Characterization of the structure features of CeZrO₂ and Ni/CeZrO₂ catalysts for tar gasification with steam

Purpose: The aim of this study was to find out how CeZrO₂ and Ni/CeZrO₂ structures change after the steam reforming of toluene. Design/methodology/approach: Nickel oxide supported on CeZrO₂ (Ni/CeZrO₂) with nickel loading of 10 wt. % was prepared by incipient wetness impregnation using an aqueous solution of nickel nitrate. Structure, morphology and chemical composition changes after the steam reforming of toluene were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and by X-ray diffraction (XRD) measurements. Additionally, spent Ni/CeZrO₂ was regenerated in O₂ while the fresh Ni/CeZrO₂ was subjected to two kinds of reduction: (i) in hydrogen, in order to reduce NiO to Ni and (ii) in toluene, in order to find if the reduction of NiO to Ni by C₇H₈ is followed by carbon deposition on metallic nickel. Findings: XRD results revealed the formation of a CeO₂-ZrO₂ solid solution with a cubic symmetry. Ni/CeZrO₂ preparation results in the increase of crystallites in comparison to the size of the commercial CeZrO₂. Reduction from NiO (200) to Ni (111) in samples reduced under hydrogen and toluene was confirmed while morphology of Ni/CeZrO₂ remained unchanged. Ni/CeZrO₂ reduced under toluene include large amount of carbon, deposited by decomposition of the hydrocarbon. Steam reforming of toluene not influence on morphology of investigated materials. Energy dispersive spectroscopy indicated larger amount of carbon residuals in sample after test in comparison to fresh Ni/CeZrO₂. After regeneration in O₂ carbon residuals were successfully removed. Practical implications: Nickel catalysts supported on ceria-zirconia can be efficiently applied in reforming reactions. Originality/value: CeZrO₂ and Ni/CeZrO₂ was selected as a model compound of tar from biomass gasification.