Non-thermal plasma assisted methane oxidation inside a DBD reactor: Effect of monometallic catalyst on energy efficiency and CO2 selectivity

The oxidation of methane was studied in a co-axial dielectric barrier discharge (DBD) quartz tube reactor at room temperature and atmospheric pressure. Methane oxidation was investigated in two reactor configurations: an empty DBD reactor and a packed-bed DBD reactor containing various oxidation catalysts (Co/Al 2 O 3 , Cu/Al 2 O 3 , Fe/Al 2 O 3 , Pt/Al 2 O 3 , and Pd/Al 2 O 3 ). Methane oxidation was examined at plasma power levels ranging from 20 to 40 W. In the empty DBD reactor, methane conversion was initiated at 23 W plasma power. Methane conversion increased with increasing plasma power due to generation of more active species. The main methane oxidation products were CO and CO 2 . Both CO 2 selectivity and energy efficiency improved with increasing plasma power. However, methane conversion, CO 2 selectivity, and energy efficiency declined as the gas flow rate was increased due to the reduced residence time of gases inside the plasma discharge zone. In the packed-bed DBD reactor, methane conversion was lower than in the empty reactor due to the reduced residence time of gases inside the plasma discharge zone. The presence of catalyst increased the plasma power requirements for methane conversion. Among the catalysts, Co/Al 2 O 3 and Cu/Al 2 O 3 catalysts exhibited higher methane conversion at lower plasma power (<30 W), while Pd/Al 2 O 3 catalyst demonstrated higher methane conversion at higher plasma power (>35 W). The presence of catalysts generally improved CO 2 selectivity, with noble metal catalysts achieving above 95 % CO 2 selectivity across all plasma power levels studied. Despite the higher plasma power requirements in packed-bed DBD, both Pd/Al 2 O 3 and Co/Al 2 O 3 improved energy efficiency compared to the empty reactor. • Non thermal plasma was able to convert CH 4 into CO and CO 2 at room temperature and atmospheric pressure. • Plasma-catalyst system with noble metals (Pd and Pt) achieved 99% CO 2 selectivity above 35 W plasma power. • Cu and Co catalysts showed higher CH 4 conversion below 30 W while Pd catalyst was the most active above 35 W. • Both Pd/Al 2 O 3 and Co/Al 2 O 3 catalysts demonstrated higher energy efficiency than the empty reactor.