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Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Wang, Gang, Cao, Yueqiang, Zhang, Zhihua, Xu, Jialun, Lu, Mengke, Qian, Gang, Duan, Xuezhi, Yuan, Weikang, Zhou, Xinggui
Industrial & engineering chemistry process design and development 2019 v.58 no.37 pp. 17300-17307
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, activation energy, catalysts, catalytic activity, epoxidation reactions, gold, hydrogen, oxygen, process design, propylene, propylene oxide, temperature, thermogravimetry, transmission electron microscopy, ultraviolet-visible spectroscopy
Uncalcined TS-1-immobilized Au bifunctional catalysts have been demonstrated to be highly active yet stable for the propylene epoxidation with H₂ and O₂. The objective of this study is to further engineer the surface properties of uncalcined TS-1 toward enhanced bifunctional catalysis. A strategy by increasing the reduction temperature is proposed to remove the residual TPA⁺ template on the external surfaces, and the resultant Au/TS-1-B-300 catalyst gives rise to simultaneously enhanced activity, propylene oxide (PO) selectivity, and H₂ efficiency. These phenomena are explained by more exposed Ti-active sites and targeted catalysts’ electronic properties based on high-angle annular dark-field scanning transmission electron microscopy, thermal gravimetric analysis, UV–vis, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy measurements. Furthermore, kinetics analysis demonstrates a much lower activation energy for the main reaction to form PO, suggesting the existence of an appropriate reaction temperature for the PO yield. The obtained insights could shed new light on rationally designing and optimizing the catalysts by engineering the surface properties.