Abstract: The nanoscale HZSM-5(20—50nm) catalyst was prepared, and characterized by XRF, TEM, NH₃-TPD and so on. The performance of the nanoscale HZSM-5 catalysts for conversion of n-octane, the mixture of n-octane and benzene was evaluated. The transformation behavior of both single and mixing hydrocarbons as the model reactants over the nanoscale HZSM-5 catalyst was investigated, the influences of the reaction conditions on product distribution were investigated, and reaction mechanism was also studied. The results indicate that the nanoscale HZSM-5 catalyst exhibits a higher ability to convert hydrocarbons, and the hydrocarbons were converted mainly into aromatics and iso-paraffins which have a high octane value by isomerization, aromatization, alkylation reactions and so on, as a result, the total amount of the iso-paraffins(C₄—C₆)and aromatics in products was above 90%(mass fraction). The aromatization from single hydrocarbons mainly produced benzene via dehydrocyclization process, whereas the aromatization from the mixing hydrocarbons formed alkyl-aromatics mostly by alkylation of benzene and small molecule hydrocarbons. The formation of benzene and C⁺₉ could be restrained by regulating the reaction conditions. The analysis of the products shows that the cracking, aromatization and isomerization reaction of hydrocarbons such as octane and benzene-n-octane over the nanoscale HZSM-5 catalyst followed the carbonium ion mechanism.

Key words: Nanoscale HZSM-5 zeolite, n-Octane, Benzene, Isomerization, Aromatization, Alkylation