Plasma-catalytic dry reforming of methane in an atmospheric dielectric barrier discharge: Understanding the synergistic effect at low temperature

A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma-catalytic dry reforming of CH4 into syngas over different Ni/gamma-Al2O3 catalysts. Three different packing methods are introduced into the single-stage plasma-catalysis system to investigate the influence of catalysts packed into the plasma area on the physical properties of the DBD and determine consequent synergistic effects in the plasma-catalytic dry reforming reactions. Compared to the fully packed reactor, which strongly changes the discharge mode due to a significant reduction in the discharge volume, partially packing the Ni/-gamma-Al2O3 catalyst either in a radial or axial direction into the discharge gap still shows strong filamentary discharge and significantly enhances the physical and chemical interactions between the plasma and catalyst. Optical emission spectra of the discharge demonstrate the presence of reactive species (CO, CH, C-2, CO2+ and N-2(+)) in the plasma dry reforming of methane. We also find the presence of the Ni/gamma-Al2O3 catalyst in the plasma has a weak effect on the gas temperature of the CH4/CO2 discharge. The synergistic effect resulting from the integration of the plasma and catalyst is clearly observed when the 10 wt% Ni/gamma-Al2O3 catalyst in flake form calcined at 300 degrees C is partially packed in the plasma, showing both the CH4 conversion (56.4%) and H-2 yield (17.5%) are almost doubled. The synergy of plasma-catalysis also contributes to a significant enhancement in the energy efficiency for greenhouse gas conversion. This synergistic effect from the combination of low temperature plasma and solid catalyst can be attributed to both strong plasma-catalyst interactions and high activity of the Ni/gamma-Al2O3 catalyst calcined at a low temperature. (C) 2012 Elsevier B.V. All rights reserved.