Selective catalytic oxidation of arabinose-A comparison of gold and palladium catalysts

Aqueous-phase selective oxidation of arabinose by molecular oxygen was studied in an isothermal shaking reactor at moderate conditions of 50-70 degrees C and pH 6-9. Different gold and palladium catalysts on metal oxide and carbon supports were tested. High catalyst activity and selectivity to arabinonic acid were achieved with Au/Al2O3 catalyst. Pd catalysts were characterized with low activity and selectivity due to the increase of the amount of by-products. The influence of the kinetic parameters such as pH, temperature, and oxygen flow rate was investigated. In situ catalyst potential measurements during arabinose oxidation gave information about the extent of the oxygen accumulation on the metal surface and a correlation to activity was obtained. The apparent activation energy E-a for the selective oxidation of arabinose to arabinonic acid was 23.8 kJ mol(-1) based on the temperature dependence of the experimental data. (C) 2010 Elsevier B.V. All rights reserved.