The fate of bromine during pyrolysis of tetrabromobisphenol A-bis(2,3-dibromopropyl ether): A combined experimental and computational study

Abstract

A thorough comprehension of the migration mechanism of Br is essential for the thermochemical recycling of waste electrical and electronic equipment (WEEE), given that brominated flame retardants (BFRs) are key components in WEEE. Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (TBBPA-DBPE) is a new BFR that has been widely used in WEEE in recent years, whereas the transformation of Br during the thermochemical recycling of TBBPA-DBPE has been rarely reported. In this study, the decomposition mechanism of TBBPA-DBPE pyrolysis to generate Br-containing products was investigated by combining experiments and density functional theory (DFT) calculations. The primary Br-containing products of TBBPA-DBPE pyrolysis were HBr, 1,2,3-tribromopropane, and bromophenols. During the initial stage of pyrolysis, TBBPA-DBPE predominantly undergoes the homolysis of the C–O and C–Br bonds, resulting in the formation of 1,2,3-tribromopropane. Subsequently, Br radicals and H atoms can react with TBBPA-DBPE and its intermediates to produce various Br-containing products, including HBr, 2,4,6-tribromophenol and 2,6-dibromophenol. Notably, the 2,6-dibromophenol radical serves as a critical precursor for the formation of brominated dioxins via C–O coupling reactions. This research provides a theoretical basis for managing Br during the thermochemical treatment of WEEE.