Flame spray pyrolysis synthesized Ni-doped Fe/Ce oxygen carriers for chemical looping dry reforming of methane

Abstract

The current study investigates a nano-Fe/Ce oxygen carriers (OCs) doped with Ni synthesized by flame spray pyrolysis (FSP) method for the chemical looping dry reforming of methane (CL-DRM). The thermodynamic analysis and reaction simulation of the CL-DRM process with iron-based oxygen carriers are first carried out. The result shows that when reacting with CH4, Fe2O3 is reduced to Fe3O4 at first, accompanied by generation of H2O and CO2, and then to Fe with H2 and CO production. Fe can be oxidized to Fe3O4 and FeO by CO2. Subsequently, based on the reaction patterns obtained from the aforementioned analysis, CL-DRM experiment using Ni-doped Fe/Ce oxygen carriers is conducted in a fixed-bed reactor, and the effects of different Ni doping and reaction conditions on the performance of the oxygen carriers are investigated. The OC with a Ni/Fe molar ratio of 2/98 (2NiFe) achieves over 30% CH4 conversion and 90% CO selectivity in the partial oxidation step and stable cyclic performance. The FSP process facilitates high dispersion of Ni and formation of NiCe and NiFe alloys, which are stable active sites. Moreover, the transformation of Fe oxides and CeO2 into CeFeO3 on the surface of the OC has enhanced lattice oxygen availability and further improved cyclic stability.