Coeffect of Na+ and Tetrapropylammonium (TPA+) in Alkali Treatment on the Fabrication of Mesoporous ZSM-5 Catalyst for Methanol-to-Hydrocarbons Reactions
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- 作者：Weili Wan ; Tingjun Fu ; Ruiyue Qi ; Juan Shao ; Zhong Li
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2016
- 出版时间：December 28, 2016
- 年：2016
- 卷：55
- 期：51
- 页码：13040-13049
- 全文大小：619K
- ISSN：1520-5045
文摘
This investigation focused on the study of formation mechanism for highly mesoporous ZSM-5 under the introduction of tetrapropylammonium hydroxide (TPAOH) during NaOH treatment. Determined based on N2 sorption, transmission electron spectroscopy, scanning electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, and 29Si magic-angle spinning nuclear magnetic resonance characterizations, increased mesoporosity, crystallinity, and surface integrity for the desilicated ZSM-5 were found after TPAOH introduction. This protective effect of tetrapropylammonium (TPA+) on desilication was reflected by increased surface SiO2/Al2O3 ratios with increased concentrations of TPA+. TPA+ was first confirmed to be mainly adsorbed on the Si(4Si, 0Al) sites to provide a protective effect. Na+ played an indispensable role in the induced desilication during alkali treatment. The co-effect of protective desilication from TPA+ and preferential desilication near Na+ on the surface accounts for the formation of ZSM-5 with high mesoporosity. Contributing to larger external surfaces, the TPAOH-aided desilicated sample possessed a longer methanol-to-hydrocarbons lifetime of 102 h, twice that of ZSM-5 treated by traditional NaOH treatment.