关键词: 轻烃, 芳构化, ZSM-5, 反应机理

Abstract: In this work, two major pathways of light alkane aromatization, including alkane activation and alkene aromatization, was reviewed. The Haag-Dessau mechanism and classical cracking mechanism of alkane activation by Brnsted acid sites of catalysts were introduced. Alkanes are mainly activated by the Haag-Dessau mechanism at low conversion, high reaction temperature and low reactant partial pressure. The activation process of alkanes over Lewis acid sites was described. The process is consistent with the characteristics of synergistic activation by Brønsted acid and Lewis acid. The reaction mechanisms of oligomerization, cracking and cyclization during the aromatization of olefins were introduced respectively. These reactions are completed with aromatization on the Brønsted acid site, owing to the formation carbenium species. Due to the steric hindrance of channels of zeolites, oligomers of large size are difficult to be generated. The β cracking rate depends on the charge of β-C atoms after isomerization. Under the same coordination condition, the β cracking rate is increasing along with the increase of charge amount. As for the cyclization reaction, both 1,6 ring closure and 1,5 ring closure reaction may occur, and the way of cyclization is determined by the type of alkoxide complex. Finally, the development direction of light alkanes aromatization mechanism is prospected.

Key words: alkane, aromatization, ZSM-5, reaction mechanism