A comparative study of the GSR performance for Ni/CaO-MgO-Al2O3 and Ni/Al2O3 catalysts is reported. Catalysts were synthesized applying the wet impregnation method at a constant metal loading (8 wt %). Synthesized samples were characterized by N-2 adsorption/desorption, ICP, BET, XRD, NH3-TPD, CO2-TPD, H-2-TPR, XPS, TEM, STEM-HAADF and EDS. The carbon deposited on their surface under reaction conditions was characterized by TPO, Raman and TEM. It was proven that the use of CaO-MgO as alumina modifiers leads to smaller nickel species crystallite size, increased basicity and surface amount of Ni-0 phase. Thus, it increases the conversion to gaseous products favoring H-2 and CO2 production to the detriment of CO formation, by enhancing the water gas-shift (WGS) reaction. No liquid products were produced by the Ni/modAl catalyst over 550 degrees C, whereas time on stream results confirmed that deactivation can be prevented, as apart from decreasing the amount of coke deposition the nature of carbon was altered towards less graphitic and more defective structures. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.