Zeolite catalysts for dehalogenation processes Original Research Article

A review is given of recent work in which zeolites have been used to catalyse the decomposition, oxidation or hydrodehalogenation of halogen containing molecules. The reactivity of CFCs depends strongly on the number of CH and CCl bonds in the molecule. Reactions over FAU and MFI zeolites involve acid sites, and irreversible dealumination of the zeolites through the formation of extraframework AlF3 species. Halons (bromofluorocarbons) have been less widely studied, but both pyrolysis and hydrodehalogenation reactions occur over transition metal exchanged MFI zeolites. Both acidic and metal loaded zeolites have also been explored as catalysts for the oxidation and/or hydrodehalogenation of other organohalogen compounds of environmental concern. Features of zeolite chemistry common to these different applications are identified, and prospects for development of zeolite based dehalogenation processes for environmental protection discussed.