Acta Chimica Sinica ›› 2004, Vol. 62 ›› Issue (1): 22-27. Previous Articles     Next Articles

29Si NMR研究Stöiber反应的化学动力学

刘瑞丽1, 徐耀1, 李志宏1, 吴东1, 孙予罕1, 高红昌2, 袁汉珍2, 邓风2   

  1. 1. 中国科学院山西煤炭化学研究所, 煤转化国家重点实验室, 太原, 030001;
    2. 中国科学院武汉物理与数学研究所, 波谱与原子分子物理国家重点实验室, 武汉, 430071
  • 收稿日期:2003-06-02 修回日期:2003-09-01 出版日期:2004-01-14 发布日期:2014-01-26
  • 通讯作者: 孙予罕;Tel.:0351-4084072;Fax:0351-4041153.
  • 基金资助:

Liquid-state 29Si NMR Study on the Chemical Kinetics of Stöiber Synthesis

LIU Rui-Li1, XU Yao1, LI Zhi-Hong1, WU Dong1, SUN Yu-Han1, GAO Hong-Chang2, YUAN Han-Zhen2, Deng Feng2   

  1. 1. State Key Laboratory of Coal Conversion, Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001;
    2. State Key Laboratory of Magnetic Resonance & Atomic & Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071
  • Received:2003-06-02 Revised:2003-09-01 Online:2004-01-14 Published:2014-01-26

Stöber syntheses, the ammonia-catalyzed reactions of tetraethoxysilane with water in low molecular weight (MW) alcohols, produce highly monodisperse, spherical silica nanoparticles with size ranging from 5 to 2000 nm. It is the initial hydrolysis and polycondensation process that have been investigated by liquid-state 29Si NMR. We found that the intermediate species was Q01; the reaction equation of the rate-determining step was r=kh[TEOS]·[NH3]0.457[H2O]0.051; the constant value was kh=7.32×10-3 mol-0.5·dm1.5·min-1 (T=25℃). In the meantime, the reaction rate constant values of those non-rate-determining steps by using the transition state theory were calculated, and the values of the activation energy and the Arrhenius constant were also derived. The results suggested that the reaction rates of the hydrolysis and condensation become faster with increasing the temperature, and the rate constant value of the rate-determining step increases larger than that of non-rate-determining step, indicating that high temperature is more favorable for the hydrolysis of TEOS. The molar ratios of H2O/TEOS and NH 3/TEOS were adjusted to examine the effect of H2O and NH 3 and we found that the reaction rates of hydrolysis and condensation of TEOS largely depended on the concentration of NH 3 but not that of H2O.

Key words: kinetics, 29Si NMR, Stöber synthesis, sol-gel