Effects of surface activation on the structural and catalytic properties of ruthenium nanoparticles supported on...

Using colloid-based methods to prepare supported catalytic metallic nanoparticles (NPs) often faces the challenge of removing the stabilizer used during synthesis and activating the catalyst without modifying the particles or the support. We explored three surface activation protocols (thermal oxidation at 150 °C, thermal reduction at 350 °C, and argon-protected calcination at 650 °C) to activate ruthenium NPs supported on mesoporous silica (MSU-F), and assessed their effects on the structural and catalytic properties of the catalysts, and their activity by the aqueous phase hydrogenation of pyruvic acid. The NPs were synthesized by polyol reduction using poly-N-vinyl-2-pyrrolidone (PVP) as a stabilizer, and supported on MSU-F by sonication-assisted deposition. The NPs maintained their original morphology on the support during activation. Ar-protected calcination was the most efficient of the three for completely removing PVP from particle surfaces, and provided the highest degree of particle crystallinity and a metal dispersion comparable to commercial Ru/SiO2. Its catalytic performance was significantly higher than the other two protocols, although all three thermally activated catalysts achieved higher activity than the commercial catalyst at the same Ru loading. Post-reaction analysis also showed that the supported catalyst activated at 650 °C retained its morphology during the reaction, which is an important requirement for recyclability.