Oxidation of sugars from hemicelluloses represents an important lignocellulosic biomass valorization process and has been considered as an option to decrease high dependency of chemical industry on fossil feedstock. Gold nanoparticles as an arabinose oxidation catalyst under alkaline conditions result in high selectivity towards aldonic acids. In this work, kinetics of selective oxidation of L-arabinose to arabinonic acid over Au/Al2O3 was studied using data from experiments in a semibatch shaker reactor under pH-controlled conditions at atmospheric pressure. A novel model considering molecular adsorption of oxygen, production of H2O2 and different skeletal isomers of arabinose as reactants is reported. An experiment with D-arabinose was carried out in a conventional semibatch reactor and the model adequately predicted the results.