Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (08): 1933-1940.doi: 10.3866/PKU.WHXB20110829

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Effects of Heat Treatment on the Structure and Properties of the Tungstophosphoric Acid-Modified Zirconia Aerogel Solid Acids

LIANG Li-Ping1,2, ZHU Qing1, ZHAO Yong-Xiang1, LIU Dian-Sheng1   

  1. 1. Engineering Research Center for Fine Chemicals of Ministry of Education, School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, P. R. China;
    2. School of Materials Science and Engineering, Taiyuan University of Science and Technology, Taiyuan 030024, P. R. China
  • Received:2011-01-30 Revised:2011-05-23 Published:2011-07-19
  • Contact: ZHAO Yong-Xiang, LIU Dian-Sheng E-mail:yxzhao@sxu.edu.cn; dshliu@sxu.edu.cn
  • Supported by:

    The project was supported by the Scientific and Technological Project of Shanxi Province, China (20090321059) and Industrial Technology Development Project of Development and Reform Commission of Shanxi Province, China (2009164).

Abstract:

Based on detailed experimental results, the effects of heat treatment on the structure, acidity, and catalytic performance of the 12-tungstophosphoric acid (TPA) modified zirconia aerogel (ZA) (TPZA) solid acids were investigated. TPZA samples, with TPA mass fraction of 25% and heat-treated at 120- 750 °C, were characterized by N2 physical adsorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, FTIR spectroscopy of adsorbed pyridine (Py-FTIR), and temperature programmed desorption of NH3 (NH3-TPD). And they were used as catalysts in the polymerization of tetrahydrofuran (THF). The results show that, although the heat treatment might greatly influence both the surface density and type of tungsten species, the TPZA materials with the TPA loading of 25% could acquire suitable Brönsted and Lewis acidity and accordingly acceptable catalytic activities over the wide temperature ranges of 120-300 °C and 550-750 °C. In the TPZA samples treated at 120-300 °C, the presence of Brönsted acid sites can be associated with the presence of highly dispersed and somewhat distorted but intact Keggin-anions, whereas the Brönsted acid sites in the samples treated at 550-750 °C might originate from the zirconia-anchored, highly polymerized tungstate surface species. Moreover, all the samples show obvious Lewis acidity, which is associated with the presence of coordinatively unsaturated Zr4+ and phosphorous oxide produced by the decomposition of TPA.

Key words: Zirconia aerogel, Tungstophosphoric acid, Polytungstate, Tetrahydrofuran, Polymerization

MSC2000: 

  • O643.3