Effect of ethane and ethylene on catalytic non oxidative coupling of methane

The effect of addition of ethane and ethylene (C₂) on methane coupling at 1000 °C was investigated. A Fe/SiO₂ catalyst was used to determine the contributions of catalytic as well as C₂ initiated methane activation. The catalyst load as well as the residence times at 1000 °C downstream of the catalyst bed were varied. C₂ addition significantly increases methane conversion rates, similarly for both ethane and ethylene, although ethylene is more effective when operating with long residence times in the post-catalytic volume. Methane activation via C₂ addition proceeds dominantly in the gas-phase whereas catalytic C₂ activation is negligible. The catalyst has no effect on methane conversion when the feed contains more than 2 vol% C₂. Product selectivity distribution as well as total hydrocarbon yield at 10% conversion is not influenced by C₂ addition, but is influenced by the amount of catalyst as well as residence time in the post-catalytic volume at high temperature. It is proposed that C₂ impurities in natural gas change from a nuisance to an advantage by enhancing methane conversion and simplifying purification of the natural gas feed. A process is proposed in which ethylene is recycled back into the reactor to initiate methane coupling, leading to a process converting methane to aromatics.