Methane pyrolysis in a hot filament reactor

An electrically heated platinum filament mounted inside a quartz tube was used as a high temperature flow reactor for methane pyrolysis. The reaction products included carbon and a mixture of hydrocarbons, mainly C1-C5 alkanes, alkenes, and benzene. The hydrocarbons were measured by gas chromatography and the carbon gravimetrically. At 1275 degrees C filament temperature and 100ms residence time in the hot region of the reactor, methane conversion was 19.7% and selectivity of hydrocarbon products 68%. Lowering the flow rate increased the conversion but lowered sharply the selectivity of hydrocarbon products. Coking of the filament surface gradually lowered the filament temperature and the conversion of methane. This deactivation process could be slowed by adding a few percent of oxygen to the methane feed.