Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-3-specialKINETIC MODELING OF LACTOSE OXIDATION OVERSUPPORTED PALLADIUM AND GOLD CATALYSTSD.Yu. Murzin, E.V. Murzina, A.V. Tokarev, J.-P. MikkolaProcess Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FIN-20500,Turku/Åbo, Finland, fax: +358 2 215 4479, E-mail: dmurzin@abo.fiIntroductionLactose, an abundant disaccharide, can be oxidized resulting first in lactobionic acid, andthen in 2-keto-lactobionic acid [1-3].Oxidation of sugars is very sensitive to several factors such as pH and the oxygen feedrate. The «in situ» catalyst potential measurements give important information about red-oxstate of the catalyst surface.ExperimentalLactose oxidation was studied in the present work using such measurements over Pd/Cand Au/Al 2 O 3 catalysts. Catalytic experiments were performed at 60-90 o C and pH from 6 to10 at different oxygen flow rates. Samples of the liquid phase were periodically taken andanalyzed by HPLC with Biorad Aminex HPX-87C column (t =80 o C and flow 0.4 ml /min).KineticsLangmuir type of kinetics was applied to describe the concentration behavior leading tothe following rate expression for lactobionic acid consumptionk3KLCLKoPO2rLA=(1)21+K P + K C + K C )(o O2LLOH−OHFor gold catalysts it was proposed that initially adsorption of oxygen occurs on edges,corners and perimeter of nanoparticles, migrating further to faces, where it is transferred intoinactive in catalysis oxide. In order to explain experimentally observed electrochemicalpotential behavior of gold catalysts reduction of oxygen in alkali media with involvementshould be assumed.An expression for the catalyst potential is32