The performance and stability of different Ni supported catalysts have been studied in a continuous bench scale plant fitted with a conical spouted bed reactor for biomass pyrolysis at 500 degrees C and a fluidized bed reactor for the in line catalytic steam reforming of pyrolysis volatiles at 600 degrees C. The metal oxides selected as Ni supports have been Al2O3, SiO2, MgO, TiO2 and ZrO2, and all the catalysts have been prepared by the wet impregnation method. Significant differences have been observed in the performance and stability of the catalysts, with the most suitable ones concerning the evolution of bio-oil oxygenate conversion and H-2 yield with time on stream being as follows: Ni/Al2O3 > Ni/ZrO2 > Ni/MgO > Ni/TiO2 > Ni/SiO2. The activity and stability are explained based on the properties of the catalysts, which have been measured prior and after their use, by means of different techniques: N-2 adsorption/desorption, X-ray fluorescence (XRF), X-ray powder diffraction (XRD), temperature programmed oxidation (TPO), in-line monitoring by Fourier-transform infrared spectroscopy temperature programmed oxidation (FTIR-TPO), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).