The large scale production of biodiesel has increased interest in glycerol transformation into higher value products. This study evaluated catalysts supported on HZSM-5 containing Fe, Mo, and Nb, in the glycerol conversion to olefins. The samples were prepared by wet impregnation and characterized by XRD, SBET. NH3-TPD, and TPO techniques. Catalytic experiments were performed in the range of 450-600 degrees C in a fixed-bed tubular reactor. The gaseous products were analyzed by online gas chromatography. It was observed that the modification in the acidic properties of ZSM-5 plays an important role in the selectivity to olefins. The highest selectivity for olefins was obtained for the Fe/ZSM-5 catalyst in the 450-500 degrees C range and for Nb/ZSM-5 in the range of 550-600 degrees C. Fe/ZSM-5 presented the highest selectivity to propylene at lower temperatures due to the higher acidic strength of the strong acid sites. (C) 2019 Elsevier Ltd. All rights reserved.