The bimetal-bearing SO2-4/ZrO2 superacid catalysts supported on ultra stable Y(USY) zeolite were prepared by impregnation and characterized with XRD and H2-TPR.Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor.The USY support well kept its pore structure in catalysts and the metal species were highly dispersed on the support.The Pt-bearing catalysts doped with Cr or Al were catalytically much more stable and exhibited higher catalytic activity and selectivity than the catalysts without dopants.Over the catalyst with a Pt loading of 0.4%(mass) and ZrO2 loading of 10%(mass)

the conversion of n-heptane was 42.1% with a selectivity of only 69.6% for isomerization products

while over the catalysts doped with Cr or Al with a molar ratio of Cr(Al) to Pt 5∶1

the conversion of n-heptane was 44.3% and 42.1% with the selectivity for isomerization products as high as 88.9% and 89.5% respectively.