Cux/ZnO-y Catalysts. Effect of Support Modification by High Energy Milling on the Metal-Support Interaction

Commercial ZnO, was subjected to high-energy milling to introduce structural modifications, which can result in a different metal-support interaction. The milling time (0 to 960 min) and vial material and mill balls (WC and ZnO2), were modified. The supports were characterized by XRD, Scherrer, SBET, Raman Spectroscopy. With the increase in grinding time, an increase in the accrued kinetic energy (Ecum) was observed. For the same Ecum, with ZrO2, twice the area was obtained in just 6 min. Cu was deposited on both, the ground support (ZnO-z) and unmilled support (ZnO-0) in three compositions; x = 0.2, 0.5, and 1 (% wt). AAS measurements showed Cu compositions similar to the theoretical ones. XRD studies, Rietveld modeling and Raman Spectroscopy confirmed that Cu cations could be localized, either by substituting the Zn2+ ions or interstitially in the network, depending on the metal content. The TPR profiles showed two types of copper species, which interact differently with the support. Likewise, the analysis of the XPS results showed that, with the increase in Cu content, for Cux/ZnO-0 there is a decrease in the metal-support interaction. However, for Cux/ZnO-z the interaction increases, which can be associated with the introduction of structural defects accompanied by superficial energy changes. For both systems, different catalytic behaviors are expected in the hydrogenolysis reaction of glycerol in liquid phase, regarding selectivity and stability, as a result of the metal-support interaction achieved