Sonia Gil

Remarkable Enhancement of O2 Activation on Yttrium-Stabilized Zirconia Surface in a Dual Catalyst Bed

Yttrium-stabilized zirconia (YSZ) has been extensively studied as an electrolyte material for solid oxide fuel cells (SOFC) but its performance in heterogeneous catalysis is also the object of a growing number of publications. In both applications, oxygen activation on the YSZ surface remains the step that hinders utilization at moderate temperature. It was demonstrated by oxygen isotope exchange that a dual catalyst bed system consisting of two successive LaMnO3 and YSZ beds without intimate contact drastically enhances oxygen activation on the YSZ surface at 698 K. It can be concluded that LaMnO3 activates the triplet ground-state of molecular oxygen into a low-lying singlet state, thereby facilitating the activation of the O2 molecule on the YSZ oxygen vacancy sites. This phenomenon is shown to improve the catalytic activity of the LaMnO3-Pd/YSZ system for the partial oxidation of methane.

Low-temperature catalytic oxidation of vinyl chloride over Ru modified Co3O4 catalysts

Ruthenium modified cobalt oxides were prepared by (1) impregnating ruthenium chloride hydrate on cobalt oxides, Ru-supported catalysts (Ru/Co3O4), and (2) Ru-doped catalysts (Ru–Co3O4) where the ruthenium ions were added to the precursor solution, by a one-step sol–gel method with cobalt nitrate. The physicochemical properties of the catalysts were characterized by ICP, BET, XRD, HR-TEM, TPR, and XPS analysis. The effects of ruthenium were studied for the total oxidation of vinyl chloride. This Ru modifier was observed to enhance oxygenate formation. The different preparation methods made contributions to the different amounts of Ru4+ on the surfaces of the catalysts while Ru4+ would be in synergy with Co2+ concentration, and this also changed the chemical coordination of oxygen on the surface. Dispersion of Ru oxides on the cobalt oxides surface could not only improve the catalytic activity and stability on steam, but also decrease the amount of chlorinated by-products and increase HCl selectivity.

Study of Lanthanum Manganate and Yttrium-Stabilized Zirconia-Supported Palladium Dual-Bed Catalyst System for the Total Oxidation of Methane: A Study by 18O2/16O2 Isotopic Exchange

A significant enhancement of the yttrium‐stabilized zirconia‐supported palladium (0.2 wt % Pd/YSZ) catalytic activity for the total oxidation of methane was achieved in a dual‐bed system by the association of LaMnO3+Pd/YSZ materials. The combination with the best performance was 40 wt % LaMnO3+60 wt % Pd/YSZ. Pd/YSZ and LaMnO3 perovskite were characterized by using the 18O2 exchange technique. A Mars–van Krevelen mechanism was demonstrated over Pd/YSZ at 425 °C. Additionally, it was evidenced that LaMnO3 activated the O2 molecule on the YSZ oxygen vacancy sites to result in a significant increase of the oxidation rate characterized by a correlating decrease of the light‐off temperature of 65 °C.