Warm plasma catalytic reforming of biogas in a heat-insulated reactor: Dramatic energy efficiency and catalyst auto-reduction

Abstract

Highly efficient warm plasma catalytic reforming of biogas in a compact and heat-insulated reactor using gliding arc discharge with a co-axial electrode configuration and Ni-based catalyst was reported. The effect of inlet flow rate at a special energy input (SEI) of 20kJ/mol for the plasma alone was first investigated and the inlet flow rate was selected at 4 SLM. Then, it was found that the Ni-based catalyst could be auto-reduced by the outgoing gas from the warm plasma via comparing with the pre-reduced catalyst in the reforming reaction testing and characterizations of Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of catalyst-bed position (l) was also examined. Feeding with the molar ratio of CH4:CO2:O2=3:2:1.8, for the warm plasma with the auto-reduced Ni/CeO2/Al2O3 catalyst located at l=4cm, dry-basis concentration of syngas rose substantially to 81% and energy efficiency improved dramatically to 86%. Syngas energy cost reduced significantly to 0.21kWh/Nm3, which is nearly a threefold reduction compared with the plasma alone. The stability of the warm plasma catalytic reforming was preliminarily evaluated over time-on-stream (TOS) of 13.5h.