A novel chemical looping approach for direct propylene oxidation to propylene oxide and other oxygenated products was investigated. Supported Ag- and Au-based catalysts were prepared, using SrFeO3-δ perovskite as a catalyst support, and characterised using X-ray diffraction (XRD), electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Particles of the catalysts were used in experiments carried out in a packed bed reactor over the range 260–300OC, by passing 5vol% propylene over the material to generate oxygenated products, with oxygen provided via reduction of the catalyst support. The solid particles (AgCl/Au/SrFeO3-δ) were subsequently re-oxidised with air in a separate step, closing the chemical loop. Outlet gas was analysed using online Fourier-transform infrared spectroscopy (FTIR) and offline gas chromatography (GC). Gold-based catalysts displayed some activity towards propylene oxide production, as well as considerable selectivity towards formation of propan-1-ol, with 5wt%AgCl,5wt%Au/SrFeO3-δ giving stable c.55-60% selectivity towards propan-1-ol over the studied temperature range. Postulated mechanisms for propan-1-ol formation under chemical looping conditions are discussed, via propylene oxide or propanal intermediates.

Use of Ag and Au catalysts in chemical looping oxidation of propylene

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ACS Fall 2022

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