物理化学学报 >> 2011, Vol. 27 >> Issue (08): 1933-1940.doi: 10.3866/PKU.WHXB20110829

催化和表面科学 上一篇    下一篇

热处理过程中磷钨杂多酸修饰ZrO2气凝胶固体酸的结构及性能演变

梁丽萍1,2, 朱晴1, 赵永祥1, 刘滇生1   

  1. 1. 山西大学化学化工学院, 精细化学品教育部工程研究中心, 太原 030006;
    2. 太原科技大学材料科学与工程学院, 太原 030024
  • 收稿日期:2011-01-30 修回日期:2011-05-23 发布日期:2011-07-19
  • 通讯作者: 赵永祥, 刘滇生 E-mail:yxzhao@sxu.edu.cn; dshliu@sxu.edu.cn
  • 基金资助:

    山西省科技攻关计划项目(20090321059)和山西省发改委产业技术开发项目(2009164)资助

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).

摘要:

基于N2物理吸附、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、吸附吡啶红外(Py-FTIR)光谱、氨程序升温脱附(NH3-TPD)等物理化学表征及催化四氢呋喃(THF)聚合反应实验结果, 探讨了120-750 °C空气气氛热处理对磷钨杂多酸(TPA)修饰ZrO2气凝胶(ZA)(TPZA)固体酸结构、酸性质及酸催化性能的影响. 研究发现, 对于固载量(TPA质量分数)为25%的TPZA材料, 随热处理温度升高, ZrO2表面发生了Keggin-杂多阴离子结构畸变、杂多阴离子分解、低聚合度表面多钨酸根物种形成以及多钨酸根物种沿载体表面二维方向聚合的钨物种演变过程; 材料相应地经历了其Brönsted酸性及酸催化活性失而复得的变化. 在实验考察范围内, 材料明显的Brönsted酸性及催化THF聚合反应活性发生在120-300 °C及550-750 °C两个热处理温度段. 其间, 材料的Brönsted酸性分别源于与Keggin-杂多阴离子及在载体表面二维方向上具有一定聚合度的聚钨物种相联系的酸性质子. 在350-450 °C处理温度范围内, 绝大多数Keggin-杂多阴离子的分解及钨物种沿载体表面方向聚合度的不足使得样品中难以形成明显数量的Brönsted酸中心. 此外, 在实验考察的整个温度范围内, 材料显示明显的Lewis酸性, 这应该与样品表面存在配位不饱和的Zr4+阳离子及磷的氧化物有关.

关键词: 二氧化锆气凝胶, 磷钨杂多酸, 多钨酸根, 四氢呋喃, 聚合

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