Pyrolysis of biomass Tar model compound with various Ni-based catalysts: Influence of promoters characteristics on hydrogen-rich gas formation

This paper studied the conditions and mechanism of hydrogen-rich gas produced from catalytic pyrolysis of toluene by various Ni-based catalysts in a fixed-bed reactor. We specifically focused on the effect of different promoters and promoter characteristics on the physicochemical properties of Ni/HZSM-5 -based catalyst. The results revealed that, a similar initial activity for Ni-catalysts modified different promoters was tested with toluene conversion higher than 85%. The Fe-modified Ni/HZSM-5 catalyst has the most effective catalyst for hydrogen-rich gas production with the gaseous efficiency of 63.4 wt%, mainly gas (H2, CH4) yield of 118.6 mL/g-toluene, H2 yield of 53.4 mL/g-toluene at 800 °C pyrolysis for 40 min. The smaller crystal particles (3.1 nm), high surface area (219.5 m2/g), and sufficient loading quality (4 wt%) for Ni–Fe catalysts provided efficient active sites and promoted the pyrolysis process of toluene. The activity and stability of catalysts were also improved by Ce-modified Ni/ZSM-5 catalyst with the highest gaseous efficiency of 68.0 wt%, but the H2 yield of 40.3 mL/g-toluene was lower. However, Ni–Mg/HZSM-5 catalyst has lowest activity and stability. The catalyst deactivation is associated with nickel sintering and coke formation. After the Ni–Fe/HZ5 catalyst was regenerated twice, it still maintained high catalytic activity.