Catalytic and Non-catalytic Conversion of Methane to C۲ Hydrocarbons in a Low Temperature Plasma

The direct conversion of methane to C۲ hydrocarbons, in a quartz tube reactor enforced by a DC corona discharge, was investigated at atmospheric pressure. The process was carried out in the presence of metal oxide catalysts of Mn/W/SiO۲, Mn/W/SiO۲ (tetraethyl orthosilicate, TEOS), and Mn/W/CNT (supported on carbon nanotubes). The total yield to C۲ hydrocarbons in the presence of metal oxide catalysts in plasma environment was in the order of Mn/W/SiO۲> Mn/W/SiO۲ / TEOS> Plasma only> Mn/W/CNT. The order changes to Mn/W/SiO۲>Mn/W/CNT>Plasma only> Mn/W/SiO۲/ TEOS, when the selectivity and yield of ethylene is considered. The highest yield to C۲ hydrocarbons was ۱۵.۸%, which was obtained by using Mn/W/SiO۲ in combination with gas discharge plasma without external heating; it was lower when the same feed composition was tested over this catalyst at ۸۲۵ °C. The catalyst Na۲WO۴/Mn۲O۳/SiO۲ –b۱, which produces the least carbon oxides, gives rise to the highest production of higher hydrocarbons and ethylene. Catalysts Na۲WO۴/Mn۲O۳/SiO۲ /TEOS-b۲ and Na۲WO۴/Mn۲O۳/‍CNT-b۳,due to their high selectivity toward carbon oxides, show low efficiency in producing more valuable hydrocarbons.

Keywords:

Methane Conversion , Non-thermal Plasma , Catalysis , Metal Oxide , Hydrocarbons