Optimization of dry reforming of methane over Ni/YSZ anodes for solid oxide fuel cells

This work investigates the catalytic properties of Ni/YSZ anodes as electrodes of Solid Oxide Fuel Cells (SOFCs) to be operated under direct dry reforming of methane. The experimental test rig consists of a micro-reactor, where anode samples are characterized. The gas composition at the reactor outlet is monitored using a mass spectrometer. The kinetics of the reactions occurring over the anode is investigated by means of Isotherm reactions and Temperature-programmed reactions. The effect of the variation of temperature, gas residence time and inlet carbon dioxide-methane volumetric ratio is analyzed. At 800 degrees C, the best catalytic performance (in the carbon safe region) is obtained for 1.5 < carbon dioxide/methane ratio <2, which is an interesting result for prospective direct biogas fueled SOFCs. Conversion is stable over a period of 70 h. Both for temperatures lower than 450 degrees C and for carbon dioxide methane ratios lower than equi-molar at 800 degrees C, conversion is poor due to low activity of the anode toward dry reforming and cracking reactions, respectively. In other ranges, dry reforming and reverse water gas shift are the dominant reactions and the inlet feed reaches almost the equilibrium condition provided that a sufficient gas residence time is obtained. (C) 2013 Elsevier B.V. All rights reserved.