Particle formation in the hydrolysis of tetraethyl orthosilicate in pH buffer solution
Particle formation in the hydrolysis of tetraethyl orthosilicate in pH buffer solution
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DOI：
10.1016/j.jcis.2004.06.041
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发表时间：
2004-11-01
影响因子：
9.9
通讯作者：
Konno, M
中科院分区：
文献类型：
--
作者：
Nagao, D;Osuzu, H;Konno, M
通过在 5 mol/m(3) CH3COOH 存在下使用碱性催化剂 NH3、甲胺 (MA) 和二甲胺 (DMA) 改变 pH (9.5-11)，研究了原硅酸四乙酯 (TEOS) 水解和缩合过程中的颗粒形成，选择催化剂是为了抑制反应过程中 pH 和离子强度的时间变化。 MA 和 DMA 在催化剂浓度为 0.02-0.2 kmol/m(3) 时形成球形颗粒，而 NH3 在催化剂浓度为 0.1-1.5 kmol/m(3) 时形成球形颗粒。在形成球形颗粒的常见催化剂浓度范围内，DMA 的平均颗粒尺寸最大，NH3 的平均颗粒尺寸最小。 TEOS 的水解速率可以通过使用缓冲系统来量化，作为 TEOS 和 OH- 浓度的函数。未发现水解与粒径之间存在特定关系。在反应溶剂中测量的二氧化硅颗粒的 zeta 电位的顺序为 DMA < MA < NH3，根据反应中的 pH 值估算的离子强度的顺序为 DMA 与 MA > NH3 一致。这表明颗粒尺寸是由静电颗粒相互作用控制的。 (C) 2004 Elsevier Inc. 保留所有权利。
Particle formation in the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) was studied by varying pH (9.5-11) with the basic catalysts NH3, methylamine (MA), and dimethylamine (DMA) in the presence of 5 mol/m(3) CH3COOH, which was chosen to suppress time variations of pH and ionic strength during the reaction. Spherical particles were formed for MA and DMA at catalyst concentrations of 0.02-0.2 kmol/m(3) and for NH3 at catalyst concentrations of 0.1-1.5 kmol/m(3). In a common range of catalyst concentrations for spherical particle formation, average particle size was largest for DMA and smallest for NH3. Hydrolysis rate of TEOS Could be quantified by the use of buffer systems as a function of TEOS and OH- concentrations. A specific relation was not found between the hydrolysis and the particle size. The zeta potential of silica particles measured in the reaction solvent was in the order DMA < MA < NH3, and ionic strength, estimated from pH in the reactions, was in the order DMA congruent to MA > NH3. This Suggested that the particle sizes were controlled by electrostatic particle interactions. (C) 2004 Elsevier Inc. All rights reserved.