| Metal-support interactions are often invoked whenever the modifications in the catalytic properties of the supported metal cannot be rationalized in terms of the basic functions of the support: namely the stabilization of small metal particles on the catalyst surface and/or the providence of a functionality different from that of metal in bifunctional catalysis.;Metal-support interactions were studied from two entirely different perspectives: modifications of the metal behavior, and changes in the support induced by the presence of the metal. The second issue was mostly overlooked in previous work.;Different supports (MgO, SiO(,2), TiO(,2), SiO(,2)-Al(,2)O(,3), NaY) and different catalyst preparations were used to obtain metal particles of varying sizes. The catalysts were characterized by chemisorption, TEM, WAXS, and FTIR.;The activity and selectivity of gold in the H(,2) reduction of NO clearly depended upon the nature of the support. When CO was adsorbed on MgO supported catalysts, adsorbed species were detected on both the metal and the support, in contrast to blank MgO where no adsorption took place under identical conditions. Thus, CO chemisorption may not be suitable for measuring the metal dispersion of MgO supported catalysts. The adsorbed species on the support were a mixture of mono- and bi-dentate surface carbonates at the metal-oxide interface. Their exact identity was dependent on the metal particle size and the nature of the metal. There was no enhanced uptake of CO by the support when the metal was supported on SiO(,2) or TiO(,2).;Due to its limited catalytic activity, gold was used in this research to simplify the detection of metal-support interactions. Any activity enhancement of gold could be easily attributed to an interference from the support. Ruthenium was included in the research to study the effects of an active metal in metal-support interactions. Bimetallic ruthenium-gold catalysts were used to explore the feasibility of using a second metal addition to control the existing metal-support interactions.;Apparent metal-support interactions in ruthenium-catalyzed cyclopropane hydrogenation and hydrogenolysis could be explained simply by a metal particle size effect. The experimental results also indicated a dilution of surface ruthenium atoms by gold in the bimetallic ruthenium-gold catalysts. |
