III International Conference

PP-II-65CATALYTIC ACTIVITY OF OXIDES OF TUNGSTEN AND MOLYBDENUM,REDUCED BY HYDROGEN IN PRESENCE OF PLATINUM METALS ANDCESIUM, IN REACTIONS OF SMALL MOLECULES OXIDIZATIONLisnyak V.V., Yatsimirsky V.K., Gut I.N., Boldyrieva O.Yu.Chemical Department of Kyiv National Taras Shevchenko University, Kyiv, UkraineE-mail: lisnyak@chem.univ.kiev.uaWe have shown that H 2 reduced WO 3 and MoO 3 with Pt(Pd) and/or Cs + additives exhibithigh catalytic activity in the reaction of H 2 , CO and CH 4 oxidation. It has been found thatmain catalysts component formed during reduction are hydrogen bronzes caused high surfacearea and considerable activity and of the composite catalysts. Deactivation of the catalystsoccurs because of the bronze destruction at high-temperature regimes.Oxides of transitional 3d- and 4d-metals (V 2 O 5 , MoO 3 , WO 3 ) with small admixtures of Ptor Pd at reduction by hydrogen able to form compounds belongings to the class of hydrogenoxide bronzes H x V 2 O 5 , H x MoO 3 , H x WO 3 [1-4]. In contrast to pure oxide, the bronzesformation on the surface and bulk increase considerably catalytic activity of resultedcomposites in different heterogeneous catalytic processes, for example in the reactions ofisomerisation and conversion of hydrocarbons [5]. Formation of oxide bronzes occurs due tothe effect of the spillover of hydrogen adsorbed on Pt and Pd, from the metal to the properoxide [1,2]. It is considered that Pt and Pd play the role of catalysts of reduction of the oxides.Besides, the platinum metals are the most active catalysts of many reactions, for example, ofhydrocarbons combustion, oxidization of CO and H 2 , hydrocarbons hydrogenation. Additionsof salts of alkaline metals to catalysts diminish energy of oxygen binding with the surface ofcatalyst [6], that promote the catalytic activity increase. Potential of high active catalyticsystems in the processes of complete oxidization and their stability in reaction mixturescontaining oxygen excess is practically unexplored. In this work the results of examination ofcatalytic activity in the reactions of complete oxidization of small molecules (H 2 , CO andCH 4 ) of oxides of tungsten and molybdenum partly-reduced with H 2 in presence of Pd or Pt,and also Cs + are reported. Influencing of parameters of the reduction (temperature and time)on catalytic properties of the composite systems were studied. Also stability of the compositesystems was examined at high temperatures in gas mixture with excess of oxygen, andcompared with the activity of traditional Pt or Pd of catalysts supported on γ-Al 2 O 3 .Catalysts were prepared by the impregnation on moisture capacity and further werereduced with hydrogen. The oxides of tungsten and molybdenum (Reakhym, 99.999 % mass.282