Palladium nanoparticles supported on carbon black were synthesized by two different methods precipitation reduction (PR) and urea-assisted sodium formate homogeneous deposition (HD). The catalysts were then submitted to thermal treatments at 573 K, 873 K and 1173 K to produce catalysts with a wide range of particle sizes. The obtained catalysts were characterized by XPS, TEM CO chemisorption and TGA measurements and tested in the oxidative dehydrogenation of glucose to gluconic acid. It was found that catalysts with a palladium particles size of 7 rim exhibit the highest activity. Above or below this particular value the oxidative dehydrogenation of glucose appeared less efficient.