Gold and silver catalysts for liquid phase n-octanol oxidation: Effect of promoters

Background: In comparison with these platinum group metal catalysts, supported nano gold catalysts have emerged as a new type of catalysts highly active at low temperature and selective for the aerobic oxidation of alcohols. But catalytic data and detailed characterizations of the Au-Ag bimetal catalytic system are not available up to date. Objective: This work is aimed to develop bimetallic AuAg-based heterogeneous catalysts for liquid phase selective oxidation of n-octanol. Modification of the titania support with transition metal additives were used as tools for transforming active species. Method: Catalytic tests in n-octanol liquid-phase oxidation at 80 °C. Catalyst characterization by Transmission electron microscopy, X-ray diffraction, plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, EXAFS and UV-visible spectroscopy. Results and Conclusion: Bimetallic AuAg catalysts supported on titania are moderately active for liquid phase selective oxidation of n-octanol. Formation of Au-Ag alloy was observed. Their activity may be increased by modification of the support with donor additives (La, Mg), while acceptor additives (Ce, Fe) decreased it. The addition of La, that inhibits the formation of Au-Ag alloy, provides the highest activity and the highest stability of reaction rate with run time in either as prepared and red-ox treated forms, which implies that it stabilizes the active centers in its optimal electronic state.