Investigation of product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Iron-Nickel/ZSM-5 catalyst

• Fe-Ni/ZSM-5 exhibited an additive effect on aromatics selectivity. • Kinetic triplets of non-catalytic and catalytic pyrolysis of biomass were determined. • The activation energy was reduced in biomass catalytic pyrolysis over Fe-Ni/ZSM-5. • The reaction mechanism model of poplar sawdust catalytic pyrolysis was proposed. Py-GC/MS and thermogravimetric analysis were carried out to systematically explore product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Fe-Ni/ZSM-5. The results showed that the Fe-Ni/ZSM-5 exhibited an additive effect on the production of monocyclic aromatic hydrocarbons compared to mono-metallic catalysts (Fe/ZSM-5 or Ni/ZSM-5). Fe-Ni/ZSM-5 further increased the yield of toluene (17.28 mg g −1 ), which was 41.4% and 80.9% higher than Fe/ZSM-5 and Ni/ZSM-5, respectively. According to the kinetic analysis, the average activation energy obtained from catalytic pyrolysis with Fe-Ni/ZSM-5 using the methods of Friedman, Starink, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose was 156.19, 152.39, 154.30, and 152.11 kJ mol −1 , respectively. Fe-Ni/ZSM-5 addition lowered the activation energy compared to non-catalytic pyrolysis at the conversion rate of 0.15–0.75. The overall catalytic pyrolysis process of poplar sawdust follows the diffusion and nucleation models. The thermodynamic parameters (enthalpy and entropy) showed positive and negative values, respectively, indicating non-spontaneous reactions during the catalytic pyrolysis process.