Synthesis and structure characterization of Ru nanoparticles stabilized by PVP or γ-Al2O3

Uniform and stable Ru nanoparticles were synthesized by reduction of RuCl3 in ethylene glycol (EG) in the presence of poly(N-vinyl-2-pyrrolidone) by using microwave-assisted solvothermal method. The obtained materials were characterized by UV–vis, FT-IR, XPS, XRD and TEM techniques, and used as precursors of heterogeneous metal colloid catalysts. Characterization by TEM showed that as-prepared PVP-stabilized Ru nanoparticles have small average diameters (below 2 nm) and narrow size distributions (1–3 nm). Diffraction data confirmed that a crystallite size is around 2.0 nm. A colloidal Ru/γ-Al2O3 catalyst was obtained by two different methods: immobilization of the PVP-stabilized Ru colloid on the support or by in situ deposition of Ru colloid, e.g., reduction of RuCl3 with EG in the presence of the γ-alumina. It was found that both synthesis methods produced the Ru/γ-Al2O3 catalysts with narrow size distributions of metallic nanoparticles, that are distributed uniformly over the support. However, only in situ preparation of the colloidal Ru/γ-Al2O3 catalyst results in chlorine free system with high activity for hydrogen chemisorption. The H2 uptake on the Ru(PVP)/γ-Al2O3 catalyst was very low because the ruthenium surface was strongly occluded with a thin layer of polymer molecules.