Catalytic and structural properties of ruthenium bimetallic catalysts: Preparation and characterization

In the framework of an EC Stimulation Action Programme, alumina-supported mono- and bimetallic Ru, RuGe, RuSn and RuPb catalysts have been prepared from both organic and inorganic precursors. Herein are presented some basic properties of these materials obtained by TPR and TPO experiments, H₂ and CO chemisorption, TEM examination, XPS and EXAFS studies. The use of organic precursors led to very small Ru particles, with a coordination number between Ru atoms of 4.35 (Ru⁰-Ru⁰+Ru⁰-Ru^δ+). The size of the metallic particles was not modified by adding Ge, Sn or Pb by the controlled surface reaction technique. In very small aggregates, some Ru atoms (10–15%) remained partially oxidised even after reduction at 623 K in flowing hydrogen. During the coimpregnation of alumina with inorganic precursors, the modifier played the role of a nucleation center for Ru, thus allowing small particles to be formed. We believe that CO could modify the surface composition of small bimetallic RuGe particles during the chemisorption.