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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.

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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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Based on the important effect of catalyst on the plasma-catalytic system, various types of zeolites (5A, HZSM-5, Hβ, HY and Ag/HY) were chosen as catalysts to remove toluene under non-thermal plasma condition in this work. The results showed that all the zeolites, whether with toluene adsorption ability or not, significantly enhanced the toluene removal efficiency in the plasma discharge zone. Moreover, the carbon balance and CO 2 selectivity showed the same tendency of Ag/HY >HY > Hβ (HZSM-5)>5A, which was basically consistent with toluene adsorption ability, while opposed with the ozone emission. Loading silver on zeolite greatly decreased organic byproducts emission, and further improved the mineralization of toluene oxidation. At the same time, the intermediates including ringopening products on the catalyst surface were identified, and the pathways of toluene decomposition were proposed.

Fundamental understanding of the structure sensitivity of Au-catalyzed H 2 O 2 formation from H 2 with O 2 is of prime scientific and industrial significance. Herein, DFT calculations are employed to reveal the underling nature of the site-dependent H 2 O 2 formation activity and selectivity over three typical Au(111), Au(100), and Au(211) sites. The hydrogen dissociation is suggested as the ratedetermining step. The structural and charge analysis and the energy barrier decomposition indicate one lower-coordinated edge atom on the Au(211) as the active site for hydrogen dissociation. Furthermore, competition reactions between hydrogenation/desorption of the species involving the O−O bonds and their cleavage are comparatively studied. Au( 111) is found to exhibit the highest selectivity to H 2 O 2 . Finally, a combination of the low-coordinated Au atom with Au( 111) is proposed as the catalytically active center of H 2 O 2 formation. The results demonstrated here could be valuable for fabricating highly active and selective catalysts for H 2 O 2 formation.