Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Gold nanoparticles (AuNPs) were anchored on alkynyl carbamate-functionalized support materials having the suitable features for application as catalysts in continuous-flow packed bed reactors. The functionalization step was carried out by grafting with the difunctional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) three commercial micrometer-sized oxide supports, i.e. silica, alumina, and titania. The alkynyl-carbamate moieties were capable of straightforwardly reducing the gold precursor HAuCl4 yielding the supported AuNPs systems Au/SiO2@Yne, Au/Al2O3@Yne, and Au/TiO2@Yne. A comparison among the three materials revealed that silica allowed the highest organic functionalization (12 wt %) as well as the highest gold loading (3.7 wt %). Moreover, a TEM investigation showed only for Au/SiO2@Yne the presence of homogeneously distributed spherically shaped AuNPs (average diameter 15 nm). Au/SiO2@Yne is an efficient catalyst, both in batch and flow conditions, in the oxidation of a large...