Six kinds of platinum-loaded sulfated zirconia-alumina (Pt-SZA) were prepared with the intention of investigating the effect of the electric types of platinum compounds, the amount of platinum, and the pH value of the impregnated material.For the effect of electric type, the platinum particles in catalysts prepared by using a cationic platinum compound, [(NH3)(4)Pt](2+), showed much higher dispersion and more even distribution than those in catalysts prepared by an anionic compound. [PtCl6](2-), because of strong interaction of the cationic platinum compound with SZA. The above two catalysts showed almost the same isomerization activities in the synthesis of normal hexane, but the catalyst prepared by the cationic platinum compound showed higher isomerization activity when normal hexane containing 6% of benzene was used as feedstock. The catalysts with 0.33 and 0.50 wt.% amounts of Pt prepared by using the cationic platinum compound showed almost the same activities, even for the feedstock mixed with 6% of benzene.The catalyst with 0.11 wt.% of Pt also showed nearly the same activity as those two catalysts to the normal hexane, but its activity dropped remarkably with the feedstock with 6% of benzene. The reduction of activity was based on the amount of Pt, 0.11 wt.%, being insufficient for the ring-opening hydrogenation of the cycloalkane.As for the effect of pH of the cationic Pt complex ion solution, pH around 7 was desirable. The life of the catalyst (0.33 wt.% Pt) was evaluated for 1800 h by using commercial light-naphtha. The catalyst showed above 80 of research octane number (RON) and above 0.7 of iso-pentane/C5 alkane ratio of liquid product without showing any deactivation. The catalyst prepared by the anionic platinum compound also showed high performance. However, a much higher amount of coke was detected than for that prepared by the cationic one. The differences of the activity in existing benzene and the coke deposition of the catalyst in the life evaluation are due to the dispersion of platinum particles, which have influence upon the ability to supply spillover hydrogen. (C) 2003 Elsevier Science B.V. All rights reserved.