A study was carried out on the reaction of acetone transformation over bifunctional monometallic (Pt/H[Al]ZSM5, Sn/H[Al]ZSM5) and bimetallic (PtSn/H[Al]ZSM5) catalysts with variation of their tin atomic fraction (X-Sn = number of Sn moles/number of Sn moles + number of Pt moles). The solids prepared were analyzed by means of X-ray diffraction (XRD), nitrogen adsorption at - 196 degreesC, chemical analysis through inductive coupled plasma-atomic emission spectroscopy (ICP-AES) technique, energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance (EPR), transmission electronic microscopy (TEM), and by means of test reaction of toluene hydrogenation. Acetone transformation was carried out at 160degreesC, under atmosphere pressure, at an acetone/hydrogen molar ratio of 3 and varying WHSV. The results obtained show a sensitive variation in the catalytic properties as X-Sn is varied in the series of PtSn/H[AI]ZSM5 catalysts prepared; these changes are attributed to the presence of effects of the electronic and geometric type, which would be a consequence of the formation of a Pt-Sn alloy and probably of the phenomenon of decoration of platinum particles, which is evidenced from the evaluation of the solids by means of XPS and EPR. (C) 2003 Elsevier B.V. All rights reserved.