Nanostructured silica-supported gold: Effect of nanoparticle size distribution and electronic state on its catalytic properties in oxidation reactions

摘要

Gold nanocatalysts, active in several oxidation reactions, suffer of insufficient time-on-stream stability. The easiest way to solve this problem is modifying the support, due to metal-support interaction. This study compares modifying effects of MgO and La2O3 on textural, electronic, and catalytic properties of Au nanoparticles (NPs) supported on inert nanostructured SiO2 in CO oxidation and liquid phase 1-octanol oxidation. Modification of the silica support surface with La and Mg increased metal support interaction, leading to gold particles with primary size of 1 nm but with different stability: stable under different pretreatment conditions on Mg-modified samples but highly sensible to the pretreatments on La-modified samples. Both modifiers changed electronic properties of supported gold favoring formation and stabilization of Au delta(+) states, which are probable gold active sites in catalytic redox processes. Modification with La and Mg oxides changed catalytic properties in CO oxidation before and after pretreatment in H-2 at 300 degrees C for 1 h. Gold catalysts supported on La- and Mg-modified silica showed similar performance in 1-octanol oxidation with higher conversion than unmodified Au/SiO2. La and Mg showed better promoting effects of catalytic properties in this reaction than redox modifiers (Fe and Ce) supported on small SiO2 particles.