Preparation of SiCl4 from Rice Hull Ashes (Part 2)

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Abstract
In order to produce SiCl4 efficiently from active SiO2 in rice hulls, rice hull ash, combustion waste of rice hull, was chlorinated under the coexistence of alkaline and alkaline earth additives such as potassium compounds in the temperature range of 600° to 1000°C. These additives changed to chlorides under the condition of chlorination. Potassium compounds accelerated the chlorination of the rice hull ash. Other alkaline and alkaline earth compounds such as lithium, sodium, magnesium and calcium inhibited the chlorination. The acceleration effect of potassium in the chlorination of SiO2 was explained by assuming that the diffusion of K+ ion in SiO2 lattice caused the distortion of SiO2 lattice and the chlorinating species such as chlorinated carbon were easy to diffuse in SiO2 lattice. The inhibitory efffect of other elements was interpreted in terms of the absence of SiO2 lattice distortion, since the ionic radii of these elements are smaller than that of K+. It is also inferred that the melts of these chlorides covered the contact points of SiO2 and C.

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