Influence of initial Si/Al ratios on the structural, acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors
Thông tin tác giả: TS. Vũ Xuân Hoàn, nghiên cứu viên của Nhóm DEMASTED thuộc Trường Đại học Tôn Đức Thắng
Tên bài báo: Influence of initial Si/Al ratios on the structural, acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors
Thông tin tạp chí: Bài báo được công bố trên tạp chí ISI Journal of Porous Materials (impact factor là 1.624 theo ISI và chỉ số H-index là 43 theo SJR).
Tóm tắt: Nano-ZSM-5/SBA-15 analog composites (ZSC) were prepared in a two-step process from ZSM-5 precursors with different Si/Al molar ratios (10–50) via high-temperature synthesis in mildly acidic media (200 °C, pH 3.5) aiming to evaluate the influence of the initial Si/Al ratio on their structural, acidic and catalytic properties. The resulting materials were characterized by SAXS, XRD, FTIR, TEM, N2 sorption, 27Al solid state-NMR, NH3-TPD, FTIR spectroscopy of adsorbed pyridine, AAS and ICP-AES. Under the applied synthesis conditions, a ZSC material with controlled distribution of nano-ZSM-5 and SBA-15 analog phases can be prepared from ZSM-5 precursors by adjusting the initial Si/Al ratio in the range of 20–30. Increasing the initial Si/Al ratio to 50, only ZSM-5 nanocrystals were obtained whereas reducing the initial Si/Al ratio to 10 led to the formation of a disordered mesoporous SBA-15 analog. The total acidity increases with the crystallinity of the ZSM-5 phase as varying the Si/Al ratio from 10 to 30 despite the decreased amount of incorporated aluminum. However, the acidity declines slightly when raising the Si/Al ratio to 50 because of the low incorporated aluminum. The catalytic performance of the ZSC materials compared to the reference materials, i.e. purely mesoporous Al-SBA-15 and purely microporous H-ZSM-5 was assessed in the gas phase cracking of cumene and 1,3,5-tri-isopropylbenzene (TIPB) as test reactions. The results show that a balanced ratio of nano-ZSM-5 and SBA-15 analog phases obtained by tuning the initial Si/Al ratio is crucial to achieve superior catalytic performance of the ZSC materials in the cracking of both cumene and TIPB.
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