Abstract: The isomerization reaction of n-heptane over Pd/HZSM-5 bifunctional catalyst was studied. The effect of Si/Al ratio, crystal size and Pd loading on the reaction were investigated by micro-reactor-chromatograph system. The results showed that as the Si/Al ratio increases, the number of acid sites and the conversion of n-heptane decrease, however the isomerization selectivity of the catalyst is improved. Being the little effect of grain size of ZSM-5 molecular sieve on external surface area and acidity of the carrier, it has little influence on the isomerization performance of Pd/HZSM-5 catalysts. Loading Pd leads the conversion of n-heptane and isomerization activity improved significantly. However, when the Pd loading exceeds 0.4%, the metal function and acid function of catalyst reaches equilibrium state, and the conversion of n-heptane and isomerization activity no longer change significantly.

Key words: Si/Al ratio, Pd/HZSM-5 catalyst, n-heptane isomerization