Conversion of methane by an electric barrier-discharge plasma using an inner electrode with discharge disks set at 5 mm intervals

•The between discharge disks with 5 mm interval can increase methane conversion.•The interval can improve the selectivity of propane, C4 and over hydrocarbon.•The product carbon selectivity is not changed with increasing flow rate at Pw of 32 W.•The product carbon selectivity of both reactors is different at Pw of 3 W.

In this study, we investigated the effect of inner electrode structure on methane conversion (XCH4XCH4) and product selectivity using dielectric barrier-discharge plasma. We used two types of inner electrodes: those with discharge disks set at 5 mm intervals (Type A) and those with discharge disks set at 0 mm intervals (Type B).When electric power (Pw) was increased, the methane conversion (XCH4XCH4) of Type A and Type B increased. However, the XCH4XCH4 of Type A reactor was lower than that of Type B reactor, irrespective of Pw. When the total thickness of the discharge disks set at 0 mm intervals was the same as that in Type A, XCH4XCH4 was lower than the XCH4XCH4 for Type A or Type B. This result shows that the presence of discharge disk intervals can result in increased XCH4XCH4. The primary product was ethane when using electrodes with/without intervals under various conditions. When Pw was increased in Type A, the product carbon selectivity (PCS) of propane and C4+ hydrocarbon increased with increased Pw and the PCS of ethylene decreased. When Type B was used, the PCS of acetylene also increased with an increase in Pw. These results show that Type A reactors can promote homologation and Type B reactors can promote dehydration. When the flow rate (F0) was varied at a Pw of 3 or 32 W, XCH4XCH4 decreased with increased F0. Ethane was again the primary product, and the F0 value did not dramatically affect the PCS.