Influence of the Acid Properties of the Support on Au‐Based Catalysts for Glycerol Oxidation in Aqueous Medium

Abstract

AbstractTuning the surface and structural properties of heterogeneous catalysts is important for alcohol oxidation with the aim of obtaining valuable aldehydes and carboxylic acids. In this work, gold nanoparticles (AuNPs) were dispersed and stabilized on two different supports, ZrO2 and TiO2, and the catalytic properties were evaluated in glycerol oxidation as a model reaction. AuNPs were first synthesized through the reverse micelle (RMs) synthetic strategy, which acted as nanoreactor, by using sodium 1,4‐bis(2‐ethylhexyl) sulfosuccinate (AOT). For instance, the growing was governed by the confined environment provided by the AOT micelle allowing obtaining pseudospherical AuNPs with an average diameter of 6 nm. Further deposition of the synthesized AuNPs on ZrO2 and TiO2 supports allowed, after annealing at 400 °C, obtaining AuNPs on ZrO2 and TiO2. Catalytic properties of these AuNPs on glycerol oxidation under oxygen atmosphere and in aqueous NaOH solution at 90 °C, demonstrated that the support type played a key role in the activity of gold species in terms of conversion of glycerol and selectivity, with lactic acid being the main product formed on Au/ZrO2 while glyceraldehyde was the main product formed on Au/TiO2. The differences in catalytic performance of Au/ZrO2 might be correlated to a better dispersion of AuNPs and a higher density of acid sites with middle strength that modified activation of glycerol and the aldehyde intermediates toward the formation of lactic acid.