Airborne Preparation of Small Gold Nanoparticles Dispersed on Mesoporous Silica for the Catalytic Oxidation of Glycerol to Dihydroxyacetone

Supported gold nanoparticles play a fundamental role in modern material science and particularly in heterogeneous catalysis. Supported gold nanoparticles are known to be excellent catalysts, not only for the total oxidation of various pollutants (CO, VOCs) but also for the selective oxidation of bio-based platform molecules (such as glycerol) to added-value chemicals (dihydroxyacetone, glyceric acid, and glycolic acid). Controlling their fine dispersion however remains a challenge, especially when using silica supports. We report a simple one-pot aerosol route to mesoporous Au-SiO₂catalysts featuring small gold nanoparticles (∼3 nm). To achieve this, we rely on the strong interactions between the gold and thiol functions of a mercapto-silane: (3-mercaptopropyl)-trimethoxysilane (MPTMS). The addition of this gold stabilizer during synthesis enhances the stability of the gold precursor and is the key to controlling the formation of small gold nanoparticles. The dispersion of gold in the material reaches 21% (compared with 3% without the stabilizer). The selective oxidation of glycerol to dihydroxyacetone was employed as a test reaction, of importance in the context of sustainable chemistry. The highly dispersed catalyst obtained via gold stabilization outcompetes benchmark catalysts, reaching a glycerol conversion of 59% after 8 h (vs 5% without stabilization).