Although halons (brominated or chlorinated fluorocarbons) are widely used as fire suppressants and foaming agents, they also contribute to stratospheric ozone depletion. However, halons are potentially valuable chemicals that should not be destroyed, but rather converted to reusable chemicals, says Bogdan Dlugogorski, professor of chemical engineering in the school of chemical engineering, faculty of engineering, University of Newcastle (New South Wales, Australia; edlinks.chemengonline.com/6900-532). Dlugogorski is part of a team of researchers developing a process to convert halons into useful hydrofluorocarbons (HFCs).
In the process, halons react in the gas phase via reductive coupling with methane at elevated temperatures in a high-purity, alpha-alumina tubular reactor, producing HFCs and mineral acids. For example, halon 1301 (CBrF3) is converted into trifluoromethane, ethylene and HBr; halon 1211 (CBrClF2) is converted into difluoroethane, HCl and HBr. The reaction yield for forming C2H2F2 is approximately 40–50 mol%. A fluidized bed scrubber downstream from the reactor is used to remove acid gases from the product.
The process is being developed in a pilot plant that handles about 3 m.t./d of halons. The team is also working on a catalytic process for the reductive coupling of halons with methane and hydrodehalogenation with H2 under relatively mild reaction conditions, says Dlugogorski.