III International Conference

CATALYSTS MOLECULAR DESIGN BY SURFACE SYNTHESIS OF THEPLATINUM POLYHYDROXOCOMPLEXES AS PRECURSORSPP-II-13Belskaya O.B., Duplyakin V.K., Karymova R. Kh., Nizovsky A.I., Larina T.V. 1 ,Maevskaya O.V.Institute of Hydrocarbons Processing SB RAS, Omsk, RussiaBoreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: obelska@incat.okno.ruThe paper deals with the problems of “metal complex – support” interaction at the stageof the precursor contact with the high surface area oxide support and the development ofsynthesis methods to modify greatly catalytic properties of an active metal.The hydrolyzed Pt-species as precursors were offered. The advantage of this Pt-species isa firm metal grafting due to the exchange of complex’s OH-ligands and the surfacehydroxogroups of alumina. Besides, an ability of hydroxocomplexes to form a bridge oxoandhydroxogroups provides polynuclear structures and thus a formation of active sitesgeometry at the initial stage of synthesis. The novelty of this research is to carry out asynthesis of Pt-hydroxocomplexes directly on the support surface by thermal hydrolysis ofpre-adsorbed chloride precursor.There are various opinions of surface reactions mechanisms in interacting a support andprecursor solution available in the literature. The investigation of surface metal complexes bythe method dividing surface Pt-species in amount according to the nature of their interactionwith the oxide support was conducted. The desorption technique suggested was used in twoversions. In the first case, the removal of surface forms was a result of the competitivesorption of anions essentially differing by the sorption selectivity onto alumina. In anothercase, the desorption of surface anion Pt-complexes was carried out due to the charge statechange of the alumina surface. The simultaneous proceeding of both ion exchanged processesin which Pt-complex keeps its nature in transferring from the solution onto the surface, andthe coordinated interaction accompanying by the entering surface groups into coordinationsphere was determined to be available in the process of metal deposition. The chemicalcomposition of ion exchange and coordinately bounded complexes were investigated byESDR and EXAFS methods. In the coordinately grafted complexes there are present thehydrolyzed species with the average composition [PtCl 2 (OH) 4 ]/Al 2 O 3 and/or[PtCl 2 (Н 2 O) 4 ]/Al 2 O 3 . Their reduction occurs at higher temperatures and formed Pt-crystallitesshow the specific adsorbed properties. However, the part of coordinately grafted species inthe samples prepared from chloride precursor is not in excess of 30 %.185