Reforming Reactions of Model Biogas over Honeycomb Supported Ni Catalysts

From the standpoint of the environmental load, it is important to develop the hydrogen production system from methane produced by the fermentation of food waste or biomass. Compared with conventional catalysts such as pellet or raschig ring type catalysts, honeycomb catalyst is consider to be suitable for this process, especially for small-scale applications because it has the advantages such as high geometric surface area and the low pressure drop. We chose the cordierite substrate of Ni catalyst from several oxides, and applied it to steam reforming, partial oxidation and autothermal reforming by using model biogas. The temperature profiles of outlet gas concentration and CH4 conversion was investigated in these reactions. CH4 conversion did not reach the equilibrium conversion at the outlet temperature in steam reforming. This result suggests the reaction rate was low and the catalyst bed temperature was lower than that at the outlet, due to the endothermic nature of steam reforming and poor heat conduction of the honeycomb substrate. On the other hand, CH4 conversion in partial oxidation and autothermal reforming, which are the exothermic reactions, exceeded apparently the equilibrium conversion calculated for the outlet temperature in the temperature range below 1000 K, indicating the catalyst bed temperature was higher than that at the catalyst outlet. Optimum ratio of steam/CH4 (S/C) and O-2/CH4 (O-2/C) were examined for autothermal reaction of CH4, and it was found that the highest hydrogen concentration was attained at O-2/C = 0.5 and S/C >= 2.