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以碳黑为第二模板剂在氟离子体系中一步水热合成了多级结构MCM-22分子筛组装体(简称为MCM-22-FC).考察了碳黑和氟离子对MCM-22分子筛形貌和催化性能的影响.MCM-22-FC分子筛是由大量片状晶体交错生长形成的组装体结构,其中MCM-22的片层结构更薄,在其固有的微孔中存在的晶间孔呈现大孔和介孔的特征.MCM-22-FC负载Mo后得到的Mo/MCM-22-FC催化剂在甲烷无氧芳构化反应(MDA)中提高了苯收率和芳烃选择性,并且提高了催化剂的寿命.通过氨气程序升温脱附(NH3-TPD)表征,吡啶红外(Py-IR)表征,结合热重(TG)分析,得出的结论是Mo/MCM-22-FC在MDA中优越的催化性能是由于氟离子进入到分子筛骨架当中,形成具有拉电子效应的结构单元,从而提高了分子筛的Br鰊sted酸量,较多的Br鰊sted酸性位将更多的Mo物种迁移至分子筛孔道内部,形成更多的MoCx或MoOxCy活性物种以及更有利于大分子产物扩散的MCM-22薄片层的结构.少量过剩的Br鰊sted酸性位在成型后保留在Mo/HMCM-22-FC催化剂活性中心抑制了积碳的形成,也有助于改善芳烃的选择性.
MCM-22 molecular sieve assembly (abbreviated as MCM-22-FC) was synthesized by one-step hydrothermal synthesis in a fluoride ion system using carbon black as the second template. The effects of carbon black and fluoride on the molecular sieve morphology of MCM-22 Morphology and catalytic properties of MCM-22-FC molecular sieve is a large number of lamellar crystals formed by the staggered growth of the assembly structure, which MCM-22 lamellae structure thinner, in its inherent micropores exist in the intercrystalline pores Showing the characteristics of macropores and mesopores.The Mo / MCM-22-FC catalyst obtained after the MCM-22-FC was loaded with Mo increased the benzene yield and aromatic selectivity in methane anaerobic aromatization (MDA) (NH3-TPD) characterization, Py-IR characterization and thermogravimetry (TG) analysis. The conclusion is that Mo / MCM-22-FC The superior catalytic performance of MDA is due to the fluoride ions entering the framework of the molecular sieve to form the structural unit with the pulling electron effect, thereby increasing the Br sted acid amount of the molecular sieve. More Bromo sted acidic sites will more Mo species Migration into the molecular sieve pore to form more active species of MoCx or MoOxCy and more conducive to the proliferation of macromolecular products MCM -22 lamellae structure. A small excess of Brøsted acid sites retained the active site in the Mo / HMCM-22-FC catalyst after forming, inhibiting the formation of coke and also aiding the aromatics selectivity.