Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (01): 33-37.doi: 10.3866/PKU.WHXB20050107

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The Local Structure of Titania-Silica Composite Oxides

YANG Xiao-Guang;DONG Peng;ZHOU Ya-Song;LIU Tao;ZHANG Jing;XIEYa-Ning;HU Tian-Dou   

  1. State Key Laboratory of Heavy Oil Processing, Beijing University of Petroleum, Bejing 102249;Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039
  • Received:2004-06-23 Revised:2004-08-19 Published:2005-01-15
  • Contact: DONG Peng E-mail:p.dong@china.com

Abstract: By analyzing the X-ray absorption spectra of Ti K edge, the structural information of TiO2-SiO2 composite oxides prepared by sol-gel (CTS1, CTS4), impregnation (SYB02, SYB04, SYB06), and CVD (CVD1, CVD2)methods were obtained.TiO2 was most dispersed in SiO2 by the sol-gel method and TiO2 was least dispersed in SiO2 by the CVD method. The pre-edge structure of anatase (Ti K edge of XAFS) is characteristic of three peaks: A1, A2, and A3. For the sol-gel and impregnation prepared TiO2-SiO2 supports, the structure of Ti K edge is different from that of anatase. The intensity of A2 peak increases with the decrease of the content of Ti, and coordination numbers of the first shell of Ti-O increase with the increase of the content of Ti. The pre-edge absorption feature of TiO2-SiO2 prepared by CVD is consistent with that of anatase, and the coordination number of the first shell is nearly to 6. The bond lengths of the first shell of Ti-O increase with the increasing Ti content. The results were confirmed by further measurement using XRD. Based on the experimental results, a model of titania-silica composite oxide was proposed.

Key words: XAFS(X-ray absorption fine structure), TiO2-SiO2, Sol-gel,  Impregnation, CVD, Catalyst