Synthesis and catalytic performance of hierarchical MCM-22 zeolite aggregates with the assistance of carbon particles and fluoride ions

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• 作者：Jianhua Yang ; Jun Chu ; Jinqu Wang ; Dehong Yin ; Jinming Lu ; Yan Zhang
• 关键词：Methane dehydroaromatization ; MCM-22 zeolite ; Hierarchical pore ; Fluoride route ; Catalytic performance
• 刊名：Chinese Journal of Catalysis
• 出版年：January, 2014
• 年：2014
• 卷：35
• 期：1
• 页码：49-57
• 全文大小：1040 K

文摘

Hierarchical MCM-22 zeolite aggregates (MCM-22-FC) were prepared by one-pot hydrothermal synthesis with the assistance of carbon particles and fluoride ions. The effects of carbon particles and fluoride ions on the morphology and catalytic properties of the MCM-22 zeolite were investigated. The hierarchical MCM-22-FC zeolite aggregates were constructed by intergrown and stacked thin MCM-22 lamellas and possessed macro-/mesopores and inherent micropores. The MCM-22-FC zeolite was modified to form the Mo/MCM-22-FC catalyst, which exhibited an improved benzene yield and aromatic selectivity as well as catalyst life in the methane dehydroaromatization (MDA) reaction. Based on NH₃-TPD and pyridine-Fourier transform infrared spectroscopy measurements together with thermogravimetric analysis, we found that the improved MDA catalytic performance of Mo/MCM-22-FC resulted from the formation of more active MoC_x or MoO_xC_y species that evolved from increased amounts of Br枚nsted acids with the assistance of fluoride ions. This promoted the diffusion of large molecule products because of the thin MCM-22 lamellas. Less excess Br枚nsted acid sites were retained in the Mo/HMCM-22-FC catalyst because the formation of active centers inhibited the formation of coke, which contributed to its improved aromatic selectivity