Aromatization of n-Hexane Over H-ZSM-5 and Metal (Mo, Ga, Zn) Modified H-ZSM-5 Zeolite Catalysts of Different Crystallinity

Aromatic compounds are a major component of the chemical industry, and hence the aromatization reactions of light hydrocarbons have attracted significant interest. In this study, we investigate the influence of the crystallinity of the H-ZSM-5 zeolites on the aromatization of n-hexane. The aromatization of n-hexane was studied over H-ZSM-5 Ga/H-ZSM-5, Zn/H-ZSM-5, and Mo/H-ZSM-5 catalysts, with H-ZSM-5 having different %XRD crystallinity between 17 and 86%. The SiO2/Al2O3 ratio was kept constant at 35. The 2wt.% metal-modified H-ZSM-5 catalysts were prepared by the incipient impregnation method and calcined at 500 °C. Aromatization reactions were carried out at 500 °C. BET, FTIR XRD, SEM, NH3-TPD, and XRD were used for the characterization of the catalysts in a preliminary attempt to correlate the structure and catalytic behaviour. The results on the effect of the percentage of XRD crystallinity (from 17 to 86%) of H-ZSM-5 on the activity of H-ZSM5 modified by loading 2 wt.% of metal showed that the conversion of n-hexane increased with %XRD. The Ga/H-ZSM-5 and Zn/H-ZSM-5 catalysts with% XRD greater than 30% were more aromatic selective than the Mo/H-ZSM-5 catalysts. Mo/H-ZSM-5 catalysts were more selective to cracked products due to the absence of the dehydrogenation activity possessed by gallium and zinc metals.