Developing stable yet efficient Au-Ti bifunctional catalysts is important but challenging for direct propylene epoxidation with H 2 and O 2. This work describes a novel strategy of employing uncalcined titanium silicalite-2 (TS-2-B) to immobilize Au nanoparticles as a bifunctional catalyst for the reaction. Under no promoter effects, the Au/TS-2-B catalyst compared to the referenced Au/TS-1-B catalyst delivers outstanding catalytic performance, that is, exceptionally high stability over 100 hr, propylene oxide (PO) formation rate of 118 g PO Áhr −1 Ákg cat −1 , PO selectivity of 90% and hydrogen efficiency of 35%. The plausible relationship of catalyst structure and performance is established by using multiple techniques, such as UV-vis, high-angle annular dark-field scanning transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. A unique synergy of Au-Ti 4+-Ti 3+ triple sites is proposed for our developed Au/TS-2-B catalyst with the higher stable PO formation rate and hydrogen efficiency. The insights reported here could shed new light on the rational design of highly stable and efficient Au-Ti bifunctional catalysts for the reaction.

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.

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