Boosting hydrogen production by reducible oxygen species over Ni/MTixOy catalysts for the steam reforming of liquefied oil from Saccharina japonica

Abstract

Hydrogen is a sustainable energy resource. However, H2 is mainly produced by steam reforming of fossil fuels, emitting greenhouse gases. H2 production from macroalgae is a promising alternative to fossil fuels because of the carbon neutrality of the marine biomass. In this study, we investigated the steam reforming of liquefied oil derived from Saccharina japonica over metal titanate-based Ni catalysts (Ni/K2TixOy, Ni/CaTiO3, Ni/SrTiO3, and Ni/BaTiO3). CO temperature-programmed reduction (CO-TPR), and O2 temperature-programmed desorption (O2-TPD) characterizations showed that the reducibility of lattice oxygen on metal titanates depended on metal cation species and was much higher than on the inert Al2O3. SrTiO3 exhibited the highest reducible oxygen content among the metal titanates.Catalytic evaluations showed that Ni/MTixOy catalysts exhibited higher H2 selectivity and catalytic stability than Ni/Al2O3. Ni/Al2O3 exhibited an H2/CO ratio of 1.1, while other Ni/MTixOy catalysts exhibited higher values (2.3–4.4); especially, Ni/SrTiO3 showed the highest H2 selectivity (55.8%) and H2/CO ratio (4.4). The H2 selectivity could be correlated with the amount of reactive lattice oxygen, as quantified by CO-TPR and O2-TPD. Furthermore, reactive oxygen species inhibited coke deposition on Ni/MTixOy catalysts. Overall, the Ni/MTixOy catalysts exhibited a high potential for H2 production by the steam reforming of bio-oil from macroalgae.