abstracts - Институт катализа им. Г.К. Борескова

KS-I-6MODERN UNDERSTANDING OF HETEROGENEOUS CATALYSIS: DOES THEBULK MATTER?CO, METHANE AND ETHYLENE OXIDATION ON PALLADIUMZemlyanov D., Aszalos-Kiss B., Kleimenov E. 1 , Teschner D. 1 , Zafeiratos S. 1 ,Hävecker M. 1 , Knop-Gericke A. 1 , Schlögl R. 1 , Han J. 2 , Ribeiro F.H. 2 , Gabasch H. 3 ,Unterberger W. 3 , Hayek K. 3 , Klötzer B. 3Materials and Surface Science Institute and Physics Department, University of Limerick,Limerick, Ireland1 Abteilung Anorganische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft,Faradayweg 4-6, D-14195 Berlin, Germany2 School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, WestLafayette, IN 47907-2100, USA3 Institut für Physikalische Chemie, Universität Innsbruck, A-6020, Innsbruck, AustriaE-mail: dimazemlyanov@purdue.eduAnnotationThis investigation focuses on oxidation of CO, methane and ethylene on the surface ofpalladium single crystals as a model catalyst. The number of in situ and ex situ techniqueswas exploited such as in situ XPS, TPD, STM, LEED, kinetic measurements, etc. It wasfound that dissolution of carbon and oxygen can change catalytic activity of palladium,leading to passivation or activation of the catalyst.Introduction: According to traditional understanding of heterogeneous catalysis, chemicalreaction occurs on the surface and reaction rate mainly depends on a surface composition anda surface structure. However, dissolution of small molecules such as hydrogen, oxygencarbon might take place during reaction and this might result in the changes of electronic andstructure property of the surface. As the consequence, catalyst behaviour can change.This investigation focuses on oxidation of methane and ethylene on the surface of palladiumsingle crystals as a model catalyst. Palladium is considered as the best catalyst for thecatalytic combustion/partial oxidation of methane and other small hydrocarbons, which is anenvironmentally benign process for power generation with low NO x emissions and forremoval of residual methane from the emission gases of methane-powered vehicles (see forinstance [1] and Refs. therein). Catalytic combustion of methane is carried out underconditions varying from low temperatures, where PdO is the thermodynamically stable phase,to high temperatures, where Pd metal is stable. PdO is believed to be the more active phase inmethane combustion [2-4]. Therefore, an understanding of the palladium oxidationmechanism and the mechanism of palladium oxide decomposition is critically important. Anadequate understanding of the oxidation mechanism is impossible without an in situ high-34