Fischer-Tropsch synthesis seems to develop the following two consecutive paths : a primary process that involves the formation of alpha-olefin products and a secondary process leading to the production of branched isomers and paraffins and requiring the readsorption of primary alpha-olefin products. It was already shown by Iglesia et al. (E. Iglesia, S. C. Reyes, and R. J. Madon, J. Catal. 129, 238 (1991)) that such readsorption steps are of fundamental importance for Ru catalysts and that they occur due to the slow diffusive removal of alpha-olefins when the molecular size increases, this resulting in a long intraparticle residence time. In the present paper alpha-olefins readsorption was enhanced by changing the metal distribution inside the pores of a titanium silicate (ETS-10), modified by ion exchange with alkali metal ions, used as a support for Ru-based catalysts.