The effect of WO3 (5-50 wt%) and ZnO (0.7-22 wt%) on the catalytic properties of Pt/WO3/(ZnO)-ZrO2 for n-heptane (n-C-7) hydroisomerization was investigated. The optimized WO3 and ZnO contents are 20 wt% and 3.4 wt%, respectively. The catalytic performance is achieved at 81 % n-C-7 conversion and 89% C-7 isomer selectivity at 250 degrees C, which is reproducible and can be kept constant over 82 h under reaction conditions. Both WO3 and ZnO can stabilize the tetragonal phase of ZrO2. The Bronsted acid-to-Lewis acid ratio should be optimized to achieve high catalytic performance. The activity for Pt/WO3/ZrO2 using Zr(OH)(4) as the catalyst support (n-C-7 conversion, 88% at 250 degrees C) is much higher than that for Pt/WO3/ZrO2 with ZrO2 as the support (n-C-7 conversion, 9% at 250 degrees C) with the same Pt and WO3 loadings. BET, SEM-EDX, and pyridine-FTIR analyses show that acid treatment can successfully enhance the surface area (from 73 to 91 m(2)/g), increase the number of Bronsted acid sites, and lower the surface Zn:Zr ratio (from 0.43 to 0.15) for ZnO-ZrO2 with 22 wt% ZnO. The yield of C-7 isomers is increased from nil to 47% at 300 degrees C on Pt/WO3/ZnO-ZrO2 catalyst after acid treatment. It is suggested that n-heptane hydroisomerization activity is related to acidity, surface area, and crystalline phase of ZrO2. (c) 2006 Elsevier Inc. All rights reserved.