Decomposition of CH4 over supported Ir catalysts

The decomposition of methane and its conversion into higher hydrocarbons have been investigated on supported Ir catalysts. The effects of temperature, flow rate and support materials have been examined. The interaction of CH₄ with iridium has been observed at as low a temperature as 473 K. As a result, hydrogen, a small amount of ethane and surface carbonaceous species were produced. With increase of the temperature, the extent of the decomposition significantly increased. At 773 K, the initial conversion varied between 2.0–5.0%, which decreased to low values in a short reaction time. Taking into account the dispersion of Ir, the most effective sample in the decomposition of CH₄ was Ir/MgO. By means of Fourier transform infrared spectroscopy adsorbed CH₃ was identified as a reaction intermediate of methane decomposition. Temperature programmed reactions revealed that the reactivity of surface carbon produced in the decomposition of CH₄ depends on the nature of the support. Hydrogenation of the most reactive carbonaceous species led to the production of aliphatic hydrocarbons up to six carbon atoms.