Syngas production on a Ni-enhanced Fe2O3/Al2O3 oxygen carrier via chemical looping partial oxidation with dry reforming of methane

Abstract

A novel chemical looping process was introduced by combining partial oxidation and dry reforming of methane on a cost-effective iron-based oxygen carrier to produce high-purity syngas with a H2/CO ratio of 2. The rationale for the proposed chemical looping process was substantiated with the thermodynamic data, which showed increased syngas purity and an H2/CO ratio close to 2 by introducing the CH4-CO2 mixture feed. Compared with the general chemical looping process, the calculated carbon deposition with the CO2 emission of the proposed process was dramatically decreased by using CO2 as a co-feed with CH4. Due to the exothermic heat from the oxidation reaction of the oxygen carrier, the net heat duty of the novel chemical looping process was much lower than that of the dry reforming process. To validate the thermodynamic results, a Ni entrapped Fe2O3/Al2O3 oxygen carrier was synthesized by increasing the metal-support interaction through a sol-gel route. It is striking that the formation of Ni aluminate phase in the Ni-reinforced oxygen carrier facilitated dry reforming with partial oxidation while suppressing methane decomposition. By supplying a nonstoichiometric CH4-CO2 mixture feed (CO2/CH4 ratio = 0.38) to the 1 wt% Ni-entrapped Fe2O3/Al2O3 oxygen carrier at 900 °C, an H2/CO ratio of 2.09 and high CO selectivity of 96.76% were achieved with minimized carbon deposition. These results were close to the calculated equilibrium value while a Ni-impregnated Fe2O3/Al2O3 oxygen carrier showed an increased H2/CO ratio of 2.36 with severe carbon deposition by the promoted methane decomposition. In addition, the Ni-reinforced oxygen carrier also showed stable redox activity during successive reduction and oxidation cycles.