Hydrogen production from acetic acid decomposition as bio-oil model molecule over supported metal catalysts

Abstract

Acetic acid decomposition to produce hydrogen was studied over Pd/Al2O3, Pt/Al2O3, Ni/Al2O3, and Co/Al2O3 catalysts. Pd/Al2O3 and Pt/Al2O3 systems exhibited high levels of conversion and hydrogen selectivity, with Pt/Al2O3 showing a hydrogen selectivity of 51.3% at 973 K. This behavior was influenced by the high dispersion and small particle size of Pt as well as the dissociative adsorption of acetic acid (acetate species) as exhibited by Pt/Al2O3 and Pd/Al2O3 systems. Additionally, Ni/Al2O3 and Co/Al2O3 were less active and presented low selectivity to hydrogen. These catalysts exhibited low dissociation of acetic acid on their surfaces, therefore hindering acetic acid transformation and hydrogen generation. However, when Ni/Al2O3 and Co/Al2O3 were reduced at 973 K, the conversion of acetic acid and hydrogen formation increased favorably. Co/Al2O3 showed less deactivation during time on stream. Deposited carbon on catalysts corresponded to the formation of carbon filaments for Pd/Al2O3 and Co/Al2O3 and of carbon nanotubes in the case of Ni/Al2O3.