Ni- and Fe-doped γ-Al2O3 or Olivine as primary catalyst for toluene reforming

In this paper, γ-Al2O3 supports prepared by a new aqueous sol-gel synthesis were doped with 2 wt. % of Ni or 10 wt. % of Fe and used as primary catalysts for the bio-syngas purification. Raw olivine, Ni- and Fe-doped olivine catalysts were also prepared for comparison with alumina-based samples. The physico-chemical properties of the samples were characterized by X-ray diffraction, nitrogen adsorption-desorption and temperature programmed reduction. Results showed that alumina-based samples were more porous than olivine-based ones. Stronger interactions of the dopants with the support were highlighted in the case of alumina samples. The catalysts were then tested at two temperatures, 750 and 850 °C, for the toluene reforming. Toluene was chosen as biomass gasification tar model molecule. At 750 °C, the Ni/olivine sample showed a higher toluene conversion and a lower benzene selectivity than the Ni/alumina sample. This lower catalytic activity was attributed to strong interactions between nickel and alumina (formation of a spinel NiAl2O4). At 850 °C, similar performances were obtained both for olivine and for alumina supports. However, due to lower interactions with the support and a better reduction of Ni, the methane conversion of the Ni/olivine sample was higher than that of the Ni/alumina sample.