The By-product Of Polycrystalline Silicon-Silicon Tetrachloride: Utilization Resourcefully And Application For Camellia Oil Refining

With the development of the polycrystalline silicon industry, it becomes a problem to dispose the silicon tetrachloride (SiCl₄) by-product generated in the polycrystalline silicon industry harmlessly and utilize it resourcefully. This thesis is to discuss the issue of using silicon tetrachloride as raw material to prepare silica with superior physicochemical performance by applying precipitation method and further functionalizing the silica surface with amino(-NH₂) group using 3-aminopropyltriethoxysilane(APTES)as modification reagent. The amino content on the silica surface was determined by the kjeldahl method. Finally, the application of the amino functionalized Silica in the process of deacidification of camellia oil was studyed. The main work of this thesis is as below:1. Silica powders was prepared by adopting the precipitation method using silicon tetrachloride and sodium silicate as raw materials, polyethylene glycol as surface active agent and ethanol as dispersant. The influence on the silica particle size and feature of the reaction temperature, the concentration of sodium silicate and PEG (polyethylene glycol), the amount of ethanol added, pH value of the system and other factors was studyed according to the factor analysis method. The optimal conditions were finally determined as follows: the reaction temperature, the sodium silicate concentration, the PEG concentration, the volume ratio of ethanol and water, and the final pH value of the system were 50℃, 0.2mol/L, 3%, 0.2 and 8, respectively. The sample was characterized by XRD, SEM, TEM and nanometer zetasizer tester.2. The prepared silica particles were functionalized with amino (-NH₂)functional group using 3-aminopropyltriethoxysilane ( APTES ) as modification reagent. The amino content on the Silica surface was determined by the kjeldahl method. The modification conditions, such as the reaction time, reaction temperature and reaction dissolvant, were optimized according to the factor analysis method based on maximum amino concentration.In the meantime, the composition, structure and particle size distribution of the modified silica were characterized by various test methods. All the results demonstrate that the APTES has grafted to the silica particle surface and kept well the structure and feature of original particles. 3. The amino-functionalized silica was applied to deacid camellia oil. Due to the chemical reaction between the amino(-NH₂)on the silica surface and the -COOH of free fatty acid in the camellia oil (amido bonds formed), free fatty acid in the camellia oil was adsorbed on the the silica surface and then the silica was isolated from the camellia oil. In this way, the free fatty acid can be removed and the acid value of the camellia oil be reduced. The assay result demonstrates that the amino silica can achieve the purpose of deacidification of the camellia oil.