旋轉盤反應器中以矽酸鈉合成二氧化矽球形微粒之研究

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

彭筱涵(Hsiao-Han Peng)

指導教授 ： 林義峯 ； 陳昱劭

中原大學/工學院/化學工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400770

摘要

二氧化矽在工業和日常生活扮演著重要的角色，由於其具有優良的光學性、力學性質及熱性能，而有廣泛的應用範圍。目前常見製備二氧化矽的方法有反應沉澱法、化學氣相沉積法、噴霧法、微乳液法、溶膠-凝膠法等。一般製備單一懸浮奈米二氧化矽粒子皆以TEOS(Tetraethyl Orthosilicate)為原料，由於TEOS成本較高，反應過程又較為費時且前驅物矽醇鹽(silicon alkoxide)涉及對人體有毒性危害的問題。因此本次實驗選用成本較低且原料充足的矽酸鈉(Na2SiO3)為前驅物來製備二氧化矽粒子。
本研究利用旋轉盤反應器結合溶膠-凝膠法之沉澱程序來製備二氧化矽顆粒，期望以高速旋轉盤提供一個良好的微觀混合的反應系統，而得到形狀及粒徑分佈均一的二氧化矽顆粒。
實驗中分別探討批次式攪拌系統及超重力系統中各操作參數對二氧化矽粒子大小、形貌及產率的影響。於批次式系統中探討反應後漿液之pH值、反應物濃度、乙醇與矽酸鈉溶液接觸時間對顆粒的形貌及產率的影響，並探討乙醇在反應中扮演的角色。於超重力系統中探討旋轉盤轉速、反應物進料流率、反應物進料總流率對二氧化矽顆粒大小及形貌的影響，同時也比較批次式反應器與旋轉盤反應器所製備出二氧化矽奈米顆粒的差異。
實驗結果顯示，反應後漿液在pH= 9時能夠得到較佳的顆粒形貌及產率；乙醇量增加對平均粒徑沒有太大影響，但產率會大幅上升；隨著起始反應物濃度提高及增加乙醇與矽酸鈉溶液接觸時間，二氧化矽平均粒徑及產率皆明顯增加。超重力系統中增加反應液總流率不會影響產率，而會增加產量，顆粒形貌則為反應液總流率低時較佳；轉盤轉速增加能夠得到較小的平均粒徑，對產率沒有影響。而旋轉盤反應器得到比批次式反應器明顯較窄的粒徑分佈和較小的平均粒徑。於旋轉盤反應器內的最佳條件下可得到粒徑分佈窄且平均粒徑為150nm、產率為54%的球形二氧化矽粉體。

關鍵字

矽酸鈉 ； 旋轉盤反應器 ； 二氧化矽

並列摘要

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.

並列關鍵字

sodium silicate ； spinning disk reactor ； silica

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