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Au/ZnO showed the best activity in the oxidative esterification of ethylene glycol to methyl glycolate.

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In order to learn the active components and their functional mechanism during the plant-mediated synthesis of gold nanoparticles (GNPs), 16 kinds of plants were randomly selected as research objects, and statistical analysis was used to obtain more universal and systematic results. Polyphenols are proved to have the most prominent effect in both reductive and protective capability among all components. The relationship between polyphenols concentration and the protective and reductive capability was further studied in detail. Pyrogallic acid was used as a substitute for polyphenols to elucidate the functional mechanism. The concentration of polyphenols was found to be a critical factor for the preparation of GNPs, and the synergistic competition between phenolic hydroxyl and carbonyl groups caused by the oxidation of polyphenols could affect the particle size and morphology of GNPs. This work can provide excellent guidance for the controllable synthesis of GNPs via the plant-mediated method.

Thermally expanded graphene oxide supported PtAu alloy nanoparticles showed high catalytic activity in the oxidation of glycerol in base-free aqueous solution.

BACKGROUND Glycerol, which is a coproduct of biodiesel production, has been identified as a key platform compound for producing various valuable chemicals. The selective catalytic oxidation of glycerol to dihydroxyacetone is very attractive. RESULTS A series of Au catalysts supported on metallic oxides, i.e. ZnO, CuO, Al2O3, Fe2O3 and NiO, were studied for selective catalytic oxidation of glycerol to dihydroxyacetone under base‐free conditions. Among the catalysts, Au/CuO showed the best catalytic activity (glycerol conversion of 89% and dihydroxyacetone selectivity of 82.6% at 80 °C under 10 bar of O2), followed by Au/ZnO ≫ Au/NiO > Au/Al2O3 ≈ Au/CuO‐SD ≈ Au/Fe2O3. The catalytic behaviors of these supported Au catalysts varied depending on the Au particle size, Au oxidation state, Au–support interactions and lattice oxygen reducibility. CONCLUSION The main reasons for the high catalytic activity of Au/CuO are as follows. Firstly, the catalyst has small metallic Au particles, which are more active in cleavage of the secondary CH bond in glycerol molecules. Secondly, the interactions between Au and CuO facilitate lattice oxygen reduction, and this increases oxygen mobility, which may promote regeneration of Au–support perimeter active sites by gaseous oxygen. © 2019 Society of Chemical Industry

Selective catalytic oxidation of polyols, e.g., the selective catalytic oxidation of the secondary -OH bond in glycerol, remains a considerable challenge. In this study, a series of mesoporous CuO-SnO 2 composite oxides were prepared by a hard-template method and used to support Au catalysts for the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA) under base-free conditions. Catalysts with different Cu:Sn molar ratios gave different catalytic performances. A high conversion of glycerol (100%) and selectivity for DHA (94.7%) were obtained in 2 h at 80°C and P O2 = 1 MPa over the Au/CuO-SnO 2 -3:1 catalyst. Further investigation indicated that the high catalytic activity of Au/CuO-SnO 2 -3:1 is related to the small size and high dispersion of Au nanoparticles (NPs), the interactions between the Au NPs and the support, the synergistic effect between CuO and SnO 2 , and the amount of surface lattice oxygen species. Various reaction parameters, namely the glycerol:Au molar ratio, the reaction temperature, the initial O 2 pressure, the reaction time, and the support calcination temperature were studied. Although the conversion rate by the catalyst decreased after four cycles, the selectivity remained above 86%. Density functional theory calculations showed that the synergy between CuO and SnO 2 improves the catalytic activity in glycerol oxidation to DHA. The results show that mesoporous composite oxide supports have a wide range of potential applications in the selective oxidation of glycerol to other high-value-added products.

A series Cu–Al composite oxides supported Au catalysts were prepared and applied for the selective catalytic oxidation of glycerol to 1, 3-dihydroxyacetone (DHA) in base-free conditions. The optimal the Au/CuAlO-3...