Supported and unsupported palladium nanoparticles for heterogeneous catalysis

Renee Wai Ying Man
2015
The development of new methods to prepare Pd-containing nanomaterials for catalysis are reported. Monodisperse, catalytically active Pd0 nanoparticles were prepared using a one-pot procedure, and new insights into the mechanism of the formation of these catalytically active Pd0 nanoparticles were obtained. A number of key intermediates and byproducts were determined using NMR and IR spectroscopies. Furthermore, addition of Lewis bases such as TOPO and DMSO to the reaction mixture greatly
more » ... ture greatly reduced the temperature at which highly monodisperse nanoparticles were formed. This effect was shown to be applicable to other Pd precursors in preparing Pd0 nanoparticles. Spherical Pd0@m-SiO2 core-shell nanoparticles were prepared and characterized by a number of techniques, including TEM, PXRD, TGA, and XPS. These nanoparticles consist of a Pd0 core enclosed by a mesoporous silica shell and are prepared using a simple, scalable one-pot procedure. The reaction conditions were crucial in controlling the morphology and pore diameter of the nanoparticles synthesized. Acid treatment of the Pd0@m-SiO2 nanoparticles was found to be the most suitable method in removing CTAB. The morphology, surface area, and pore diameter of the core-shell nanoparticles remained intact after removal of CTAB. A new ceria-containing core-shell material, PdO@m-CeO2, was prepared via templating from Pd0@m-SiO2 and PdO@m-SiO2 nanoparticles. The absence of Pd0 and presence of Pd2+ was explained by the possible formation of a solid solution composed of Ce1-xPdxO2-δ when Pd0 was the core. The catalytic activity of the nanoparticles was examined by performing the catalytic oxidation of methane. As well, the silica channels of the Pd0@m-SiO2 nanoparticles were used as selector to separate molecules based on their size. Size-selective hydrogenation was investigated using the porous silica shell of the Pd0@m-SiO2 nanoparticles as a selector, where the porous shell controlled the selectivity by the size of the substrates. Hydrogenation of a small molecule, 1-hex [...]
doi:10.14288/1.0167200 fatcat:nmlgcsckq5d2tfwyoxuf65u7fa