Gaseous Phase Silica Generation

Abstract

Commercialized silica is commonly produced from the hydrolysis of tetraethoxysilane TEES (or tetraethyl orthosilicate (TEOS)) via the sol-gel method. This method is a liquid phase process that requires the use of catalyst (usually acid) and solvent (mostly ethanol). Herein gaseous phase hydrolysis of TEES should be a promising process to produce silica without catalyst use. Therefore, we focus on the gaseous phase hydrolysis of TEES to produce amorphous silica. In general, the particle size of produced silica is one of the most important factors for its application. In the gaseous phase hydrolysis, the size and size distribution of silica particles might depend on the experimental conditions (geometry of the experiment device, temperature and flow rates of reactants). In the present study, we used two shapes of the reaction tube (reactor), reactor type 3 and reactor type 4. We also increased the temperature and the water steam flow rate. The results showed that with similar conditions of temperature and water steam flow rate, the particles synthesized inside the reactor type 4 (absence of back-flow) were smaller than those obtained inside the reactor type 3 (presence of back-flow). The increase of temperature and/or water steam flow rate accelerated the nuclei formation and inhibited their cohesion. In summary, the silica particle size tended to be smaller with temperature and water steam flow rate increase.