DIRECT EVIDENCE OF ELECTRONICALLY MEDIATE D REACTION DURING TICL4 REDUCTION BY MAGNESIUM

An attempt has been made to obtain direct evidence of electrochemical redox reaction, i.e. electronically mediated reaction (EMR) during TiC l4 reduction by magnesium, and it includes a clear understanding of th e mechanism of titanium deposition in the Kroll process. Feed material of TiCl4 and reductant magnesium were charged into different location s in molten MgCl2 at 1073 K. Large current, more than 5 A, between the se feed and reductant locations has been clearly detected when shorten ing these electronically isolated sites, and metallic titanium deposit s were observed in the TiCl4 feed site. Reproducibility of these exper iments was well-confirmed. Thus, magnesiothermic reduction of TiCl4 ap pears to occur by EMR without direct physical contact between feed and reductant. The usefulness of the concept of EMR was demonstrated by e xplaining mechanism of titanium deposition in the sponge form on the r eactor wall and reaction pathways including the crawling behavior of m agnesium on the metallic wall surface in the Kroll process. The presen t results suggest the concept of EMR plays an important roll in metall othermic reduction of TiCl4 due to electron transfer through an electr onically conductive medium, e.g. reaction wall and titanium deposit an d due to ion transfer through MgCl2 as an ionic conductive medium.