Size-Controlled Synthesis of Highly Stable and Active Pd@SiO2 Core–Shell Nanocatalysts for Hydrogenation of Nitrobenzene

Pd@SiO 2 core–shell nanoparticles were successfully synthesized by a sol–gel method. Tetradecyl trimethyl ammonium bromide capped Pd nanoparticles were coated with SiO 2 through the hydrolysis of tetraethylorthosilicate. The as-synthesized Pd@SiO 2 particles consist of Pd cores with a particle size of 3.7 nm and SiO 2 shells with a thickness from 10 to 30 nm at different synthetic conditions. The Pd@SiO 2 nanocatalysts with 1.9–2.4 nm mesoporous SiO 2 shells were generated after removal of tetradecyl trimethyl ammonium bromide from Pd@SiO 2 core–shell particles by calcination and following H 2 reduction. The relevant characterizations such as XRD, TEM, FT-IR, and BET were carried out for Pd@SiO 2 particles, and the results showed that the Pd@SiO 2 nanocatalysts were highly stable with the protection of silica shells, and the Pd cores did not increase during thermal treatment and H 2 reduction. The studies of catalytic CO oxidation at high temperatures and hydrogenation of nitrobenzene with H 2 were tested for Pd@SiO 2 nanocatalysts, and the results indicated that Pd@SiO 2 nanocatalysts were stable at high temperatures and highly active and stable for hydrogenation of nitrobenzene even after long time use.