Direct coupling of bromine-mediated methane activation and carbon-deposit gasification.

The direct bromination of methane offers a quite selective (>98 %) route towards methane activation but shifts the problem of fuel production to converting and handling corrosive methyl bromide. The direct conversion of methyl bromide, at about 200 degrees C, into light hydrocarbons can be catalyzed under pressure by AlBr(3) resulting in the formation of propane-rich mixtures of light hydrocarbons, carbonaceous deposits, and HBr. After releasing the gaseous products, the addition of hydrogen at 260 degrees C allows a quantitative conversion of the carbonaceous deposits into the same range of light hydrocarbons. These second-stage products efficiently contribute to the overall process yield while enabling a full regeneration of the catalyst's activity. This oxygen-free process is compared to the conversion of methyl bromide on zeolites and the currently used methanol-to-gasoline (MTG) process in terms of product distributions and apparent energy of activation. A detailed chemical analysis of the intermediates revealed the presence of a carbon pool consisting of highly substituted benzene and cyclopentadiene derivatives, as observed on zeolites used in the MTG process. This similarity suggests that the currently used oxygen-based syngas/MTG process for methane conversion may be extended to a bromine-mediated process by using methyl bromide as an intermediate instead of methanol.