Several catalysts consisting of Pt supported on sulfated or tungstated zirconia (one of them supported on alumina) have been characterized by different techniques, such as elemental and XRD analyses, N(2) adsorption, TPD of ammonia, TPR and H(2) chemisorption. All these catalysts were active in the transformation of two alpha-olefins, 1-pentene and 1-hexene, both present in most of FCC naphthas, whose conversion to internal and branched olefins is of a great interest for their use in reformulated gasolines and as intermediate chemicals. At low reaction temperatures (200-250 degrees C), both hydrogenation and double bond shift compete to give n-paraffins and internal olefins, respectively. As the temperature rises (>350 degrees C) the catalytic activity for the isomerization reactions increases, yielding a higher amount of internal and branched olefins. The product composition depends on the particular catalyst and reaction conditions used. The high activity of the sulfated zirconia, is remarkable and clearly indicates the participation of acid sites in these reactions. (C) 2009 Elsevier B.V. All rights reserved.