There is a growing body of literature that examines the catalytic capacity of metal oxides in acting as halogen fixation agents during thermal recycling of halogenated polymers. Franklinite (ZnFe2O4) represents one of the most abundant metal oxides in electric arc furnace dust (EAFD). EAFD are emitted as unwanted by-product from crude steel manufacturing operations. A great deal of experimental work has established that EAFD captures the chlorine and bromine contents in polyvinyl chloride (PVC) and brominated flame retardants. However, the specific underlying mechanisms for the interaction of HCl/Br and other halogenated C1-C6 cuts reactions with Franklinite is still not well understood. Density functional theory (DFT) calculations were carried out in the present work to investigate the chemical interplay between of HCl/Br and selected halogenated hydrocarbons (namely as chloroethene, 1-chloro-1-propene, chloroethane, 2-chloropropane, chlorobenzene, 2-chlorophenol and their brominated counterparts) with ZnFe2O4, as a model compound for metal oxides in EAFD. A detailed kinetic analysis points out that, the adsorption mechanism of HCl/Br on a clean ZnFe2O4 surface is based on a dissociative chemisorption pathway that encompasses halogen−hydrogen bond cleavage and forming oxyhalide structures via modest activation barriers. In that course of interaction, we have demonstrated that conversion of the oxyhalide structure into zinc halides occurs via further dissociative adsorption of HCl/Br molecules by the same surface Zn atom, followed by the release of a H2O molecule via an intramolecular hydrogen transfer. The results also indicated that the catalytic removal of halogen atoms from alkanes and olefins generally proceed via two pathways; direct elimination, or dissociative adsorption followed by hydrogen transfer to the surface. Both channels assume comparable reaction rate constants in reaction networks that ensure to produce acetylene from vinyl chloride/bromide.
عدي حميد احمد | Oday Hameed Ahmed | 1032