High catalytic performance of an innovative Ni/magnesium slag catalyst for the syngas production and tar removal from biomass pyrolysis

The study aims to evaluate the catalytic potential of a Ni-based catalyst supported by magnesium slag (MS) for catalytic reforming of pyrolysis volatiles from pine sawdust. The catalysts were prepared by a wet impregnation method. The effects of different parameters (Ni loading content, calcination/catalytic bed temperature and steam to carbon (S/C) ratio) on the catalytic performance were investigated. In addition, tar cracking capability and coke deposition resistance of Ni/MS catalyst and Ni/γ-Al2O3 catalyst were explored under different calcination/catalytic bed temperatures. The catalysts were characterized by BET, XRD, SEM, TEM, TPO and Raman spectroscopy. The Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability. The best tar conversion (95.69%) and the highest hydrogen yield of 38.9 mmol/g biomass were obtained over Ni/MS catalyst under the conditions of Ni loading content = 3%, calcination/catalytic bed temperature = 800 °C, and S/C = 0.5. The interactions among Ni, Fe, Ca, and Mg formed multiple active centers (e.g., Ca2Fe2O5, (Ni, Mg) O solid solution and NiFe2O4) in the catalyst to show synergistic catalysis effects, thereby jointly improving catalyst activity and coke deposition resistance. Furthermore, both amorphous carbon and graphitic carbon were formed on the used catalysts and the D/G ratio (the relative intensity ratio between the D and G bands) was positively correlated with the catalytic activity.