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Indexed by:期刊论文

Date of Publication:2014-10-01

Journal:CHEMICAL ENGINEERING JOURNAL

Included Journals:SCIE、EI、Scopus

Volume:253

Page Number:464-471

ISSN No.:1385-8947

Key Words:TS-1; TS-1/SiO2 extrudate; Transformation; TPAOH treatment; Propylene epoxidation

Abstract:Titanium Silicalite-1 (TS-1)/SiO2 extrudates were treated with tetrapropylammonium hydroxide (TPAOH) solutions under hydrothermal conditions. The catalysts were characterized using various analysis techniques including X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis), UV Raman, X-ray photoelectron spectroscopy (XPS), nitrogen physisorption, X-ray fluorescence (XRF), Si-29 magic-angle-spinning nuclear magnetic resonance (Si-29 MAS NMR) spectroscopy, and transmission electron microscopy (TEM). The transformation of amorphous SiO2 in TS-1/SiO2 catalysts during TPAOH treatment was studied in detail. The results show that the SiO2 dissolved and then crystallized during TPAOH treatment, which increased the hydrophobicity and the ratio of Si/Ti on the external surface of TS-1. Moreover, the existence of SiO2 inhibited the formation of anatase TiO2 during TPAOH treatment. The changes in physical and chemical properties not only improved the catalytic activity but also improved the stability of catalysts after TPAOH treatment. The experimental results show that the treated TS-1/SiO2 catalysts exhibited higher catalytic activity and stability than the untreated counterparts. Especially for the TS-1/SiO2 catalyst treated with 0.06 mol/L TPAOH solution for 72 h, the H2O2 conversion still remained above 90% and the propylene oxide selectivity was as high as 99% after a long-term run with time on stream (TOS) of 648 h. (C) 2014 Elsevier B.V. All rights reserved.