Kinetics of formation of monodisperse colloidal silica particles through the hydrolysis and condensation of tetraethylorthosilicate
Kinetics of formation of monodisperse colloidal silica particles through the hydrolysis and condensation of tetraethylorthosilicate
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DOI：
10.1021/ie9602217
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发表时间：
1996-12-01
影响因子：
4.2
通讯作者：
Yang, JJ
中科院分区：
文献类型：
--
作者：
Chen, SL;Dong, P;Yang, JJ
用气相色谱和电导仪分别测定正硅酸乙酯(TEOS)和硅酸的浓度，研究了正硅酸乙酯(TEOS)在均匀二氧化硅颗粒形成过程中的水解和缩合动力学。结果表明，正硅酸乙酯的水解反应和氢氧化硅的缩合反应分别与正硅酸乙酯和氢氧化硅反应均为一级反应，并测定了反应速率常数与反应温度、NH3浓度和H2O浓度的关系。此外，还研究了颗粒生长速率与水解和缩合动力学的关系。实验表明，在大部分反应过程中，生成的颗粒数量少于消耗的TEOS数量，说明在二氧化硅生成过程中存在反应中间体。在Stober过程的早期阶段，反应中间产物包括硅酸和亚颗粒，而在没有形成新颗粒的种子生长实验中或在Stober过程的早期阶段之后，反应中间产物主要由硅酸组成，二氧化硅的生长速率等于硅酸的缩合速率。
Kinetic studies of the hydrolysis and condensation of tetraethylorthosilicate (TEOS) during the formation of uniform silica particles were performed through determining concentrations of TEOS and silicic acid by means of gas chromatography and a conductometer, respectively. It was shown that both hydrolysis of TEOS and condensation of Si(OH)(4) are first order with TEOS and Si(OH)(4), respectively, and the relationships of the hydrolysis and condensation rate constants with reaction condition variables, such as temperature, NH3 concentration, and H2O concentration, were determined. In addition, the particle growth rate was investigated with relation to the hydrolysis and condensation kinetics. Experiments showed that, during most of the reaction, the amount of formed particles is less than that of consumed TEOS, indicating that reaction intermediates exist during the process of silica formation. In the early stages of the Stober process, the reaction intermediates include silicic acid and subparticles, while in the case of seed growth experiments without the formation of new particles or after the early stages of Stober process, the reaction intermediates primarily consist of silicic acid and the growth rate of silica equals the rate of silicic acid condensation.