Three Pt/KL-zeolite catalysts containing 1 wt.% of metal were prepared by different procedures: Cl-1 and Cl-2 by wetness impregnation of the zeolite with aqueous solutions of Pt(NH3)(4)(OH)(2) and Pt(NH3)(4)(NO3)(2), respectively, and CE-3 by ion exchange with a Pt(NH3)(4)(OH)(2) solution. These samples were successively calcined at 573 K and reduced at 773 K. An additional sample, CE-3-n, was obtained from CE-3 by ion-exchange with KNO3. The catalysts were characterized by H2O2, titration, TPD of NH3, XRD, CO-FTIR and XPS and tested in the dehydrocyclization of n-heptane to toluene at 723 K, 100 kPa, WHSV = 3.4 h(-1) and H-2/nC(7) = 7.3 mol mol(-1) in a fixed bed tubular reactor. Characterization results show that Pt dispersion for the ion exchanged samples is higher than for the impregnated ones and CE-3 is the more acidic catalyst. FTIR measurements indicate that the highest population of electron reach platinum species (Ptdelta-) is found in CE-3-n, while CE-3 exhibits the highest concentration of electron deficient platinum species (Ptdelta+). The order of dehydrocyclization activity, CE-3-n > CI-2 > CI-1 > CE-3, roughly correlates with that of the intensity of the FTIR bands attributed to Ptdelta-. The low selectivity toward toluene of CE-3 is attributed to the protons generated during the reduction of Pt2+ exchanged. 41 (C) 2002 Elsevier Science B.V. All rights reserved.