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论文类型：期刊论文

发表时间：2013-02-26

发表刊物：APPLIED CATALYSIS A-GENERAL

收录刊物：SCIE、EI

卷号：453

页面范围：272-279

ISSN号：0926-860X

关键字：Titanium silicalite-1; Organic base; Recrystallization; Hydroxylation of phenol; Modification

摘要：Small-crystal titanium silicalite-1 (TS-1) with a crystal size of about 600 nm x 400 nm x 250 nm, was treated with different organic bases, including ethylamine, diethylamine, tetramethyl ammonium hydroxide, tetrapropyl ammonium hydroxide and tetrabutyl ammonium hydroxide. The treated TS-1 was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet-visible diffuse reflectance spectrum (UV-vis), X-ray photoelectron spectrum (XPS), n-hexane and cyclohexane physical adsorption, nitrogen physisorption, inductive coupled plasma emission (ICP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Modification with different bases led to different molar ratios of Si/Ti on the external surface, according to the XPS data. The TEM images showed that many irregular hollows were generated during modification, due to the random dissolution of framework silicon and titanium. The dissolved amorphous silica and titania recrystallize on the external surface of the TS-1 crystals in the presence of template, and different axis-oriented recrystallization occurred for different templates. Tetrapropyl ammonium favored a-orientation and tetrabutyl ammonium favored b-orientation. Especially the modification with tetrapropyl ammonium hydroxide improved the catalytic properties of small-crystal TS-1 for the hydroxylation of phenol. The conversion of phenol reached 32.6% over small-crystal TS-1 modified with 0.06 mol/L tetrapropyl ammonium hydroxide for 72 h. (C) 2013 Elsevier B.V. All rights reserved.