THE ROLE OF BROMINE IN THE DE-NOVO SYNTHESIS IN A MODEL FLY-ASH SYSTEM

The role of bromine in the de novo synthesis in a model fly ash system has been evaluated. A silica-alumina carrier was impregnated with a C uX2 catalyst system (X=Cl, 0.5 wt%; X=Br, 0.8 wt%). A flow of air with 5 vol.% HX (X=Cl or Br) was passed over a fixed bed at 300-degrees-C. Several processes have been investigated concerning the role of bromi ne and chlorine in the formation of polyhalogenated dibenzo-p-dioxins and -dibenzofurans in municipal waste incinerator fly ash under condit ions observed in an electrostatic precipitator: (i) The exchange of br omine and chlorine in 2,3,7,8-tetrabromodibenzo-p-dioxin; (ii) The rea ctivity and selectivity of bromine and chlorine in the halogenation of the parent structures dibenzo-p-dioxin and dibenzofuran; (iii) The co mpetition of bromine and chlorine in the de novo synthesis.