Study on the mechanism of syngas production from catalytic pyrolysis of biomass tar by Ni–Fe catalyst in CO2 atmosphere

This study focused on the pyrolysis behavior of biomass tar (toluene as model compound) via Ni-Fe catalyst, and enhanced the generation of syngas in the CO2 atmosphere. The whole reaction was carried out in a two-stage fixed-bed reactor. The evolution and yield of H2, CO, total syngas, and carbon deposition were investigated by Fe loading, catalyst dosage, pyrolysis temperature, and CO2 flow rate. The results showed the catalytic pyrolysis process of toluene obtained a gas yield of 323.3 mL/g-toluene, H2 yield of 181.7 mL/g-toluene, and carbon deposition of 794.3 mg/g-catalyst with Ni-4 %Fe/HZSM-5 catalyst dosage of 16 % at 900 ℃ for 40 min. Specifically, the catalytic pyrolysis process of toluene produced 27.43 % higher total syngas, 23.52 % higher H2, 66.0 % lower carbon deposition, and 391.67 % higher CO (19.07 mL/g-toluene) in the CO2 atmosphere with 40 mL/min. Approximately 4.43 g (21.22 mL) of CO2 was consumed by pyrolysis of 1 g toluene to generate the total syngas. This provides a theoretical basis for the synergistic pyrolysis of biomass tar and CO2 in the pyrolysis/gasification process of biomass, expounds the synergistic effect of Ni–Fe/HZSM-5 catalyst and CO2, reduces greenhouse gas emissions, and realizes the recycling of resources.