Reforming of CO2-Containing Natural Gas Using an AC Gliding Arc System: Effects of Operational Parameters and Oxygen Addition in Feed

Abstract

In this research, the reforming of simulated natural gas containing a high CO2 content under AC non-thermal gliding arc discharge with partial oxidation was conducted at ambient temperature and atmospheric pressure, with specific regards to the concept of the direct utilization of natural gas. This work aimed at investigating the effects of applied voltage and input frequency, as well as the effect of adding oxygen on the reaction performance and discharge stability in the reforming of the simulated natural gas having a CH4:C2H6:C3H8:CO2 molar ratio of 70:5:5:20. The results showed marked increases in both CH4 conversion and product yield with increasing applied voltage and decreasing input frequency. The selectivities for H2, C2H6, C2H4, C4H10, and CO were observed to be enhanced at a higher applied voltage and at a lower frequency, whereas the selectivity for C2H2 showed an opposite trend. The use of oxygen was found to provide a great enhancement of the plasma reforming of the simulated natural gas. For the combined plasma and partial oxidation in the reforming of CO2-containing natural gas, air was found to be superior to pure oxygen in terms of reactant conversions, product selectivities, and specific energy consumption. The optimum conditions were found to be a hydrocarbons-to-oxygen feed molar ratio of 2/1 using air as an oxygen source, an applied voltage of 17.5 kV, and a frequency of 300 Hz, in providing the highest CH4 conversion and synthesis gas selectivity, as well as extremely low specific energy consumption. The energy consumption was as low as 2.73 × 10−18 W s (17.02 eV) per molecule of converted reactant and 2.49 × 10−18 W s (16.60 eV) per molecule of produced hydrogen.