In order to prepare suitable catalysts for the aromatization reaction of n-pentane, metallosilicates catalysts were synthesized using conventional method and modified by ion-exchange with gallium nitrate, platinum chloride, zinc chloride, nickel chloride, iridium chloride and rhenium chloride. The aromatization reaction was performed with these catalysts. Conversion of n-pentane to aromatics was carried out in a continuous flow reactor at 1 atm. The analysis of reaction products was made with Gas Chromatograph equipped with FID detector.
Prepared metallosilicates were characterized by SEM, XRD, AA, IR, surface area, $NH_3$ TPD, which showed that prepared metallosilicates have a structure of ZSM-5.
The catalytic activities and selectivities to aromatics of Ga-silicate and HZSM-5 in the aromatization reaction of n-pentane increased with decreasing Si/metal ratio. The catalytic activity of Zn-silicate, Ni-silicate, and Fe-silicate was smaller than that of HZSM-5, while the selectivity to aromatics was higher than that of HZSM-5. TPD spectra of $NH_3$ of Ga-silicate indicated that the acid sites of medium acidity play an important role in the formation of aromatics. For all catalysts prepared, the conversion of aromatization reaction of n-pentane and the selectivity of aromatics increased with increasing reaction temperature. However, in case of Ga-silicate and Zn-silicate, the selectivity to aromatics increased with increasing reaction temperature up to 600℃ and decreased with further increase of reaction temperature. It has been also found that HZSM-5 and Ga-silicate bifunctional catalysts ion-exchanged with Pt, Zn, Ni and Ga are more active and selective than HZSM-5 and Ga-silicate.
