Effect of gold electronic state on the catalytic performance of nano gold catalysts in n-octanol oxidation

UIDB/50006/2020 project VIU-RSCBMT-65/2019 project 18-29-24037 (Russia) MINECO project CTQ2017-86170-R (Spain)This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/MxOy/TiO2 (where MxOy are Fe2O3 or MgO) for the liquid phase oxidation of n-octanol, under mild conditions. For this purpose, Au/MxOy/TiO2 catalysts were prepared by deposition-precipitation with urea, varying the gold content (0.5 or 4 wt.%) and pretreatment conditions (H2 or O2), and characterized by low temperature nitrogen adsorption-desorption, X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDX), scanning transmission electron microscopy-high angle annular dark field (STEM HAADF), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy of CO adsorption, temperature-programmable desorption (TPD) of ammonia and carbon dioxide, and X-ray photoelectron spectroscopy (XPS). Three states of gold were identified on the surface of the catalysts, Au0, Au1+ and Au3+, and their ratio determined the catalysts performance. Based on a comparison of catalytic and spectroscopic results, it may be concluded that Au+ was the active site state, while Au0 had negative effect, due to a partial blocking of Au0 by solvent. Au3+ also inhibited the oxidation process, due to the strong adsorption of the solvent and/or water formed during the reaction. Density functional theory (DFT) simulations confirmed these suggestions. The dependence of selectivity on the ratio of Brønsted acid centers to Brønsted basic centers was revealed.publishersversionpublishe

Competitive HDS and HDN reactions over NiMoS/HMS-Al catalysts: Diminishing of the inhibition of HDS reaction by support modification with P

[EN] The effect of the support (Al-HMS) modification with P between (0.0-2.0 wt.%) was studied in this work. NiMo/Al-HMS-P(x) catalysts were prepared and sulfided in order to be tested in the hydrodesulfurizarion (HDS) reaction of dibenzothiophene (DBT), hydrodenitrogenation (HDN) of carbazole and simultaneous HDS and HDN reactions. The materials were characterized by X-ray diffraction (XRD), FT-IR of framework vibration (FTIR-KBr), Micro-Raman spectroscopy, temperature programmed adsorption of ammonia (TPD-NH3), N2 adsorption–desorption isotherms and X-ray photoelectron spectroscopy. For both, individual HDS and HDN reactions, all P-containing catalysts have shown a higher activity with respect to P-free sample. The catalyst modified with optimized amount of P (1 wt.%) promoted DBT transformation via HYD route of this reaction. Due to the important HYD properties, the NiMo/Al-HMS-P1.0 sample showed the lower inhibition factor during simultaneous HDS and HDN.CONACYT projects 152012, 155388 and 117373 for the financialsupports