Are olefin aromatization reactions structure sensitive over Al pairs and single Al in H-ZSM-5 Zeolite?. (1st February 2023)

• Record Type: Journal Article
• Authors: Xing, Mengjiao; Chen, Yunlei; Cao, Jian; Han, Yuanlong; Tao, Zhichao; Wang, Fei; Hao, Kun; Zhang, Ling; Zheng, Wentao; Xiang, Hongwei; Yang, Yong; Li, Yongwang; Wen, Xiaodong
• Is Part Of: Fuel. Volume 333(2023)Part 2
• Publication Date: 2023-02-01
• Subjects: H-ZSM-5 zeolite -- Olefin aromatization -- Al pairs -- Single Al -- Activation temperature -- Brønsted acid; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.126541
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: The acid strength for Al pairs and single Al are similar. The Al pairs content has small effect on aromatization at high temperature. Al pairs can be activated at around 100 ℃, lower than single Al (about 150 ℃). The desorption of big products is critical for the catalytic cycle sustainable. Abstract: Understanding the catalytic structure–activity relationship over active sites is of fundamental importance in heterogeneous catalysis field. Herein, a series of H-ZSM-5 zeolites with Al pairs contents in the range of 31% to 82% are used to explore the structure sensitivity of olefin aromatization reaction. Compared with high reaction temperatures (385 ℃ and above), prominently different initial aromatic yields are observed over the samples at 150 ℃. In addition, the 1-octene temperature-programmed surface reaction (TPSR) and theoretical calculation results give a thorough understanding on active site dependent activation temperature (100 vs 150 ℃ over Al pairs and single Al). However, the catalytic cycle of olefin aromatization is not sustainable at low reaction temperature, which is due to the formation and blocking of big molecules in the micropores (e.g., trimethylbenzene etc.). In conclusion, the desorption of big molecules is the rate-determining step for olefin aromatization reaction over H-ZSM-5, which masks the structure sensitivity over Al pairs and single Al.