Abstract: N-heptane, the paraffin that is difficult to convert, was used as a model compound to investigate the effect of potassium, mixture of rare earth cerium and potassium, and bi-rare earth metals (Ce,Eu) on n-heptane conversion. The results showed that adding potassium (0.045%, 0.060%) decreases the strong Lewis acidity of catalyst support, inhibiting the cracking reaction. At 510 ℃, cracking products decrease about 5 percentage points and the selectivity of iso-paraffins increases about 7 percentage points; adding mixture of cerium (0.28%) and potassium (0.010%, 0.030%) decreases the selectivity for cracking by 4.2-7.1 percentage points, while the iso-paraffin selectivity rises 7.4 - 9.8 percentage points at 510 ℃. Increasing reaction temperature has a weakened effect to certain extent on n-heptane conversion; Addition of bi-rare earth metals can effectively reduce the selectivity for cracking product at low temperature (510 ℃)，but the iso-parafin selectivety rises. The effect of addition of bi-rare metals on heptane transformation is weakened significantly with increasing the reaction temperature.

Key words: Pt-Sn catalyst, n-heptane, high temperature, additive metal