Ni-Fe and Co-Fe binary oxides derived from layered double hydroxides and their catalytic evaluation for hydrogen production

Binary oxides based on Co-Fe and Ni-Fe were synthesized thermal treatment of layered double hydroxides (LDH) having distinct Ni/Fe and Co/Ni ratios. The solids were characterized through X-ray diffraction (XRD), Raman and Mossbauer spectroscopy, nitrogen adsorption-desorption isotherms, thermoprogrammed reduction (TPR) and thermoprogrammed desorption of CO2 (TPD-CO2), scanning electron microscopy (SEM) and evaluated in dry reforming of methane. XRD results revealed the spinel oxides such as NiFe2O4 and CoFe2O4 coexisting with gamma-Fe2O3, alpha-Fe2O3, Co3O4 and NiO monoxides. These phases were confirmed by Raman and Mossbauer spectroscopy. Nitrogen adsorption-desorption isotherms showed a porosity within micro-to-meso pores range, with some samples displaying macropores. Catalytic evaluation in the dry reforming of methane by varying the temperature in the 650 and 750 degrees C range suggested in situ Co /CoFe2O4 and Ni /NiFe2O4 phases formation, which gives best results with the temperature increment, resulting in H-2/CO ratios close to 1. The elevated resistance to coking showed by Co-Fe series is particularly remarkable, however, sintering effects were observed over these solids. (C) 2014 Elsevier B.V. All rights reserved.