Effect of Additives on Ni-Based Catalysts for Hydrogen-Enriched Production from Steam Reforming of Biomass

The catalytic steam reforming of biomass for hydrogen production is investigated in a fixed-bed reactor. A suitable additive and precursor is found in various additives (cobalt, strontium, and lanthanum) and nickel salt precursors (nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate). Synthesized samples are characterized by X-ray diffraction (XRD), NH₃ temperature-programmed desorption (TPD), H₂ temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). Results show that Co and La doping of the Ni/Al₂O₃ catalyst improves the dispersion of surface-active particles and reduces the particle size, increasing H2 production. The hydrogen volume fraction of La-modified catalysts with 10% Ni is 38.96%, which is higher than 30.39% for the unmodified Ni/Al₂O₃ catalyst. The lowest hydrogen yield of Ni–Sr/Al₂O₃ catalyst is 19.22%. This low catalytic activity is due to the reaction of Ni–Sr/Al₂O₃ with SiO₂ found in biomass ash, which generates silicate without catalytic effect. The silicate melts and adheres to the catalyst surface at a high temperature, inhibiting the catalysis of nickel active sites. The maximum hydrogen yield obtained with nickel acetate as catalyst precursor is 51.41%, which is due to nickel acetate decomposing and forming more NiO in the amorphous state and improving the performance of catalyst.