Methane decomposition and catalyst regeneration in a cyclic mode over supported Co and Ni catalysts Original Research Article

CH4 decomposition (CH4 → C + 2H2) on supported Co and Ni catalysts has been studied using a fixed-bed, oscillating microbalance reactor and a 5% CH4 in He feed reacted at 773 K and 101 kPa. After 45 min reaction the catalysts were regenerated by reaction of the deposited carbon with O2 or CO2 at 773 K and 101 kPa. The effect of repeated CH4 decomposition–carbon oxidation cycles is reported. At the chosen conditions, Ni was more active and more stable than Co during the CH4 decomposition step. Although >90% of the carbon deposited on both Co and Ni was removed by reaction with O2, an oxidation of the active metal also occurred. In subsequent CH4 decomposition steps, an induction period was necessary to re-reduce the Co. Furthermore, the oxidized metal reacted with CH4 producing CO and CO2 as an impurity in the H2. Removal of the carbon deposit by reaction with CO2 rather than O2 significantly decreased the CO contamination of the produced H2 on the Ni catalyst. However, the carbon removal rate was 20×ʹs slower with CO2 compared to O2. Several CH4 decomposition–carbon oxidation cycles were completed on the Ni catalyst without a significant loss in activity, whereas the Co catalyst deactivated.