Preparation of SiCl4 from Rice Hull Ashes (Part 3): FT-IR-PAS Analysis of Chlorination Mechanism of Rice Hull Ashes Containing Alkaline and Alkaline Earth Metal Salts

The chlorination of a mixture of rice hull ashes and carbon containing alkaline and alkaline earth salts was investigated by FT-IR-PAS. It was thought that the relative ratio of totally symmetric SiO4 stretching vibration (ν1) to antisymmetric SiO4 degenerate stretching vibration (ν3) in infrared frequencies for SiO2 whose constituent oxygen atoms occupy the corners of a tetrahedron shows structural changes of SiO2 network. The results of ν1/ν3 of SiO2 before and after chlorination showed that the values of ν1/ν3 increased and the chlorination was accelerated because K+ increased. The ν1/ν3 of SiO2 by addition of Na+, Mg2+ and Ca2+ was smaller than that of K+ and these additives did not accelerate the chlorination. KCl, NaCl, MgCl2 and CaCl2 which formed during the chlorination melted at 900°C.