from first principles PP-I-1

Mechanistic Aspects of Hydrogenation and Oxidation of SugarsMurzin D.Yu.Åbo Akademi University, Turku, Finlanddmurzin@abo.fiKL-4In recent years, exploitation of renewable sources has gained considerable attention. Inparticular polyols and acids derived from respectively hydrogenation and oxidation of sugarsare versatile molecules with a variety of applications. In the lecture these reactions occurringin the aqueous phase will be discussed.Extensive kinetic studies on oxidation of arabinose, galactose and glucose combined withelectrochemical potential measurements along with investigations of structure sensitivity andcatalyst characterization were conducted over supported gold catalysts for the interpretation ofthe reaction mechanism [1]. The influence of the reaction parameters such as pH, temperature,and oxygen flow rate was investigated. In-situ catalyst potential measurements duringoxidation gave information about the extent of the oxygen accumulation on the metal surfaceand a correlation to activity was obtained. An oxidative dehydrogenation mechanism wasproposed and a kinetic model taking into account the catalyst potential changes wasdeveloped.Hydrogenation of D–maltose, D–galactose, L–rhamnose and L–arabinose and some of theirbinary mixtures to corresponding polyols was carried out on a finely dispersed Ru/activatedcarbon catalyst with the objective of studying the kinetics and the reaction mechanism [2].This work was supplemented with DFT investigations of five L-arabinose tautomersadsorption on a ruthenium surface allowing advancing a reaction mechanism. In particular itcould be suggested that conformers of sugars are mostly adsorbed keeping the conformationalproperties and the most abundant tautomer, perpendicularly interacting with the metal surface,is the one, which is probably hydrogenated.References:[1] B. T. Kusema et al. Appl. Catal. A. Gen. 386 (2010) 101; B. T. Kusema et al. ChemCatChem.3 (2011) 1789; O. Simakova et al., J. Phys. Chem. C. 115 (2011) 1036; B. T. Kusema et al., Catal. Sci.Tech. 2 (2012) 423.[2] V.A. Sifontes Herrera et al. J. Chem. Tech.Biotech. 86 (2011) 658; R. Cortese et al., J. Phys.Chem. C. (in press)19