319.75 mmol g_ecat⁻¹ h⁻¹. A mechanistic study revealed that the m-TS-1 catalysts accepted the migrated OOH⁻ and formed a Ti-OOH intermediate, which played a key role in relaying the tandem reactions for an efficient propylene epoxidation reaction. Techno-economic analysis and life-cycle assessment revealed favorable figures for the proposed process compared to the conventional process.