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 °C in the furnace and around 280 °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 °C. The maximum amount of antimony converted into SbBr₃ (above 60%) was obtained from runs conducted at temperatures between 440 and 650 °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 °C. Finally, when a temperature of 650 °C is reached, Sb₂O₃ undergoes a carbothermic reduction into metallic antimony. Additional experiments conducted at selected temperatures under an oxidative atmosphere (He + 5%O₂) 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 °C, which may result in enhanced evaporation of the formed SbBr₃ at 340 °C.