Studies on bromination and evaporation of antimony oxide during thermal treatment of tetrabromobisphenol A (TBBPA)

In this paper the bromination reaction between antimony oxide (Sb2O3) and hydrobromic acid, originating from the thermal decomposition of tetrabromobisphenol A (TBBPA), under inert and oxidative atmospheres was investigated using differential scanning calorimetry (DSC) analysis and a laboratory-scale furnace. The results indicate that the bromination follows the decomposition of the TBBPA and takes place below 340 degrees C in the furnace and around 280 degrees C during DSC analysis. During thermal treatment of a mixture of TBBPA and Sb2O3 (2.82:1, w/w), it was observed that volatilization of the SbBr3 began immediately after its formation occurred at about 340 degrees C. The maximum amount of antimony converted into SbBr3 (above 60%) was obtained from runs conducted at temperatures between 440 and 650 degrees C. The main intermediate products found in the solid residue were Sb4O5Br2 and Sb8O11Br2, which then decompose to more stable compounds such as Sb2O3 at temperatures above 440 degrees C. Finally, when a temperature of 650 degrees C is reached, Sb2O3 undergoes a carbothermic reduction into metallic antimony. Additional experiments conducted at selected temperatures under an oxidative atmosphere (He + 5%O-2) indicated that the presence of oxygen has only a small influence on the bromination reaction, however, these conditions may enhance the decomposition of TBBPA at 340 degrees C, which may result in enhanced evaporation of the formed SbBr3 at 340 degrees C. (C) 2010 Elsevier B.V. All rights reserved.