n-Pentane aromatization was investigated over Ni ion exchanged ZSM-5 catalyst instead of Ga-ZSM-5 and Zn-ZSM-5, which are commercially used for aromatization of lower alkanes. Suprisingly, yields of aromatics over the Ni-ZSM-5 catalysts were equivalent to those over the Ga or Zn-ZSM-5 catalysts. As Ni was ion exchanged, the number of Lewis acid sites increased. Ni ion, acting Lewis acid site, has much higher initial selectivity to olefins such as propylene and ethylene which seem to act as intermediate for aromatics. However, mechanical mixture of NiO and H-ZSM-5 did not show good reactivity and this indicates that there are little solid-solid reactions among them. Hydrogen treatment at 500℃ of Ni-ZSM-5 catalyst did not affect the conversion of n-pentane. However the yields of aromatics decreased with hydrogen treatment above 800℃ possibly due to partial reduction of Ni ion to metal. Since reduction of Ni ion in ZSM-5 is very difficult at reaction condition, it seems that the active species for n-pentane aromatization is $Ni^{2+}$.
