Highly dispersed mesoporous Au/SiO2 catalysts obtained by a direct aerosol-assisted sol-gel process

Abstract

Supported gold nanoparticles play a fundamental role in modern heterogeneous catalysis. However, controlling their fine dispersion remains a challenge, in particular when using silica supports. Here, we report a simple one-pot aerosol route to Au-SiO2 catalysts featuring small gold nanoparticles and calibrated mesoporous texture. To achieve such result, we rely on the strong interactions between gold and the thiol function of a mercapto-silane. We show that the addition of this gold-stabilizer during synthesis enhances the stability of the gold precursor and is the key to control the formation of small gold nanoparticles in the one-pot synthesis. After calcination, the catalyst displays advantageous textural properties (SSA = 440 m².g-1; Vp = 0.5 cm³.g-1; Dp = 5 nm) with small gold nanoparticles (3.7 nm, compared to 13.7 nm without the stabilizer). The dispersion of gold in the material reaches 21 % (compared to 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. We show that the highly dispersed catalyst obtained via gold stabilization outcompetes benchmark catalysts, reaching a glycerol conversion of 59 % after 8 hours (vs. 5 % without stabilization).

Multifunctional, Hybrid Materials Design via Spray‐Drying: Much more than Just Drying

“…Recently, a mesoporous Au‐Sn‐SiO 2 catalyst was prepared in one step by an aerosol‐assisted sol–gel synthesis. [ 120 ] Upon calcination, isolated Sn oxide species were stabilized in the silica matrix, and small gold nanoparticles were formed at its surface. The catalyst was able to catalyze the oxidation of glycerol (on Au NP) and the rearrangement of the formed dihydroxyacetone with methanol (on Sn species), to yield the targeted methyl lactate.…”