from first principles PP-I-1

PP-III-16Formation of Active Sites in NiZn/UDD Catalysts for the SelectivePhenylacetylene Hydrogenation as Monitored by in situ EXAFSChernikova V.S. 1 , Erokhin A.V. 1 , Golubina E.V. 1 , Murzin V.Y. 2 , Veligzhanin A.A. 2 ,Zubavichus Y.V. 21 M.V.Lomonosov Moscow State University, Moscow, Russia2 National Research Center “Kurchatov Institute”, Moscow, Russiacheleriya@gmail.comOne of the most important problems in modern catalysis is the development of targetedapproaches to the formation of active centers of a given composition and structure. Thesolution for this problem in addition to the expansion of tools for the directed synthesis is toprovide detailed control of the structural characteristics of the catalyst directly in the processof its preparation and subsequent chemical modification. For this purpose methods ofstructural diagnostics in situ, including those based on X-ray synchrotron radiation are moreand more often used worldwide.In this work, the formation of active sites in NiZn bimetallic catalysts supported onultradispersed diamond (UDD) is studied by temperature-programmed reduction withsimultaneous monitoring of metal state changes by X-Ray absorption spectroscopy(EXAFS/XANES) in situ. These catalysts show high activity in the selective hydrogenation ofcarbon-carbon triple bonds to double bonds.Catalyst precursors were prepared by impregnation from an aqueous solution of nickel andzinc nitrates (molar ratio 1:3), followed by drying and calcination in air (150С, 2:00). Formeasurements a pressed pellet of a catalyst was placed in a gas stream 2% H 2 in He, andsubjected to gradual heating. It was found that with the temperature increase two types ofprocesses of changes in the state of nickel were activated. At T ~ 300С the process ofordering of initially amorphous NiO begins with no change in the overall oxidation state ofnickel atoms. At 400С a slow chemical reduction of nickel sites to the metal state begins.The fraction of Ni (0) increases to ~ 25% within 4.5 hours and then ceases to change. Thismeans that only specific types of Ni sites undergo reduction under these conditions. Thechemical state of zinc remains essentially unchanged.The work was supported by RFBR grant 11-03-00820.167