Catalytic features of Ni supported on CeO2–ZrO2 solid solution in the steam reforming of glycerol for syngas production

Abstract

Catalysts containing 5 wt% Ni supported on Ce_xZr_1−xO₂ solid solutions prepared by the Pechini method were tested in steam reforming of glycerol (SRG) reactions. The catalysts were characterized by temperature programmed reduction with H₂ (H₂-TPR), XANES with H₂-TPR, X-ray diffraction (XRD) for fresh and used catalysts, XRD in situ for reduced catalysts, N₂-physisorption, oxygen storage capacity (OSC), and scanning electron microscopy (SEM). H₂-TPR analysis revealed various degrees of interaction between the NiO phase and the supports, which were confirmed by XANES analysis. XANES data also showed greater reduction of mixed supports, than of pure supports, showing that the presence of Zr⁴⁺ promotes CeO₂–ZrO₂ reduction. XRD confirmed the formation of CeO₂–ZrO₂ solid solutions, with cubic and tetragonal crystal structures, depending on the composition. N₂ physisorption analysis showed a greater surface area on the CeO₂–ZrO₂ solid solution supports than on the pure supports and this increase may be related to the insertion of ZrO₂ in the CeO₂ lattice. The SRG reaction was performed at 973 K with molar feed ratios of H₂O–glycerol = 3 : 1. All catalysts exhibited catalytic activity for the reaction, but carbon formation was high on the catalysts supported on pure oxide. The 5% Ni50CZ catalyst was the most selective for syngas production in the SRG. In addition to the nickel activity, the experiments revealed the activity of the supports in oxidation reactions, which was assigned to the formation of oxygen vacancies by the interaction of CeO₂ with ZrO₂.