Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Efficient H2O2-based Propylene to Propylene Oxide (HPPO) Reaction Catalyzed over ZnO/ZnO₂ Materials (#437)

Gebretinsae Yeabyo Mr. Nigussie 1 2 3 , Yi-Fang Dr. Tsai 3 , Tsung-Cheng Mr. Yang 4 , Chia-Min Prof. Yang 4 , Steve Sheng-Fa Prof. Yu 3
  1. Department of Applied Chemistry, National Yang-Ming Chiao Tung University, Hsinchu , N/A, Taiwan
  2. Sustainable Chemical Science and Technology (SCST), Taiwan International Graduate Program (TIGP), Academia Sinica , Nankang, Taipei , Taiwan
  3. Institute of Chemistry, Academia Sinica , Academia Sinica, Taipei city, Taiwan
  4. Department of Chemistry, National Tsing Hua University, Hsinchu , N/A, Taiwan

ABSTRACT: Propylene oxide (PO) is an essential feedstock in the plastic industry. Herein, unprecedented, inexpensive and robust zinc oxide (ZnO)-based catalysts were prepared. A ZnO nanorod (ZnO-NR) catalyst was synthesized using a solvothermal method. Another type of ZnO catalyst supported and immobilized on mesoporous MCM-41 material (ZnO/MCM-41(x)) was also prepared with varied proportions (x = 0.82-9.41 wt %) of Zn content. The catalytic reactions of propylene epoxidation over ZnO-NR and ZnO/MCM-41(x) with H2O2 as an oxidant and acetonitrile as a solvent were studied at 30-70 ºC and 5-20 bar. The ZnO catalysts were found capable of catalyzing the reaction with high H2O2 utilization and PO selectivity.1 Among them, the ZnO/MCM-41(7.99) achieved nearly 100% PO selectivity and the highest turnover number of 124.4 (moles of PO per mole of Zn). In this reaction, H2O2 acted as a biomimetic oxidant in epoxidation reactions by forming metal-oxo species that mimic enzymatic oxidation pathways. This process is akin to the renowned peroxide shunt pathway in cytochrome P450, which provides the alternative route to activate the iron-heme center. The activation leads to the formation of the reactive high-valent iron-oxo species (compound I), which are capable of oxygenating inert hydrocarbons. The fresh catalysts of ZnO-NR, ZnO/MCM-41(7.99), the spent catalysts, and the ZnO2 nanoparticles were characterized by synchrotron powder X-ray diffraction, transmission electron microscopy, and X-ray absorption spectroscopy.  The fractions of ZnO2 in the spent catalysts were quantified to be higher than 50%. Electron paramagnetic resonance and X-ray photoelectron spectroscopies revealed that the ZnO2 phase formed by reacting ZnO with H2O2 in acetonitrile, stored as green redox oxide materials, contained species of hydroperoxide, peroxide and superoxide, which can be essential for catalytic production of PO. The fact of 18O enrichment to PO using H218O2 suggested that the reactive oxygenated species are generated from H2O2 and anchored on/in ZnO2 for the electrophilic epoxidation, with the assistance of acetonitrile.

Keywords: propylene, epoxidation, hydrogen peroxide, zinc oxide, zinc peroxide

 

  1. 1. Nigussie, G. Y.; Tsai, Y.; Yang, T.; Yang, C.; Yu, S. S.-F. An Efficient H₂O₂-based Propylene to Propylene Oxide (HPPO) Reaction Catalyzed by ZnO/ZnO₂ Materials. J. Mater. Chem. A, 2025, 13, 5261-5274.