Catalytic behaviour of nickel-based catalysts operating onsimulated biogas: optimisation through oxygen addition,temperature variation and catalyst modification

The use of catalytic systems operating on waste products such as biogas offers a potentially attractive alternative for renewable and sustainable energy generation. To investigate the potential viability of such catalytic systems for operation on biogas, a detailed study of nickel-based catalysts for the reforming of simulated biogas (methane:carbon dioxide = 2) to synthesis gas has been undertaken. The influence of oxygen addition in varied concentrations to the simulated biogas mixture has been investigated with regards to catalyst activity, selectivity and stability. This influence has been studied over an extended temperature range from room temperature to 1000 °C.Additionally, the effect of H2S within the simulated biogas mixture on the catalyst activity, selectivity and stability has been studied. Also, the influence of ceria-doping of the nickel catalyst on catalytic behaviour has been investigated.Temperature programmed and conventional catalytic reaction measurements have been used to analyse the catalytic behaviour and long term stability of the catalyst system over a full range of reaction temperatures. Carbon deposits from the simulated biogas reforming were analysed using post-reaction temperature programmed oxidation to assess the extent and nature of carbon deposition.The addition of oxygen significantly increases catalyst activity and shows a variation in product selectivity with temperature. Increased catalyst stability through reduced carbon deposition and increased sulfur tolerance is also observed with oxygen addition. Doping of the nickel catalyst with ceria enhances the influence of oxygen, apart from at high oxygen levels where total oxidation of methane is prevalent. Catalyst regeneration from sulfur poisoning has also been shown through oxygen addition to the simulated biogas mixture and ceria-doping of the nickel catalyst.Fuel cell studies have shown the successful operation of solid oxide fuel cells on simulated biogas and the substantial improvements in electrical performance through addition of oxygen and increased temperature