Dry reforming of methane in a tip–tip arc discharge reactor at very high pressure

• We report the conversion of CH4 and CO2 to syngas with very high pressure plasma.
• Low carbon formation observed as pressure increases.
• Carbon black and gaseous products formed at the instance of arc ignition.
• Conversion of CH4 and CO2 decreases with pressure.
• Formation of C2 to C3 saturated and unsaturated hydrocarbons reported.

Over the last two decades there has been growing research interest in the oxidative reforming of methane using carbon dioxide (CO2), with the aim of producing syngas (mixture of H2 and CO) which can be converted to synthetic fuels via the Fischer–Trospch process. Among the different options investigated, non-thermal plasma technology is considered to have a high potential for natural gas to syngas (and higher hydrocarbons) conversion at relatively lower energy consumption and cost. While many studies on plasma dry reforming of methane have been carried out over the years using different non-thermal plasma technologies, almost all these studies have been undertaken at near-atmospheric pressure. The aim of this paper is to study the influence of the pressure on the plasma dry reforming of methane. For this purpose, a tip–tip plasma batch-reactor connected to a high voltage direct current power supply has been used. This reactor has a maximum pressure limit of 20 MPa. All experiments were carried out with a CH4/CO2 reactant gas ratio of 1.8, a current of 350 mA, an interelectrode gap of 0.4 mm, and discharge duration of 60 s. The results presented in this paper show the variation of the concentration of the different obtained products: CO, H2, C2 and C3 hydrocarbons versus the operating pressure. From these results, the selectivity, chemical yield, H2/CO ratios and energy balances have been determined. The results from this study are compared to other plasma dry reforming studies in the literature. The high pressure reactor shows a high potential in terms of energy efficiency despite the low conversion due to the specific energy consumed by the reactant and the small discharge volume. The conversion could possibly be improved by increasing the interelectrode gap, and thus create a larger arc discharge reaction zone.