Hydrogen Production via Glycerol Steam Reforming over Ni/Al₂O₃: Influence of Nickel Precursors

Abstract

This paper describes an investigation regarding the influence of Ni precursors on catalytic performances of Ni/Al2O3 catalysts in glycerol steam reforming. A series of Ni/Al2O3 is synthesized using four different precursors, nickel nitrate, nickel chloride, nickel acetate, and nickel acetylacetonate. Characterization results based on N2 adsorption–desorption, X-ray diffraction, H2 temperature-programmed reduction, H2 chemisorption, transmission electron microscopy, and thermogravimetric analysis show that reduction degrees of nickel, nickel dispersion, and particle sizes of Ni/Al2O3 catalysts are closely dependent on the anion size and nature of the nickel precursors. Ni/Al2O3 prepared by nickel acetate possesses the moderate Ni reduction degree, high Ni dispersion, and small nickel particle size, which possesses the highest H2 yield. Reaction parameters are also examined, and 550 °C and a steam-to-carbon ratio of 3 are optimized. Moreover, coke deposition, mainly graphite species, leads to the deactivation of Ni/Al2O3 catalysts in glycerol steam reforming. Nickel chloride-derived Ni/Al2O3 catalysts suffer from severe coke deposition and low reaction activity due to large Ni particle size, low Ni dispersion, and residual chloride.