Abstract: The effects of steaming and impregnation with transition metal (Ni, Co, Cu, Zn) salt solution on the catalytic performance of nano-sized HZSM-5 zeolite catalysts for the aromatization ofC5-C8alkane mixture were studied in a small fixed-bed reactor. The surface acidity of the modified zeolite catalysts was characterized by NH3-TPD and Py-FT-IR, and the surface acidity was correlated to the aromatization performance. The results showed that steaming treatment at 450 ℃ could notably increase the selectivity for aromatization over the zeolite catalysts, and less methane and ethane were produced. The impregnation of the steamed nano-sized HZSM-5 zeolite with copper or zinc nitrate solution significantly strengthened its resistance to coking deactivation. It was because that steaming treatment decreased both the amount and strength of acid sites on the zeolite surface, while the impregnation with copper or zinc nitrate solution further decreased Brnsted acid sites, increased Lewis acid sites, and generated active dehydrogenation sites by cooperating with Brnsted acid sites, thereby made an impact on both the activation way and the aromatization path of the alkane mixture.

Key words: C5-C8 alkane mixture, aromatization, HZSM-5 zeolite, steaming, impregnation, transition metal