Synthesis of spherical silica particles from sodium silicate in spinning disk reactor

• Main Authors: Hsiao-Han Peng, 彭筱涵
• Other Authors: Yi-Feng Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/97153012639369880993

碩士 === 中原大學 === 化學工程研究所 === 102 === Silica particles with narrow size distribution, structurally controlled size and shape showed great potential in daily life and industry. Due to the particles’ great properties in optics, mechanic and thermodynamic. Various methods for synthesis of SiO2 particles have been developed, including reactive precipitation, chemical vapor deposition, spraying, microemulsion and sol-gel method, etc. The monodisperse silica is usually produced by sol-gel method using TEOS (Tetraethyl Orthosilicate). However, the process is costly and involves toxic silicon alkoxide precusors. In attempted to reduce processing cost and time, this work used sodium silicate to prepare silica particles. Spinning disk reactor (SDR) combined with sol-gel method and precipitation process to synthesize uniform and narrow sized silica particles because SDR provides a high micro-mixing efficiency. The effect of operating variables on the particle size, shape and product yield in a batch system and a continuous higee system were investigated, respectively. In batch system, operating variables included the amount of ethanol, pH value, reactant concentration and the time of sodium silicate solution contacting with ethanol. In higee system, the effect of reactant flow rate, the time of sodium silicate solution contacting with ethanol, rotation speed were studied. Experimental results show that the more spherical particles and higher yields were achieved in the slurry at pH9. Increasing the amounts of ethanol resulted in higher yields but has no influence in particle size. The particle size and yields obviously increased with increasing the concentration of sodium silicate and the time of sodium silicate solution contacting with ethanol. In higee system, increasing total reactant flow rate resulted in higher product rate, but it has no influence in yields. At lower total reactant flow rate resulted in the regular particle shape. Increasing rotation speed leads to a decrease of particle size, but it has no effect on yields. The silica products obtained from the SDR have a narrow particle size distribution and a small average particle diameter compared with those a batch stirred tank . At the optimal condition, spherical silica particles with particle size of 150 nm and yield of 54% were obtained in a SDR.