Carbon dioxide reforming of methane under periodic operation

Abstract

This work investigates the carbon dioxide reforming of methane on a commercial Ni/SiO[subscript 2].MgO catalyst. Methane and carbon dioxide, which are major components found in natural gas and biogas, are efficiently utilized for the production of synthesis gas with low H[subscript 2]/CO ratio. The study is aimed at investigating the possibility for applying the periodic operation to this reaction. In the operation, pure methane was fed to the catalyst bed where the methane cracking reaction took place, yielding hydrogen and carbonaceous deposit. The catalyst was regenerated via the reverse Boudouard reaction under a flow of pure carbon dioxide. The effect of key parameters such as cycle period, cycle split, and reaction temperature were investigated and the results were compared with those from the steady state operation. All experiments were carried out under the same time-average flow rate of both reactants. At 1023 K, the methane conversion and hydrogen yield initially decreased with time on stream and eventually leveled off, giving the values about half of those from the steady state operation. The decreased catalytic activity was due to the accumulation of carbonaceous deposit and loss of metal active sites. The different trend was observed at 923 K. The methane conversion and hydrogen yield were not changed with the time on stream although more carbonaceous deposit was accumulated during the reaction course. At this temperature, the periodic operation offered the equivalent hydrogen yield to the steady state operation. The observed behavior may be due to the different mechanisms of carbon formation over the catalyst. Further investigations are required to elucidate this unusual behavior. Finally it was found that no significant effects of cycle period and cycle spilt on the reaction performance was observed at least within the ranges of this study