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Gold as a catalytic metal was widely studied during the last 25 years. Its application indifferent reactions has demonstrated that it is active when finely dispersed over differentsupports. One of these cases is the oxidation of sugars, where Pd is the catalyst mostcommonly applied due to its activity. However the main disadvantage of palladium is thedeactivation due to the overoxidation of the surface under reaction conditions. On thecontrary, gold catalysts are quite stable. The origin of this stability could be the surface stateof the catalysts. Thus XPS was applied to the characterization of fresh and spent Au/CeO2catalysts. The data included in this contribution are preliminar results of our study.Catalysts were submitted to different treatments: (a) reduction in formaldehyde (roomtemperature, 24 h) (b), reduction under hydrogen flow (300°C/3h) and (c) calcination inoxygen (300°C/3h). The samples were evaluated in arabinose oxidation at 60°C and pH 8.The spectra of the fresh catalysts allowed to confirm the presence of particles smaller than 2nm, evidenced by a contribution placed at binding energy lower than the one correspondent tometallic gold. This fact is also a consequence of the metal-support interactions. The presenceof Auδ+ implies the stabilization of gold particles on the surface defects, mainly oxygen vacancies [1]. The catalysts submitted to treatment (b) exhibits a small percentage of Au3+(See Table 1). Regarding the arabinonic acid concentration, the catalysts treated in hydrogen and oxygenpresented similar behaviour. On the other hand, the one treated in formaldehydepresented lower values. The explanation of this fact could be the state of gold surface. Toobtain the highest conversion of arabinose to arabinonic acid in the shortest reaction timesubstantial amount of gold should be present as Auδ+.