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Selective Oxidation of Veratryl Alcohol over Au-Pd/Ce0.62Zr0.38O2 Catalysts Synthesized by Sol-Immobilization: Effect of Au:Pd Molar Ratio

2018; Multidisciplinary Digital Publishing Institute; Volume: 8; Issue: 9 Linguagem: Inglês

10.3390/nano8090669

2079-4991

Carol M. Olmos, Lidia E. Chinchilla, Andrea M. Cappella, Alberto Villa, Juan J. Delgado, Ana B. Hungría, Ginesa Blanco, José J. Calvino, Laura Prati, Xiaowei Chen,

Catalysis and Oxidation Reactions

The selective oxidation of veratryl alcohol (VA), a model compound of lignin, with oxygen molecules to produce veratraldehyde (VAld) was studied over monometallic Au, Pd, and bimetallic Au:Pd nanoparticles supported on a Ce0.62Zr0.38O₂ mixed oxide for the first time. These bimetallic Au-Pd catalysts with Au:Pd molar ratios from 0.4 to 4.3 were synthesized by the sol-immobilization method. Furthermore, all the catalysts were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), N₂ physisorption, X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF) imaging, energy dispersive X-ray spectroscopy (EDXS), and temperature programmed reduction (TPR) techniques. A synergistic effect between gold and palladium was observed over all the bimetallic catalysts in a wide range of studied Au:Pd ratios. Remarkably, the optimum Au:Pd ratio for this reaction was 1.4 with a turnover frequency of almost six times larger than for the monometallic gold and palladium catalysts. Selectivity to veratraldehyde was higher than 99% for the monometallic Au, Pd, and all the bimetallic Au-Pd catalysts, and stayed constant during the reaction time.