The light olefins present in Delay Coker and fluid catalytic cracker dry gas can be valorized into naphthenes using a new PtGaZr/SiO2 catalyst. This catalyst was compared to a GaZrSiO2 catalyst prepared with the same methodology. Both were characterized by XRD, and FTIR, XpS, Ga-71, Si-29 and H-1 NMR spectroscopies. Propylene is treated in the presence Of CS2, hydrogen, and benzene in a semi-batch type reactor and the product composition is analyzed by GC and MS techniques. The different operating variables were explored to study the effect of Pt on activity, selectivity and catalyst stability. The spent catalysts after 10 cycles in operation were analyzed using C-13 NMR, H-1 NMR, IR, and XPS spectroscopies. The paper discusses the catalytic surface composition, the effect of temperature, contact time, hydrogen partial pressure and benzene in the feed. The study demonstrated that the effect of Pt, hydrogen and benzene is crucial to orient the reaction toward naphthenes production. (C) 2007 Elsevier B.V. All rights reserved.