III International Conference

PP-II-162several carbon materials as well. The obtained noble metal modified carbon catalysts werecomparatively studied in respect of their textural properties, noble metal particle sizes andcatalytic behaviour. Therefore, materials were characterized by means of nitrogenadsorption at 77 K and X-ray diffraction (XRD), whereas, the selective oxidation ofglucose to gluconic acid was employed as test reaction, since this reaction has beeninvestigated and described in literature systematically [5-7]. X-ray photoelectronspectroscopy (XPS) and inductive coupled plasma optical emission spectroscopy (ICP-OES) had been applied revealing additional information about the distribution of thereactive metal component within the carbon matrix.ExperimentalSynthesis of noble metal doped carbon catalysts were performed via two differentsynthesis routes. On the one hand, preparation of noble metal modified carbons occurredby customary deposition of a noble metal precursor onto the carbon support, which wasprepared by template assisted synthesis beforehand. In contrast, direct synthesis wasrealised by template assisted route whereas the noble metal precursor has been introducedin the synthesis approach already [8]. However, sucrose as carbon precursor andamorphous silica gel [9] or MCM-48 [2] as solid siliceous templates have been applied forboth synthesis routes. Hexachloroplatinic acid and tetrachloroauric acid were employed asnoble metal precursor salts, respectively. The liquid phase oxidation of glucose wasperformed under stable alkaline conditions using a semi batch reactor at 323 K with an airflow as oxidizing agent.600ImpregnatedDirectly synthesized600ResultsMesoporous noble metalmodified carbon materials had beenobtained no matter which synthesispathway was employed. For bothprocedures low noble metal contentsat the external surface and rathersmall particles have been found inSpecific Activity [mol Gluc.conv./h · mol Pt]50040030020010000 5 10 15Metal particle size [nm]pore width > 5 nmpore width < 5 nm0 10 20 30Metal particle size [nm]Fig.1: Effect of metal particle size (XRD) and pore width(DFT) on the specific catalytic activities of impregnatedand directly synthesized platinum containing carbons5004003002001000Specific Activity [mol Gluc.conv./h · mol Pt]465