CO2 reforming with methane for syngas production using a dielectric barrier discharge plasma coupled with Ni/γ-Al2O3 catalysts: Process optimization through response surface methodology

In this work, CO2 reforming with methane in the form of biogas over Ni/gamma-Al2O3 catalysts was carried out in a coaxial dielectric barrier discharge (DBD) non-thermal plasma reactor. The effects of various process parameters (biogas flow rate, discharge power, CO2/CH4 molar ratio and Ni loading) and their interactions on the hybrid plasma-catalytic biogas reforming were evaluated using response surface methodology through a four-factor, five-level central composition design. Quadratic regression models were developed to gain a better understanding of the relationships between these process parameters (independent variables) and the biogas conversion, syngas yield and energy efficiency (responses) of the plasma reforming process. The results indicated that biogas flow rate was the most significant factor affecting the conversion of CO2 and CH4 and syngas yield, while the CO2/CH4 molar ratio was the leading process parameter determining the energy efficiency of the process. In addition, there was a trade-off between the biogas conversion and energy efficiency of the process at different specific energy inputs (SEI). The process optimization suggested that the optimal process performance was achieved at a biogas flow rate of 56.1 ml/min, a discharge power of 60.0 W, a CO2/CH4 molar ratio of 1.03 and a Ni loading of 9.5 wt.%, which was demonstrated by the reproducibility of the experimental results. Moreover, the carbon deposition on the spent catalyst was only 3.9% after running the plasma biogas reforming process for 150 min under the optimal experimental conditions.