Synergetic effect of plasma/catalysis hybrid system for CH4 removal

Methane abatement from rich gas mixture was performed in a plasma-catalyst reactor. The inlet concentration of CH4 varied from 0.15 to 1 vol.% of the total flow rate. Influences of different parameters such as temperature, gas composition and catalyst were investigated. The catalyst was an alumina wash-coated monolith made of cordierite containing 0.15 wt% of palladium and 15 wt% of Al2O3. The plasma was generated by means of a high voltage monopolar excitation. The higher the energy density, the higher the methane conversion. For plasma experiments carried out without catalyst, the CH4 conversion reached a maximum of 33% for 1 vol.% CH4 and 49% for 0.3 vol.% CH4 in a N2/O2/CO2/H2O gas mixture (75/18.7/4/2 vol.%) at 200 °C and 1823 J L−1. Carbon monoxide (CO) was observed to be the main product. The CO yield reached 29% and 49% for 1 and 0.3 vol.% CH4, respectively. Moreover, experiments performed with a hybrid plasma-catalytic reactor showed two different behaviours depending on the catalyst location. In POST-plasma position, the presence of the catalyst did not modify the methane conversion but oxidized CO into CO2. In IN-plasma position, the catalyst inhibited the methane conversion by decreasing the plasma volume between electrodes but oxidized CO into CO2.

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