Catalytic pyrolysis of biomass with Ni/Fe-CaO-based catalysts for hydrogen-rich gas: DFT and experimental study

The H₂-rich gas produced by biomass pyrolysis with Ni-based catalysts were studied by DFT, thermodynamic simulation, and pyrolysis experiment. The complex reaction between volatiles of biomass pyrolysis was clarified through DFT calculation. The results proved that the E_a of key reactions for H₂ production on Ni-Fe/CaO surface were lower than that on NC, which facilitates to produce H₂. The order of the E_a of the rate determining step on Ni-Fe/CaO surface is toluene cracking reaction < water-carbon reaction < Boudouard reaction < methane steam reforming reaction < methane dry reforming reaction < water gas shift reaction, indicating water gas shift reaction is the key control reaction. When the temperature is 650 ℃, Ni-Fe/CaO can effectively adsorb CO₂ to break the thermodynamic equilibrium of the water gas shift reaction and promote the forward reaction to generate H₂. Thermodynamic simulation and pyrolysis experiments determined that 650℃ and Ni-Fe/CaO are the most suitable reaction condition for H₂ formation. Under this condition, the liquid yield of biomass pyrolysis decreased by 18.32% and the gas yield was increased by 26.27% compared to that of Ni /CaO. More importantly, the H₂ yield was increased by 18.29% to 453.34 mL/g-biomass.