The effect of Ni catalysts promoted with Mg on catalytic activity and carbon deposition was investigated in acetic acid steam reforming. Acetic acid was chosen as representative compound for the steam reforming of bio-oil derived from biomass pyrolysis. In this study, nickel catalysts modified with Mg have been prepared by sequential impregnation method with 15 wt.% Ni and variable loadings of Mg (1-10 wt.%). The samples were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), high resolution transmission electron microscopy (HRTEM), specific surface area (BET) and temperature programmed reduction (TPR-H-2). Steam reforming of acetic acid was conducted in a fixed bed reactor at a temperature of 500 degrees C and 600 degrees C. Under reactive conditions, the 15Ni5Mg/Al catalyst proved to be superior to the other catalysts at 600 degrees C at which it presented an effluent gaseous mixture with the highest H-2 selectivity and reasonable low coke formation. (C) 2014 Elsevier B.V. All rights reserved.